Oxidation of amides by laccase-generated aminoxyl radicals

The enzyme laccase from the fungus Trametes villosa catalyses the oxidation of two hydroxylamines ( NO H), i.e., HPI ( N-hydroxy-phthalimide) and HBT (1-hydroxy-benzotriazole), into their corresponding aminoxyl radicals ( NO ) PINO and BTNO. The ensuing oxidation of a few amides and lactames by PINO...

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Bibliographic Details
Published in:Journal of molecular catalysis. B, Enzymatic Enzymatic, 2008-01, Vol.50 (1), p.40-49
Main Authors: Coniglio, Alessandra, Galli, Carlo, Gentili, Patrizia, Vadalà, Raffaella
Format: Article
Language:English
Subjects:
Amides
Aminoxyl radicals
Bioconversions. Hemisynthesis
Biological and medical sciences
Biotechnology
Fundamental and applied biological sciences. Psychology
Laccase
Mediators
Methods. Procedures. Technologies
Oxidation
Semiempirical calculations
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Summary:The enzyme laccase from the fungus Trametes villosa catalyses the oxidation of two hydroxylamines ( NO H), i.e., HPI ( N-hydroxy-phthalimide) and HBT (1-hydroxy-benzotriazole), into their corresponding aminoxyl radicals ( NO ) PINO and BTNO. The ensuing oxidation of a few amides and lactames by PINO and BTNO has been investigated in buffered water solution (pH 5) at room temperature. The results from this chemo-enzymatic approach have been compared with a literature method that generates the aminoxyl radical PINO by the HPI/Co(II)/O 2 chemical system, and uses it for the oxidation of similar amides. The merits of the aminoxyl radicals PINO and BTNO have been comparatively assessed in the chemo-enzymatic method, and the mechanism investigated. A Hammett treatment of the relative reactivity of oxidation of X-substituted- N-acetylbenzylamides in competition experiments supports a rate-determining H-abstraction route. With a few of the investigated substrates, stereoelectronic effects have been uncovered, and a rationalisation of their contribution to the reactivity of the H-abstraction route is offered, and supported by semiempirical calculations.
ISSN:1381-1177
1873-3158
DOI:10.1016/j.molcatb.2007.09.022