Applying slow-release biocatalysis to the asymmetric reduction of ethyl 4-chloroacetoacetate.

Amberlite XAD 2 resin enhanced the asymmetric reduction of ethyl 4-chloroacetoacetate (ECA) to S-4-chloro-3-hydroxybutyric acid ethyl ester as catalyzed by Saccharomyces cerevisiae. The absorbed ECA was released slowly to the solution during the reaction so that the substrate inhibition and the spontaneous chemical hydrolysis of ECA were considerably lessened. With 75 g resin l(-1) and ECA at 74 mM, the reaction yield and the product's optical purity increased from 75% to 84% and from 88% to 93%, respectively.