Selective functionalization and preorganization of calix[8]arenes

Due to the large dimension of their annulus, calix[8]arenes are promising substrates for the synthesis of molecular receptors for medium-sized organic compounds. To this end, their selective functionalization and conformational preorganization are of central interest. Examples of selectively derivatized calix[8]arenes or examples with reduced conformational mobility are reviewed. Partial O-alkylation is usually obtained in the presence of a weak base, which drives the reaction throughthe ''alternate alkylation'' route. Inhibition of conformational interconversion is achieved by simple intramolecular bridging, while a complete preorganization requires a multiple anchoring and a concomitant reduction of the tendency to self-fill the cavity.