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• Ketoconazole, 1-acetyl-4- [4-[[2-(2,4-dichlorophenyl)-2-[(1H-imidazol-1-yl)-methyl]-1,3-dioxolan-4-yl] methoxy] phenyl] piperazine, is a racemic mixture of the cis enantiomers (-)-(2S, 4R) and (+)-(2R, 4S) marketed as an anti-fungal agent. Ketoconazole inhibits fungal growth through the inhibition of ergosterol synthesis. Ergosterol is a key component of fungal cell walls.
• More recently, ketoconazole was found to decrease plasma cortisol and to be useful, alone and in combination with other agents, in the treatment of a variety of diseases and conditions, including type 2 diabetes, Metabolic Syndrome (also known as the Insulin Resistance Syndrome, Dysmetabolic Syndrome or Syndrome X), and other medical conditions that are associated with elevated cortisol levels. SeeU.S. Patent Nos. 5,584,790 ; 6,166,017 ; and 6,642,236 , each of which is incorporated herein by reference. Cortisol is a stress-related hormone secreted from the cortex of the adrenal glands. ACTH (adenocorticotropic hormone) increases cortisol secretion. ACTH is secreted by the pituitary gland, a process activated by secretion of corticotropin releasing hormone (CRH) from the hypothalamus.
• Cortisol circulates in the bloodstream and activates specific intracellular receptors, such as the glucocorticoid receptor (GR). Disturbances in cortisol levels, synthetic rates or activity have been shown to be associated with numerous metabolic complications, including insulin resistance, obesity, diabetes and Metabolic Syndrome. Additionally, these metabolic abnormalities are associated with substantially increased risk of cardiovascular disease, a major cause of death in industrialized countries. See Mårin P et al., “Cortisol secretion in relation to body fat distribution in obese premenopausal women.” Metabolism 1992; 41:882-886, Bjorntorp, “Neuroendocrine perturbations as a cause of insulin resistance.” Diabetes Metab Res Rev 1999; 15(6): 427-41, and Rosmond, “Role of stress in the pathogenesis of the metabolic syndrome.” Psychoneuroendocrinology 2005; 30(1): 1-10, each of which is incorporated herein by reference.
• While ketoconazole is known to inhibit some of the enzymatic steps in cortisol synthesis, such as, for example, 17α hydroxylase (Wachall et al., “Imidazole substituted biphenyls: a new class of highly potent and in vivo active inhibitors of P450 17 as potential therapeutics for treatment of prostate cancer.” Bioorg Med Chem 1999; 7(9): 1913-24, incorporated herein by reference) and 11b-hydroxylase (Rotstein et al., “Stereoisomers of ketoconazole: preparation and biological activity.” J Med Chem 1992; 35(15): 2818-25) and 11β-hydroxy steroid dehydrogenase (11β-HSD) (Diederich et al., “In the search for specific inhibitors of human 11β-hydroxysteroid-dehydrogenases (11β-HSDs): chenodeoxycholic acid selectively inhibits 11β-HSD-L” Eur J Endocrinol 2000; 142(2): 200-7, incorporated herein by reference) the mechanisms by which ketoconazole decreases cortisol levels in the plasma have not been reported. For example, there is uncertainty regarding the effect of ketoconazole on the 11β-hydroxy steroid dehydrogenase (11β-HSD) enzymes. There are two 11β-HSD enzymes. One of these, 11β-HSD-I, is primarily a reductase that is highly expressed in the liver and can convert the inactive 11-keto glucocorticoid to the active glucocorticoid (cortisol in humans and corticosterone in rats). In contrast, the other, 11β-HSD-II, is primarily expressed in the kidney and acts primarily as an oxidase that converts active glucocorticoid (cortisol in humans and corticosterone in rats) to inactive 11-keto glucocorticoids. Thus, the plasma concentration of active glucocorticoid is influenced by the rate of synthesis, controlled in part by the activity of adrenal 11β-hydroxylase and by the rate of interconversion, controlled in part by the relative activities of the two 11β-HSD enzymes. Ketoconazole is known to inhibit these three enzymes (Diederich et al., supra) and the 2S,4R enantiomer is more active against the adrenal 11β-hydroxylase enzyme than is the 2R,4S enantiomer (Rotstein et al., supra). However, there are no reports describing the effect of the two ketoconazole enantiomers on either of 11β-HSD-I or 11β-HSD-II, so it is not possible to predict what effects, if any, the two different ketoconazole enantiomers will each have on plasma levels of the active glucocorticoid levels in a mammal.
• Ketoconazole has also been reported to lower cholesterol levels in humans (Sonino et al. (1991). “Ketoconazole treatment in Cushing’s syndrome: experience in 34 patients.” Clin Endocrinol (Oxf). 35(4): 347-52; Gylling et al. (1993). “Effects of ketoconazole on cholesterol precursors and low density lipoprotein kinetics in hypercholesterolemia.” J Lipid Res. 34(1): 59-67) each of which is incorporated herein by reference). The 2S,4R enantiomer is more active against the cholesterol synthetic enzyme 14 αlanosterol demethylase than is the other (2R,4S) enantiomer (Rotstein et al infra). However, because cholesterol level in a human patient is controlled by the rate of metabolism and excretion as well as by the rate of synthesis it is not possible to predict from this whether the 2S,4R enantiomer of ketoconazole will be more effective at lowering cholesterol levels.
