Substituent effect on anthracene-based bisboronic acid glucose sensors

Earlier we communicated an anthracene-based bisboronic acid sensor for glucose. Aimed at understanding the substituent effect, we have introduced various functional groups, such as the cyano, nitro, and fluoro group on the boronic acid moiety of this glucose sensor. Fluorescent binding studies indicated that the cyano-substituted sensor (4a) has the highest affinity (K 2540 M⁻¹) for glucose, but the lowest selectivity (three-fold over fructose); the fluoro-substituted compound (4c) shows the lowest affinity (630 M⁻¹) and a modest selectivity (15-fold over fructose); and the unsubstituted one (1a) shows the highest selectivity over fructose (43-fold) and a modest affinity (1472 M⁻¹).