A 16 mL vial flask was successively charged with (2E)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylic acid hydrochloride (30 mg, 0.12 mmol), DMF (3 mL), 2-(5-methyl-1,2,4-oxadiazol-3-yl)piperidine hydrochloride (29 mg, 0.14 mmol; which may be prepared as described in Step 3), DIPEA (48 μL, 0.28 mmol) and EDAC (27 mg, 0.14 mmol). The reaction mixture was stirred at room temperature overnight and concentrated to dryness. The residue was purified on preparative TLC (eluent: dichloromethane/NH3 7N in MeOH, 2.5%) to give an oil. This oil was taken up in acetone, diethyl ether and concentrated. The resulting wax was finally dissolved in dichloromethane, concentrated and dried to give the title compound (15 mg, 34%) as a yellow solid.
