Late-Stage N-Alkylation of Azapeptides

Azapeptides undergo on-resin, late-stage N-alkylations to install side chains with high chemoselectivity for the hydrazide nitrogen atoms. The major product is the N1-alkylated azapeptoid, with only small amounts (<10%) of alkylation occurring at the other aza-amino acid nitrogen (N2). Dialkylations are also possible and afford highly functionalized, disubstituted azapeptides with side chains installed on both aza-amino acid nitrogen atoms. The site-selectivity was determined using Edman degradation, MS/MS sequencing, and comparative LCMS and NMR analyses.

Automated summary

Azapeptides can undergo late-stage N-alkylations on-resin to selectively install side chains on the hydrazide nitrogen atoms. The major product is the N1-alkylated azapeptoid, while only a small amount of alkylation occurs on the other aza-amino acid nitrogen (N2). Site-selectivity was determined using various analytical techniques.