F[C:2]1[CH:7]=[C:6](F)[CH:5]=[CH:4][C:3]=1[CH2:9][CH2:10]C(O)=O.[CH3:14][C:15]([CH3:20])(C)[C:16](Cl)=[O:17].[Li+].[Cl-].C[C@H]1[C@@H](C2C=CC=CC=2)[O:27][C:26](=[O:35])[NH:25]1.[CH2:36](N(CC)CC)[CH3:37]>C1COCC1>[CH3:14][C:15](=[CH:20][CH2:36][CH3:37])[C:16]([N:25]1[CH:9]([C:3]2[CH:2]=[CH:7][CH:6]=[CH:5][CH:4]=2)[CH2:10][O:35][C:26]1=[O:27])=[O:17]A flask was charged with 29.5 g (158 mmol) of 3-(2,4-difluoro-phenyl)-propionic acid, 700 mL of THF, and 82.8 mL of triethylamine. The mixture was cooled to 0° C. and 23.4 mL of trimethyl acetyl chloride was added slowly. The mixture was stirred cold for 1 hour. Then 8.06 g (190 mmol) of LiCl and 28.1 g of (4S,5R)-4-methyl-5-phenyl-oxazolidin-2-one was added. The mixture was allowed to warm room temperature and stirred overnight. The solids were filtered off, and the solvent was removed under reduced pressure. The residue was taken up in diethyl ether and washed with sat. aq. ammonium chloride, sat. aq. sodium bicarbonate, and the solvent were removed under reduced pressure. The crude residue was purified by column chromatography (3:1 dichloromethane/hexanes eluent) to give 54 g (99% yield) of the titled compound.
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