Crystal structures of aza-β3-peptides, a new class of foldamers relying on a framework of hydrazinoturns

Crystals of aza-beta 3-peptides have been obtained. This gives the first opportunity for hydrazino peptides, in the sense of oligomers built exclusively with cc-hydrazinoacetic units, to be observed in the solid state. The structures make it clear that the H-bond network developed by aza-beta(3)-peptides differs radically from those of the corresponding beta(3)-peptides but strongly resembles that of the alpha-aminoxy peptides. Our study contributes to the current interest in hydrazino peptides as an extension of the beta-peptide concept.