Purines. LXXIV. Syntheses and Rearrangements of 8-Oxoadenines Monomethylated at the N6-, 1-, and 3-Positions

On treatment with boiling 2 N hydrochloric acid for 48 h, N6-methyl-8-oxoadenosine (1), 1-methyl-8-oxoadenosine (5), and 7-methyl-8-oxoadenosine (8) underwent glycosidic hydrolysis, though much more slowly than the corresponding 8-unsubstituted compounds, furniching the aglycons (2, 6, and 9) in 45%-63% yields. Under these conditions, N6-methyl-8-oxoadenine (2) rearranged to 9-methyl-8-oxoadenine (3) (8% yield), presumably through fission and reclosure of the imidazole ring. Apparent methyl migration also occurred with 3-methyl-8-hydroxyadenine (7), which afforded 1-methyl-8-oxoadenine (6) in 9% yield on treatment with hydrochloric acid under similar conditions.