C([O:3][C:4](=[O:21])[CH:5]([C:7]1[CH:12]=[CH:11][C:10]([N:13]2[CH2:17][CH2:16][CH2:15][S:14]2(=[O:19])=[O:18])=[C:9]([F:20])[CH:8]=1)[CH3:6])C.[Li+].[OH-].Cl>C1COCC1.O>[O:19]=[S:14]1(=[O:18])[CH2:15][CH2:16][CH2:17][N:13]1[C:10]1[CH:11]=[CH:12][C:7]([CH:5]([CH3:6])[C:4]([OH:21])=[O:3])=[CH:8][C:9]=1[F:20]2-[4-(1,1-Dioxo-[1,2]thiazolidin-2-yl)-3-fluoro-phenyl]-propionic acid ethyl ester (448 mg, 1.42 mmol) was dissolved in a 2:1 mix of THF/water (2.8 mL+1.4 mL) and stirred for 15 min. 3 equivalents of LiOH (98 mg, 4.26 mmol), which is also dissolved in a 2:1 THF/water mix (1 mL+0.5 mL), are added to this solution. The reaction mixture was stirred overnight under reflux. While cooling, the aqueous phase is set to pH 1 using 4 N aq. HCl and repeatedly extracted with ethyl acetate (3×10 mL). The combined organic phases are dried over magnesium sulfate and concentrated under reduced pressure to afford 2-[4-(1,1-dioxo-[1,2]thiazolidin-2-yl)-3-fluoro-phenyl]-propionic acid (350 mg, 86%).
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