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.
Amino acids are organic compounds containing a basic amino group and an acidic carboxyl group. Because amino acids contain both amino and carboxyl groups, they can be polymerized in an end-to-end manner, removing a molecule of water to form a covalent amide bond or peptide bond. Many amino acids are linked together end to end to form a polypeptide. Amino acids and peptides are important components in the fields of medicine and life sciences.