[CH2:1]([NH:8][C:9]([NH:11][C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=1)=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[C:18](O)(=[O:23])[CH2:19][C:20](O)=[O:21].C(OC(=O)C)(=O)C>C1(C)C=CC=CC=1>[CH2:1]([N:8]1[C:18](=[O:23])[CH2:19][C:20](=[O:21])[N:11]([C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][CH:13]=2)[C:9]1=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1In a 300-ml glass flask equipped with a thermometer, a reflux condenser and a stirrer, 5.0 g of N-benzyl-N′-phenylurea synthesized in Exemplary Synthesis 1, 2.5 g of malonic acid, 20 ml of toluene, and 5.6 g of acetic anhydride were put, the content was heated under stirring so as to adjust the inner temperature to 80° C., and kept under stirring at 80° C. for 3 hours. The content was then cooled to 50° C., washed with 15 ml of water, and the aqueous phase was discarded. The organic layer was kept under stirring at room temperature, and 5 ml of isopropanol was dropped therein. The content was further stirred at 10° C. or below for 0.5 hours, filtered under suction to collect a deposited crystal, the crystal was washed with cold isopropanol, and dried, to thereby obtain 4.6 g of 1-benzyl-3-phenylbarbituric acid as an intermediate.
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