%0 Journal Article %A Kelly, Brendan %A O'Donovan, Daniel H. %A O'Brien, John %A McCabe, Thomas %A Blanco, Fernando %A Rozas, Isabel %D 2016 %T Pyridin-2-yl Guanidine Derivatives: Conformational Control Induced by Intramolecular Hydrogen-Bonding Interactions %U https://acs.figshare.com/articles/journal_contribution/Pyridin_2_yl_Guanidine_Derivatives_Conformational_Control_Induced_by_Intramolecular_Hydrogen_Bonding_Interactions/2581942 %R 10.1021/jo200954c.s001 %2 https://acs.figshare.com/ndownloader/files/4227724 %K series %K dihedral angle %K intramolecular interactions %K 1 H NMR spectra %K NMR analysis %K guanidinium salts %K pyridine N 1 atom %K derivative %K guanidinium protons %K B 3LYP %K guanidine %K data %K Conformational Control Induced %K pyridine ring %X 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 1H 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. %I ACS Publications