4-(4-Amino-2-butyl-1H-imidazo[4,5-c][1,5]naphthyridin-1-yl)butaneamine (0.050 g, 0.16 mmol) was suspended in tetrahydrofuran (30 mL). N,N-diisopropylethylamine (28 μL, 0.16 mmol) was added to the suspension and then nicotinoyl chloride hydrochloride (0.028 g, 0.16 mmol) was added. The reaction mixture was stirred at ambient temperature for 1 hour by which time a solution was obtained. Thin layer chromatography (9:1 dichloromethane:methanol) showed one major new spot with a higher Rf and only a trace of starting material. Aminomethyl resin (100 mg) was added and the reaction mixture was stirred for 5 minutes. The solvent was removed under vacuum. The residue was dissolved in dichloromethane and placed on a layer of silica gel. The silica gel was eluted first with dichloromethane and then with 9:1 dichloromethane:methanol. The cleanest fractions were combined and then concentrated under vacuum to provide N3-[4-(4-amino-2-butyl-1H-imidazo[4,5-c][1,5]naphthyridin-1-yl)butyl]nicotinamide as a white powder. 1H NMR (300 MHz, CDCl3) δ 8.91 (m, 1H), 8.68 (d, J=4.5 Hz, 1H), 8.45 (d, J=4.3 Hz, 1H), 8.03 (m, 2H), 7.30-7.40 (m, 2H), 6.98 (s, 2H), 5.51 (s, 1H), 4.86 (apparent t, J=2H), 3.66 (q, J=6.5 Hz, 2H), 2.92 (apparent t, J=7.7 Hz, 2H), 2.05 (m, 2H), 1.75-1.95 (m, 4H), 1.51 (m, 2H), 1.00 (t, J=7.3 Hz, 3H); HRMS (EI) calcd for C23H27N7O (m+) 417.2277, found 417.2276.
