A mixture of 1-benzyl-5-hydroxy-2-oxo-3-phenyl-8-pyridin-3-yl-1,2-dihydro-[1,7]naphthyridine-6-carboxylic acid (68 mg, 0.15 mmol) and HOBt (33 mg, 0.24 mmol) was dissolved in CH2Cl2 (3 mL). EDC (52 mg, 0.27 mmol) was added, and the resulting mixture was stirred for 10 min. (1-Amino-cyclopropyl)-acetic acid methyl ester HCl salt (40 mg, 0.24 mmol) and Hunig's base (0.1 mL, 0.55 mmol) were added, and the mixture was stirred for 16 h. The mixture was diluted with EtOAc and washed with 0.1 M HCl. The organic layer was dried over MgSO4 and concentrated. The crude product was purified by silica gel chromatography (5-90% EtOAc/hexanes+1% AcOH) to give 5 mg of the title compound as a yellow solid. MS: (+) m/z 561.34 (M+1).
