869891-41-8

936020-16-5

869891-41-8

b) General procedure for synthesizing methyl 4-methyl-2,6-dioxo-3H-pyrimidine-5-carboxylate: Methyl 3-amino-2-(ethoxycarbonylcarbamoyl)-but-2-enoate (0.71 g, 3.08 mmol) was reacted with triethylamine (30% aqueous solution, 0.56 mL) with stirring for 18 hours at 50 °C. Subsequently, another portion of triethylamine (30% aqueous solution, 0.14 mL) was added and the reaction mixture was continued to be stirred at 60 °C for 3 hours. Upon completion of the reaction, the solvent was removed by evaporation and then acidified with acetic acid (AcOH). The resulting solid product was collected by filtration and dried under vacuum to afford methyl 4-methyl-2,6-dioxo-3H-pyrimidine-5-carboxylate (0.33 g, 1.79 mmol, 58% yield), which could be used directly in the next reaction without further purification.