Synthesis of optically active amino ketones from (s)-serine

The oxazoline-protected (S)-serine methyl ester 2 can be coupled with various organolithio compounds to give the corresponding ketones 4a-d in good yield without racemisation.     

Asymmetric synthesis of alanine by hydrogenolytic asymmetric transamination

Hydrogenolytic asymmetric transamination between alkyl (R)-phenylglycinate and ethyl pyruvate was studied. The effect of the asymmetric moieties and of the solvents used in the asymmetric synthesis were explained by the substrate-catalyst complex.     

Practical synthesis of optically active amino alcohols via asymmetric transfer hydrogenation of functionalized aromatic ketones

2-Substituted acetophenones such as 2-cyano-, 2-azido-, or 2-nitroacetophenones were effectively reduced with a mixture of HCOOH/N(C(2)H(5))(3) containing a chiral Ru(II) catalyst, RuCl[(S,S)-N-(p-toluenesulfonyl)-1,2-diphenylethylenediamine](p-cymene), giving the corresponding optically active alcohols, which can be converted to optically active amino alcohols with excellent ee's. Similarly, the reaction of 2-benzoylacetophenone with the same Ru catalyst gave a quantitative yield of the corresponding optically active 1,3-diol with 99% ee.     

Asymmetric synthesis by chiral cobalt catalysts: Homogeneous reduction of ketones to optically active alcohols

The hydrogenation of ketones with Co₂(CO)₆(PR₃)₂ (PR₃ = PPh₂-neomenthyl, PPh₂ -6-deoxo-1,2:3,4-diisopropylidene d-galactose and PMe₂ -menthyl) as catalysts gives optically active alcohols in optical yields of 1.6 to 5%.     

Synthesis of optically active amino acids during asymmetric phase-transfer catalysis

Conclusions Asymmetric alkylation of the amino acid fragment of Ni²⁺ complexes of the Schiff bases of glycine with N-(2-pyridinecarbonyl)-o-aminobenzophenone and of alanine with N-(2-pyridinecarbonyl)-o-aminobenzaldehyde has been carried out under phase-transfer conditions using N-benzylcinchonidinium chloride as the chiral phase-transfer catalyst.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 631–635, March, 1989.     

Enantioselective synthesis of optically active secondary amines via asymmetric reduction

The enantioselective synthesis of optically active secondary amines via the asymmetric reduction of N-substituted ketimines with various chiral hydride reagents, such as Itsuno's reagent (1), Corey's reagent (2), K glucoride (3), Sharpless' reagent (4), and Mosher's reagent (5) has been investigated. Among the hydride reagents examined, 1 gave the best results in terms of asymmetric induction. Thus, the reduction of N-phenylimine derivatives of aromatic ketones with 1 provided the corresponding amines in 96–98% yields with high optical induction, such as 73 % ee for acetophenone N-phenylimine (6a), 87 % ee for propiophenone N-phenylimine (6b), 88 % ee for bulyrophenone N-phenylimine (6c), and 71 % ee for isobutyrophenone N-phenylimine (6d). In the case of N-alkyl ketimine derivatives, the reduction afforded somewhat lower optical inductions as compared to those of N-phenyl derivatives, giving 46 % ee for acetophenone N-benzylimine (6f), 52 % ee for acetophnone N-ⁿ-heptylimine (6g) and 43 % ee for acetophenone N-cyclohexylimine (6h). However, the substitution of a bulky alkyl group on nitrogen of the ketimines increases remarkably the optical induction of product amine, such as 80 % ee for acetophenone N-tert-butylimine (6e). The reduction of N-substituted aliphatic ketimines gave very low optical inductions (7.4 – 24 % ee). The catalytic effects of oxazaborolidines (1a and 2a) in the reduction of ketimines with 1 and 2 were also examined.     

Stereoselectivity in reactions of metal complexes VII. Asymmetric synthesis of amino acids by metal ion-promoted transamination

Enantioselective synthesis of phenylalanine was performed by reacting phenylpyruvic acid with pyridoxamine followed by ketimine-aldimine isomerization of the Schiff base formed catalyzed by an optically active copper (II)-complex. By UV and CD measurements it was shown that the enantiomeric excess strongly depends on the reaction conditions and on the reaction time. In favorable cases it reached values up to 80%. The selectivity of the reaction is discussed on the basis of possible structures of the intermediate mixed ligand complex.     

One-pot asymmetric synthesis of either diastereomer of tert-butanesulfinyl-protected amines from ketones

A one-pot method for the asymmetric synthesis of tert-butanesulfinyl-protected amines is described. Condensation of aryl alkyl and dialkyl ketones with tert-butanesulfinamide followed by in situ reduction with the appropriate reagent provides either diastereomer of the sulfinamide products in good yields and with diastereomeric ratios of up to 99:1.     

(S)-2-芳基丙酸不对称合成研究进展

对(S)-2-芳基丙酸类非甾体抗炎药光学纯品的不对称合成方法进行了总结和概述，从中反映近年不对称合成中新概念、新方法和新技术的应用。     

Stereoselectivity in reactions of metal complexes VIII. Asymmetric synthesis of some amino acids by stereoselective transamination of aliphatic keto acids in mixed ligand copper(II)-Schiff-base complexes

Optically active alanine, valine and leucine were obtained by a transamination reaction between pyridoxamine and the corresponding α-keto acid in the presence of a Cu²⁺-complex with the tridentate ligand 2,6-bis[(3S)-3-phenykl-2-azabutyl]pyridine. In each case the amino acid with (R)-configuration was formed preferentially, and the maximum enantiomeric excesses were 54% (alanine), 48% (leucine) and 29% (valine). The stereoselectivity of the reaction is discussed in terms of the possible structure and the stability of the intermediate Cu²⁺-ketimine-ligand complex.