[N+:1]([C:4]1C(=O)[O:6][C:7]2[C:12]([C:13]=1[OH:14])=[CH:11][CH:10]=[C:9]([O:15][CH3:16])[CH:8]=2)([O-:3])=[O:2].Cl>[OH-].[Na+]>[OH:6][C:7]1[CH:8]=[C:9]([O:15][CH3:16])[CH:10]=[CH:11][C:12]=1[C:13](=[O:14])[CH2:4][N+:1]([O-:3])=[O:2]3-Nitro-4-hydroxy-7-methoxy coumarin (1.85 g, 0.078 m), prepared as described in D. R. Buckle, et al., J. Med. Chem., 18, 391 (1975), was stirred at room temperature in 5% aqueous sodium hydroxide (60 ml) for 20 hours. The mixture was slowly acidified with 5N HCl. The product was filtered off and sucked dry. Recrystallization from absolute ethanol gave pale yellow crystals (0.92 g, 56%), m.p. 138°-40° C.
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