[OH-].[Na+].S(O)(O)(=O)=O.[C:8]([N:11]1[CH2:16][CH2:15][N:14]([CH2:17][C:18]2[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=2)[CH2:13][CH2:12]1)(=[NH:10])[NH2:9].CO[CH:26]=[C:27]([C:32]([CH3:34])=O)[C:28]([O:30][CH3:31])=[O:29]>CO>[CH2:17]([N:14]1[CH2:15][CH2:16][N:11]([C:8]2[N:9]=[C:32]([CH3:34])[C:27]([C:28]([O:30][CH3:31])=[O:29])=[CH:26][N:10]=2)[CH2:12][CH2:13]1)[C:18]1[CH:23]=[CH:22][CH:21]=[CH:20][CH:19]=1One hundred milliliters of a 1M solution of sodium hydroxide in methanol were added to a suspension (60 ml) of 26.8 g (0.1 mol) of 1-amidino-4-benzylpiperazine sulfate [which had been synthesized in accordance with the process disclosed in J. Am. Chem. Soc., 66, 263 (1944)] in methanol, followed by a dropwise addition of 15.8 g (0.1 mol) of methyl α-methoxymethyleneacetoacetate. After stirring the resultant mixture overnight at room temperature, the precipitated sodium sulfate was filtered off. After distilling off methanol, the residue was dissolved in 500 ml of ethyl acetate. The resultant solution was washed twice with 100 ml of water. The ethyl acetate layer was washed with saturated saline and then dried with anhydrous magnesium sulfate. Upon distilling off ethyl acetate, 28.7 g of the intended compound was obtained as an orange-colored oily substance (yield: 88%). When the oily substance was left over at room temperature subsequent to its distillation under a reduced pressure, it was crystallized.
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