To a solution of (3-ethylbenzofuran-2-yl)-N-methylmethanamine (115 mg, 0.6 mmol) in DMF (5 mL) were added in sequential order (E)-3-(3-oxo-3,4-dihydro-2H-pyrido[3,2-b][1,4]oxazin-7-yl)acrylic acid (140 mg, 0.54 mmol), 1-hydroxybenzotriazole (84 mg, 0.6 mmol), diisopropylethylamine (282 uL, 1.62 mmol), and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (120 mg, 0.6 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 the title compound as a white solid (113 mg, 52%): 1H NMR (400 MHz, DMSO-d6) δ 11.41 (s, 1H), 8.19 (s, 1H), 7.88 (d, J=6.4 Hz, 1H), 7.66 (d, J=7.6 Hz, 1H), 7.51-7.49 (m, 2H), 7.29-7.25 (m, 3H), 4.99-4.79 (rotamers, 2s, 2H), 4.68 (s, 2H), 3.39 (s, 3H), 2.79-2.73 (m, 2H), 1.23-1.20 (m, 3H); MS (ESI) m/e 392 (C22H21N3O4+H)+.
