... M. Nishii, J. Inagaki, F. Nohara, K. Isono ... Until the tautomeric structure is established, we prefer to use the N(7)-H structure (20) because the UV spectrum of 3-methylhypo- xanthinem' is dissimilar to that of 3,9—dimethylhypoxanthine [T. Itaya and K. Ogawa, Chem. Pharm. ...