Chirality sensing of saccharides using a boronic acid-appended chiral ferrocene derivative

Abstract

A diboronic acid-appended chiral ferrocene derivative ( R )-9 was designed and synthesized. This chiral ferrocene scaffold was obtained by resolution of the diastereomer with a monosaccharide derivative. One can therefore expect that ( R )-9 would show d/ l selectivity for specific monosaccharides. The complex formation of ( R )-9 with various saccharides using the two boronic acid functions was conveniently monitored by a change in the circular dichroism (CD) spectra. The CD spectral change (Δ[ θ]) induced by added monosaccharides was chiroselective: in particular, d/ l-alloses and d/ l-galactoses induced the 8.0- and 7.0-fold difference in the magnitude of the CD spectral change. The association constants for d- and l-saccharides ( K D and K L, respectively) were determined: among them, ( R )-9 showed a significant discrimination ability for mannose ( K L/ K D=2.6) and arabinose ( K L/ K D=1/2.4). The origin of d/ l selectivity was discussed on the basis of computational studies on ( R )-9·saccharide complexes.