[C:1]([N:5]1[C:9](=[O:10])[C:8]([NH:11][CH2:12][C:13]([O:15]C)=[O:14])=[C:7]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)[S:6]1(=[O:24])=[O:23])([CH3:4])([CH3:3])[CH3:2].CO.[Li+].[OH-].Cl>O1CCOCC1.O>[C:1]([N:5]1[C:9](=[O:10])[C:8]([NH:11][CH2:12][C:13]([OH:15])=[O:14])=[C:7]([C:17]2[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=2)[S:6]1(=[O:24])=[O:23])([CH3:4])([CH3:2])[CH3:3]Methyl [(2-tert-butyl-1,1-dioxido-3-oxo-5-phenyl-2,3-dihydroisothiazol-4-yl)amino]acetate (1.28 g, 3.64 mmol) was dispersed in a mixture of dioxane (20 mL), MeOH (20 mL) and water (20 mL). Aqueous LiOH (1M, 0.218 g, 9.10 mmol) was added and the reaction mixture was stirred at rt for 2 h. Aqueous HCl was carefully added to the reaction mixture to give the pH˜1 and the resulting mixture was extracted with DCM. The organic phases were combined, dried over Na2SO4, filtered, evaporated and the crude residue was purified by preparative HPLC giving the title compound (0.51 g, 41%). 1H-NMR (CD3OD, 500 MHz): δ 7.52-7.48 (m, 2H), 7.46-7.42 (m, 3H), 5.41 (brs, 8H) 1.95 (s, 2H), 1.71 (s, 9H); 13C-NMR (CD3OD, 125 MHz): δ 178.4, 174.8, 160.8, 136.5, 132.8, 130.4, 129.5, 126.6, 107.4, 62.1, 48.3, 27.9, 22.9.
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