A mixture of 9-[(cyclopentyl)methyl]-4-hydroxy-5-carbamoyl carbazole (45 mg, 0.146 mmol) and Cs2CO3 (120 mg; 0.365 mmol) in 2 mL of DMF was treated with methyl bromoacetate (0.018 mL; 0.19 mmol). The reaction was stirred for 2 hours at ambient temperature, then it was diluted with EtOAc and H2O (10 mL each). The aqueous layer was saturated with solid NaCl extracted with EtOAc (2×10 mL). The combined organic layers were washed with H2O (2×25 mL), dried over anhydrous Na2SO4, filtered and concentrated in vacuo. Purification of the crude residue by flash chromatography on silica gel (elution with a gradient of 0% to 100% EtOAc/hexanes) followed by trituration with Et2O/EtOAc afforded 26 mg (0.0683 mmol; 47%) of title compound as a tan solid. MS (ES) m/e 381 (M+1), 364 (M+H—NH3), 439 (M+AcO−).
