To a mixture of 4′-{[6-ethyl-3-[2-(4-hydroxyphenyl)-2-oxoethyl]-2,4-dioxo-3,4-dihydrothieno[2,3-d]pyrimidin-1(2H)-yl]methyl}biphenyl-2-carbonitrile, 2-chloro-N,N-dimethylethanamine hydrochloride (0.62 g) and N,N-dimethylformamide (7 mL) was added cesium carbonate (2.8 g), and the mixture was stirred at 60° C. for 12 hr. After allowing to cool to room temperature, ethyl acetate and water were added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was successively washed with water and saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography to give the title compound as a pale-yellow amorphous solid (0.41 g, 48%).
