IMIDAZOLE RING-OPENING OF 7-METHYLGUANOSINE AT PHYSIOLOGICAL PH

It is shown by carbon-13 NMR that the only product of the imidazole ring-opening of 7-methyl-guanosine at physiological pH is 2-amino-6-hydroxy-5-N-methylformamido-4-(N-beta-ribofurano-sylamino)pyrimidine and that, contrary to previous results, the hydrolysis of the glycosylic bond at pH = 7.2 is a much slower process than the ring opening. The ring opened formamidopyrimidine derivative is a very mobile molecule existing under different conformations depending on the solvent, and in water it is capable of giving different kinds of aggregates. Possible biochemical implications of these results are discussed.