• The use of ketoconazole as a therapeutic is complicated by the effect of ketoconazole on the P450 enzymes responsible for drug metabolism. Several of these P450 enzymes are inhibited by ketoconazole (Rotsteinet al., supra). This inhibition leads to an alteration in the clearance of ketoconazole itself (Brass et al., “Disposition of ketoconazole, an oral antifungal, in humans.” Antimicrob Agents Chemother 1982; 21(1): 151-8, incorporated herein by reference) and several other important drugs such as Glivec (Dutreix et al., “Pharmacokinetic interaction between ketoconazole and imatinib mesylate (Glivec) in healthy subjects.” Cancer Chemother Pharmacol 2004; 54(4): 290-4) and methylprednisolone (Glynn et al., “Effects of ketoconazole on methylprednisolone pharmacokinetics and cortisol secretion.” Clin Pharmacol Ther 1986; 39(6): 654-9). As a result, the exposure of a patient to ketoconazole increases with repeated dosing, despite no increase in the amount of drug administered to the patient. This exposure and increase in exposure can be measured and demonstrated using the “Area under the Curve” (AUC) or the product of the concentration of the drug found in the plasma and the time period over which the measurements are made. The AUC for ketoconazole following the first exposure is significantly less than the AUC for ketoconazole after repeated exposures. This increase in drug exposure means that it is difficult to provide an accurate and consistent dose of the drug to a patient. Further, the increase in drug exposure increases the likelihood of adverse side effects associated with ketoconazole use.
• [0008]
  Rotstein et al. (Rotstein et al., supra) have examined the effects of the two ketoconazole cis enantiomers on the principal P450 enzymes responsible for drug metabolism and reported “…almost no selectivity was observed for the ketoconazole isomers” and, referring to drug metabolizing P450 enzymes: “[t]he IC50 values for the cis enantiomers were similar to those previously reported for racemic ketoconazole”. This report indicated that both of the cis enantiomers could contribute significantly to the AUC problem observed with the ketoconazole racemate.
• One of the adverse side effects of ketoconazole administration exacerbated by this AUC problem is liver reactions. Asymptomatic liver reactions can be measured by an increase in the level of liver specific enzymes found in the serum and an increase in these enzymes has been noted in ketoconazole treated patients (Sohn, “Evaluation of ketoconazole.” Clin Pharm 1982; 1(3): 217-24, and Janssen and Symoens, “Hepatic reactions during ketoconazole treatment.” Am J Med 1983; 74(1B): 80-5, each of which is incorporated herein by reference). In addition 1:12,000 patients will have more severe liver failure (Smith and Henry, “Ketoconazole: an orally effective antifungal agent. Mechanism of action, pharmacology, clinical efficacy and adverse effects.” Pharmacotherapy 1984; 4(4): 199-204, incorporated herein by reference). As noted above, the amount of ketoconazole that a patient is exposed to increases with repeated dosing even though the amount of drug taken per day does not increase (the “AUC problem”). The AUC correlates with liver damage in rabbits (Ma et al., “Hepatotoxicity and toxicokinetics of ketoconazole in rabbits.” Acta Pharmacol Sin 2003; 24(8): 778-782 incorporated herein by reference) and increased exposure to the drug is believed to increase the frequency of liver damage reported in ketoconazole treated patients.
• Additionally, U.S. Patent No. 6,040,307 , incorporated herein by reference, reports that the 2S,4R enantiomer is efficacious in treating fungal infections. This same patent application also reports studies on isolated guinea pig hearts that show that the administration of racemic ketoconazole may be associated with an increased risk of cardiac arrhythmia, but provides no data in support of that assertion. However, as disclosed in that patent, arrhythmia had not been previously reported as a side effect of systemic racemic ketoconazole, although a particular subtype of arrhythmia, torsades de pointes, has been reported when racemic ketoconazole was administered concurrently with terfenadine. Furthermore several published reports (for example, Morganroth et al. (1997). “Lack of effect of azelastine and ketoconazole coadministration on electrocardiographic parameters in healthy volunteers.” J Clin Pharmacol. 37(11): 1065-72) have demonstrated that ketoconazole does not increase the QTc interval. This interval is used as a surrogate marker to determine whether drugs have the potential for inducing arrhythmia. US Patent Number 6,040,307 also makes reference to diminished hepatoxicity associated with the 2S,4R enantiomer but provides no data in support of that assertion. The method provided in US Patent Number 6,040,307 does not allow for the assessment of hepatoxicity as the method uses microsomes isolated from frozen tissue.

