ORGN 523

It is known that seven-membered-ring intramolecular hydrogen bond (γ-turn) is seldom formed in naturally occurring peptides composed of a -amino acids. Here we report a new strategy to induce g-turn into short linear peptides. The previous studies of our group have shown that, in the oligomers of a-aminoxy acids, eight-membered-ring intramolecular hydrogen bonds (N-O turns) are formed between the adjacent residues. In this project, we designed and synthesized several peptides (1-6) containing alternating a -L-aminoxy acids and a -L-amino acids. ¹H NMR and IR studies revealed that the N-O turn immediately after an a-amino acid residue could induce a g-turn in the previous residue. Moreover, 2D NMR and CD studies suggested that oligomers 3 and 6 form a novel reverse turn structure in non-polar solvents.