title: Pyridin-2-yl guanidine derivatives: conformational control induced by intramolecular hydrogen-bonding interactions.
abstract: The synthesis and conformational analysis of a series of pyridin-2-yl guanidine derivatives using NMR, X-ray crystallography, and B3LYP/6-31+G** theoretical studies are reported. A remarkable difference was observed in the (1)H NMR spectra of the guanidinium salts as compared with their N,N'-di-Boc protected and neutral analogues. This difference corresponds to a 180° change in the dihedral angle between the guanidine/ium moiety and the pyridine ring in the salts as compared to the Boc-protected derivatives, a conclusion that was supported by theoretical studies, X-ray data, and NMR analysis. Moreover, our data sustain the existence of two intramolecular hydrogen-bonding systems: (i) between the pyridine N1 atom and the guanidinium protons in the salts and (ii) within the tert-butyl carbamate groups of the Boc-protected derivatives. To verify that the observed conformational control arises from these intramolecular interactions, a new series of N-Boc-N'-propyl-substituted pyridin-2-yl guanidines were also prepared and studied.
authors: School of Chemistry, University of Dublin, Trinity College, Dublin 2, Ireland.
authors: Brendan
authors: B
authors: Kelly
authors: Daniel H
authors: DH
authors: O'Donovan
authors: John
authors: J
authors: O'Brien
authors: Thomas
authors: T
authors: McCabe
authors: Fernando
authors: F
authors: Blanco
authors: Isabel
authors: I
authors: Rozas
mesh_terms: D018360:Crystallography, X-Ray; D019791:Guanidine / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation
chemical_list: D006146:Guanidines; C570125:pyridin-2-yl guanidine; D019791:Guanidine