Ferryl oxygen

Oxidation of benzyl alcohol catalysed by chloroperoxidase exhibits a very high prochiral selectivity involving only the cleavage of the pro-S C-H bond. The reaction mechanism involved the transfer of a hydrogen atom to the ferryl oxygen of the iron-oxo complex. An a-hydroxy-carbon radical and the iron-hydroxy complex P-Fe -OH form. They may lead to the hydrated benzaldehyde or stepwise with the formation of the intermediate a-hydroxy cation. 

Many other species also contain catalases. In bacteria these can contain either haem or dihydroporphyrin (chlorin) prosthetic groups [52], However, the presence of a weak tyrosine-ligation to the iron appears to be present in all cases. This, combined with the lack (present in peroxidases) of an H-bond between an arginine residue and the ferryl oxygen, may explain why catalase compound I is uniquely reactive to H2O2. 

This catalytic asymmetric oxidation yielded J -methylphenylsulfoxide with a productivity of30g/l/day andane.e. >98% [35]. Chloroperoxidase is the most versatile peroxidase with better stability compared to other peroxidases, because spontaneous oxidation can be suppressed in the presence of ascorbic acid or dihydroxyfu-maric acid, and with better enantioselectivity because substrate access to the heme iron and ferryl oxygen favors stereoselective oxygen transfer [36]. Chloroperoxidase has been used for catalyzing the oxidation of cis-cydopropylmethanols with much higher enantioselectivity than trans-isomers [37]. 

In the second step. Compound I oxidizes a second peroxide molecule to molecular oxygen and releases the ferryl oxygen species as water, restoring ferriCAT ... 

Addition of the ferryl oxygen to the internal carbon of a terminal acetylene results, as already discussed, in prosthetic heme alkylation. Addition of the oxygen to the terminal carbon, however, is associated with intramolecular 1,2-shift of the terminal hydrogen to give a ketene (Ortiz de Montellano, 1986). The... 

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