Resorcarenes: Emerging Class of Macrocyclic Receptors

The present review intends to give an overview on the synthetic methods applied for the preparation of resorcarenes and all the conformation implications due to the flexibility of the target tetramers. The flexible resorcarenes can be rigidified by intramolecular bridging of adjacent oxygens with bifunctional reagents, to give cavitands. These compounds, which feature rigid bowl shaped cavities of different size and dimensions, depending on the bridging groups employed, will be examined according to these latter. Moreover, some emphasis will be placed in resorcarenes chirality and on the ways how to introduce it: either indirectly, e.g. by tetramerization of monomers containing a chiral center, or directly, by synthesis of macrocycles featuring a Cn-type symmetry, which is defined as inherent chirality and arises from the nonplanarity of the basic metacyclophane system. Finally, the use of resorcarenes as pseudo stationary phases for the separation of isomeric compounds will be mentioned.