Stereoselective Reduction of α-Keto Ester and α-Keto Amide with Marine Actinomycetes, Salinispora Strains, as Novel Biocatalysts

To clarify the potential ability of marine actinomycetes as biocatalysts, the stereoselective reduction of α-keto esters and α-keto amide using Salinispora arenicola and Salinispora tropica was tested. The reduction of ethyl pyruvate and ethyl 2-oxobutanoate by S. tropica gave corresponding alcohol with high conversion ratio and in high e.e. (96% e.e. (S) and 99% e.e. (S), respectively). In the presence of l-glutamate as an additive, the reduction of ethyl pyruvate by S. tropica afforded the corresponding (S)-ethyl lactate with >99% e.e. Furthermore, 2-chlorobenzoylformamide was reduced by S. tropica to the corresponding (R)-2-chloromandelamide with high conversion ratio and excellent enantioselectivity (>99% e.e.). Thus, it was found that marine actinomycetes, Salinispora strains, had high ability for the stereoselective reduction of carbonyl compounds as useful biocatalysts.