An unusual oxidative ring transformation of purine to imidazo[1,5-c]imidazole

reaction: see text] Reevaluation of products derived from 3,9-dimethyluric acid in a chlorination-reductive dechlorinaton sequence has demonstrated unequivocally that they are not purines. Spectroscopic and degradative evidence, in conjunction with position-labeling NMR studies, revealed an unprecedented oxidative ring transformation pathway involving the key purine-to-imidazo1,5-c]imidazole rearrangement.