Metalloglycosidase Mimics: Oxidative Cleavage of Saccharides Promoted by Multinuclear Copper Complexes under Physiological Conditions

Abstract

Degradation of saccharides is relevant to the design of catalytic therapeutics, the production of biofuels, inhibition of biofilms, as well as other applications in chemical biology. Herein, we report the design of multinuclear Cu complexes that enable cleavage of saccharides under physiological conditions. Reactivity studies with para-nitrophenyl (pNP)-conjugated carbohydrates show that dinuclear Cu complexes exhibit a synergistic effect and promote faster and more robust cleavage of saccharide substrates, relative to the mononuclear Cu complex, while no further enhancement is observed for the tetranuclear Cu complex. The use of scavengers for reactive oxygen species confirms that saccharide cleavage is promoted by the formation of superoxide and hydroxyl radicals through Cu^II/I redox chemistry, similar to that observed for native copper-containing lytic polysaccharide monooxygenases (LMPOs). Differences in selectivity for di- and tetranuclear Cu complexes are modest. However, these are the first reported small multinuclear Cu complexes that show selectivity and reactivity against mono- and disaccharide substrates and form a basis for further development of metalloglycosidases for applications in chemical biology.