Lipases in anhydrous organic solvents catalyze the lactonization of esters of y-hydroxy carboxylic acids with a high degree of stereospecificity. Under these conditions the lipases exhibit both enantioselectivity and prochiral selectivity. We exploited the enzymes' enantioselectivity for synthesis of chiral lactones from racemic y-hydroxy esters and their prochiral stereospecificity, ie the ability to discriminate between enantiotopic groups of a ...