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http://www.google.com/patents/EP1853266B1?cl=en

• DIO-902 is the single enantiomer 2S,4R ketoconazole and is derived from racemic ketoconazole. It is formulated using cellulose, lactose, cornstarch, colloidal silicon dioxide and magnesium stearate as an immediate release 200 mg strength tablet. The chemical name is 2S,4R cis-1-acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl] methoxyl]phenyl] piperazine, the formula is C₂₆H₂₈Cl₂N₄O₄, and the molecular weight is 531.44. The CAS number is 65277-42-1, and the structural formula is provided below. The chiral centers are at the carbon atoms 2 and 4 as marked.

  
• [0132]
  Ketoconazole is an imidazole-containing fungistatic compound. DIO-902 is an immediate release tablet to be taken orally and formulated as shown in the table below.

  Component	Percentage
  2S,4R ketoconazole; DIO-902	50%
  Silicified Microcrystalline Cellulose, NF (Prosolv HD 90)	16.5
  Lactose Monohydrate, NF (316 Fast-Flo)	22.4
  Corn Starch, NF (STA-Rx)	10
  Colloidal Silicon Dioxide, NF (Cab-O-Sil M5P)	0.5
  Magnesium Stearate, NF	0.6

  The drug product may be stored at room temperature and is anticipated to be stable for at least 2 years at 25° C and 50% RH. The drug is packaged in blister packs.

ketoconazole 2S,4R enantiomer

ketoconazole 2S,4S enantiomer

• ketoconazole 2R,4R enantiomer

ketoconazole 2R,4S enantiomer

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Journal of Medicinal Chemistry (Impact Factor: 5.61). 08/1992; 35(15):2818-25. DOI: 10.1021/jm00093a015

http://pubs.acs.org/doi/abs/10.1021/jm00093a015

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Enantioselective separation of ketoconazole enantiomers by membrane extraction

http://www.sciencedirect.com/science/article/pii/S1383586611001638

A new process has been developed to separate ketoconazole (KTZ) enantiomers by membrane extraction, with the oppositely preferential recognition of hydrophobic and hydrophilic chiral selectors in organic and aqueous phases, respectively. This system is established by adding hydrophobic l-isopentyl tartrate (l-IPT) in organic strip phase (shell side) and hydrophilic sulfobutylether-β-cyclodextrin (SBE-β-CD) in aqueous feed phase (lumen side), which preferentially recognizes (+)-2R,4S-ketoconazole and (−)-2S,4R-ketoconazole, respectively. The studies performed involve two enantioselective extractions in a biphasic system, where KTZ enantiomers form four complexes with SBE-β-CD in aqueous phase and l-IPT in organic phase, respectively. The membrane is permeable to the KTZ enantiomers but non-permeable to the chiral selector molecules. Fractional chiral extraction theory, mass transfer performance of hollow fiber membrane, enantioselectivity and some experimental conditions are investigated to optimize the separation system. Mathematical model of I/II = 0.893e^0.039NTU for racemic KTZ separation by hollow fiber extraction, is established. The optical purity for KTZ enantiomers is up to 90% when 9 hollow fiber membrane modules of 30 cm in length in series are used.

