Binding Assessment of Monosaccharide–Boronic Acid Complexes via Tandem Mass Spectrometry

Benzoxaborole and arylboronic acids bind to monosaccharides in water to form reversible boronic esters with multiple hydroxyl groups. When benzoxaborole binds with a diol or an arylboronic acid binds with a triol on a monosaccharide, a tetrahedral boron anion is formed at the boron atom. These boron anions can be detected as negative ions in mass spectrometry and tandem mass spectrometry, and profiling their fragment anions provides information on the stereo‐ and regiochemical configurations of the hydroxyl groups on the monosaccharides. Borate fragment anions derived from both benzoxaborole and arylboronic acids show differential connections with hydroxyl groups, which reflect the steric structure of the monosaccharide. As the result, we could distinguish monosaccharides by using the differences in the binding abilities of monosaccharide‐boronic acid complexes by means of mass spectrometric analysis.