[CH2:1]([O:8][C:9]1[CH:13]=[C:12]([CH:14]([CH3:16])[CH3:15])[S:11][C:10]=1[C:17]([O:19]C)=[O:18])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[OH-].[Li+]>O1CCCC1.CO.O>[CH2:1]([O:8][C:9]1[CH:13]=[C:12]([CH:14]([CH3:16])[CH3:15])[S:11][C:10]=1[C:17]([OH:19])=[O:18])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=11.16 g of methyl 3-benzyloxy-5-isopropyl-thiophene-2-carboxylate were dissolved in 10 ml of tetrahydrofuran (THF) and 10 ml of methanol, and a solution of 1.7 g of lithium hydroxide in 10 ml of water was added. The reaction mixture was stirred at 22° C. for 72 h. Methanol and THF were stripped off in the rotary evaporator. While cooling in ice, the reaction mixture was adjusted to pH=4 with 2 molar hydrochloric acid and extracted twice with 50 ml of ethyl acetate each time. The combined organic phases were dried over sodium sulfate and concentrated.
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