The synthesis of a new heterocyclic ring system is reported. The condensation of 9,10-dihydro-9-oxo-4-acridine carboxamide (7) with diethoxymethyl acetate gave pyrimido[5,6,1-d,e]acridine-3,7-dione (8). The amide 7 reacts with ethyl chloroformate to afford 2H-pyrimido[5,6,1-d,e]acridine-1,3,7-trione (9).