D-Phenylalanine → (R)-2-[(7-Benzyl-1-cyano-4-hydroxy-8-oxo-7,8-dihydro-[2,7]naphthyridine-3-carbonyl)-amino]-3-phenyl-propionic acid

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Reaction Steps

A mixture of 7-benzyl-1-cyano-4-hydroxy-8-oxo-7,8-dihydro-[2,7]naphthyridine-3-carboxylic acid methyl ester (30 mg, 0.090 mmol), D-phenylalanine (296 mg, 1.8 mmol) and NaOMe (73 mg, 1.3 mmol) in 2-methoxyethanol (10 mL) was refluxed for 3 h. After the mixture was cooled to r.t., solvent was evaporated in vacuo. The residue was partitioned between EtOAc and water. 1 M HCl was added with vigorous stilling until pH was about 2. The organic layer was dried over MgSO4 and concentrated. The residue was chromatographed (5-60% EtOAc/hexanes+2% AcOH) to give a crude solid. The solid was dissolved in saturated NaHCO3 and washed with ether. 1 M HCl was added to the aqueous layer until pH was about 1, and the resulting precipitate was isolated by filtration to give 21 mg of the title compound as an off-white solid. MS: (+) m/z 469.02 (M+1).

Provenance & Evidence