Candida antarctica lipase B-catalyzed reactions of β-hydroxy esters: Competition of acylation and hydrolysis

The ester function of ethyl cis-(+/-)-2-hydroxycyclopentane-1-carboxylate [(+/-)-1] and ethyl (+/-)-5-hydroxycyclopent-1-enecarboxylate [(+/-)-2] was demonstrated to undergo hydrolysis, as a side-reaction, during asymmetric (E > 200) O-acylation with Candida antarctica lipase B (CAL-B) as catalyst and vinyl acetate as acyl donor in t-BuOMe at 30 degrees C. This competition of acylation and undesirable hydrolysis draws attention to CAL-B-catalyzed non-hydrolytic resolutions where the substrates contain any hydrolysable functions. Enantiomerically enriched cis-2-hydroxycyclopentane-1-carboxylic acid (ee = 90%) and 5-hydroxycyclopent-1-enecarboxylic acid (ee = 47%) were prepared through de nova CAL-B-catalyzed hydrolysis of (+/-)-1 and (+/-)-2 with added H2O in t-BuOMe at 30 degrees C. (C) 2013 Elsevier B.V. All rights reserved.