[C:1]1([C@@H:7]2[CH2:11][O:10][C:9](=[O:12])[NH:8]2)[CH:6]=[CH:5][CH:4]=[CH:3][CH:2]=1.C([Li])CCC.[CH:18]1(/[CH:21]=[CH:22]/[C:23](Cl)=[O:24])[CH2:20][CH2:19]1.[NH4+].[Cl-]>C1COCC1>[CH:18]1(/[CH:21]=[CH:22]/[C:23]([N:8]2[C@H:7]([C:1]3[CH:2]=[CH:3][CH:4]=[CH:5][CH:6]=3)[CH2:11][O:10][C:9]2=[O:12])=[O:24])[CH2:20][CH2:19]1(R)-(-)-4-Phenyl-2-oxazolidinone (39.12 g, 0.240 mmol, Aldrich) was dissolved in THF (600 mL), and the solution was cooled to -78° C. and flushed with N2. n-Butyllithium (2.5M in THF, 96.0 mL, 0.240 mmol) was introduced over 25 minutes. The compound from step 1b (0.276 mmol) was added while maintaining the temperature at -78° C., and the mixture was stirred at this temperature for half an hour. The mixture was stirred as it was allowed to warm to room temperature. Saturated aqueous NH4Cl solution was added, the mixture was stirred for 10 minutes and the THF was removed under reduced pressure. The residue was dissolved in ethyl acetate, and the solution was washed with water, 5% aqueous NaHCO3 and brine, then dried over Na2SO4. The solvent was removed to afford the title compound, which was recrystallized from ethyl acetate:hexane to give the title product (54.660 g, 89% yield). MS m/z 258 (M+H)+, 275 (M+NH4)+.
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