A solution of 80 mg (0.25 mmol) of 9-benzyl-4-carbamoyl-5-hydroxy-1,2,3,4-tetrahydrocarbazole in 2.5 mL of DMF was treated with 61 mg (0.30 mmol) of Cs2CO3 followed by 26 mg (0.30 mmol) of methyl bromoacetate. The mixture was stirred at room temperature until tlc indicated complete consumption of starting material (2 hours). The reaction was diluted with H2O (10 mL) and was extracted with EtOAc (3×10 mL). The combined organic layers were washed with H2O (3×20 mL), dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified by radial chromatography (SiO2; 2.5% MeOH in CH2Cl2) to afford 50 mg (0.13 mmol; 51%) of [9-benzyl-4-carbamoyl-1,2,3,4-tetrahydrocarbazole-5-yl]oxyacetic acid, methyl ester as an oil. 1H NMR (CDCl3) δ 7.33-7.21 (m, 3H), 7.05-6.98 (m, 3H), 6.98 (d, 1H, J=7.4 Hz), 6.46 (br s, 1H), 6.37 (d, 1H, J=7.7 Hz), 5.52 (br s, 1H), 5.23 (d, 1H, J=4.9 Hz), 4.79-4.70 (m, 2H), 4.20-4.15 (m, 1H), 3.81 (s, 3H), 2.79-2.69 (m, 1H), 2.63-2.49 (m, 1H), 2.43-2.35 (m, 1H), 2.25-2.09 (m, 1H), and 1.99-1.78 (m, 2H). IR (CHCl3, cm−1) 1759, 1670, 1497, 1453, 1440, and 1132. MS (ES) m/e 393 (M+1).
