- Regioselectivity in lignin biosynthesis. The influence of dimerization and cross-coupling
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We have studied the regioselectivity of oxidative phenol coupling in lignin formation using an oxidation system that distinguishes between dimerization reactions and cross-coupling reactions. We found that the regioselectivity of coupling was different in the two reactions. For instance, in coniferyl alcohol dimerization the formation of β-5 coupling product has a slight prevalence over the formation of β-O-4 product; in cross-coupling the β-0-4 mode is favoured in a ratio of ≈10:1. This ratio is higher than that found in isolated softwood lignins. The degree of cross-coupling was influenced only to a small extent by changes in the rates of conventional addition of coniferyl alcohol (Zulauf versus Zutropf conditions). We found that diffusion through a dialysis membrane did effectively suppress the dimerization of coniferyl alcohol. Of the different oxidants investigated, manganese triacetate in acetic acid yielded the highest proportion of cross-coupling product. The Royal Society of Chemistry 2000.
- Syrjaenen, Kaisa,Brunow, Goesta
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- Structures of new aromatics glycosides from a Japanese folk medicine, the roots of Angelica furcijuga
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Three new aromatics glycosides, hyuganosides II, IIIa, and IIIb, were isolated from a Japanese folk medicine, the roots of Angelica furcijuga KITAGAWA. The structures of the new glycosides were determined on the basis of chemical and physicochemical evide
- Morikawa, Toshio,Matsuda, Hisashi,Nishida, Norihisa,Ohgushi, Teruki,Yoshikawa, Masayuki
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Read Online
- In vitro activity-guided identification of antioxidants in aged garlic extract
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Activity-guided fractionation was applied on an aged garlic extract (AGE), reported to show strong antioxidant activity, in order to locate the key in vitro antioxidant ingredients by means of the hydrogen peroxide scavenging (HPS) assay as well as the OR
- Matsutomo, Toshiaki,Stark, Timo D.,Hofmann, Thomas
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- Incorporation of catechyl monomers into lignins: Lignification from the non-phenolic end: Via Diels-Alder cycloaddition?
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Canonical lignification occurs via the coupling of phenolic radicals, in which chain extension can occur only from phenolic ends of growing polymer chains. Radical coupling of catechyl monomers, including caffeyl and 5-hydroxyconiferyl alcohols, gives ris
- Ando, Daisuke,Boerjan, Wout,Elder, Thomas J.,Eugene, Alexis,Kim, Hoon,Lu, Fachuang,Ralph, John,Tobimatsu, Yuki,Vanholme, Ruben
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p. 8995 - 9013
(2021/11/27)
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- Biomimetic Oxidation of Monolignol Acetate and p-Coumarate by Silver Oxide in 1,4-Dioxane
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Lignin acylated with acetate and/or p-coumarate is common in many herbaceous plants. Herein, the biomimetic oxidation of ?3-acylated monolignols with Ag2O was studied to understand the effect of ?3-acyl groups on monolignol polymerization. The oxidation of sinapyl acetate gave ?3-acylated and α-acylated β-O-4 dimers in 71 and 9.5% yields, respectively. The oxidation of sinapyl p-coumarate produced ?3-acylated β-O-4 and ?3-acylated tetralin β-β dimers in 53 and 16% yields, respectively. Only the sinapyl alcohol moiety in sinapyl p-coumarate reacted, and the p-coumarate moiety remained unchanged, suggesting that p-coumaric acid is not incorporated into the lignin backbone in the acylated lignins. All of the ?3-acylated monolignols used in this study produced the ?3-acylated β-O-4 dimers, which suggests that the ?3-acylated monolignols act as lignin monomers. The relatively high yields of the β-O-4 dimers indicate that Ag2O oxidation of the monolignols can be used as an easy method for synthesizing the β-O-4 dimer model compounds.
- Hamada, Masahiro,Kishimoto, Takao,Nakajima, Noriyuki,Urabe, Daisuke,Yamashita, Ayana
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p. 2124 - 2131
(2020/03/06)
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- Three new lignan glycosides from the Firmiana simplex
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In our quest for structurally intriguing compounds from Korean medicinal plant sources, chromatographic separation of the 80% MeOH extract from Firmiana simplex resulted in the isolation and identification of three new lignan glycosides (1-3), together with six known lignan glycosides (4-9). The structures of 1-3 were determined on the basis of spectroscopic analyses, including extensive 2D-NMR and enzyme hydrolysis. Nitric oxide (NO) production was evaluated in the lipopolysaccharide-Activated microglial cell line, BV-2 to investigate the anti-neuroinflammatory effects of the isolated compounds (1-9). Compound 7 marginally inhibited NO levels with IC50 values of 59.83 μM.
