Pyridin-2-yl guanidine derivatives: conformational control induced by intramolecular hydrogen-bonding interactions.
J Org Chem
; 76(22): 9216-27, 2011 Nov 18.
Article
en En
| MEDLINE
| ID: mdl-21977964
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.
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1
Banco de datos:
MEDLINE
Asunto principal:
Guanidina
/
Guanidinas
Idioma:
En
Año:
2011
Tipo del documento:
Article