Kinetic resolutions of amine and thiol analogues of secondary alcohols catalyzed by the Candida antarctica lipase B

Abstract

Chiral amine and thiol analogues of secondary alcohols were tested as substrates for the Candida antarctica lipase B with emphasis on lipase enantioselectivity and substrate reactivity. Although the apparent enantiomeric ratios were lower for the amines than for the corresponding alcohols, the amines 2-octylamine and 1-phenyl-ethylamine were produced with high optical purity (ee-93–99%) in a lipase-catalyzed acyl transfer reaction with ethyl octanoate as the acyl donor. The initial rates were lower and the reaction times longer for the amines than for the corresponding alcohols. The thiols 2-octanethiol and 1-phenylethanethiol did not yield any thiol ester product in the analogous lipase-catalyzed acyl transfer reaction. By preparing the thiooctanoate of 1-phenyl-ethanethiol and employing it as acyl donor in a lipase-catalyzed reaction with 1-phenylethanol as acyl acceptor, however, 1-phenylethanethiol could be resolved with high enantiomeric excess of the ( R)-enantiomer (ee-95%) and moderate enantiomeric excess of the ( S)-enantiomer (ee-75%).