Cyclodextrin Aldehydes are Oxidase Mimics

Cyclodextrins containing 6-aldehyde groups were found to catalyse oxidation of aminophenols in the presence of hydrogen peroxide. The catalysis followed Michaelis-Menten kinetics and is related to the catalysis previously observed with cyclodextrin ketones. A range of different cyclodextrin aldehydes were prepared containing one, two or more aldehydes at the primary rim (6-positions) or a ethoxy-2-al or propoxy-3-al at the secondary rim. 2-O-ethoxy-2-al-beta-cyclodextrin (22) was found to be the best catalyst. The aldehydes are in many cases better catalysts than the ketones, because of their powerful covalent binding of hydrogen peroxide.