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

•The CAL-B-catalyzed enantioselective acylation of hydroxy esters has been demonstrated to be accompanied by hydrolysis.•The possibility of enzymatic hydrolysis needs to be carefully investigated.•When the acyl donor was used in a higher excess, the hydrolysis could be suppressed.•Enantiomerically enriched β-hydroxy acids were prepared through CAL-B-catalyzed 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 °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 novo CAL-B-catalyzed hydrolysis of (±)-1 and (±)-2 with added H2O in t-BuOMe at 30 °C.

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