C[O:2][C:3](=[O:17])[CH2:4][C:5]1[CH:10]=[CH:9][CH:8]=[C:7]([S:11](=[O:16])(=[O:15])[NH:12][CH2:13][CH3:14])[CH:6]=1.O[Li].O>C1COCC1.O.C(OCC)(=O)C.C(O)(=O)CC(CC(O)=O)(C(O)=O)O>[CH2:13]([NH:12][S:11]([C:7]1[CH:6]=[C:5]([CH2:4][C:3]([OH:17])=[O:2])[CH:10]=[CH:9][CH:8]=1)(=[O:16])=[O:15])[CH3:14](3-Ethylsulfamoyl-phenyl)-acetic acid methyl ester (0.28 g, 1.1 mmol) was dissolved in THF and LiOH hydrate (63 mg, 1.5 mmol) in water was added. The reaction mixture was stirred at room temperature for 4 hours and then diluted with ethyl acetate and 10% citric acid. The organic layer was washed with brine, dried over sodium sulfate, and concentrated to a solid. 0.25 g, 1.1 mmol 99% yield. 1H NMR 500 MHz (DMSO) 7.71 ppm, 1H, s; 7.70 ppm, 1H, m; 7.50 ppm, 3H, m; 4.11 ppm, 1H, br s; 3.70 ppm, 2H, s; 2.81 ppm, 2H, m; 0.99 ppm, 3H, t.
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