S-(-)-9-Fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H- benzo[ij]qumorizine-2-carboxylic acid L-arginine salt is a broad-spectrum antibiotic, medically grouped together with the fluoroquinolone class of antibiotics, which is disclosed and claimed in  U.S. patent 6,514,986 B2 as being isolated in a less crystalline anhydrate form and a more crystalline hydrate form.

U.S. patent 6,664,267 describes a crystalline monohydrate form of S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H-benzo[i,j] quinolizine-2-carboxylic acid L-arginine salt that is disclosed as having advantages over the anhydrate and hydrate forms described in US 6,514,986 B2.

SYNTHESIS

A chiral benzoquinolizine-2-carboxylic acid arginine salt active against vancomycin-resistant Staphylococcus aureus
J Med Chem 2005, 48(16): 5232………..http://pubs.acs.org/doi/abs/10.1021/jm050035f

There is an urgent medical need for novel antibacterial agents to treat hospital infections, specially those caused by multidrug-resistant Gram-positive pathogens. The need may also be fulfilled by either exploring antibacterial agents having new mechanism of action or expanding known classes of antibacterial drugs. The paper describes a new chemical entity, compound 21, derived from hitherto little known “floxacin”. The choice of the entity was made from a series of synthesized prodrugs and salts of the active chiral benzoquinolizine carboxylic acid, S-(−)-nadifloxacin. The chemistry, physicochemical characteristics, and essential bioprofile of 21 qualifies it for serious consideration as a novel drug entity against hospital infections of multi-drug-resistant Staphylococcus aureus, and its progress up to clinical phase I trials in humans is described.

S-(−)-9-Fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j]quinolizine-2-carboxylic Acid l-Arginine Salt Tetrahydrate (Crystalline Form) (21). To a three-necked round-bottom flask fitted on an oil bath and equipped with a mechanical stirrer, a thermometer pocket, and a reflux condenser was charged 1 (100 g, 0.278 mol) followed by acetone (300 mL). Stirring was started and to the stirred suspension was charged powderedl-arginine (48.4 g, 0.278 mol) followed by distilled water (250 mL). The reaction mixture was stirred at a temperature between 50 and 60 °C for 1 h to obtain a clear solution. Activated charcoal (3 g) was added to the solution and the solution was filtered hot. To the filtrate was then added acetone (700 mL) and the reaction mixture was allowed to cool to 30−35 °C. The reaction mixture was stirred for an additional 2 h at this temperature. The crystalline solid was filtered under reduced pressure and the wet cake was washed with acetone (100 mL). The resulting solid was dried under vacuum at 65−70 °C to furnish 21 (137 g, 92% yield):

mp 236−240 °C;

1H NMR (DMSO-d6) δ 1.4 (d, 3H, J = 7.0 Hz), 1.5−2.2 (m, 8H), 2.8−4.2 (m, 16H), 4.8 (m, 1H), 7.8 (d, 1H, J = 13.0 Hz), 8.8 (s, 1H). MS (ES+) m/z 535 (M + H).

Anal. (C25H35FN6O6·4H2O) C, H, N. HPLC assay of free base (theoretical free base content) 67.41%, found 67.16%. Estimated l-arginine by HPLC (theoretical l-arginine content) 32.59%, found 32.14%.

S-(−)-Nadifloxacin is S-(−)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-1-yl)-5-methyl-1-oxo-1H,5H-benzo[i,j] quinolizine-2-carboxylic acid (1). Prodrugs and aqueous soluble salts of 1were synthesized and explored for possible use in parenteral or oral formulations………….De Souza, N. J.; Agarwal, S. K.; Patel, M. V.; Bhawsar, S. B.; Beri, R. K.; Yeole, R. D.; Shetty, N.; Khorakiwala, H. F. Chiral Fluoroquinolone Arginine Salt Form. US patent 6,514,986, 2003.

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CN 102532131,

quinolones has now grown to four generations, the first generation to nalidixic acid is represented as the representative of the second generation to PPA, only the Gram-negative bacteria effectively, the third generation is the development of these drugs the peak period, there has been a lot of drugs, and is a broad-spectrum antibiotic, which to norfloxacin, ciprofloxacin and other representatives. The fourth-generation quinolone antibiotics is in the third generation on the basis of a broad spectrum of antibacterial spectrum further expanded to make it available against mycoplasma and chlamydia infections.

[0003] R & D has been relatively popular domestic antibiotics, the most widely used on the market today is the third generation fluoroquinolones. Nadifloxacin developed by the Japanese company Otsuka, belongs to the third-generation quinolone antibacterial drugs, topical treatment of acne and folliculitis. 1993 for the first time in Japan (trade name: Acuatim), 2004 in the German market (trade name: Nadixa), 2005 in China listed (trade name: By Union, ointment).

