RESOLUTION OF DIOLS WITH C2-SYMMETRY BY LIPASE-CATALYZED TRANSESTERIFICATION

S-Ethyl thiooctanoate was used as acyl donor in the transesterification of 2,3-butanediol (1), 2,4-pentanediol (2), and 2,5-hexanediol (3), catalysed by a lipase from Candida antarctica. Mixtures of all stereoisomers were used as substrates in each case. 2,5-Hexanediol was transesterified with high stereoselectivity and the (2S,5S)-2,5-hexanediol was isolated in good yield with >99 % ee. The diester of (2R,5R)-2,5-hexanediol was formed in good yield and was hydrolysed to yield the (2R,5R)-2,5-hexanediol of high enantiomeric excess (>99% ee). Similar results were obtained for 2,4-pentanediol with >99% ee for both enantiomers. The stereoselectivity for 2,3-butanediol was lower than for 2 and 3, giving 89% ee for the R,R-enantiomer and 34% ee for the SS-enantiomer.