Optical resolution of (+/-)-1-aryl-1-alkanols using enantioselective transesterification by lipases

Abstract

Enantioselective transesterification of 1-phenyl-1-alkanols (PhCH(OH)(CH2)n-2CH3; n = 2, 3, 4, 5, 6, 9, 12, 18) with vinyl acetate catalyzed by lipases in benzene has been studied to find the catalyst which is generally used for preparing optically active 1-phenyl-1-alkanols having various alkyl chains. Amongst lipases examined (lipases LIP, PS, AK, CAL and RML), the lipase from Pseudomonas aeruginosa (LIP) is the best catalyst which shows high reactivity and enantioselectivity and low substrate specificity. The rate of the LIP-catalyzed transesterification decreases with increasing the alkylchain length till n = 4. The catalysis of LIP recovers again toward the alkanols with n = 5-18. Other lipases do not exhibit such an effect of alkyl-chain length and show very poor or no catalysis for the alkanols with n > or = 4. LIP is also the best catalyst for the enantioselective transesterification of 1-(1-naphthyl)-, 1-(2-naphthyl)- and 1-(1-pyrenyl)-1-propanols. Each optically pure 1-aryl-1-alkanol was isolated by the present method.