Cl.[NH2:2][CH:3]([CH2:8][C:9]1[CH:14]=[CH:13][C:12]([Cl:15])=[CH:11][CH:10]=1)[C:4]([O:6][CH3:7])=[O:5].N1C=CC=CC=1.Cl[C:23]([O:25][CH2:26][CH3:27])=[O:24]>C(Cl)Cl.C(OCC)(=O)C.O>[Cl:15][C:12]1[CH:11]=[CH:10][C:9]([CH2:8][CH:3]([NH:2][C:23]([O:25][CH2:26][CH3:27])=[O:24])[C:4]([O:6][CH3:7])=[O:5])=[CH:14][CH:13]=1
While under nitrogen, a stirred mixture of methyl 2-amino-3-(4-chlorophenyl)propanoate hydrochloride (3.13 g, 12.5 mmol) in methylene chloride (42 mL) was cooled in an ice-water bath and carefully treated with pyridine (2.23 mL, 27.5 mmol) and ethyl chloroformate (1.27 mL, 13.3 mmol). After stirring for 1 h, the solution was diluted with ethyl acetate (50 mL) and water (50 mL), and the layers were separated. The aqueous phase was re-extracted with ethyl acetate (2×25 mL), and the combined organic phase was washed with saturated aqueous sodium chloride (25 mL), dried over Na2SO4 and concentrated under reduced pressure to give methyl 3-(4-chlorophenyl)-2-(ethoxycarbonylamino)propanoate (3.56 g, 99%) as a white solid. 1H NMR (CDCl3, 400 MHz) δ 7.28 (m, 2 H), 7.08 (m, 2 H), 5.12 (m, 1 H), 4.65 (m, 1 H), 4.13 (q, J=8 Hz, 2 H), 3.74 (s, 3 H), 3.10 (qd, J=16, 4.0 Hz, 2 H), 1.25 (t, J=8 Hz, 3 H). LC-MS gives ESI+ MS found for C13H16ClNO4 m/z 308.0 (M+Na), 286.0 (M+H).
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