An oxazolidine is a five-membered ring compound consisting of three carbons, a nitrogen, and an oxygen. The oxygen and NH are the 1 and 3 positions, respectively. In oxazolidine derivatives, there is always a carbon between the oxygen and the nitrogen (or it would be an isoxazolidine). All of the carbons in oxazolidines are reduced (compare to oxazole and oxazoline). Some of their derivatives, the oxazolidinediones, are used as anticonvulsants.