To a stirred solution of (2E)-3-[3-(tert-butoxycarbonyl)phenyl]prop-2-enoic acid from the previous step (0.186 g, 0.749 mmol) in THF (3 mL) was added triethylamine (0.110 mL, 0.787 mmol) and the mixture was cooled to −20° C. Pivaloyl chloride (0.0969 mL, 0.787 mmol) was added and then the reaction mixture was stirred at −20° C. for 15 min, warmed to 0° C. and stirred for 40 min. Meanwhile, to a cooled (−78° C.) solution of (R)-4-benzyl-2-oxazolidinone (0.305 g, 1.72 mmol) in THF (5 mL), was added nBuLi (1.1 mL, 1.6M in hexanes) dropwise and the mixture was stirred for 30 min. The slurry was warmed to 0° C. and added via cannula into the anion solution. After one hour, the reaction was quenched by the addition of 10 mL 20% aqueous NH4Cl solution, warmed to room temperature and extracted with 2×50 mL ether. The organic layer was washed with saturated aqueous NaHCO3 and brine, dried over MgSO4, filtered, and the solvent removed under reduced pressure, and chromatographed on a 4″ 25 mm SiO2 column using 18% EtOAc:hexanes. The clean fractions were combined and the solvent was removed under reduced pressure to give tert-butyl 3-{(1E)-3-[(4R)-4-benzyl-2-oxo-1,3-oxazolidin-3-yl]-3-oxoprop-1-enyl}benzoate as an oil (0.273 g, 89%). TLC Rf=0.3 (1:4 EtOAc:hexanes, UV visualization); HPLC RT=2.9 min, method B; M+H=408.
