O[CH2:2][CH2:3][C@@H:4]([CH3:14])[C:5]([NH:7][C:8]1[CH:12]=[CH:11][N:10]([CH3:13])[N:9]=1)=[O:6].C(P(CCCC)CCCC)CCC.C1(C)C=CC=CC=1.N(C(OCC)=O)=NC(OCC)=O>C1COCC1.C(OCC)(=O)C>[CH3:14][C@@H:4]1[CH2:3][CH2:2][N:7]([C:8]2[CH:12]=[CH:11][N:10]([CH3:13])[N:9]=2)[C:5]1=[O:6]To a solution of (2R)-4-hydroxy-2-methyl-N-(1-methyl-1H-pyrazol-3-yl)butanamide (216 mg) and tri-n-butylphosphine (0.54 mL) in THF (10 mL) was added 40% diethyl azodicarboxylate toluene solution (1.0 mL). The reaction mixture was stirred at room temperature for 15 hr, and diluted with ethyl acetate. The diluted solution was washed with saturated brine, and dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography (ethyl acetate/hexane), and then HPLC (C18, mobile phase: water/acetonitrile (containing 0.1% TFA)), and to the obtained fraction was added ethyl acetate. The mixture was washed with saturated aqueous sodium carbonate solution and saturated brine, and dried over anhydrous sodium sulfate, and the solvent was concentrated under reduced pressure to give the title compound (97 mg).
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