Asymmetric reductions of ethyl 2-(benzamidomethyl)-3-oxobutanoate by yeasts

The stereoselective reduction of ethyl 2–(benzamidomethyl)-3-oxobutanoate 1 using yeasts was investigated among a restricted number (12) of yeasts. Kluyveromyces marxianus var. lactis CL69 diastereoselectively produced (2R,3S)-ethyl 2–(benzamidomethyl)-3- hydroxybutanoate 2, whereas Pichia glucozyma CBS 5766 gave (2S,3S)-2 as the major stereoisomer. The biotransformations were independently optimised for minimizing by-products formation and maximizing the diastereoselectivity. . Under optimised conditions, K. marxianus var lactis CL 69 gave the (2R,3S)-ethyl 2–(benzamidomethyl)-3-hydroxybutanoate 2 with e.e. > 99% and d.e. = 98%, while P. glucozyma CBS 5766 allowed for the obtainment of (2S,3S)-2 with e.e. > 99% and d.e. = 86%.