[C:1]([O:5][C:6]([C:8]1[S:9][C:10](/[CH:13]=[C:14](/[C:17]([O:19]C)=[O:18])\[CH2:15][CH3:16])=[CH:11][CH:12]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2].CO.[OH-].[Li+]>O1CCCC1>[C:1]([O:5][C:6]([C:8]1[S:9][C:10](/[CH:13]=[C:14](\[CH2:15][CH3:16])/[C:17]([OH:19])=[O:18])=[CH:11][CH:12]=1)=[O:7])([CH3:4])([CH3:3])[CH3:2]5-[(1E)-2-(Methoxycarbonyl)-but-1-en-1-yl]thiophene-2-carboxylic acid tert-butyl ester (34.6 g, 120 mol) was dissolved in tetrahydrofuran (150 mL), and methanol (60 mL), 1 N lithium hydroxide solution (144 mL, 144 mmol) was added, and the mixture was stirred at room temperature for 2 days. The mixture was concentrated under reduced pressure. 0.5 N-Hydrochloric acid solution and ethyl acetate were added to the obtained residue, the organic layer was separated, and the aqueous layer was extracted three times with ethyl acetate. The organic layers were combined, washed with brine, and dried over anhydrous magnesium sulfate. After filtration, the solvent of the filtrate was evaporated under reduced pressure to give the title compound (32.2 g, 114 mmol, 95%).
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