- Woo, Kyeong Wan,Park, Jong Eel,Cha, Joon Min,Subedi, Lalita,Kim, Sun Yeou,Lee, Kang Ro
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- Anti selective glycolate aldol reactions of (: S)-4-isopropyl-1-[(R)-1-phenylethyl]imidazolidin-2-one: application towards the asymmetric synthesis of 8-4′-oxyneolignans
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The anti selective glycolate aldol reactions of (S)-4-isopropyl-1-[(R)-1-phenylethyl]imidazolidin-2-one auxiliary have been standardized with high yields and excellent diastereoselectivities on various substituted aryl, allyl and alkyl aldehydes. The optimized reaction conditions were employed for the stereoselective synthesis of oxyneolignans.
- Gangar, Mukesh,Ittuveetil, Avinash,Goyal, Sandeep,Pal, Anang,Harikrishnan,Nair, Vipin A.
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p. 102116 - 102126
(2016/11/09)
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- The synthesis and analysis of advanced lignin model polymers
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If the lignin-first biorefinery concept becomes a reality, high quality lignins close in structure to native lignins will become available in large quantities. One potential way to utilise this renewable material is through depolymerisation to aromatic chemicals. This will require the development of new chemical methods. Here, we report the synthesis and characterisation of advanced lignin model polymers to be used as tools to develop these methods. The controlled incorporation of the major linkages in lignin is demonstrated to give complex hardwood and softwood lignin model polymers. These polymers have been characterised by 2D HSQC NMR and GPC analysis and have been compared to isolated lignins.
- Lancefield,Westwood
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p. 4980 - 4990
(2015/11/16)
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- On the reactivity of the Melanocarpus albomyces laccase and formation of coniferyl alcohol dehydropolymer (DHP) in the presence of ionic liquid 1-allyl-3-methylimidazolium chloride
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Some ionic liquids are able to dissolve wood, including lignin and lignocellulose, and thus they provide an efficient reaction media for modification of globally abundant wood-based polymers. Lignin can be modified with laccases (EC 1.10.3.2), multicopper
- Lahtinen, Maarit,Viikari, Liisa,Karhunen, Pirkko,Asikkala, Janne,Kruus, Kristiina,Kilpel?inen, Ilkka
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p. 169 - 177
(2013/01/15)
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- Synthesis and characterization of new 5-linked pinoresinol lignin models
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Pinoresinol structures, featuring a β-β′-linkage between lignin monomer units, are important in softwood lignins and in dicots and monocots, particularly those that are downregulated in syringyl-specific genes. Although readily detected by NMR spectroscopy, pinoresinol structures largely escaped detection by β-ether-cleaving degradation analyses presumably due to the presence of the linkages at the 5 positions, in 5-5′- or 5-O-4′-structures. In this study, which is aimed at helping better understand 5-linked pinoresinol structures by providing the required data for NMR characterization, new lignin model compounds were synthesized through biomimetic peroxidase-mediated oxidative coupling reactions between pre-formed (free-phenolic) coniferyl alcohol 5-5′- or 5-O-4′-linked dimers and a coniferyl alcohol monomer. It was found that such dimers containing free-phenolic coniferyl alcohol moieties can cross-couple with the coniferyl alcohol producing pinoresinol-containing trimers (and higher oligomers) in addition to other homo- and cross-coupled products. Eight new lignin model compounds were obtained and characterized by NMR spectroscopy, and one tentatively identified cross-coupled β-O-4′-product was formed from a coniferyl alcohol 5-O-4′-linked dimer. It was demonstrated that the 5-5′- and 5-O-4′-linked pinoresinol structures could be readily differentiated by using heteronuclear multiple-bond correlation (HMBC) NMR spectroscopy. With appropriate modification (etherification or acetylation) to the newly obtained model compounds, it would be possible to identify the 5-5′- or 5-O-4′-linked pinoresinol structures in softwood lignins by 2D HMBCN MR spectroscopic methods. Identification of the cross-coupled dibenzodioxocin from a coniferyl alcohol 5-5′-linked moiety suggested that thioacidolysis or derivatization followed by reductive cleavage (DFRC) could be used to detect and identify whether the coniferyl alcohol itself undergoes 5-5′-cross-linking during lignification. Super model: In this study, aimed at helping to better understand 5-linked pinoresinol structures by providing the required data for NMR structural characterization, new lignin model pinoresinol compounds were synthesized through biomimetic peroxidase-mediated oxidative coupling between pre-formed (free-phenolic) 5-5′- or 5-O-4′-linked coniferyl alcohol dimers and a coniferyl alcohol monomer (examples with 5-O-4′-linked dimers are shown in the scheme).
