Br[C:2]1[CH:7]=[CH:6][C:5]([Br:8])=[CH:4][CH:3]=1.[Li]CCCC.[F:14][C:15]1[CH:29]=[C:28]([F:30])[CH:27]=[CH:26][C:16]=1[CH:17]=[N:18][CH:19]([CH2:22][CH:23]([CH3:25])[CH3:24])[CH2:20][OH:21]>CCOCC>[Br:8][C:5]1[CH:6]=[CH:7][C:2]([C@H:17]([NH:18][C@@H:19]([CH2:22][CH:23]([CH3:25])[CH3:24])[CH2:20][OH:21])[C:16]2[CH:26]=[CH:27][C:28]([F:30])=[CH:29][C:15]=2[F:14])=[CH:3][CH:4]=1To a solution of 1,4-dibromobenzene (24.5 g, 100 mmol, 5eq) in dry ether (200 mL) under nitrogen atmosphere at −30° C., nBuLi (64.75 mL, 1.6 M solution in hexanes, 5 eq) was added and the reaction mixture was stirred for 1 h. A solution of 2-[(2,4-difluorobenzylidene)-amino]-4-methylpentan-1-ol (5 g, 20 mmol) in dry ether was added slowly at −30° C. After stirring for 4 h, the reaction was quenched with water. The ether layer was washed with saturated solution of NaCl, and dried over MgSO4. The solvent was removed under reduced pressure and the crude was flash chromatographed on 500 cm3 of silica gel using 8:2 hexanes:EtOAc as an eluant to yield (2S)-2-{(S)-[(4-bromophenyl)-(2,4-difluorophenyl)-methyl]-amino}-4-methylpentan-1-ol.
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