o-acetamidophenylboronate esters stabilized toward hydrolysis by an intramolecular O-B interaction: potential linkers for selective bioconjugation via vicinal diol moieties of carbohydrates.

The synthesis and properties of o-acetamidophenylboronic acid 8 and the corresponding 1,2-diol cyclic boronates 13 and 16 are reported. The presence of an O-B interaction in 8 and 13 has been established by 11B and 1H NMR spectroscopy. The O-B interaction stabilizes boronate 13 toward hydrolysis and accelerates esterification of acid 8 in contrast to the non-ortho-substituted boronate 10 and acid 3. The enhanced stability of o-acetamidophenylboronate esters toward hydrolysis suggests their application as vicinal diol protecting groups in carbohydrate synthesis. Through the incorporation of an amino group as a second site for a coupling reaction (e.g. via isothiocyanate 22), o-acetamidophenylboronic acids may serve as novel agents for bioconjugation reactions involving carbohydrate moieties.