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.
1,2-Benzoisoxazole is an aromatic organic compound with the molecular formula C7H5NO containing a benzene-fused isoxazole ring structure. The compound itself has no general application; however, functionalized benzoxazoles and benzoisoxazoles have a variety of uses, including therapeutic drugs such as some antipsychotics (including risperidone, paliperidone, cape ketone and iloperidone) and the anticonvulsant azolamide.