- Yue, Fengxia,Lu, Fachuang,Sun, Runcang,Ralph, John
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supporting information
p. 16402 - 16410
(2013/02/23)
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- A novel 8,4′-oxyneolignan diglycoside from Ligusticum sinensis
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A novel 8,4′-oxyneolignan diglycoside, named ligusinenoside d (1), was isolated from the rhizomes of Ligusticum sinensis, together with five known analogues 2-6. The absolute configurations of 1 and 2 were elucidated by means of enzymatic hydrolysis and spectroscopic data.
- Ma, Jian Ping,Tan, Chang Heng,Zhu, Da Yuan,Jin, Ling
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experimental part
p. 1454 - 1456
(2012/06/01)
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- Hitherto unrecognized fluorescence properties of coniferyl alcohol
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We instituted a quasi-quality assurance program for demonstrating coniferyl alcohol's fluorescence and fluorescence diminishment following enzymatic oxidation. The magnitude of diminishment was a measure of catalysis. High throughput screening was performed in pseudo-kinetic and endpoint modes by measuring the fluorescence at 416 nm following excitation at 290, 310 or 340 nm. Dose-response tracings were linear between two and three orders of magnitude with average limits of detection and quantitation of 1.8 and 6.9 μM coniferyl alcohol, respectively. Oxidation was evident with 0.025 μg/mL laccase or 0.003 μg/mL peroxidase or inside 5 min using 0.5 μg/mL laccase or 5 μM substrate. Sodium chloride inhibited (IC50, 25 mM) laccase oxidation of coniferyl alcohol. Fluorescence from 10 concentrations (1 to 1000 μM) of coniferyl alcohol was stable for 24 hours over 14 excitation/emission cycles at 3 different combinations of excitation and emission wavelengths. In conclusion, coniferyl alcohol absorption and fluorescence assays should facilitate biomass lignin analyses and improve delignification.
- Achyuthan, Komandoor Elayavalli,Adams, Paul David,Datta, Supratim,Simmons, Blake Alexander,Singh, Anup Kumar
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experimental part
p. 1645 - 1667
(2010/06/13)
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- An enantiocomplementary dirigent protein for the enantioselective lacease-catalyzed oxidative coupling of phenols
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(+)- or (-)-plnoreslnol: that Is the question. Which of the two enantiomeric lignans is formed during laccasecatalyzed phenol coupling of (E)-coniferyl alcohol (1) depends on the dirigent protein. In the presence of the first enantiocomplementary dirigent protein AtDIR6, (-)-2 is formed (78 % ee). Preferential formation of (+)-2 is observed in the presence of the dirigent protein FiDIR1, whereas only racemic 2 is formed in the absence of dirigent proteins
- Pickel, Benjamin,Constantin, Mihaela-Anca,Pfannstiel, Jens,Conrad, Juergen,Beifuss, Uwe,Schaller, Andreas
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supporting information; experimental part
p. 202 - 204
(2010/03/30)
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- Glycosides from the root of Iodes cirrhosa
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Seven new neolignan glycosides (1-7), two arylglycerol glycosides (8, 9), and 18 known glycosides have been isolated from an ethanolic extract of the root of Iodes cirrhosa. Their structures including absolute configurations were determined by spectroscop
- Gan, Maoluo,Zhang, Yanling,Lin, Sheng,Liu, Mingtao,Song, Weixia,Zi, Jiachen,Yang, Yongchun,Fan, Xiaona,Shi, Jiangong,Hu, Jinfeng,Sun, Jiandong,Chen, Naihong
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experimental part
p. 647 - 654
(2009/04/04)
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- Initial steps of the peroxidase-catalyzed polymerization of coniferyl alcohol and/or sinapyl aldehyde: Capillary zone electrophoresis study of pH effect
