3-Methyladenine nucleosides: their synthesis, ring opening, and glycosidic bond cleavage.

3-Methyladenosine (Va) and 3-methyl-2'-deoxyadenosine (Vb) have been synthesized in the form of the p-toluenesulfonate salt by methylation of N'-benzyloxy-5-formamido-1-beta-D-ribofuranosylimidazole-4-carboxamidine (IIa) and of N'-benzyloxy-1-(2-deoxy-beta-D-ribofuranosyl)-5-formamidoimidazole-4-carboxamideine (IIb) followed by hydrogenolysis of the N'-benzyloxy group and cyclization. The 3-methyladenine nucleosides thus obtained are very unstable, and their hydrolytic cleavage of the glycosidic bond and ring opening of the adenine ring have been studied.