Oxazaborolidine catalysed enantioselective reduction of cyclic meso-imides

Article abstract of DOI:10.1016/S0957-4166(97)00154-7

Full details of the enantioselective reduction of cyclic meso-imides catalysed by an enantiopure oxazaborolidine derived from (S)-α,α-diphenylprolinol are reported. Treatment of the imides with borane in the presence of the catalyst led 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 68-94% by HPLC-determination. One example, in which the ethoxylactam was converted into the benzenesulfonyllactam, could be crystallized to >99% enantiomeric purity.