To a solution of (3-ethylbenzofuran-2-yl)-N-methylmethanamine (89 mg, 0.49 mmol) in DMF (5 mL) were added in sequential order (E)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylic acid (111 mg, 0.44 mmol), 1-hydroxybenzotriazole (68 mg, 0.49 mmol), diisopropylethylamine (232 uL, 1.34 mmol), and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (98 mg, 0.49 mmol). The mixture was stirred at room temperature overnight, cooled in an ice bath and water added with rapid stirring. The product precipitated and was filtered, triturated with ether and dried to yield title compound as a pale brown solid (134 mg, 70%): 1H NMR (300 MHz, DMSO-d6) δ 10.67 (s, 1H), 8.37 (s, 1H), 8.09 (s, 1H), 7.96 (s, 1H), 7.18-7.64 (m, 5H), 4.81-5.01 (rotamers, 2s, 2H), 3.27-3.61 (m, 2H), 2.90 (d, J=9.0 Hz, 2H), 2.73-2.78 (m, 2H), 2.51-2.59 (m, 3H), 1.23 (t, J=9.0 Hz, 3H); MS (ESI) m/e 390 (C23H23N3O3+H)+.
