To a stirred solution of quinoxalin-6-ol (King et al.; J. of the Chem. Society 1949:3012.) (11.2 g, 76.66 mmol) in tetrahydrofuran (800 mL) was added isopropylmagnesium chloride (38.3 mL, 2.0 M THF solution, 76.60 mmol) at −40° C. to −30° C. The mixture was allowed to stir at 0° C. for 2 h, followed by the addition of 1-(diphenylmethyl)-1H-indole-2,3-dione (20.00 g, 63.84 mmol) in tetrahydrofuran (400 mL). The mixture was stirred at ambient temperature for 20 h, and quenched with saturated ammonium chloride solution and extracted with ethyl acetate (3×1000 mL). The organic layer was washed with water and brine, dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo, and the residue was purified by column chromatography (dichloromethane/methanol, 100/1) to give 1-(diphenylmethyl)-3-hydroxy-3-(7-hydroxyquinoxalin-6-yl)-1,3-dihydro-2H-indol-2-one (10.0 g, 34%): 1H NMR (300 MHz, CDCl3) δ 10.21 (s, 1H), 8.47 (s, 1H), 7.97-7.92 (m, 2H), 7.60-7.58 (m, 2H), 7.54-7.49 (m, 4H), 7.46-7.35 (m, 6H), 7.14 (s, 1H), 7.05-7.00 (m, 1H), 6.89-6.87 (m, 1H), 6.56-6.52 (m, 1H).