• I, (−)-2S,4R-ketoconazole;
• II, (+)-2R,4S-ketoconazole;
• CDs, cyclodextrin derivatives;
• l-IPT, l-isopentyl tartrate;
• d-IPT, d-isopentyl tartrate;
• HP-β-CD, hydroxypropyl-β-cyclodextrin;
• Me-β-CD, methyl-β-cyclodextrin;
• β-CD, β-cyclodextrin;
• NTU, number of transfer units;
• HTU, height of a transfer unit;
• PVDF,polyvinylidene fluoride

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Stereoselective synthesis of both enantiomers of ketoconazole from (R)- and (S)-

• Stereoselective synthesis of both enantiomers of ketoconazole from (R)- and (S)-epichlorohydrin

  Original Research Article

• Pages 1283-1294
• Pelayo Camps, Xavier Farrés, Ma Luisa García, Joan Ginesta, Jaume Pascual, David Mauleón, Germano Carganico

• Bromobenzoates (2R,4R)- and (2S,4S)-18, prepared stereoselectively from (R)- and (S)-epichlorohydrin, were transformed into (2R,4S)-(+)- and (2S,4R)-(−)-Ketoconazole, respectively, following the known synthetic protocols for the racemic mixture.

  

Tetrahedron Asymmetry 1995, 6(6): 1283

Stereoselective syntheses of both enantiomers of ketoconazole (1) from commercially available (R)- or (S)-epichlorohydrin has been developed. The key-step of these syntheses involves the selective substitution of the methylene chlorine atom by benzoate on a mixture of  and  or of their enantiomers, followed by crystallization of the corresponding cis-benzoates, (2S,4R)-18 or(2S,4S)-18, from which (+)- or (−)-1 were obtained as described for (±)-1. The ee’s of (+)- and (−)-ketoconazole were determined by HPLC on the CSP Chiralcel OD-H.

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WO 1996029325

 http://www.google.com/patents/WO1996029325A1?cl=en

The incidence of fungal infections has considerably increased over the last decades. Notwithstanding the utility of the antifungal compounds commercialized in the last 15 years, the investigation in this field is however very extensive. During this time, compounds belonging to the azole class have beer, commercialized for both the topical and oral administrations, such a class including imidazoles as well as 1,2,4-triazoles. Some of these compounds car. show m some degree a low gastrointestinal tolerance as well as hepatotoxycity.

A large number of pharmaceutically active compounds are commercialized as stereoisomeric mixtures. On the other hand, the case in which only one of said stereoisomers is pharmaceutically active is frequent.

The undesired enantiomer has a lower activity and it sometimes may cause undesired side-effects.

Ketoconazole (1-acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2-[(1H-imidazol-1-yl)methyl]-1,3-dioxolane-4-yl]methoxy]phenyl]piperazine), terconazole (1-[4-[[2(2,4-dichlorophenyl)-2-[(1H-1 , 2 ,4-triazol-1-yl)methyl]-1,3-dioxolane-4-yl]methoxy]phenyl]-4-(1-methylethyl)piperazine) and other related azole antifungal drugs contain in their structure a substituted 1,3-dioxolane ring, in which carbon atoms C2 and C4 are stereogenic centres, therefore four possible stereoisomers are possible. These compounds are commercialized in the form or cis racemates which show a higher antifungal activity than the corresponding trans racemates.

The cis homochiral compounds of the present invention, which are intermediates for the preparation of enantiomerically pure antifungal drugs, have been prepared previously in the racemic form and transformed into the different azole antifungal drugs in the racemic form [J. Heeres et al., J . Med . Chem . , 22 , 1003 (1979). J . Med . Chem . , 26, 611 (1983), J . Med . Chem . , 27 , 894 (1984) and US 4,144,346, 4,223,036, 4,358,449 and 4,335,125].

Scheme 1 shows the synthesis described for racemic ketoconazole [J. Heeres et al., J . Med . Chem . , 22 , 1003 (1979)]. Scheme 1

)

The synthesis of racemic terconazole [J. Heeres et al., J. Med . Chem . , 26 , 611 11983)] is similar. differing in the introduction of a 1 H- 1 , 2,4-triazol-1-yl substituent in place of 1H-imidazol-1-yl and in the nature of the phenol used in the last step of the synthetic sequence, which phenol is 1-methylethyl-4-(4- hydroxyphenyl)piperazme instead of 1-acetyl-4-(4-nydroxyphenyl)piperazine.

The preparation of racemic itraconazole [J. Heeres et al., J. Med . Chem. , 27 , 894 (1984)] is similar to that of terconazole, differing only in the nature of the phenol used in the last step of the synthetic sequence.

