[O:1]=[C:2]1[C:7]2[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=2[N:5]=[C:4]([C:12]2[CH:17]=[CH:16][CH:15]=[CH:14][C:13]=2[NH:18][S:19]([C:22]2[CH:31]=[CH:30][C:29]3[C:24](=[CH:25][CH:26]=[CH:27][CH:28]=3)[CH:23]=2)(=[O:21])=[O:20])[O:3]1.[OH-].[Na+].Cl.[CH2:35]([OH:37])[CH3:36]>>[CH2:35]([O:37][C:2](=[O:1])[C:7]1[CH:8]=[CH:9][CH:10]=[CH:11][C:6]=1[NH:5][C:4](=[O:3])[C:12]1[CH:17]=[CH:16][CH:15]=[CH:14][C:13]=1[NH:18][S:19]([C:22]1[CH:31]=[CH:30][C:29]2[C:24](=[CH:25][CH:26]=[CH:27][CH:28]=2)[CH:23]=1)(=[O:21])=[O:20])[CH3:36]A 1 L three-necked flask was charged with 67.7 g (0.158 mol) N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]-2-naphthalenesulfonamide) and 200 g ethanol. Under stirring, 0.33 g sodium hydroxide (0.0083 mol, correlates to 5.2% of applied raw material) was added. After 15 minutes, the reaction mixture was heated until reflux for 5 hours. Completion of the reaction was monitored by thin layer chromatography. After the 5 hours, the intermediate mixture was cooled to 20° C., and within 20 minutes 4.5 g of 10% hydrochloric acid solution (0.012 mol) was added drop wise. The precipitate consisted of tiny white crystals, and was stirred for 1 hour at room temperature, then filtered by suction, washed with first 150 ml ethanol, then 300 ml water and dried at 85° C. in a circulating air oven.
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