[0004] nadifloxacin irritation due to its absorption and vascular problems, only made of topical formulations for in vitro Propionibacterium acnes (propionibacterium acnes) caused by acne. Wherein the S-(-) – that is the main role difloxacin isomer, the antibacterial activity of the R-isomer of 64 to 256 times that of racemic 2 times.

[0005] fine that gatifloxacin is S-(-) _ nadifloxacin salt on the basis of the system.Significantly improved solubility nadifloxacin well absorbed by the body, so it retains nadifloxacin broad spectrum antimicrobial, antibacterial activity, especially methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus Effective characteristics (Antimicrobial Agents and Chemotherapy, 2004,3188 ~ 31920; J. Med. Chem. 2005 (48), 5232 ~ 5242). Pre-clinical tests prove that the product on the market anti-methicillin-resistant Staphylococcus aureus Antibiotic better compare the efficacy, including vancomycin, trovafloxacin, quinupristin + dalfopristin, linezolid amine.

[0006] fine molecular structure that gatifloxacin following formula:

[0007]

[0008] S-(-) _ nadifloxacin (C19H21FN2O4) with L-arginine salt, the further improve the play a major role in antibacterial s-(-) – nadifloxacin isomer content, and improved oral bioavailability, so that it can develop an oral or injectable preparations.

[0009] the literature (J. Med. Chem. 2005 (48), 5232 ~ 5242) discloses the synthesis of S_ (_) _ Nadifloxacin-L-arginine salt, S-(-) _ that fluoride gatifloxacin and L-arginine salt in the reaction solvent system, which solvent system is mainly methanol – water system, according to the paper reported in S-(-) – Nadifloxacin-L-arginine salt, yields were and related substances are not high enough.

Example 1

[0026] In equipped with oil bath, magnetic stirrer, thermometer, reflux condenser flask at 25 ° C was added (S) – (-) – nadifloxacin (100. 0g, 278mmol), dioxane ring (300ml), and the reaction solution was added dropwise to the L-arginine 4g, 278mmol) in distilled water (250ml) was added. Then heated to 50_60 ° C stirred 1.5 hours, and then adding activated carbon (3. Og) for 5 minutes, filtered hot, and then added dropwise at 55-60 ° C dioxane (700ml), and the natural cooling to 30 -35 ° C for 2 hours crystallization. The solid was collected by filtration and acetone (IOOml) wash. Dried at room temperature M hours. To give a white solid 137g, yield: 92%.

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WO 2005023805,

Example 1

Preparation of the single crystal of S-(- -9-fluoro-6,7-dihvdro-8-(4-hvdroxypiperidin-l-ylV5- methyl-l-oxo-lH,5H-benzo[^“i,ι^‘lquinolizine-2-carboxylic acid L-arginine salt terahvdrate.

S-(-)-9-Fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H- benzo[i,j]quinolizine-2-carboxylic acid L-arginine salt (1.0 g) was dissolved in a mixture of acetone (40 ml) and water (10 ml) by heating the suspension at 70 °C for 15 minutes. The clear solution thus obtained was left for slow evaporation at room temperature in a beaker covered with a perforated aluminum foil. The crystal formation started after 2 days. Finally the single crystal was selected for X-ray crystal analysis from a cluster left after complete evaporation of the solvent. The ORTEP diagrams are described in Figures 1 and 2.

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WO 2002009758,

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WO 2001085095,

EXAMPLE 1

S-(-)-9-Fluoro-6,7-dihvdro-8-(4-hvdroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H-benzo Ti l quinolizine-2-carboxylic acid arginine salt Synthesis of SubstantiaUy CrystaUine product A solution of L-(+)-arginine (48.372 g, 0.278 mole) in distilled water (600 ml) was added dropwise over a period of 30 min to the stirred solution/suspension of finely powdered S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H-benzo [ij] quinolizine-2-carboxylic acid (100 g, 0.278 mole) in acetone (1250 ml). The obtained clear solution was stirred for 30 min and concentrated on a water bath in vacuum (175 mbar) at 80°C. When product started solidifying, the concentration was carried out in vacuum (50 mbar) at 80°C up to dryness. Hexane (1 liter) was added, the reaction mixture was stirred for 4 hr, the solid thus separated was filtered and dried in vacuum (0.7 mbar) for 12 hrs at 70 °C. Yield 145 g (96.9%), m.p. 238-242 °C, and solubility 6 mg/ml (pH 9.5 buffer solution).

