Beta-Alanine → 3-{[1-Cyclohexylmethyl-8-(2-ethoxy-pyrimidin-5-yl)-5-hydroxy-2-oxo-3-phenyl-1,2-dihydro-[1,7]naphthyridine-6-carbonyl]-amino}-propionic acid

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A mixture of 1-cyclohexylmethyl-8-(2-ethoxy-pyrimidin-5-yl)-5-hydroxy-2-oxo-3-phenyl-1,2-dihydro-[1,7]naphthyridine-6-carboxylic acid methyl ester (35 mg, 0.068 mmol), β-alanine (607 mg, 6.8 mmol) and NaOMe solution (11 mL, 5.4 mmol, 0.5 M in MeOH) was refluxed for 16 h. After the mixture was cooled to r.t., the solvent was evaporated in vacuo. The residue was partitioned between EtOAc and water. 1 M HCl was added until pH was about 3-4. The aqueous layer was extracted with additional EtOAc, and the organic layers were combined, dried over MgSO4 and concentrated. The crude product was purified by silica gel chromatography (5-40% EtOAc/hexanes+1% AcOH). The product isolated was dissolved in saturated NaHCO3 and washed several times with ether. The aqueous layer was acidified to pH about 3-4, and the resulting precipitate was isolated by filtration to give 15 mg of the title compound. MS: (+) m/z 572.36 (M+1).

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