Zanamivir, Relenza…For the prevention and treatment of influenza A and B.

Uncategorized 1 Response »

Feb 022014

Zanamivir

139110-80-8

APPROVED 26-7-96……. GSK NDA 021036

A guanido-neuraminic acid that is used to inhibit neuraminidase.

Zanamivir INN /z ə ˈ n æ m ɨ v ɪər / is a neuraminidase inhibitor used in the treatment and prophylaxis of influenza caused by influenza A virus andinfluenza B virus. Zanamivir was the first neuraminidase inhibitor commercially developed. It is currently marketed by GlaxoSmithKline under the trade name Relenza as a powder for oral inhalation.

The drug is approved for use for the prevention and treatment of influenza in those over the age of 7 in the United States, Canada, European Union, and many other countries. It is not recommended for people with respiratory problems and ailments.

United States	6294572	APPROVED 1994-12-15	EXPIRY 2014-12-15
United States	5360817	1993-07-26	2013-07-26
Canada	2291994	2003-10-14	2011-04-24
Canada	2081356	2000-02-22	2011-04-24

Patent No	PatentExpiry	use code
5360817	Jul 26, 2013
5648379	Jul 15, 2014	U-274
5648379	Jul 15, 2014	U-721
5648379	Jul 15, 2014	U-722
6294572	Dec 15, 2014

Zanamivir was discovered in 1989 by scientists led by Peter Malcolm Colman and Joseph Varghese at the CSIRO, in collaboration with theVictorian College of Pharmacy, Monash University, and scientists at Glaxo, UK. Zanamivir was the first of the neuraminidase inhibitors. The discovery was initially funded by the Australian biotechnology company Biota and was part of Biota’s ongoing program to develop antiviral agents throughrational drug design. Its strategy relied on the availability of the structure of influenza neuraminidase, by X-ray crystallography. It was also known, as far back as 1974, that 2-deoxy-2,3-didehydro-N-acetylneuraminic acid (DANA), a sialic acid analogue, is an inhibitor of neuraminidase. Sialic acid (N-acetyl neuraminic acid, NANA), the substrate of neuraminidase, is itself a mild inhibitor of the enzyme, but the dehydrated derivative DANA, a transition-state analogue, is a better inhibitor.

Computational chemistry techniques were used to probe the active site of the enzyme, in an attempt to design derivatives of DANA that would bind tightly to the amino acid residues of the catalytic site, and so would be potent and specific inhibitors of the enzyme. The GRID software by Molecular Discovery was used to determine energetically favourable interactions between various functional groups and residues in the catalytic site canyon. This investigation showed that there is a negatively charged zone in the neuraminidase active site that aligns with the C₄hydroxyl group of DANA. This hydroxyl is, therefore, replaced with a positively charged amino group; the 4-amino DANA was shown to be 100 times better as an inhibitor than DANA, owing to the formation of a salt bridge with a conserved glutamic acid (119) in the active site. It was also noticed that Glu 119 is at the bottom of a conserved pocket in the active site, just big enough to accommodate a more basic functional positively charged group, such as a guanidino group, which was also larger than the amino group. Zanamivir, a transition-state analogue inhibitor of neuraminidase, was the result.

As Biota was a small company, it did not have the resources to bring zanamivir to market by itself. In 1990, zanamivir patent rights were licensed to Glaxo, now GlaxoSmithKline (GSK). In 1999, the product was approved for marketing in the US and subsequently has been registered by GSK in a total of 70 countries (GlaxoSmithKline News release, 2006). Zanamivir is delivered via Glaxo’s proprietary Diskhaler inhalation device. The license agreement entitled Biota to receive a 7% royalty on Glaxo’s sales of zanamivir.

Chemical name:	5- Acetamido- 2, 6- anhydro- 3, 4, 5- trideoxy- 4- guanidino- D- glycero- D- galacto- non- 2- enonic acid
Synonyms:	Zanamivir, GG167, 4-guanidino-Neu5Ac2en and 2,3- Didehydro- 2, 4- dideoxy- 4- guanidino- N- acetyl- D- neuraminic acid(2R,3R,4S)-4-guanidino-3-(prop-1-en-2-ylamino)-2-((1R,2R)-1,2,3-trihydroxypropyl)-3,4-dihydro-2H-pyran-6-carboxylic acid
Empirical formula:	C₁₂H₂₀N₄O₇
Structural formula:
Molecular weight:	332.31g
Beilstein number:	7083099
Normal State:	Powder
Colour:	White to ‘off white’
Melting point:	325^oC
Optical rotary power:	Type [�]Conc: 0.9g/100mlSolvent: H₂OOptical rotary power: 41 degWavelength: 589nmTemp: 20^oC
CAS number:	139110-80-8
Solubility:	18mg/mL in water at 20^oC

Zanamivir is used for the treatment of infections caused by influenza A virus and influenza B virus. There is low to moderate evidence that it decreases the risk of one’s getting influenza by 1% to 12% in those exposed. In otherwise-healthy individuals, benefits overall appear to be small.It is unclear whether it affects the risk of one’s need to be hospitalized or the risk of death. An independent analysis of its effects by the Cochrane collaboration was awaiting release of trial data as of 2012. The evidence for a benefit in preventing influenza is weak in children with concerns of publication bias in the literature. As of 2009 no influenza has shown any signs of resistance. Since then genes expressing resistance to were found in patients infected with Influenza A H7N9 and who were treated with corticosteroids.

ZANAMIVIR

Mass

¹H NMR

Hydrogen	Chemical shift /ppm
(1H, d, 3-H)	5.53
(2H, 2dd, 4- and 6-H)	4.50 – 4.38
(1H, dd, 5-H)	4.21
(2H, dd+ddd, 9-Ha and 8-H)	4.00-3.88
(2H, 2dd, 9-Hb and 7-H)	3.70-3.62
(3H, s, Ac)	2.05

¹³C NMR

Carbon	Shift /ppm
(C=O, Ac)	177.3
(C-1)	172.1
(guanidino)	159.9
(C-2)	152.1
(C-3)	106.8
(C-6)	78.3
(C-8)	72.6
(C-7)	71.0
(C-9)	65.9
(C-4)	54.0
(C-5)	50.6
(Me)	24.8

ref 12

IR spectra:

The following peaks are present in the IR spectra of Relenza: 3332cm^-1, 1676cm^-1, 1600cm^-1, 1560cm^-1, 1394cm^-1, 1322cm^-1 and 1281cm^-1.

UV spectra

The maximum peak is 235nm giving E = 199 dm^-3 mol^-1cm^-1

ref 13for above

Although zanamivir was the first neuraminidase inhibitor to the market, it had only a few months lead over the second entrant, oseltamivir (Tamiflu), with an oral tablet formulation.

According to the CDC, Tamiflu, zanamivir’s main competitor, is not as effective at treating the influenza viruses as zanamivir, especially in H1N1 seasonal flu. In fact, tests showed 99.6% of the tested strains of seasonal H1N1 flu and 0.5% of 2009 pandemic flu were resistant to Tamiflu, while no flu samples, seasonal or pandemic, showed any resistance to zanamivir.

When first marketed in the US in 1999/2000, zanamivir captured only 25% of the influenza antiviral market, despite a huge promotional campaign. By the end of that season, Tamiflu was outselling zanamivir 3:1. During that season, zanamivir experienced worldwide safety warnings involving the risk of bronchospasm and death. Glaxo then reduced the marketing of zanamivir, and Tamiflu’s dominance increased. More than US$20 million worth of zanamivir sold by Glaxo in the first US season was returned to the company in the next two seasons because zanamivir’s sales to patients were far less than expected.

Biota commenced legal proceedings in 2004 alleging Glaxo’s reduced marketing of zanamivir to be a breach of contract. Biota claimed approximately A$700m from Glaxo. After Biota spent four years trying to progress its case, and incurring A$50m in legal costs, the company abandoned the claim in July 2008, recovering only A$20 million, including legal costs following settlement at mediation. Biota had refused an earlier tactical offer from Glaxo of A$75 million plus legal costs.

In August 2006, Germany announced it would buy 1.7 million doses of zanamivir, as part of its preparation strategy against bird flu. “Germany’s purchase shows that countries are starting to take a balanced view of influenza preparedness,” says Simon Tucker, head of research at Melbourne-based Biota, where zanamivir was originally developed.

In April 2009, many cases of swine flu (H1N1-type virus) were reported in US and Mexico. Zanamivir is one of only two drugs prescribed to treat it. A study published in June 2009 emphasized the urgent need for augmentation of oseltamivir (Tamiflu) stockpiles, with additional antiviral drugs including zanamivir, based on an evaluation of the performance of these drugs in the scenario that the 2009 H1N1 swine flu neuraminidase (NA) were to acquire the Tamiflu-resistance (His274Tyr) mutation, which is currently widespread in 99.6% of all tested seasonal H1N1 strains.n January 2011, GSK announced that it would commence phase III trials for intravenous zanamivir in a study that will span 20 countries in the Northern and Southern Hemispheres.

Recently, the reported oseltamivir-resistance H5N1 virus neuraminidase still retaining susceptibility to zanamivir indicates that the structure of zanamivir has some advantages over oseltamivir in binding to the active pocket of H5N1 neuraminidase.

As a proven anti-influenza drug target, neuraminidase continues to be attractive for the development of new inhibitors. The crystal structure of H5N1 avian influenza neuraminidase (PDB code: 2HTY) provides the three-dimensional structural information and opportunity for finding new inhibitors in this regard, because the existing inhibitors, such as oseltamivir and zanamivir, were developed based on different structures of neuraminidase, such as subtypes N9 and N2, and type B genus of influenza virus.

ZANAMIVIR

Chemistry

Scheigetz, J.; Zamboni, R.; Bernstein, M. A.;Roy, B. (December 1995). “A syntheses of 4-a-guanidino-2-deoxy-2,3-didehydro n-acetylneuraminic acid”. Organic Letters 27 (6): 637–644.doi:10.1021/ol901511x. Retrieved 2010-11-14.

Zanamivir synthetic process in the world

Together with oseltamivir, zanamivir is the only medicine which can prevent influenza on humans caused by H5N1 and H1N1 virus. Vietnam prepared oseltamivir (Tamiflu) medicine. But there was no zanamivir – the first influenza medicine belonging N1 kind, discovered and commercialized before oseltamivir. The scientific name of zanamivir is acid 5-acetamido-4-guanidino-6-(1,2,3-trihydroxy-propyl)-5,6-dihydro-4H-pyran-2-carboxylic. The discovery of zanamivir opens research possibilities for new medicines which have the same effect on enzyme neuraminidase inhibitor to prevent and treat influenza.

Acid sialic is an input to synthetize zanamivir. The name acid sialic (Neu5Ac2en) is used to indicate derivation at O- and N- positions of acid neuraminic, just for acid N-axetylneuraminic. Acid sialic of carbohydrate groups is on animal cells and microorganism, especially in glycoprotein and gangliosid. The commercial acid sialic is extracted from whey of the cheese and milk process as well as egg yolk, and costs about 5,000 USD per kilo.

In 1994, zanamivir was first synthesized and made public by Von Itzstein and other scientists from the Department of Pharmaceutical Chemistry under Monash University (Australia). Then, Chandler and co-workers of Glaxo company (GSK, Britain) acquired results, improved reaction steps and made them public in 1995. Accordingly, this method produced 8.3% of general output. The synthetic process is described in Figure 1.

Figure 1: Zanamivir synthetic process according to Chandler

Up to now, the research of Chandler has been the only publication about zanamivir synthetic method, the output of which is greater than milligrams, and it reproduces details about reaction conditions and physiochemical properties of the requisite substances.

Recently, a research group of Yao (China) proposed a new approach to synthetize into intermediate compound 5. Researchers started from another material – D-glucono-δ-lactone, which is cheaper than acid sialic. However, the synthetic process is longer and much complicated, including 24 steps, with lower productivity (0.2%).

Researching on synthesizing Zanamivir from Acid sialic by Institute of Chemistry

Synthetizing methyl N-acetylneuraminate (2) and O-pentaacetoxy (3) from acid sialic

Scientists from the Institute of Chemistry used acid sialic (axit N-acetylneuraminic) 98% from China as the input for the zanamivir synthetic process. They decided to use the method of Warner, using ion exchange resin Dowex-H, with the role of catalyst. Reaction was performed in the room in 10 hours. The output was metyl (2) este product of acid N-acetylneuraminic with a productivity of 99%.

Then, to synthetize O-pentaacetoxy (3), scientists applied axetyl effective chemistry method recently published, using BF₃.OEt₂catalysis at 0⁰C. Productivity in this case exceeded 95%.

Figure 2: The diagram of O-pentaacetoxy 3 derivative making

The use of catalysts which were ion exchange resin Dowex-H (for este chemical reaction) and BF₃.OEt₂ (for axetyl chemical reaction) had more advantages than the method by scientists from Glaxo.

Synthesizing intermediate compound – oxazoline (4) key from O-pentaacetoxy (3)

Figure 3: Diagram to synthesize oxazoline (4) from O-pentaacetoxy (3) according to a and b methods

Firstly, scientists conducted a survey on oxazoline (4) synthetic process according to Chandler’s process. O-pentaacetoxy (3) compound was separated from two types of OAc and formed oxazoline round thanks to the effect of strong acid Lewis, which was TMSOTf at 52⁰C in 2.5 hour. The productivity of this reaction achieved 40%. The pilot instead of TMSOTf by BF3.OEt2 catalysis in dichloromethane at room temperature at night, the productivity of the reaction to form oxazoline round from penta-acetoxy (5) was similar to the method using TMSOTf (42%). To increase productivity, scientists made a survey on one-pot method, directly from metyl este (2) to oxazoline (4), without passing O-pentaacetoxy (3), gave the highest productivity (73,3%) and was the most economic effectiveness.

Synthesizing zanamivir from oxazoline (4) intermediate compound

The next, scientists successfully conducted reactions from oxazoline (4) intermediate compound to Zanamivir (9) final product (Figure 1). Zanamivir product had IR and NMR data which were compatible with their structure.

Therefore, scientists from the Institute of Chemistry under Vietnam Academy of Science and Technology built a stable process, including seven major steps, synthesizing from acid sialic with the general productivity of 6.6% (the productivity made public in the world was 8.3%). Especially, in the first period, from acid sialic to oxazolin (4) was optimized and gave a general productivity of 74%, higher than the productivity made public by (61.7%). However, the productivity gained in the later period is still low. Now, synthesizing zanamivir influenza medicine still continues to be researched.

……………………

Beau and coworkers assembled the core dihydropyran framework of zanamivir congeners via a combination of PBM reaction and Iron(III)-promoted deprotection-cyclization sequence. A stereochemically-defined α-hydroxyaldehyde 2, diallylamine and a dimethylketal-protected boronic acid 1 is coupled to form the acyclic, stereochemically-defined amino-alcohol 3, which then undergoes an Iron(III)-promoted cyclization to form a bicyclic dihydropyran 4. Selective opening of the oxazoline portion of the dihydropyran intermediate 4 with water or timethylsilyl azide then furnish downstream products that have structures resembling the Zanamivir family members.

Reaction scheme part 1:

The commercially available N-acetyl-neuraminic acid 1 is the starting reagent for the most direct approach to the synthesis of 4-guanidino-Neu5Ac2en (Relenza). In reaction scheme 1 the steps for the conversion of N-acetyl-neuraminic acid 1 to its 4-amino analogue is shown. Step 1 is the addition of methanolic HCl (MeOH and HCl gas), which produces the methyl ester of 1, followed by acetic anhydride in pyridine with 4-(dimethylamino)pyridine catalysis, which produces the penta-acetoxy compound, 2. In step 2, 2 is converted into the oxazoline 3 at high yield using trimethylsilyl trifluoromethanesulfonate (TMSOTf) in ethyl acetate at 52^oC. In step 3, the azido compound, 4, is produced by the reaction of 3 with trimethylsilyl azide in tert-butyl alcohol at 80^oC. In step 4 catalytic sodium methoxide in methanol was used to remove the acetate protecting groups from 4 to give triol 5. The 4-amino analogue, 6 was made in step 5, by hydrolysis using triethylamine in water, hydrogenolysis with a Lindlar catalyst and finally the addition of Dowex 2 * 8 resin. The triethylamine salt of the 6 was made during hydrogenolysis and the purpose of the Dowex 2 * 8 resin was to desalt this intermediate. The chemical names of the compounds are:

1: N-acetyl-neuraminic acid

2: 5- Acetamido- 3,5- dideoxy- D- glycero- �- D- galacto- 2- nonulo- pyranosonic acid methyl ester

3: Methyl (3aR, 4R, 7aR)- 2- Methyl- 4- [(1’S, 2’R)- 1′, 2′, 3′ – triacet- oxypropyl]- 3a, 7a- dihydro- 4H- pyrano [3, 4-d] oxazole- 6- carboxlate.

4: 5- Acetamido- 7, 8, 9- tri- O- acetyl- 2, 6- anhydro- 4- azido- 3, 4, 5- trideoxy- D- glycero- D- galacto- non- 2- enonic acid methyl ester.

5: 5- Acetamido- 2, 6- anhydro- 4- azido- 3, 4, 5- trideoxy- D- glycero- D- galacto- non- 2- enonic acid methyl ester.

6: 5- Acetamido- 4- amino- 2, 6- anhydro- 3, 4, 5- trideoxy- D- glycero- D- galacto- non- 2- enonic acid.

Part one of reaction scheme

Synthesis of reactant necessary for part 2 of reaction:

Aminoiminomethane-sulfonic acid (AIMSA), 7, which is necessary for the conversion of compound 6 into Relenza, 9, is synthesised in Reaction scheme 2. The oxidizing solution necessary for the reaction is prepared by the addition of peracetic acid to 30% hydrogen peroxide and then conc. sulfuric acid. This is followed by acetic anhydride and, once the reaction has completed, methanol. Thiourea is dissolved in methanol and added slowly to the oxidizing solution.to produce compound 7. Note that any crystals that form are removed and that the reaction needs to be carried out under cooled conditions. See the reference source for more experimental details.

Synthesis of AIMSA

Reaction scheme part 2:

Reaction scheme 3 shows the conversion of compound 6 into Relenza For route A, 3 mol equivalent of AIMSA, 7, and 3 mol equivalent of potassium carbonate are added in a portionwise manner to compound 6 over an eight hour period. A yield of about 48% of the crystalline product 8 should be obtained for this method. An alternative route is to treat compound 6 with 1.1 mol equivalent of cyanogen bromide in the presence of sodium acetate in methanol. Route B step 1 gives compound 9, which can be converted into the final product 8 by treating it with ammonium hydroxide and ammonium formate at 85^oC. A 36% yield of the purified product can be obtained after purification with ion-exchange chromatography and crystallisation. The chemical names of the compounds in this scheme are:

8. 5- Acetamido- 2, 6- anhydro- 3, 4, 5- trideoxy- 4- guanidino- D- glycero- D- galacto- non- 2- enonic acid. (Relenza)

9. 5- Acetylamino- 2, 6- anhydro- 4- cyanoamino- 3, 4, 5- trideoxy- D- glycero- D- galacto- non- 2- enonic acid

Part 2 of reaction scheme

ref are 13 and 14

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

SYNTHESIS FROM PATENT EP2276479A2

ZANAMIVIR AND BOC PROTECTED ZANAMIVIR

The synthesis of zanamivir is shown in Scheme 1. The starting material used for zanamivir synthesis is sialic acid 1, which was converted to the methyl ester 2, in presence of Dowex H+ as described in detail in reference 104. The hydroxyl groups of 2 are protected with acetyl groups to give compound 3, which was then converted to the oxazoline derivative 4 in the presence of trimethyltrifluoromethanesulfonate as described in detail in reference 105. Azide 5 was synthesized from 4 in presence of azidotrimethylsilane as described in detail in reference 105. The azide is reduced to the corresponding amine 6 by using Lindlar’s catalyst, and the amine is in turn converted to the guanidine derivative 7 as described in detail in reference 106. The final step involves the deprotection of the methyl ester and acetyl groups in the presence of methanolic sodium hydroxide to give Boc-protected zanamivir 8 as described in detail in reference 106. 8, ¹H NMR (CD₃OD) δ (ppm) 5.6 (d, J = 2.0 Hz, IH), 5.01 (dd, J = 9.6, 2.1 Hz, IH), 4.25 (dd, J = 10.8, 1.1 Hz, IH), 4.18 (dd, J = 10.6, 9.6 Hz, IH), 3.89 (ddd, J = 9.4, 6.2, 2.7 Hz, IH), 3.84 (dd, J = 11.3, 2.8 Hz, IH), 3.67 (dd, J = 11.3, 5.8 Hz, IH), 3.57(d, J = 9.3 Hz, IH), 1.9 (s, 3H), 1.55 (s, 9H), 1.50 (s, 9H); ESI-MS: 533 (M+H)+.

Scheme 1

a) Dowex H Methanol b) Aceticanhydride DMAP pyridine c) trimethylsilyl tπfluorαmethane sulfonate ethylacetate d) azidotrimethylsilane butanol e) Lindlar’s catalyst ethanol f) N N’-bis-tert-butoxycarbonyMH-pyrazole-i carboxamidine tetrahydrofuran g) sodium hydroxide methanol

104. Martin, R., K.L. Witte, and C-H. Wong, The synthesis and enzymatic incorporation of sialic acid derivatives for use as tools to study the structure, activity, and inhibition of glycoproteins and other glycoconjugates. Bioorganic & Medicinal Chemistry, 1998. 6(8): p. 1283-1292.

105. Malcolm Chandler, M.J.B., Richard Conroy, Brian Lamount, Bina Patel, Vipulkumar K. Patel, Ian P. Steeples, Richard Storer, Naill G. Weir, Michael

Wrightm Christopher Williamson, Synthesis of the potent influenza neuraminidase inhibitor 4-guanidino Neu5Ac2en. X-Ray molecular structure of S-acetamido^-amino^^-anhydro-S^^-trideoxy-D-erythro-L-gluco- nononic acid. J. Chem. Soc, Perkin Trans. 1, 1995: p. 1173 – 1180.

106. Masuda, T., et al., Synthesis and anti-influenza evaluation of polyvalent sialidase inhibitors bearing 4-guanidino-Neu5Ac2en derivatives. Chem Pharm Bull (Tokyo), 2003. 51(12): p. 1386-98

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

The active component of RELENZA is zanamivir. The chemical name of zanamivir is 5- (acetylamino)-4-[(aminoiminomethyl)-amino]-2,6-anhydro-3,4,5-trideoxy-D-glycero-D-galacto non-2-enonic acid. It has a molecular formula of C₁₂H₂₀N₄O₇ and a molecular weight of 332.3. It has the following structural formula:

RELENZA<br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /> (zanamivir) Structural Formula Illustration

Zanamivir is a white to off-white powder for oral inhalation with a solubility of approximately 18 mg/mL in water at 20°C.

RELENZA is for administration to the respiratory tract by oral inhalation only. Each RELENZA ROTADISK contains 4 regularly spaced double-foil blisters with each blister containing a powder mixture of 5 mg of zanamivir and 20 mg of lactose (which contains milk proteins). The contents of each blister are inhaled using a specially designed breath-activated plastic device for inhaling powder called the DISKHALER. After a RELENZA ROTADISK is loaded into the DISKHALER, a blister that contains medication is pierced and the zanamivir is dispersed into the air stream created when the patient inhales through the mouthpiece. The amount of drug delivered to the respiratory tract will depend on patient factors such as inspiratory flow. Under standardized in vitro testing, RELENZA ROTADISK delivers 4 mg of zanamivir from the DISKHALER device when tested at a pressure drop of 3 kPa (corresponding to a flow rate of about 62 to 65 L/min) for 3 seconds.

CLIP

On Zanamivir

Total Synthesis of Anti-Influenza Agents Zanamivir and Zanaphosphor via Asymmetric Aza-Henry Reaction

Long-Zhi Lin^† and Jim-Min Fang^*^†^‡

^† Department of Chemistry, National Taiwan University, Taipei 106, Taiwan

^‡ The Genomics Research Center, Academia Sinica, Taipei 115, Taiwan

Org. Lett., 2016, 18 (17), pp 4400–4403

DOI: 10.1021/acs.orglett.6b02131, http://pubs.acs.org/doi/suppl/10.1021/acs.orglett.6b02131

*E-mail: jmfang@ntu.edu.tw.

The potent anti-influenza agents, zanamivir and its phosphonate congener, are synthesized by using a nitro group as the latent amino group at C4 for asymmetric aza-Henry reaction with a chiral sulfinylimine, which is derived from inexpensive d-glucono-δ-lactone to establish the essential nitrogen-containing substituent at C5. This method provides an efficient way to construct the densely substituted dihydropyran core of zanamivir and zanaphosphor without using the hazardous azide reagent.

Zanamivir as the TFA salt (40 mg, 90 %). C14H21F3N4O9; colorless solid, mp 260262 oC;
1H NMR (400 MHz, D2O) δ 5.67 (1 H, d, J = 2.1 Hz), 4.48 (1 H, dd, J = 9.3, 2.1 Hz), 4.41 (1H, d, J = 10.6 Hz), 4.26 (1 H, dd, J = 10.6, 9.3 Hz), 3.98–3.90 (2 H, m), 3.71–3.66 (2 H, m),2.06 (3 H, s);

13C NMR (100 MHz, D2O) δ 174.5, 166.4, 162.9 (CO2 of TFA, q, J = 35.4 Hz ),157.0, 146.2, 116.3 (CF3 of TFA, q, J = 290.2 Hz ), 107.2, 75.8, 69.8, 67.9, 62.9, 50.8, 47.6,21.9;

ESI–HRMS calcd for C12H20N4O7Na: 355.1230, found: m/z 355.1288 [M + Na]+.

Introduction

Relenza (Zanamivir for oral inhalation) is the first in a new generation of influenza virus-specific drugs known as neuraminidase inhibitors, which work by interferring with the life cycles of influenza viruses A and B. It prevents the virus spreading infection to other cells by blocking the neuraminidase enzyme present on the surface of the virus. Relenza is available as a powder that is administered by inhalation of 2 blisters from the rotadisk inside the diskhaler (Fig. 1) twice daily for five days. This means that 20mg of Relenza is delivered to the principal site of viral replication each day.The main method for preventing influenza since the 1960s is by vaccination and although this and anti-viral drugs such as amantadine and its analogue rimantadine have long been available (since 1976 and 1993 respectively), they are only of limited use because of the constant mutation of the virus. This chameleon-like nature also means that the virus can become unrecognizable to the human immune system and thus repeatedly infect millions of people year after year.

Fig 1: The diskhaler used to administer Relenza. Each blister in the Rotadisk contains 5mg of the drug

Why there is a need for a more effective influenza treatment: At present influenza is basically an uncontrolled disease and an effective method is needed for both the prevention and treatment of it. In the 20^th century there were some major pandemics such as the 1918-1919 Spanish ‘flu which killed 20 million people world wide, the 1957 Asian ‘flu, the 1968 Hong Kong ‘flu and the 1977 Russian ‘flu¹² These viruses also affect different animals, especially domesticated chickens and turkeys and in Hong Kong in 1997 a virulent bird flu virus, started infecting and killing people for the first time ever. Of the 18 people affected 6 died, although there was no evidence that the virus was able to spread between people. Given the antigenic properties of the influenza virus, in the future the virus may be passed from person to person, and because human immune systems are not prepared for avian viruses the effects on the population could be grave. It would not be possible to prepare vaccines in time and anti-viral drugs are not always adequate.

Advantages of Relenza over previous treatments:

Relenza has a number of advantages over the existing treatments for influenza. It does not cause significant side effects and the development of zanamivir-resistant viruses is not expected to occur readily in patients. This is because selection of drug-resistant mutants characterized by changes in neuraminidase requires prolonged passage in tissue culture and may be a biological cripple. If started within two days of the onset of influenza symptoms and if a fever is present, the duration of illness is decreased by an average of 1.5 days. It appears to decrease the severity of flu symptoms for the remainder of the illness, as well as decreasing the number of complications from the flu. It is also possible that Relenza could be used as a method of ‘flu prevention although it has not yet been approved for this use.

Comparison of the symptoms of the ‘flu with that of a common cold:

People infected by an influenza virus suffer a lot more than those with a cold. As you can see from the table below, some of the symptoms are similar, but with a cold they are less severe.Influenza also becomes more serious when it leads to secondary bacterial pneumonia or primary influenza viral pneumonia or when it exacerbates underlying medical conditions such as pulmonary or cardiac disease. In children, the symptoms are similar to those observed in adults, however children often have higher fevers and younger ones may develop gastrointestinal manifestations. It should be noted that Relenza is not effective on people with colds or other viral illnesses.

Influenza	Cold
Sore throat	Mild sore throat
High fever and chills	Low-grade fever
Non-productive cough	Cough
Severe muscle aches	Congestion
Headache
Intense fatigue.

The effect of Relenza on patients with respiratory diseases:Relenza is not generally recommended for the treatment of patients with respiratory dieseases such as asthma or chronic obstructive pulmonary disease (COPD) and has carried an approval since its approval in July 1999. Some patients with underlying airway diseases have experienced serious adverse events following treatment, with some fatal outcomes although causality has been difficult to establish. It has been recommended that patients with asthma have a fast-acting bronchodilator inhaler available and use it about 15 minutes before taking Relenza

Successfulness of Relenza:The sialidase inhibitory activities (determined by methods described in reference 7) of Relenza compared to the more recent neuraminidase inhibitor Oseltamivir are shown in the table below⁹.IC50 is the concentration that reduces enzyme activity by 50%.

Compound	Influenza A IC50 (�M)	Influenza B IC50 (�M)
Relenza	0.005	0.004
Oseltamivir	0.002	0.032

The results demonstrate that both compounds are good inhibitors of influenza A and B, with Oseltamivir being more selective towards Influenza A and Relenza showing a better overall performance. In phase I and II tests reported by the Lancet⁵, no important adverse effects were found in healthy patients or those reported to have mild to moderate asthma following an inhaled administration of 40mg/day of Relenza. There was a significant improvement of the symptoms of people taking Relenza compared to those taking the placebo.

1940s: Discovery that the influenza virus’s enzyme was destroying receptors on red blood cells^F.This was discovered by George Hirst, who noticed that when red blood cells were mixed with fluids from influenza infected chicken embryos in cold conditions the cells were very heavily agglutinated by the virus. These red cells dispersed when warmed up and could not be re-agglutinated in the cold with fresh virus. This led him to the conclusion that the influenza virus’s enzyme was destroying receptors on red blood cells.

The finding of sialidase (also known as neuraminidase):Alfred Gottschalk heard of Hirst’s experiment and interpretation of results, and this led him to believe that there was a “split product”. He discovered sialic or neuraminic acid (Fig 2), a type of sugar, and the enzyme on the virus was called neuraminidase (or sialidase). At this time it was thought that it was the neuraminidase which was responsible for the observations made by Hirst, but it was later shown by Robin Valentine, W. Graeme Laver, Norbert Bischofberger and Robert G. Webster that the hemagglutinin (receptor-binding) and neuraminidase (receptor-destroying) activities of the virus resided in two quite different spikes on the surface of the virus.

Fig 2: Sialic Acid

Discovery of how new pandemic strains of ‘flu A occured.

Ed Kilbourne, W. Graeme Laver, Norbert Bischofberger and Robert G. Webster realised that hybrid viruses could be formed by infecting cells simultaneously with two different Type A flu viruses. This was because the RNA pieces coding the various virus proteins reassorted, some of the viruses contained the hemagglutinin from one parent and the neuraminidase from the other. This “mating” of two parent viruses to give a hybrid virus explained how new pandemic strains of ‘flu A occurred, and led to a very good way of producing influenza viruses with any desired combination of hemagglutinin and neuraminidase spikes. This helped towards finding a way of producing pure neuraminidase which was later essential for crystal growth and drug design experiments.

The crystallization of neuraminidase:

Laver, Bischofberger and Webster isolated one type of influenza virus by sucking off the allantoic fluid surrounding the embryo of infected chicken eggs and purifying this. The virus particles were incubated with an enzyme capable of digesting proteins. This enzyme was selected to split the “heads” of the neuraminidase spikes off the virus particle without destroying them and to leave behind or destroy the hemagglutinin spike. The neuraminidase “heads” obtained were concentrated using high-speed centrifugation. The tiny pellet of neuraminidase heads examined had a crystalline appearance, and X-ray diffraction analysis of larger crystals showed that they were made of protein.

