Aromatic ring cleavage of a non-phenolic beta-O-4 lignin model dimer by laccase of Trametes versicolor in the presence of 1-hydroxybenzotriazole

The novel cleavage products, 2,3-dihydroxy-1-(4-ethoxy-3-methoxyphenyl) -1- formyloxypropane (II) and 1-(4-ethoxy-3-methoxyphenyl)- 1,2,3-trihydroxypro pane-2, 3-cyclic carbonate (III) were identified as products of a non-pheno lic beta-O-4 lignin model dimer, 1,3-dihydroxy-2-(2,6-dimethoxylphenoxy)-1- (4-ethoxy-3-methoxyphenyl)propane (I), by a Trametes versicolor laccase in the presence of 1-hydroxybenzotriazole (1-HBT), An isotopic experiment with a C-13-labeled lignin model dimer, 1,3-dihydroxy-2-(2,6-[U-ring-C-13]dimet hoxyphenoxy)-1- (4-ethoxy-3-methoxyphenyl)propane (I-C-13) indicated that t he formyl and carbonate carbons of products II and III were derived from th e beta-phenoxy group of beta-O-4 lignin model dimer I as aromatic ring clea vage fragments. These results show that the laccase-1-HBT couple could cata lyze the aromatic ring cleavage of non-phenolic beta-O-4 lignin model diner in addition to the beta-ether cleavage, C alpha-C beta cleavage, and C alp ha-oxidation. (C) 1999 Federation of European Biochemical Societies.