Conformational studies on peptides of alpha-aminoxy acids with functionalized side-chains.

Peptides of homochiral alpha-aminoxy acids of nonpolar side chains can form a 1.8(8)-helix. In this paper, we report the conformational studies of alpha-aminoxy peptides 1-3, which have functionalized side chains, in both nonpolar and polar solvents. (1)H NMR, XRD, and FTIR absorption studies confirm the presence of the eight-membered-ring intramolecular hydrogen bonds (the N-O turns) in nonpolar solvents as well as in methanol. CD studies of peptides 1-3 in different solvents indicate that a substantial degree of helical content is retained in methanol and acidic aqueous buffers. The introduction of functionalized side chains in alpha-aminoxy peptides provides opportunities for designing biologically active peptides.