Oxygen heterocycles are one of the most common heterocycles in drugs and natural products. Oxetanes are highly polar and are also good acceptors of hydrogen bonds, which contribute to the metabolism and chemical stability of their host molecules. When substituted for commonly used functional groups such as gem dimethyl or carbonyl, oxetane units can induce profound changes in water solubility, lipophilicity, metabolic stability, and conformational preference. Four of the FDA-approved drugs contain oxetanes: Orlistat (orlistat), Paclitaxel (paclitaxel), and two of its derivatives, Docetaxel (docetaxel) and Cabazitaxel (cabazitaxel). Currently, oxetane-containing building blocks are flourishing in the fields of medicinal chemistry and drug discovery.