Preparation of Single-Enantiomer Biofunctional Molecules with (S)-2-Methoxy-2-(1-naphthyl)propanoic Acid

(RS)-β-Ionol and (RS)-2-methyl-4-octanol were resolved by using (S)-2-methoxy-2-(1-naphthyl)propanoic acid [(S)-MαNP acid]. The specific stereochemistry of each MαNP ester was elucidated by 2D NMR analyses, and shielding by the 1-naphthyl group was observed in both the ¹H- and ¹³C-NMR spectra. Solvolysis of the individual (S)-MαNP esters gave four single-enantiomer alcohols. The normal-phase HPLC elution order of each MαNP ester is also discussed.     

Fiber-based liquid-phase micro-extraction of mebeverine enantiomers followed by chiral high-performance liquid chromatography analysis and its application to pharmacokinetics study in rat plasma

The applicability of two-phase liquid-phase micro-extraction (LPME) in porous hollow polypropylene fiber for the sample preparation and the stereoselective pharmacokinetics of mebeverine (MEB) enantiomers (an antispasmodic drug) in rat after intramuscular administration were studied. Plasma was assayed for MEB enantiomer concentrations using stereospecific high-performance liquid chromatography with ultraviolet detection after a simple, inexpensive, and efficient preconcentration and clean-up hollow fiber-based LPME. Under optimized micro-extraction conditions, MEB enantiomers were extracted with 25 μl of 1-octanol within a lumen of a hollow fiber from 0.5 ml of plasma previously diluted with 4.5 ml alkalized water (pH 10). The chromatographic analysis was carried out through chiral liquid chromatography using a DELTA S column and hexane-isopropyl alcohol (85:15 v/v) containing 0.2% triethylamine as mobile phase. The mean recoveries of (+)-MEB and (-)-MEB were 75.5% and 71.0%, respectively. The limit of detection (LOD) was 3.0 ng/ml with linear response over the concentration range of 10-2500 ng/ml with correlation coefficient higher than 0.993 for both enantiomers. The pharmacokinetic studies showed that the mean plasma levels of (+)-MEB were higher than those of (-)-MEB at almost all time points. Also, (+)-MEB exhibited greater t(max) (peak time in concentration-time profile), C(max) (peak concentration in concentration-time profile), t(1/2) (elimination half-life), and AUC(0-240 min) (area under the curve for concentration versus time) and smaller CL (clearance) and V(d) (apparent distribution volume) than its antipode. The obtained results implied that the absorption, distribution, and elimination of (-)-MEB were more rapid than those of (+)-MEB and there were stereoselective differences in pharmacokinetics.     

Effective use of preparative chiral HPLC in a preclinical drug synthesis

Access to a key 3-aryl-delta-lactone intermediate in enantiopure form using preparative chiral chromatography allowed expedited preparation of an important drug discovery target. A preclinical drug discovery strategy that combines rapid route discovery with effective use of preparative chiral chromatography can result in significant savings of both time and labor.     

Synthesis,Molecular Modeling,and Biological Evaluation of Novel Chiral Thiosemicarbazone Derivatives as Potent Anticancer Agents

A series of new chiral thiosemicarbazones derived from homochiral amines in both enantiomeric forms were synthesized and evaluated for their in vitro antiproliferative activity against A549 (human alveolar adenocarcinoma), MCF‐7 (human breast adenocarcinoma), HeLa (human cervical adenocarcinoma), and HGC‐27 (human stomach carcinoma) cell lines. Some of compounds showed inhibitory activities on the growth of cancer cell lines. Especially, compound 17b exhibited the most potent activity (IC₅₀ 4.6 μM) against HGC‐27 as compared with the reference compound, sindaxel (IC₅₀ 10.3 μM), and could be used as a lead compound to search new chiral thiosemicarbazone derivatives as antiproliferative agents. Chirality 27:177–188, 2015. © 2014 Wiley Periodicals, Inc.     

Stereoselective pharmacokinetics of RS-8359, a selective and reversible MAO-A inhibitor, by species-dependent drug-metabolizing enzymes

RS-8359, (+/-)-4-(4-cyanoanilino)-5,6-dihydro-7-hydroxy-7H-cyclopenta[d]pyrimidine selectively and reversibly inhibits monoamine oxidase A (MAO-A). After oral administration of rac-RS-8359 to rats, mice, dogs, monkeys, and humans, plasma concentrations of the (R)-enantiomer were greatly higher than were those of the (S)-enantiomer in all species studied. The AUC((R)) to AUC((S)) ratios were 2.6 in rats, 3.8 in mice, 31 in dogs, and 238 in monkeys, and the (S)-enantiomer was almost negligible in human plasma. After intravenous administration of RS-8359 enantiomers to rats, the pharmacokinetic parameters showed that the (S)-enantiomer had a 2.7-fold greater total clearance (CL(t)) and a 70% shorter half-life (t(1/2)) than those for the (R)-enantiomer but had no difference in distribution volume (V(d)). No significant difference in the intestinal absorption rate was observed. The principal metabolites were the 2-keto form, possibly produced by aldehyde oxidase, the cis-diol form, and the 2-keto-cis-diol form produced by cytochrome P450 in rats, the cis-diol form in mice, RS-8359 glucuronide in dogs, and the 2-keto form in monkeys and humans. Thus, the rapid disappearance of the (S)-enantiomer from the plasma was thought to be due to the rapid metabolism of the (S)-enantiomer by different drug-metabolizing enzymes, depending on species.     

