Carbohydrate Receptors and Sensors

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Two related topics will be studied: (1) Carbohydrate molecular recognition in lipophilic and hydrophilic solvents and (2) Multifunctional catalysis in phosphatediester hydrolysis. In the first topic, molecules will be investigated where two intramolecular hydrogen bonds are both retained and broken in complexation to a receptor with two hydrogen bonds. Multiple energetic analyses will be used to probe the strength of intra- and inter-molecular hydrogen bonds. Bis-boronic acid molecular hosts that are complementary to pyranoses will be prepared that incorporate a redox metal ion that will change coordination on complexing glucose. The difference in redox potential of the metal ion, with different coordination spheres, will be the basis of an electrochemical sensor for glucose in aqueous medium. In the second topic, bifunctional catalysis by two guanidinium groups in stabilization of the transition state of phosphatediester hydrolysis will be studied. Trifunctional catalysis with a general base and tetrafunctional catalysis with an added metal ion will be studied in the guanidinium system. A method for predicting enzyme rate enhancements based on binding constants and transition state analogs will be applied to the proposed multi-functional catalysis. %%% This grant from the Organic Dynamics Program supports the work of Professor Eric V. Anslyn at the University of Texas, Austin. Two topics will be pursed: (1) Complexation of carbohydrates and (2) Multifunctional catalysis of phosphatediesters, which are important in biological systems. In the first project, molecules that complex carbohydrates such as glucose in both water and organic solvents will be prepared. The structures of these complexes and their stabilities will be determined. A metal ion, such as an iron, will be incorporated into the receptor, which will be probed electrochemically to determine if glucose is complexed. This will lead to a practical application for the detection of glucose in aqueous solutions. In the second topic, a molecule will be prepared that uses two organic groups as catalytic centers for phosphatediester hydrolysis. This system will be expanded stepwise to include a basic functional group, and a metal ion. It is anticipated that this synthetic system will mimic an enzyme.