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.
Benzimidazole is a benzo derivative of imidazole. It is a kind of bicyclic aromatic organic compounds, which is formed by fusing a six-membered benzene ring and five-membered imidazole at positions 4 and 5 of imidazole ring. It is an important pharmacophore of many biologically active heterocyclic compounds with various pharmacological activities. Benzimidazoles and their derivatives have developed into dynamic heterocyclic systems due to their potency in a variety of biologically active compounds such as anticancer, bactericidal and antiviral drugs. Benzimidazoles are a class of therapeutic motifs with broad relevance in medicinal chemistry.