An Improved Class of Sugar-Binding Boronic Acids, Soluble and Capable of Complexing Glycosides in Neutral Water

This study describes a new class of carbohydrate-binding boronic acids. ortho-Hydroxymethyl phenylboronic acid (boronophthalide) was shown to be superior to the well-established dialkylamino ("Wulff-type") analogues, and it is more soluble in aqueous solvents. The most significant finding in this work is the surprising ability of ortho-hydroxyalkyl arylboronic acids to complex model glycopyranosides under physiologically relevant conditions. These boronic acid units appear to complex hexopyranosides mainly using their 4,6-diol. This behavior is significant because a majority of cell-surface glycoconjugates present free 4,6-diols. Thus, conjugatable forms of these boronic acids could be used in the design of oligomeric receptors and sensors to exploit multivalency effects. Such receptors could dramatically expand the potential of boronic acids toward the selective recognition of cell-surface glycoconjugates.