[N+]([O-])(O)=[O:2].C(O[C:13]1[CH:14]=[C:15]2[C:20](=[CH:21][CH:22]=1)[O:19][C:18](=[O:23])[CH:17]=[C:16]2[OH:24])C1C=CC=CC=1.[OH-:25].[Na+]>C(Cl)(Cl)Cl.C1C=CC=CC=1.O>[OH2:2].[OH:24][C:16]1[C:15]2[C:20](=[CH:21][C:22]([OH:25])=[CH:13][CH:14]=2)[O:19][C:18](=[O:23])[CH:17]=1Fuming nitric acid (13 ml) was added to a stirred suspension of 6-benzyloxy-4-hydroxycoumarin (m.p. 226°-8°; 3.13g) in chloroform (200 ml) at room temperature over 1.5 hours. After a further 1.5 hours, the solvent was removed in vacuo at room temperature and water (100 ml) added to the residue. Filtration gave an oily solid which was dissolved in benzene, filtered, and the filtrate evaporated to dryness to give a yellow solid, decomp. 170°. The solid was suspended in water (30 ml) and dilute sodium hydroxide solution added till the pH of the solution reached 14. Filtration gave the product, m.p. 262°-4°(d). (C10H10NO6Na requires C, 57.32; H, 3.01; N, 4.18; Na, 6.86. Found: C, 57.44; H, 3.31; N, 4.34; Na, 6.86. Found: C, 57.44; H, 3.31; N, 4.34; Na, 6.67) after washing with water and drying under vacuum.
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