The enantioselectivity of lipase PS in chlorinated solvents increases as a function of substrate conversion

The enantiomeric ratio E of lipase from Pseudomonas cepacia increased markedly as a function of substrate conversion in the resolution of (+/-)-6-methyl-5-hepten-2-ol (sulcatol) when methylene chloride was used as reaction medium. Such behavior was observed, even though less pronounced, also in dichloroethane. Instead, when cyclohexane and toluene were used as reaction medium or when 3-methyl-2-cyclohexen-1-ol was employed as substrate, enzyme enantioselectivity remained constant. No explanation for the phenomenon, which can have practical implications for resolutions carried out in organic solvents, has been found yet.