Neu5Ac2en (DANA) was shown to inhibit influenza neuraminidase:

Different variants of ‘flu neuraminidase were known to exist, each containing an amino acid sequence that varies between types of neuraminidase apart from one small sequence.It was seen that the conserved amino acids came together when the neuraminidase polypeptide folded up to form the active enzyme. This formed a well conserved cavity which was the active catalytic site of the neuraminidase enzyme. It became apparent that a plug-drug could be made to exactly fit into the active site and inhibit the neuraminidase activity from other influenza viruses. A synthetic analog of sialic acid called Neu5Ac2en (DANA) (Fig 3) was shown to inhibit the influenza virus neuraminidase, but not sufficiently enough to be used treatment for the ‘flu in humans.

Fig 3: Neu5Ac2en (DANA)

The plug drug.Mark von Itzstein and colleagues discovered that replacing the OH at the 4 position of sialic acid with a positively charged amino group made a better inhibitor than sialic acid or its analogue, DANA. Replacing the OH at the 4 position of sialic acid with a guanidino group led to a potent inhibitor of ‘flu neuraminidase. This compound was given the names GG167 and Zanamivir and is now more commonly known as Relenza. Peter Colman soaked the substrate for sialic acid in neuraminidase crystals and used X-ray crystallography to determine the three-dimensional structure of the crystals. The strong binding of Relenza by ‘flu neuraminidase which was seen is due to the positively charged guanidino group being anchored by the negatively charged glutamic acids. More details about this are provided in the immunology section.

Immunology


	Fig 4: The influenza viruses as seen under the electron microscope. Neuraminidase and haemagglutin spikes are visible.
Structure of the flu virus:Influenza (Fig 4) is an RNA virus which may exist as any shape from round balls to long, spaghetti-like filaments. The genome of this virus is associated with five different viral proteins and is surrounded by a lipid membrane, which means that influenza belongs to the “enveloped” group of viruses. Eight separate pieces of ribonucleic acid (RNA) make up the influenza virus genome and each piece of RNA specifies the amino acid sequence of one and sometimes two of the virus’s proteins. The segmented nature of the RNA allows differenet flu viruses to easily “mate” with each other to form hybrid progeny viruses with bits of RNA from each parent virus.Two glycoprotein molecules, known as hemagglutinin (HA) and neuraminidase (NA) (Fig 5) are stuck onto the lipid envelope of the virus and both play a crucial role in the infection of the epithelial cells of the upper respiratory tract. HA is a rod-shaped triangular molecule.and NA exists as a mushroom shaped spike with a box-like head on top of a long stalk, containing a hydrophobic region by which it is embedded in the viral membrane..


	Fig 5: The Neuraminidase enzyme
The enzyme Neuraminidase, also known as sialidase, is a tetramer with C-4 symmetry and an approximate molecular weight of 250 000. It contains a symmetrical folding pattern of six four-stranded antiparallel �-sheets arranged like propeller blades. Nine types of neuraminidase have been identified for influenza A and only one subtype for influenza B, and only 30% of the overall amino acid sequence is conserved between all known types of neuraminidase⁸ – these are the amino acids which line and surround the walls of the binding pocket. If they mutate, the enzyme is inactivated, so the virus could not mutate to escape from a drug which interfered with this site. So neuraminidase offers an attractive site for therapeutic intervention in influenza infections.

How the influenza virus works:The influenza virus (like all viruses) can only replicate after invading selected living cells and growing inside them. It makes thousands of new virus particles from the cellular machinery and then goes on to infect other cells.. Hemagglutinin allows the virus to infect the epithelial cells of the upper respiratory tract by attaching it to cells through receptors on the cell containing sialic acid, it fuses the cell membrane with the membrane of the virus, allowing the RNA of the virus to get inside the cell and thus instruct the cell to make thousands of new virus particles. After this viral replication, the progeny virions must be released from the cell to repeat the cell cycle of infection.Neuraminidase removes the sialic acid receptors from the host cell and other newly made virus particles by cleavage of -glycosidic bonds. This enables the virus to escape from the cell in which it grew and spread in the body to infect other cells. The action of NA may also facilitate viral mobility through the mucus of the respiratory tract. virusattack.gif (46720 bytes)

	Fig. 6: The life cycle of the influenza virus. Click once on this image to see a larger version
The life cycle of the influenza virus^G begins with the individual virus entering the cell lining of the respiratory tract (letter a in Fig. 6), and the cell being induced to take up the virus because hemagglutinin on the virus binds to the sialic acid (b and c in Fig 6). The virus then dispatches its genetic material (made up of RNA) and its internal proteins to the nucleus of the cell (e and f). Messenger RNA is produced when some of the internal proteins duplicate the RNA (f). This messenger RNA is used by the cell as a template for making viral proteins (g and h) and genes which become new viral particles and leave the cell covered in sialic acid. This sialic acid needs to be removed so that the hemagglutinin molecules on one particle don’t attach to the sialic acid on other ones, thus causing the new viruses to clump together and stick to the cell. The sialic acid is removed from the surface of the new viral particle by neuraminidase (j) and the new viral particles are able to travel and invade other cells (k).

How Relenza works:

Relenza adopts a position within the active site of the enzyme and copies the geometry of the sialoside hydrolysis transition state⁹. It can achieve very good binding through appropriate presentation of its four pendent substituents and contains a hydrogen bonding glycerol sidechain. The guanidino group in Relenza is believed to form salt bridges with Glu 119 in the neuraminidase active site and add a strong charge interaction with Glu 227⁸.

Two hydroxyl groups of the 6-glycerol side chain are hydrogen bonded to Glu276 and the 4-hydroxyl is oriented towards Glu119. The NH group of the 5-N acetyl side chain interacts with a bound water molecule on the floor of the active site. The carbonyl oxygen of the same side chain is hydrogen bonded to Arg152 and the methyl group enters a hydrophobic pocket lined by Ile222 and Trp178. The glycosidic oxygen projects into bulk solvent.


	Fig 7. Relenza bound to neuraminidase

The binding involved in Fig 7 is shown more clearly in Fig 8 below. Neuraminidase can no longer remove the sialic acid receptors from the host cell and newly made virus particles because of this binding. Therefore the virsuse ‘clump’ together or to the host cell and cannot go on to effect new cells.


	Fig 8: Depiction of interaction of Relenza (GG 167) in the neuraminidase binding site⁶

References

1): K. J. Lui and A. P. Kendal, Am. J. Public Health, 1987, 77, 712

2): Scheiget, Zambonis, Bernstein and Roy, Org. Prep. Proced. Int., 1995, 27, 637- 644

3): Glaxo Wellcome Inc. Relenza� (zanamivir for inhalation) [package insert]. Research Triangle Park, NC: Glaxo Wellcome, Inc., 1999

4): N Seppa, Scientific American, July 10th 1999, Volume 156

5): L. Gubareva, Lancet, March 4th 2000, 355: 827-35

6): J. Medicinal Chemistry. 1999, 42, 2332-2343

7):P Smith, S Sollis, P Howes, P Cherry, I Starkey, K Cobley, H Weston, J Scicinski, A Merritt, A Whittington, P Wyatt, N Taylor, D Green, R Bethall, S Madar, R Fenton, P Morley, T Pateman, A Beresford. A. J. Med. Chem, 41, 1998, 787-797

8): C Kim, W Lew, M Williams, H Liu, L Zhang, S Swaminathan, N Bischofberger, M Chen, D Mendel, C Tai, G Laver, R Stevens, J Am Chem Soc, 1997, 119, 681-690

9): P Smith, J Robinson, D Evans, S Sollis, P Howes, N Trivedi and R Bethell, Bioorganic and Medicinal Chemistry Letters 9, 1999, 601-604

10): A. J. Hay, A. J. Wolstenholme, J. J. Skehel and M. H. Smith. EMBO J,. 1985, 4, 3021: L. J. Holsinger and R. A. Lamb, Cell, 1992, 69, 517

11): J. C. Stoof, J. Booij, B. Drukarch and E. C. Wolters, Eur. J. Pharmacol., 1992, 213, 439

12): W. Graeme Laver, Norbert Bischofberger, and Robert G. Webster, Perspectives in Biology and Medicine 43.2 (2000) 173-192. This can be seen by visitinghttp://www.press.jhu.edu/journals/perspectives_in_biology_and_medicine/v043/43.2laver.html nmr

13): M. Chandler, M. J. Bamford, R. Conroy, B. Lamont, B. Patel, V. K. Patel, I. P. Steeples, R. Storer, N. G. Weir, M. Wright, C. Williamson, J. Chem. Soc. Perkin Trans. 1, 1995, 1173- 1180 nmr synth

14): A. E. Miller, J. J. Bischoff, Synthesis, 1986, 777- 779

15): G. D. Allena, S. T. Brookesa, A. Barrow, b, J. A. Dunnc and C. M. Grossec, Journal of Chromatography B: 1999, 732, 383-393

The Magic of Cubane!

PROCESS, Uncategorized Comments Off

Feb 012014

Cubane^[1]

Pentacyclo[4.2.0.0^2,5.0^3,8.0^4,7]octane

CAS 277-10-1

Cubane (C₈H₈) is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a cube, with one hydrogen atom attached to each carbon atom. A solid crystalline substance, cubane is one of the Platonic hydrocarbons. It was first synthesized in 1964 by Philip Eaton, a professor of chemistry at the University of Chicago.^[2] Before Eaton and Cole’s work, researchers believed that cubic carbon-based molecules could not exist, because the unusually sharp 90-degree bonding angle of the carbon atoms was expected to be too highly strained, and hence unstable. Once formed, cubane is quite kinetically stable, due to a lack of readily available decomposition paths.

The other Platonic hydrocarbons are dodecahedrane and tetrahedrane.

Cubane and its derivative compounds have many important properties. The 90-degree bonding angle of the carbon atoms in cubane means that the bonds are highly strained. Therefore, cubane compounds are highly reactive, which in principle may make them useful as high-density, high-energyfuels and explosives (for example, octanitrocubane and heptanitrocubane).

Cubane also has the highest density of any hydrocarbon, further contributing to its ability to store large amounts of energy, which would reduce the size and weight of fuel tanks in aircraft and especially rocket boosters. Researchers are looking into using cubane and similar cubic molecules inmedicine and nanotechnology.

Synthesis

The original 1964 cubane organic synthesis is a classic and starts from 2-cyclopentenone (compound 1.1 in scheme 1):^[2]^[3]

Reaction with N-bromosuccinimide in carbon tetrachloride places an allylic bromine atom in 1.2 and further bromination with bromine in pentane –methylene chloride gives the tribromide 1.3. Two equivalents of hydrogen bromide are eliminated from this compound with diethylamine in diethyl ether to bromocyclopentadienone 1.4

In the second part (scheme 2), the spontaneous Diels-Alder dimerization of 2.1 to 2.2 is analogous to the dimerization of cyclopentadiene to dicyclopentadiene. For the next steps to succeed, only the endo isomer should form; this happens because the bromine atoms, on their approach, take up positions as far away from each other, and from the carbonyl group, as possible. In this way the like-dipole interactions are minimized in the transition state for this reaction step. Both carbonyl groups are protected as acetals with ethylene glycol and p-toluenesulfonic acid inbenzene; one acetal is then selectively deprotected with aqueous hydrochloric acid to 2.3

In the next step, the endo isomer 2.3 (with both alkene groups in close proximity) forms the cage-like isomer 2.4 in a photochemical [2+2] cycloaddition. The bromoketone group is converted to ring-contracted carboxylic acid 2.5 in a Favorskii rearrangement with potassium hydroxide. Next, the thermal decarboxylation takes place through the acid chloride (with thionyl chloride) and thetert-butyl perester 2.6 (with t-butyl hydroperoxide and pyridine) to 2.7; afterward, the acetal is once more removed in 2.8. A second Favorskii rearrangement gives 2.9, and finally another decarboxylation gives 2.10 and 2.11.

The cube motif occurs outside of the area of organic chemistry. Prevalent non-organic cubes are the [Fe₄-S₄] clusters found pervasively iron-sulfur proteins. Such species contain sulfur and Fe at alternating corners. Alternatively such inorganic cube clusters can often be viewed as interpenetrated S₄ and Fe₄ tetrahedra. Many organometallic compounds adopt cube structures, examples being (CpFe)₄(CO)₄, (Cp*Ru)₄Cl₄, (Ph₃PAg)₄I₄, and (CH₃Li)₄.

It was mentioned previously that cubane was first prepared in 1964 by Dr. Philip E. Eaton. He was partnered by Thomas W. Cole and together they successfully completed the first synthesis, shown schematically below:

Reactive enough to undergo dimerisation via a [4+2] cycloaddition reaction to give the ENDO cycloadduct The more reactive, bridgehead ketone group is protected by Ketal formation.

The first occurance of a Hunsdiecker decarboxylation, firstly substitutes the caroxylic acid group and then removes it.

Acid hydrolysis releases the protected ketone The second instance of a Hunsdiecker decarboxylation.

The second instance of a Hunsdiecker decarboxylation.

Decarboxylation via thermal degradation of di-t-butyl perester

This, however, was soon simplified by N.B.Chapman who condensed the process to give cubane-1,4-dicarboxylic acid in five steps and so cubane in six:

n 1966 J C Barborak et al discovered yet another new synthesis of cubane. It was slightly unconventional in the fact that it utilised cyclobutadiene as a key substance to the process. Before this,cyclobutadiene was usually unavailable for the purposes of organic chemistry due to it’s instability. The shorter synthesis is shown below:

Decomposition in presences of 2,5-dibromobenzoquinone gives...

Irradiation, in benzene, with a mercury lamp initiates the intramolecular [2+2] cycloaddition reaction.

Treatment with KOH at 100 ºC gives the cubane-1,3-dicarboxylic acid

Decarboxylation via thermal degradation of di-t-butyl perester

Since the synthesis of the cubane-1,4-dicarboxylic acid has become shorter and easier, a new decarboxylation method has also devised to give increased yields of the final cubane product. This has allowed the scale of production reach multikilogram batches in places (Fluorochem in California and EniChem Synthesis in Milan) eventhough cubane and its derivatives remain expensive to purchase.

Cuneane may be produced from cubane by a metal-ion-catalyzed σ-bond rearrangement.^[4]^[5]

Cubane is a unique molecule for its extraordinary C8 cage, very high symmetry,exceptional strain and unusual kinetic stability. The particular appeal of cubane,referred to as a landmark in the world of impossible compounds, stems from therehybridization of the carbon atoms away from the canonical sp3 configuration,that is required to bound together eight CH units in a cubic framework.There is now a revival of interest on the chemistry of cubane and its functionalized derivatives,triggered by potential applications as high-energy fuels, explosives and propellantsand intermediates in pharmaceuticalpreparations.Let us now discover the synthesis and properties of this landmark molecule of impossible chemistry

Cubanehas the highest strain energy (166kcal/mol) of any organiccompounds available in multi gram amount. It is a kineticallystable compound and only decomposite above 220 Celsius Degree.It is also one of the most dense hydrocarbons ever know.However, although many physical properties of cubane have been measured, in1980 and before, cubane was considered just a laboratory curiosity of interest only to academics.It changed, in early 1980s when Gilbert of U.S ArmyArmament and Development Command (now ARDEC) pointed out that cubane’svery high heat of formation and its exceptionally high density could make certain cubanederivatives important explosives.

The effectiveness of an explosive is dependent on the energentics of the decomposition reaction,the number of moles and molecular weight of the gaseous products and also the density.

The more mols of of an explosive that can be packed into the limited volume the better. .

Highly nitrated cubanes can be predicted to be very dense and very powerful explosives.

Octanitrocubane is calculated to be 15~30%more powerful than HMX.

Cubane, which CA index name is Pentacyclo[4.2.0.02,5.03,8.04,7]octane (7CI,8CI,9CI),has exceptional structure, strain and symmetry and it is a benchmark in organic chemistry.It has been studied extensively and much of its properties has been published.Some of the physical properties are given at right hand table.

The C-C bond length is a bit longer than obtained in the original X-ray structure determination by

Fleischer in 1964. There is not much difference between this bond length and the

C-C bond length in a simple cyclobutane.

SYNTHESIS

The cubane system was first synthesized over 35 years ago by Philip Eaton and Tom Cole.
It is a highly symmetric cubic cage structure having carbon atoms at the vertices of a cube.
The synthesis needs to go through brombromocyclopentadienone
dimer I and cubane-1,4,dicarboxylic acid. It is a marvel scheme of economy and simplicity.
With only minor modification, this procedure remains to this day the best available

method for large-scale synthesis of cubane-1,4,dicarboxylic acid.

The stereospecific in situ [4 + 2] (Diels-Alder) cyclodimerization of 4-bromocyclo-pentadienone
is the key in this kinetically controlled synthesis. However, it is still a tricky matter
and a few years later after this synthesis is published, N.B.Chapman et al in England following up
this work and improved this synthesis.

Why cubane is stable?

The reason for this, unappreciated at the time of the early predictions of instability,

is that there are no kinetically viable paths along which cubane can rearrange thermally.

On one hand, orbital symmetry considerations raise the energy of concerted two-bond ring

opening reactions. On the

other, there is little to be gained by breaking just one bond as there is concomitantly

only a small change in geometry, and the resulting biradical is still very strained.

Functional group transformation

Functional groups on the cubane system generally behaves very well.Functional group transformation can be applied successfully.For example, the preparation of 1,4-dinitrocubane from cubane-1,4-dicarboxylic acid.(The mechanism is provided on the right hand side.) Classical methodology is used here.

Substitution on the cubane framework is fairly easy done by the cubyl radical.
However, the problem is such that a mixture of products are obtained.
Thus, to achieve controlled substitution on the cubane framework,
we need to carefully study the chemistry of the cubane system.

The improvement in synthesis of

cubane-1,4-dicarboxylic acid

This is the improved synthesis by N.B Chapman et al in England.

Basically the improvement is such that the

2-bromocyclopentadienone could be made easily and undergoes spontaneous dimerization.

The rest of the reaction is the same as the original one.

This synthesis now is scaled up and is conducted in small pilot plants by

Flurochem in California and EniChem Synthesis in Milan.

This method is much more superior than the old method. It is introduced by

Derek Barton et al and use the radical-induced decomposition of diester which can be

prepared easily from cubane-1,4-dicarboxylic acid.

IMPROVEMENT

This method is much more superior than the old method. It is introduced by

Derek Barton et al and use the radical-induced decomposition of diester which can be

prepared easily from cubane-1,4-dicarboxylic acid

Cubane is a colorless solid. It melts at 130- 131°C, and decomposes above the melting point.

It is soluble in CS2, CC14, CHC13, and benzene.

Spectra were obtained from 400 to 3600 cm^-l with a Beckman IR-12 spectrophotometer.

The lower limit was set by KBr cell windows. In addition a thick deposit of do was

measured down to 200 cm^-lin a Csl cell. Since no infrared bands were found, the range

200-400 cm^-l was not examined for the other compounds.

The spectral slit widths were 1-2 cm^-l in all cases.

In the infrared spectrum, there are only noticeable absorptions in the region from

4000 to 660 cm^-1appear at 300,1231, and 851 cm^-1.

Generally, for single-line proton magnetic resonance spectrum, the one

and only absorption appears at chemical shift=6.0ppm.

Originally there was doubt whether cubane does exist.

The geometry at each carbon atom is far from tetrahedral.

Only later, we found out that there is no kinetically viable paths exist for

the thermal rearrangement of cubane.

At same time, orbital symmetry considerations shows that

the energy of concerted two-bond ring-opening reactions is very high.

There will be very little gain in energy by breaking just one bond, as the

concomitant change in geometry is small, and the resulting biradical is still very strained

In 1964 Fleischer showed that cubane forms a stable solid at room temperature with a

crystalline structure composed of cubane molecules occupying corners of the rhombohedral

primitive unit cell (space group R3). The cubic molecular geometry gives the solid many unusual

electronic,structural, and dynamical properties compared to the other hydrocarbons.

For example, solid cubane has a relatively high melting point temperature about 405 K! and a

very high frequency for the lowest-lying intramolecular vibrational

mode (617 cm^-1). Recent work related to cubane has focused on solid cubane and cubane based

derivatives.Because of relatively weak intermolecular interaction the cohesive energy relative

to the constituent C₈H₈ is expected to be small, and most of the physical properties of

solid cubane are dominated by the properties of the C₈H₈molecule.

Pharmaceutical aspect of cubane

Because the cubane frame is rigid, substituent have precise spatial relationships to each another.

The distance across the cubane (the body diagonal) is almost the same as that between the para

positions of the benzene ring. On cubane, on can add substituents in the “benzene plane”, as

well as above and below it, so to speak. This offers fascinating position possibilities for

the synthesis of new pharmaceuticals. A number of cubane derivatives have already

been obtained which shows interesting activity in anti-AIDS and anti-tumor screens.

Although the activity or the toxicity balance of cubane is yet not know, the cubane

system is not inherently toxic. Most of cubanes are biologically innocuous.

The research of cubane pharmaceutical has just began. At least now,

cubane is a biologically stable, lipophilic platform on which the chemist

can install a wide range of substituents in a variety of well defined special relationships.

Developments in drug design programs should allow the judicious choice.

Dipivaloylcubane: a cubane derivatized with keto, cyano, and amide groups,

shown on the left- exhibits moderate activity against human immunodeficiency virus (HIV),

which causes AIDS, without impairing healthy cells.

Polymers of cubane:

Optically transparent cubanes and cubylcubanes have been proposed as building

blocks for rigid liquid-crystal compounds. UV active cubanes, for example cubyl ketones,

are readily transformed photochemically into coloured cyclooctatetraenes;this transformation

can be used to permanent information storage.

Another example of UV active cubane, which can be used to synthesis liquid crystals.

Polymers with cubane in the backbone or as a pendant group along a polymer chain is

focused now.

The cubane subunits in these polymers can be rearranged easily to cycloctatetraenes.

It is expected that polycyclooctatetra can be converted in to polyacetylenes by

the way of ring-opening metathesis polymerization. The polyacetylenes will have properties

which are enhanced by the chain being intrinsically part of another polymer.

These properties including stability and extrudability and etc. A example is shown below:

Cubane derivative could be the structural basis for a class of intrinsic small gap polymers.The small gap polymer could present intrinsic good conductivity without doping,good nonlinear optical and photoelectric properties.Investigation of oligamers with up to six units of a conjugated unsaturated cubane derivative,where all the hydrogen were removed, is carried out.The table below shows that the gap values in eV by EHT and PM3.These values suggest to us that these structures could be used to design a newclass of polymers with very small gap.

Explosive and fuels:

In the early 1980s Everett Gilbert of the U.S. Army Armament Research and Development

Command (now ARDEC) pointed out that the nitrocarbon octanitrocubane (ONC),

then unknown, has a perfect oxygen balance, and in light of the properties of the

parent hydrocarbon cubane should have a very high heat of formation per CNO₂ unit

and an exceptionally high density as well. His colleagues Jack Alster, Oscar Sandus

and Norman Slagg at ARDEC provided theoretical support for Gilbert’s

brilliant insight and estimated that ONC would have a detonation pressure

significantly greater than HMX. Later, both statistical and computational

approaches predicted a density of 2.1 ± 2.2 g /cm³ for octanitrocubane,

greater than any other C, N, O compound.

Is Cubane a really good explosives?

Quantitative evaluation of the potential of a candidate explosive before synthesis is very difficult.

Currently, estimation of energetic properties relies on the empirically derived Kamlet and Jacobs

equations:

In these equations the heat released by the decomposition, the number of moles of gas produced,

and the molecular

weight of these gases are all critical factors. Density too is crucial.

Obviously, the more molecules of a high-energy material that can be packed into the limited

volume of a shell or rocket the better. Less obvious, but more important, density affects the

detonation velocity of an explosive.

This is a specialized “linear” rate of reaction that ranges from 5 to 10 km/s in

explosives and affects the maximum detonation pressure, a direct measure of the

power of an explosive. For a given explosive, the detonation pressure is proportional

to the square of its density, so great effort is made to obtain the highest density form

of any particular explosive.

Quantitative evaluation of the potential of a candidate explosive before synthesis is very difficult.

Currently, estimation of energetic properties relies on the empirically derived Kamlet and Jacobs

equations:

In these equations the heat released by the decomposition, the number of moles of gas produced,

and the molecular

weight of these gases are all critical factors. Density too is crucial.

Obviously, the more molecules of a high-energy material that can be packed into the limited

volume of a shell or rocket the better. Less obvious, but more important, density affects the

detonation velocity of an explosive.

This is a specialized “linear” rate of reaction that ranges from 5 to 10 km/s in

explosives and affects the maximum detonation pressure, a direct measure of the

power of an explosive. For a given explosive, the detonation pressure is proportional

to the square of its density, so great effort is made to obtain the highest density form

of any particular explosive.

Numerous nitro compounds are employed commonly as military and commercial explosives.

There is a continuing search for more powerful and less shock-sensitive examples.

Such materials are also sought as potentially useful fuels and propellants.

Most interest is focused on high-density organic compounds that contain all of the

elements needed for combustion to gaseous products in the absence of air.

Nitrocubanes carrying five or more nitro groups contain enough oxygen to oxidize

all constituent carbon and hydrogen atoms to gaseous CO, CO₂, or H₂O.

Each of these, along with N₂, “explodes” from the solid to 12 gaseous molecules.

The expansion from the dense solid to a lot of gas (much expanded by the released heat)

produces the desired effect in propellants and explosives. ONC has a “perfect”

oxygen balance and would produce (were the detonation completely efficient)

eight molecules of carbon dioxide and four of dinitrogen. As ONC has no

hydrogen, no water forms when it burns; when used as propellants such zero-hydrogen

compounds leave little or no visible smoke (steam) in the plume behind the rocket;

such “low-signature” rockets are difficult to track.

On application of the Kamlet and Jacobs equations led ARDEC to predict that

octanitrocubane would be a very much better explosive (Table 1) than the classic

C-nitro compound trinitrotoluene (TNT), perhaps 15±30% better than the nitramine

HMX (the most powerful, commonly used military explosive), and at least competitive

with (and perhaps less shock-sensitive than) the newest experimental explosive CL-20

SYNTHESIS:(1)

The high strain that the cubane framework is under has already been highlighted. The researchers had to very cautiously attach a nitro group to each of the corners of the cube in order to make the desired product. The insertion of the first four nitro groups could be done by manipulating functional groups:

The key intermediate, cubane-1,3,5,7- tetracarboxylic acid (TNC), was obtained by clever application of the Brown-Kharasch photochlorocarbonylation to cubane mono-acid.

The addition of four further nitro groups proved far more difficult and new methodologies had to be developed, specifically the process of interfacial nitration. This method was used successfully to convert the sodium salt of TNC to pentanitrocubane (PNC) and then hexanitrocubane (HNC), both are stable materials.

Interfacial nitration, however, proved deficient for further nitration of HNC and again new experimental methodology had to be developed for its successful conversion to heptanitrocubane (HpNC):

Addition of excess NOCl to a solution of the lithium salt of HpNC in dichloromethane at -78°C gave the long-sought ONC:

DIFF TYPES

For the last planned post in my Unnatural Products series, I’m going to write about Eaton’s 1981 synthesis of pentaprismane.[A] At the time, unnatural hydrocarbons were hot targets, and as the next largest prismane on the list this target was the subject of much research by groups around the world. Perhaps Eaton’s biggest rivals were the groups of Paquette and Petit, and in fact all three had, at various times, synthesised hypostrophene as an intended precursor to the target.

Unfortunately, the ‘obvious’ [2 + 2] disconnection from pentaprismane turned out to be a dead end and the photochemical ring closure was unsuccessful. The 1970s and early 1980s saw the publication of a number of other similarly creative, but sadly ill-fated, approaches based on various ring contractions, and the compound gained a well-earned reputation for extraordinary synthetic inaccessibility.

Eaton’s route began, as with the cubane and dodecahedrane syntheses previously covered in this series, with a Diels-Alder reaction. The diene used was the known tetrachlorocyclopentadienone acetal shown that upon heating neat with benzoquinone produced the endo adduct shown in excellent yield. Next, an even higher yielding photochemical [2 + 2] reaction was used to close the cage-like structure by cyclobutane formation. Treatment with lithium in liquid ammonia simultaneously reduced both ketones and removed all four chlorine atoms. The resulting diol was converted to the ditosylate, which, under carefully controlled conditions with sodium iodide in HMPA, underwent a mono-Finkelstein reaction to give the iodotosylate shown. When this was treated with t-BuLi halogen-lithium exchange, followed by an extraordinary fragmentation, gave a diene reminiscent of hypostrophene shown above. However, the extra carbon atom in the skeleton made all the difference, and unlike the parent compound, this did undergo a [2 + 2] cycloaddition when exposed to UV light. Finally, acetal hydrolysis gave homopentaprismane in 34% yield from benzoquinone, putting the group a single ring contraction from victory.[B]

With significant amounts of homopentaprismanone in hand, the group now intended to employ the transformation that had been the cornerstone of their cubane synthesis – the Favorskii rearrangement. Unfortunately, this required the introduction of a leaving group in the ketone α-position, a transformation made incredibly difficult due to the strained system and Bredt’s rule, which prevented enolisation.[C] Eventually a six-step sequence (!) to introduce a tosyloxy group was devised, beginning with a Baeyer-Villiger reaction using m-CPBA. A remarkable CH oxidation with RuO4, generated in situ, then gave the hydroxylactone. Treatment of this with diazomethane gave the corresponding δ-ketoester in almost quantitative yield. The group then reformed the starting norbornane-like bridge through use of an unusual acyloin type reaction effected by treatment with sodium in liquid ammonia. Finally, oxidation of the secondary alcohol and tosylation gave the Favorskii precursor, apparently preparable in muti-gram quantities.

Treatment with aqueous potassium hydroxide solution effected Favorskii rearrangement in excellent yield, especially considering that this was the first time the elusive pentaprimane ring system had been prepared. Finally, Eaton used the three-step decarboxylation he had developed for cubane to remove the extraneous acid and give pentaprismane in 18 steps. Awesome.[D]

References and suchlike

A J. Am. Chem. Soc., 1981, 103, 2134. Much like Eaton’s seminal cubane paper, the title is a single word, ‘Pentaprismane’. I love the lack of hype.
B Although Petit had prepared this compound a full decade earlier, his approach relied on a cycloaddition of the difficult to prepare cyclobutadieneiron tricarbonyl with the acetal of tropone, and proved difficult to scale up. In fact, in his own paper Eaton rather directly described it as ‘conceptually fascinating [but] useless synthetically’.
C Eaton uses the phrase ‘invasion at the bridgehead’, which I find delightfully evocative. Makes it sound like a second world war campaign. Apparently the group initially planned, in spite of Bredt’s rule, to deprotonate the bridgehead position, relying on inductive stabilisation of the anion rather than enolate formation, but were unable to do so.
D Pentaprismane is the most recent of three prismanes synthesised to date, the other two being cubane, and triprismane. Although I think triprismane looks quite silly, it was actually synthesised some 8 years previouslyby T. J. Katz in far fewer steps. Go figure.

The Amide Activating Group

The very first step of cubane frame substitution will be the activation of the cubane frame.

This can be done by amides. The idea is derived from the similarities between cubane and arenes.

Both of them have C-H bonds with enhanced s character ( see structure),

and in both the adjacent (ortho) substituents are forced to be coplanar.

A more specific example is the cubane-N,N-diisopropyl carboxamide

reacts with excess lithium tetramethylpiperidide (LiTMP) in THF solvent.

About 3% of the deuteriation products obtained.

The diisopropyl amide activating group is used because it is inert to the amide

bases employed for ortho metalation. Although there is a problem, there is

difficulty in hydrolyzed it the corresponding carboxylic acid.

The problem is finally solved by using borane reduction followed by the oxidation

of the amine so produced with dimethyldioxirane or potassium permanganate (in large scale).

Transmetalation is the basis of a complete synthetic methodology for the preparation

of a great variety of the substituted cubanes.

In order to make the substitution productively, a way must be found to

make use of the small amount of anion in the equilibrium with the starting material.

Mercury salt is used here as an effective anion trap and very little starting material remain unreacted.

