Isoxazole is a liquid heterocyclic compound C3H3NO isomeric with oxazole and having a penetrating odor like that of pyridine. Isoxazoles belong to an important class of five-membered aromatic heterocycles containing two electronegative heteroatoms, nitrogen and oxygen, in a 1,2-relationship and three regular sp2 carbon atoms. These molecules are found to be key components in various synthetic products in daily use and also present as a pharmacophore essential for biological activity in many drugs and bioactive natural products. In addition, isoxazoles have demonstrated their ability to exhibit hydrogen bond donor/acceptor interactions with a variety of enzymes and receptors.
Nitrogen-containing heterocyclic compounds have a wide range of applications in medicine, organic materials, natural products and other fields, mainly for biologically active molecules. Pyrrolopyrazines contain pyrrole and pyrazine rings as bioactive scaffolds. Compounds containing this scaffold have a wide range of biological activities, such as antibacterial, anti-inflammatory, antiviral, antifungal, antioxidant, antitumor, and kinase inhibition.