[CH:1]1([CH:6]([C:11]2[CH:16]=[CH:15][C:14]([C:17]([F:20])([F:19])[F:18])=[CH:13][CH:12]=2)[C:7]([O:9]C)=[O:8])[CH2:5][CH2:4][CH2:3][CH2:2]1.C1COCC1.[OH-].[Li+].Cl>O.CO>[CH:1]1([CH:6]([C:11]2[CH:16]=[CH:15][C:14]([C:17]([F:18])([F:19])[F:20])=[CH:13][CH:12]=2)[C:7]([OH:9])=[O:8])[CH2:5][CH2:4][CH2:3][CH2:2]14.98 g (17.4 mmol) of methyl cyclopentyl[4-(trifluoromethyl)phenyl]acetate were initially charged in a mixture of in each case 24.9 ml of THF, methanol and water, and 1.04 g (43.49 mmol) of lithium hydroxide were added at 0° C. The reaction mixture was warmed to RT and stirred at this temperature for 4 h. The mixture was then diluted with water and acidified slightly with 1 N hydrochloric acid. The aqueous phase was extracted three times with ethyl acetate. The combined organic phases were dried over magnesium sulphate and concentrated under reduced pressure. This gave 4.56 g of the target compound as a crude product (yield 96.3% of theory).
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