The mercury for lithium transmetalation resulted in nearly complete conversion of the

starting material by drawing the lithiation equilibrium to the right.

The amide group is important in stabilizing the intermediate lithiated cubane,

but not the mercuriated compound. Once the lithium is replaced by mercury,

the amide group is again able to assist removal of another ortho-hydrogen atom.

In the end, the complex ortho-mercurated product mixture obtained was

simplified by treatment with elemental iodine.

The iodine cleavage of the carbon-mercury bonds 2-iodo and 2,6-diiodo derivatives

of the starting amide in72% and 15% respectively

Cubyl Grignard Reagents

From transmetalation, a reverse transmetalation was also developed, which is basically adding Grignard reagent to the mercuriated cubane instead of the iodine. However, these processes have a great main disadvantage, the mercury is highly toxic. Thus, scale up of this method was limited.

In 1988, Bashir-Hashemi introduced transmetaltion with magnesium salts and thereby provided easy access to cubyl mono-and bis-Grignard reagents. It is a reaction of cubane diamide with an excess of LiTMP/MgBR₂in THF and quenching with I₂ gave diiodocubane diamide of 72% yield.

The effect of the presence of electron withdrawing group – Cyanide

When electron withdrawing group such as cynate present, they stabilize both intermediate lithiated cubanes very well. As a result, only a small amount of LiTMP is need to achieve fairly complete deprotonation even at -78°C.

The inductive effect of the cyano group clearly enhances the reaction. However, the adding of cyano groups results in competitive lithiation and a mixture of products. However, this problem can be well trackled by adding MgBr₂.The product ratio was improved to 9:1 favoring carboxyliation ortho to the amide function.

A mixture of product formed.

Increased selectivity by adding MgBr₂

Since the reactivity of cubane metalation is enhanced greatly with presence of cyano groups, it is possible to substitute all three positions ortho to the amide in a simple reaction. For instance, 4-cyanocubanamide can be converted directly into the tri(tert-butylcarbonyl)derivative as shown below.

Through Baeyer-Villiger oxidation, ter-butyl cuybl ketones can be converted easily to the polycarboxyliated cubane.

PHENYL CUBANE

From the basis idea of cubyl Grignard Reagent, phenyl cubane can be synthesised. The reaction of cubane diamide with 10 equiv of LiTMP and 4.0 equivalents of MgBr2 etherate in THF at 0°C followed by the addition of 10.0 equiv of bromobenzene, gave diphenylcubane diamide in 53% yield.

The mechanism is shown below:

The benzyne intermediate was formed in situ from the reaction of excess of LiTMP with bromobenzene. For a similar reaction, MeMgBr is used and give 30% yield of bromo-phenylcubane diamide, the first cubane derivative containing 3 different substituents.

Now, let us look the main concern of the cubane derivatives–the nitrocubanes.

Nitrocubanes are sought to be powerful, shock-insensitive, high-density explosives. They are stable compounds with decomposition points above 200°C. Simple nitrocubane can be made from simple oxidation of amines( See Functional Group Transformation.)

If we want to add more nitro groups into the cubane nucleus, we cannot do it though transmetalation because there is unstoppable cage cleavage reactions when make adjacent nitro groups. The ab initio calculation has confirmed this destabilising effect.

We are going to discuss how to make more and more substituted nitrocubane until octanitrocubane(ONC), the ultimate power house, is synthesised.

1,3,5 trinitrocubane and 1,3,5,7 tetranitrocubane(TNC)

As we mention early, addition of nitro groups cannot be done through direct transmetalation. Thus, we need found some indirect route.

This is done by introducing a substituent on each of 3 ortho carbons and remove the ortho-activating group in the end.

By adding a electron-withdrawing group such as a cyano group will help the case here. This choice of original substituent is important here and when cyano group is chosen, it activates the cubane nucleus without affecting the ortho directing by the diamide (for details please refer to electron-withdrawing group-cyanite).

When the dicyano amide was treated with TMPMgBr in THF and quenched with CO₂. The ortho (to amide) carboxylic acid was the only product.

Even when the much activated tricyanoamide is treated with TMPMgBr and CO₂ ,again, the ortho position ( to amide) carboxylic acid was formed.

The removal of the carboxamido group is done through a smart yet tedious process. The cyano group is converted to acid group first. Then, it is reduced to alcohol by lithium aluminium hydride. At same time, the carboxamido is reduced to aminotetrol. The alcohols are protected as acetates and amino tetrol is converted to carboxylic acid. The carboxylic is then removed through Barton Decarboxylatio. A detail mechanism is provided below.

The cubane-1,3,5,7-teracarboxylic acid is converted to TNC on the mechanism as follow:

The whole process is very clever, but it is very long. Thus, in 1997, a improved synthesis method for TNC was proposed by making use of the photochemsitry.

Improved synthesis for TNC

In 1993, Bashir-Hashemi showed the cubane-1,3,5,7-tetracarboxylic acid chloride can be formed by applying photochemically induced chlorocarbonyl cation( the Kharasch_Brown Reaction).

For a fast reaction, a high power Hanovia of 450 watts, medium pressure Hg was used. The favoured products are cubane tetraacid chloride shown on the right hand side. The first one, cubane-1,3,5,7-tetracarboxylic acid, made up 30% overall. This reaction conveniently prepare us the important versatile intermediate .

A detail conversion process is provided below:

A catalyst TMSN₃ is used in converting tetraacid chloride to tetracylazide. The rest is the same as the orginal reaction.

TNC is a thermodynamic powerhouse but remarkly stable kinetically. Figure 1 shows that rapid thermal decomposition doesnot start until over 250°C.

The literature was unsupportive of this optimistic view. Poor results were also obtained initially with nitrating agent such as NO₂BF₄, acetyl nitrate, amyl nitrate etc.

Tetranitrocubylsodium can be formed directly on treatment of TNC with sodium bis(trimethylsilyl) amide in THF at -75°C. It can react with electrophiles to provide a useful and convenient way to achieve further functionalization of cubane nucleus.

More substituted nitrocubanes-

Pentanitrocubane(PNC) and Hexanitrocubane(HNC)

PNC

Base on the property of tetranitrocubylsodium, nitryl chloride(NO₂Cl) was used to further nitrate the cubane nucleus. Treatment of NO₂Cl with tetranitrocubylsodium in THF at -75°C works out 10-15% yield of pentanitrocubane(PNC). The yield increased to 30% when the solution was frozen to-180°C and allowed to warm slowly. This is called the interfacial nitration process. It is suggested that NO₂Cl oxidized tetranitrocubylsodium to a radical, which made the whole reaction worked.

Base on the property of NO₂Cl , N₂O₄ should be a better choice. The results showed that it is actually a better with 60:40 PNC to TNC ratio. The reaction is extremely clean.

PNC is colourless and highly crystalline. It is the first nitrated cubane to contain adjacent nitro groups. It behaves just TNC and other nitrocubanes, remarkly stable kinetically.

HNC

Although HNC can be prepared the same way as PNC, but the separation between PNC and HNC is extremely difficult.

However, if TIPS-substituted PNC( by N₂O₄ nitration from TIPS-sub TNC) react with potassium base (K(TMSN)₂and the nitration with N₂O₄ gave a mixture of (triisopropyl) HNC and PNC in 60:40 ratio. This step is important and crucial. The separation is now possible by column chromatography on silica gel. 30% isolated yield of PURE HNC could be obtained when further treated with SiO₂.

Synthesis for the last two nitro cubanes- heptanitrocubane and octanitrocubane

Interfacial nitration is not sufficient to further nitration for heptanitrocubane. Al though it is very good in deed, we need to find something which can successfully convert heptanitrocubane (HpNC).

HpNC

In this procedure TNC was treated with at least 4 equivalents of the base NaN(TMS)₂ (where TMS = trimethylsilyl) at ±78 C in 1:1 THF/MeTHF. After the mono sodium salt had formed, the solution was cooled to between ±125 and ±130°C giving a clear, but very viscous fluid. This was stirred vigorously as excess N₂O₄ in cold isopentane was added. After one minute, the base was quenched, and the whole mixture was added to water. This resulted reproducibly in almost complete conversion of TNC (1 g scale) to HpNC (95% by NMR), isolated crystalline in 74% yield!

ONC

However, even in the presence of excess nitrating agent (N₂O₄ or many others) no indication
of any formation of ONC was ever seen. It is suspected that anion nitration with N₂O₄ proceeds by oxidation of the carbanion to the corresponding radical.Perhaps the anion of HpNC is too stabilized for this to occur. (HpNC is significantly ionized in neutral methanol.) This concept led to the use of the more powerful oxidant nitrosyl chloride. Addition of excess NOCl to a solution of the lithium salt of HpNC in dichloromethane at 78° C followed by ozonation at 78° C gave the long-sought ONC in 45±55% isolated yield on millimole scale. The intermediate product prior to oxidation is thought to be nitrosoheptanitrocubane.

Finally, the magic molecule, the so called the impossible molecule, octanitrocubane was synthesised. But, how good are they and how useful are they? Let us discuss about it in the following section.

Properties of nitrocubane:

Neither HpNC nor ONC is detonated by hammer blows!
Both have decomposition points well above 200 C. Octanitrocubane
sublimes unchanged at atmospheric pressure at 200 C. HpNC forms beautiful, colorless, solvent-free crystals when
its solution in fuming nitric acid is diluted with sulphuric acid. Single-
crystal X-ray analysis confirmed the assigned structure and
provided an accurate density at 21 C of 2.028 g cm±3, impressively
high for a C, H, N, O compound. Although octanitrocubane
catches the imagination with its symmetry, heptanitrocubane
currently is significantly easier to make than ONC. It is
denser, and it may be a more powerful, shock-insensitive explosive
than any now in use. According to page 41 of a 2004 IUPAC guide, cubane is the “preferred IUPAC name.”

‘ ‘Cubaneand Thomas W. Cole. Philip E. Eaton and Thomas W. Cole J. Am. Chem. Soc.; 1964; 86(15) pp 3157 – 3158; doi:10.1021/ja01069a041.
The Cubane System Philip E. Eaton and Thomas W. Cole J. Am. Chem. Soc.; 1964; 86(5) pp 962 – 964; doi:10.1021/ja01059a072
Michael B. Smith, Jerry March, March’s Advanced Organic Chemistry, 5 th Ed., John Wiley & Sons, Inc., 2001, p. 1459. ISBN 0-471-58589-0
K. Kindler, K. Lührs, Chem. Ber., vol. 99, 1966, p. 227.

Dimethyl cubane-1,4-dicarboxylate

dimethyl 1,4-cubanedicarboxylate;

**1,4-cubanedicarboxylic acid dimethyl*ester;**

methyl 4-(methoxycarbonyl)pentacyclo[4.2.0.0<2,5>.0<3,8>.0<4,7>]octanecarboxylate

Pentacyclo(4.2.0.0(2,5).0(3,8).0(4,7))octane-1,4-dicarboxylic acid dimethyl ester

CAS 29412-62-2

Molecular Weight:	220.2213
Molecular Formula:	C₁₂H₁₂O₄
Density:	1.684g/cm³
Boiling Point(℃):	270°C at 760 mmHg
Flash Point(℃):	131.3°C
refractive_index:	1.704

An interesting OPRD paper on the scale up of dimethyl cubane -1,4-dicarboxylate.

The work appeared in Organic Process Research and development, 2013, doi.org/10.1021/op400181g . It was carried out by an Australian group, John Tsanaktsidis, Michael Falkiner, Stuart Littler, Kenneth McRae and Paul Savage from CSIROand features a large-scale photochemical reaction which is very unusual to see in a scaled chemical process.

Extending their previous work from 1997, they scaled the following reaction.

As is the norm with such reactions the reaction requires high dilution to be successful. In this case they used a tailor made photochemical reactor. A solution of 1 in methanol/water was pumped through the reactor at 4 L/minute and the conversion of 1 to 2 was noted as 1g/4 minutes of irradiation.

This meant a total time of 173 hours. Further processing of 2 through the double Favourskii ring contraction required significant development but eventually delivered the di-sodium salt corresponding to the di-ester of cubane.

One needs to be careful with these cubanes as they are, due to the highly strained nature of the system quite energetic materials, the do-acid and ester being more stable than the parent hydrocarbon. However the energy released upon warming above the melting point is not insignificant.

This paper represents a good demonstration of the scale-up of several very difficult chemical reactions, including excellent descriptive paragraphs of the problems and solutions. They are to be congratulated on a very nice piece of work.

See below

A scalable process for the preparation of high purity dimethyl 1,4-cubanedicarboxylate (3) is reported.

The work described herein builds on previous synthetic work from this and other laboratories, to provide a reliable process that can be used to prepare multigram quantities of 3 in a partially telescoped, 8 step process, with minimal purification of intermediates.

Pilot-Scale Production of Dimethyl 1,4-Cubanedicarboxylate

Michael J. Falkiner , Stuart W. Littler , Kenneth J. McRae , G. Paul Savage , and John Tsanaktsidis *

CSIRO Materials Science & Engineering, Ian Wark Laboratory, Bayview Avenue, Clayton Victoria 3168,Australia

Org. Process Res. Dev., 2013, 17 (12), pp 1503–1509

DOI: 10.1021/op400181g

Publication Date (Web): November 8, 2013

http://pubs.acs.org/doi/full/10.1021/op400181g?prevSearch=cubane&searchHistoryKey=

Scheme 5. Pilot-Scale Synthesis of Dimethyl 1,4-Cubanedicarboxylate (3)

Figure 1. Cubane nucleus.

Step 5

A dry 100 L glass reactor was charged with the crude diacid 2 (1287 g), dry methanol (36 L), and Dowex ion-exchange resin 50WX8–100 (176 g) that was prewashed with 1 L of methanol. This mixture was then stirred (150 rpm), and heated under reflux for 18 h under an atmosphere of nitrogen. The mixture was then cooled to room temperature and filtered to remove the resin. The methanol solution mixture was then evaporated to dryness using a rotary evaporator (45 °C at 45 mmHg) leaving behind the crude diester 3 (863 g) as a dark brown solid. Purification by sublimation (100–120 °C/0.01 mmHg), followed by recrystallization from acetonitrile furnished the diester 3 (560 g, 30%), as a colorless solid,

mp 164.5 °C (lit. 161–162 °C).(47)

1H NMR δ: 3.7, s, 6H 4.24, s, 6H, ring protons.

13C NMR δ: 47.03, 51.55, 55.77, 171.89.

………………………………..

http://cst-www.nrl.navy.mil/lattice/struk/c8h8.html.

http://www.ch.ic.ac.uk/local/projects/b_muir/Enter.html.

http://www.sciencedirect.com.

http://www.sciencenews.org/.

http://www.winbmdo.com/.

Bashir-Hashemi, A., New developments in cubane chemistry: phenylcubanes.

J. Am. Chem. Soc.;1988;110(21);7234-7235, 110(21), 7234-7235.

D.S.Calvao, p. m. v. b. B. A. C. J. a., Theooretical Characterization of oligocubane.

Synthetic Metals 102 (1999) 1410.

E. W. Della, E. F. M., H. K. Patney,Gerald L. Jones,; Miller, a. F. A.,

Vibrational Spectra of Cubane and Four

of Its Deuterated Derivatives.

Journal of the American Chemical Society / 101.25 / December 5, I979,7441-7457.

Galasso, V., Theoretical study of spectroscopic properties of cubane.

Chemical Physics 184 (1994) 107-114.

Kirill A. Lukin, J. L., Philip E. Eaton,*,Nobuhiro Kanomata,Juirgen Hain,Eric Punzalan,and

Richard Gilardi, Synthesis and Chemistry of 1,3,5,7-Tetranitrocubane Including

Measurement of Its Acidity, Formation of o-Nitro Anions, and

the First Preparations of Pentanitrocubane and Hexanitrocubane.

J. Am. Chem. Soc., Vol. 119, No. 41, 1997,9592-9602.

P.E.Eaton, Cubanes: starting Materials For the chemistry of 1990s and the New Century.

J. Am. Chem. Soc.;1992;31;1421-1436, 31, 1421-1436.

Philip E. Eaton, t. Y. X., t and Richard Gilardi*, Systematic Substitution on the Cubane Nucleus.

Synthesis and

Properties of 1,3,5-Trinitrocubane and 1,3,5,7-Tetranitrocubane

. J. Am. Chem. SOC.1993,115, 10195-10202.

Philip E. Eaton, R. L. G.; Zhang, a. M.-X., Polynitrocubanes: Advanced High-Density,

High-Energy Materials**. Adv. Mater. 2000, 12, No. 15, August 2.

Philip E. Eaton, Cubane: Starting Materials for the chemistry of the 1990s and the new century.

Angew.Chem.Int.Ed.Engl.1992,31,1421-1436.

Philip E. Eaton, t. Y. X., t and Richard Gilardi*, Systematic Substitution on the Cubane Nucleus.

Synthesis and

Properties of 1,3,5-Trinitrocubane and 1,3,5,7-Tetranitrocubane.

J. Am. Chem. SOC., Vol. 115, No. 22, 1993,10196-10202.

T. YILDIRIM, P. M. G., D. A. NEUMANN, P. E. EATONC and ‘T. EMRICK’, SOLID

CUBANE: A BRIEF REVIEW. Carbon Vol. 36, No. 5-6, pp. 809-815,1998.

Zhang, P. E. E. a. M.-X., Octanitrocubane: A New Nitrocarbon.

Propellants, Explosives, Pyrotechnics 27, 1 – 6 (2002).

VARDENAFIL

Uncategorized 1 Response »

Jan 312014

VARDENAFIL

224785-90-4^{CAS NO}

Vardenafil hydrochloride (CAS NO.224785-91-5)

Formula	C₂₃H₃₂N₆O₄S
Mol. mass	488.604 g/mol

4-[2-Ethoxy-5-(4-ethylpiperazin-1-yl)sulfonyl-phenyl]-9-methyl-7-propyl-3,5,6,8-tetrazabicyclo[4.3.0]nona-3,7,9-trien-2-one

Vivanza, Vardenafil (INN), Levitra (TN), STK642629, , LEVITRA

Vardenafil (INN) is a PDE5 inhibitor used for treating erectile dysfunction that is sold under the trade names Levitra (Bayer AG, GSK, and SP) andStaxyn.

Vardenafil was co-marketed by Bayer Pharmaceuticals, GlaxoSmithKline, and Schering-Plough under the trade name Levitra. As of 2005, the co-promotion rights of GSK on Levitra have been returned to Bayer in many markets outside the U.S. In Italy, Bayer sells vardenafil as Levitra and GSK sells it as Vivanza. Thus, because of European Union trade rules, parallel imports might result in Vivanza sold next to Levitra in the EU.

Vardenafil (Levitra) is an oral therapy for the treatment of erectile dysfunction. It is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMPspecific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP.

An orally disintegrating form, marketed as Staxyn, has been gaining approvals in countries such as the United States^[1] and Canada.^[2]

Vardenafil’s indications and contra-indications are the same as with other PDE5 inhibitors; it is closely related in function to sildenafil citrate (Viagra) and tadalafil (Cialis). The difference between the vardenafil molecule and sildenafil citrate is a nitrogen atom’s position and the change of sildenafil’spiperazine ring methyl group to an ethyl group. Tadalafil is structurally different from both sildenafil and vardenafil. Vardenafil’s relatively short effective time is comparable to but somewhat longer than sildenafil’s.

Beyond its indications for erectile dysfunction, vardenafil may be effective in the treatment of premature ejaculation, where it may significantly increase the time from vaginal penetration to ejaculation.^[3]

The common, adverse drug reactions (side-effects) are the same as with other PDE5 inhibitors. The frequent vardenafil-specific side-effect is nausea; the infrequent side-effects are abdominal pain, back pain, photosensitivity, abnormal vision, eye pain, facial edema, hypotension, palpitation,tachycardia, arthralgia, myalgia, rash, itch, and priapism.

One possibly serious, but rare, side-effect with vardenafil is heart attack. Also, in rare cases, vardenafil use may cause priapism, a very painful emergency condition that can cause impotence if left untreated.^[4]

On 18 October 2007, the U.S. Food and Drug Administration (FDA) announced that a warning about possible deafness (sudden hearing loss) would be added to the drug labels of Vardenafil, and other PDE5 inhibitors.^[5]

Vardenafil, as with all PDE5 inhibitors, should not be used by men taking nitrate medications, because combining them with vardenafil might provoke potentially life-threatening hypotension (low blood pressure).

Further, Vardenafil causing lengthening of the QT interval. Therefore it should not be taken by men taking other medications that affect the QT interval (such as amiodarone).

Levitra 20mg Oral Tablet

It is available in 2.5 mg, 5 mg, 10 mg, and 20 mg doses in round orange tablets. The normal starting dose is 10 mg (roughly equivalent to 50 mg of sildenafil). Vardenafil should be taken 1 to 2 hours prior to sexual activity, with a maximum dose frequency of once per day. In some territories, such as the UK, only certain doses may be available.

Vardenafil is also available under the name Staxyn as a tablet which dissolves on the tongue rather than being swallowed in the form of a pill.

STAXYN is an oral therapy for the treatment of erectile dysfunction. This monohydrochloride salt of vardenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific PDE5.

Vardenafil HCl is designated chemically as piperazine, 1-[[3-(1,4-dihydro-5-methyl-4-oxo-7-propylimidazo[5,1f][1,2,4]triazin-2-yl)-4-ethoxyphenyl]sulfonyl]-4-ethyl-, monohydrochloride and has the following structural formula:

STAXYN (vardenafil hydrochloride) Structural Formula Illustration

Vardenafil HCl is a nearly colorless, solid substance with a molecular weight of 579.1 g/mol and a solubility of 0.11 mg/mL in water.

LEVITRA

TRIHYDRATE, HCL SALT

Abbreviated New Drug Application (ANDA)

US2002137930A

vardenafil hydrochloride is piperazine, 1-[[3-(1,4-dihydro-5-methyl-4-oxo-7-propylimidazo[5,1-f][1,2,4]triazin-2-yl)-4-ethoxyphenyl]sulfonyl]-4-ethyl-, mono -hydrochloride and can be structurally represented by Formula I.

The monohydrochloride salt of vardenafil is a selective inhibitor of cyclic guaosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). It is commercially available in products sold under the brand name LEVITRA formulated as 2.5 mg, 5 mg, 10 mg, 20 mg film-coated tablets.

U.S. Pat. No. 6,362,178 B1 discloses vardenafil, its related compounds and processes for their preparation. The patent describes a process in which vardenafil is obtained by recrystallization in ether in Example 19. Vardenafil produced as per Example 19 is hereinafter referred as “crystalline Form I” of vardenafil. The patent also describes processes for the preparation of its monohydrochloride and dihydrochloride salts, which are formed in a combination of ether and dichloromethane. The patent also describes a process for the preparation of vardenafil monohydrochloride trihydrate.

U.S. Patent Application Publication No. 2005/0203298 also describes a process for the preparation of vardenafil, and its monohydrochloride trihydrate.

Chemical synthesis of vardenafil has mostly been directed to the preparation of the trihydrate of monohydrochloride of vardenafil.

In WO 99/24433, sulphonamide-substituted imidazotriazinones are described as potent inhibitors of either one or more of the cyclic guanosine 3′,5′-monophosphate-metabolizing phosphodiesterases (cGMP PDEs). According to the nomenclature of Beavo and Reifsnyder (Trends in Pharmacol. Sci. 11, 150-155, 1990), these cGMP PDEs are the phosphodiesterase isoenzymes PDE-I, PDE-II and PDE-V.

According to WO 99/24433, the sulphonamide-substituted imidazotriazinones described therein are prepared from corresponding 2-ethoxyphenyl-substituted imidazotriazinones by reaction with chlorosulphonic acid and subsequent reaction with an appropriate amine, as is illustrated by the following scheme (R¹to R⁶here have the meanings indicated in WO 99/24433):

In this process, highly reactive chlorosulphonic acid has to be used as a reagent. Moreover, the imidazotriazinonesulphonyl chlorides formed as intermediates are sensitive to hydrolysis, which, in particular in the conversion of this preparation process to the industrial scale, can lead to not inconsiderable yield variations.

It was therefore the object of the present invention to make available a process for the preparation of sulphonamide-substituted imidazotriazinones in which the disadvantages of the above process known from the prior art are avoided.

This object is achieved according to the present invention by a process as in claim 1. In particular, in the process according to the invention as in claim 1 the use of chlorosulphonic acid is avoided by introduction of the sulphonic acid via a reaction with sulphuric acid and subsequent reaction with thionyl chloride. Moreover, the reaction with thionyl chloride and the subsequent reaction with an amine is carried out in a one-pot process, so that the imidazotriazinonesulphonyl chloride intermediate, which is sensitive to hydrolysis, does not need to be isolated. By means of this, yield variations on account of partial hydrolysis of this intermediate can be excluded. As a result of these advantages, the process according to the invention is much simpler to carry out on the industrial scale than the process described in WO 99/24433.

………………….

SYNTHESIS

US6362178

2-butyrylamino-propionic acid

EXAMPLE 1A 2-Butyrylaminopropionic acid

22.27 g (250 mmol) of D,L-alanine and 55.66 g (550 mmol) of triethylamine are dissolved in 250 ml of dichloromethane, and the solution is cooled to 0° C. 59.75 g (550 mmol) of trimethylsilyl chloride are added dropwise, and the solution is stirred for 1 hour at room temperature and for 1 hour at 40° C. After cooling to −10° C., 26.64 g (250 mmol) of butyryl chloride are added dropwise, and the resulting mixture is stirred for 2 hours at −10° C. and for one hour at room temperature.

With ice-cooling, 125 ml of water are added dropwise and the reaction mixture is stirred at room temperature for 15 minutes. The aqueous phase is evaporated to dryness, the residue is titrated with acetone and the mother liquor is filtered off with suction. The solvent is removed and the residue is chromatographed. The resulting product is dissolved in 3N aqueous sodium hydroxide solution and the resulting solution is evaporated to dryness. The residue is taken up in conc. HCl and once more evaporated to dryness. The residue is stirred with acetone, precipitated solid is filtered off with suction and the solvent is removed under reduced pressure. This gives 28.2 g (71%) of a viscous oil which crystallizes after some time.

200 MHz ¹H-NMR (DMSO-d6): 0.84, t, 3H; 1.22, d, 3H; 1.50, hex, 2H; 2.07, t, 2H; 4.20, quin., 1H; 8.09, d, 1H.

EXAMPLE 3A 2-Ethoxybenzonitrile

25 g (210 mmol) of 2-hydroxybenzonitrile are refluxed with 87 g of potassium carbonate and 34.3 g (314.8 mmol) of ethyl bromide in 500 ml of acetone overnight. The solid is filtered off, the solvent is removed under reduced pressure and the residue is distilled under reduced pressure. This gives 30.0 g (97%) of a colourless liquid.

200 MHz ¹H-NMR (DMSO-d6): 1.48, t, 3H; 4.15, quart., 2H; 6.99, dt, 2H; 7.51, dt, 2H.

2-ethoxybenzamidine hydrochloride

EXAMPLE 4A 2-Ethoxybenzamidine hydrochloride

21.4 g (400 mmol) of ammonium chloride are suspended in 375 ml of toluene, and the suspension is cooled to 0° C. 200 ml of a 2M solution of trimethylaluminium in hexane are added dropwise, and the mixture is stirred at room temperature until the evolution of gas has ceased. After addition of 29.44 g (200 mmol) of 2-ethoxybenzonitrile, the reaction mixture is stirred at 80° C. (bath) overnight.

With ice-cooling, the cooled reaction mixture is added to a suspension of 100 g of silica gel and 950 ml of chloroform, and the mixture is stirred at room temperature for 30 minutes. The mixture is filtered off with suction, and the filter residue is washed with the same amount of methanol. The mother liquor is concentrated, the resulting residue is stirred with a mixture of dichloromethane and methanol (9:1), the solid is filtered off with suction and the mother liquor is concentrated. This gives 30.4 g (76%) of a colourless solid.

200 MHz ¹H-NMR (DMSO-d6): 1.36, t, 3H; 4.12, quart., 2H; 7.10, t, 1H; 7.21, d, 1H; 7.52, m, 2H; 9.30, s, broad, 4H.

EXAMPLE 10A 2-(2-Ethoxy-phenyl)-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one

7.16 g (45 mmol) of 2-butyrylamino-propionic acid and 10.67 g of pyridine are dissolved in 45 ml of THF and, after addition of a spatula tip of DMAP, heated to reflux. 12.29 g (90 mmol) of ethyl oxalyl chloride are slowly added dropwise, and the reaction mixture is refluxed for 3 hours. The mixture is poured into ice-water and extracted three times with ethyl acetate and the organic phase is dried over sodium sulphate and concentrated using a rotary evaporator. The residue is taken up in 15 ml of ethanol and refluxed with 2.15 g of sodium bicarbonate for 2.5 hours. The cooled solution is filtered.

With ice-cooling, 2.25 g (45 mmol) of hydrazine hydrate are added dropwise to a solution of 9.03 g (45 mmol) of 2-ethoxybenzamidine hydrochloride in 45 ml of ethanol, and the resulting suspension is stirred at room temperature for another 10 minutes. The ethanolic solution described above is added to this reaction mixture, and the mixture is stirred at a bath temperature of 70° C. for 4 hours. After filtration, the mixture is concentrated, the residue is partitioned between dichloromethane and water, the organic phase is dried over sodium sulphate and the solvent is removed under reduced pressure.

This residue is dissolved in 60 ml of 1,2-dichloroethane and, after addition of 7.5 ml of phosphorus oxychloride, refluxed for 2 hours. The mixture is diluted with dichloromethane and neutralized by addition of sodium bicarbonate solution and solid sodium bicarbonate. The organic phase is dried and the solvent is removed under reduced pressure. Chromatography using ethyl acetate and crystallization afford 4.00 g (28%) of a colourless solid, R_f=0.42 (dichloromethane/methanol=95:5)

200 MHz ¹H-NMR (CDCl₃): 1.02, t, 3H; 1.56, t, 3H; 1.89, hex, 2H; 2.67, s, 3H; 3.00, t, 2H; 4.26, quart., 2H; 7.05, m, 2H; 7.50, dt, 1H; 8.17, dd, 1H; 10.00, s, 1H.

EXAMPLE 15A 4-Ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydro-imidazo[5,1-f][1,2,4]triazin-2-yl)-benzenesulphonyl chloride

At 0° C., 2.00 g (6.4 mmol) of 2-(2-ethoxy-phenyl)-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one are slowly added to 3.83 ml of chlorosulphonic acid. At room temperature, the reaction mixture is stirred ovemight, and then poured into ice-water and extracted with dichloromethane. This gives 2.40 g (91%) of a colourless foam.

200 MHz ¹H-NMR (CDCl₃): 1.03, t, 3H; 1.61, t, 2H; 1.92, hex, 2H; 2.67, s, 3H; 3.10, t, 2H; 4.42, quart., 2H; 7.27, t, 1H; 8.20, dd, 1H; 8.67, d, 1H; 10.18, s, 1H.

Example 19 2-[2-Ethoxy-5-(4-ethyl-piperazine-1-sulphonyl)-phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one

470 mg (1.14 mmol) of 4-ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydro-imidazo[5,1-f][1,2,4]triazin-2-yl)-benzenesulphonyl chloride are dissolved in 20 ml of dichloromethane and cooled to 0° C. 390 mg (3.42 mmol) of N-ethylpiperazine are added, and the reaction mixture is stirred at room temperature overnight. The mixture is diluted with dichloromethane, the organic phase is washed twice with water and dried over sodium sulphate and the solvent is removed under reduced pressure. Crystallization from ether gives 370 mg (66%) of a colourless solid.

400 MHz ¹H-NMR (CDCl₃): 1.01, t, 3H; 1.59, t, 3H; 1.88, hex, 2H; 2.42, quart., 2H; 2.56, m, 4H; 2.63, s, 3H; 3.00, t, 2H; 3.10, m, 4H; 4.33, quart., 2H, 7.17, d, 1H; 7.88, dd, 1H; 8.44, d, 1H; 9.75, s, 1H.

…………………….

