Coordination mode and reactivity of copper(II) complexes with kasugamycin

Protonation and Cu(II) coordination of kasugamycin were studied by potentiometry, UV-vis, CD, EPR, 13C NMR, and 1H NMR. Mononuclear complexes with stoichiometries ranging from CuHL to CuH(-1)L were found. The aminoamidine moiety provides the coordination site in the CuHL species. The additional axial coordination of the amino nitrogen of the aminosugar ring is present in CuL. Finally, the CuH(-1)L complex is formed as a result of a deprotonation and coordination of the hydroxyl group of the inositol ring. The non-planar arrangement of the chelate rings results in the relative stabilization of a Cu(I) species. As a consequence, Cu(I) and superoxide radicals are involved in the redox mechanism of H(2)O(2) activation by the Cu(II) complex of kasugamycin.