[NH2:1]N.C[N:4](/[CH:6]=[C:7]1/[CH2:8][N:9]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:10][C:11]/1=O)C>C(O)C>[NH:1]1[C:11]2[CH2:10][N:9]([C:13]([O:15][C:16]([CH3:19])([CH3:18])[CH3:17])=[O:14])[CH2:8][C:7]=2[CH:6]=[N:4]1A solution of hydrazine (3 mL) and tert-butyl (3Z)-3-[(dimethylamino)methylene]-4-oxopyrrolidine-1-carboxylate (19.22 g) in ethanol (40 mL) was heated at 85° C. in a sealed tube for 4 h. Solvent was removed under reduced pressure, and the residue was triturated with dichloromethane (160 mL) and ethyl acetate (15 mL). The resulting solid was filtered. The filtrate was concentrated and the resulting solid was triturated again. The combined solids were used in the next step.
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