Guaiacyl-type

However, in the light of the results presented herein, this cannot be stated unequivocally, otherwise it would follow that only guaiacyl type compounds would be obtained as softwood lignin degradation products. It has been found that the native lignin from the softwood white Scots pine also yields p-hydroxybenzaldehyde upon oxidation. Thus, it seems that either coniferyl alcohol is not the only lignin progenitor in woody tissues, or that this coniferyl compound is preceded in the process of... 

It has also been observed that syringyl-type precursors arc transformed in part into guaiacyl-type lignin 78, 90, 91), i.e. a demethoxyla-tion, not merely a dcmcthylation has taken place. It has also been found that sweet almond emulsin hydrolyses syringin only extremely slowly 143) and that pure peroxidase does not oxidize sinapyl alcohol well 71). The metabolism of the sinapyl component of lignin is perhaps not quite as simple as the analogy between its />-coumaryl and conifcryl components suggests. 

Condensed Structures in p-Hydroxyphenyl-Guaiacyl Type DHP. It has been difficult to determine the exact amount of p-hydroxyphenylpropane units in lignin. This can best be illustrated by an example nitrobenzene oxidation of a DHP prepared by the Zutropfverfahren method from a mixture of p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol, gave no detectable p-hydroxybenzaldehyde on alkaline nitrobenzene oxidation... 

C2 and C3 primary alcohol side chains guaiacyl type models substituted in the C6 position with reduced carbon side chains and acetylated derivatives of these models from spectra cf the several hydrol lignin preparations. 

Ether-insoluble hydrol lignin from the acid-catalyzed product seems to be a highly condensed guaiacyl type of preparation which has not been severely degraded during the isolation process. 

The low product yield and S/G ratio indicates that these units are not abundant and that they are mainly of the guaiacyl type... 

Lignin-derived compounds Guaiacyl-type unit ... 

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