To a solution of [4-(3-nitro-benzenesulfonylamino)-4,5,6,7-tetrahydro-indazol-1-yl]-acetic acid ethyl ester (390 mg, 0.96 mmol) in acetic acid (3 mL) and ethanol (15 mL) was added zinc powder portionwise. After being heated at reflux for 2 hours, the mixture was cooled to room temperature, diluted with dichloromethane (30 mL) and filtered through a glass funnel and concentrated in vacuo. The residue was purified by flash column (gradient elution, 0-5% methanol in dichloromethane) to afford [4-(3-amino-benzenesulfonylamino)-4,5,6,7-tetrahydro-indazol-1-yl]-acetic acid ethyl ester (300 mg, 83%) as a semisolid. MS cald. for C17H22N4O4S 378, obsd. (ESI+) [(M+H)+] 379.
