To a solution of methyl 3-[4-(6-chloro-3-formyl-1H-indol-5-yl)phenyl]pyrrolidine-1-carboxylate (124 mg, 0.325 mmol) in acetonitrile (4 mL) and tert-butanol (4 mL) was added 2-methyl-2-butene (4 mL). The reaction mixture was cooled to 0° C. and treated with a solution of sodium chlorite (327 mg, 3.59 mmol) and sodium phosphate monobasic dihydrate (761 mg, 4.875 mmol) in water (2 mL). After the resulting mixture was stirred for 2 hours at room temperature, additional sodium chlorite (435.5 mg, 4.79 mmol) and sodium phosphate monobasic dihydrate (1.014 g, 6.5 mmol) in water (2 mL) and 2-methyl-2-butene (1 mL) was added. The resulting mixture was stirred at room temperature for 16 h. The reaction mixture was evaporated in vacuo and the aqueous residue was extracted with EtOAc (3×20 mL). The combined organic layers were dried over Na2SO4 and concentrated in vacuo. The residue was dissolved in DMSO and purified via prep-HPLC to give 6-chloro-5-{4-[1-(methoxycarbonyl)pyrrolidin-3-yl]phenyl}-1H-indole-3-carboxylic acid (60 mg, 46%) as a white solid. The racemic mixture was separated by preparative chiral SFC to give 16 mg of peak 1 or Example 14A (>99% ee, ret time=4.73 minutes), and 17 mg of peak 2 or Example 14B (>93% ee, ret time=5.33 minutes) using ChiralPak AD-H Minigram-1, 60/40 CO2/MeOH 0.2% isopropylamine, 10 mL/min, 120 Bar. MS (ES+) 398.9 (M+H)+. 1H NMR (400 MHz, DMSO-d6) δ 12.14 (br, 1H), 11.97 (s, 1H), 8.08 (d, 1H), 7.94 (s, 1H), 7.61 (s, 1H), 7.38 (m, 4H), 3.81 (m, 1H), 3.61 (s, 3H), 3.54 (m, 1H), 3.40 (m, 2H), 3.28 (m, 1H), 2.25 (m, 1H), 2.00 (m, 1H).
