"Click-fluors": Triazole-linked saccharide sensors

A series of boronic acid-containing saccharide receptors was synthesised via copper catalysed azide-alkyne cycloaddition (CuAAC) reactions. Their saccharide binding capacity was studied by ¹H and ¹¹B NMR spectroscopy titrations and isothermal titration calorimetry (ITC) techniques. Fluorescent sensors were generated by linking a phenylboronic acid (PBA) receptor with fluorophores via a triazole-linker. Fluorescence titrations with fructose revealed that the substitution pattern about the PBA influences the fluorescence response to saccharides. Titrations studied by ¹H NMR spectroscopy suggested that fructose binding is enhanced when the aromatic ring bearing the boronic acid has the triazole-containing substituent at the ortho position. No evidence of either a dative N-B bond or solvent insertion (between B and N) was observed by ¹¹B NMR spectroscopy. These results demonstrate that synthetic accessible triazole receptors may allow rapid sensor synthesis, screening and discovery.