Structural versatility of peptides from C^α,α‐dialkylated glycines. II. An IR absorption and ¹H‐nmr study of homo‐oligopeptides from C^α,α‐diethylglycine

Abstract

Abstract The conformational preferences of the N ‐trifluoroacetylated homo‐peptides of C α,α ‐diethylglycine from monomer to pentamer in chloroform solution were determined by using ir absorption and 1 H‐nmr. Intramolecular hydrogen bonding was found to be the dominant factor for all NH groups. The likely absence of a conformational transition upon increasing main‐chain length, and the remarkable stability to dilution, heating, and addition of perturbing agents, are additional relevant findings of this study. These results are in agreement with those of the fully extended, C 5 ‐conformation‐forming homo‐peptides from the higher homolog C α,α ‐di‐ n ‐propylglycine, but contrast dramatically to those of the homo‐peptides from the lower homolog C α,α ‐dimethylglycine, which have been shown to adopt the 3 10 ‐helical structure.