[NH2:1][C@:2]([CH3:14])([CH2:5][CH2:6][C:7]1[N:8]([CH2:12][CH3:13])[CH:9]=[CH:10][CH:11]=1)[CH2:3][OH:4].C(N([CH2:20][CH3:21])CC)C.[C:22](OC(=O)C)(=[O:24])[CH3:23].[OH2:29]>ClCCl.CN(C)C1C=CN=CC=1>[C:22]([O:4][CH2:3][C@@:2]([NH:1][C:20](=[O:29])[CH3:21])([CH3:14])[CH2:5][CH2:6][C:7]1[N:8]([CH2:12][CH3:13])[CH:9]=[CH:10][CH:11]=1)(=[O:24])[CH3:23]To a solution of (2R)-2-amino-2-methyl-4-(1-ethylpyrrol-2-yl)butan-1-ol 1/2 D-(−)tartrate (2.7 g, 7.80 mmol) obtained in Reference example (24a) in dichloromethane (30 ml) were added successively triethylamine (17.0 ml, 122 mmol), acetic anhydride (7.6 ml, 80.4 mmol) and 4-dimethylaminopyridine (20 mg, 0.16 mmol), and the resulting mixture was stirred at room temperature for 3.5 hours. After stirring, water was added to the reaction mixture, and the resulting mixture was extracted with dichloromethane. The extract was washed successively with water and saturated aqueous sodium chloride solution and dried over anhydrous sodium sulfate. After filtration, the solvent was removed in vacuo, and the residue was purified by chromatography on a silica gel column using ethyl acetate as the eluent to afford the title compound (2.2 g, yield: 96%).
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