Asymmetric synthesis of silylated alpha-amino acid esters through dynamic kinetic resolution

Abstract

Esters of three types of silylated alpha-amino acids have been prepared from appropriate zirconaaziridines. Slow addition (syringe pump) of the (R,R) carbonate of trans-stilbene gave metallacycles with the maximum possible diastereomeric excess (as determined by the diastereomeric excess produced by the Hoffmann test-the same reaction but with racemic carbonate). Methanolysis gave esters (RO(2)C)CH(R')(NHPh) (R' = Me(3)Si, Me(3)SiCH(2), and p-Me(3)SiC(6)H(4)) with the same optical purity at the alpha carbon.