Purines. LXXII. Oxidation of N6-Alkyladenines with m-Chloroperoxybenzoic Acid Leading to N6-Alkyladenine 1-Oxides

Oxidations of N6-methyladenine (8a) and N6-benzyladenine (8b) with m-chloroperoxybenzoic acid (MCPBA) in methanol have been found to afford the N(1)-oxides 7a, b in 36% and 35% yields, respectively. The structure of 7b has been established by leading it to N6-methoxyadenine (10) through O-methylation, Dimroth rearrangement, and nonreductive debenzylation. On the other hand, N6, N6-dimethyladenine (16) afforded the N(3)-oxide 17 in 40% yield on treatment with MCPBA in methanol. On the basis of these findings, together with data accumulated for N-oxidations of adenine, Nx-monosubstituted adenines, and 6-substituted purines, the formation of hydrogen bonding between the 6-amino NH and the carbonyl oxygen of a peroxycarboxylic acid may account for regioselective N(1)- and N(7)-oxidations of adenine and Nx-monosubstituted adenines.