[CH2:1]1[O:9][C:8]2[CH:7]=[CH:6][C:5]([CH3:10])=[CH:4][C:3]=2[O:2]1.[N+:11]([O-])([OH:13])=[O:12]>C(O)(=O)C>[N+:11]([C:6]1[CH:7]=[C:8]2[O:9][CH2:1][O:2][C:3]2=[CH:4][C:5]=1[CH3:10])([O-:13])=[O:12]To a solution of 10 (19.0 g, 139.6 mmol) in acetic acid (180 mL) was added a solution of fuming HNO3 (10 mL) in acetic acid (70 mL) dropwise over 30 minutes. The mixture was stirred at ambient temperature for 10 minutes, then poured into a beaker containing ice to give a crystalline precipitate, which was collected by vacuum filtration and washed with water to afford the crude product. Further purification via recrystallization from CH2Cl2/hexane gave the pure product (16.3 g, 64.4%).
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