Stereoselective, biocatalytic reductions of α-chloro-β-keto esters

(Chemical Equation Presented). Eighteen known and putative reductases from baker's yeast (Saccharomyces cerevisiae) were tested for the ability to reduce a series of α-chloro-β-keto esters. In nearly all cases, it was possible to produce at least two of the four possible α-chloro-β- hydroxy ester diastereomers with high optical purities. The utility of this approach was demonstrated by reducing ethyl 2-chloroacetoacetate to the corresponding syn(2R,3S)-alcohol on a multigram scale using whole cells of an Escherichia coli strain overexpressing a single yeast reductase identified from the screening studies.