US7977478

EXAMPLE 7 Preparation of the Trihydrate of Vardenafil Monohydrochloride

14 g of vardenafil hydrochloride was taken into a round bottom flask followed by the addition of 70 ml water and the pH of the reaction mass was adjusted using sodium hydroxide to 11 at 30° C. 280 ml of dichloromethane was added to the above reaction mass and the layers were separated. The organic layer was dried over sodium sulfate and the organic layer was transferred into a round bottom flask and subjected to heating for distillation at 40° C. for 1.5 hours. The solid material was transferred into a round bottom flask and 36 ml of a mixture of acetone and water in 12:1 ratio was added with stirring, then 2.2 ml of 36% aqueous hydrochloric acid was added with stirring. The reaction mass was heated to a temperature of about 45° C. and the undissolved particles were removed by filtration. The filtrate was taken into a round bottom flask and cooled to 5° C., maintained for 45 minutes at 3 to 5° C. followed by the filtration of the solid which was then subjected to suction drying and finally dried at 40° C. to yield 9.0 g of the trihydrate of vardenafil monohydrochloride.

……………………..

US20050203298

STARTING COMPOUNDS

Example I Preparation of 2-(2-ethoxyphenyl)-5-methyl-7-propyl-3H-imidazo-[5,1-f][2,4]triazin-4-oneIa) Preparation of 2-butyrylaminopropionic acid

A solution of 100 kg of D,L-alanine in aqueous sodium hydroxide solution is reacted in the cold with 119 kg of butyryl chloride. After addition of butyl acetate, the mixture is acidified with hydrochloric acid, the organic phase is separated off and the aqueous phase is re-extracted. The organic phase is dried by azeotropic distillation. The crystallizate is isolated, washed with butyl acetate and dried.

Yield: 132.6 kg (68%)

¹H-NMR: δ=0.8 (t, 3H), 1.25 (d, 3H), 1.5 (m, 2H), 2.1 (t, 2H), 4.2 (q, 1H), 8.1 (d, NH), 12.0-12.7 (s, COOH)

MS: 336 (2M+NH₄, 40), 319 (2M+H, 15), 177 (M+NH₄, 100), 160 (M+H, 20)

Ib) Preparation of 2-ethoxybenzonitrile

260 kg of thionyl chloride are added at 85-95° C. to a suspension of 250 kg of 2-ethoxybenzamide in toluene under metering control. The reaction mixture is stirred in the presence of heat. Thionyl chloride and toluene are then distilled off in vacuo. The product is employed in the subsequent stage as a crude product.

Yield: 228.5 kg (crude product)

¹H-NMR: δ=1.45 (t, 3H), 4.15 (q, 2H), 7.0 (m, 2H, phenyl), 7.5 (m, 2H, phenyl)

MS: 312 (2M+N₄, 35), 165 (M+NH₄, 100), 147 (5)

Ic) Preparation of 2-ethoxy-N-hydroxybenzamidine

111 kg of 2-ethoxybenzonitrile (crude product) from Example Ib are heated under reflux with 164 1 of triethylamine and 73 kg of hydroxylamine hydrochloride in isopropanol. The reaction mixture is treated with water and cooled. The crystallizate is isolated, washed and employed in the subsequent stage as a moist product.

Yield: 92.6 kg (moist product)

¹H-NMR: δ=1.35 (t, 3H), 4.1 (q, 2H), 5.6 (s, 2H), 6.9-7.4 (4H, phenyl), 9.4 (s, 1H, OH)

MS: 361 (2M+H, 30), 198 (M+N, 30), 181 (M+H, 100)

Id) Preparation of 2-ethoxybenzamidine hydrochloride

135 kg of 2-ethoxy-N-hydroxybenzamidine (moist product) from Example Ic are hydrogenated at 50-60° C. in acetic acid using palladium on carbon as a catalyst. For the work-up, the hydrogenation reaction is freed from the catalyst, treated with hydrochloric acid and concentrated. Residual acetic acid and water are removed by azeotropic distillation with toluene. The crystallizate is isolated and dried in vacuo.

Yield: 136.4 kg

H-NMR: 1.35 (t, 3H), 4.15 (q, 2H), 7.1-7.7 (m, 4H, phenyl), 9.1-9.4 (2×s, 3H), 10.5-10.7 (s, 1H)

MS: 329 (2M+H, 10), 165 (M+H, 100)

Ie) Preparation of 2-(2-ethoxyphenyl)-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]-triazin-4-one

231 kg of 2-butyrylaminopropionic acid from Example Ia are treated in tetrahydrofuran with 341 kg of pyridine, catalytic amounts of 4-N,N-dimethylaminopyridine and 392 kg of ethyl chloroxalate and stirred with heating under reflux. The reaction mixture is taken up in ethyl acetate, washed with water and the ethyl acetate phase is concentrated. The distillation residue is taken up in methanol and reacted with the following solution.

192 kg of 2-ethoxybenzamidine hydrochloride from Example Id are treated in methanol with 47.5 kg of hydrazine hydrate and the mixture is stirred at room temperature. The solution is combined with the solution of 2-butyrylamino-1-ethoxycarbonylpropenyl ethyl oxalate prepared above. The reaction mixture thus obtained is stirred with heating under reflux. Methanol is removed by distillation and replaced by acetic acid.

Option A:

138.6 kg of phosphorus oxychloride are added and stirred in the presence of heat.

Acetic acid is distilled off in vacuo. The residue is treated with water and dichloromethane or optionally methyl isobutyl ketone and rendered neutral using sodium hydroxide solution. The organic phase is concentrated, and the residue is dissolved in acetone and crystallized with cooling. The crystallizate is isolated, washed and dried.

Option B:

At least 190 kg of acetyl chloride are added and stirred in the presence of heat. Acetic acid is distilled off in vacuo. The distillation residue is treated with acetone and water, and the product is crystallized by rendering neutral with sodium hydroxide solution. The product is isolated, washed and dried.

Yield: 90-160 kg

¹H-NMR: δ=1.0 (t, 3H), 1.6 (t, 3H), 1.9 (m, 2H), 2.8 (s, 3H), 3.3 (t, 2H), 4.3 (q, 2H), 7.0-8.2 (Ar, 4H), 10.3 (CONH, 1H)

MS: 313 (M+H, 100), 149 (25), 151 (40), 121 (15)

HPLC: Kromasil C-18 phase, neutral phosphate buffer, acetonitrile, 233 nm, linear gradient of 30% acetonitrile ->80% acetonitrile (30 min.): 99 area % (R_t19.1)

PREPARATION EXAMPLES Example 1a 4-ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydroimidazo[5,1-fl-][1,2,4]triazin-2-yl)benzenesulphonic acid

194 kg of 2-(2-ethoxyphenyl)-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one from Example Ie are reacted with 504 kg of concentrated sulphuric acid. The reaction mixture is added to water, cooled, and the crystallizate is isolated and dried in vacuo.

Yield: 195.2 kg

¹H-NMR: δ=0.95 (t, 3H), 1.3 (t, 3H), 1.8 (m, 2H), 2.6 (s, 3H), 3.05 (t, 2H), 4.1 (q, 2H), 7.15 (Ar, 1H), 7.75 (m, 2H), 12.3 (SO₂OH)

MS: 393 (M+H, 100), 365 (25), 151 (40)

HPLC: X-Terra C-18 phase, aqueous phosphoric acid, acetonitrile, 242 nm, linear gradient of 10% acetonitrile ->90% acetonitrile (20 min.):

98 area % (R, 9.2)

Example 1b) 2-[2-ethoxy-5-(4-ethlylpiperazin-1-sulphonyl)phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one

22.5 kg of 4-ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydro-imidazo[5,1-f][1,2,4]-triazin-2-yl)benzenesulphonic acid from Example 1a are reacted with 74 kg of thionyl chloride and catalytic amounts of dimethylformamide until the evolution of gas has ended. Xylene is repeatedly added to the reaction mixture and thionyl chloride is distilled off. 15.1 kg of N-ethylpiperazine are added to the suspension and it is stirred. After the addition of water, it is adjusted to pH 1 using hydrochloric acid, and the phases are separated. The aqueous phase is treated with acetone and rendered neutral by addition of sodium hydroxide solution. The mixture is cooled, and the crystallizate is isolated, washed and dried in vacuo.

Yield: 26.1 kg

¹H-NMR: δ=1.0 (2×t, 6H), 1.6 (t, 3H), 1.9 (m, 2H), 2.45 (q, 2H), 2.55 (m, 4H), 2.65 (s, 3H), 3.0 (t, 2H), 3.1 (m, 4H), 4.35 (q, 2H), 7.15 (Ar, 1H), 7.9 (Ar, 1H), 8.4 (Ar, 1H), 9.8 (CONH)

MS: 489 (M+H, 100), 345 (10), 313, (10), 285 (10), 113 (20)

HPLC: X-Terra C-18 phase, neutral phosphate buffer, acetonitrile, 242 nm, linear gradient of 20% acetonitrile ->75% acetonitrile (20 min.): 98 area % (R_t16.3)

1 c) 2-[2-ethoxy-5-(4-ethylpiperazin-1-sulphonyl)phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-fl][1,2,4]triazin-4-one hydrochloride trihydrate

22.5 kg of 2-[2-ethoxy-5-(4-ethylpiperazin-1-sulphonyl)phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one from Example 1b are dissolved in 5.1 kg of concentrated hydrochloric acid and acetone/water (12:1 v/v) in the presence of heat. The clear solution is filtered hot and crystallized by cooling and seeding. The crystallizate is isolated, washed and dried in vacuo at about 30° C. and about 300 mbar.

Yield: 25.4 kg

M.p. (DSC): 192° C.

HPLC: X-Terra C-18 phase, neutral phosphate buffer, acetonitrile, 242 nm, linear gradient of 20% acetonitrile ->75% acetonitrile (20 min.): 99 area % (R_t16.3)

http://www.pharmpro.com/News/Feeds/2010/06/pharmaceutical-companies-bayer-new-erectile-dysfunction-treatment-staxyn-approve/
http://www.newswire.ca/en/story/832217/staxyn-new-innovation-in-erectile-dysfunction-helps-younger-men-rise-to-the-occasion
A Aversa et al. “Effects of vardenafil administration on intravaginal ejaculatory latency time in men with lifelong premature ejaculation”. Retrieved 2010-12-14.
Schools of Pharmacy (Glen L. Stimmel, Pharm.D., and Mary A. Gutierrez, Pharm.D.) and Medicine (Glen L. Stimmel, Pharm.D.), University of Southern California, Los Angeles, California. “Counseling Patients About Sexual Issues: Drug-Induced Priapism”. Medscape. Retrieved 2010-12-06.
“FDA Announces Revisions to Labels for Cialis, Levitra and Viagra”. Food and Drug Administration. 2007-10-18. Retrieved 2009-08-06.

Official Levitra website
PubChem Information

23313637

2-1-2013

Synthesis of quinoline derivatives: discovery of a potent and selective phosphodiesterase 5 inhibitor for the treatment of Alzheimer’s disease.

European journal of medicinal chemistry

PATENTS

US6362178 *	Oct 31, 1998	Mar 26, 2002	Bayer Aktiengesellschaft	2-phenyl substituted imidazotriazinones as phosphodiesterase inhibitors
US20050203298 *	May 5, 2005	Sep 15, 2005	Bayer Healthcare Aktiengesellschaft	Process for the preparation of sulphonamide-substituted imidazotriazinones
US20060111354 *	Jul 3, 2003	May 25, 2006	Peter Serno	Medicaments containing vardenafil hydrochloride trihydrate
WO2004006894A1 *	Jul 3, 2003	Jan 22, 2004	Bayer Healthcare Ag	Medicaments containing vardenafil hydrochloride trihydrate

US2011269750	11-4-2011	ROFLUMILAST FOR THE TREATMENT OF DIABETES MELLITUS
US8017633	9-14-2011	Roflumilast for the Treatment of Diabetes Mellitus
US2011190495	8-5-2011	N-BUTYRAMIDE, THE PREPARATION METHOD AND USE THEREOF
US2011048980	3-4-2011	Fatty Acid Oxidation Inhibitors Treating Hyperglycemia and Related Disorders
US2011009367	1-14-2011	2-PHENYL SUBSTITUTED IMIDAZOTRIAZINONES AS PHOSPHODIESTERASE INHIBITORS
US2010234388	9-17-2010	SUBSTITUTED PDE5 INHIBITORS
US2010179131	7-16-2010	Combination treatment for diabetes mellitus
US7704999	4-28-2010	2-Phenyl substituted imidazotriazinones as phosphodiesterase inhibitors
US7696206	4-14-2010	2-PHENYL SUBSTITUTED IMIDAZOTRIAZINONES AS PHOSPHODIESTERASE INHIBITORS
US2010029671	2-5-2010	Heterocyclic Compounds And Uses Thereof In The Treatment Of Sexual Disorders


US2009318459	12-25-2009	Therapeutic Compositions Comprising a Specific Endothelin Receptor Antagonist and a PDE5 Inhibitor
US2009291958	11-27-2009	Substituted PDE5 inhibitors
US2009221570	9-4-2009	Uses of 2-Phenyl-Substituted Imidazotriazinone Derivatives for Treating Pulmonary Hypertension
US2009215836	8-28-2009	Roflumilast for the Treatment of Pulmonary Hypertension
US2009196900	8-7-2009	Use of Phosphodiesterase Inhibitor as a Component of Implantable Medical Devices
US2009163504	6-26-2009	Method for healing a wound using a phosphodiesterase type five inhibitor
US2009074796	3-20-2009	Pde5 inhibitor compositions and methods for immunotherapy
US2009062313	3-6-2009	Pde5 inhibitor compositions and methods for treating cardiac indications
US2008268046	10-31-2008	Formulations with Controlled Release of Active Ingredient
US2008194529	8-15-2008	HIGHLY SELECTIVE and LONG-ACTING PDE5 MODULATORS

US2008187588	8-8-2008	Formulations With Controlled Release Of Active Ingredient
US2008085897	4-11-2008	Use of 2-alkoxyphenyl-substituted imidazotriazinones
US7314871	1-2-2008	2-phenyl substituted imidazotriazinones as phosphodiesterase inhibitors, for treatment of hypertension
US2007299088	12-28-2007	Novel Uses of 2-Phenyl-Substituted Imidazotriazinone Derivatives
US7276504	10-3-2007	Use of 2-alkoxyphenyl-substituted imidazotriazinones
US2006264624	11-24-2006	Methods for synthesizing imidazotriazinones
US7122540	10-18-2006	2-Phenyl substituted imidazotriazinones as phosphodiesterase inhibitors
US6998483	2-15-2006	Process for the preparation of sulphonamide-substituted imidazotriazinones
US6930108	8-17-2005	Use of 2-alkoxyphenol-substituted imidazotriazinones
US6890922	5-11-2005	2-phenyl substituted imidazotriazinones as phosphodiesterase inhibitors

US2005014756	1-21-2005	Process for the preparation of sulphonamide-substituted imidazotriazinones
US6777551	8-18-2004	Process for the preparation of sulphonamide-substituted imidazotriazinones
US2004152700	8-6-2004	Novel use of 2-phenyl-substituted imidazotriazinones
US2003144296	7-32-2003	Daily treatment for erectile dysfunction using a PDE5 inhibitor
US6566360	5-21-2003	2-phenyl substituted imidatriazinones as phosphodiesterase inhibitors
US6362178	3-27-2002	2-phenyl substituted imidazotriazinones as phosphodiesterase inhibitors
US2001053780	12-21-2001	Daily treatment for erectile dysfunction using a PDE5 inhibitor
WO9924433	5-21-1999	2-PHENYL SUBSTITUTED IMIDAZOTRIAZINONES AS PHOSPHODIESTERASE INHIBITORS

////////////

Lodenafil Carbonate … an Erectile Dysfunction Drug in Phase III

Phase 3 drug, Uncategorized 1 Response »

Jan 312014

Lodenafil carbonate

UNII-29X84F932D, CRIS-031

bis-(2-{4-[4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-benzenesulfonyl]piperazin-1-yl}-ethyl)carbonate

5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one. IS THE NAME OF MONOMER

398507-55-6 CAS

Cristalia (Originator)

C47 H62 N12 O11 S2= MF
Molecular Weight	1035.199

Lodenafil is a drug belonging to a class of drugs called PDE5 inhibitor, which many other erectile dysfunction drugs such as sildenafil, tadalafil, and vardenafil also belong to. Like udenafil and avanafil it belongs to a new generation of PDE5 inhibitors.

Sildenafil, tadalafil, vardenafil, and the newer udenafil and avanafil selectively inhibit PDE5, which is cGMP-specific and responsible for the degradation of cGMP in the corpus cavernosum. These phosphodiesterase inhibitors are used primarily as remedies for erectile dysfunction, as well as having some other medical applications such as treatment of pulmonary hypertension.

Lodenafil is formulated as a dimer, lodenafil carbonate, which breaks down in the body to form two molecules of the active drug lodenafil. This formulation has higher oral bioavailability than the parent drug.^[1]

It is manufactured by Cristália Produtos Químicos e Farmacêuticos in Brazil and sold there under the brand-name Helleva.^[2]

Helleva (Lodenafil Carbonate) - 80mg (4 Tablets)

Helleva (Lodenafil Carbonate) is an oral PDE5 inhibitor prescribed to treat men suffering from erectile dysfunction. It operates by relaxing muscles and dilating blood vessels in the penis to increase circulation making it easier to attain and maintain an erection.

It has undergone Phase III clinical trials,^[3]^[4]^[5] but is not yet approved for use in the United States by the U.S. Food and Drug Administration.

lodenafil

………..

SYNTHESIS

WO 2002012241 OR US7148350

MONOMER synthesis

PIPERAZINE

AND

ETHYL CHLORO ACETATE

WILL GIVE

Ethyl 1-piperazinylacetate ChemSpider 2D Image | Ethyl 1-piperazinylacetate | C8H16N2O2

SEE RXN 1 BELOW

Reaction 1:

Synthesis of Piperazine Ethyl Acetate

To a reaction blend containing 100 g (3 Eq, 0.515 mol, MW=194) of piperazine, 26.3 mL (1.1 Eq, 0.189 mol, MW=101, d=0.726) of triethylamine in 200 mL of isopropanol, add to a solution previously prepared of 18.4 mL (1 Eq., 0.172 mol, MW=122.55, d=1.15) of chloroacetate of ethyl in 140 mL of isopropanol under stirring, at room temperature. Keep the reaction medium under stirring, monitoring the reaction termination by means of a chromatography of the thin layer (about 2–3 hours). Add a solution of 40.6 g (0.344 mol) of succinic acid in 140 mL of isopropanol. Keep the system under stirring for about 30 minutes to assure total precipitation of the succinate salt of piperazine formed. Filter this salt and concentrate the filtrate containing the mono and dialkyled derivatives. We obtain a slightly yellowish oil, which is used in later phases without purification.

Mass obtained=33 g

GC/MS: Monoalkylated derivative 72%, and dialkylated 22%.

ChemSpider 2D Image | Ethyl 1-piperazinylacetate | C8H16N2O2 Piperazine Ethyl Acetate

AND

5-(5-Chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one Structure

5-(5-chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one

WILL REACT TO GIVE… 5-{2-ethoxy-5-[(4-ethyl acetate 1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-di-hydro-7H-pyrazole[4,3-d]pyrimidin-7-one AS IN RXN 4 BELOW

Reaction 4:

Synthesis of 5-{2-ethoxy-5-[(4-ethyl acetate 1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-di-hydro-7H-pyrazole[4,3-d]pyrimidin-7-one.

Suspend 24.6 g (60 mmol, MW=410.9) of 5-(5-chlorosulfonyl-2-etoxyphenyl)-1-methyl-3n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one in 900 mL of ethanol absolute. Under stirring and at room temperature, add at only one time, a solution containing 31.0 g (3 Eq., 180 mmol MW=172) of N-piperazine ethyl acetate (Reaction 1) dissolved in 150 mL of ethanol absolute. In an interval of 2–10 minutes, all solid is consumed, forming a clean and homogeneous solution, and after that starts the precipitation of the expected product. At the end of the reaction, which lasts 2–3 hours (monitored by chromatography of thin layer), the product is vacuum filtered and the solid is washed with two portions of 50 mL of iced absolute ethanol. 29 g are obtained (yielding=89%) from the product as a white solid of MP=165.5–166.5° C.

Reaction 7:

Intermediate 1

5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one. IS MONOMER

please note during LAH redn …………. the PIP CH2-C=O-O CH2 CH3 BECOMES PIP-CH2CH2-OH

To a suspension of lithium aluminum hydride (0.74 g 2.2 Eq. MW=37.9) in 25 mL of THF, slowly add, under stirring and at room temperature, a suspension of 5.0 g (9.1 mmol, MW=546.6) of 5-{2-ethoxy-5-[(4-ethyl acetate 1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-di-hydro-7H-pyrazole[4,3-d]pyrimidin-7-one in 50 mL of THF. The system is maintained under stirring, monitoring the consumption of the product by chromatography of thin layer, until the complete consumption of the starting reagent (about 5–6 hours). Slowly add water to the reaction medium and, when there is no longer release of H₂, add HCl 1M regulating pH for 7. Extract the product with 3 200 mL-portions of chloroform, dry with anhydrous sodium sulfate and vacuum concentrate the product. It is obtained 3.8 g of the product as a cream solid MP=183–187° C. yielding 83%. The same was crystallized from methanol and DMF yielding a slightly yellowish solid with melting point at 189–192° C.

note …………. the PIP CH2-C=O-O CH2 CH3 BECOMES PIP-CH2CH2-OH

HOMODIMER CARBONATE

EXAMPLE 1B

Homodimer Carbonate of Intermediate 1—Alternative Method

A phosgene solution (3.5 g, 35 mmol) dissolved in 20 mL of toluene was added dropwise to a solution of 2.02 g (4 mmol) of 5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one, suspended in 44 mL of toluene. The reaction mixture resulting is stirred and followed by chromatography analysis of thin layer every hour until the reagent conversion in its chloroformate was completed. When the analysis indicates the complete consumption of 5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one, the volatile compounds of the reaction are vacuum removed (solvents and phosgene), yielding the esther chloroformate raw derivative of 5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one.

The raw chloroformate obtained above (4.0 mmol, 2.27 g) is dissolved in about 30 mL of dichloromethane, to which is added 2.07 g (4.1 mmol) of 5-{2-ethoxy-5-[(4-hydroxyethyl-1-piperazinyl)sulfonyl]phenyl}-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one, followed by the addition of 4 mL of dichloromethane containing 450 mg of triethylamine. The reaction mixture is maintained under stirring, being followed by chromatography of thin layer every hour until this indicates the end of the reaction (disappearing of chloroformate derivative). The reaction mixture is then diluted with 60 mL of dichloromethane, washed with NaCl saturated solution, after with sodium bicarbonate saturated solution and again with NaCl saturated solution. Organic phase is separated and dry with anhydrous sodium sulfate. The solvent is then evaporated to dry, yielding the dimer carbonate as a slightly yellowish solid.

This compound is re-crystallized from ethanol:DMF, yielding a pale white solid. Yielding m=3.2 g (76%)

Microanalysis: Theoretical C, (54.53%); H, (6.04%); N, (16.24%);

Obtained C, (54.45%); H, (6.02%); N, (16.17%).

INFO ABOUT INTERMEDIATE

5-(5-Chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one Structure

5-(5-chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3n-propyl-1,6-dihydro-7H-pyrazole[4,3-d]pyrimidin-7-one

CAS No.	139756-22-2
Chemical Name:	5-(5-Chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one
Synonyms:	Sildenafil Chlorosulfone IMpurity;Sildenafil Chlorosulfonyl IMpurity;5-(5-CHLOROSULFONYL-2-ETHOXY PHENYL)-1-METHYL-3-N-PROPYL-1;3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1 H-pyrazolo-(4-3-d)-pyrimidine-5;5-(5-Chlorosulfonyl-2-ethoxyphenyl)-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one;3-(4,7-Dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxy-benzenesulfonyl Chloride;4-Ethoxy-3-(1-Methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyriMidin-5-yl)benzene-1-sulfonyl chloride
CBNumber:	CB11175931
Molecular Formula:	C17H19ClN4O4S

http://www.chemicalbook.com/ChemicalProductProperty_EN_CB11175931.htm

…………..

SYNTHESIS OF

http://www.google.co.in/patents/US6362178

2-butyrylamino-propionic acid

EXAMPLE 1A 2-Butyrylaminopropionic acid

200 MHz ¹H-NMR (DMSO-d6): 0.84, t, 3H; 1.22, d, 3H; 1.50, hex, 2H; 2.07, t, 2H; 4.20, quin., 1H; 8.09, d, 1H.

EXAMPLE 3A 2-Ethoxybenzonitrile

200 MHz ¹H-NMR (DMSO-d6): 1.48, t, 3H; 4.15, quart., 2H; 6.99, dt, 2H; 7.51, dt, 2H.

2-ethoxybenzamidine hydrochloride

EXAMPLE 4A 2-Ethoxybenzamidine hydrochloride

200 MHz ¹H-NMR (DMSO-d6): 1.36, t, 3H; 4.12, quart., 2H; 7.10, t, 1H; 7.21, d, 1H; 7.52, m, 2H; 9.30, s, broad, 4H.

EXAMPLE 10A 2-(2-Ethoxy-phenyl)-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one

200 MHz ¹H-NMR (CDCl₃): 1.02, t, 3H; 1.56, t, 3H; 1.89, hex, 2H; 2.67, s, 3H; 3.00, t, 2H; 4.26, quart., 2H; 7.05, m, 2H; 7.50, dt, 1H; 8.17, dd, 1H; 10.00, s, 1H.

EXAMPLE 15A 4-Ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydro-imidazo[5,1-f][1,2,4]triazin-2-yl)-benzenesulphonyl chloride

200 MHz ¹H-NMR (CDCl₃): 1.03, t, 3H; 1.61, t, 2H; 1.92, hex, 2H; 2.67, s, 3H; 3.10, t, 2H; 4.42, quart., 2H; 7.27, t, 1H; 8.20, dd, 1H; 8.67, d, 1H; 10.18, s, 1H.

Example 22 2-[2-Ethoxy-5-(4-hydroxyethyl-1-amino-piperazine-1-sulphonyl)-phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one

By the same method, starting with 0.04 g (0.097 mmol) of 4-ethoxy-3-(5-methyl-4-oxo-7-propyl-3,4-dihydro-imidazo[5,1-f][1,2,4]triazin-2-yl)-benzenesulphonyl chloride and 0.04 g (0.29 mmol) of 1-amino-4-hydroxyethylpiperazine, 46 mg (91%) of 2-[2-ethoxy-5-(4-hydroxyethyl-1-amino-piperazine-1-sulphonyl)-phenyl]-5-methyl-7-propyl-3H-imidazo[5,1-f][1,2,4]triazin-4-one are obtained.

R_f=0.08 (dichloromethane/methanol=19:1)

200 MHz ¹H-NMR (CDCl₃): 1.02, t, 3H; 1.59, t, 3H; 1.90, sex., 2H; 2.49, m, 6H; 2.62, s, 3H; 2.71, m, 4H; 3.00, t, 2H; 3.55, t, 2H; 4.31, quart., 2H; 7.14, d, 1H; 8.05, dd, 1H; 8.60, d, 1H.

…………..

Methods of analysis

The development of lodenafil carbonate was reported by Toque et al. (2008). They observed the effects of lodenafil carbonate on rabbit and human corpus cavernosum relaxation, activity of PDE5 in human platelets, stability and metabolic studies in comparison with sildenafil and lodenafil, as well as the pharmacological evaluation of lodenafil carbonate after intravenous and oral administration in male beagles.

The determination of PDE activity, stability of lodenafil carbonate in human, dog and rat plasma and the pharmacokinetic parameters after a single intravenous or oral dose was carried out by LC-MS/MS analysis

Codevilla et al. (2011a) developed a stability-indicating reversed-phase liquid chromatography method using ultraviolet (UV) detection for the quantitative determination of lodenafil carbonate in tablets. The method can be useful for routine quality control assay and stability studies.

Another study for the determination of lodenafil carbonate in tablets was developed by Codevilla et al. (2011b). As an alternative to the LC method the authors suggested a UV-spectrophotometric method for the analysis of lodenafil carbonate in pharmaceutical form. The UV method offers advantages over other analytical methods due to its rapidity, simplicity, and lower cost. Recently, Codevilla et al. (2012) developed and validated a capillary zone electrophoresis (CZE) method for determination of lodenafil carbonate in drug products. There are some advantages to use the CZE method, such as rapid analysis, small sample and reagent consumption, high separation efficiency (Furlanetto et al., 2001; Yang et al., 2010). The results obtained from the UV-spectrophotometric method and CZE method were compared statistically with the LC method (Codevilla et al., 2011a) and the results showed no significant difference between these methods.

References

Toque HA, Teixeira CE, Lorenzetti R, Okuyama CE, Antunes E, De Nucci G (September 2008). “Pharmacological characterization of a novel phosphodiesterase type 5 (PDE5) inhibitor lodenafil carbonate on human and rabbit corpus cavernosum”. European Journal of Pharmacology 591 (1–3): 189–95. doi:10.1016/j.ejphar.2008.06.055. PMID 18593576.
Cristália Product page. Retrieved on September 16, 2009.
ukmedix Lodenafil article. Retrieved on September 16, 2009.
Glina S, Toscano I, Gomatzky C, de Góes PM, Júnior AN, Claro JF, Pagani E (February 2009). “Efficacy and tolerability of lodenafil carbonate for oral therapy in erectile dysfunction: a phase II clinical trial”. The Journal of Sexual Medicine 6 (2): 553–7. doi:10.1111/j.1743-6109.2008.01079.x.PMID 19040623.
Glina S, Fonseca GN, Bertero EB, Damião R, Rocha LC, Jardim CR, Cairoli CE, Teloken C, Torres LO, Faria GE, da Silva MB, Pagani E (February 2010). “Efficacy and Tolerability of Lodenafil Carbonate for Oral Therapy of Erectile Dysfunction: A Phase III Clinical Trial”. The Journal of Sexual Medicine 7 (5): 1928–1936. doi:10.1111/j.1743-6109.2010.01711.x. PMID 20214718.
Toque H A et al., (2008) European Journal of Pharmacology, 591(1-3):189-95.
Exploring the role of PDE5 inhibition in the treatment of muscular dystrophy
Drugs Fut 2011, 36(4): 321

Prediction of Drug Degradation Pathways leading to Structural Alerts for Potential Genotoxic Impurities

regulatory, Uncategorized Comments Off

Jan 302014

An in-depth analysis of the web-based CambridgeSoft Pharmaceutical Drug Degradation Database, Pharma D3, was conducted in two phases in an attempt to generate some general rules for the prediction of alerting structures for genotoxicity that may arise as a result of degradation. The first phase involved interrogation of the database to determine the nature and frequency of alerting structures present in the degradants. This analysis revealed five functional groups, which account for approximately 70% of the alerting structures found in the degradants within the database: (1) aldehydes; (2) α,β unsaturated carbonyls; (3) aromatic amines, hydroxylamine and its derived esters; (4) epoxides; and (5) polyaromatic hydrocarbons. The second phase of the analysis involved categorizing the major chemical reactions responsible for the generation of the five most prevalent alerting structures. This two-step approach led, in turn, to a proposal for the prediction of functional groups that may have a propensity to degrade to alerting structures not necessarily present in the parent molecule.

