BIOELECTROCATALYTIC REDUCTION OF 3-KETOESTERS USING BAKERS-YEAST

The electrochemical asymmetric reduction of 3-ketoesters using baker's yeast in the bioelectrocatalytic reaction system under anaerobic cond itions was investigated. The bioelectrocatalytic reaction system is co mposed of the electrochemical reduction cycle of viologen, RV2+ to RV+ on a cathode, the generation cycle of NADH which is produced with RV ++ from NAD: and the reduction cycle of substrates with NADH. The bake r's yeast containing in the system catalyzes the generation of coenzym e and the reduction of substrates. The preparative scale asymmetric re duction of ethyl acetoacetate (1a), ethyl 3-oxovalerate (1b), and ethy l 4, 4, 4-trifluoroacetoacetate (1c) using the bioelectrocatalytic rea ction system led to the corresponding optically active 3-hydroxyesters , ethyl (S)-(+)-3-hydroxybutyrate (2a), ethyl (R)-(-)-3-hydroxyvalerat e (2b), and ethyl (R)-(+)-4, 4, 4-trifluoro-3-hydroxybutyrate (2c), re spectively, with high current efficiencies and enantioselectivities. T he stereochemistry of products, 2a and 2c obeyed the Prelog's rule but 2b was contrary. The reaction conditions for electrochemical reductio n of 3-ketoesters were also discussed.