[CH3:1][CH:2]1[NH:7][C:6](=[O:8])[CH2:5][N:4]([C:9]([O:11][C:12]([CH3:15])([CH3:14])[CH3:13])=[O:10])[CH2:3]1.[H-].[Na+].C1(P(C2C=CC=CC=2)(O[NH2:27])=O)C=CC=CC=1>CN(C=O)C>[NH2:27][N:7]1[C:6](=[O:8])[CH2:5][N:4]([C:9]([O:11][C:12]([CH3:14])([CH3:13])[CH3:15])=[O:10])[CH2:3][CH:2]1[CH3:1]tert-Butyl 3-methyl-5-oxo-1-piperazinecarboxylate (1.1 g) was dissolved in DMF (20 ml) and treated with sodium hydride (0.25 g, in oil) with cooling on ice. After stirring at 50° C. for 1 hour, O-diphenylphosphinyl hydroxylamine (1.3 g) was added and the mixture was stirred at 50° C. for 15 hours. The reaction mixture was concentrated under reduced pressure, and the residue was combined with aqueous sodium bicarbonate and extracted with dichloromethane. The extract was dried and concentrated to obtain tert-butyl 4-amino-3-methyl-5-oxo-1-piperazinecarboxylate as a yellow oil.
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