A detailed examination of boronic acid–diol complexation

Boronic acids bind with compounds containing diol moieties with high affinity through reversible boronate formation. However, the conditions that foster tight binding between the diol and the boronic acid are not well understood. Also, due to the multiple ionic states of both the boronic acid and boronate ester, the equilibrium constants reported in the literature have not always been strictly defined, and therefore there is a lack of ‘comparability’ between the reported values. To address these issues, we have developed a method for examining boronate ester stability using the fluorescent reporter Alizarin Red S. We have used this system to determine the binding constants of a series of diols, and as a basis from which to derive a number of relationships that correlate the various equilibrium constants in the literature.