Boronic acid

(molecules with vicinal, (1,2) or occasionally (1,3) substituted Lewis base donors (alcohol, amine, carboxylate)).

Boronic acids are used extensively in organic chemistry as chemical building blocks and intermediates predominantly in the Suzuki coupling.

Boronic acids are known to bind to active site serines and are part of inhibitors for porcine pancreatic lipase,[2] subtilisin[3] and the protease Kex2.

[4] Furthermore, boronic acid derivatives constitute a class of inhibitors for human acyl-protein thioesterase 1 and 2, which are cancer drug targets within the Ras cycle.

[25] Aryl boronic acids or esters may be hydrolyzed to the corresponding phenols by reaction with hydroxylamine at room temperature.

[26] The diboron compound bis(pinacolato)diboron[27] reacts with aromatic heterocycles[28] or simple arenes[29] to an arylboronate ester with iridium catalyst [IrCl(COD)]2 (a modification of Crabtree's catalyst) and base 4,4′-di-tert-butyl-2,2′-bipyridine in a C-H coupling reaction for example with benzene: In one modification the arene reacts using only a stoichiometric equivalent rather than a large excess using the cheaper pinacolborane:[30] Unlike in ordinary electrophilic aromatic substitution (EAS) where electronic effects dominate, the regioselectivity in this reaction type is solely determined by the steric bulk of the iridium complex.

[33] One of the key advantages with this dynamic covalent strategy[34] lies in the ability of boronic acids to overcome the challenge of binding neutral species in aqueous media.

Potential applications for this research include blood glucose monitoring systems to help manage diabetes mellitus.

[35] Some commonly used boronic acids and their derivatives give a positive Ames test and act as chemical mutagens.

The mechanism of mutagenicity is thought to involve the generation of organic radicals via oxidation of the boronic acid by atmospheric oxygen.