Asymmetric Reduction of Prochiral Cyclic Imines to Alkaloid Derivatives by Novel Asymmetric Reducing Reagent in THF or under Solid-State Conditions

Asymmetric reductions of prochiral cyclic imines were studied using chiral nonracemic sodium acyloxy borohydride 2 . The chiral nonracemic reducing agent 2 has been easily prepared by the reaction of NaBH 4 with N,N -phthaloyl amino acid 1 in THF. The reagent reduces the prochiral cyclic imines 3 and 5 to the alkaloid derivatives 4 and 6 in good enantioselectivity (65−75% ee). The reduction of prochiral cyclic imines with the reagent in the presence of ZnCl 2 or under solid-state conditions showed higher enantioselectivity (83−100% ee).