First, 0.48 g of 4-nitrobenzyl bromide, 0.5 g of 1,3-dimethyl-6-(piperazin -1-yl)-2,4(1H,3H)-pyrimidinedione (compound 2) and 0.5 ml of triethylamine were suspended in 5 ml of isopropanol, and the resulting suspension was then heated under reflux for 8 hours. Afterward, the used solvent was removed from the resulting reaction mixture by distillation under reduced pressure, and the residue was dissolved in chloroform and was then washed with water. The washed organic layer was dried over anhydrous sodium sulfate. Furthermore, the dried organic layer was subjected to distillation under reduced pressure so as to remove the solvent therefrom, and the residue was then purified through a silica gel column chromatograph (chloroform/methanol=50/1 to 20/1 in terms of volume ratio) in order to obtain 0.88 g of 1,3-dimethyl-6-[4-(4-nitrobenzyl)piperazin-1-yl]-2,4(1H,3H)-pyrimidinedione.
