1,3,7,9-tetramethylpyrimido[5,4-g]pteridine-2,4,6,8-tetrone

1,1',3,3'-tetramethylhydurilic acid

1,3-dimethyl-9-propyl-8-sulfanylidene-7H-purine-2,6-dione

2-[(4-amino-1,3-dimethyl-2,6-dioxopyrimidin-5-yl)amino]acetonitrile

1,3-dimethyl-6,7-diphenylpteridine-2,4-dione