The pK_as as well as apparent binding constants of several 3-amino-substituted benzoxaboroles with alizarin red S (ARS) and some biologically important sugars have been evaluated and compared with that of the parent aminomethylphenylboronic acids. The investigated benzoxaboroles reveal lower acidity than the corresponding boronic acids. All the studied boronic compounds display the usual order of apparent binding constant values with glucose, galactose and fructose. The X-ray structure of the model catechol ester of the morpholinylmethylphenylboronic acid has been determined. The molecules are monomeric zwitterions with a tetracoordinated boron atom. The intermolecular interactions have been described with the aid of the Hirshfeld surface analysis.