Fenton-like Chemistry by a Copper(I) Complex and H2O2 Relevant to Enzyme Peroxygenase C-H Hydroxylation

Abstract

Lytic polysaccharide monooxygenases have received significantattentionas catalytic convertors of biomass to biofuel. Recent studies suggestthat its peroxygenase activity (i.e., using H2O2 as an oxidant) is more important than its monooxygenase functionality.Here, we describe new insights into peroxygenase activity, with acopper-(I) complex reacting with H2O2 leadingto site-specific ligand-substrate C-H hydroxylation.[Cu-I(TMG(3)tren)](+) (1)(TMG(3)tren = 1,1,1-Tris-{2-[N (2)-(1,1,3,3-tetramethylguanidino)]-ethyl}-amine) and a dry source ofhydrogen peroxide, (o-Tol(3)P O & BULL;H2O2)(2) react in the stoichiometry, [Cu-I(TMG(3)tren)](+) + H2O2 & RARR; [Cu-I(TMG(3)tren-OH)](+) +H2O, wherein a ligand N-methyl group undergoeshydroxylation giving TMG(3)tren-OH. Furthermore, Fenton-typechemistry (Cu-I + H2O2 & RARR; Cu-II-OH + & BULL;OH) is displayed, in which (i) a Cu-(II)-OH complexcould be detected during the reaction and it could be separately isolatedand characterized crystallographically and (ii) hydroxyl radical (& BULL;OH)scavengers either quenched the ligand hydroxylation reaction and/or(iii) captured the & BULL;OH produced.