[Cl:1][C:2]1[C:3]([C:9](=O)[C@@H:10]([NH:12][C:13](=[O:19])[O:14][C:15]([CH3:18])([CH3:17])[CH3:16])[CH3:11])=[N:4][CH:5]=[C:6]([Cl:8])[CH:7]=1.Cl.[NH2:22][OH:23].N1C=CC=CC=1>C(O)C>[Cl:1][C:2]1[C:3]([C:9](=[N:22][OH:23])[C@@H:10]([NH:12][C:13](=[O:19])[O:14][C:15]([CH3:18])([CH3:17])[CH3:16])[CH3:11])=[N:4][CH:5]=[C:6]([Cl:8])[CH:7]=1To a solution of 1.0 g of tert-butyl (S)—N-[2-(3,5-dichloropyridin-2-yl)-1-methyl-2-oxoethyl]carbamate and 239 mg of hydroxylamine hydrochloride in 5 ml of ethanol, 272 mg of pyridine was added, and the mixture was stirred at room temperature for 18 hours. After completion of the reaction, the solvent was evaporated under reduced pressure, the resulting residue was mixed with 10 ml of water and extracted with ethyl acetate (10 ml×2), the resulting organic layers were combined, dried over saturated aqueous sodium chloride and then anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The resulting residue was purified by silica gel column chromatography using ethyl acetate-hexane (with a gradient of from 5:95 to 40:60) as the eluent to obtain 740 mg of the desired product as pale yellow crystals.
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