Asymmetric Synthesis of (R)-and (S)-Moprolol

A simple and effective procedure for the enantioselective synthesis of (R)-and (S)-moprolol was described.The key step was the asymmetric synthesis of enantiopure (R)-and (S)-guaifenesin,which were synthesized from enantioenriched (R)-3-chloro-1,2-propanediol and (S)-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-CoIIII complex.The e.e.values of both the optical compounds were above 98%,and the chemical structures of the target compounds were confirmed by 1H NMR,13C NMR,IR,and MS.     

光学纯的(4S, 8R)-和(4S, 8S)-1- 烯-8, 9-二醇的改进合成法

本文提出了一个改进的合成两个光学异构纯的94S)-1- 烯-8, 9-二醇的方法,其优点是简便、有效, 适于克量级制备。     

Enzymatic synthesis of (R) and (S) 1-deuterohexanol

This paper describes practical enzymatic procedures for the synthesis of (R) and (S) 1-deuterohexanol, a useful building block for chiral poly isocyanated liquid crystals. Alcohol dehydrogenases from horse liver and Pseudomonas catalyzed the reduction of hexanal with deuterated NAD (NADD) resulting in 50% and 89% yields of (R) and (S) 1-deuterohexanol, respectively. The deuterated cofactor was regenerated in situ by alcohol dehydrogenase catalyzed oxidation of ethanol-d6 or 2-propanol-d8. The (S) alcohol was also synthesized by the horse liver alcohol dehydrogenase reduction of 1-deuterohexanal, which was prepared chemically from hexanal. The yields of the reaction were greatly increased by the use of a biphasic system or with the immobilized enzyme in anhydrous organic solvents. Horse liver alcohol dehydrogenase was stabilized by immobilization on PAN or noncovalent entrapment on XAD resin.     

Simultaneous enzymatic synthesis of (S)-3-fluoroalanine and (R)-3-fluorolactic acid

A coupled enzymatic system for the simultaneous synthesis of (S)-3-fluoroalanine (1a) and (R)-3-fluorolactic acid (3) with l-alanine dehydrogenase (l-AlaDH) from Bacillus subtilis and rabbit muscle l-lactate dehydrogenase (l-LDH) using rac-1 and NAD⁺ is described. Analysis of isolated products of the laboratory preparative scale process revealed 1a in 60% yield and 88% ee and 3 in 80% yield and over 99% ee. The compounds 1a and 3 represent chiral building blocks for the synthesis of several products with pharmacological activity.     

High-performance liquid chromatographic determination of (R)-and (S)-proxyphylline in human plasma

A reversed-phase high-performance liquid chromatographic assay has been developed for determination of (R)-(--)-and (S)-(+)-proxyphylline in human plasma. The procedure is based on liquid-solid extraction of proxyphylline from plasma followed by derivatization of extracted proxyphylline with (--)-camphanoyl chloride. The ratio between the enantiomers is calculated from the peak areas of the corresponding diastereoisomeric proxyphylline camphanates after injection into the liquid chromatograph. The recovery of proxyphylline from plasma was 88% (coefficient of variation = 4%) and proxyphylline was detectable from a plasma concentration of 0.2 micrograms/ml. Three different plasma extraction procedures for proxyphylline using Extrelut, Bond Elut, and Chem Elut columns have been developed and compared, and the rate of derivatization of the proxyphylline enantiomers with camphanoyl chloride has been studied.     

从D-甘露糖醇制备(R)和(S)-3,3-二甲基-2,3-O-异亚丙基甘油酸甲酯

本文提出了一种由D-甘露糖醇出发合成一对高光学纯度的异亚丙基保护的3,3-二甲基甘油酸甲酯2a和2b的有效方法     

Definite peak identification of (R)-and (S)-methadone and (R)- and (S)-EDDP using established HPLC and CE methods

Methadone is widely used for the treatment of opioid dependence. HPLC and CE are widespread methods for drug monitoring and metabolism studies. Although the methods are widely used for methadone and its main metabolite EDDP [1, 2], a definite direct peak identification for EDDP enantiomers is not described. This study describes a method for specific identification of each peak in the chromatogram and electropherogram of methadone analysis. The result of the study demonstrates differences in the elution order of the enantiomers of methadone and EDDP due to the technique used for analysis. The elution order of EDDP using HPLC is interchanged with respect to the order of the peaks in the electropherogram.     

(R)-和(S)-石蚕蛾属于信息素的合成

以樟脑衍生物(-)-莰烷磺内酰胺为原料,经N-(E-2-烷烯酰基)莰烷-10,2-磺内酰胺与烷基格氏试剂的不对称Michael加成反应,LiAlH4还原断裂,3-甲基已醇的碘代反应及有机镉试剂与丙酰氯的偶联反应制得(R)-和(S)-石蚕蛾雄性性信息素6-甲基于-3-壬酮,其光学纯度达96%ee以上。     

Asymmetric synthesis of syn-(2R,3S)-and anti-(2S,3S)-ethyl diamino-3-phenylpropanoates from N-(benzylidene)-p-toluenesulfinamide and glycine enolates

Addition of differentially N-protected glycine enolates to enantiopure sulfinimines affords syn- and anti-alpha,beta-diamino esters with high diastereoselectivities and good yields.     

Asymmetric synthesis of (1R,2S,3R)-gamma-methyl-cis-pentacin by a kinetic resolution protocol

The asymmetric synthesis of (1R,2S,3R)-3-methyl-2-amino-cyclopentane carboxylic acid has been achieved via kinetic resolution of racemic tert-butyl 3-methyl-cyclopentene-1-carboxylate with homochiral lithium (S)-N-benzyl-N-alpha-methylbenzylamide.     

