1,3,6,7-Tetramethylpyrimido(4,5-d)pyrimidine-2,4,5(1H,3H,6H)-trione 64467-27-2 BRN 1140741 Pyrimido(4,5-d)pyrimidine-2,4,5(1H,3H,6H)-trione, 1,3,6,7-tetramethyl-