Aqueous Sugar Sensing by Boronic-Acid-Based Artificial Receptors

Abstract

A review with 28 refs. on the development of new receptor mols. that can precisely recognize sugar mols., a no. of diboronic acids were prepd. Since one boronic acid can react with two OH groups (one diol group) to form a boronate ester, one diboronic acid can immobilize two diol units to form a sugar-contg. macrocycle. The selectivity can be tuned by the relative spatial position of the two boronic acids and the complexation event can be read out by CD spectroscopy. When a boronic acid group is combined intramolecularly with an aminomethylfluorophore, the complexation event can be conveniently read out by fluorescence spectroscopy. This is a novel application of a PET (photoinduced electron transfer) sensor; the sugar-binding changes the strength of the B...N interaction, which eventually changes the fluorescence quenching efficiency of the amine. We have demonstrated using a chiral 1,1'-binaphthyl group as a fluorophore that even chiral recognition of sugars is possible. The porphyrin skeleton is shown to be useful not only as a platform to control the spatial position of boronic acids but also as a chromophore for reading-out the sugar configuration. These abundant examples support the superiority of boronic-acid-based covalent bond recognition over hydrogen-bond-based non-covalent bond recognition for sugars in water. [on SciFinder (R)]