[OH:1][CH:2]1[C:7]2[CH:8]=[C:9]([S:11]([NH:14][C:15]([CH3:18])([CH3:17])[CH3:16])(=[O:13])=[O:12])[S:10][C:6]=2[S:5](=[O:20])(=[O:19])[NH:4][CH2:3]1.CC(C)=O.OS(O)(=O)=O.O=[Cr](=O)=O.OS(O)(=O)=O>CC(C)=O.O>[CH3:18][C:15]([NH:14][S:11]([C:9]1[S:10][C:6]2[S:5](=[O:20])(=[O:19])[NH:4][CH2:3][C:2](=[O:1])[C:7]=2[CH:8]=1)(=[O:13])=[O:12])([CH3:16])[CH3:17]To a solution of 3,4-dihydro-4-hydroxy-N-(1,1-dimethylethyl)-2H-thieno[3,2-e]-1,2-thiazine-6-sulfonamide 1,1-dioxide (3.36 g, 9.87 mmol) in acetone (15 mL) at room temperature was added Jones reagent [2 mL (prepared by dissolving CrO3 (7 g) in H2O (50 mL) and adding H2SO4 (6.1 mL)]. The mixture was stirred at room temperature for one hour, solvent was evaporated and the residue dissolved in ethyl acetate (75 mL). This solution was washed with saturated aqueous sodium bicarbonate until the the organic layer was neutral. The aqueous layer was separated and washed with ethyl acetate (3'25 mL). The combined extracts were dried (NaSO4) and evaporated to provide a residue which was purified by column chromatography (silica, 40% ethyl acetate in hexane) to give an off-white solid (2.74 g, 82%): mp 170°-172° C.
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