Chiral HPLC determination and stereoselective pharmacokinetics of tetrahydroberberine enantiomers in rats

Tetrahydroberberine (THB), a racemic mixture of (+)‐ and (?)‐enantiomer, is a biologically active ingredient isolated from a traditional Chinese herb Rhizoma corydalis (yanhusuo). A chiral high performance liquid chromatography method has been developed for the determination of THB enantiomers in rat plasma. The enantioseparation was carried out on a Chiral®‐AD column using methanol:ethanol (80:20, v/v) as the mobile phase at the flow rate 0.4 ml/min. The ultraviolet detection was set at 230 nm. The calibration curves were linear over the range of 0.01–2.5 μg/ml for (+)‐THB and 0.01‐5.0 μg/ml for (?)‐THB, respectively. The lower limit of quantification was 0.01 μg/ml for both (+)‐THB and (?)‐THB. The stereoselective pharmacokinetics of THB enantiomers in rats was studied after oral and intravenous administration at a dose of 50 and 10 mg/kg racemic THB (rac‐THB). The mean plasma levels of (?)‐THB were higher at almost all time points than those of (+)‐THB. (?)‐THB also exhibited greater C_max, and AUC_0–∞, smaller CL and V_d, than its antipode. The (?)/(+)‐enantiomer ratio of AUC_0–∞ after oral and intravenous administration were 2.17 and 1.43, respectively. These results indicated substantial stereoselectivity in the pharmacokinetics of THB enantiomers in rats. Chirality, 2012. © 2012 Wiley Periodicals, Inc.     

S-亚胺还原酶和葡萄糖脱氢酶共表达系统的构建及手性胺的合成

旨在构建S-亚胺还原酶(S-IRED)和葡萄糖脱氢酶(GDH)在大肠杆菌中的一菌双酶共表达系统,实现辅酶NADPH的再生,高效合成手性仲胺。利用无缝克隆的手段设计构建一种单质粒双启动子共表达系统,以全细胞为催化剂催化手性仲胺S-2-甲基吡咯烷(S-2MP)的合成,并研究温度、pH及有机溶剂对双酶反应的影响。成功构建了S-IRED和GDH的重组共表达质粒,实现了S-IRED与GDH在大肠杆菌中的胞内共表达,以亚胺2-甲基吡咯啉(2MPN)为模式底物,以工程菌全细胞催化手性仲胺S-2MP的合成,在低辅酶添加时催化手性胺的产率和光学纯度均高于95%。该双酶共表达体系的最适温度和pH分别为37℃和pH 8,10%以下的甲醇对双酶反应有正向促进作用。大肠杆菌胞内双酶共表达系统的构建实现了辅酶NADPH的原位再生,降低了亚胺还原酶催化合成手性胺的成本,为手性胺的规模制备奠定了基础。     

Chiral pharmacokinetics of rac-flurbiprofen and pharmacodynamics of anabolic bone response in the normal rat

The route of administration of the NSAID, flurbiprofen (sq vs. po) resulted in positive and negative results respectively with regard to enhanced cancellous and cortical bone accumulation in the immature rat. This pharmacokinetic study was an effort to understand the pharmacodynamic difference between the two routes of administration observed when the same dose range of drug, given as single daily doses, had been employed in both studies. Conventional chiral pharmacokinetics were evaluated in young rats. A significant difference was observed in the T_max of the active (S)-enantiomer by both administration routes (sq 4 h and po 1 h). The bioavailability, as evaluated by AUCs favored the sq route as expected. The plasma concentrations over 18 h, at steady state, for one po dose group (0.5 mg/kg/day) fell well within the therapeutic window described by the 0.1 and 0.5 mg/kg sq doses which had demonstrated anabolic bone activity. Oral dosing had exhibited no significant bone activity. We conclude that the pharmacodynamic difference between routes of administration cannot be simply explained on a pahrmacokinetic basis. Consequently, experiments detailing the pharmacodynamics and pharmacokinetics of single and multiple dose administration of aryl-propionic acids in normal and osteopenic states need further pharmacologic study. © 1994 Wiley-Liss, Inc.     

Resolution and determination of enantiomeric purity of the enantiomers of felodipine using chiral-AGP® as stationary phase

A direct chiral chromatographic reversed phase method for the determination of the enantiomers of felodipine is described. The influence of charged and uncharged modifiers as well as the effect of the mobile phase pH on the enantiomeric resolution is discussed. A high mobile phase pH and the addition of 2-propanol as organic modifier gave the highest separation factor (α = 1.3). The high mobile phase pH (pH = 7.6) is outside the recommended pH limit of silica based columns but was necessary to achieve baseline resolution of (R)- and (S)-felodipine. Improvement of column efficiency by increasing column temperature was utilized for optimization of the enantiomeric resolution (Rs = 1.7). The enantiomers of felodipine and three related compounds were separated within 15 min. The enantiomeric purity of (R)- and (S)-felodipine in injections and (R)-felodipine in bulk substance was higher than 99.5% and no racemization was observed after storage at accelerated conditions. A poor Chiral-AGP® column used for a long period was restored using a simple wash step together with repacking the top of the chromatographic column. © 1995 Wiley-Liss, Inc.     

Chiral discrimination and interaction mechanism between enantiomers and serum albumins

The chiral discrimination studies of biological system are theoretically and practically significant for the development of chiral drugs and life science. Our work has embarked upon the interaction between serum albumin (SA) (including human SA and bovine SA), R,S‐1‐(4‐methoxyphenyl)ethylamine, and R,S‐1‐(3‐methoxyphenyl)ethylamine. The formation of intermediate transition state, binding sites, and chiral discrimination ability can be investigated by ultraviolet‐visible spectra and fluorescence spectra. Moreover, both the changes of hydrophobic microenvironment and energy transfer can be detected by synchronous fluorescence spectra and fluorescence lifetime. Copyright © 2013 John Wiley & Sons, Ltd.