Biocatalyzed Enantioselective Reduction of Activated C=C Bonds: Synthesis of Enantiomerically Enriched alpha-Halo-beta-arylpropionic Acids

The enantioselective biocatalyzed reduction of the C=C bond of some (Z)-methyl alpha-halo-beta-arylacrylates was investigated. The reaction was performed by baker's yeast fermentation and Old Yellow Enzymes 1-3 mediated biotransformations. The final products were, respectively, enantiomerically enriched (S)-alpha-halo-beta-arylpropionic acids and their methyl esters, and ester hydrolysis was promoted in the whole cell system. High conversions and enantioselectivity values were observed when the aromatic ring was substituted by an electron-withdrawing group. Further manipulation of two of these enantiomerically enriched (S)-haloacids afforded p-substituted D-phenylalanines.