Structural peculiarities of 6-azacytosine and its derivatives imply intramolecular H-bonds

• Published in: Journal of molecular structure Vol. 484; no. 1-3; pp. 31 - 38
• Main Authors: Samijlenko, S.P, Alexeeva, I.V, Palchykivs’ka, L.H, Kondratyuk, I.V, Stepanyugin, A.V, Shalamay, A.S, Hovorun, D.M
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 08-06-1999
• Subjects: 6-azacytidine; Intramolecular H-bond; IR spectroscopy; PMR; Intramolecular H-bond; 6-azacytidine; PMR; IR spectroscopy
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/S0022-2860(98)00749-2

The study of 6-azaCyt, 6-azaC, a number of their derivatives and related compounds was performed by PMR and IR spectroscopies. The doublet splitting of amino group signals in PMR spectrum of 6-azaCyt (unlike the cases of the canonical base Cyt, nucleosides C and dC under the same experimental conditions) indicates non-equivalence of amino protons caused by the greater asymmetry of 6-azaCyt electronic structure, which increases on ring substitution at the 1 and 5 positions and by enhanced barrier of amino group rotation. The downfield component is insensitive to the 5-methyl substitution, which is probably related to the involvement of one amino proton into the intramolecular H-bond with the N3 atom. The inverse (as compared to Cyt) specificity of interactions of 6-azaCyt with amino acid carboxylic group and carboxylate ion has been shown in anhydrous dimethylsulfoxide (DMSO). IR spectroscopy data support the conclusion that investigated compounds with nonsubstituted amino group exist as keto–amino tautomers in DMSO and in solid state.