In the class of azoles containing a 1,3-dioxolane ring and a piperazine ring and moreover they are pure enantiomers, only the preparation of (+)- and (-)-ketoconazole has been described [D. M. Rotstein et al., J. Med . Chem . , 35, 2818 (1992)] (Scheme 2) starting from the tosylate of (+)- and (-) 2,2-dimethyl-1,3-dioxolane-4-methanol.

Scheme 2

This synthesis suffers from a series of drawbacks, namely: a) the use of expensive, high molecular weight starting products which are available only on a laboratory scale, and b) the need for several chromatographies during the process in order to obtain products of suitable purity, which maKes said synthesis economically unattractive and difficult to apply industrially.

Recently (N. M. Gray, WO 94/14447 and WO 94/14446) the use of (-)-ketoconazole and (+)-ketoconazole as antifungal drugs causing less side-effects than (±)-ketoconazole has been claimed.

The industrial preparation of enantiomerically pure antifungal drugs with a high antifungal activity and less side-effects is however a problem in therapy. The present invention provides novel homochiral compounds which are intermediates for the industrial preparation of already known, enantiomerically pure antifungal drugs such as ketoconazole enantiomers, or of others which have not yet been reported in literature, which are described first in the present invention, such as (+)-terconazole and (-)-terconazoie, which show the cited antifungal action, allowing to attain the same therapeutical effectiveness using lower dosages than those required for racemic terconazole

Example 14 : (2S,4R)-(-)-1-acetyl-4-[4-[ [2-(2,4-dichlorophenyl)-2-[(1H-imidazol-1-yl)-methyl]-1,3-dioxolane-4-yl]methoxy]phenyl]piperazine, (2S,4R) -(- )-ketoconazole.

This compound is prepared following the process described above for (2R,4S)-(+)-ketoconazole. Starting from HNa (60-65% dispersion in paraffin, 32 mg, 0.80 mmol), 1-acetyl-4-(4-hydroxyphenyl)piperazine (153 mg, 0.69 mol) and (2S,4S)-(-)-IV (Ar = 2,4-dichlorophenyl, Y = CH, R = CH₃) (250 mg, 0.61 mmol), upon crystallization from an acetone:ethyl acetate mixture, (2S,4R) -(-)-ketoconazole is obtained [(2S,4R)-V Ar = 2,4-dichlorophenyl, Y = CH, Z = COCH₃] (196 mg, 61% yield) as a solid, m.p. 153-155ºC (lit. 155-157ºC); [α]_D ²⁰ = -10.50 (c = 0.4, CHCl₃) (lit. [α]_D ²⁵ = -10.58. c = 0.4, CHCl₃) with e.e. > 99% (determined by HPLC using the chiral stationary phase CHIRALCEL OD-H and ethanol:hexane 1:1 mixtures containing 0.1 % diethylamine as the eluent).

+ KETOCONAZOLE…. UNDESIRED

Example 7: (2 R ,4S)-(+)-1-acetyl-4-[4-[[2-(2,4-dichlorophenyl)-2-[(1H-imidazol-1-yl)methyl]-1,3-dioxolane-4-yl]methoxy]phenyl]piperazine (22, 4 S)-(+)-ketoconazole.

To a suspension of NaH (dispersed in 60-65% paraffin, 19.2 mg, 0.48 mmol) in anhydrous DMSO (3 ml),

1-acetyl-4-(hydroxyphenyl)piperazine (102 mg, 0.46 mmol) is added and the mixture is stirred for 1 hour at room temperature. Then, a solution of (2R,4R) – (+)-IV (Ar = 2,4-dichlorophenyl, Y = CH, R = CH₃) (160 mg, 0.39 mmol) in anhydrous DMSO (5 ml) is added, and the mixture is heated at 80ºC for 4 hours. The reaction mixture is allowed to cool to room temperature, diluted with water

(20 ml) and extracted with CH₂Cl₂ (3 × 25 ml). The combined organic phases are washed with water (3 × 25), dried with Na₂SO₄ and the solvent is evaporated off under vacuum. The oily residue thus obtained is crystallized from an acetone:ethyl acetate mixture to give (2R,4S)-(+)-ketoconazole ( (2R, 4 S) -V , Ar 2,4-dichlorophenyl, Y = CH , Z = COCH₃ ) ( 110 mg , 5 3 % yie ld ) as a white solid, m.p. 155-156°C (lit. 154-156ºC), [α]_D ²⁰ = + 8.99 (c = 0.4, CHCl₃) (lit. [α]_D ²⁵ = + 8.22, c = 0.4, CHCl₃), with e.e. > 99% (determined by HPLC using the chirai stationary phase CHIRALCEL OD-H and ethanol:hexane 1:1 mixtures containing 0.1% of diethylamine, as the eluent; (+)-Ketoconazole retention time 73,28 min. (-)-Ketoconazole, retention time 79.06 min).

