Boronic acids, molecular receptors based

T.D. James, K.R.A.S. Sandanayake, S. Shinkai, Saccharide sensing with molecular receptors based on boronic acid , Angew. Chem, Int. Ed. EngL 1996, 35, 1910-1922. 

Boronic acids RB(OH)2, boronic esters RB(OR)2, and triorganoboranes R3B have been studied extensively for the selective recognition of anions. " Moreover, arylboronic acids have proven highly useful for sensing of saccharides based on the facile formation of esters with diols, thus providing an excellent alternative to more commonly employed synthetic molecular receptors based on hydrogenbonding interactions. Absorption and fluorescence spectroscopy, circular dichroism, and cyclic voltammetry have all been successfiilly used as detection methods for organoboron sensors. 

It should be noted that carbohydrate recognition through formation of boronates has been remarkably successful. However, it involves covalent bonds and cannot be seen as biomimetic. For reviews, see James, T. D., Sandanayake, K. R. A. S. and Shinkai, S. (1996) Saccharide sensing with molecular receptors based on boronic acid, Angew. Chem., Int. Ed. Engl. 35, 1911-1922 Smith, B. D. (1996) Liquid membrane transport using boronic acid carriers, Supramolecular Chemistry 7, 55-60. 

Membranes and Molecular Assemblies The Synkinetic Approach 6 Calixarenes Revisited 7 Self-assembly in Supramolecular Systems 8 Anion Receptor Chemistry 9 Boronic Acids in Saccharide Recognition 10 Calixarenes An Introduction, 2nd Edition 11 Polymeric and Self Assembled Hydrogels From Fundamental Understanding to Applications 12 Molecular Logic-based Computation 13 Supramolecular Systems in Biomedical Fields 14 Synthetic Receptors for Biomolecules Design Principles and Applications... 

So far we have discussed the development of integrated molecular sensors using boronic acids. The systems contain a receptor and reporter (fluorophore or chromophore) as part of a discrete molecular unit. However, another approach toward boronic acid-based sensors is also possible where the receptor and a reporter unit are separate as in a competitive assay. A competitive assay requires that the receptor and reporter (typically a conunercial dye) to associate under the measurement conditions. The receptor-reporter complex is then selectively dissociated by the addition of the appropriate guests. When the reporter dissociates from the receptor, a measurable response is produced (Scheme 6). 

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