[Br:1][C:2]1[C:11](=[O:12])[C:10]2[C:5](=[CH:6][C:7]([OH:13])=[CH:8][CH:9]=2)[O:4][C:3]=1[CH:14]([CH3:16])[CH3:15].[N+:17]([O-])([OH:19])=[O:18]>S(=O)(=O)(O)O>[Br:1][C:2]1[C:11](=[O:12])[C:10]2[C:5](=[C:6]([N+:17]([O-:19])=[O:18])[C:7]([OH:13])=[CH:8][CH:9]=2)[O:4][C:3]=1[CH:14]([CH3:16])[CH3:15]3-Bromo-7-hydroxy-2-isopropyl-chromen-4-one (778 mg, 2.75 mmol) is dissolved in concentrated sulphuric acid (4 ml), and the solution is cooled to 0° C. A solution of fuming nitric acid (189 mg, 3 mmol) in concentrated sulphuric acid (1 ml) is added dropwise. The mixture is stirred at 0° C. for 30 min, poured onto ice, recovered by filtration and dried to give a cream-coloured solid.
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