Piperazine is an organic compound consisting of a six-membered ring containing two nitrogen atoms in opposite positions in the ring. The chemical formula of piperazine is C4H10N2, and it is an important pharmaceutical intermediate. Pyrimidines and piperazines are known to be the backbone of many bulk compounds and important core structures for approved drugs; studies have shown that combining a pyridine ring with a piperazine moiety within a single structural framework enhances biological activity.
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.
When the ends of the chains are joined together into a ring, cyclic compounds result; such substances often are referred to as carbocyclic or alicyclic compounds. Substitution of one or more of the ring carbon atoms in the molecules of a carbocyclic compound with a heteroatom gives a heterocyclic compound.