β N-O turns and helices induced by β2-aminoxy peptides: Synthesis and conformational studies

Abstract

Herein, we report an efficient route for the asymmetric synthesis of β 2-aminoxy acids as well as experimental and theoretical studies of conformations of peptides composed of β 2-aminoxy acids. The nine-membered-ring intramolecular hydrogen bonds, namely, β N-O turns, are generated between adjacent residues in those peptides, in accordance with our computational results. The presence of two consecutive homochiral β N-O turns leads to the formation of β N-O helical structures in solution, although both helical (composed of two β N-O turns of the same handedness) and reverse-turn (composed of two β N-O turns with opposite handedness) structures are of similar stability, as suggested by theoretical studies. Nevertheless, two slightly different conformations, with the same handedness, of β 2-aminoxy monomers have been observed in the solid state and in solution according to our X-ray and 2D NOESY studies. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.