Prediction of Drug Degradation Pathways leading to Structural Alerts for Potential Genotoxic Impurities

Stephen P. Raillard, Joel Bercu, Steven W. Baertschi and Christopher M. Riley

Org. Process Res. Dev., 2010, 14 (4), pp 1015–1020

Publication Date (Web): April 21, 2010 (Article)

DOI: 10.1021/op100007q

READ ALL AT

http://pubs.acs.org/doi/full/10.1021/op100007q

Dasantafil for Treatment of Erectile Dysfunction

phase 2, Uncategorized 2 Responses »

Jan 292014

Dasantafil

569351-91-3 CAS NO

405214-79-1 (racemate)

UNII-48P711MI2G, SCH 446132, D03657,

Molecular Formula: C₂₂H₂₈BrN₅O₅

Molecular Weight: 522.39222

Merck & Co. (Originator) IN PHASE 2

THERAPEUTIC CLAIM treatment of erectile dysfunction (phosphodiesterase (PDE) 5 isoenzyme inhibitor)

CHEMICAL NAMES

1H-purine-2,6-dione, 7-[(3-bromo-4-methoxyphenyl)methyl]-1-ethyl-3,7-dihydro-8-[[(1R,2R)-2-hydroxycyclopentyl]amino]-3-(2-hydroxyethyl)
7-(3-bromo-4-methoxybenzyl)-1-ethyl-8-[[(1R,2R)-2-hydroxycyclopentyl]amino]-3-(2-hydroxyethyl)-3,7-dihydro-1H-purine-2,6-dione

7-[(3-bromo-4-methoxyphenyl)methyl]-l-ethyl-8-[[(lR,2R)-2- hydroxycyclopentyl]amino]-3-(2-hydroxyethyl)purine-2,6-dione

Treatment of Erectile Dysfunction , Phosphodiesterase PDE5A Inhibitors

Dasantafil (SCH-446132) is a phosphodiesterase type 5 (PDE5) inhibitor which had been in early clinical development at Merck & Co. for the treatment of erectile dysfunction (ED); however, no recent development has been reported for this research. Phosphodiesterases regulate the tissue concentration of cyclic guanosine monophosphate (cGMP), which in turn triggers smooth muscle relaxation, allowing blood to flow into the penis and resulting in erection. PDE5 is the most abundant phosphodiesterase in the human corpus cavernosum, and as such its inhibition by dasantafil enhances erectile function by increasing the concentration of cGMP.

DASANTAFIL

PDE V inhibitor compounds and their use in treating a variety of physiological conditions are described in a number of patents {e.g., U.S. Pat. Nos. 5,409,934, 5,470,579, 5,939,419 and 5,393,755) and foreign publications (e.g., WO 93/23401 , WO 92/05176, WO 92/05175, and WO 99/24433).

Specific PDE V inhibitors have been found useful for specific indications. For example, the use of PDE V inhibitors for treating impotence has met with commercial success with the introduction of sildenafil citrate, vardenafil, and tadalafil (i.e., Viagra®, Levitra®, and Cialis®, respectively). The chemistry and use of Viagra®, including its mechanism of action in treating erectile dysfunction, are taught in EP 0 702 555 B1. Accordingly, it is an object of this invention to provide a method of using a PDE V inhibitor to treat a patient who has, or is at risk of, congestive heart failure, and/or other cardiovascular conditions.

Processes for preparing PDE V inhibitor compounds can be found in US

6,207,829, US 6,066,735, US 5,955,611 , US 5,939,419, US 5,393,755, US 5,409,934, US 5,470,579, US 5,250,534, WO 02/24698, WO 99/24433, WO 93/23401 , WO 92/05176, WO 92/05175, EP 740,668 and EP 702,555. One type of PDE V inhibitor compound contains a xanthine functionality in its structure. Xanthines can be prepared as described by Peter K. Bridson and Xiaodong Wang in 1 -Substituted Xanthines, Synthesis, 855 (July, 1995), which is incorporated herein by reference in its entirety. WO 02/24698, which is incorporated herein by reference in its entirety, teaches a class of xanthine PDE V inhibitor compounds useful for the treatment of impotence. A general process disclosed therein for preparing xanthine PDE V inhibitor compounds having the formula (I) follows:

(III) (I) (i) reacting a compound having the formula (III) with an alkyl halide in the presence of a base (introduction of R¹¹ or a protected form of R¹¹); (ii) (a) debenzylating and then (b) alkylating the compound resulting from step (i) with an alkyl halide, XCH₂R¹“; (iii) (a) deprotonating and then (b) halogenating the compound resulting from step (ii);

(iv) reacting the compound resulting from step (iii) with an amine having the formula R^lvNH₂; and (v) removing a protecting portion of Rⁿ, if present, on the compound resulting from step (iv) to form the compound having the formula (I). R¹, R”, R^m and R^lv correspond to R¹, R², R³ and R⁴, respectively, in WO02/24698, and are defined therein. WO 02/24698 (pages 44 and 68-73) also teaches a synthesis for the following xanthine compound (identified therein as Compound 13 or Compound 114 of Table II): 1-ethyl-3,7-dihydro-8-[(1 R,2R)- (hydroxycyclopentyl) amino]-3-(2-hydroxyethyl)-7-[(3-bromo-4- methoxyphenyl)methyl]-1 H-purine-2,6-dione:

Compound 13. It would be beneficial to provide an improved process for preparing polycyclic xanthine PDE V inhibitor compounds

………………….

Patent description

Links

WO2006055573A2

entry 129 is dasantafil

Figure imgf000050_0001

…………………

SYNTHESIS

Links

WO2002024698A1

Figure imgf000069_0001

14X^‘ _CHs ^{‘ B}” tX is Experimental Procedure: Compound 114 in Table II (13)

1 (20.0 g, 74.0 mmol) was dissolved in dimethylformamide (370 mL) under nitrogen and (2-bromoethoxy)-terf-butyldimethylsilane (31.8 mL, 148 mmol) was added dropwise. The reaction was stirred at room temperature for 115 hrs., then diluted with ethyl acetate and washed with water several times.

The organic mixture was dried over potassium carbonate, filtered and concentrated under vacuum. Purification via flash chromatography (30/70 ethyl acetate/hexanes) yielded 2 (28.1 g, 88%).

¹H NMR (400 MHz, CDCI₃): δ 7.52 (s, 1 H), 7.29-7.39 (m, 5H), 5.49 (s,

2H), 4.25 (t, 2H, J = 6.0 Hz), 4.07 (q, 2H, J = 7.2 Hz), 3.93 (t, 2H, J =

6.0 Hz), 1.24 (t, 3H, J = 7.2 Hz), 0.75 (s, 9H), 0.08 (s, 6H). HRMS: Calcd for C₂₂H₃₂N₄0₃Si (M+H): 429.2322. Found: 429.2329.

To a solution of 2 (2.10 g, 4.89 mmol) in methanol (375 mL) was added ammonium formate (4.64g, 73.6 mmol) and 20% palladium hydroxide on carbon (980 mg). The reaction was heated to reflux for 1.5 hrs., then cooled to room temperature, filtered and concentrated under vacuum. Purification via flash chromatography (50/50 ethyl acetate/hexanes) yielded 3 (1.26 g, 94%).

¹H NMR (400 MHz, CDCI₃): δ 7.82 (s, 1 H), 4.33 (t, 2H, J = 6.0 Hz), 4.16

(q, 2H, J = 7.2 Hz), 3.99 (t, 2H, J = 6.0 Hz), 1.29 (t, 3H, J = 7.2 Hz),

0.78 (s, 9H), 0.06 (s, 6H). HRMS: Calcd for Cι₅H₂₆N₄O₃Si (M+H): 339.1852. Found: 339.1864. To 3 (970 mg, 2.86 mmol) was added dimethylformamide (25 mL), 3- bromo-4-methoxybenzyl bromide 15 (1.62 g, 5.79 mmol), and potassium carbonate (800 mg, 5.79 mmol) under nitrogen. The reaction mixture was stirred at room temperature for 21 hrs., then diluted with ethyl acetate and washed with water several times. The organic mixture was dried over potassium carbonate, filtered and concentrated under vacuum. Purification by flash chromatography (30/70 ethyl acetate/hexanes) yielded 10 (1.55 g, 100%).

¹H NMR (400 MHz, CDCI₃): δ 7.52 (s, 1 H), 7.51 (d, 1 H, J = 2.4 Hz),

7.30 (dd 1 H, J = 2.0 Hz, J = 8.4 Hz), 6.87 (d, 1 H, J = 8.8 Hz), 5.40 (s,

2H), 4.25 (t, 2H, J = 6.0 Hz), 4.07 (q, 2H, J = 7.0 Hz), 3.93 (t, 2H, J =

6.0 Hz), 3.88 (s, 3H), 1.25 (t, 3H, J = 7.0 Hz), 0.75 (s, 9H), 0.08 (s, 6H).

HRMS: Calcd for C₂₃H₃₃BrN₄O₄Si (M+H): 537.1533. Found: 537.1540.

To solution of 10 (1.50 g, 2.80 mmol) in tetrahydrofuran (24 mL) under nitrogen at -78 °C (dry ice/acetone bath) was added lithium diisopropylamide (2M in THF/heptane, 2.2 mL, 4.33 mmol). After stirring for thirty minutes, 1 ,2- dibromotetrafluoroethane (0.69 mL, 5.77 mmol) was added dropwise over five minutes. The reaction was stirred for 1.25 hrs. at -78 °C then quenched with saturated aqueous sodium bicarbonate and warmed to room temperature.

The mixture was extracted with dichloromethane, dried over potassium carbonate, filtered and concentrated under vacuum. Purification via flash chromatography (30/70 ethyl acetate/hexanes) yielded 11 (600 mg, 34%). ¹H NMR (400 MHz, CDCI₃): δ 7.60 (d, 1 H, J = 2.4 Hz), 7.35 (dd, 1 H, J =

2.0 Hz, J = 8.4 Hz), 6.84 (d, 1 H, J = 8.4 Hz), 5.45 (s, 2H), 4.21 (t, 2H, J = 5.6 Hz), 4.07 (q, 2H, J = 6.8 Hz), 3.90 (t, 2H, J = 5.6 Hz), 3.87 (s, 3H), 1.24 (t, 3H, J = 6.8 Hz), 0.73 (s, 9H), 0.08 (s, 6H). HRMS: Calcd for C₂₃H₃₂Br₂N₄O₄Si (M+H): 615.0638. Found: 615.0633.

To 11 (1.89 g, 3.07 mmol) was added the amino alcohol hydrochloride salt (1.31 g, 12.27 mmol), diisopropylethylamine (15.4 mL), and 1-methyl-2- pyrrolidinone (15.4 mL). The reaction mixture was heated to 160 °C in a sealed tube for 13 hrs., then cooled to room temperature. Water was added, then the mixture was extracted with ethyl acetate and washed with water several times. The organic mixture was dried over potassium carbonate, filtered and concentrated under vacuum. Purification via flash chromatography (3/97 methanol/dichloromethane) yielded 12 (1.77 g, 90%).

¹H NMR (400 MHz, CDCI₃): δ 7.45 (d, 1 H, J = 2.0 Hz), 7.17 (dd, 1 H, J =

2.4 Hz, J = 8.6 Hz), 6.86 (d, 1 H, J = 8.4 Hz), 5.18-4.34 (m, 3H), 4.00- 4.23 (m, 5H), 3.86-3.98 (m, 6H), 3.69-3.79 (m, 1 H), 2.10-2.21 (m, 1 H), 1.99-2.10 (m, 1 H), 1.60-1.84 (m, 3H), 1.32-1.43 (m, 1 H), 1.24 (t, 3H, J = 7.2 Hz), 0.75 (s, 9H), 0.07 (d, 6H, J = 4.0 Hz). HRMS: Calcd for C₂₈H₄₃BrN₅θ₅Si (M+H): 636.2217. Found: 636.2207.

12 (1.77 g, 2.78 mmol) was dissolved in tetrahydrofuran (28 mL) under nitrogen and tetrabutylammonium fluoride (1M in THF, 28 mL) was added dropwise. The reaction was stirred at room temperature for 15 hrs., then diluted with dichloromethane and washed with water several times. The organic mixture was dried over potassium carbonate, filtered and concentrated under vacuum. Purification via flash chromatography (3/97 methanol/dichloromethane) yielded 13 (compound no. 114 in Table II) (760 mg, 52%).

DASANTAFIL

¹H NMR (400 MHz, CDCI₃):

δ 7.47 (d, 1 H, J = 2.0 Hz), 7.19 (dd, 1 H, J =2.0 Hz, J = 8.4 Hz), 6.88 (d, 1 H, J = 8.4 Hz), 5.25 (s, 2H), 5.09 (s, 1H), 4.21-4.27 (m, 3H), 4.06 (q, 2H, J = 7.0 Hz), 3.90-3.97 (m, 3H), 3.89 (s, 1 H), 3.74-3.82 (m, 1 H), 3.08 (s, 1 H), 2.12-2.22 (m, 1 H), 1.98-2.08 (m, 1 H), 1.60-1.86 (m, 3H), 1.33-1.43 (m, 1 H), 1.25 (t, 3H, J = 7.0 Hz),1.06-1.22 (m, 3H). HRMS: Calcd for C₂₂H₂₈BrN₅O₅ (M+H): 522.1352. Found: 522.1346.

2-Bromo-4-methyl anisole 14 (2.2 mL, 14.9 mmol) was dissolved in dichlomethane (30 mL) and N-bromosuccinimide (3.75 g, 16.4 mmol) was added followed by AIBN (26.0 mg). The reaction was heated to reflux for 19 hrs., then cooled to room temperature and the precipitate was filtered off. The filtrate was diluted with dichloromethane and washed with 0.5 M aqueous sodium bicarbonate, followed by water. The organic mixture was dried over sodium sulfate, filtered and concentrated under vacuum to yield 15 (4.16 g,

100%). The benzyl bromide was used as the crude material without further purification.

¹H NMR (400 MHz, CDCI₃): δ 7.59 (d, 1 H, J = 2.0 Hz), 7.30 (dd, 1 H, J =

2.4 Hz, J = 8.4 Hz), 6.85 (d, 1 H, J = 8.4 Hz), 4.37 (s, 2H), 3.90 (s, 3H).

General Synthesis of Compound No. 114 in Table II (13) a) Reacting 1 with an alkyl halide and base to form 2; b) Debenzylation of 2 to form 3; c) Alkylation of 3 with a benzyl halide to form 10; d) Deprotonation of 10 followed. by addition of a brominating agent to form 11 ; e) Displacement of bromo 11 with an amine to form 12; and f) Silyl ether cleavage of 12 to form compound no. 114 in Table II (13).

114 IN TABLE II./(13)

Figure imgf000045_0001

……………

WO2003101992A1

GENERAL SCHEME

Figure imgf000018_0001

SYNTHESIOS

Figure imgf000027_0001

9A 13A DASANTAFIL

SYNTHESIS

Compound 1A:

glycine-A/-r(4-methoxyphenyl)methyl1 ethyl ester

To a mixture of glycine ethyl ester hydrochloride (about 1.4 equiv) and potassium carbonate (about 1.0 equiv) was added anhydrous ethanol. The mixture

was stirred at about 40-45 °C for about 3 hours. Then, p-anisaldehyde (about 1.0

equiv.) was added, and the reaction mixture was stirred for a minimum of about 3 hours to provide an imine (not shown). Upon reaction completion (about <5.0 % p- anisaldehyde remaining by GC analysis), the reaction mixture was cooled to about 0-

10 °C. Then, an aqueous solution of sodium borohydride (about 0.50 equiv) was

added to the reaction mixture at a temperature of between about 0 °C and about 20

°C, and stirred for about 1 hour to provide Compound 1 A. Upon completion of the

reduction reaction, the reaction mixture was quenched with the slow addition of an aqueous solution of aqueous glacial acetic acid. After quenching, the reaction mixture was warmed to room temperature and filtered to remove solids. The filtrate was then concentrated under vacuum, followed by the addition of toluene and water to facilitate layer separation. Aqueous potassium carbonate solution was added to adjust the pH of the mixture to about 8-9. The organic layer was separated and the aqueous layer was extracted with toluene. The combined toluene extracts were concentrated to provide the product in about a 80-85% yield (based on GC and HPLC in solution assay). ¹H NMR 400 MHz (CDCI₃): δ 7.23 (d, J = 8.5 Hz, 2H), 6.85 (d, J = 8.5 Hz, 2H),

4.17 (q, J = 7.1 Hz, 2H), 3.78 (s, 3H), 3.73 (s, 2H), 3.38 (s, 2H), 1.88 (s, br, 1 H), 1.26

(t, J = 7.1 Hz, 3H); ¹³C NMR 100 MHz (CDCI₃): δ 172.8, 159.2, 132.0, 129.9, 114.2,

61.1, 55.6, 53.1 , 50.4, 14.6.

Compound 2:

/V-cvanomethanimidic acid ethyl ester

To cyanamide (about 1.2 mole) was added triethylorthoformate (about 1.33 mole), and the reaction mixture was heated to about 85-95 °C for approximately 2 hours to form Compound 2. Estimated in-solution yield was about 95-100%. The product was optionally purified by vacuum distillation.

¹H NMR 400 MHz (CDCI₃): δ 8.38 (s, 1H), 4.28 (t, J = 6.7 Hz, 2H), 1.29 (t, J =

6.8 Hz, 3H); ¹³C NMR 100 MHz (CDCI₃): δ 171.5, 113.4, 65.5, 13.1.

Compound 3A:

Figure imgf000051_0001

cis- and frans-glvcine Λ/-r(cvanoimino,methyl1-Λ/-r(4- methoxyphenvDmethvπ ethyl ester

A solution of Compound 1A (about 1.0 mole) in toluene was concentrated under vacuum to distill off toluene. Anhydrous tetrahydrofuran (“THF”) was added to the concentrate, then Compound 2 (about 1.2 moles, obtained above) was added to that, and the solution was heated at reflux for about 1 hour. At this stage, the formation of Compound 3A was complete. Estimated in-solution yield was about

95% (about 2:1 mixture of cis and trans isomers). Compound 4A: 1H-imidazole-5-carboxylic acid, 4-amino-1-[(4- methoxyphenvDmethvn ethyl ester

Compound 3A (obtained above) was concentrated by distilling off THF. Then, anhydrous ethanol was added to afford a reaction mixture solution. Separately, potassium t-butoxide (about 0.15 mole) was dissolved in anhydrous ethanol to afford a solution. The potassium t-butoxide solution was added to the reaction mixture solution and heated to about 75-85 °C for about 1 hour. The overall in-solution yield of Compound 4A was about 85-90%.

Figure imgf000051_0002

¹H NMR 400 MHz (CDCI₃): δ 7.16 (s, 1H), 7.08 (d, J = 8.6 Hz, 2H), 6.82 (d, J

=8.7 Hz, 2H), 5.23 (s, 2H), 4.93 (s, br, 2H), 4.23 (q, J = 7.1 , 2H), 3.76 (s, 3H), 1.26 (t,

J = 7.1 Hz, 3H); ¹³C NMR 400 MHz (CDCI₃): δ 160.9, 159.2, 139.0, 128.6, 128.5,

114.0, 101.8, 59.5, 55.2, 50.1 , 14.4.

Compound 5AK:

Figure imgf000052_0001

4A 5AK

1 -ethyl-3,7-dihydro-7-F(4-methoxyphenyl)methvπ-1 H-Purine-2.6- dione potassium salt

The reaction mixture containing Compound 4A in ethanol (obtained above) was added to diglyme and distilled under vacuum to remove the ethanol. After being cooled to room temperature, Λ/-ethylurethane (about 1.2 equiv.) was added and the

reaction mixture was heated to about 110-120 °C. A solution of potassium t-butoxide

(2.2 equiv.) in diglyme was added to the hot solution. The reaction mixture was cooled to room temperature. THF was added to precipitate additional product, which was filtered and washed to provide Compound Salt 5AK in 55-65% overall yield. The wet cake can be used as such for conversion to Compound 6A.

¹H NMR (DMSO-de, 400 MHz): δ 7.73 (s, 1H) 7.31 (d, J = 8.6 Hz , 2H) 6.86 (d,

J = 8.6 Hz, 2H) 5.24 (s, 1 H) 3.88 (q, J = 6.8 Hz, 2H) 3.71 (s, 3H) 1.07 (t, J = 6.8 Hz, 3H); ¹³C NMR (DMSO-d₆, 100 MHz): δ 161.1 , 159.0, 158.4, 157.2, 141.4, 131.0,

129.5, 114.1 , 105.6, 55.4, 48.2, 34.4, 14.3.

Optional Neutralization of Compound Salt 5AK to Compound 5A: Compound 5A: 1-ethyl-3,7-dihvdro-7-r(4-methoχyphenyl,methvπ-1 H-Purine-2,6- dione

The wet cake filtered solid of Compound Salt 5AK (obtained above) was suspended in water and then acidified to a pH of about 5 using glacial acetic acid. The resulting slurry was filtered to obtain the neutralized product, which was then washed with water and dried. The overall isolated yield of neutralized Compound 5A from Compound 1 A was about 45-55%. Spectroscopic data for neutralized Compound 5A was identical to that of Compound Salt 5AK.

Compound 6A:

3-r2-(acetyloxy,ethvn-1-ethyl-3,7-dihvdro-7-r(4- methoxyphenyl,methvπ-1H-purine-2,6-dione

To the wet cake filtered solid of Compound Salt 5AK (obtained above) were added tetrabutylammonium bromide (about 0.05 mole) and 2-bromoethyl acetate

(about 1.2 moles) in THF. After being heated to reflux for about 2 hours, part of the THF was distilled off, and isopropyl alcohol was added to the reaction mixture. The reaction mixture was then concentrated under reduced pressure and cooled to around room temperature. Water was added to precipitate the product. After being cooled to about 0-5 °C for about a few hours, the product was isolated by filtration. The wet cake was washed with aqueous isopropyl alcohol (about 30% in water), and dried under vacuum to afford Compound 6A as a pale yellow solid in about a 45- 55% overall yield (based on Compound 1A). The crude product may be purified further by decolorizing with Darco in methanol, followed by filtration and concentration to afford crystalline Compound 6A.

¹H NMR (CDCI3 , 400 MHz): δ 7.54 (s, 1 H) 7.32 (d, J = 8.6 Hz, 2H) 6.90 (d, J =

8.6 Hz, 2H) 5.43 (s, 2H) 4.41 (m, 2H) 4.38 (m, 2H) 4.10 (q, J = 7.2 Hz, 2H) 3.79 (s,

3H) 1.96 (s, 3H) 1.25 (t, J = 7.2 Hz, 3H); ¹³C NMR (CDCI₃ , 100 MHz): δ 171.1 ,

160.2, 155.3, 151.4, 148.9, 140.9, 130.1 , 127.7, 114.8, 107.5, 61.7, 55.6, 50.2, 42.4, 36.9, 21.2, 13.6.

After Optional Neutralization of Compound Salt 5AK to Compound 5A:

Compound 6A:

3-r2-(acetyloxy.ethvπ-1-ethyl-3,7-dihvdro-7-r.4- methoxyphenyl)methyn-1H-purine-2,6-dione

Acetonitrile was added to a mixture of Compound 5A (about 1.0 mole), anhydrous potassium carbonate (about 1.5 moles) and tetrabutylammonium hydrogen sulfate (about 0.05 mole). 2-bromoethyl acetate (about 1.5 moles) was added in three separate portions (0.72 mole in the beginning, another 0.45 mole after about 2 hours of reaction, and then the remaining 0.33 mole after about another

1 hour of reaction) during the course of the reaction at about 80-85 °C. The total reaction time was about 7 hours. The reaction mixture was cooled to about room temperature and filtered. The filtrate was concentrated. Aqueous isopropanol was added to crystallize the product. The product was filtered, washed with aqueous isopropanol, and dried to provide Compound 6A in about a 75-80% yield. Compound 7A: 8-bromo-1 -ethyl-3-r2-(acetyloxy)ethvπ-3,7-dihvdro-7-r(3-bromo-4- methoxyphenyl)methvπ-1 – -Purine-2,6-dione

Compound 6A (about 1 mole) and NBS (about 2.8 moles) were dissolved in

dry acetonitrile and agitated at about 15-20 °C. To this reaction mixture, a solution of

sulfuric acid (about 0.03 mol) in acetonitrile was added, while maintaining the

reaction temperature below about 25 °C. The reaction mixture was agitated at about

20-25 °C for about 12-15 hours until complete consumption of the starting material

was indicated. The reaction mixture was cooled to about 0-5 °C and a cold (about 5-

10 °C) aqueous solution of sodium sulfite was added, keeping the temperature below

about 10 °C. The reaction was agitated for about 2 hours at about 0-10 °C, and then

filtered. The isolated cake was washed with water, followed by methanol, then dried under a vacuum to obtain Compound 7A in about an 85% yield.

Figure imgf000053_0001

¹H NMR (CDCIs, 400 MHz): D 7.60 (d, J=2.0 Hz, 1H), 7.35 (dd, J=8.4 Hz, 2.0 Hz, 1 H), 6.83 (d, J=8.4 Hz, 1 H), 5.43 (s, 2H), 4.35 (m, 4H), 4.05 (q, J=7.0 Hz, 2H), 3.85 (s, 3H), 1.96 (s, 3H), 1.23 (t, J=7.0 Hz, 3H); ¹³C NMR (CDCI₃, 100 MHz): D 171.0, 156.2, 154.2, 150.8, 148.2, 138.3, 128.9, 128.7, 127.5, 112.1 , 112.0, 109.1 , 61.5, 56.5, 49.3, 42.5, 37.0, 21.0, 13.3. MS (ES) m/e 545.2 (M+H)⁺.

Compound 13A:

1-ethyl-3.7-dihvdro-8-r(1f?,2 )-(hvdroxycvclopentyl)amino1-3-(2- hvdroxyethvπ-7-r(3-bromo-4-methoxyphenvhmethvπ-1/–purine-2.6-dione

Compound 7A (about 1 mole) was combined with (R,R)-2-amino-1- cyclopentanol hydrochloride (Compound 8A, about 1.2 moles) and sodium bicarbonate (about 3 moles). To this reaction mixture was added N,N- dimethylacetamide (“DMA”), and the reaction mixture was agitated at about 135-140 °C for about 15-17 hours until complete consumption of the starting material was

indicated.

Figure imgf000053_0002

Compound 9A is an intermediate that is formed, but not isolated, from the

reaction mixture. The reaction mixture was then cooled to about 45-50 °C, and

tetrabutylammonium hydroxide (about 0.05 moles of about a 40% solution in water) was charged therein, followed by methanol. The reaction mixture was refluxed at

about 80-85 °C for about 8-9 hours until complete deprotection of the acetate group

was indicated. The reaction mixture was cooled to about 40-45 °C and concentrated

under vacuum. The pH of the reaction mixture was adjusted to about 5-6 with dilute

acetic acid, and the reaction mixture was heated to about 55-65 °C, and seeded with

a small amount of Compound 13A. The reaction mixture was then cooled to about

30-35 °C over a period of about 2 hours, and water was added over a period of

about 1 hour. The reaction mixture was further cooled to about 0-5 °C over a period

of about 1 hour, and agitated at that temperature for about 4 hours. The Compound 13A product was isolated by filtration, washed with water and dried to provide about an 85-90% yield.

Figure imgf000054_0002

9A 13A DASANTAFIL

¹H NMR (CDCI₃, 400 MHz): D 7.47 (d, J=2.1 Hz, 1 H), 7.18 (dd, J=8.4 Hz, 2.0 Hz, 1 H), 6.87 (d, J=8.4 Hz, 1H), 5.23 (s, 2H), 5.01 (s, 1 H), 4.22 (m, 2H), 4.15 (m, 1H), 4.05 (q, J=7.0 Hz, 2H), 3.93 (m, 3H), 3.88 (s, 3H), 3.77 (m, 1H), 2.95 (m, 1H), 2.15 (m, 1H), 2.05 (m, 1 H), 1.60-1.80 (m, 4H), 1.35 (m, 1 H), 1.23 (t, J=7.0 Hz, 3H); ¹³C NMR (CDCI₃, 100 MHz): D 156.2, 154.0, 153.5, 151.8, 148.3, 132.6, 129.1 , 127.9, 112.5, 103.2, 79.5, 77.8, 63.2, 61.3, 56.7, 46.5, 45.9, 36.8, 32.9, 31.5, 21.4, 13.8. MS (ES) m/e 523.4 (M+H)⁺. Micronization

INTERPRETATION

¹H NMR (CDCI₃, 400 MHz): DELTA

7.47 (d, J=2.1 Hz, 1 H), SANDWICHED AROM H BETWEEN BROMO AND -CH2-PY RING

7.18 (dd, J=8.4 Hz, 2.0 Hz, 1 H), AROM H ORTHO TO -CH2-PH RING AND PARA TO BROMO

6.87 (d, J=8.4 Hz, 1H), AROM H ORTHO TO O ATOM OF PH RING

5.23 (s, 2H), CH2 OF N-CH2-PH RING

5.01 (s, 1 H), OH OR NH 1H OUT OF 3 NOS

4.22 (m, 2H), OH OR NH 2H OUT OF 3 NOS

4.15 (m, 1H), –NCH2CH2OH 1H OUT OF 4 NOS

4.05 (q, J=7.0 Hz, 2H), CH2 OF NCH2 CH3

3.93 (m, 3H), —NCH2CH2OH 3H OUT OF 4 NOS

3.88 (s, 3H), -OCH3

3.77 (m, 1H), OH-CH OF CYCLOPENTANE RING

2.95 (m, 1H),NH-CH OF CYCLOPENTANE RING

2.15 (m, 1H),

2.05 (m, 1 H), 1H ON CYCLOPENTANE RING

1.60-1.80 (m, 4H), 4H ON CYCLOPENTANE RING

1.35 (m, 1 H), 1 H PARA TO SUBS IN CYCLOPENTANE RING

1.23 (t, J=7.0 Hz, 3H) –NCH2 CH3

………………………..

shark

DASANTAFIL

Links

REFERENCES

1 WANG Y ET AL: “DESIGN AND SYNTHESIS OF XANTHINE ANALOGUES AS POTENT AND SELECTIVE PDE5 INHIBITORS” BIOORGANIC & MEDICINAL CHEMISTRY LETTERS, OXFORD, GB, vol. 12, no. 21, 2002, pages 3149-3152, XP009014973 ISSN: 0960-894X

2. Peter K. Bridson and Xiaodong Wang in 1 -Substituted Xanthines, Synthesis, 855 (July, 1995)

PATENTS

1. WO 2002024698..

2. WO 2003101992..

3.WO 2010062366

4. WO 2007002125

5. WO 2006104870

6. WO 2005051368

7. US 2004167137

8. WO 2003101991

9.WO2006104870A2 , Schering Corp Methods of treating benign prostatic hyperplasia or lower urinary track symptoms by using pde 5 inhibitors

shark

WO2005012303A1 *	Jul 29, 2004	Feb 10, 2005	Kevin B Alton	Metabolite of xanthine phosphodiesterase 5 inhibitor and derivatives thereof useful for treatment of erectile dysfunction
US7312223	Jul 29, 2004	Dec 25, 2007	Schering Corporation	Metabolite of xanthine Phosphodiesterase 5 inhibitor and derivatives thereof useful for treatment of erectile dysfunction

WO2002024698A1 *	Sep 17, 2001	Mar 28, 2002	Schering Corp	Xanthine phosphodiesterase v inhibitors
WO2003020724A1 *	Aug 26, 2002	Mar 13, 2003	Schering Corp	Polycyclic guanine phosphodiesterase v inhibitors
WO2003042216A1 *	Nov 7, 2002	May 22, 2003	Schering Corp	Polycyclic guanine derivative phosphodiesterase v inhibitors
DE4411660A1 *	Apr 5, 1994	Oct 12, 1995	Hoechst Ag	Verwendung von Xanthinderivaten zur Reduktion der pathologischen Hyperreagibilität eosinophiler Granulozyten, neue Xanthinverbindungen und Verfahren zu deren Herstellung
EP0430025A2 *	Nov 20, 1990	Jun 5, 1991	Hokuriku Pharmaceutical Co., Ltd.	Xanthine compound, method for preparing thereof, and a pharmaceutical composition comprising the same
JP3072480A *				Title not available
JP4279586A *				Title not available
JP5001065A *				Title not available
US5728686 *	Oct 31, 1996	Mar 17, 1998	Hoechst Aktiengesellschaft	Alkylxanthine phosphonates and alkylxanthine phosphine oxides and their use as pharmaceuticals
US6214992 *	Jun 4, 1997	Apr 10, 2001	Hoechst Aktiengesellschaft	Use of theophylline derivatives for the treatment and prophylaxis of states of shock, novel xanthine compounds and processes for their preparation

shark

WO2003057200A2 *	13 jan 2003	17 juli 2003	Richard David Carr	Compositions comprising inhibitors of dpp-iv and nep enzymes for the treatment of diabetes
WO2003101991A1 *	30 mei 2003	11 dec 2003	Schering Corp	Xanthine phosphodiesterase v inhibitor polymorphs
WO2006026395A1 *	26 aug 2005	9 maart 2006	Richard Dixon	Endothelin a receptor (eta) antagonists in combination with phosphodiesterase 5 inhibitors (pde5) and uses thereof
US20020169174 *	28 aug 2001	14 nov 2002	Samuel Chackalamannil	Xanthine phosphodiesterase V inhibitors
US20030060627 *	25 jan 2002	27 maart 2003	Jordi Gracia Ferrer	8-Phenyl-6, 9-dihydro-[1,2,4] triazolo[3,4-i]purin-5-one derivatives
US20040063731 *	14 jan 2002	1 april 2004	Hans-Michael Eggenweiler	Pharmaceutical formulation comprising pyrazolo[4,3-d]pyrimidines and endothelin receptor antagonists or thienopyrimidines and endothelin receptor antagonists

US2011142956	6-17-2011	USE OF A PDE 5 INHIBITOR FOR TREATING AND PREVENTING HYPOPIGMENTARY DISORDERS
US7786301	8-32-2010	Process for preparing xanthine phosphodiesterase V inhibitors and precursors thereof
US2009149480	6-12-2009	METHODS OF USING PDE V INHIBITORS FOR THE TREATMENT OF CONGESTIVE HEART FAILURE
US7531544	5-13-2009	Xanthine Phosphodiesterase V Inhibitors
US2009105282	4-24-2009	METHODS OF TREATING BENIGN PROSTATIC HYPERPLASIA OR LOWER URINARY TRACT SYMPTOMS BY USING PDE 5 INHIBITORS
US2009074869	3-20-2009	PHARMACEUTICAL FORMULATIONS
US2008051408	2-29-2008	Use of a Pde 5 Inhibitor for Treating and Preventing Hypopigmentary Disorders
US7312223	12-26-2007	Metabolite of xanthine phosphodiesterase 5 inhibitor and derivatives thereof useful for treatment of erectile dysfunction
US7268141	9-12-2007	Xanthine phosphodiesterase V inhibitors
US2007122355	5-32-2007	RAPIDLY ABSORBING ORAL FORMULATIONS OF PDE 5 INHIBITORS


US7192962	3-21-2007	Xanthine phosphodiesterase V inhibitor polymorphs
US2007037831	2-16-2007	Methods of using PDE 5 inhibitors for the treatment of congestive heart failure
US2007031349	2-9-2007	Rapidly absorbing oral formulations of PDE 5 inhibitors
US2007004745	1-5-2007	Methods of treating benign prostatic hyperplasia or lower urinary tract symptoms by using PDE 5 inhibitors
US7074923	7-12-2006	Process for preparing xanthine phosphodiesterase V inhibitors and precursors thereof
US2006040962	2-24-2006	Pharmaceutical formulations
US2005182077	8-19-2005	Xanthine phosphodiesterase V inhibitors
US2005075349	4-8-2005	Xanthine phosphodiesterase V inhibitors
US6821978	11-24-2004	Xanthine phosphodiesterase V inhibitors
US2004229885	11-19-2004	Xanthine phosphodiesterase V inhibitors

Risk Assessment of Genotoxic Impurities in Marketed Compounds Administered over a Short-Term Duration: Applications to Oncology Products and Implications for Impurity Control Limits

regulatory, Uncategorized Comments Off

Jan 282014

Controlling impurities during drug development improves product quality and minimizes safety risks to the patient. Recent regulatory guidance on genotoxic impurities (GTIs) state that identified GTIs are unusually toxic and require lower reporting, identification, and qualification limits than outlined in the International Conference on Harmonization (ICH) guideline “Impurities in New Drug Substances Q3A(R2).” [ ICH Harmonized Tripartite Guideline: Impurities in New Drug Substances (Q3A), (R2); International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH), 2006.] Patient safety is always the underlying focus, but the overall impurity control strategy is also driven by appropriate “as low as reasonably practicable” (ALARP)(2)procedures that include assessment of process capability and associated analytical techniques. In combination with ALARP, safe and appropriate GTI levels are currently identified using chronic toxicology-based limits calculated under the standard assumption of 70-years for exposure duration. This paper proposes a risk assessment approach for developing GTI limits based on shorter-term exposure durations by highlighting marketed anticancer compounds with limited dosing schedules (e.g., 2 years). These limits are generally higher than the defaulted threshold of toxicological concern (TTC of 1.5 μg/day) and can result in more easily developed and less complex analytical methods. The described approach does not compromise safety and can potentially speed life-saving medicines to patients.

