STRUCTURAL VERSATILITY OF HOMO-PEPTIDES FROM C-ALPHA,ALPHA-DIALKYLATED GLYCINES

A theoretical and experimental analysis of the preferred conformations of homo-peptides from C** alpha **,** alpha -dialkylated glycines revealed that these compounds are characterized by a marked structural versatility. Fully extended (C//5-conformations), folded (of the beta -bend type), and 3//1//0-helical structures are adopted as a function of side-chain nature. Dimethylated and cyclic side chains favor folded and helical structures, whereas diethylated and longer acyclic side chains favor the fully extended structure. By means of conformational energy calculations the preferred screw sense of the helical structure of homo-peptides from a representative chiral acyclic residue is also anticipated.