A Long‐Wavelength Fluorescent Probe for Saccharides Based on Boronic‐Acid Receptor

A single boronic acid-based fluorescent probe (compound CSP) for saccharides was designed and synthesized. The probe, with an α,β-unsaturated ketone conjugated into the coumarin fluorophore, was synthesized by 4 steps from the commercial material 4-diethylamino salicylaldehyde. The electron push-pull effect is enhanced with the N,N-diethyl amino as the electron donor and the carbonyl as the electron acceptor. Both the absorption (463 nm) and emission (616 nm) maxima of CSP are in the visible wavelength region with a Stokes shift of about 150 nm, which ensures CSP a potential probe for biological application. Under near physiological conditions, significant fluorescence enhancement of CSP was observed upon the addition of some saccharides, namely, D-sorbitol, D-fructose, D-glucose, D-mannose and D-galactose. The probe showed relatively high sensitivity towards D-fructose and D-sorbitol, and their detection limits were 0.05 mmol/L and 0.1 mmol/L, respectively.