B(Br)(Br)Br.[CH2:5]([NH:7][C:8]([C:10]1[C:18]2[S:17][C:16]([NH:19][C:20](=[O:24])[NH:21][CH2:22][CH3:23])=[N:15][C:14]=2[CH:13]=[C:12]([O:25]C)[CH:11]=1)=[O:9])[CH3:6]>C(Cl)Cl.CCOC(C)=O>[CH2:5]([NH:7][C:8]([C:10]1[C:18]2[S:17][C:16]([NH:19][C:20](=[O:24])[NH:21][CH2:22][CH3:23])=[N:15][C:14]=2[CH:13]=[C:12]([OH:25])[CH:11]=1)=[O:9])[CH3:6]Boron tribromide (8.72 mL, 8.72 mmol, 4M solution in DCM was added to a suspension of N-ethyl-2-(ethylcarbamoylamino)-5-methoxy-1,3-benzothiazole-7-carboxamide in dichloromethane (10 mL). The reaction was stirred at ambient temperature overnight then diluted with EtOAc, washed with saturated aqueous sodium hydrogen carbonate and brine and the organic layer dried (MgSO4), filtered and concentrated in vacuo. The crude material was purified by flash chromatography on silica gel using DCM:MeOH 95:5. The product was obtained as a white solid, 212 mg, 31% yield.
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