A mixture of 7-amino-4-(2-fluorophenyl)-9H-pyrido[3,4-b]indole-1-carboxamide (30.0 mg, 0.094 mmol), dihydro-2H-pyran-4(3H)-one (10.37 μL, 0.112 mmol), and sodium triacetoxyborohydride (39.7 mg, 0.187 mmol) in tetrahydrofuran (1 mL) and dichloromethane (1 mL) was stirred at rt for 16 hr. Additional dihydro-2H-pyran-4(3H)-one (10.37 μL, 0.112 mmol) and sodium triacetoxyborohydride (39.7 mg, 0.187 mmol) were added, and the mixture was stirred at room temperature for another 8 hr. To the reaction mixture was added water (2 mL), and the resulting mixture was stirred at room temperature for 20 min. It was diluted with ethyl acetate (50 mL), washed with saturated NaHCO3 solution (15 mL) and brine (15 mL), and dried over anhydrous MgSO4. Solvent was removed under vacuum, and the residue was subjected to prep. reverse phase HPLC purification. The correct fraction was concentrated under vacuum and basified with saturated NaHCO3 solution. The precipitating product (11.8 mg, 0.029 mmol, 30.8% yield) was collected as a yellow solid by suction filtration and dried at 50° C. under vacuum. LCMS (M+H)+=405.17. 1H NMR (500 MHz, DMSO-d6) δ: 11.30 (s, 1H), 8.23 (s, 1H), 8.11 (s, 1H), 7.70 (s, 1H), 7.65-7.61 (m, 2H), 7.49-7.42 (m, 2H), 6.98 (d, J=8.0 Hz, 1H), 6.94 (s, 1H), 6.46 (dd, J1=8.7 Hz, J2=1.5 Hz, 1H), 6.19 (br. s, 1H), 3.90 (m, 2H), 3.47 (m, 1H), 3.43 (m, 2H), 1.94 (m, 2H), 1.44 (m, 2H).
