Purine Studies. XXII. Occurrence of N- and C-Methylation on Diazomethane Treatment of 2-Methylthiopurine

Abstract

Diazomethane treatment of 2-methylthiopurine gives the expected 9- methyl-2-methylthiopurine as the main product together with a smaller amount of the 7-methyl isomer. An unexpected feature of this reaction, however, is the formation also, in smaller but significant yields, of C,N-dimethylated homologues, identified as 7,8- and 8,9-dimethyl-2- methylthiopurine. Subsequent methylation studies point towards the 8-methyl group in the latter derivatives being introduced prior to the N-methylation step, thus representing an additional alkylation pathway for some purine derivatives.