Enantioselective Biocatalytic Synthesis of β²-Amino Acids

Significance

Asymmetric hydrogenation of β -nitroacrylates 2 by NADPH in the presence of Saccharomyces carlsbergensis old yellow enzyme is reported as a key step for the preparation of enantiomerically enriched β²-amino acids 3. It has been observed that 2-alkyl-substituted nitroalkenes were reduced in high yields (>98%) and with high enantiomeric excesses (93.5:6.5 to 98:2 er), whereas 3-alkyl-substituted products were obtained in essentially racemic form. The required β -nitroacrylates 2 are easily prepared from the corresponding α-keto esters 1 in two steps.