Binding-site Analysis of the Ether Linkages between Lignin and Hemicelluloses in Lignin–Carbohydrate Complexes by DDQ-Oxidation

A Biomimetic Route to Lignin Model Compounds via Silver (I) Oxide Oxidation. 1. Synthesis of Dilignols and Non-cyclic Benzyl Aryl Ethers

“…Assuming that a "bulk" polymerization should allow the best conditions for the formation of non-cyclic --linked lignin substructures, their occurrence is likely to be minimal based on our observations and those of others. This is not to say that lignin-carbohydrate benzyl alkyl ethers do not occur; evidence of the occurrence of such direct cell wall polymer crosslinking structures has been reported (Eriksson et al 1980;Fengel and Wegener 1989;Watanabe et al 1989). It is conceivable that quinone methides formed during lignification of carbohydrate-rich regions of the cell wall react with e. g. hemicellulosic hydroxyls, which are not in competition with phenolic hydroxyls, to form non-cyclic benzyl alkyl ether bonds (Freudenberg 1968;Tanaka et al 1979;Katayama et al 1980).…”

Biodegradation of lignin-carbohydrate complexes

“…1). Watanabe et al (1989) found that mannose, galactose, and glucose are 0-6 ether linked and xylose is 0-2 or 0-3 ether linked to the a benzyl hydroxyl in a neutral fraction of pine LCC. Watanabe et al (1989) Watanabe et al 1989).…”

“…2). The GC-MS analysis of methylated sugar derivatives led Watanabe et al (1989) to conclude that the arabinoglucuronoxylan is bound to the lignin at the 0-2 and 0-3 positions of the xylose units, and that the linkage position in the lignin subunits is in the ~ or conjugated [3 positions of phenyl propane or propene units. Minor (1982) investigated the LC bonds of loblolly pine MWEL to determine the positions of linkages in carbohydrates.…”

Fractionation and characterization of lignin-carbohydrate complexes (LCCs) of Eucalyptus globulus in residues left after MWL isolation. Part II: Analyses of xylan-lignin fraction (X-L)

“…There are three approaches to LC analysis: (1) chemical analytical methods based on selective oxidation with 2,3-dichloro-5,6-cyano-1,4-benzoqinone, (2) isolation of degradation products containing the original LC linkages from the native sample, and (3) direct analysis of native samples and their fractions by means of one-dimensional (1D) nuclear magnetic resonance (NMR; 1 H and 13 C) and twodimensional (2D) NMR methods. The existence of α -ether linkages between lignin and hemicelluloses (Watanabe et al 1989 ) and the ester linkages between lignin and glucuronic acid (Imamura et al 1994 ) were proven by the first method. As to the second method, there are few reports concerning such degradation products (Karlsson et al 2004 ).…”