The substantially crystalline S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5- methyl-l-oxo-lH,5H-benzo[i,j]quinolizine-2-carboxylic acid arginine salt prepared according to Example 1 possesses the following properties: a) Crystalline form, with a degree of crystallinity as determined by X-ray powder diffraction and as shown in Fig. 1. , b) A thermogram as determined by Differential scanning calorimetry and as shown in Fig. 3. c) Particle size measured as mean mass diameter (MMD) of 83.92 μm, as determined by laser diffraction technique. d) Density of 0.51 g/cm³ (untapped) and 0.7 g/cm³ (tapped). e) Hygroscopicity of 0% increase of weight upon storage for 14 days up to 22% relative atmospheric humidity as determined gravimetricaUy. f) A content of moisture water of 0.1 % by weight as determined by titration according to Karl Fischer. g) A content of acetone of 0.014 % by weight as determined by gas chromatography

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WO 2000068229

Example 1

S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyI-l-oxo-lH,5H-benzo [ij] quinolizine-2-car boxy lie acid anhydrate

Method A

S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yI)-5-methyl-l-oxo-lH,5H-benzo [ij] quinoIizine-2-carboxylic acid (3.0 g) obtained according to the process described in literature [K Hashimoto et al., Chem.Pharm.Bull.44, 642-5(1996)] was dissolved in acetonitrile (250 ml) at 85 °C. The resulting clear solution was filtered (to remove if any fibrous material is in suspension). The filtrate was concentrated to 125 ml and left at room temperature for crystallization. The crystals thus separated were filtered and dried in a drying cabinet at 40 °C for 2 hr in vacuum at 50 mm of Hg to obtain constant weight. Yield 2.6 g (86%).

Method B:

S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyI-l-oxo-lH,5H-benzo [ij] quinolizine-2-carboxyIic acid (2.0 g) obtained according to the process described in literature [K.Hashimoto etal., Chem.Pharm.Bull.44, 642-5(1996)] was dissolved in ethyl alcohol (95 %; 200 ml) at 80 °C. The obtained clear solution was filtered (to remove if any fibrous material is in suspension), concentrated to 100 ml and left for crystallization. The separated solid was Altered and dried in a drying cabinet at 40 °C for 3 hr in vacuum at 50 mm of Hg to obtain constant weight. Yield 1.7 g (85 %).

M.p.258-62 °C, moisture content 0 % (by Karl Fisher method) [CXJ_D ²⁶ -299°, HPLC purity 99.8%

Example 8

S-(-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyI-l-oxo-lH,5H-benzo [ij] quinolizine-2-carboxylic acid, L-arginine salt 0.75 hydrate

L-(+)-Arginine (0.958 g., 5.5 mmoles) was added in portions to a suspension solution of S- (-)-9-fluoro-6,7-dihydro-8-(4-hydroxypiperidin-l-yl)-5-methyl-l-oxo-lH,5H-benzo [ij] quinoIizine-2-carboxyIic acid 0.2 hydrate (2.0 g., 5.5 mmole) in methanol (400 ml). The obtained solution was concentrated in vacuum to give the desired product as a yellow solid, which was dried at 50 °C at 50 mm/Hg for 5 hours. Yield 3.0 g. (100%), m.p. 220- 223 °C (dec), m/z 535 (M+H), moisture content 2.3% (by Karl Fisher, required 2.46%), [CIJ_D ²⁵ -144 ° (1% methanol c=l), solubility 93 mg/ml.

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Chemical and Pharmaceutical Bulletin
Vol. 44 (1996) No. 4 P 642-645

https://www.jstage.jst.go.jp/article/cpb1958/44/4/44_4_642/_article

A Practical Synthesis of (S)-(-)-Nadifloxacin : Novel Acid-Catalyzed Racemization of Tetrahydroquinaldine Derivative

(S)-(-)-Nadifloxacin [(S)-(-)-9-fluoro-6, 7-dihydro-8-(4-hydroxy-1-piperidyl)-5-methyl-1-oxo-1H, 5H-benzo[i, j]quinolizine-2-carboxylic acid, (S)-(-)-OPC-7251], an antibacterial agent, was synthesized from (S)-(-)-5, 6-difluoro-2-methyl-1, 2, 3, 4-tetrahydroquinoline (DFTQ), which was prepared by the optical resolution of recemic DFTQ with 2, 3-di-O-benzoxyl-L-tartaric acid. Racemization of the undesired enantiomer [(R)-(+)-DFTQ] was studied in the presence of various acids and the best result was obtained in the case of methanesulfonic acid. The absolute configuration of (-)-nadifloxacin was determined as S by X-ray crystallographic analysis.

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