3-Methylinosine (2a) has been prepared in 28% yield by heating 5-(methylamino)-1-(2, 3, 5-tri-O-acetyl-β-D-ribofuranosyl) imidazole-4-carboxamide (5c) with a mixture of ethyl orthoformate and acetic anhydride, followed by ammonolysis. Compound 2a gave the stable 1, 2-dihydro derivative 6 in 77% yield on catalytic hydrogenation over Pd-C. The pyrimidine moiety of 2a has been shown to undergo ring cleavage under alkaline conditions at a rate three times faster than that of 3, 9-dimethylhypoxanthine (3a). The glycosidic bond of 2a is unusually susceptible to acidic hydrolysis and the rate was shown to be faster than that of inosine by a factor of 104.
