Added to an ethanol solution of sodium ethoxide, which had been prepared from 0.57 g (24.8 mmol) of sodium and 30 ml of EtOH, was 6.61 g (24.7 mmol) of 1-amidino-4-benzylpiperazine sulfate, followed by a dropwise addition of an ethanol solution (10 ml) of 5.0 g (24.7 mmol) of ethyl 2-formylsuccinate [the compound described in Ann. 363, 340] over 15 minutes. The resultant mixture was then refluxed for 4.5 hours. After cooling the reaction mixture, crystals were collected by filtration and then washed with water to obtain 3.65 g of the above-identified compound (yield: 41%).
