Sugar-induced stereoselectivity in the Fe3+-complexation of boronic acid-appended trihydroxamate-type artificial siderophores

Two linear- and two tripodal-trihydroxamate siderophore mimics, suspending phenylboronic acid as the sugar-binding site, have been newly prepared. The se siderophore mimics strongly bind Fe3+ ions to give rise to the ligand-Fe 3+ 1:1 complexes over a wide range of pH 2 to 11. Circular dichroism (CD) s pectra of these complexes in the presence of a sugar, D-fructose, exhibit m oderately strong bisignate Cotton effects of first negative and second posi tive signs in aqueous alkaline media. The sign and extent of the observed C D signals depend largely on the solution pH and the concentration and absol ute configuration of the bound sugars, implying that the phenylboronate-sug ar covalent interactions are capable of inducing a chirality around the met al center.