2-(6?,8?,9?-Trimethylpurin-2?-ylthio)acetamide (1e) and analogous N- substituted acetamides are prepared by treatment of 6,8,9- trimethylpurine-2-thione (3a) with an appropriate 2- chloroacetamide. 6,9-Dimethyl-2-(piperidin-1?-yl)purine (In) and some 2- polymethyleneamino homologues are made by initial amination of 2- chloro-4-methyl-6-methylamino-5-nitropyrimidine (2b) followed by reduction of the nitro group and final cyclization with formic acid. Such purines enhance the lethal effect of phleomycin on Escherichia coli cultures.