To a solution of 4-(2-hydroxyphenyl)-N-(4-methoxybenzyl)-N-(thiazol-2-yl)-3,4-dihydro-2H-benzo[b][1,4]oxazine-7-sulfonamide (550 mg, 1.080 mmol), 2-bromoacetamide (704 mg, 5.108 mmol, Aldrich) in DMF (10 mL) was added potassium carbonate (528 mg, 3.83 mmol). The reaction mixture was heated at 80° C. for 12 h. After completion, the reaction mixture was cooled to room temperature, diluted with water (50 mL) and extracted with ethyl acetate (2×50 mL). The combined organic layer was washed with water (50 mL), dried over sodium sulfate and concentrated under reduced pressure to obtain the crude material which was purified by combiflash column chromatography (column size: 12 g; elution: 0-60% ethyl acetate in hexane) to get 2-(2-(7-(N-(4-methoxybenzyl)-N-(thiazol-2-yl)sulfamoyl)-2H-benzo[b][1,4]oxazin-4(3H)-yl)phenoxy)acetamide (300 mg, 49.0%). MS (ESI, positive ion) m/z; 567.1 (M+1)
