[Br:1]Br.[F:3][C:4]1[CH:9]=[CH:8][C:7]([NH:10][C:11](=[O:13])[CH3:12])=[C:6]([O:14][CH3:15])[CH:5]=1>C(O)(=O)C>[Br:1][C:9]1[C:4]([F:3])=[CH:5][C:6]([O:14][CH3:15])=[C:7]([NH:10][C:11](=[O:13])[CH3:12])[CH:8]=1Bromine (1.8 ml, 34 mmol) was added dropwise to a solution of the product of Step 1 (5.69 g, 31 mmol) in acetic acid (100 ml). After 18 hours at room temperature additional bromine (0.3 ml) was added and the solution stirred for a further 3 hours. The solution was partitioned between water and ethyl acetate and the layers separated. The organic phase was then washed with aqueous sodium thiosulfate solution, water and brine, dried over anhydrous magnesium sulfate and concentrated in vacuo to give the title compound. MS (ES+) m/e 262/264 [M+H]+.
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