Pyrrolidine, also known as tetrahydropyrrole, is a saturated five-membered heterocyclic ring, which is miscible with water. Pyrrolidine exists in many alkaloids and drug molecules, such as kappa opioids, antagonists of dopamine D4 receptors, and HIV reverse transcriptase inhibitors.
Cinnoline is a heterocyclic binuclear base containing two vicinal nitrogen atoms. Over the past two centuries, fused N-heterocyclic compounds have been widely used as valuable entities for expanding pharmacologically important reagents and have been recognized as an advantageous scaffold. Among the numerous fused N-heterocyclic compounds, cinnoline, quinoxaline, and quinazoline are important pharmacological agents, and a great deal of research has been done on this class of compounds. In medicinal chemistry, these N-heterocyclic compounds have a wide range of biological properties and can be used as synthetic intermediates, potential drug candidates and chemical probes.