抄録
Phenylboronic acid in water exists as an equilibrium mixture of the nonionic trigonal boronic form and the ionic tetrahedral monoboronate form. It is known that the tetrahedral-formed phenylboronate can form significantly stable covalent bonds with polyol compounds including glucose in aqueous solution. Therefore, the binding/dissociation equilibrium between boronic acids and sugar molecules can be controlled with pH change. However, there has been no report on controlling this equilibrium by the external stimulus such as light and magnetic field. Thus, we tried to create a novel photo-swiching compound which can control the binding/dissociation with sugars by photoirradiation as an external stimulus at a constant pH condition. In our strategy, an azobenzene moiety which gives the geometrical change of photoisomerization (cis-trans isomerization) is employed as a photo-switching moiety, which leads the change of the acidity of boronic acid with the electronic and steric effects. Therefore, we synthesized o-, m-, p- azophenylboronic acids (APB) which have phenylboronic acid and azo groups. It was confirmed that the isomerization of synthesized compounds was certainly induced, which was measured by UV-vis and 1H/13C NMR. Furthermore, it was confirmed using 11B NMR measurement that the binding/dissociation ratio to fructose was changed before and after photoirradiation. In this study, it was proved that newly synthesized boronic acid derivatives can control the binding/dissociation to sugar by photo-stimulation at a constant pH condition. In near future, this new sugar-recognition system is expected to be utilized in medical field as a biosensor and so on.
