[N+:1]([NH:4][C:5]([NH2:7])=[NH:6])([O-:3])=[O:2].[Na].[CH2:9]([CH:13]([C:19]([CH3:21])=O)[C:14](OCC)=[O:15])[CH:10]([CH3:12])[CH3:11]>CO>[CH2:9]([C:13]1[C:14](=[O:15])[NH:6][C:5]([NH:4][N+:1]([O-:3])=[O:2])=[N:7][C:19]=1[CH3:21])[CH:10]([CH3:12])[CH3:11]Nitroguanidine (53.1 g) was added to a solution of sodium (17.6 g) in methanol (500 ml). The mixture was heated under reflux for 45 minutes. Ethyl α-isobutylacetoacetate (95.0 g) was then added dropwise to the refluxing mixture over 30 minutes. Refluxing was continued for a further 61/2 hours. Most of the methanol was removed and the residue was dissolved in water. Unreacted β-keto-ester was removed by extraction with chloroform and the solution was acidified with concentrated hydrochloric acid. The separated solid was washed with water and dried, giving 5-isobutyl-6-methyl-2-nitraminopyrimid-4(3H)-one (formula IV, R1 = CH3, R = isobutyl) (73.2 g). A sample recrystallised from ethanol had a melting point of 179°-181° (decomp.).
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