C([NH:7][C:8]1[CH:13]=[CH:12][C:11]([Cl:14])=[CH:10][C:9]=1[C:15](=[O:33])[CH2:16][C@H:17]1[C:21](=[O:22])[O:20]C[N:18]1C(OCC1C=CC=CC=1)=O)(=O)C(C)(C)C.Cl.O>CC(O)=O>[NH2:18][C@@H:17]([CH2:16][C:15]([C:9]1[CH:10]=[C:11]([Cl:14])[CH:12]=[CH:13][C:8]=1[NH2:7])=[O:33])[C:21]([OH:22])=[O:20]A stirred mixture of (S)-(+)-N-pivaloyl-2-[1-oxo-2-[3-(benzyloxycarbonyl)-5-oxo-oxazolidin-4-yl]ethyl]-4-chloro aniline (1.06 g, 2.24 mmol), 37% HCl (20 ml), H2O (20 ml) and CH3COOH (28 ml), was heated at 70° C. for 5.5 h. The solution was evaporated to dryness. The residue was dissolved in water (30 ml), washed with CH2Cl2 and evaporated again. The crude product was purified by flash chromatography on silica gel (chloroform: methanol:30% NH4OH=140:60:6) to yield (S)-(-)-2-amino-4-(2-amino-5-chlorophenyl)-4-oxo butyric acid as yellow crystal (0.29 g; 51.5%; m.p. 206°-208° C.; [α]20D =-12.0° (1%; CH3OOH); ee 96%.
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