Risk Assessment of Genotoxic Impurities in Marketed Compounds Administered over a Short-Term Duration: Applications to Oncology Products and Implications for Impurity Control Limits

Courtney M. Callis, Joel P. Bercu, Keith M. DeVries, Linda K. Dow, David K. Robbins and David L. Varie

Org. Process Res. Dev., 2010, 14 (4), pp 986–992

Publication Date (Web): June 7, 2010 (Concept Article)

DOI: 10.1021/op1000226

READ AT

http://pubs.acs.org/doi/full/10.1021/op1000226

DOLUTEGRAVIR

Uncategorized Comments Off

Jan 272014

Dolutegravir

2H-Pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide, N-[(2,4-difluorophenyl)methyl]-3,4,6,8,12,12a-hexahydro-7-hydroxy-4-methyl-6,8-dioxo-, (4R,12aS)

(3R,11aS)—N-[(2,4-Difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide

(4R,12aS)-N-(2,4-difluorobenzyl)-7-hydroxy-4-methyl-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide
Trade Name:Tivicay
Synonym:GSK1349572, S-349572, GSK572
Date of Approval: August 12, 2013 (US)
Indication:HIV infection
Drug class: Integrase strand transfer inhibitor
Company: ViiV Healthcare,GlaxoSmithKline

INNOVATOR …ViiV Healthcare
CAS number: 1051375-16-6

MF:C20H19F2N3O5
MW:419.4
Chemical Name: (4R,12aS)-N-[(2,4-difluorophenyl)methyl]-7-hydroxy-4-methyl-6,8-dioxo-3,4,6,8,12,12a- hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide
Patent: US8129385
Patent expiration date: Oct 5, 2027
PCT patent application: W02006116764

Dolutegravir (DTG, GSK1349572) is an integrase inhibitor being developed for the treatment of human immunodeficiency virus (HIV)-1 infection by GlaxoSmithKline (GSK) on behalf of Shionogi-ViiV Healthcare LLC. DTG is metabolized primarily by uridine diphosphate glucuronyltransferase (UGT)1A1, with a minor role of cytochrome P450 (CYP)3A, and with renal elimination of unchanged drug being extremely low (< 1% of the dose).

The European Commission has on 21 January 2014 Dolutegravir (Tivicay, ViiV) permit as part of combination therapy for the treatment of HIV-infected persons over the age of 12 years.Dolutegravir (Tivicay, ViiV) is an integrase inhibitor, in combination with other antiretroviral drugs in adults and adolescents can be used from 12 years for the treatment of HIV infection.

Source: Communication from the European Commission

Dolutegravir^[1] is a FDA-approved drug^[2] for the treatment of HIV infection. Dolutegravir is an integrase inhibitor. Known as S/GSK1349572 or just “572” the drug is marketed as Tivicay^[3] by GlaxoSmithKline (GSK). In February, 2013 the Food and Drug Administration announced that it would fast track dolutegravir’s approval process.^[4] On August 13, 2013, dolutegravir was approved by the FDA. On November 4, 2013, dolutegravir was approved by Health Canada.^[5]

The oral HIV integrase inhibitor S-349572 was originated by Shionogi-GlaxoSmithKline and Shionogi-ViiV Healthcare. In 2013, the product was approved and launched in the U.S. for the treatment of HIV-1 in adults and children aged 12 years and older, in combination with other antiretroviral agents. A positive opinion was received in the E.U for this indication and, in 2014, approval was attained in Europe for this indication. Registration is pending in Japan.

In 2013, orphan drug designation in Japan was assigned to the compound.

Dolutegravir is approved for use in a broad population of HIV-infected patients. It can be used to treat HIV-infected adults who have never taken HIV therapy (treatment-naïve) and HIV-infected adults who have previously taken HIV therapy (treatment-experienced), including those who have been treated with other integrase strand transfer inhibitors. Tivicay is also approved for children ages 12 years and older weighing at least 40 kilograms (kg) who are treatment-naïve or treatment-experienced but have not previously taken other integrase strand transfer inhibitors.^[6]

Dolutegravir has also been compared head-to-head with a preferred regimen from the DHHS guidelines in each of the three classes (i.e. 1.) nuc + non-nuc, 2.) nuc + boosted PI, and 3.) nuc + integrase inhibitor).

SPRING-2 compared dolutegravir to another integrase inhibitor, raltegravir, with both coformulated with a choice of TDF/FTC orABC/3TC. After 48 weeks of treatment 88% of those on dolutegravir had less than 50 copies of HIV per mL compared to 85% in the raltegravir group, thus demonstrating non-inferiority.^[9]

The FLAMINGO study has been presented at scientific meetings but as of early 2014 has not yet been published. It is an open-label trial of dolutegravir versus darunavir boosted with ritonavir. In this trial 90% of those on dolutegravir based regimens had viral loads < 50 at 48 weeks compared to 83% in the darunavir/r.^[10] This 7% difference was statistically significant for superiority of the dolutegravir based regimens.

Another trial comparing dolutegravir to efavirenz, SINGLE, was the first trial to show statistical superiority to an efavirenz/FTC/TDF coformulated regimen for treatment naive patients.^[11] After 48 weeks of treatment, 88% of the dolutegravir group had HIV RNA levels < 50 copies / mL versus 81% of the efavirenz group. This has led one commentator to predict that it may replace efavirenz as the first line choice for initial therapy as it can also be formulated in one pill, once-a-day regimens.^[12]

Doultegravir has also been studied in patients who have been on previous antiretroviral medications. The VIKING trial looked at patients who had known resistance to the first generation integrase inhibitor raltegravir. After 24 weeks 41% of patients on 50mg dolutegravir once daily and 75% of patients on 50mg twice daily (both along with an optimized background regimen) achieved an HIV RNA viral load of < 50 copies per mL. This demonstrated that there was little clinical cross-resistance between the two integrase inhibitors. ^[13]

Dolutegravir (also known as S/GSK1349572), a second-generation integrase inhibitor under development by GlaxoSmithKline and its Japanese partner Shionogi for the treatment of HIV infection, was given priority review status from the US Food and Drug Administration (FDA) in February, 2013.

GlaxoSmithKline marketed the first HIV drug Retrovir in 1987 before losing out to Gilead Sciences Inc. (GILD) as the world’s biggest maker of AIDS medicines. The virus became resistant to Retrovir when given on its own, leading to the development of therapeutic cocktails.

The new once-daily drug Dolutegravir, which belongs to a novel class known as integrase inhibitors that block the virus causing AIDS from entering cells, is owned by ViiV Healthcare, a joint venture focused on HIV in which GSK is the largest shareholder.

Raltegravir (brand name Isentress) received approval by the U.S. Food and Drug Administration (FDA) on 12 October 2007, the first of a new class of HIV drugs, the integrase inhibitors, to receive such approval. it is a potent and well tolerated antiviral agent. However, it has the limitations of twice-daily dosing and a relatively modest genetic barrier to the development of resistance, prompting the search for agents with once-daily dosing.

Elvitegravir, approved by the FDA on August 27, 2012 as part of theelvitegravir/cobicistat/tenofovir disoproxil fumarate/emtricitabine fixed-dose combination pill (Quad pill, brand name Stribild) has the benefit of being part of a one-pill, once-daily regimen, but suffers from extensive cross-resistance with raltegravir.

Gilead’s Atripla (Emtricitabine/Tenofovir/efavirenz), approved in 2006 with loss of patent protection in 20121, is the top-selling HIV treatment. The $3.2 billion medicine combines three drugs in one pill, two compounds that make up Gilead’s Truvada (Emtricitabine/Tenofovir) and Bristol- Myers Squibb Co.’s Sustiva (Efavirenz).

A three-drug combination containing dolutegravir and ViiV’s older two-in-one treatment Epzicom(Abacavir/Lamivudine, marketed outside US as Kivexa) proved better than Gilead’s market-leading Atripla in a clinical trial released in July, 2012 (See the Full Conference Report Here), suggesting it may supplant the world’s best-selling AIDS medicine as the preferred front-line therapy. In the latest Phase III study, after 48 weeks of treatment, 88% of patients taking the dolutegravir-based regimen had reduced viral levels to the goal compared with 81% of patients taking Atripla. More patients taking Atripla dropped out of the study because of adverse events compared with those taking dolutegravir — 10% versus just 2% — which was the main driver of the difference in efficacy. The result was the second positive final-stage clinical read-out for dolutegravir, following encouraging results against U.S. company Merck & Co’s rival Isentress in April, 2012 (See the Conference Abstract Here)..

Dolutegravir is viewed by analysts as a potential multibillion-dollar-a-year seller, as its once-daily dosing is likely to be attractive to patients. The FDA is scheduled to issue a decision on the drug’s approval by August 17。

TIVICAY contains dolutegravir, as dolutegravir sodium, an HIV INSTI. The chemical name of dolutegravir sodium is sodium (4R,12aS)-9-{[(2,4-difluorophenyl)methyl]carbamoyl}-4-methyl-6,8-dioxo-3,4,6,8,12,12a-hexahydro-2H-pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazin-7-olate. The empirical formula is C₂₀H₁₈F₂N₃NaO₅ and the molecular weight is 441.36 g/mol. It has the following structural formula:

TIVICAY (dolutegravir) Structural Formula Illustration

Dolutegravir sodium is a white to light yellow powder and is slightly soluble in water.

Each film-coated tablet of TIVICAY for oral administration contains 52.6 mg of dolutegravir sodium, which is equivalent to 50 mg dolutegravir free acid, and the following inactive ingredients: D-mannitol, microcrystalline cellulose, povidone K29/32, sodium starch glycolate, and sodium stearyl fumarate. The tablet film-coating contains the inactive ingredients iron oxide yellow, macrogol/PEG, polyvinyl alcohol-part hydrolyzed, talc, and titanium dioxide.

……………………………………

INTRODUCTION

Among viruses, human immunodeficiency virus (HIV), a kind of retrovirus, is known to cause acquired immunodeficiency syndrome (AIDS). The therapeutic agent for AIDS is mainly selected from a group of reverse transcriptase inhibitors (e.g., AZT, 3TC) and protease inhibitors (e.g., Indinavir), but they are proved to be accompanied by side effects such as nephropathy and the emergence of resistant viruses. Thus, the development of anti-HIV agents having the other mechanism of action has been desired.

On the other hand, a combination therapy is reported to be efficient in treatment for AIDS because of the frequent emergence of the resistant mutant. Reverse transcriptase inhibitors and protease inhibitors are clinically used as an anti-HIV agent, however agents having the same mechanism of action often exhibit cross-resistance or only an additional activity. Therefore, anti-HIV agents having the other mechanism of action are desired.

Under the circumstances above, an HIV integrase inhibitor has been focused on as an anti-HIV agent having a novel mechanism of action (Ref: Patent Documents 1 and 2). As an anti-HIV agent having such a mechanism of action, known are carbamoyl-substituted hydroxypyrimidinone derivative (Ref: Patent Documents 3 and 4) and carbamoyl-substituted hydroxypyrrolidione derivative (Ref: Patent Document 5). Further, a patent application concerning carbamoyl-substituted hydroxypyridone derivative has been filed (Ref: Patent Document 6, Example 8).

Other known carbamoylpyridone derivatives include 5-alkoxypyridine-3-carboxamide derivatives and γ-pyrone-3-carboxamide derivatives, which are a plant growth inhibitor or herbicide (Ref: Patent Documents 7-9).

Other HIV integrase inhibitors include N-containing condensed cyclic compounds (Ref: Patent Document 10).

[Patent Document 1] WO03/0166275
[Patent Document 2] WO2004/024693
[Patent Document 3] WO03/035076
[Patent Document 4] WO03/035076
[Patent Document 5] WO2004/004657
[Patent Document 6] JP Patent Application 2003-32772
[Patent Document 7] JP Patent Publication 1990-108668
[Patent Document 8] JP Patent Publication 1990-108683
[Patent Document 9] JP Patent Publication 1990-96506
[Patent Document 10] WO2005/016927

Patent Document 1 describes compounds (I) and (II), which are useful as anti-HIV drugs and shown by formulae:
This document describes the following reaction formula as a method of producing compound (I).
Furthermore, Patent Documents 2 to 6 describe the following reaction formula as an improved method of producing compound (I).
[NON-PATENT DOCUMENTS]
- [Non-Patent Document 1] Journal of Organic Chemistry, 1991, 56(16), 4963-4967
  
  [Non-Patent Document 2] Science of Synthesis, 2005, 15, 285-387
  
  [Non-Patent Document 3] Journal of Chemical Society Parkin Transaction. 1, 1997, Issue. 2, 163-169

…………………………………………

Dolutegravir synthesis (EP2602260, 2013). LiHMDS as the non-nucleophilic strong base pulling compound 1 carbonyl group proton alpha position with an acid chloride after 2 and ring closure reaction to obtain 3 , 3 via primary amine 4 ring opening ring closure to obtain 5 , NBS the bromine under acidic conditions to obtain aldehyde acetal becomes 6 , 6 of the aldehyde and amino alcohols 7 and turn off the condensation reaction obtained by the ring 8 , alkaline hydrolysis 8 of bromine into a hydroxyl group and hydrolyzable ester obtained 9 after the 10 occurred acid condensation Dolutegravir.

………………………………………………………

Synthesis of Dolutegravir (S/GSK1349572, GSK1349572)

………………………

SYNTHESIS

2H-Pyrido[1′,2′:4,5]pyrazino[2,1-b][1,3]oxazine-9-carboxamide, N-[(2,4-difluorophenyl)methyl]-3,4,6,8,12,12a-hexahydro-7-hydroxy-4-methyl-6,8-dioxo-, (4R,12aS) ………..dolutegravir

PATENT US8129385

Desired isomer

Example Z-1

(3R,11aS)—N-[(2,4-Difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide sodium salt

(3R,11aS)—N-[(2,4-Difluorophenyl)methyl]-3-methyl-5,7-dioxo-6-[(phenylmethyl)oxy]-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide. To a solution of 16a (409 mg, 0.87 mmol) in dichloroethane (20 mL) was added (2R)-2-amino-1-propanol (0.14 mL, 1.74 mmol) and 10 drops of glacial acetic acid. The resultant solution was heated at reflux for 2 h. Upon cooling, Celite was added to the mixture and the solvents removed in vacuo and the material was purified via silica gel chromatography (2% CH₃OH/CH₂Cl₂gradient elution) to give (3R,11aS)—N-[(2,4-difluorophenyl)methyl]-3-methyl-5,7-dioxo-6-[(phenylmethyl)oxy]-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide (396 mg, 92%) as a glass. ¹H NMR (CDCl₃) δ 10.38 (m, 1H), 8.42 (s, 1H), 7.54-7.53 (m, 2H), 7.37-7.24 (m, 4H), 6.83-6.76 (m, 2H), 5.40 (d, J=10.0 Hz, 1H), 5.22 (d, J=10.0 Hz, 1H), 5.16 (dd, J=9.6, 6.0 Hz, 1H), 4.62 (m, 2H), 4.41 (m, 1H), 4.33-4.30 (m, 2H), 3.84 (dd, J=12.0, 10.0 Hz, 1H), 3.63 (dd, J=8.4, 7.2 Hz, 1H), 1.37 (d, J=6.0 Hz, 3H); ES⁺MS: 496 (M+1).

(3R,11aS)—N-[(2,4-Difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide sodium salt. To a solution of (3R,11aS)—N-[(2,4-difluorophenyl)methyl]-3-methyl-5,7-dioxo-6-[(phenylmethyl)oxy]-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide (396 mg, 0.80 mmol) in methanol (30 mL) was added 10% Pd/C (25 mg). Hydrogen was bubbled through the reaction mixture via a balloon for 2 h. The resultant mixture was filtered through Celite with methanol and dichloromethane.

The filtrate was concentrated in vacuo to give (3R,11aS)—N-[(2,4-difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide , DOLUTEGRAVIR as a pink tinted white solid (278 mg, 86%).

¹H NMR (CDCl₃) δ 11.47 (m, 1H), 10.29 (m, 1H), 8.32 (s, 1H), 7.36 (m, 1H), 6.82 (m, 2H), 5.31 (dd, J=9.6, 3.6 Hz, 1H), 4.65 (m, 2H), 4.47-4.38 (m, 3H), 3.93 (dd, J=12.0, 10.0 Hz, 1H), 3.75 (m, 1H), 1.49 (d, J=5.6 Hz, 3H); ES⁺ MS: 406 (M+1).

DOLUTEGRAVIR NA SALT

The above material (278 mg, 0.66 mmol) was taken up in ethanol (10 mL) and treated with 1 N sodium hydroxide (aq) (0.66 ml, 0.66 mmol). The resulting suspension was stirred at room temperature for 30 min. Ether was added and the liquids were collected to provide the sodium salt of the title compound as a white powder (291 mg, 99%). ¹H NMR (DMSO-d₆) δ 10.68 (m, 1H), 7.90 (s, 1H), 7.35 (m, 1H), 7.20 (m, 1H), 7.01 (m, 1H), 5.20 (m, 1H), 4.58 (m, 1H), 4.49 (m, 2H), 4.22 (m, 2H), 3.74 (dd, J=11.2, 10.4 Hz, 1H), 3.58 (m, 1H), 1.25 (d, J=4.4 Hz, 3H).

UNDESIRED ISOMER

Example Z-9

(3S,11aR)—N-[(2,4-Difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide sodium salt

The title compound was made in two steps using a similar process to that described in example Z-1. 16a (510 mg, 1.08 mmol) and (25)-2-amino-1-propanol (0.17 mL, 2.17 mmol) were reacted in 1,2-dichloroethane (20 mL) with acetic acid to give (3S,11aR)—N-[(2,4-difluorophenyl)methyl]-3-methyl-5,7-dioxo-6-[(phenylmethyl)oxy]-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide (500 mg, 93%). This material was hydrogenated in a second step as described in example Z-1 to give (3S,11aR)—N-[(2,4-Difluorophenyl)methyl]-6-hydroxy-3-methyl-5,7-dioxo-2,3,5,7,11,11a-hexahydro[1,3]oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide (386 mg, 94%) as a tinted white solid. ¹H NMR (CDCl₃) δ 11.46 (m, 1H), 10.28 (m, 1H), 8.32 (s, 1H), 7.35 (m, 1H), 6.80 (m, 2H), 5.30 (dd, J=10.0, 4.0 Hz, 1H), 4.63 (m, 2H), 4.48-4.37 (m, 3H), 3.91 (dd, J=12.0, 10.0 Hz, 1H), 3.73 (m, 1H), 1.48 (d, J=6.0 Hz, 3H); ES⁺ MS: 406 (M+1). This material (385 mg, 0.95 mmol) was treated with sodium hydroxide (0.95 mL, 1.0 M, 0.95 mmol) in ethanol (15 mL) as described in example Z-1 to provide its corresponding sodium salt (381 mg, 94%) as a white solid. ¹H NMR (DMSO-d₆) δ 10.66 (m, 1H), 7.93 (s, 1H), 7.33 (m, 1H), 7.20 (m, 1H), 7.01 (m, 1H), 5.19 (m, 1H), 4.59 (m, 1H), 4.48 (m, 2H), 4.22 (m, 2H), 3.75 (m, 1 H), 3.57 (m, 1H), 1.24 (d, J=5.6 Hz, 3H).

SYNTHESIS OF INTERMEDIATES

Figure US08129385-20120306-C00090

IN ABOVE SCHEME SYNTHESIS UPTO COMPD 9 MAY BE USEFUL IN SYNTHESIS BUT READERS DISCRETION IS SOUGHT IN THIS ?????????????????

1) Maltol 1 (189 g, 1.5 mol) was dissolved in dimethylformamide (1890 ml), and benzyl bromide (184 ml, 1.5 mol) was added. After the solution was stirred at 80° C. for 15 minutes, potassium carbonate (228 g, 1.65 mol) was added, and the mixture was stirred for 1 hour. After the reaction solution was cooled to room temperature, an inorganic salt was filtered, and the filtrate was distilled off under reduced pressure. To the again precipitated inorganic salt was added tetrahydrofuran (1000 ml), this was filtered, and the filtrate was distilled off under reduced pressure to obtain the crude product (329 g, >100%) of 3-benzyloxy-2-methyl-pyran-4-one 2 as a brown oil.

NMR (CDCl₃) δ: 2.09 (3H, s), 5.15 (2H, s), 6.36 (1H, d, J=5.6 Hz), 7.29-7.41 (5H, m), 7.60 (1H, d, J=5.6 Hz).

2) The compound 2 (162.2 g, 750 mmol) was dissolved in ethanol (487 ml), and aqueous ammonia (28%, 974 ml) and a 6N aqueous sodium hydroxide solution (150 ml, 900 mmol) were added. After the reaction solution was stirred at 90° C. for 1 hour, this was cooled to under ice-cooling, and ammonium chloride (58 g, 1080 mmol) was added. To the reaction solution was added chloroform, this was extracted, and the organic layer was washed with an aqueous saturated sodium bicarbonate solution, and dried with anhydrous sodium sulfate. The solvent was distilled off under reduced pressure, isopropyl alcohol and diethyl ether were added to the residue, and precipitated crystals were filtered to obtain 3-benzyloxy-2-methyl-1H-pyridine-4-one 3 (69.1 g, 43%) as a pale yellow crystal.

NMR (DMSO-d₆) δ: 2.05 (3H, s), 5.04 (2H, s), 6.14 (1H, d, J=7.0 Hz), 7.31-7.42 (5H, m), 7.46 (1H, d, J=7.2 Hz), 11.29 (1H, brs).

3) The above compound 3 (129 g, 699 mmol) was suspended in acetonitrile (1300 ml), and N-bromosuccinic acid imide (117 g, 659 mmol) was added, followed by stirring at room temperature for 90 minutes. Precipitated crystals were filtered, and washed with acetonitrile and diethyl ether to obtain 3-benzyloxy-5-bromo-2-methyl-pyridine-4-ol 4 (154 g, 88%) as a colorless crystal.

NMR (DMSO-d₆) δ: 2.06 (3H, s), 5.04 (2H, s), 7.32-7.42 (5H, m), 8.03 (1H, d, J=5.5 Hz), 11.82 (1H, brs).

4) To a solution of the compound 4 (88 g, 300 mmol), palladium acetate (13.4 g, 60 mmol) and 1,3-bis(diphenylphosphino)propane (30.8 g, 516 mmol) in dimethylformamide (660 ml) were added methanol (264 ml) and triethylamine (210 ml, 1.5 mol) at room temperature. The interior of a reaction vessel was replaced with carbon monoxide, and the material was stirred at room temperature for 30 minutes, and stirred at 80 degree for 18 hours. A vessel to which ethyl acetate (1500 ml), an aqueous saturated ammonium chloride solution (1500 ml) and water (1500 ml) had been added was stirred under ice-cooling, and the reaction solution was added thereto. Precipitates were filtered, and washed with water (300 ml), ethyl acetate (300 ml) and diethyl ether (300 ml) to obtain 5-benzyloxy-4-hydroxy-6-methyl-nicotinic acid methyl ester 5 (44.9 g, 55%) as a colorless crystal.

NMR (DMSO-d₆) δ: 2.06 (3H, s), 3.72 (3H, s), 5.02 (2H, s), 7.33-7.42 (5H, m), 8.07 (1H, s).

5) After a solution of the compound 5 (19.1 g, 70 mmol) in acetic anhydride (134 ml) was stirred at 130° C. for 40 minutes, the solvent was distilled off under reduced pressure to obtain 4-acetoxy-5-benzyloxy-6-methyl-nicotinic acid methyl ester 6 (19.9 g, 90%) as a flesh colored crystal.

NMR (CDCl₃) δ: 2.29 (3H, s), 2.52 (3H, s), 3.89 (3H, s), 4.98 (2H, s), 7.36-7.41 (5H, m), 8.85 (1H, s).

6) To a solution of the compound 6 (46.2 g, 147 mmol) in chloroform (370 ml) was added metachloroperbenzoic acid (65%) (42.8 g, 161 mmol) in portions under ice-cooling, and this was stirred at room temperature for 90 minutes. To the reaction solution was added a 10% aqueous potassium carbonate solution, and this was stirred for 10 minutes, followed by extraction with chloroform. The organic layer was washed with successively with a 10% aqueous potassium carbonate solution, an aqueous saturated ammonium chloride solution, and an aqueous saturated sodium chloride solution, and dried with anhydrous sodium sulfate. The solvent was distilled off under induced pressure, and the residue was washed with diisopropyl ether to obtain 4-acetoxy-5-benzyloxy-6-methyl-1-oxy-nicotinic acid methyl ester 7 (42.6 g, 87%) as a colorless crystal.

NMR (CDCl₃) δ: 2.30 (3H, s), 2.41 (3H, s), 3.90 (3H, s), 5.02 (2H, s), 7.37-7.39 (5H, m), 8.70 (1H, s).

7) To acetic anhydride (500 ml) which had been heated to stir at 130° C. was added the compound 7 (42.6 g, 129 mmol) over 2 minutes, and this was stirred for 20 minutes. The solvent was distilled off under reduced pressure to obtain 4-acetoxy-6-acetoxymethyl-5-benzyloxy-nicotinic acid methyl ester 8 (49.6 g, >100%) as a black oil.

NMR (CDCl₃) δ: 2.10 (3H, s), 2.28 (3H, s), 3.91 (3H, s), 5.07 (2H, s), 5.20 (2H, s), 7.35-7.41 (5H, m), 8.94 (1H, s).

8) To a solution of the compound 8 (46.8 g, 125 mmol) in methanol (140 ml) was added a 2N aqueous sodium hydroxide solution (376 ml) under ice-cooling, and this was stirred at 50° C. for 40 minutes. To the reaction solution were added diethyl ether and 2N hydrochloric acid under ice-cooling, and precipitated crystals were filtered. Resulting crystals were washed with water and diethyl ether to obtain 5-benzyloxy-4-hydroxy-6-hydroxymethyl-nicotinic acid 9 (23.3 g, 68%) as a colorless crystal.

NMR (DMSO-d₆) δ: 4.49 (2H, s), 5.19 (2H, s), 5.85 (1H, brs), 7.14-7.20 (2H, m), 7.33-7.43 (7H, m), 8.30 (1H, s), 10.73 (1H, t, J=5.8 Hz), 11.96 (1H, brs).

9) To a solution of the compound 9 (131 g, 475 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (219 g, 1140 mmol) and 1-hydroxybenzotriazole (128 g, 950 mmol) in dimethylformamide (1300 ml) was added 4-fluorobenzylamine (109 ml, 950 mmol), and this was stirred at 80° C. for 1.5 hours. After the reaction solution was cooled to room temperature, hydrochloric acid was added, followed by extraction with ethyl acetate. The extract was washed with a 5% aqueous potassium carbonate solution, an aqueous saturated ammonium chloride solution, and an aqueous saturated sodium chloride solution, and dried with anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain a mixture (175 g) of 10 and 11. the resulting mixture was dissolved in acetic acid (1050 ml) and water (1050 ml), and zinc (31.1 g, 475 mmol) was added, followed by heating to reflux for 1 hour. After the reaction solution was cooled to room temperature, a 10% aqueous potassium carbonate solution was added, followed by extraction with ethyl acetate. The extract was washed with an aqueous saturated ammonium chloride solution, and an aqueous saturated sodium chloride solution, and dried with anhydrous sodium sulfate. After the solvent was distilled off under reduced pressure, this was washed with diethyl ether to obtain 5-benzyloxy-N-(4-fluoro-benzyl)-4-hydroxy-6-hydroxymethyl-nicotinic acid amide 10 (107 g, 59%) as a colorless crystal.

NMR (DMSO-d₆) δ: 4.45 (2H, d, J=4.3 Hz), 4.52 (2H, d, J=5.8 Hz), 5.09 (2H, s), 6.01 (1H, brs), 7.36-7.43 (5H, m), 8.31 (1H, s), 12.63 (1H, brs).

………………..

