[CH2:1]([O:3][P:4]([C:9]([C:12]1[CH:21]=[C:20]2[C:15]([CH:16]=[CH:17][C:18]([CH:22]=[O:23])=[N:19]2)=[CH:14][C:13]=1[Br:24])([F:11])[F:10])(=[O:8])[O:5][CH2:6][CH3:7])[CH3:2].[OH:25]O>C(O)=O>[Br:24][C:13]1[CH:14]=[C:15]2[C:20](=[CH:21][C:12]=1[C:9]([P:4]([O:5][CH2:6][CH3:7])([O:3][CH2:1][CH3:2])=[O:8])([F:10])[F:11])[N:19]=[C:18]([C:22]([OH:25])=[O:23])[CH:17]=[CH:16]2As described in the literature (Synthesis, 1993, 295), to the product of step 4 (105 mg, 0.25 mmol) in 1 ml formic acid was added 30% hydrogen peroxide (0.13 mL, 1 mmol) dropwise and the mixture was stirred overnight at rt. The solvent was evaporated and absolute ethanol was added. This was repeated 3 times and after evaporation of the remaining ethanol yielded the title product as an oil.
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