To a mixture of racemic (2′R,3R,4′S)-4′-(2-amino-5-chloro-phenyl)-6-chloro-2′-isopropenylspiro[3H-indole-3,3′-piperidine]-2,6′(1H)-dione (40 mg, 0.1 mmol), acetic acid (9 mg, 0.15 mmol), EDCI.HCl (29 mg, 0.15 mmol), and HOBt (20 mg, 0.15 mmol) in acetonitrile (5 mL) was added DIPEA (0.052 mL, 0.3 mmol) at r.t. The reaction mixture was stirred for 4 h. The mixture was concentrated and partitioned between ethyl acetate and water. The organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layers were dried over MgSO4 and concentrated. The residue was purified with Prep HPLC to give the title compound as a white solid (Yield: 9 mg).
