D-Alanine → (R)-2-[(1-Cyano-4-hydroxy-8-phenoxy-isoquinoline-3-carbonyl)-amino]-propionic acid

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A mixture of 1-cyano-4-hydroxy-8-phenoxy-isoquinoline-3-carboxylic acid methyl ester (95 mg, 0.30 mmole), D-Alanine (529 mg, 5.94 mmole) and 0.5 M sodium methoxide/methanol (11.3 mL) was refluxed for three days before it was cooled to room temperature and concentrated in vacuo. The residue was dissolved in water (25 mL) and extracted with dichloromethane (3×30 mL). The remaining aqueous layer was acidified to pH=3 with 1N HCl (8 mL). The white suspension was extracted with ethyl acetate (30 mL) and dichloromethane (30 mL). The combined organic layers were washed with brine, dried over MgSO4 and concentrated in vacuo to give the title compound as a white solid (90 mg): 1H NMR (DMSO-d6, 200 MHz): δ=13.52 (bs, 1H), 9.15 (br s, 1H), 8.30 (d, 1H), 8.10 (m, 1H), 7.67 (t, J=8 Hz, 1H), 7.42 (m, 2H), 7.17 (m, 3H), 4.83 (q, 1H), 1.68 (d, J=7.0 Hz, 3H)); MS: (+) m/z 378.29 (M+1).

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