Enantio- and Regiospecific Partial Hydrolysis of Racemic Diol Diacetates by Pig Liver Esterase

Article abstract of DOI:10.1021/jo00059a046

The high enantio- and regiospecificity reported from this laboratory for the hydrolysis of the diacetate (+/-)-2 with pig liver esterase to yield pure monoacetate (+)-3a has been investigated further to define some of the structural features responsible for this unusual degree of specificity.The hydrolysis of the isomeric (+/-)-5 was found to proceed with identical specificity both qualitatively and quantitatively, indicating that the enzyme recognizes the overall geometry of these substrates but is unable to distinguish between the CF2 group and the oxygen bridge.Partial hydrolysis of the monocyclic diacetate (+/-)-16 showed parallel enantioselectivity but proceeded with only 25percent ee.These data indicate that the highly rigid 2 and 5 which present sterically well-defined targets to the enzyme result in the isolation of a single regioisomer and enantiomer as the major products of this reaction.In contrast, the conformational flexibility of 16 leads to poor differentiation between the rates of hydrolysis of the two enantiomers resulting in a low ee.It is concluded that conformationally stable molecules may offer favorable targets for regio and/or enantioselectivity in PLE reactions.