OXAZABOROLIDINE CATALYZED ENANTIOSELECTIVE REDUCTION OF CYCLIC MESO-IMIDES

Full details of the enantioselective reduction of cyclic meso-imides c atalysed by an enantiopure oxazaborolidine derived from (S)-alpha,alph a-diphenylprolinol are reported. Treatment of the imides with borane i n the presence of the catalyst led to a mixture of cis- and trans-hydr oxylactams and, after subsequent ethanolysis, to the corresponding dia stereomerically pure trans-ethoxylactams. The enantiomeric excesses we re shown to be 68-94% by HPLC-determination. One example, in which the ethoxylactam was converted into the benzenesulfonyllactam, could be c rystallized to >99% enantiomeric purity. (C) 1997 Elsevier Science Ltd .