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Capillary zone electrophoresis has been used to monitor the first steps of the dehydrogenative polymerization of coniferyl alcohol, sinapyl aldehyde, or a mixture of both, catalyzed by the horseradish peroxidase (HRP)-H2O2 system. When coniferyl alcohol was the unique HRP substrate, three major dimers were observed (β-5, β-β, and β-O-4 interunit linkages) and their initial formation velocity as well as their relative abundance varied with pH. The β-O-4 interunit linkage was thus slightly favored at lower pH values. In contrast, sinapyl aldehyde turned out to be a very poor substrate for HRP except in basic conditions (pH 8). The major dimer observed was the β,β′-di-sinapyl aldehyde, a red-brown exhibiting compound which might partly participate in the red coloration usually observed in cinnamyl alcohol dehydrogenase-deficient angiosperms. Finally, when a mixture of coniferyl alcohol and sinapyl aldehyde was used, it looked as if sinapyl aldehyde became a very good substrate for HRP. Indeed, coniferyl alcohol turned out to serve as a redox mediator (i.e. shuttle oxidant ) for the sinapyl aldehyde incorporation in the lignin-like polymer. This means that in particular conditions the specificity of oxidative enzymes might not hinder the incorporation of poor substrates into the growing lignin polymer.
- Fournand, David,Cathala, Bernard,Lapierre, Catherine
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p. 139 - 146
(2007/10/03)
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- Regioselectivity in oxidative cross-coupling of phenols. Application to the synthesis of dimeric neolignans
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The problems of regioselectivity in oxidative coupling of phenols are outlined, and recent research on the application to the synthesis of lignans and neolignans is reviewed. Lignans and neolignans are dimers that are typically formed by oxidative coupling of propenyl phenols. The coupling of structurally different phenols (cross-coupling) is an extension of this synthesis. Recent results show that cross-coupling can be achieved if the phenols have compatible reactivities. The regioselectivity is often quite different in cross-coupling compared to dimerization. Coupling of phenols with widely different rates of oxidation is difficult but can be achieved if the concentration of the more reactive phenol can be kept low enough during the reaction, for instance by diffusion through a dialysis membrane.
- Syrj?nen, Kaisa,Brunow, G?sta
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p. 365 - 370
(2007/10/03)
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- Salen complexes with bulky substituents as useful tools for biomimetic phenol oxidation research
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The catalytic properties of bulky water-soluble Co-, Cu-, Fe- and Mn-salen complexes in the oxidation of phenolic lignin model compounds have been studied in aqueous water-dioxane solutions (pH 3-10). Mn catalysts were found to oxidize coniferyl alcohol in a same reaction time as horseradish peroxidase (HRP) enzyme and Mn and Co catalysts showed different regioselectivity suggesting a different substrate to catalyst interaction in the oxidative coupling. When the oxidation of material more relevant to plant polyphenolics was studied, the results indicated that the complexes catalyze one- and two-electron oxidations depending on the bulk of the substrate. Copyright
- Haikarainen, Anssi,Sipil?, Jussi,Pietik?inen, Pekka,Pajunen, Aarne,Mutikainen, Ilpo
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p. 1633 - 1638
(2007/10/03)
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- Oxidative cross coupling of p-hydroxycinnamic alcohols with dimeric arylglycerol β-aryl ether lignin model compounds. The effect of oxidation potentials
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Oxidation of p-hydroxycinnamyl alcohols together with dimeric lignin model compounds containing arylglycerol β-aryl ether structures was found, under certain conditions, to yield cross coupling products with β-aryl ether and 5,5′-biphenyl bonds. Cross cou
- Syrjaenen, Kaisa,Brunow, Goesta
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p. 3425 - 3429
(2007/10/03)
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- Revised structure for a neolignan from Brucea javanica
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On the basis of 1H and 13C NMR spectral comparison with natural and synthetic compounds, the neolignan isomers isolated from Brucea javanica for which unusual 8-O-6'-structures were proposed have been reassigned to the conventional 8-O-4'-structures (erythro and threo-guaiacylglycerol-β- coniferyl ether), respectively. Thus far, there is no evidence for the existence of 8-O-6'-neolignans in nature.
- Li, Shiming,Lundquist, Knut,Wallis, Adrian F. A.
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p. 2125 - 2128
(2007/10/03)
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