341036-48-4Relevant articles and documents
New mediators for the enzyme laccase: Mechanistic features and selectivity in the oxidation of non-phenolic substrates
Astolti, Paola,Brandi, Paolo,Galli, Carlo,Gentili, Patrizia,Gerini, Maria Francesca,Greci, Lucedio,Lanzalunga, Osvaldo
, p. 1308 - 1317 (2005)
New mediators of laccase have been comparatively evaluated and ranked towards the benchmark aerobic oxidation p-MeO-benzyl alcohol. The mechanism of oxidation of this non-phenolic substrate by each mediator, which is initially oxidised by laccase to the Medoxform, has been assessed among three alternatives. The latter make the phenoloxidise laccase competent for the indirect oxidation of non-phenolic (and thus 'unnatural') substrates. Experimental characterisation of the mediators, by means of spectrophotometric, electrochemical and thermochemical survey, is reported. Clear-cut evidence for the formation of a benzyl radical intermediate in the oxidation of a particular benzyl alcohol with laccase and a 2 bonds on the lefthand side signN-OH mediator is attained by means of a trapping experiment. The selectivity of the laccase-catalysed oxidation of two competing lignin and polysaccharide model compounds has been assessed by using the highly proficient 4-MeO-HPI mediator, and found very high in favour of the former model. This evidence is in keeping with the operation of a radical hydrogen-abstraction process that efficiently cleaves the benzylic rather than the aliphatic C-H bond of the two models. Significant is the finding that catechol, i.e., a model of recurring phenolic structures in lignin, once oxidised to aryloxyl radical by laccase is capable to mediate a radical oxidation of non-phenolic compounds. This supports a fully-fledged role of laccase as a delignifying enzyme in nature by way of no other mediators than the very phenolic groups of lignin. Finally, an evaluation of the dissociation energy of the NO H bond of HBT, which is not accessible experimentally, is provided by the use of a thermochemical cycle and theoretical calculations. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2005.
Straightforward synthesis of functionalized chroman-4-ones through cascade radical cyclization-coupling of 2-(allyloxy)arylaldehydes
Zhao, Jingjing,Li, Pan,Li, Xinjian,Xia, Chungu,Li, Fuwei
, p. 3661 - 3664 (2016/03/05)
A novel and direct approach to synthesize a series of phosphonate, azide and hydroxy functionalized chroman-4-ones has been developed. The cascade transformation appears to proceed through an intramolecular addition of an in situ generated acyl radical onto the alkene, followed by a selective nucleophilic radical-electrophilic radical cross coupling.
