title: Carbon-oxygen bond formation by fungal laccases: cross-coupling of 2,5-dihydroxy-N-(2-hydroxyethyl)-benzamide with the solvents water, methanol, and other alcohols.
abstract: Laccase-catalyzed reactions lead to oxidation of the substrate via a cation radical, which has been described to undergo proton addition to form a quinonoid derivative or nucleophilic attack by itself producing homomolecular dimers. In this study, for the substrate 2,5-dihydroxy-N-(2-hydroxyethyl)-benzamide, we show that, besides the quinonoid form of substrate, all products formed are nonhomomolecular ones. Indeed, without addition of a reaction partner, heteromolecular products are formed from the quinonoid form of the laccase-substrate and the solvents water or methanol present in the incubation assay. Consequently, in laccase catalyzed syntheses performed in aqueous solutions or in the presence of methanol or other alcohols, undesirable heteromolecular coupling reactions between the laccase substrate and solvents must be taken into account. Additionally, it could be shown at the example of methanol and other alcohols that C-O-bound cross-coupling of dihydroxylated aromatic substances with the hydroxyl group of aliphatic alcohols can be catalyzed by fungal laccases.
authors.affiliation: Institute for Microbiology, Ernst-Moritz-Arndt-University Greifswald, Friedrich-Ludwig-Jahn-Str. 15, 17487 Greifswald, Germany. manda@uni-greifswald.de
authors.forename: Katrin
authors.initials: K
authors.lastname: Manda
authors.forename: Dirk
authors.initials: D
authors.lastname: Gördes
authors.forename: Annett
authors.initials: A
authors.lastname: Mikolasch
authors.forename: Elke
authors.initials: E
authors.lastname: Hammer
authors.forename: Enrico
authors.initials: E
authors.lastname: Schmidt
authors.forename: Kerstin
authors.initials: K
authors.lastname: Thurow
authors.forename: Frieder
authors.initials: F
authors.lastname: Schauer
mesh_terms: D000438:Alcohols / Q000378:metabolism; D001549:Benzamides / Q000378:metabolism*; D002244:Carbon; D005658:Fungi / Q000201:enzymology* / Q000378:metabolism; D007700:Kinetics; D042845:Laccase / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D000432:Methanol / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen; D014867:Water / Q000737:chemistry
chemical_list: D000438:Alcohols; D001549:Benzamides; D014867:Water; C055881:gentisamide; D002244:Carbon; D042845:Laccase; D010100:Oxygen; D000432:Methanol