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.
Benzoxazole is an aromatic organic compound with a molecular formula of C7H5NO, a benzoxazole ring structure, and an odor similar to pyridine. Although benzoxazole itself has little practical value, many benzoxazole derivatives are commercially important. As heterocyclic compounds, benzoxazoles are used in research as starting materials for the synthesis of larger, often biologically active structures. Its aromaticity makes it relatively stable, although as a heterocycle it has an active site that enables it to be functionalized.