SYNTHESIS

EP2602260A1

3H IS DOLUTEGRAVIR

Step 1

N,N-dimethylformamide dimethyl acetal (4.9 ml, 36.5 mmol) was added dropwise to compound 3A (5.0 g, 30.4 mmol) under cooling at 0°C. After stirring at 0°C for 1 hour, 100 ml of ethyl acetate was added to the reaction solution, and the organic layer was washed with a 0.5 N aqueous hydrochloric acid solution (50 ml). The aqueous layer was separated, followed by extraction with ethyl acetate (50 ml). The organic layers were combined, washed with a saturated aqueous solution of sodium bicarbonate and saturated saline in this order, and then dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained residue was purified by silica gel column chromatography (n-hexane-ethyl acetate: 1:1 (v/v) → ethyl acetate) to obtain 4.49 g (yield: 67%) of compound 3B as an oil.
¹H-NMR (CDCl₃)δ:1.32 (3H, t, J = 7.1 Hz), 2.90 (3H, br s), 3.29 (3H, br s), 4.23 (2H, q, J = 7.1 Hz), 4.54 (2H, s), 7.81 (1H, s).

Step 2

Lithium hexamethyldisilazide (1.0 M solution in toluene, 49 ml, 49.0 mmol) was diluted with tetrahydrofuran (44 ml). A tetrahydrofuran (10 ml) solution of compound 3B (4.49 g, 20.4 mmol) was added dropwise thereto under cooling at -78°C, and a tetrahydrofuran (10 ml) solution of ethyl oxalyl chloride (3.35 g, 24.5 mmol) was then added dropwise to the mixture. The mixture was stirred at -78°C for 2 hours and then heated to 0°C. 2 N hydrochloric acid was added to the reaction solution, and the mixture was stirred for 20 minutes, followed by extraction with ethyl acetate (200 ml x 2). The organic layer was washed with a saturated aqueous solution of sodium bicarbonate and saturated saline and then dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained residue was purified by silica gel column chromatography (n-hexane-ethyl acetate: 7:3 → 5:5 → 0:10 (v/v)) to obtain 1.77 g (yield: 31%) of compound 3C as a white solid.
¹H-NMR (CDCl₃)δ:1.36-1.46 (6H, m), 4.35-4.52 (8H, m), 8.53 (1H, s).

Step 3

Aminoacetaldehyde dimethyl acetal (0.13 ml, 1.20 mmol) was added to an ethanol (6 ml) solution of compound 3C (300 mg, 1.09 mmol) at 0°C, and the mixture was stirred at 0°C for 1.5 hours, then at room temperature for 18 hours, and at 60°C for 4 hours. The solvent in the reaction solution was distilled off under reduced pressure, and the obtained residue was then purified by silica gel column chromatography (n-hexane-ethyl acetate: 5:5 → 0:10 (v/v)) to obtain 252 mg (yield: 64%) of compound 3D as an oil.
¹H-NMR (CDCl₃)δ:1.36-1.47 (6H, m), 3.42 (6H, s), 3.90 (2H, d, J = 5.2 Hz), 4.37 (3H, q, J = 7.2 Hz), 4.50 (2H, q, J = 7.2 Hz), 8.16 (1H, s).

Step 4

62% H₂SO₄ (892 mg, 5.64 mmol) was added to a formic acid (10 ml) solution of compound 3D (1.02 g, 2.82 mmol), and the mixture was stirred at room temperature for 16 hours. The formic acid was distilled off under reduced pressure. To the residue, methylene chloride was added, and the mixture was pH-adjusted to 6.6 by the addition of a saturated aqueous solution of sodium bicarbonate. The methylene chloride layer was separated, while the aqueous layer was subjected to extraction with methylene chloride. The methylene chloride layers were combined and dried over anhydrous sodium sulfate. The solvent was distilled off to obtain 531.8 mg of compound 3E as a yellow oil.
1H-NMR (CDCl3) δ: 1.28-1.49 (6H, m), 4.27-4.56 (4H, m), 4.84 (2H, s), 8.10 (1H, s), 9.72 (1H, s).

Step 5

Methanol (0.20 ml, 5.0 mmol), (R)-3-amino-butan-1-ol (179 mg, 2.0 mmol), and acetic acid (0.096 ml, 1.70 mmol) were added to a toluene (5 ml) solution of compound 3E (531 mg, 1.68 mmol), and the mixture was heated to reflux for 4 hours. The reaction solution was cooled to room temperature, then diluted with chloroform, and then washed with a saturated aqueous solution of sodium bicarbonate. The aqueous layer was subjected to extraction with chloroform. The chloroform layers were combined, washed with saturated saline, and then dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained residue was purified by silica gel column chromatography (chloroform-methanol: 100:0 → 90:10) to obtain 309.4 mg of compound 3F as a brown oil.
1H-NMR (CDCl3) δ: 1.40 (3H, t, J = 7.1 Hz), 1.40 (3H, d, J = 7.1 Hz), 1.55-1.61 (1H, m), 2.19-2.27 (1H, m), 4.00 (1H, d, J = 1.5 Hz), 4.03 (1H, d, J = 2.5 Hz), 4.10 (1H, dd, J = 13.2, 6.3 Hz), 4.26 (1H, dd, J = 13.2, 3.8 Hz), 4.38 (2H, q, J = 7.1 Hz), 5.00-5.05 (1H, m), 5.31 (1H, dd, J = 6.4, 3.9 Hz), 8.10 (1H, s).

Step 6

Potassium trimethylsilanolate (333 mg, 2.34 mmol) was added to a 1,2-dimethoxyethane (2 ml) solution of compound 3F (159 mg, 0.47 mmol), and the mixture was stirred at room temperature for 7 hours. 1 N hydrochloric acid and saturated saline were added to the reaction solution, followed by extraction with chloroform. The chloroform layers were combined and dried over anhydrous sodium sulfate. The solvent was distilled off to obtain 34.4 mg (yield: 25%) of compound 3G as an orange powder.
1H-NMR (CDCl3) δ: 1.46 (3H, d, J = 3.5 Hz), 1.58-1.65 (1H, m), 2.26-2.30 (1H,m), 4.06-4.10 (2H, m), 4.31 (1H, dd, J = 13.8, 5.6 Hz), 4.48 (1H, dd, J = 13.6, 3.9 Hz), 5.03 (1H, t, J = 6.4 Hz), 5.36 (1H, dd, J = 5.5, 4.0 Hz), 8.44 (1H, s), 12.80 (1H, s), 14.90 (1H, s).

Step 7

Compound 3G (16 mg, 0.054 mmol) and 2,4-difluorobenzylamine (17 mg, 0.12 mmol) were dissolved in N,N-dimethylformamide (1 ml). To the solution, N,N,N’,N’-tetramethyl-O-(7-aza-benzotriazol-1-yl)uronium hexafluorophosphate (HATU) (53 mg, 0.14 mmol) and N-methylmorpholine (0.031 ml, 0.28 mmol) were added, and the mixture was stirred at room temperature for 16 hours. 2,4-difluorobenzylamine (17 mg, 0.12 mmol), HATU (64 mg, 0.17 mmol), and N-methylmorpholine (0.037 ml, 0.34 mmol) were further added thereto, and the mixture was stirred at room temperature for additional 16 hours. 0.5 N hydrochloric acid was added to the reaction solution, followed by extraction with ethyl acetate. The ethyl acetate layers were combined, washed with 0.5 N hydrochloric acid and then with saturated saline, and then dried over anhydrous sodium sulfate. The solvent was distilled off, and the obtained residue was purified by preparative high-performance liquid chromatography to obtain 12.5 mg (yield: 55%) of compound 3H as an orange solid.
DOLUTEGRAVIR
1H-NMR (DMSO-d6) δ: 1.36 (3H, d, J = 6.9 Hz), 1.55-1.60 (1H, m), 2.01-2.05 (1H, m), 3.92-3.94 (1H, m), 4.04 (1H, t, J = 12.6 Hz), 4.38-4.41 (1H, m), 4.57-4.60 (1H, m), 4.81-4.83 (1H, m), 5.46-5.49 (1H, m), 7.08-7.11 (1H, m), 7.25-7.30 (1H, m), 7.41 (1H, dd, J = 15.3, 8.7 Hz), 8.53 (1H, s), 10.38 (1H, s), 12.53 (1H, s).

ISOMERS OF DOLUTEGRAVIR

Step 1

Acetic acid (180 mg, 3.00 mmol) was added to a toluene (90 ml) solution of compound A-1 (4.39 g, 9.33 mmol) and (R)-3-aminobutan-1-ol (998 mg, 11.2 mmol), and the mixture was stirred at 50°C for 90 minutes. The reaction solution was allowed to cool to room temperature and then poured to a saturated aqueous solution of sodium bicarbonate. The organic layer was separated, while the aqueous layer was subjected to extraction three times with ethyl acetate. The combined extracts were washed with saturated saline and then dried over sodium sulfate. The solvent was distilled off to obtain 4.29 g of crude product A-2.

Step 2

The crude product A-2 obtained in the preceding step was dissolved in ethanol (40 ml). To the solution, a 2 N aqueous sodium hydroxide solution (20 ml) was added at room temperature, and the mixture was stirred at the same temperature for 2 hours. The reaction solution was neutralized to pH 7 using a 2 N aqueous hydrochloric acid solution. The solvent was directly distilled off. The obtained crude product A-3 was subjected to azeotropy with toluene (100 ml) and used in the next step without being purified.

Step 3

HOBt (1.65 g, 12.2 mmol) and WSC HCl (2.34 g, 12.2 mmol) were added at room temperature to a DMF (100 ml) solution of the crude product A-3 obtained in the preceding step, and the mixture was stirred at the same temperature for 15 hours. Water was added to the reaction solution, followed by extraction three times with ethyl acetate. The combined extracts were washed with water three times and then dried over sodium sulfate. The solvent was distilled off, and the obtained oil was subjected to silica gel column chromatography for purification. Elution was performed first with n-hexane-ethyl acetate (3:7, v/v) and then with only ethyl acetate. The fraction of interest was concentrated, and the obtained oil was then dissolved in ethyl acetate. The solution was crystallized with diisopropyl ether as a poor solvent. The obtained crystals were collected by filtration and dissolved again in ethyl acetate. The solution was recrystallized to obtain 1.84 g of compound A-4.
¹HNMR (CDCl₃) δ: 1.49 (3H, d, J = 6.6 Hz), 1.88-1.96 (1H, m), 2.13-2.26 (1H, m), 3.90-4.17 (4H, m), 4.42-4.47 (1H, m), 4.63 (2H, d, J = 6.0 Hz), 5.12-5.17 (1H, m), 5.17 (1H, d, J = 9.9 Hz), 5.33 (1H, d, J = 9.9 Hz), 6.77-6.87 (2H, m), 7.27-7.42 (4H, m), 7.59-7.62 (2H, m), 8.35 (1H, s), 10.41 (1H, t, J = 5.7 Hz).

Step 4

The compound A-4 was subjected to the hydroxy deprotection reaction described in Step F of the paragraph [0088] to obtain compound A-5.
¹HNMR (DMSO-d₆) δ:1.41 (3H, d, J = 6.3 Hz), 1.85-1.92 (1H, m), 1.50-1.75 (1H, m), 4.02-4.09 (3H, m), 4.28-4.34 (1H, m), 4.53 (2H, d, J = 5.7 Hz), 4.64 (1H, dd, J = 3.9 Hz, 12.6 Hz), 5.45 (1H, dd, J = 3.6 Hz, 9.3 Hz), 7.06 (1H, ddd, J = 2.7 Hz, 8.4 Hz, 8.4 Hz), 7.20-7.28 (1H, m), 7.35-7.42 (1H, m), 8.43 (1H, s),10.37 (1H, t, J = 6.0 Hz),12.37 (1H, brs).

Compound A-1 was reacted with (S)-3-aminobutan-1-ol in Step 1. Compound B-5 was obtained in the same way as in Reference Example 1.
¹HNMR (DMSO-d₆) δ:1.41 (3H, d, J = 6.3 Hz), 1.85-1.92 (1H, m), 1.50-1.75 (1H, m), 4.02-4.09 (3H, m), 4.28-4.34 (1H, m), 4.53 (2H, d, J = 5.7 Hz), 4.64 (1H, dd, J = 3.9 Hz, 12.6 Hz), 5.45 (1H, dd, J = 3.6 Hz, 9.3 Hz), 7.06 (1H, ddd, J = 2.7 Hz, 8.4 Hz, 8.4 Hz), 7.20-7.28 (1H, m), 7.35-7.42 (1H, m), 8.43 (1H, s),10.37 (1H, t, J = 6.0 Hz),12.37 (1H, brs).

……………..

W02006116764

Figure imgf000122_0001

ENTRY 68

………………………….

WO 2010068262

…………………………

WO 2010068253

…………………………………

WO 2011119566

…………………………..

WO 2012018065

Example 3

I was under cooling added dropwise at 0 ℃ (4.9 ml, 36.5 mmol) and N, N-dimethylformamide dimethyl acetal (5.0 g, 30.4 mmol) in the first step compound 3A. After stirring for 1 hour at 0 ℃, ethyl acetate was added to 100ml, the reaction mixture was washed with 0.5N aqueous hydrochloric acid (50 ml). Was extracted with ethyl acetate (50ml) and solution was separated and the aqueous layer. The organic layers were combined, washed successively with saturated aqueous sodium bicarbonate solution and saturated brine, and then dried over anhydrous sodium sulfate. After the solvent was distilled off, silica gel column chromatography and the residue obtained was – and purified by (n-hexane (v / v) → ethyl acetate 1:1) to an oil (67% yield) of Compound 3B 4.49 g I got a thing.
¹ H-NMR (CDCl ₃₎ ^δ: 1.32 (3H, t, J = 7.1 Hz), 2.90 (3H, br s), 3.29 (3H, br s), 4.23 (2H, q, J = 7.1 Hz), 4.54 (2H, s), 7.81 (1H, s).
Diluted with tetrahydrofuran (44 ml) (1.0M toluene solution, 49 ml, 49.0 mmol) the second step lithium hexamethyldisilazide, under cooling at -78 ℃, compound 3B (4.49 g, 20.4 mmol) in this After dropwise tetrahydrofuran (10 ml) was added dropwise tetrahydrofuran (3.35 g, 24.5 mmol) of ethyl oxalyl chloride and (10 ml) solution. After stirring for 2 hours at -78 ℃, I was warmed to 0 ℃. After washing (200 ml x 2), saturated aqueous sodium bicarbonate solution and the organic layer with saturated brine After stirring for 20 minutes, extracted with ethyl acetate by adding 2N hydrochloric acid, the reaction solution was dried over anhydrous sodium sulfate. After removal of the solvent, silica gel column chromatography and the residue obtained – was purified (n-hexane (v / v) ethyl acetate 7:3 → 5:5 → 0:10), compound 3C 1.77 g (yield I as a white solid 31%).
¹ H-NMR (CDCl ₃₎ ^{δ :1.36-1} .46 (6H, m), 4.35-4.52 (8H, m), 8.53 (1H, s).
Was added at 0 ℃ (0.13 ml, 1.20 mmol) the aminoacetaldehyde dimethyl acetal ethanol (300 mg, 1.09 mmol) of the third step compound 3C to (6 ml) solution, 1 hour and 30 minutes at 0 ℃, 18 hours at room temperature , then I was stirred for 4 hours at 60 ℃. After the solvent was evaporated under reduced pressure and the reaction mixture by silica gel column chromatography and the residue obtained was – and purified by (n-hexane (v / v) ethyl acetate 5:5 → 0:10), compound 3D 252 mg (yield: I got as an oil 64%) rate.
¹ H-NMR (CDCl ₃₎ ^{δ :1.36-1} .47 (6H, m), 3.42 (6H, s), 3.90 (2H, d, J = 5.2 Hz), 4.37 (3H, q, J = 7.2 Hz), 4.50 (2H, q, J = 7.2 Hz), 8.16 (1H, s).
Was added (892 mg, 5.64 mmol) and ₂ SO ₄ 62-H% formic acid (1.02 g, 2.82 mmol) in a fourth step the compound for 3D (10 ml) solution was stirred at room temperature for 16 hours. Methylene chloride was added to the residue Shi distilled off under reduced pressure and formic acid was adjusted to pH = 6.6 by addition of saturated aqueous sodium bicarbonate. The solution was separated methylene chloride layer was extracted with methylene chloride and the aqueous layer. I was dried over anhydrous sodium sulfate combined methylene chloride layers. The solvent was then distilled off and was obtained as a yellow oil 531.8 mg compound 3E.
1H-NMR (CDCl3) δ: 1.28-1.49 (6H, m), 4.27-4.56 (4H, m), 4.84 (2H, s), 8.10 (1H, s), 9.72 (1H, s).
Amino – – butane – 1 – ol (179 mg, 2.0 mmol), methanol (0.20 ml, 5.0 mmol), (R) -3 toluene (531 mg, 1.68 mmol) in the fifth step to compound 3E (5 ml) solution was added (0.096 ml, 1.70 mmol) acetic acid was heated under reflux for 4 hours. After dilution with chloroform, cooled to room temperature, the reaction mixture was washed with a saturated aqueous sodium bicarbonate solution, and the aqueous layer was extracted with chloroform. After washing with saturated brine combined chloroform layer was dried over anhydrous sodium sulfate. The solvent was then distilled off, silica gel column chromatography and the residue obtained – and (chloroform methanol 100:0 → 90:10), was obtained as a brown oil 309.4 mg compound 3F.
1H-NMR (CDCl3) δ: 1.40 (3H, t, J = 7.1 Hz), 1.40 (3H, d, J = 7.1 Hz), 1.55-1.61 (1H, m), 2.19-2.27 (1H, m), 4.00 (1H, d, J = 1.5 Hz), 4.03 (1H, d, J = 2.5 Hz), 4.10 (1H, dd, J = 13.2, 6.3 Hz), 4.26 (1H, dd, J = 13.2, 3.8 Hz ), 4.38 (2H, q, J = 7.1 Hz), 5.00-5.05 (1H, m), 5.31 (1H, dd, J = 6.4, 3.9 Hz), 8.10 (1H, s).
1,2 (159 mg, 0.47 mmol) in the sixth step compound 3F – was added (333 mg, 2.34 mmol) and potassium trimethylsilanolate dimethoxyethane (2 ml) solution was stirred for 7 hours at room temperature. Brine was added to the 1N-hydrochloric acid to the reaction mixture, followed by extraction with chloroform. The combined chloroform layer was dried over anhydrous sodium sulfate. The solvent was removed by distillation, and I as an orange powder (25% yield) of compound 3G 34.4 mg.
1H-NMR (CDCl3) δ: 1.46 (3H, d, J = 3.5 Hz), 1.58-1.65 (1H, m), 2.26-2.30 (1H, m), 4.06-4.10 (2H, m), 4.31 (1H , dd, J = 13.8, 5.6 Hz), 4.48 (1H, dd, J = 13.6, 3.9 Hz), 5.03 (1H, t, J = 6.4 Hz), 5.36 (1H, dd, J = 5.5, 4.0 Hz) , 8.44 (1H, s), 12.80 (1H, s), 14.90 (1H, s).
2,4 (16 mg, 0.054 mmol) and the seventh step compound 3G – was dissolved in N, N-dimethylformamide (1 ml) (17 mg, 0.12 mmol) difluorobenzyl amine, N, N, N ‘, N was added (0.031 ml, 0.28 mmol) and N-methylmorpholine uronium hexafluorophosphate (HATU) (53 mg, 0.14 mmol), and ‘- tetramethyl-O-(yl 7 – aza – – benzo triazolopyrimidine -1) I was stirred at room temperature for 16 h. 2,4 – was added (0.037 ml, 0.34 mmol) and N-methylmorpholine (64 mg, 0.17 mmol) and (17 mg, 0.12 mmol), HATU difluorobenzylamine, and the mixture was stirred for 16 hours at room temperature. I was extracted with ethyl acetate addition of 0.5N-hydrochloric acid to the reaction mixture. 0.5N-hydrochloric acid and then was washed with saturated brine, and dried over anhydrous sodium sulfate and combined ethyl acetate layer. The solvent was then distilled off, and purified by preparative high performance liquid chromatography residue was obtained as an orange solid (55% yield) of compound 3H 12.5 mg.
1H-NMR (DMSO-d6) δ: 1.36 (3H, d, J = 6.9 Hz), 1.55-1.60 (1H, m), 2.01-2.05 (1H, m), 3.92-3.94 (1H, m), 4.04 (1H, t, J = 12.6 Hz), 4.38-4.41 (1H, m), 4.57-4.60 (1H, m), 4.81-4.83 (1H, m), 5.46-5.49 (1H, m), 7.08-7.11 (1H, m), 7.25-7.30 (1H, m), 7.41 (1H, dd, J = 15.3, 8.7 Hz), 8.53 (1H, s), 10.38 (1H, s), 12.53 (1H, s)

References

[1] American Medical Association (AMA), STATEMENT ON A NONPROPRIETARY NAME ADOPTED BY THE USAN COUNCIL (Dolutegravir) Accessed 3 December 2011.
FDA approves new drug to treat HIV infection http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm364744.htm Aug. 12, 2013
“U.S. FDA approves GlaxoSmithKline’s HIV drug Tivicay”. Reuters. 12 August 2013. Retrieved 13 February 2013.
“GSK wins priority status for new HIV drug in U.S”. Reuters. 16 February 2013. Retrieved 18 February 2013.
“ViiV Healthcare receives approval for Tivicay™ (dolutegravir) in Canada for the treatment of HIV”. Retrieved 11 November 2013.
FDA approves new drug to treat HIV infection http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm364744.htm Aug. 12, 2013
U.S. FDA approves GlaxoSmithKline’s HIV drug Tivicay http://www.reuters.com/article/2013/08/12/us-glaxosmithkline-hivdrug-idUSBRE97B0WU20130812 Mon Aug 12, 2013 6:40pm EDT
“Dolutegravir Prescribing Information”. Retrieved 3 January 2014.
Raffi, F; Jaeger, H; Quiros-Roldan, E; Albrecht, H; Belonosova, E; Gatell, JM; Baril, JG; Domingo, P; Brennan, C; Almond, S; Min, S; extended SPRING-2 Study, Group (Nov 2013). “Once-daily dolutegravir versus twice-daily raltegravir in antiretroviral-naive adults with HIV-1 infection (SPRING-2 study): 96 week results from a randomised, double-blind, non-inferiority trial.”. The Lancet infectious diseases 13 (11): 927–35. PMID 24074642.
Jump up^ http://www.natap.org/2013/ICAAC/ICAAC_24.htm
Walmsley, Sharon L.; Antela, Antonio; Clumeck, Nathan; Duiculescu, Dan; Eberhard, Andrea; Gutiérrez, Felix; Hocqueloux, Laurent; Maggiolo, Franco; Sandkovsky, Uriel; Granier, Catherine; Pappa, Keith; Wynne, Brian; Min, Sherene; Nichols, Garrett (7 November 2013). “Dolutegravir plus Abacavir–Lamivudine for the Treatment of HIV-1 Infection”. New England Journal of Medicine 369 (19): 1807–1818. doi:10.1056/NEJMoa1215541.
Sax, Paul. “SINGLE Study Underscores Waning of the Efavirenz Era — But Probably Just in the USA – See more at:http://blogs.jwatch.org/hiv-id-observations/index.php/single-study-underscores-waning-of-the-efavirenz-era-but-probably-just-in-the-usa/2013/11/06/#sthash.A39SderN.dpuf”. Retrieved 19 December 2013.
Eron, JJ; Clotet, B; Durant, J; Katlama, C; Kumar, P; Lazzarin, A; Poizot-Martin, I; Richmond, G; Soriano, V; Ait-Khaled, M; Fujiwara, T; Huang, J; Min, S; Vavro, C; Yeo, J; VIKING Study, Group (2013 Mar 1). “Safety and efficacy of dolutegravir in treatment-experienced subjects with raltegravir-resistant HIV type 1 infection: 24-week results of the VIKING Study.”. The Journal of infectious diseases 207 (5): 740–8. PMID 23225901.
WO2010011812A1 * Jul 23, 2009 Jan 28, 2010 Smithkline Beecham Corporation Chemical compounds

WO2010011819A1 * Jul 23, 2009 Jan 28, 2010 Smithkline Beecham Corporation Chemical compounds
[NON-PATENT DOCUMENTS]
- - [Non-Patent Document 1] Journal of Organic Chemistry, 1991, 56(16), 4963-4967
  - [Non-Patent Document 2] Science of Synthesis, 2005, 15, 285-387
  - [Non-Patent Document 3] Journal of Chemical Society Parkin Transaction. 1, 1997, Issue. 2, 163-169

…………………

Sources:

Johns, Brian Alvin; Kawasuji, Takashi; Taishi, Teruhiko; Taoda, Yoshiyuki ; Polycyclic carbamoylpyridone derivative having HIV integrase inhibitory activity and their preparation; PCT Int. Appl., WO2006116764, 02 Nov 2006

Johns, Brian Alvin; Weatherhead, Jason Gordon;Tricyclic heterocyclic compounds as antiviral agents and their preparation and use in the treatment of HIV infection; PCT Int. Appl., WO2010011812, 28 Jan 2010

Johns, Brian Alvin; Weatherhead, Jason Gordon; Tricyclic heterocyclic compounds as antiviral agents and their preparation and use in the treatment of HIV infection;PCT Int. Appl., WO2010011819, 28 Jan 2010

Yoshida, Hiroshi; Taoda, Yoshiyuki; Johns, Brian Alvin; Synthesis of fused tricyclic carbamoylpyridone HIV integrase inhibitors and intermediates;PCT Int. Appl.,WO2010068253, 17 Jun 2010

Johns, Brian Alvin; Duan, Maosheng; Hakogi, Toshikazu;Processes and intermediates for fused tricyclic carbamoylpyridone HIV integrase inhibitors;PCT Int. Appl., WO2010068262, 17 Jun 2010

Sumino, Yukihito; Okamoto, Kazuya; Masui, Moriyasu; Yamada, Daisuke; Ikarashi, Fumiya;Preparation of compounds having HIV integrase inhibitory activity; PCT Int. Appl.,WO2012018065, 09 Feb 2012

Kawasuji, Takashi; Johns, Brian A.;Discovery of dolutegravir and S/GSK1265744: Carbamoyl pyridone HIV-1 integrase inhibitors;Abstracts, 64th Southeast Regional Meeting of the American Chemical Society, Raleigh, NC, United States, November 14-17 (2012), SERM-176.

Kawasuji, Takashi; Johns, Brian A.; Yoshida, Hiroshi; Weatherhead, Jason G.; Akiyama, Toshiyuki; Taishi, Teruhiko; Taoda, Yoshiyuki; Mikamiyama-Iwata, Minako; Murai, Hitoshi; Kiyama, Ryuichi; Fuji, Masahiro; Tanimoto, Norihiko; Yoshinaga, Tomokazu; Seki, Takahiro; Kobayashi, Masanori; Sato, Akihiko; Garvey, Edward P.; Fujiwara, Tamio; Carbamoyl Pyridone HIV-1 Integrase Inhibitors. 2. Bi- and Tricyclic Derivatives Result in Superior Antiviral and Pharmacokinetic Profiles;Journal of Medicinal Chemistry (2013), 56(3), 1124-1135

Walmsley S et al. Dolutegravir (DTG; S/GSK1349572) + abacavir/lamivudine once daily statistically superior to tenofovir/emtricitabine/efavirenz: 48-week results – SINGLE (ING114467). 52nd ICAAC, 9-12 September 2012, San Francisco. Abstract H-556b.
http://www.abstractsonline.com/Plan/ViewAbstract.aspx?sKey=e1c18d5b-830f-4b4e-8671-35bcfb20eed5&cKey=af219b7d-2171-46b2-91ef-b8049552c9e5&mKey=%7b6B114A1D-85A4-4054-A83B-04D8B9B8749F%7d
http://www.natap.org/2012/ICAAC/ICAAC_06.htm
http://i-base.info/htb/20381

Raffi F et al. Once-daily dolutegravir (DTG; S/GSK1349572) is non-inferior to raltegravir (RAL) in antiretroviral-naive adults: 48 week results from SPRING-2 (ING113086). 19th International AIDS Conference. 22-27 July 2012, Washington. Late breaker oral presentation THLBB04.
http://pag.aids2012.org/abstracts.aspx?aid=20990

National Institutes of Health (U.S.). A trial comparing GSK1349572 50 mg plus abacavir/lamivudine once daily to Atripla (also called the SINGLE trial). Available from:http://clinicaltrials.gov/ct2/show/NCT01263015.

Stellbrink HJ, Reynes J, Lazzarin A, et al. Dolutegravir in combination therapy exhibits rapid and sustained antiviral response in ARV-naïve adults: 96-week results from SPRING-1 (ING112276) (Abstract 102LB). Paper presented at: 19th Conference on Retroviruses and Opportunistic Infections; 2012 March 5–8; Seattle, WA. Available from:http://www.retroconference.org/2012b/Abstracts/45432.html

DOXOFYLLINE

GENERIC, Uncategorized 1 Response »

Jan 262014

DOXOFYLLINE

LAUNCHED 1987, Istituto Biologico Chemioterapico ABC

69975-86-6 CAS NO

7-(1,3-dioxolan-2-ylmethyl)-1,3-dimethylpurine-2,6-dione

1H-Purine-2,6-dione, 3,7-dihydro-7-(1,3-dioxolan-2-ylmethyl)-1,3-dimethyl- (9CI)

7-(1,3-Dioxolan-2-ylmethyl)-3,7-dihydro-1,3-dimethyl-1H-purine-2,6-dione; 7-[1,3-(Dioxolan-d4)-2-ylmethyl)]theophylline; 2-(7�-Theophyllinemethyl)-1,3- dioxolane; ABC 12/3; ABC 1213; Ansimar; Dioxyfilline; Doxophylline; Maxivent; Ventax;

Synonyms

2-(7′-Teofillinmetil)-1,3-diossolano
2-(7′-Teofillinmetil)-1,3-diossolano [Italian]
2-(7′-Theophyllinemethyl)-1,3-dioxolane
5-26-14-00120 (Beilstein Handbook Reference)
7-(1,3-Dioxolan-2-ylmethyl)theophylline

Formula	C₁₁H₁₄N₄O₄
Mol. mass	266.25 g/mol

ABC 12/3
Ansimar
BRN 0561195
Dioxyfilline
Doxofilina
Doxofilina [INN-Spanish]
Doxofylline
Doxofyllinum
Doxofyllinum [INN-Latin]
Doxophylline
EINECS 274-239-6
Maxivent
UNII-MPM23GMO7Z
Ventax

Doxofylline (INN), (also known as doxophylline) is a xanthine derivative drug used in the treatment of asthma.^[1]

Doxofylline is a xanthine molecule that appears to be both bronchodilator and anti-inflammatory with an improved therapeutic window over conventional xanthines such as Theophylline and the evidence supporting the effects of Doxofylline in the treatment of lung diseases

It has antitussive and bronchodilator^[2] effects, and acts as aphosphodiesterase inhibitor.^[3]

In animal and human studies, it has shown similar efficacy to theophylline but with significantly fewer side effects.^[4]

Unlike other xanthines, doxofylline lacks any significant affinity for adenosine receptorsand does not produce stimulant effects. This suggests that its antiasthmatic effects are mediated by another mechanism, perhaps its actions on phosphodiesterase.^[1]

Doxofylline, [7-(1, 3-dioxolan-2-ylmethyl)-3, 7-dihydro-1, 3-dimethyl-1H-purine-2, 6-dione] is a new bronchodilator xanthine based drug which differs from theophylline by the presence of dioxalane group at position 7. It is used in the treatment of bronchial asthma, chronic obstructive pulmonary disease (COPD), and chronic bronchitis . The mechanism of action is similar to that of theophylline in that it inhibits phosphodiesterase (PDE-IV), thereby preventing breakdown of cyclic adenosine monophosphate (cAMP). Increase in cAMP inhibits activation of inflammatory cells resulting in bronchodilating effect [52]. In contrast to theophylline, doxofylline has very low affinity towards adenosine A1 and A2 receptors which explain its better safety profile

Doxofylline (7-(l,3-dioxalan-2-ylmethyl)-theophylline) is a drug derived from theophylline which is used in therapy as a bronchodilator, with anti-inflammatory action, in reversible airway obstruction. It is commonly administered in doses ranging from 800 to 1200 mg per day, orally, according to a dosage which provides for the intake of two to three dosage units per day in order to maintain therapeutically effective haematic levels. The doxofylline tablets commercially available generally contain 400 mg of active ingredient and release almost all the drug within one hour from intake. The half- life of the drug is around 6-7 hours and for this reason several administrations are required during the 24-hour period.

