[C:1]([O:5][C:6]([N:8]1[C@@H:12]([C@@H:13]([OH:25])[C@@H:14]([NH2:24])[CH2:15][C:16]2[CH:21]=[C:20]([F:22])[CH:19]=[C:18]([F:23])[CH:17]=2)[CH2:11][O:10][C:9]1([CH3:27])[CH3:26])=[O:7])([CH3:4])([CH3:3])[CH3:2].C(N(CC)CC)C.[C:35](OC(=O)C)(=[O:37])[CH3:36]>O1CCCC1.C(OCC)(=O)C>[C:1]([O:5][C:6]([N:8]1[C@@H:12]([C@@H:13]([OH:25])[C@@H:14]([NH:24][C:35](=[O:37])[CH3:36])[CH2:15][C:16]2[CH:17]=[C:18]([F:23])[CH:19]=[C:20]([F:22])[CH:21]=2)[CH2:11][O:10][C:9]1([CH3:27])[CH3:26])=[O:7])([CH3:4])([CH3:2])[CH3:3]Dissolve (R)-4-[(1S,2S)-2-amino-3-(3,5-difluorophenyl)-1-hydroxypropyl]-2,2-dimethyloxazolidine-3-carboxylic acid tert-butyl ester (920 mg, 2.38 mmol) in dry tetrahydrofuran (20 ml) under an atmosphere of nitrogen. Add to the resulting solution triethylamine (400 μl, 2.87 mmol) and acetic anhydride (235 μL, 2.49 mmol). After 1 hour, dilute with ethyl acetate and wash with water (twice), 0.1 N hydrochloric acid, and saturated aqueous sodium chloride. Dry (magnesium sulfate), filter, concentrate and purify (silica gel chromatography 0:100 to 70:30 ethyl acetate:hexanes) to give the desired compound as a white solid (738 mg, 72% yield).
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