1,3-二甲基-1H-吡咯并[3,2-d]嘧啶-2,4(3H,5H)-二酮

1,5,7-trimethylpyrazolo[3,4-d]pyrimidine-4,6-dione

5,7-dimethyl-1H-pyrazolo[3,4-d]pyrimidine-4,6-dione

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

1,3-dimethyl-6-phenylpyrrolo[3,2-d]pyrimidine-2,4(1H,3H)-dione