Search

Rapid development of research on the chemistry of boronic acids is connected with their applications in organic synthesis, analytical chemistry, materials' chemistry, biology and medicine. In many applications Lewis acidity of boron atoms plays an important role. Special group of arylboronic acids are fluoro-substituted compounds, in which the electron withdrawing character of fluorine atoms influences their properties. The present paper deals with fluoro-substituted boronic acids and their derivatives: esters, benzoxaboroles and boroxines. Properties of these compounds, i.e. acidity, hydrolytic stability, structures in crystals and in solution as well as spectroscopic properties are discussed. In the next part examples of important applications are given. [ABSTRACT FROM AUTHOR]

2,6-Diformylphenylboronic acid has been synthesized and characterized both in the solid state as well as in solution. In crystal, an unusual structural pattern has been found with the formation of intermolecular hydrogen bonds by B(OH) 2 and CHO groups as well as water molecules. In solution tautomeric equilibrium with the formation of oxaborole ring by one of the formyl groups was proved on the basis of multinuclear NMR spectroscopy. The title compound reacts with secondary mono- and diamines to form various types of substituted benzoxaboroles, which have been characterized by XRD and spectroscopic methods. [ABSTRACT FROM AUTHOR]

5-Fluoro-2,1-benzoxaborol-1(3H)-ol, a potent antifungal drug also known as Tavaborole or AN2690, has been compared with its three isomers in terms of its activity against several fungi as well as p K a and multinuclear NMR characterization. The molecular and crystal structure of 6-fluoro-2,1-benzoxaborol-1(3H)-ol was determined and compared with that of AN2690. [ABSTRACT FROM AUTHOR]

3-Piperazine-bis(benzoxaborole) and its bis(phenylboronic acid) analogue were investigated in terms of their fungicidal activity. The study was carried out against five filamentous fungi: Aspergillus terreus, Fusarium dimerum, Fusarium solani, Penicillium ochrochloron and Aspergillus niger. 3-Piperazine-bis(benzoxaborole) revealed higher inhibitory activity towards the examined strains than standard antibiotic (amphotericin B), whereas bis(phenylboronic acid) proved to be inactive. The study unequivocally showed that the presence of the heterocyclic benzoxaborole system is essential for antifungal action of the examined compounds. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A series of substituted phenylboronic acids and benzoxaboroles were evaluated for their antimicrobial activity. Antibacterial and antifungal action activity of several compounds was tested against Escherichia coli 67, Staphylococcus aureus 209-p, Mycobacterium luteum VCM B-868, Aspergillus niger VCM F-1119 and Candida tenuis VCM Y-70. Substituted phenylboronic acids have low biological activity against all the investigated species. Benzoxaboroles reveal higher biological activity in comparison with the corresponding acids. The highest activity was observed for small benzoxaborole molecules, and the unsubstituted benzoxaborole has only slightly lower biological activity as compared with the 5-fluoro-substituted one (AN2690). The compound possessing two oxaborole fragments has very high biological activity towards Mycobacterium luteum and both investigated fungi. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In the reaction of 2-formylphenylboronic acid with secondary amines different products are formed depending on the structure of the amines. For aliphatic amines the reaction proceeds with the formation of 3-amino-substituted benzoxaboroles or with the formation of complexed boroxins. A crystal structure of the benzoxaborole with a thiomorpholinyl substituent was determined. [ABSTRACT FROM AUTHOR]

Abstract: This comprehensive review covers the structure, methods of synthesis, properties and fields of application of benzoxaboroles – derivatives of phenylboronic acids. Some of the title compounds were described over 50years ago, however most of them have been investigated only recently due to their exceptional properties and wide applications. In addition to their usage as building blocks and protecting groups in organic synthesis, certain benzoxaboroles display biological activity and are under clinical trials. They also bind hydroxyl compounds and thus can be applied as molecular receptors for sugars and glycoconjugates. [Copyright &y& Elsevier]

Benzoxaboroles emerged recently as molecules of high medicinal potential with Kerydin® (Tavaborole) and Eucrisa® (Crisaborole) currently in clinical practice as antifungal and anti-inflammatory drugs, respectively. Over a dozen of 3-amino benzoxaboroles, including Tavaborole's derivatives, have been synthetized and characterized in terms of their activity against Candida albicans as a model pathogenic fungus. The studied compounds broaden considerably the structural diversity of reported benzoxaboroles, enabling determination of the influence of the introduction of a heterocyclic amine, a fluorine substituent as well as the formyl group on antifungal activity of those compounds. The determined zones of the growth inhibition of examined microorganism indicate high diffusion of majority of the studied compounds within the applied media as well as their reasonable activity. The Minimum Inhibitory Concentration (MIC) values show that the introduction of an amine substituent in position "3" of the benzoxaborole heterocyclic ring results in a considerable drop in activity in comparison with Tavaborole (AN2690) as well as unsubstituted benzoxaborole (AN2679). In all studied cases the presence of a fluorine substituent at position para to the boron atom results in lower MIC values (higher activity). Interestingly, introduction of a fluorine substituent in the more distant piperazine phenyl ring does not influence MIC values. As determined by X-ray studies, introduction of a formyl group in proximity of the boron atom results in a considerable change of the boronic group geometry. The presence of a formyl group next to the benzoxaborole unit is also detrimental for activity against Candida albicans. [ABSTRACT FROM AUTHOR]

The review discusses the structures, properties and applications of ortho -substituted phenylboronic acids. The compounds were compared with meta - and para -isomers, indicating differences resulting from the presence of a substituent in close proximity to the boron group. The effect of an individual substituent on the electron density on boron atom and, as a result, on the acidity constant of these compounds were discussed. Geometric parameters for compounds with known crystal structures were collected and their relationships with the possibility of forming intramolecular hydrogen bonds were evaluated. The most important groups of ortho -substituted boronic acids were evaluated from the point of view of their use in synthesis, analytical chemistry as well as their biological activity. Image 1 • Comparison of ortho-substituted phenylboronic acids with other isomers. • Acidity constant values. • Crystal structure. • Compounds of special significance: formyl- and aminomethyl-substituted phenylboronic acids, benzoxaboroles. • Examples of important applications. [ABSTRACT FROM AUTHOR]