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.
Indolizine is a heterocyclic compound and an isomer of indole. Indolizine derivatives are widely used in natural products and synthetic drugs. Indolizine has various pharmacological activities, such as anti-tuberculosis, anti-cancer, anti-fungal, anti-bacterial, antioxidant and anti-inflammatory.