Methylation of Purin-8-ones

Abstract

In general, electrophilic alkylation of purin-8-ones takes place at the same sites as protonation. Exceptions are observed only for 3-methyl derivatives, in which cation formation involves N9, whereas methylation proceeds both at position 1 and 9. This dichotomy of alkylation is ascribed to steric interference between 3- and 9-methyl substituents.