Synthesis of Optically Active α-Hydroxy Acids by Kinetic Resolution Through Lipase-Catalyzed Enantioselective Acetylation

The lipase-catalyzed acetylation of a broad spectrum of racemic 2-hydroxy acids 1 to their 2-acetoxy acids 2 was shown to proceed with high enantioselectivity. Thus, the microbial lipases, in particular from Candidaantarctica and Burkholderiaspecies, are convenient biocatalysts for the synthesis of optically active 2-hydroxy acids in excellent enantioselectivity (ee values up to > 99%). The absolute configurations of the 2-hydroxy acids 1 were assigned by comparison of the gas-chromatographic data with that of literature-known reference compounds, or by means of the exciton-coupled circular dichroism method (ECCD) on their bichromophoric 2-naphthoate 9-anthrylmethyl derivatives 3. These results establish that (S)-2-hydroxy acids 1 were preferentially acetylated by microbial lipases.