Benzoxaboroles – Old compounds with new applications

Lewis acidity and sugar receptor activity of 3-amino-substituted benzoxaboroles and their ortho-aminomethylphenylboronic acid analogues

“…The model catechol ester (5a) forms a zwitterionic structure with a tetracoordinated boron center in the solid state. Its formation confirms high Lewis acidity of the catechol ester (5). All the investigated receptors (1, 2 and 3) follow the usual order of apparent binding constants for 5 monoboronic acids and glucose, galactose and fructose (K Glu < K Gal < K Fru ).…”

“…Its formation confirms high Lewis acidity of the catechol ester (5). All the investigated receptors (1, 2 and 3) follow the usual order of apparent binding constants for 5 monoboronic acids and glucose, galactose and fructose (K Glu < K Gal < K Fru ). None of the determined apparent binding constants correlates with pK a of the investigated boronic acid compounds.…”

“…2 The acid-base equilibrium and pKa values of benzoxaboroles. 5 Benzoxaboroles usually display lower pK a (higher Lewis acidity) than the corresponding boronic acids. Owing to that, benzoxaboroles are prone to the tetragonal form in physiological solutions, which is crucial in the sensing of biomolecules.…”

“…4 The sugar binding activity of that simple and easily 30 available compound was reported to be higher than that of the well established ortho-aminomethylphenylboronic acids (Wulfftype receptors). The benzoxaborole structural motif has been applied for medicinal purposes, 5,6 such as inhibition of HIV entry, [7][8][9] antiprotozoal drugs, 10 antibacterial or antifungal agents 11 35 as well as a potential drug delivery scaffold. 12 The diversity of the investigated benzoxaborole structures is quite broad, yet it mostly covers the phenyl ring substituted derivatives.…”

Investigating a Relationship between the Mutagenicity of Arylboronic Acids and 11B NMR Chemical Shifts

“…26 Benzoxaboroles are stable and are not hydrolyzed to their corresponding boronic acid. 27 Therefore, boroxines and pinacol esters will also not be formed. In addition, the boron center in the borole ring is strained and sterically hindered, resulting in a lower pK a than the corresponding arylboronic acid.…”