A mixture of 4-(3-(4-(dimethylamino)benzamido)-2-fluorophenyl)-7-morpholino-9H-pyrido[3,4-b]indole-1-carboxylic acid (105 mg, 0.190 mmol), ammonium chloride (40.6 mg, 0.759 mmol), N,N-diisopropylethylamine (0.159 mL, 0.910 mmol), BOP (109 mg, 0.247 mmol), N-methylmorpholine (0.081 mL, 0.740 mmol) in DMF (0.5 mL) was stirred at room temperature for 1.5 hr. The mixture was diluted with MeOH (4 mL), divided into three portions, and purified by reverse phase HPLC. The correct fractions were concentrated under vacuum and basified with saturated NaHCO3 solution to pH 10. The precipitating product (24.7 mg, 0.044 mmol, 23.09% yield) was collected as a yellow solid by suction filtration and dried at 50° C. under vacuum. LCMS (M+H)+=553.32. 1H NMR (500 z, DMSO-d6) δ: 11.52 (s, 1H), 9.86 (s, 1H), 8.31 (s, 1H), 8.20 (s, 1H), 7.90 (d, J=9.0 Hz, 2H), 7.84 (m, 1H), 7.76 (s, 1H), 7.45-7.40 (m, 2H), 7.32 (d, J=8.0 Hz, 1H), 7.29 (d, J=2.0 Hz, 1H), 6.86 (dd, J1=9.0 Hz, J2=2.0 Hz, 1H), 6.77 (d, J=9.0 Hz, 2H), 3.79-3.77 (m, 4H), 3.22-3.19 (m, 4H), 2.51 (m, 6H).
