[CH2:1]([O:8][C:9](=[O:17])[NH:10][C:11]1([C:14](=[O:16])[NH2:15])[CH2:13][CH2:12]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.CO[CH:20](OC)[N:21]([CH3:23])[CH3:22]>>[CH2:1]([O:8][C:9](=[O:17])[NH:10][C:11]1([C:14](=[O:16])/[N:15]=[CH:20]/[N:21]([CH3:23])[CH3:22])[CH2:12][CH2:13]1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1To a round bottom flask was added (1-carbamoyl-cyclopropyl)-carbamic acid benzyl ester (935 mg, 4 mmol) in N,N-dimethylformamide dimethyl acetal (15 mL). The reaction mixture was stirred at 100° C. for 1 h. The solvent was concentrated in vacuo. The residue was dissolved in EtOAc/sat. NaHCO3. The organic phase was separated, washed with brine, dried over anhydrous Na2SO4, filtered, concentrated and dried under high vacuum to afford 1.11 g of (1-{[1-dimethylamino-meth-(E)-ylidene]-carbamoyl}-cyclopropyl)-carbamic acid benzyl ester as a light brown oil, m/z 290.9 [M+1]+.
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