Peptoid residues and beta-turn formation.

A set of terminally protected tripeptoids containing a residue of either N-methylglycine or N-isobutylglycine in position i + 1/i + 2 were synthesized and tested for intramolecularly H-bonded beta-turn formation. By exploiting FT-IR absorption and 1H NMR techniques, their folding tendencies were compared with those of a variety of reference peptides. The amount of beta-turn induction and the relative extent of the various types of intramolecularly H-bonded beta-turn conformers were determined in chloroform solution.