The title compound 6-(4-amino-1-methyl-2-(methylthio)-6-oxo-1,6-dihydro-pyrimidin-5-yl)-3,6-dimethyl-2-(methylthio)-6,7-dihydro-3H-pyrrolo[2,3-d]pyrimidine-4,5- dione was synthesized in 60% yield by a microwave-induced cyclocondensation reaction of aminopyrimidine with pyruvic acid in the presence of cerium ammonium nitrate (CAN) as catalyst.