EFFECTS OF MEDIUM AND OF REACTION CONDITIONS ON THE ENANTIOSELECTIVITY OF LIPASES IN ORGANIC-SOLVENTS AND POSSIBLE RATIONALES

The nature of organic solvents markedly influenced the enantioselectivity, expressed as the enantiomeric ratio, of porcine pancreatic lipase and of Lipase PS in transesterification between trifluoroethyl butanoate and the two unrelated alcohols (+/-)-sulcatol (1) and (+/-)-3-bromo-5-hydroxymethyl isoxazoline (2). However, there was no correlation between enantioselectivity and such physicochemical characteristics of the solvent as hydrophobicity and dielectric constant. A rationale based on the formation of solvent-enzyme complexes is proposed to explain the results. Enzyme enantioselectivity was also affected by temperature but not by the chain length of the acylating agent nor by the removal of water from the reaction medium by molecular sieves. The effects of these parameters on transesterification rates were also investigated.