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.
Compared to quinolines, isoquinolines are also prominent structural motifs present in many biologically significant natural and synthetic compounds. Some well-known isoquinoline alkaloids include the anticancer and anticonvulsant berberine, the vasodilator and antispasmodic drugs papaverine and emetine. In addition to naturally occurring isoquinolines, synthetic analogs have also shown significant biological activity.
Quinolines are an important class of biologically active heterocyclic compounds, and their derivatives usually exhibit a variety of biological activities. They can be used as antimalarial drugs and in the preparation of other antimalarial drugs. Other important activities of quinoline derivatives include inhibitory activity against EGFR-TK and antipsychotic activity. Futhermore, quinoline scaffolds are present in various drug molecules, including the antimalarial drugs aablaquine, chloroquine, mefloquine and primaquine, and the antibacterial agents gatifloxacin, levofloxacin, and moxifloxacin.