C([NH:4][CH:5]([CH2:9][C:10]([C:12]1[CH:17]=[C:16]([Cl:18])[CH:15]=[CH:14][C:13]=1[NH2:19])=[O:11])[C:6]([OH:8])=[O:7])(=O)C>Cl>[NH2:4][C@H:5]([CH2:9][C:10]([C:12]1[CH:17]=[C:16]([Cl:18])[CH:15]=[CH:14][C:13]=1[NH2:19])=[O:11])[C:6]([OH:8])=[O:7]A solution of (-)-2-acetamido-4-(2-amino-5-chlorophenyl)-4-oxo-butyric acid (0.76 g, 2.67 mmol) in 2N HCl (90 ml) was heated at reflux temperature for 3 h. The aqueous solution was evaporated to dryness, the residue was dissolved in water, washed with CH2Cl2 and evaporated again. The residue was dissolved in water (30 ml) and adjusted to pH 6.5 with 1N NaOH: a light yellow solid separated. The solid was filtered and washed with cold water to obtain (R)-(+)-2-amino-4-(2-amino-5-chlorophenyl)-4-oxo-butyric acid (0.40 g; 59.7%; m.p. 210°-211° C. (dec.); [α]20D =+11.5 (1%, CH3COOH); ee=96%).
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