Modular fluorescence sensors for saccharides

Modular photoinduced electron transfer (PET) sensors bearing two phenylboronic acid groups, a pyrene group and alkylene linkers, from trimethylene to octamethylene, have been prepared and evaluated. The diboronic acid systems with tetramethylene 3(4) pentamethylene 3(5) and hexamethylene 3(6) linkers display the greatest enhancement in binding relative to monoboronic acid 4 with D-glucose. The diboronic acid system with the hexamethylene 3(6) linker is particularly D-glucose selective and sensitive. Whilst the diboronic acid systems with the longer heptamethylene 3(7) and octamethylene 3(8) linkers display the greatest enhancement in binding relative to monoboronic acid 4 with D-galactose. All saccharide titrations were performed in methanolic aqueous solution.