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tert-Butyl 7-(4-(benzyloxy)-2-oxopyridin-1(2H)-yl)-5-methyl-3,4-dihydro-1H-pyrido[4,3-b]indole-2(5H)-carboxylate (12.0 g, 24.7 mmol) was dissolved in MeOH (100 mL), and 2 N HCl in Et2O (300 mL) was added. The reaction was allowed to proceed for 18 h. The mixture was concentrated, and the residue was partitioned between CH2Cl2 and sat. Na2CO3 solution. The organic phase was removed, and the aqueous phase was back extracted with CH2Cl2. The combined organic extracts were dried over Na2SO4, filtered and concentrated to dryness providing the free base of the title compound (8.1 g, 85%) as a yellow solid. A portion of the free base was converted to the HCl salt for biological testing. Free base: 1H NMR (500 MHz, CDCl3) δ 7.47-7.34 (m, 6H), 7.32-7.28 (m, 2H), 6.98 (d, J=7.1 Hz, 1H), 6.07 (d, J=2.6 Hz, 1H), 6.04 (dd, J=7.5, 2.6 Hz, 1H), 5.05 (s, 2H), 4.15 (s, 2H), 3.61 (s, 3H), 3.34 (br s, 2H), 2.78 (br s, 2H). HCl salt: melting point (mp) 296-302° C.; 1H NMR (500 MHz, CD3OD) δ 7.61-7.57 (2×d, 2H), 7.47-7.46 (m, 3H), 7.43-7.40 (m, 2H), 7.37-7.34 (m, 1H), 7.05 (dd, J=8.3, 1.7 Hz, 1H), 6.33 (dd, J=7.5, 2.7 Hz, 1H), 6.16 (d, J=2.6 Hz, 1H), 5.19 (s, 2H), 4.57 (s, 2H), 3.73 (s, 3H), 3.67 (t, J=6.2 Hz, 2H), 3.20 (t, J=6.1 Hz, 2H); ESI MS m/z 386 [M+H]+; HPLC (Method A) 95.7% (AUC), tR=13.6 min.
