title: Z/E isomerism in Nα-Nα-disubstituted hydrazides and the amidoxy bond: application to the conformational analysis of pseudopeptides built of hydrazinoacids and α-aminoxyacids.
abstract: We have investigated the Z/E isomerism of the hydrazide link (CO-NH-N) and amidoxy link (CO-NH-O). The study was first focused on small molecular models using NMR and X-ray diffraction. It allowed determination of simple NMR criterions to differentiate easily the Z and E forms, which were then applied to investigate the behavior of these links inside the corresponding oligomers. Our results concerning the hydrazide link corroborate pioneering work that had been done in the 1970s except in the case were it is located inside aza-β(3)-cyclopeptides, where the old empirical rules failed to predict the right geometry of the link. The geometrical preference of the amidoxy bond is also unambiguously established and differs clearly from recent theoretical calculations. Our findings help rationalize the close self-organization ability of aza-β(3)-peptides and α-aminoxypeptides, two recently described foldamers.
authors.affiliation: ICMV, UMR CNRS 6226, Universite de Rennes I, 263 avenue du General Leclerc 35042 Rennes Cedex. philippe.legrel@univ-rennes1.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Le Grel
authors.forename: Arnaud
authors.initials: A
authors.lastname: Salaün
authors.forename: Clémence
authors.initials: C
authors.lastname: Mocquet
authors.forename: Barbara
authors.initials: B
authors.lastname: Le Grel
authors.forename: Thierry
authors.initials: T
authors.lastname: Roisnel
authors.forename: Michel
authors.initials: M
authors.lastname: Potel
mesh_terms: D000588:Amines / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D010087:Oxides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000588:Amines; D006834:Hydrazines; D010087:Oxides; D010455:Peptides