二乙酰酒石酸酐柱前手性衍生化反相高效液相色谱法拆分心得安对映体

以（Ｒ，Ｒ）－Ｏ，Ｏ－二乙酰基酒石酸酐作柱前手性衍生化试剂，用ＯＤＳ柱拆分了心得安对映体，探讨了衍生化反应条件，研究了ＰＨ及流动相组成对色谱保留行为的影响，发现心得安的两种非对映异构体衍生物的荧光响应有显著差别，对心得安对映体的半制备色谱拆分规律作了新的探讨，确定用Ｓｈｉｍ－ｐａｃｋＣＬＣ－ＯＤＳ柱进行半制备色谱拆分的最佳条件，得到的光学异构体纯度在９９％以上。     

Effective synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol by asymmetric enzymatic reduction

The synthesis of (S)-3,5-bistrifluoromethylphenyl ethanol, a pharmaceutically important alcohol intermediate for the synthesis of NK-1 receptor antagonists, was demonstrated from a ketone via asymmetric enzymatic reduction. The isolated enzyme alcohol dehydrogenase from Rhodococcus erythropolis reduced the poorly water soluble substrate with excellent ee (>99.9%) and good conversion (>98%). The optimized process was demonstrated up to pilot scale using high substrate concentration (390 mM) using a straightforward isolation process achieving excellent isolation yields (>90%) and effective space time yield (100–110 g/L d). Process improvements, demonstrated at preparative scale, increased the substrate concentration to 580 mM achieving a space time yield of 260 g/L d.     

Preparation of (R)- and (S)-6-hydroxybuspirone by enzymatic resolution or hydroxylation

6-Hydroxybuspirone is an active metabolite of the antianxiety drug buspirone. The (R)- and (S)-enantiomers of 6-hydroxybuspirone were prepared using an enzymatic resolution process. l-Amino acid acylase from Aspergillus melleus (Amano Acylase 30000) was used to hydrolyze racemic 6-acetoxybuspirone to (S)-6-hydroxybuspirone in 95% ee after 45% conversion. The remaining (R)-6-acetoxybuspirone with 88% ee was converted to (R)-6-hydroxybuspirone by acid hydrolysis. The ee of both enantiomers could be improved to 99% by crystallization as a metastable polymorph. (S)-6-Hydroxybuspirone was also obtained in 88% ee and 14.5% yield by hydroxylation of buspirone using Streptomyces antibioticus ATCC 14890.     

Asymmetric synthesis of (S,R)- and (R,R)-methiin stereoisomers

Abstract

An asymmetric synthesis of (+)- and (–)-methiine (S-methyl-(R)-cysteine sulfoxide) diastereomers has been developed. These natural sulfur compounds were isolated from a variety of Brassica vegetables. As the starting compound, (R)-cysteine was used, which was methylated to form (R)-S-methylcysteine. Then the oxidation of S-methylcysteine with tert-butyl hydroperoxide catalyzed by the chiral tetra(isopropylate)titanium/(S)- or (R)-Binol complex led to the formation of (1?R,2S)-(+)- or (1?R,2R)-(–)-methiin stereomers.     

A Convenient Approach to the Enantiopure (1S,2S,4S,5S)-and (1R,2S,4R,5S)-2,5-Bis(phenylmethyl)-1,4-diazabicyclo[2.2.2]-octane

Introduction1,4 Diazabicyclo[2 .2 .2 ]octane (DABCO)wasre portedtocatalyzeorganicreactionsduetoitsstrongbasici ty .1,2 Severalchiraltrans 2 ,3 disubstitutedDABCOshavebeensynthesizedandappliedtotheasymmetricBaylis Hillmanreaction3andvicinalhydroxylation .4ThefirstsynthesisofthetitlecompoundwasreportedbySoai5from (2S ,5S) bis(phenylmethyl)piperazine (1) ,asshowninScheme 1.Butthisprocedureislengthy ,andtheoverallyieldisnotsosatisfactory .Besides ,thereport edmethodforthepreparationof 1is…     

Asymmetric synthesis of (R)-(+)-etomoxir via enzymatic resolution

An asymmetric synthesis of (R)-(+)-etomoxir 3, employing enzymatic resolution of ethyl 2-alkyl-2,3-dihydroxypropionate using Amano AK via transacylation is reported.     

Studies towards the synthesis of (1R,2S)- and (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonates and (1S,2S)- and (1R,2S)-2,3-epoxy-1-hydroxypropylphosphonates

The trans-configured fosfomycin analogue, diethyl (1S,2S)-1,2-epoxy-3-hydroxypropylphosphonate, was synthesised by the intramolecular Williamson reaction of diethyl (1S,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate. The cis-analogue was obtained as O-ethyl or O,O-diethyl (1R,2S)-1,2-epoxy-3-hydroxypropylphosphonates, when (1R,2R)-1,3-dihydroxy-2-mesyloxypropylphosphonate or its 3-O-trityl derivative were used as starting materials, respectively. The intramolecular Williamson cyclisations of diethyl (1S,2R)- and (1R,2S)-1-benzyloxy-3-hydroxy-2-mesyloxypropylphosphonates led to diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, respectively, with the concomitant formation of diethyl (E)-1-benzyloxy-3-hydroxyprop-1-en-1-phosphonate. From diethyl (1S,2S)- and (1R,2S)-2,3-epoxy-1-benzyloxypropylphosphonates, enantiomerically pure diethyl (1S,2S)- and (1R,2S)-1,2-dihydroxypropylphosphonates were obtained by catalytic hydrogenation, while diethyl (1S,2S)- and (1R,2S)-3-acetamido-1,2-dihydroxypropylphosphonates were produced after epoxide ring opening with dibenzylamine, acetylation and hydrogenolysis.