7-Ethyl-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-(1H,3H)-dione

1,3,6,7-tetramethylpyrido[2,3-d]pyrimidine-2,4-dione

1,3,7-trimethylpyrido[2,3-d]pyrimidine-2,4-dione

5-Cyano-6-cyanomethyl-5,6-dihydrouracil

7-amino-1,3-dimethylpyrido[2,3-d]pyrimidine-2,4-dione