CALIXARENES - FROM CHEMICAL CURIOSITY TO A RICH SOURCE FOR MOLECULAR RECEPTORS

Calixarenes, the macrocyclic compounds derived from the condensation o f p-substituted phenols and formaldehyde under basic conditions, have been widely used in the last ten years in Supramolecular Chemistry. Th eir huge success is due to several factors. They are readily accessibl e in large quantities, can be easily functionalized both at the phenol ic OH groups and at the aromatic nuclei, and, depending on the number of monomeric units (n) in the macrocyclic structure, they present diff erent size, shape and conformational properties. The regio- and stereo selective control in the fuctionalization of calix[4]- and calix[6]are nes here reported, provides the fundamental synthetic tools to model t he shape of these macrocycles and allows one to obtain receptors able to recognize cations, anions, and neutral molecules. The high preorgan ization and the high complementarity with the guests that can be achie ved with calixarene-based hosts make these macrocycles a rich source f or molecular receptors.