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 optimized for minimizing by-product formation and maximizing the diastereoselectivity. Under optimized conditions, K. marxianus var. lactis CL 69 gave the (2R,3S)-ethyl 2-(benzamidomethyl)-3-hydroxybutanoate 2 with ee > 99% and de = 98%, while P. glucozyma CBS 5766 allowed for the production of (2S,3S)-2 with ee > 99% and de = 86%. (c) 2009 Elsevier Ltd. All rights reserved.