Pyrimidine, also known as 1,3-diazobenzene, is a heterocyclic compound with the chemical formula C4H4N2. Pyrimidine is formed by substituting 2 nitrogen atoms for 2 carbons in the meta-position of benzene. It is a diazine and retains its aromaticity. Derivatives of pyrimidine widely exist in organic macromolecular nucleic acids, and many drugs also contain pyrimidine rings. In nucleic acids, three nucleobases are pyrimidine derivatives: cytosine, thymine and uracil. There are a variety of pyrimidine-containing drugs on the market, most of which are kinase inhibitors.
Thienopyridines are similar in structure to quinoline and isoquinoline, and are a class of heterocyclic compounds with important physiological activity and medicinal value. Thienopyridines are a subclass of antiplatelet drugs that prevent platelet aggregation by binding to selected extracellular cysteine residues on the P2Y12 receptor located on the platelet membrane.