[F:1][C:2]([F:15])([F:14])[S:3]([O:6]S(C(F)(F)F)(=O)=O)(=[O:5])=[O:4].[CH3:16][C:17]([CH3:33])([CH3:32])[C:18]([NH:20][C:21]1[CH:30]=[CH:29][CH:28]=[C:27](O)[C:22]=1[C:23]([O:25][CH3:26])=[O:24])=[O:19].N1C=CC=CC=1>C(Cl)Cl>[CH3:16][C:17]([CH3:33])([CH3:32])[C:18]([NH:20][C:21]1[CH:30]=[CH:29][CH:28]=[C:27]([O:6][S:3]([C:2]([F:15])([F:14])[F:1])(=[O:5])=[O:4])[C:22]=1[C:23]([O:25][CH3:26])=[O:24])=[O:19]Trifluoromethanesulphonic anhydride (6.2 g) was added dropwise to an ice cooled, stirred solution of methyl 2-(2,2-dimethylpropionylamino)-6-hydroxybenzoate (Intermediate 40, 5.02 g) and pyridine (3.16 g) in DCM (70 mL) and the mixture was stirred for 1 hour. The resulting solution was washed with 2M hydrochloric acid, filtered through a phase separator and the filtrate was evaporated in vacuo. The residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane with a gradient of 0-15% to give methyl 2-(2,2-dimethylpropionylamino)-6-trifluoromethanesulfonyloxybenzoate (7.09 g) as a colourless oil.
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