Beta-Alanine → 3-[(1-Cyclohexylmethyl-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-5-hydroxy-2-oxo-3-phenyl-1,2-dihydro-[1,7]naphthyridine-6-carboxylic acid methyl ester (35 mg, 0.089 mmol), β-alanine (795 mg, 8.9 mmol) and NaOMe solution (13 mL, 6.7 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 with vigorous stirring until pH was about 2. The organic layer was dried over MgSO4 and concentrated. The crude product was dissolved in saturated NaHCO3 and washed several times with ether. The aqueous layer was acidified to pH about 2 with 6 M HCl, and the resulting precipitate was isolated by filtration to give 25 mg of the title compound as a light yellow solid. MS: (+) m/z 450.30 (M+1).

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