To a solution of (E)-3-(1-(tert-butoxycarbonyl)-1H-indol-3-yl)acrylic acid (7.14 g, 24.85 mmol) in THF (400 mL) at −78° C. were added Et3N (10.39 ml, 74.6 mmol) and pivaloyl chloride (6.12 ml, 49.7 mmol). The mixture was stirred for 15 min at −78° C. then warmed to 0° C. for 1.5 h. The mixture was cooled to −78° C., to which was added n-Butyllithium (1.6 M in Hexanes)(14 mL, 22.4 mmol), then added the lithium salt of (R)-4-phenyl-2-oxazolidinone [prepared by adding n-Butyllithium (1.6 M in Hexanes)(31 ml, 49.7 mmol), to a solution of (R)-4-phenyloxazolidin-2-one (8.11 g, 49.7 mmol)] in THF (200 mL) at −78° C.) via cannula. The reaction was stirred at −78° C. for 2 h then at rt for 16 h. The reaction was quenched with saturated NH4Cl aqueous solution. The organics were removed under vacuum and the aqueous was extracted with EtOAc. The organic layer was collected, washed with brine, dried over sodium sulfate, and concentrated under vacuum. The crude product was purified by silica gel chromatography using a gradient of 10-20% EtOAc/Hexanes. The product fractions were collected and the solvent removed under vacuum to give ((R,E)-tert-butyl 3-(3-oxo-3-(2-oxo-4-phenyloxazolidin-3-yl)prop-1-en-1-yl)-1H-indole-1-carboxylate, 7.12 g (66%). ESI-MS (+) m/z 433.4 (M+1).
