To a mixture of 6-chloro-7,9-dihydro-9-methyl-2-phenyl-8H-purin-8-one (1.6 g), potassium carbonate (1.0 g) and dimethylformamide (15 ml) is added 2-chloro-N-ethyl-N-phenylacetamide (1.4 g) at room temperature, and the mixture is stirred at the same temperature for two hours. To the reaction mixture is added water, and the precipitates are collected by filtration, washed with water, and purified by silica gel column chromatography (eluent; chloroform), and recrystallized from ethanol to give the desired compound (1.8 g).
