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.
Indolinone derivatives have in common the presence of a hydrogen bond between the C-2 carbonyl and a hydrogen donor in a side chain, generally a pyrrole ring. Indolinone displays very promising antitumor properties by inhibiting various kinase families.