Convergent Strategies for Synthetic Receptors

Abstract

Combination of medium-sized building blocks such as calix[4]- or resorcinarenes comprises a new strategy for the synthesis of receptor molecules with unique complexation properties. Calix[4]arenes bridged at the lower rim with a polyglycol chain show very high association constants for K+ (8.9 x 109 M-1 in CDCl3). Kinetically stable Rb+-complexes (half-life time in CDCl3 of 180 days) can be prepared with calix[4]arenes bridged at the lower rim with a m-terphenyl moiety. The combination of calix[4]arenes with a uranyl containing salophen unit is used for the synthesis of lipophilic carriers for selective transport of urea through supported liquid membranes. Connecting the salophen unit via the upper rim of a calix[4]arene carrying four ester groups at the lower rim a ditopic receptor able to selectively complex NaH2P04 is synthesized. Calix[4]arenes can also be incorporated in carcerands via combination with resorcinol-based cavitands. Inclusion of dissymmetrical solvent molecules introduces a new type of diastereoisomerism with potential application in the preparation of molecular switches. The combination of calix[4]arenes with resorcinol-based cavitands is also used in the synthesis of the first holand, a molecule with a rigid organized cavity of nanosize dimensions.