A New Class of Fluorescent Boronic Acids That Have Extraordinarily High Affinities for Diols in Aqueous Solution at Physiological pH

Abstract

The boronic acid group is an important recognition moiety for sensor design. Herein, we report a series of isoquinolinylboronic acids that have extraordinarily high affinities for diol‐containing compounds at physiological pH. In addition, 5‐ and 8‐isoquinolinylboronic acids also showed fairly high binding affinities towards D‐glucose (K_a=42 and 46 M⁻¹, respectively). For the first time, weak but encouraging binding of cis‐cyclohexanediol was found for these boronic acids. Such binding was coupled with significant fluorescence changes. Furthermore, 4‐ and 6‐isoquinolinylboronic acids also showed the ability to complex methyl α‐D‐glucopyranose (K_a=3 and 2 M⁻¹, respectively).