IR (KBr), ʋ : 2875, 1645, 1584, 1511, 1462, 1425, 1250, 103S, 313 cm^-1.

¹H NMR (500 MHz, CDCl₃), δ : 2.12 (s, 3H, COCH₃),

3.02 (m, 2H, 3-H₂), 3.05 (m, 2H, 5-H₂), 3.27 (dd, J= 9.5

Hz, J’=7.0 Hz, 1H) and 3.70 (dd, J=9.5 Hz, J’=5.0 Hz, 1 H) (4″-CH₂), 3.60 (m, 2H, 6-H₂), 3.76 (m, 2H, 2-H₂), 3.73 (dd, J=8.0 Hz, J’=5.0 Hz, 1H) and 3.86 (dd, J=8.0 Hz, J’=6.5 Hz, 1H) (5″-H₂), 4.34 (m, 1H, 4″-H), 4.40 (d, J=15.0 Hz, 1H) and 5.00 (d, J=15.0 Hz, 1H) (CH₂-N), 4.34

(m, 1H, 4″-H), 6.76 [d, J = 9.0 Hz, 2H, 2′(C6′ )-H], 6.88

[d, J=9.0 Hz, 2H, C3′(C5)-H], 6.96 (s, 1H, imidazole 5- H), 6.99 (s, 1H, imidazole 4-H), 7.25 (dd, J=8.5 Hz, J’=2.0 Hz, 1H, 5″‘-H), 7.46 (d, J=2.0 Hz, 1H, 3″‘-H),

7.53 (s, 1H, imidazole 2-H), 7.57 (d, J=8.5 Hz, 1H,

6″‘-H).

¹³C NMR (75.4 MHz, CDCI₃), δ : 21.3 (CH₃, COCH₃), 41.4 (CH₂, C₂), 46.3 (CH₂, C6), 50.6 (CH₂, C3), 51.0 (CH₂, C5), 51.2 (CH₂, CH₂-N), 67.6 [CH₂, C5″ and 4″-CH₂), 74.7 (CH, C4″), 108.0 (C, C2″), 115.2 [CH, C2′(6′)], 118.8 [CH, C3′(5′)], 121.2 (CH, imidazole C5), 127.2 (CH, C5″‘), 128.5 (CH, imidazole C4), 129.5 (CH, C6′”), 131.3 (CH, C3″‘), 133.0 (C, C2″‘), 134.6 (C, C1′”), 135.8 (C, C4″‘), 138.8 (CH, imidazole C2), 145.6 (C, C1′), 152.8 (C, C4’), 168.9 (C, CO).

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Experimental and theoretical analysis of the interaction of (+/-)-cis-ketoconazole with beta-cyclodextrin in the presence of (+)-L-tartaric acid
J Pharm Sci 1999, 88(6): 599

Experimental and theoretical analysis of the interaction of (±)-cis-ketoconazole with β-cyclodextrin in the presence of (+)-l-Tartaric acid (pages 599–607)

Enrico Redenti, Paolo Ventura, Giovanni Fronza, Antonio Selva, Silvia Rivara, Pier Vincenzo Plazzi and Marco Mor

Article first published online: 12 JUN 2000 | DOI: 10.1021/js980468o

http://onlinelibrary.wiley.com/doi/10.1021/js980468o/pdf

• Abstract
• PDF(154K)

¹H NMR spectroscopy was used for determining the optical purity of cis-ketoconazole enantiomers obtained by fractional crystallization. The chiral analysis was carried out using β-cyclodextrin in the presence of (+)-l-tartaric acid. The mechanism of the chiral discrimination process, the stability of the complexes formed, and their structure in aqueous solution were also investigated by ¹H and ¹³C chemical shift analysis, two-dimensional NOE experiments, relaxation time measurements, and mass spectrometry experiments. Theoretical models of the three-component interaction were built up on the basis of the available NMR data, by performing a conformational analysis on the relevant fragments on ketoconazole and docking studies on the components of the complex. The model derived from a folded conformation of ketoconazole turned out to be fully consistent with the molecular assembly found in aqueous solution, as inferred from NOE experiments. An explanation of the different association constants for the complexes of the two enantiomers is also provided on the basis of the interaction energies.