On the Mechanism of Formation of Non-Cyclic Benzyl Ethers During Lignin Biosynthesis Part 3. The Reactivity of a β—O—4-Type Quinone Methide with Methyl-α-D-glucopyranoside in Competition with Vanillyl Alcohol. The Formation and the Stability of Benzyl Ethers between Lignin and Carbohydrates

Sipilä, Jussi; Brunow, Gösta

doi:10.1515/hfsg.1991.45.s1.3

Cited by 13 publications

(7 citation statements)

References 14 publications

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“…A lignin-model study using a β- O -4-aryl ether QM compound, QM-GG (shown in Scheme ), was developed by Nakatsubo et al in 1976 . Since then, subsequent studies have been conducted for many purposes, such as studies on the reactivity of QMs toward different nucleophiles ,− and characterization of the syn - and anti -geometric isomers of 3-methoxy-substituted (G-type) QMs. ,, This β- O -4-aryl ether QM has been used to synthesize novel lignin model compounds for LCC linkages, − dibenzodioxocin, and anthrahydroquinone adducts. , …”

Section: Resultsmentioning

confidence: 99%

Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β-O-4 Structures

Zhu

Akiyama

Yokoyama

et al. 2019

J. Agric. Food Chem.

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p-Quinone methides are involved in lignin biosynthesis as transient intermediates, and the aromatization step has a great impact on the chemical structure of the resulting lignin. A series of quinone methides (QMs) were synthesized and allowed to react with water in pH 3–7 buffers at 25 °C to mimic the formation of p-hydroxyphenyl- and guaiacyl-type (H- and G-type, respectively) β-O-4 structures in gymnosperm-plant cell walls. Water addition occurred in 3-methoxy-substituted QMs (G-type QMs) with half-lives of 1.4–15 min. In contrast, nonsubstituted QMs (H-type QMs) were very labile; they were aromatized to β-O-4 products with half-lives of only 10–40 s. The rapid aromatization in H-type QMs may provide an advantage over G-type species for efficiently driving the lignin-polymerization cycle, which possibly contributes to the development of highly lignified compression wood. In the water-addition reaction, the threo isomers of the β-O-4 products were stereopreferentially formed more than the erythro isomers from both G- and H-type QMs (erythro/threo ratios of 24:76 and 50:50, respectively). The proportion of erythro isomers was higher at lower-pH conditions. This pH-dependent trend agrees with findings from a previous study on 3,5-dimethoxy-substituted (syringyl-type, S-type) QMs; thus, this pH-dependent trend is common in H-, G-, and S-type lignin-related QMs. Higher threo-selectivity was obtained by changing the β-etherified aromatic rings from G- to H-type. A similar but weaker effect was also observed by changing the QM moiety from G- to H-type.

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Section: Resultsmentioning

confidence: 99%

Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β-O-4 Structures

Zhu

Akiyama

Yokoyama

et al. 2019

J. Agric. Food Chem.

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“…They were previously assigned () to lignin−carbohydrate bonds of the benzyl−alkyl ether type according to data for model compounds (). Analysis of published data for various benzyl ether lignin−carbohydrate model compounds ( − ) allows attribution of these signals to linkages between the α-position of lignin with primary hydroxyl groups of carbohydrates, such as those at C-6 in β- d -glucopyranosyl and α- d -galactopyranosyl and C-5 in α- l -arabinofuranosyl units. The CH-α moieties in benzyl ether linkages with secondary hydroxyl groups of carbohydrate give signals at a low proton field, at about δ C /δ H 80−82/4.9−5.25 ( , ), which were not detected in the spectra of the lignin investigated.…”

Section: Resultsmentioning

confidence: 99%

“…[21][22][23][24][25][26][27][28][29][30][31][32]. Although the HMQC spectra are not quantitative, they were obtained under the same conditions, that is, sample concentration, acquisition, and processing parameters.…”

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confidence: 99%

Elucidation of the Structures of Residual and Dissolved Pine Kraft Lignins Using an HMQC NMR Technique

Balakshin

Capanema

Chen

et al. 2003

J. Agric. Food Chem.

155

148

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Comparative studies on the structures of residual and dissolved lignins isolated from pine kraft pulp and pulping liquor have been undertaken using the (1)H-(13)C HMQC NMR technique, GPC, and sugar analysis to elucidate the reaction mechanisms in kraft pulping and the lignin reactivity. A modified procedure for the isolation of enzymatic residual lignins has resulted in an appreciable decrease in protein contaminants in the residual lignin preparations (N content < 0.2%). The very high dispersion of HMQC spectra allows identification of different lignin moieties, which signals appear overlapped in 1D (13)C NMR spectra. Elucidation of the role of condensation reactions indicates that an increase in the degree of lignin condensation during pulping results from accumulation of original condensed lignin moieties rather than from the formation of new alkyl-aryl structures. Among aryl-vinyl type moieties, only stilbene structures are accumulated in lignin in appreciable amounts. Benzyl ether lignin-carbohydrate bonds involving primary hydroxyl groups of carbohydrates have been detected in residual and dissolved lignin preparations. Structures of the alpha-hydroxyacid type have been postulated to be among the important lignin degradation products in kraft pulping. The effect of the isolation method on the lignin structure and differences between the residual and dissolved lignins are discussed.

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“…Therefore, the 4-O-methyl-glucuronic acid residue ester bonds are formed exclusively at the αposition of phenyl propane units. An acidic pH favours the reaction of quinone methide with glucuronic acid 46 . Biosynthesis of secondary cell walls starts by forming cellulose and hemicelluloses.…”

Section: Discussionmentioning

confidence: 99%

Direct evidence of α ester linkages between lignin and glucuronoxylan that reveal the robust heteropolymeric complex in plant cell walls

Nishimura

Nagata

et al. 2022

Preprint

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All vascular plants have lignin that interacts with polysaccharides in cell walls; however, the chemical structure of covalent lignin-carbohydrate (L-C) linkages remains unresolved because of the small number of L-C linkage relative to the polymer main chain. Sample isolation that predominantly maintains intact L-C linkages followed by advanced multi-dimensional NMR showed that the critical L-C linkage between lignin and xylan involves the α-position of the β-aryl ether unit of lignin and the sixth position of the glucuronic acid residue of 4-O-methyl glucuronoxylan. The L-C ester linkages occur primarily at the α-position of lignin, supporting a theoretical synthetic pathway through a quinone methide intermediate. In contrast, the conventional γ-L-C ester was undetectable, indicating that this linkage is not the primary type. Instead, the γ-acetyl-substituted lignin coexisted. The results on primary L-C linkages contribute to plant physiology and biology and advance research into biomass conversion.

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On the Mechanism of Formation of Non-Cyclic Benzyl Ethers During Lignin Biosynthesis Part 3. The Reactivity of a β—O—4-Type Quinone Methide with Methyl-α-D-glucopyranoside in Competition with Vanillyl Alcohol. The Formation and the Stability of Benzyl Ethers between Lignin and Carbohydrates

Cited by 13 publications

References 14 publications

Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β-O-4 Structures

Lignin-Biosynthetic Study: Reactivity of Quinone Methides in the Diastereopreferential Formation of p-Hydroxyphenyl- and Guaiacyl-Type β-O-4 Structures

Elucidation of the Structures of Residual and Dissolved Pine Kraft Lignins Using an HMQC NMR Technique

Direct evidence of α ester linkages between lignin and glucuronoxylan that reveal the robust heteropolymeric complex in plant cell walls

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