Enantioselective epoxidation and carbon-carbon bond cleavage catalyzed by Coprinus cinereus peroxidase and myeloperoxidase

We demonstrate that myeloperoxidase (MPO) and Coprinus cinereus peroxidase (CiP) catalyze the enantioselective epoxidation of styrene and a number of substituted derivatives with a reasonable enantiomeric excess (up to 80%) a nd in a moderate yield. Three major differences with respect to the chlorop eroxidase from Caldariomyces fumago (CPO) are observed in the reactivity of MPO and CiP toward styrene derivatives. First, in contrast to CPO, MPO and CiP produced the (S)-isomers of the epoxides in enantiomeric excess. Secon d, for MPO and CiP the H2O2 had to be added very slowly (10 eq in 16 h) to prevent accumulation of catalytically inactive enzyme intermediates. Under these conditions, CPO hardly showed any epoxidizing activity; only with a h igh influx of H2O2 (300 eq in 1.6 h) was epoxidation observed. Third, both MPO and CiP formed significant amounts of (substituted) benzaldehydes as si de products as a consequence of C-alpha-C-beta bond cleavage of the styrene derivatives, whereas for CPO and cytochrome c peroxidase this activity is not observed. C-alpha-C-beta cleavage was the most prominent reaction catal yzed by CiP, whereas with MPO the relative amount of epoxide formed was hig her. This is the first report of peroxidases catalyzing both epoxidation re actions and carbon-carbon bond cleavage. The results are discussed in terms of mechanisms involving ferryl oxygen transfer and electron transfer, resp ectively.