EFFECT OF HEMICELLULOSES ON DEHYDROGENATIVE POLYMERIZATION OF SINAPYLALCOHOL .2. FORMATION OF BETA-GAMMA LINKAGE IN THE PRESENCE OF PECTIN

In the plant cell wall, lignin was deposited in the matrix of polysacc harides through the lignification process. To investigate the effect o f hemicelluloses on dehydrogenative polymerization, sinapyl alcohol wa s reacted by horseradish peroxidase/H2O2 in the presence of pectin by the Zulaufverfahren method. Reaction products were acetylated and sepa rated by preparative thin-layer chromatography (PTLC). The chemical st ructures of the products were identified to be d,l-syringaresinol and hydroxyphenyl)-4-hydroxymethyl-5-hydroxy-1-pentene (beta-gamma type di mer). The latter structure may be present in a native lignin and was p roduced by the ionic addition of beta-carbanion of sinapyl alcohol thr ough the extended quinonemethide-intermediate. No paper has suggested a presence of the structure in a native lignin or reported an isolatio n of beta-gamma type dimer during dehydrogenative polymerization of mo nolignols. However, the production of the compound during dehydrogenat ive polymerization of sinapyl alcohol by peroxidase/H2O2 under acidic condition suggests the presence of this substructure in native lignin.