Preparation of both enantiomers of ethyl 4,4,4-trifluoro-3-hydroxy butanoate by enantioselective microbial reduction

The effect of some parameters, i.e. temperature, time, pH and concentration, on the baker's yeast reduction of ethyl 4,4,4-trifluoroacetoacetate is presented. The enantiomeric excess of the R enantiomer appeared to increase up to 76% when the temperature of the reduction decreased. The other factors do not appear to improve the enantioselectivity of the reaction. Reduction with Candida utilis allowed preparation of the S enantiomer in higher optical purity than previously reported.