Highly efficient and scalable chemoenzymatic syntheses of (R)- and (S)-lactaldehydes

Biocatalytic asymmetric reductions have been key steps in the enantioselective reduction of 1,1-dimethoxy-2-propanone, catalyzed by suitable ketoreductases, to enantiomerically pure (S)-and (R)-1,1-dimethoxy-2-propanols, obtained in >= 99.9% ee and excellent yield. Removal of the protecting group gave the (S)- and (R)-lactaldehydes in high yield and excellent enantiomeric and chemical purity.