Selective oxidations with molecular oxygen, catalyzed by chloroperoxidase in the presence of a reductant

Chloroperoxidase (CPO) catalyzes the oxidation of various substrates with molecular oxygen as the primary oxidant, in the presence of dihydroxyfumaric acid (DHF) as a sacrificial reductant. For example, indole is oxidized to 2-oxindale with up to 77% selectivity and thioanisole to the corresponding R-sulfoxide (e.e. > 99%). To our knowledge, these are the first examples of (enantio)selective aerobic oxidations catalyzed by peroxidases. A mechanism is proposed which involves initial formation of hydrogen peroxide via autoxidation of DHF. CPO subsequently uses the hydrogen peroxide for the selective oxidation of the substrate, via an oxygen transfer mechanism. In contrast, horseradish proxidase (HRP) primarily catalyzes the oxidation of DHF via a classical peroxidase mechanism and oxidations of added substrates are aselective. (C) 1999 Elsevier Science B.V. All rights reserved.