To a mixture of racemic (2′R,3R,4′S)-6-bromo-4′-(3-chlorophenyl)-2′-isopropenyl-2,3-dihydro-2,6′-dioxospiro[indole-3,3′-piperidine]-1-methoxyethyl trimethylsilane (100 mg, 0.17 mmol) and 2-bromo-acetamide (72 mg, 0.52 mmol) in DMF (1 mL) was added Cs2CO3 (332 mg, 1.01 mmol). The mixture was stirred at room temperature for overnight. Then additional 2-bromo-acetamide (72 mg, 0.52 mmol) and Cs2CO3 (332 mg, 1.01 mmol) were added to the reaction mixture. The resulting mixture was heated at 50° C. for 2 h, then poured into ethyl acetate (20 mL). The organic layer was washed with water 3 times, dried over Na2SO4, purified by column chromatography to give title compound 60 mg.