Obviously a drop in haematic concentration of the drug in an asthmatic patient or patient suffering from COPD (chronic obstructive pulmonary disease) can result in serious consequences, in which case the patient must have recourse to rescue medication, such as salbutamol inhalers.

Pharmaceutical techniques for obtaining the modified release of drugs have been known for some time, but no modified release formulation of doxofylline is known. In fact the present inventors have observed that there are significant difficulties in the production of a doxofylline formula that can be administered only once a day and in particular have encountered problems correlated with bioequivalence.

Various attempts to formulate doxofylline in modified release systems, with different known polymers, have not provided the desired results, i.e. a composition that can be administered once a day, bio equivalent to the plasmatic concentration obtained with the traditional compositions currently on sale. In fact currently, dosage units containing 400 mg of active ingredient are currently administered two/three times a day for a daily average of approximately 1000 mg of active ingredient, a dosage considered necessary to maintain the therapeutic haematic levels of doxofylline.

Such a dosage unit is currently marketed by Dr. Reddy’s Laboratories Ltd as DOXOBID and has the following quali-quantitative composition: doxofylline (400 mg), colloidal silicon dioxide (13 mg), corn starch (63 mg), mannitol (40 mg), povidone (7 mg), microcrystalline cellulose (64 mg), talc (30 mg), magnesium stearate (3 mg) and water (0.08 ml).

Xanthine is a dioxypurine that is structurally related to uric acid. Xanthine can be represented by the following structure:

Caffeine, theophylline and theobromine are methylated xanthines. Methylated xanthines such as caffeine and theophylline are typically used for their bronchodilating action in the management of obstructive airways diseases such as asthma. The bronchodilator effects of methylxanthines are thought to be mediated by relaxation of airway smooth muscle. Generally, methylxanthines function by inhibiting cyclic nucleotide phosphodiesterases and antagonizing receptor-mediated actions of adenosine.

Theophylline can be represented by the following structure:

However, when administered intravenously or orally, theophylline has numerous undesired or adverse effects that are generally systemic in nature. It has a number of adverse side effects, particularly gastrointestinal disturbances and CNS stimulation. Nausea and vomiting are the most common symptoms of theophylline toxicity. Moderate toxicity is due to relative epinephrine excess, and includes tachycardia, arrhythmias, tremors, and agitation. Severe toxicity results in hallucinations, seizures, dysrhythmias and hypotension. The spectrum of theophylline toxicity can also include death.

Furthermore, theophylline has a narrow therapeutic range of serum concentrations above which serious side effects can occur. The pharmacokinetic profile of theophylline is dependent on liver metabolism, which can be affected by various factors including smoking, age, disease, diet, and drug interactions.

Generally, the solubility of methylxanthines is low and is enhanced by the formation of complexes, such as that between theophylline and ethylenediamine (to form aminophylline). The formation of complex double salts (such as caffeine and sodium benzoate) or true salts (such as choline theophyllinate) also enhances aqueous solubility. These salts or complexes dissociate to yield the parent methylxanthine when dissolved in aqueous solution. Although salts such as aminophylline have improved solubility over theophylline, they dissociate in solution to form theophylline and hence have similar toxicities.

Dyphylline is a covalently modified derivative of xanthine (1,3, -dimethyl-7-(2,3-dihydroxypropl)xanthine. Because it is covalently modified, dyphylline is not converted to free theophylline in vivo. Instead, it is absorbed rapidly in therapeutically active form. Dyphylline has a lower toxicity than theophylline. Dyphylline can be represented by the following structure:

Dyphylline is an effective bronchodilator that is available in oral and intramuscular preparations. Generally, dyphylline possesses less of the toxic side effects associated with theophylline.

U.S. Pat. No. 4,031,218 (E1-Antably) discloses the use of 7-(2,3-dihydroxypropyl)-1,3-di-n-propylxanthine, a derivative of theophylline, as a bronchodilator. U.S. Pat. No. 4,341,783 (Scheindlin) discloses the use of dyphylline in the treatment of psoriasis and other diseases of the skin by topical administration of dyphylline. U.S. Pat. No. 4,581,359 (Ayres) discloses methods for the management of bronchopulmonary insufficiency by administering an N-7-substituted derivative of theophylline, including dyphylline, etophylline, and proxyphylline.

At present, domestic synthetic Doxofylline composed of two main methods: one is by the condensation of theophylline prepared from acetaldehyde and ethylene glycol, but this method is more complex synthesis of acetaldehyde theophylline, require high periodate oxidation operation. Another is a halogenated acetaldehyde theophylline and ethylene glycol is prepared by reaction of an organic solvent, the method were carried out in an organic solvent, whereby the product Theophylline caused some pollution, conducive to patients taking.

current domestic Doxofylline synthetic methods reported in the literature are: 1, CN Application No. 94113971.9, the name “synthetic drugs Doxofyllinemethod” patents, the patent is determined by theophylline with a 2 – (halomethyl) -1,3 – dimethoxy-dioxolane in a polar solvent, with a base made acid absorbent,Doxofylline reaction step. 2, CN Application No. 97100911.2, entitled “Synthesis of Theophylline,” the patent, the patent is obtained from 7 – (2,2 – dialkoxy-ethyl) theophylline with ethylene glycol in N, N-dimethylformamide solvent with an alkali metal carbonate to make the condensing agent, p-toluenesulfonic acid catalyst in the condensation Doxofylline.

Doxofylline of xanthine asthma drugs, and its scientific name is 7 – (1,3 – dioxolan – ethyl methyl) -3,7 – dihydro-1,3 – dimethyl-1H – purine-2 ,6 – dione. The drug developed by the Italian Roberts & Co. in 1988, listed its tablet tradename Ansimar. This product is compared with similar asthma drugs, high efficacy, low toxicity, oral LD50 in mice is 1.5 times aminophylline, non-addictive. Adenosine and its non-blocking agents, it does not produce bronchial pulmonary side effects, no aminophylline like central and cardiovascular system. U.S. patent (US4187308) reported the synthesis of doxofylline, theophylline and acetaldehyde from ethylene glycol p-toluenesulfonic acid catalyst in the reaction of benzene as a solvent Doxofylline. Theophylline acetaldehyde by the method dyphylline derived reaction with a peroxy periodate or 7 – (2,2 – dialkoxy-ethyl) ammonium chloride aqueous solution in the decomposition of theophylline converted to acetaldehyde theophylline . Former method is relatively complex, and the high cost of using periodic acid peroxide, low yield after France. And theophylline acetaldehyde and ethylene glycol solvent used in the reaction of benzene toxicity, harm to health, and the yield is low, with an average around 70%, not suitable for industrial production.

SYN 1

Theophylline-7-acetaldehyde (I) could react with ethylene glycol (II) in the presence of p-toluenesulfonic acid in refluxing benzene to produce Doxofylline.

SYN 2

Doxofylline can be prepared by N-alkylation of theophylline (I) with bromoacetaldehyde ethylene glycol acetal (II) using Na2CO3 in refluxing H2O (1).

.…………………………………….

Synthesis

US4187308

EXAMPLE

A mixture of 15 g of theophyllineacetic aldehyde, 30 ml of ethylene glycol and 1.5 g of p-toluenesulphonic acid in 600 ml of benzene is heated under reflux in a flask provided with a Marcusson apparatus.

After two hours the separation of the water is complete.

The reaction mixture is washed with 200 ml of a 3.5% aqueous solution of sodium bicarbonate.

The organic phase is dried and concentrated to dryness under reduced pressure, to leave a product residue which is taken up in ethyl ether, separated by filtration and purified by ethanol.

2-(7′-theophyllinemethyl)-1,3-dioxolane is obtained.

M.P. 144

Average yield 70%

Analysis: C.sub.11 H.sub.14 N.sub.4 O.sub.4 : M.W. 266.26: Calculated: C%, 49.62; H%, 5.30; N%, 21.04. Found: C%, 49.68; H%, 5.29; N%, 21.16.

………………………………..

CN102936248A

the reaction is:

a, anhydrous theophylline and bromoacetaldehyde ethylene glycol as the basic raw material, purified water as a solvent with anhydrous sodium carbonate as acid-binding agent;

NMR

Doxofylline

UV (95% C2H5OH, nm) λmax273 (ε9230); λmin244 (ε2190)

IR (KBr, cm-1) 1134 (CO); 1233 (CN) ; 1547 (C = N); 1656 (C = C); 1700 (C = O); 2993 (CH)

1H-NMR [CDCl3, δ (ppm)] 3.399 (s, 3H, N-CH3); 3.586 (S, 3H, N-CH3); 3.815-3.885 (m, 4H, OCH2 × 2); 4.581 (d, 2H, CH2); 5.211 (t, 1H, CH ); 7.652 (S, 1H, CH = N)

13C-NMR [CDCL3, δ (ppm)] 27.88 (CH3); 29.69 (CH3); 47.87 (CH2); 65.37 ( OCH2); 100.76 (CH); 107.26 (C = C); 142.16 (CH = N); 148.22 (C = C); 151.59 (C = O); 155.25 ( C

……………………………

HPLC

http://www.scipharm.at/download.asp?id=1401

…………………..

Cirillo R, Barone D, Franzone JS (1988). “Doxofylline, an antiasthmatic drug lacking affinity for adenosine receptors”. Arch Int Pharmacodyn Ther 295: 221–37.PMID 3245738.
Poggi R, Brandolese R, Bernasconi M, Manzin E, Rossi A (October 1989). “Doxofylline and respiratory mechanics. Short-term effects in mechanically ventilated patients with airflow obstruction and respiratory failure”. Chest 96 (4): 772–8.doi:10.1378/chest.96.4.772. PMID 2791671.
Dini FL, Cogo R (2001). “Doxofylline: a new generation xanthine bronchodilator devoid of major cardiovascular adverse effects”. Curr Med Res Opin 16 (4): 258–68.doi:10.1185/030079901750120196. PMID 11268710.
Sankar J, Lodha R, Kabra SK (March 2008). “Doxofylline: The next generation methylxanthine”. Indian J Pediatr 75 (3): 251–4. doi:10.1007/s12098-008-0054-1.PMID 18376093.
Dali Shukla, Subhashis Chakraborty, Sanjay Singh & Brahmeshwar Mishra. Doxofylline: a promising methylxanthine derivative for the treatment of asthma and chronic obstructive pulmonary disease. Expert Opinion on Pharmacotherapy. 2009; 10(14): 2343-2356, DOI 10.1517/14656560903200667, PMID 19678793
Farmaco, Edizione Scientifica, 1981 , vol. 36, 3 pg. 201 – 219, mp 144 – 144.5 °C
Drugs Fut 1982, 7(5): 301

US6313131	16 feb 2000	6 nov 2001	Upsher-Smith Laboratories, Inc.	Method of kidney treatment
US6348470 *	20 maart 1998	19 feb 2002	Korbonits Dezsoe	Antitussive compositions
US6423719	16 feb 2000	23 juli 2002	Upsher-Smith Laboratories, Inc.	Method for treating benign prostate hyperplasia
CN101647776B	2 sept 2009	20 april 2011	吴光彦	Doxofylline venous injection with small volume as well as preparation method and quality control method thereof
DE3114130A1 *	8 april 1981	28 jan 1982	Abc Ist Biolog Chem Spa	Neue theophyllinylmethyldioxolan-derivate, verfahren zu ihrer herstellung und sie enthaltende pharmazeutische ansaetze
EP0272596A2 *	16 dec 1987	29 juni 1988	ISTITUTO BIOLOGICO CHEMIOTERAPICO “ABC” S.p.A.	Theophyllinemethyldithiolan and theophyllinemethyldithianyl derivates, a method for their preparation and pharmaceutical compositions in which they are included
WO2011146031A1	16 mei 2011	24 nov 2011	Bilgic Mahmut	Pharmaceutical composition comprising n- acetylcysteine and a xanthine
WO2013055302A1	14 mei 2012	18 april 2013	Mahmut Bilgic	Effervescent composition comprising n- acetylcysteine and doxophylline or theophylline

………………………………………………………………………………………..

I n case Images are blocked on your computer, VIEW AT

14-chapter 4.pdf – Shodhganga

shodhganga.inflibnet.ac.in/bitstream/10603/9713/…/14-chapter%204.pdf‎

Although various bioanalytical methods for estimation of doxofylline in …. 1H and 13C-NMR spectra of doxofylline and its degradation products were recorded by….. CLICK ABOVE

SPECTRAL DATA

DOXOFYLLINE
The ESI mass spectrum exhibited a protonated molecular ion peak at m/z 267 in positive ion mode indicating the molecular weight of 266. The tandem mass spectrum showed the fragment ions m/z 223, 181.2, 166.2, 138.1, 124.1 and 87.1.

Inline image 2

Inline image 5

Inline image 6

The FT-IR spectrum, two strong peaks at 1697cm-1 and 1658cm-1 indicated presence of two carbonyl groups. A strong peak at frequency 1546cm-1 indicated presence of C=N stretch. A medium peak at 1232cm-1 was due to C-O stretch

Inline image 3

FT IR

1H and 13C-NMR spectra of doxofylline and its degradation products were recorded by using Bruker NMR 300MHz instrument with a dual broad band probe and z-axis gradients. Spectra were recorded using DMSO-d6 as a solvent and tetramethylsilane as an internal standard.
4.2.6 Validation

Inline image 1

1H NMR

Inline image 4

13 C NMR

COMPARISONS

Inline image 9

Inline image 8

Inline image 7

AVANAFIL

GENERIC, Uncategorized Comments Off

Jan 252014

AVANAFIL

A phosphodiesterase (PDE5) inhibitor, used to treat erectile dysfunction.

fish spelling out Welcome

Avanafil is a new phosphodiesterase-5 inhibitor that is faster acting and more selective than other drugs belonging to the same class. Chemically, it is a derivative of pyrimidine and is only available as the S-enantiomer. FDA approved on April 27, 2012.

CAS RN: 330784-47-9
4-{[(3-chloro-4-methoxyphenyl)methyl]amino}-2-[(2S)-2-(hydroxymethyl)pyrrolidin-1-yl]-N-(pyrimidin-2-ylmethyl)pyrimidine-5-carboxamide

(S)-2-(2-Hydroxymethyl-1-pyrrolidinyl)-4-(3-chloro-4-methoxybenzylamino)-5-[(2-pyrimidinylmethyl)carbamoyl]pyrimidine

4-[[(3-Chloro-4-methoxyphenyl)methyl]amino]-2-[(2S)-2-(hydroxymethyl)-1-pyrrolidinyl]-N-(2-pyrimidinylmethyl)-5-pyrimidinecarboxamide

TA 1790

Molecular Formular: C23H26ClN7O3

Molecular Mass: 483.95064

Stendra
TA 1790
TA-1790
UNII-DR5S136IVO
NDA 202276

INNOVATOR — VIVUS

APPROVED FDA 27/4/2-12

Patent No	Patent Expiry	patent use code
6656935	Sep 13, 2020	U-155
7501409	May 5, 2023

U 155… TREATMENT OF ERECTILE DYSFUNCTION

Exclusivity Code	Exclusivity_Date
NCE	Apr 27, 2017

Stendra (avanafil) was given the green light by the US Food and Drug Administration 27/4/2012, but there has been no launch yet as Vivus has been seeking a partner. The latest data should be attractive to potential suitors and could help Stendra take on other phosphodiesterase type 5 (PDE5) inhibitors, notably Pfizer’s Viagra (sildenafil) but also Eli Lilly’s Cialis (tadalafil) and Bayer’s Levitra (vardenafil).

read all at

http://www.pharmatimes.com/Article/13-06-20/Vivus_ED_drug_gets_to_work_in_less_than_15_mins.aspx

STENDRA (avanafil) is a selective inhibitor of cGMP-specific PDE5.

Avanafil is designated chemically as (S)-4-[(3-Chloro-4-methoxybenzyl)amino]-2-[2-(hydroxymethyl)-1-pyrrolidinyl]-N-(2pyrimidinylmethyl)-5-pyrimidinecarboxamide and has the following structural formula:

STENDRA™ (avanafil)Structural Formula Illustration

Avanafil occurs as white crystalline powder, molecular formula C23H26ClN7O3 and molecular weight of 483.95 and is slightly soluble in ethanol, practically insoluble in water, soluble in 0.1 mol/L hydrochloric acid. STENDRA, for oral administration, is supplied as oval, pale yellow tablets containing 50 mg, 100 mg, or 200 mg avanafil debossed with dosage strengths. In addition to the active ingredient, avanafil, each tablet contains the following inactive ingredients: mannitol, fumaric acid, hydroxypropylcellulose, low substituted hydroxypropylcellulose, calcium carbonate, magnesium stearate, and ferric oxide yellow.

2D image of a chemical structure AVANAFIL

Avanafil is a PDE5 inhibitor approved for erectile dysfunction by FDA on April 27, 2012 ^[1] and by EMA on June 21, 2013.^[2] Avanafil is known by the trademark names Stendra and Spedra and was developed by Vivus Inc. In July 2013 Vivus announced partnership with Menarini Group, which will commercialise and promote Spedra in over 40 European countries plus Australia and New Zealand.^[3] Avanafil acts by inhibiting a specificphosphodiesterase type 5 enzyme which is found in various body tissues, but primarily in the corpus cavernosum penis, as well as the retina. Other similar drugs are sildenafil, tadalafil and vardenafil. The advantage of avanafil is that it has very fast onset of action compared with other PDE5 inhibitors. It is absorbed quickly, reaching a maximum concentration in about 30–45 minutes.^[4] About two-thirds of the participants were able to engage in sexual activity within 15 minutes.^[4]

Avanafil is a highly selective PDE5 inhibitor that is a competitive antagonist of cyclic guanosine monophosphate. Specifically, avanafil has a high ratio of inhibiting PDE5 as compared with other PDE subtypes allowing for the drug to be used for ED while minimizing adverse effects. Absorption occurs quickly following oral administration with a median Tmax of 30 to 45 minutes and a terminal elimination half-life of 5 hours. Additionally, it is predominantly metabolized by cytochrome P450 3A4. As such, avanafil should not be co-administered with strong cytochrome P450 3A4 inhibitors. Dosage adjustments are not warranted based on renal function, hepatic function, age or gender. Five clinical trials suggest that avanafil 100 and 200 mg doses are effective in improving the Sexual Encounter Profile and the Erectile Function Domain scores among men as part of the International Index of Erectile Function. A network meta-analysis comparing the PDE5 inhibitors revealed avanafil was less effective on Global Assessment Questionnaire question 1 while safety data indicated no major differences among the different PDE5 inhibitors. The most common adverse effects reported from the clinical trials associated with avanafil were headache, flushing, nasal congestion, nasopharyngitis, sinusitis, and dyspepsia.

A “phosphodiesterase type 5 inhibitor” or “PDE5 inhibitor” refers to an agent that blocks the degradative action of phosphodiesterase type 5 on cyclic GMP in the arterial wall smooth muscle within the lungs and in the smooth muscle cells lining the blood vessels supplying the corpus cavernosum of the penis. PDE5 inhibitors are used for the treatment of pulmonary hypertension and in the treatment of erectile dysfunction. Examples of PDE5 inhibitors include, without limitation, tadalafil, avanafil, lodenafil, mirodenafil, sildenafil citrate, vardenafil and udenafil and pharmaceutically acceptable salts thereof.

“Avanafil” refers to the chemical compound 4-[(3-Chloro-4-methoxybenzyl)amino]-2-[2-(hydroxymethyl)-1-pyrrolidinyl]-N-(2-pyrimidinylmethyl)-5-pyrimidinecarboxamide, and its pharmaceutically acceptable salts. Avanafil is described in Limin M. et al., (2010) Expert Opin Investig Drugs, 19(11):1427-37. Avanafil has the following chemical formula:

Avanafil is being developed for erectile dysfunction. Avanafil currently has no trademarked term associated with it but it is being developed by Vivus Inc.

…………………………………

DESCRIPTION IN A PATENT

US6797709

EXAMPLE 92-145

The corresponding starting compounds are treated in a similar manner to give the compounds as listed in the following Table 7.

TABLE 7

Amorphous MS(m/z): 484(MH⁺)

ENTRY 98 IS AVANAFIL

…………………………………………………….

/CN103254180A

The invention discloses a preparation method of Avanafil (Avanafil, I), which comprises the following steps: carrying out a substitution reaction on 6-amino-1, 2-dihydro pyrimidine-2-keto-5-carboxylic acid ethyl ester (XII) and 3-chloro-4-methoxy benzyl chloride (XIII) so as to obtain 6-(3-chloro-4-methoxy benzyl amino)-1, 2-dihydro pyrimidine-2-keto-5-carboxylic acid ethyl ester (IXV); carrying out condensation on the compound (IXV) and S-hydroxymethyl pyrrolidine (II) so as to generate 4-[(3-chloro-4-methoxy benzyl) amino]-2-[2-(hydroxymethyl)-1-pyrrole alkyl] pyrimidine-5-carboxylic acid ethyl ester (XI); and carrying out hydrolysis on the compound (XI) and then carrying out an acylation reaction on the compound (XI) and the compound (XI) so as to obtain Avanafil (I). The preparation method is simple in process, economic and environmental-friendly, suitable for the requirements of industrialization amplification.

……………………………………………………

/CN103265534A

The invention discloses a method for preparing avanafil (Avanafil, I). The method comprises the steps of taking cytosine as an initial material; and orderly carrying out replacement, halogen addition and condensation reaction on a side chain 3-chlorine-4-methoxy benzyl halide (III), N-(2-methylpyrimidine) formamide (IV) and S-hydroxymethyl pyrrolidine (II), so as to obtain a target product avanafil (I). The preparation method is available in material, concise in technology, economic and environment-friendly, and suitable for the demands of industrial amplification.

…………………………………………………….

SYNTHESIS

Avanafil can be synthesized from a benzylamine derivative and a pyrimidine derivative REF 5:Yamada, K.; Matsuki, K.; Omori, K.; Kikkawa, K.; 2004, U.S. Patent 6,797,709

………………………………………………………

SYNTHESIS

A cutting that phenanthrene by a methylthio urea ( a ) and ethoxy methylene malonate ( 2 ) cyclization of 3 , chloride, phosphorus oxychloride get 4 , 4 with benzyl amine 5 occurred SNAr the reaction product after oxidation with mCPBA 6 . In pyrimidine, if the 2 – and 4 – positions are active simultaneously the same leaving group in the case, SNAr reaction occurs preferentially at 4 – position, but does not guarantee the 2 – side reaction does not occur. Here is an activity of the poor leaving group sulfide spans 2 – bit, and a good leaving group active chlorine occupy four – position, thus ensuring a high regioselectivity of the reaction. 4 – position after completion of the reaction, then the 2 – position of the group activation, where sulfide sulfoxide better than the leaving group. Amino alcohols 7 and 6 recurrence SNAr reaction 8 , 8 after alkaline hydrolysis and acid alpha amidation get that phenanthrene.

AVANAFIL

…………………………….

FDA approves Stendra for erectile dysfunction” (Press release). Food and Drug Administration (FDA). April 27, 2012.
http://www.ema.europa.eu/ema/index.jsp?curl=pages/medicines/human/medicines/002581/human_med_001661.jsp&mid=WC0b01ac058001d124
http://ir.vivus.com/releasedetail.cfm?releaseid=775706
Kyle, Jeffery; Brown, Dana (2013). “Avanafil for Erectile Dysfunction”. Annals of Pharmacotherapy (Sage Publishing). doi:10.1177/1060028013501989. Retrieved 28 September 2013.
Yamada, K.; Matsuki, K.; Omori, K.; Kikkawa, K.; 2004, U.S. Patent 6,797,709
- Peterson CA. Hemodynamic effect of avanafil and glyceryl trinitrate coadministration. , Drugs Context , Volume 2013 , 2013 Feb 26
- Gur S. The Effect of Intracavernosal Avanafil, a Newer Phosphodiesterase-5 Inhibitor, on Neonatal Type 2 Diabetic Rats With Erectile Dysfunction. , Urology , 2013 Dec 9
- Hill JK. Avanafil for erectile dysfunction. , Ann Pharmacother , Volume 47 , Issue 10 , 2013 Oct
- Sanford M. Avanafil: a review of its use in patients with erectile dysfunction. , Drugs Aging , Volume 30 , Issue 10 , 2013 Oct
- Hellstrom WJ. PDE5 inhibitors: considerations for preference and long-term adherence. , Int J Clin Pract , Volume 67 , Issue 8 , 2013 Aug
- Aversa A. An update on pharmacological treatment of erectile dysfunction with phosphodiesterase type 5 inhibitors. , Expert Opin Pharmacother , Volume 14 , Issue 10 , 2013 Jul
- Oelke M. Phosphodiesterase inhibitors in clinical urology. , Expert Rev Clin Pharmacol , Volume 6 , Issue 3 , 2013 May
- Kukreja RC. Sildenafil and cardioprotection. , Curr Pharm Des , Volume 19 , Issue 39 , 2013
- Day WW. An open-label, long-term evaluation of the safety, efficacy and tolerability of avanafil in male patients with mild to severe erectile dysfunction. , Int J Clin Pract, Volume 67 , Issue 4 , 2013 Apr
- Tang J. Comparative effectiveness and safety of oral phosphodiesterase type 5 inhibitors for erectile dysfunction: a systematic review and network meta-analysis. , Eur Urol , Volume 63 , Issue 5 , 2013 May

United States	APPROVED 6656935	2012-04-27	EXPIRY 2020-09-13
United States	7501409	2012-04-27	2023-05-05

Faster-Working Erectile Dysfunction Drug?. CBS News. November 24, 2009.
Vivus says men taking avanafil were more likely to be ready for sex within 15 minutes. The Gaea Times. January 11, 2010.
“Avanafil is the New Player in The Erectile Dysfunction Field”. June 28, 2011.

• Hatzimouratidis, K., et al.: Drugs, 68, 231 (2008)

US7927623	4-20-2011	Tablets quickly disintegrated in oral cavity
US2010179131	7-16-2010	Combination treatment for diabetes mellitus
US2009215836	8-28-2009	Roflumilast for the Treatment of Pulmonary Hypertension
US2008027037	1-32-2008	Cyclic compounds

US5242391	Oct 30, 1991	Sep 7, 1993	ALZA Corporation	Urethral insert for treatment of erectile dysfunction
US5474535	Jul 19, 1993	Dec 12, 1995	Vivus, Inc.	Dosage and inserter for treatment of erectile dysfunction
US5773020	Oct 28, 1997	Jun 30, 1998	Vivus, Inc.	Treatment of erectile dysfunction
US6656935	Aug 10, 2001	Dec 2, 2003	Tanabe Seiyaku Co., Ltd.	Aromatic nitrogen-containing 6-membered cyclic compounds

EXTRAS

“Tadalafil” or “TAD” is described in U.S. Pat. Nos. 5,859,006 and 6,821,975. It refers to the chemical compound, (6R-trans)-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydro-2-methyl-pyrazino[1′,2′:1,6]pyrido[3,4-b]indole-1,4-dione and has the following chemical formula:

Tadalafil is currently marketed in pill form for treating erectile dysfunction (ED) under the trade name Cialis® and under the trade name Adcirca® for the treatment of PAH.

Avanafil is being developed for erectile dysfunction. Avanafil currently has no trademarked term associated with it but it is being developed by Vivus Inc.

“Lodenafil” refers to the chemical compound, bis-(2-{4-[4-ethoxy-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-benzenesulfonyl]piperazin-1-yl}-ethyl)carbonate and has the following chemical formula:

More information about lodenafil is available at Toque H A et al., (2008) European Journal of Pharmacology, 591(1-3):189-95. Lodenafil is manufactured by Cristália Produtos Químicose Farmacêuticos in Brazil and sold there under the brand-name Helleva®. It has undergone Phase III clinical trials, but is not yet approved for use in the United States by the U.S. FDA.

“Mirodenafil” refers to the chemical compound, 5-Ethyl-3,5-dihydro-2-[5-([4-(2-hydroxyethyl)-1-piperazinyl]sulfonyl)-2-propoxyphenyl]-7-propyl-4H-pyrrolo[3,2-d]pyrimidin-4-one and has the following chemical formula:

More information about mirodenafil can be found at Paick J S et al., (2008) The Journal of Sexual Medicine, 5 (11): 2672-80. Mirodenafil is not currently approved for use in the United States but clinical trials are being conducted.

“Sildenafil citrate,” marketed under the name Viagra®, is described in U.S. Pat. No. 5,250,534. It refers to 1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)phenylsulfonyl]-4-methylpiperazine and has the following chemical formula:

Sildenafil citrate, sold as Viagra®, Revatio® and under various other trade names, is indicated to treat erectile dysfunction and PAH.

“Vardenafil” refers to the chemical compound, 4-[2-Ethoxy-5-(4-ethylpiperazin-1-yl)sulfonyl-phenyl]-9-methyl-7-propyl-3,5,6,8-tetrazabicyclo[4.3.0]nona-3,7,9-trien-2-one and has the following chemical formula:

Vardenafil is described in U.S. Pat. Nos. 6,362,178 and 7,696,206. Vardenafil is marketed under the trade name Levitra® for treating erectile dysfunction.

“Udenafil” refers to the chemical compound, 3-(1-methyl-7-oxo-3-propyl-4,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-N-[2-(1-methylpyrrolidin-2-yl)ethyl]-4-propoxybenzenesulfonamide and has the following chemical formula:

More information about udenafil can be found at Kouvelas D. et al., (2009) Curr Pharm Des, 15(30):3464-75. Udenafil is marketed under the trade name Zydena® but not approved for use in the United States.

Links

ANTHONY MELVIN CRASTO

THANKS AND REGARD’S

DR ANTHONY MELVIN CRASTO Ph.D GLENMARK SCIENTIST , NAVIMUMBAI, INDIA

did you feel happy, a head to toe paralysed man’s soul in action for you round the clock need help, email or call me

amcrasto@gmail.com

MOBILE-+91 9323115463

web link

http://about.me/amcrasto http://anthonymelvincrasto.brandyourself.com/

I was paralysed in dec2007, Posts dedicated to my family, my organisation Glenmark, Your readership keeps me going and brings smiles to my family

Older Entries Newer Entries

WO2010011812A1 *	Jul 23, 2009	Jan 28, 2010	Smithkline Beecham Corporation	Chemical compounds
WO2010011819A1 *	Jul 23, 2009	Jan 28, 2010	Smithkline Beecham Corporation	Chemical compounds

AUTHOR OF THIS BLOG

Chemistry

On Zanamivir

Total Synthesis of Anti-Influenza Agents Zanamivir and Zanaphosphor via Asymmetric Aza-Henry Reaction

Introduction

Immunology

References

Synthesis

Why cubane is stable?

Functional group transformation

The improvement in synthesis of

cubane-1,4-dicarboxylic acid

Pharmaceutical aspect of cubane

Polymers of cubane:

Explosive and fuels:

Is Cubane a really good explosives?

DIFF TYPES

The Amide Activating Group

Cubyl Grignard Reagents

The effect of the presence of electron withdrawing group – Cyanide

A mixture of product formed.

Increased selectivity by adding MgBr2

Now, let us look the main concern of the cubane derivatives–the nitrocubanes.

1,3,5 trinitrocubane and 1,3,5,7 tetranitrocubane(TNC)

Improved synthesis for TNC

In 1993, Bashir-Hashemi showed the cubane-1,3,5,7-tetracarboxylic acid chloride can be formed by applying photochemically induced chlorocarbonyl cation( the Kharasch_Brown Reaction).

More substituted nitrocubanes-

Pentanitrocubane(PNC) and Hexanitrocubane(HNC)

HNC

Synthesis for the last two nitro cubanes- heptanitrocubane and octanitrocubane

HpNC

ONC

Properties of nitrocubane:

dimethyl 1,4-cubanedicarboxylate;

1,4-cubanedicarboxylic acid dimethyl*ester;

CAS 29412-62-2

References

Follow All About Drugs

Increased selectivity by adding MgBr₂

**1,4-cubanedicarboxylic acid dimethyl*ester;**