α-Amido sulfones from natural α-amino acids and their reaction with carbon nucleophiles

Amides obtained from N-carbamoyl α-amino acids react with aldehydes in the presence of benzenesulfinic acid to give α-amido sulfones in good yield. These derivatives act as equivalents of N-acylimines in the reaction with nucleophiles leading to the corresponding addition products. The utilization of the lithium enolate of alkyl acetates as a nucleophile allows the preparation of α,β-dipeptides, while a two-step procedure involving nitromethylation and Nef conversion leads to the synthesis of α,α-dipeptides.