Exploration and exploitation of the uncommon pH profile of the dynamic covalent interactions between boronic acids and N-acetylneuraminic acids

Zwitterion–neutral form equilibria and binding selectivity of pyridineboronic acids

“…With phenylboronic acid the binding with site A occurs at low and the binding with site B at high pH values. 11,20 High pH is necessary for the binding to the glycerol chain because aliphatic diols form stable esters only with boronate anions and the p K a of phenylboronic acid is about 9, but with low p K a1 of pyridineboronic acids the interaction through the glycerol chain might be possible already in neutral solutions. To see a probable contribution of such an interaction we performed a comparative study of the interaction of 3-PyBA with lactic acid which contains the same α-hydroxycarboxylate fragment as sialic acid but lacks the glycerol side chain.…”

“…Also, there is no clear understanding of the reasons for strong binding of sialic acid to heterocyclic boronic acids in acidic solutions although several important aspects of binding mechanisms of pyridineboronic acids are discussed in a recent comprehensive review on sialic acid recognition. 11 The purposes of this paper are to get a more complete description of zwitterion–neutral form equilibria of pyridineboronic acids in different reaction media and to interpret their affinity and selectivity toward different diols at variable pH and solvent composition. The structures of di- and polyols employed in this study are shown in Chart 1.…”