Conformational study of glycopeptides. Asn-containing peptides and their glycosylated derivatives

The conformational feature has been studied by n.m.r. spectroscopy on the compounds, Boc-Asn-NHMe, Boc-Asn-Gly-NHMe, Boc-Gly-Asn-NHMe, and their glycosylated derivatives. From the temperature dependence of the amide proton chemical shifts and vicinal coupling constants, little change was confirmed in the peptide conformation upon N-glycosylation. There is no particular intramolecular interaction between the peptide and carbohydrate moieties. Boc-Asn-Gly-NHMe takes, to some extent, a folded structure with a hydrogen bond involving the amide proton of N-methylamide group. This backbone conformation is also preferable in the corresponding glycopeptide.