Stereoselective benzylic hydroxylation of alkylbenzenes and epoxidation of styrene derivatives catalyzed by the peroxygenase of Agrocybe aegerita

Here we report on the stereoselective benzylic hydroxylation and C1-C2 epoxidation of alkylbenzenes and styrene derivatives, respectively, by a heme-thiolate peroxygenase (EC 1.11.2.1) from the fungus Agrocybe aegerita. Benzylic hydroxylation led exclusively to the (R)-1-phenyl-alkanols. For (R)-1-phenylethanol, (R)-1-phenylpropanol and (R)-1-tetralol, the ee reached > 99%. For longer chain lengths, the enantiomeric excesses (ee) and total turnover numbers (TTN) decreased while the number of by-products, e.g. 1-phenylketones, increased. Epoxidation of straight chain and cyclic styrene derivatives gave a heterogeneous picture and resulted in moderate to excellent ee values and TTN: e.g., in the case of (1R, 2S)-cis-beta-methylstyrene oxide formation, an ee > 99% and a TTN of 110 000 was achieved. Hydroxylation and epoxidation were true peroxygenations, which was demonstrated by the incorporation of O-18 from H-2 O-18(2) into the products. The use of fed-batch devices and varying feeding strategies for the substrate and co-substrate turned out to be a suitable approach to optimize peroxygenase catalysis.