Stereo-selective synthesis of bis-bridged calixarenes
Staggs, Sara J.
In recent years, there has been a growing interest in the rational design of synthetic catalysts capable of achieving significant enhancement of reaction rates and stereo-selectivities. Ideally, a new catalyst would mimic highly efficient biological catalysts such as enzymes. In order to achieve this goal, the synthetic catalyst system would need to be constructed so to as complement the size, shape and charge of the specific substrate and/or metal ion that would be required in a particular reaction. This can be accomplished primarily through supramolecular interactions that involve hydrogen bonding, Van der Waals forces, electrostatic interactions, and ion-dipole to interact with the substrate and metal ion to form a complex. Calixarenes have certain structural features analogous to enzymes, which include a well-defined cavity for host-guest complex interactions, and potential for structural variation. Research conducted in the Blanda group has focused on the synthesis of new, rigid calixarenes that have the potential to function as enzyme mimics. The synthetic protocol generally calls for the rigidification of the calixarene via synthesis of a bis-bridged calixarene. The development of a stereo-selective synthetic strategy has allowed the synthesis of two distinct conformational isomers of the bis-bridged calixarene. Structural characterization of each isomer was derived by NMR spectroscopy and X-ray crystallography. During the NMR characterization the discovery of a 13C rule emerged which allowed for rapid and reliable structural assignment in solution.
Staggs, S. J. (2003). Stereo-selective synthesis of bis-bridged calixarenes (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.