Photochemistry of N6-methoxyadenosine and of N4-hydroxycytidine and its methyl derivatives II: photoinduced rupture of the NO bond

Abstract

The UV irradiation of dilute aqueous and ethanolic solutions of N 4-hydroxycytidine and its N (3) −, N 4- and N 4- O-methyl derivatives and of N 6-methoxyadenosine leads to rupture of the NO bond and the formation of cytidine and its methyl derivatives or adenosine. The reaction proceeds via the homolytic dissociation of the NO bond in the triplet state followed by interaction of the resultant radicals with the solvent. The path of the reaction is not affected by the pH of the solution or the wavelength of the exciting light (254 − 313 nm). The quantum yields of the NO bond cleavage were determined for various ionic and tautomeric forms of N 6-methoxy-adenosine and of N 4-hydroxycytidine and its methyl derivatives.