Chiral Phosphinyl Enamines and Their Asymmetric Reduction through Group-Assisted Purification Chemistry Leading to Enantiopure β-Amino Esters/Amides

Abstract

A series of new chiral N-phosphinyl β-enamino esters and amides were successfully prepared with excellent Z-stereoselectivity (Z/E > 99:1 in nearly all cases). Group-assisted purification chemistry proved to be an efficient method for the asymmetric reduction of the resulting β-enamino esters/amides to give enantiopure β-amino esters/amides. The asymmetric reduction can be controlled efficiently by using a combination of sodium cyanoborohydride and acetic acid.