[CH2:1]([N:8]1[C:12](=[O:13])[CH:11]([CH3:14])[CH:10](C(O)=O)[CH2:9]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C1(P(N=[N+]=[N-])(C2C=CC=CC=2)=[O:25])C=CC=CC=1.C([N:37]([CH2:40]C)CC)C.[C:42]([OH:46])([CH3:45])([CH3:44])[CH3:43]>>[CH2:1]([N:8]1[CH2:9][C@H:10]([NH:37][C:40]([O:46][C:42]([CH3:45])([CH3:44])[CH3:43])=[O:25])[C@H:11]([CH3:14])[C:12]1=[O:13])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1Compound (43) (3.40 g), 4.45 g of diphenylphosphorylazide, 1.9 g of triethylamine, and 50 ml of t-butyl alcohol were mixed and the mixture was heated under reflux for 12 hours. The reaction mixture was concentrated under reduced pressure, and the residue was dissolved in chloroform. The solution was washed successively with a 10% citric acid aqueous solution, a 2% sodium hydroxide aqueous solution, and water and dried over anhydrous sodium sulfate. The solvent was evaporated, and the residue was purified by silica gel column chromatography using chloroform-methanol (97.5:2.5 by volume) as an eluent to obtain 1.76 g of (±)-cis-1-benzyl-4-t-butoxycarbonylamino-3-methyl-2-oxopyrrolidine (44) as a colorless oil.
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