[CH:1]1[C:9]2[C:8]3[CH:10]=[CH:11][CH:12]=[CH:13][C:7]=3[O:6][C:5]=2[CH:4]=[CH:3][C:2]=1[C:14](=[O:22])[CH:15]([F:21])[CH:16]([F:20])[C:17]([OH:19])=[O:18].C([N-]C(C)C)(C)C.[Li+].[CH2:31](Br)[CH2:32][C:33]1[CH:38]=[CH:37][CH:36]=[CH:35][CH:34]=1>O1CCCC1>[CH:1]1[C:9]2[C:8]3[CH:10]=[CH:11][CH:12]=[CH:13][C:7]=3[O:6][C:5]=2[CH:4]=[CH:3][C:2]=1[C:14](=[O:22])[CH:15]([F:21])[C:16]([F:20])([CH2:31][CH2:32][C:33]1[CH:38]=[CH:37][CH:36]=[CH:35][CH:34]=1)[C:17]([OH:19])=[O:18]To a solution of 4-dibenzofuran-2-yl-2,3-difluoro-4-oxo-butyric acid (1 equivalent, Example 6) in tetrahydrofuran cooled to -78° C. is added dropwise a solution of lithium diisopropylamide (2 equivalents). After stirring at -78° C. for 30 minutes, a solution of phenethyl bromide (1 equivalent) in tetrahydrofuran is added. The cooling bath is removed, and the reaction mixture gradually warms to room temperature and is stirred overnight. To this solution is added aqueous HCl (1 M) and ethyl acetate. The layers are separated, and the organic portion is washed with brine, dried (MgSO4), and concentrated in vacuo. The title compound is obtained by separation from the reaction by-product using silica gel chromatography (elution with chloroform/methanol).
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