33070-58-5 Ppo-54g5 Pyrimido(5,4-g)pteridine-2,4,6,8(1H,3H,7H,9H)-tetrone, 1,3,7,9-tetrabutyl-, 5-oxide Pyrimido(5,4-g)pteridinetetrone 5-oxide, 1,3,7,9-tetrabutyl