To a solution of 3-(3-ethyl-5-isopropyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carbonyl)-5-methylbenzonitrile (778 g, 2.39 mol) in anhydrous DMF (5 L) was added 60% NaH (115 g) portion-wise over 30 min at 0° C. The reaction mixture was stirred at room temperature for 3 hours and then the mixture was cooled to −10° C. Acetic acid bromomethyl ester (321 mL) was dropwise added to the reaction mixture for 2 hours at the same temperature and the reaction mixture was stirred at room temperature for 12 hours. The mixture was diluted with water (10 L). The precipitate was collected by filtration, washed with water (5 L) and then dissolved in dichloromethane (10 L). The organic solution was washed with water (4 L), dried with anhydrous magnesium sulfate (1 kg) and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate/dichloromethane, 1:20) to give (4-(3-cyano-5-methylbenzoyl)-3-ethyl-5-isopropyl-2,6-dioxo-2,3-dihydropyrimidin-1(6H)-yl)methyl acetate (745 g, 1.87 mol, 79%) as a white solid.
