Ruthenium- and enzyme-catalyzed dynamic kinetic resolution of secondary alcohols

Enzymatic resolution of secondary alcohols under substrate racemizing conditions was studied using an immobilized lipase from Candida antarctica in the presence of a ruthenium catalyst. A specifically designed acyl donor, 4-chlorophenyl acetate, was found to be compatible with both catalysts and resulted in an efficient dynamic kinetic resolution. Studies of the reaction in different solvents showed that nonpolar solvents gave the best results. With this process, a variety of racemic secondary alcohols were transformed to the corresponding enantiomerically pure acetates, making efficient use of all starting material. In most cases, the reaction proceeded with >99% ee and in good yield.