1H NMR investigation on 6-azacytidine and its derivatives

Abstract The study of 6-azaCyt, 6-azaC, a number of their derivatives and related compounds was performed by 1 H NMR spectroscopy. The doublet splitting of amino group signals in 1 H NMR 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 is shown in anhydrous DMSO.