Reactions of some 6-mercapto-8-(3-pyridyl)purines with methyl iodide

Abstract

6-Mercapto-8-(3-pyridyl)purine (I) undergoes S-methylation when treated with methyl iodide in dimethylform-amide. In the presence of an excess of methyl iodide quaternization of the pyridine nitrogen atom occurs, to give the intermediate (III), followed by methylation at N-3 of the purine nucleus. Simultaneously with this last step, a small percentage of (III) suffers S-demethylation, so that the end product is a mixture of the exhaustively methylated material (VI) with some N-quaternary mercaptopurine (V).