Oxidation of Phenols

Abstract

The enzyme vanillyl-alcohol oxidase (VAO, E.C. 1.1.3.38) was examined in detail with respect to mechanism, structural properties, and biotechnological applications by van Berkel and coworkers, giving an excellent example of how detailed biochemical studies provide a basis for preparative biocatalytic applications (for recent reviews see['. ' 1). The homooctamer with a monomer mass of 65 kDa was isolated and purified from Penicillium simplicissimum. The catalytic mechanism of VAOcatalyzed oxidation of para-alkyl phenols was studied in detail r3-'1. After initial hydride abstraction from the Ca atom, a binary complex of the intermediate paraquinone methide and reduced FAD reacts with molecular oxygen, regenerating the By this reaction sequence, highly functionalized bicyclo-[2.2.2]-octenes can be obtained from simple phenols and alkenes as starting materials. The overall yields reported are usually satisfactory (> 70%). The Diels-Alder products are racemic, probably because the Diels-Alder reaction proceeds in the bulk organic phase without involvement of tyrosinase.