The molecular structure of cyclobutane has four carbon atoms, and its four carbon atoms are not in the same plane, which is the folded conformation of cyclobutane. Cyclobutane itself is not of commercial or biological interest, but more complex derivatives are important in biology and biotechnology. Currently, nine FDA-approved drugs contain the cyclobutane structure. From the perspective of therapeutic areas, cyclobutyl drugs are mainly distributed in popular areas such as tumors, neurological diseases, infectious diseases, endocrine and metabolic diseases.
Cyclopropane is the smallest cyclic compound with unique structural features and physicochemical properties, which is widely used in the design of small molecule drugs. In drug design, it is often used to increase activity, fix conformation and improve PK and water solubility. The introduction of cyclopropyl groups into drugs can change various properties of molecules, such as improving metabolic stability; increasing biological activity; enhancing drug efficacy; limiting polypeptide conformation and slowing down its hydrolysis; reducing plasma clearance; improving drug dissociation and many more. Cyclopropane rings are widely found in marketed drugs, including cardiovascular drugs, central nervous system (CNS) drugs, anticancer drugs, autoimmune and anti-inflammatory drugs.