Oxazaborolidine catalyzed enantioselective reductions of cyclic meso-imides☆

Abstract A new asymmetric reduction method for meso -imides is reported. Treatment of various imides with a mixture of a chiral oxazaborolidine and BH 3 leads to a mixture of cis - and trans -hydroxylactams and, after subsequent ethanolysis, to the corresponding diastereomerically pure trans -ethoxylactams. The enantiomeric excesses were shown to be 75–89% by both chiral HPLC-determinations and conversion of the reduction products into the corresponding, known lactones.