- Highly Selective Syntheses of Coniferyl and Sinapyl Alcohols
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(E)-Isomers of coniferyl and sinapyl alcohols were readily and cleanly prepared in excellent yields from comercially available coniferaldehyde and sinapaldehyde by sodium triacetoxyborohydride reduction in ethyl acetate.No 1,4-reduction products, always produced in prior methods, could be detected. - Keywords: coniferyl alcohol; sinapyl alcohol; monolignol; lignin; triacetoxyborohydride; dihydroconiferyl alcohol; coniferaldehyde; sinapaldehyde; regiospecific reduction
- Lu, Fachuang,Ralph, John
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- EPR imaging of sinapyl alcohol and its application to the study of plant cell wall lignification
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In bioimaging, bioorthogonal chemistry is most often used to visualize chemical reporters by fluorescence in their native environment. Herein, we show that TEMPO-based probes can be ligated to monolignol reporters by Diels-Alder chemistry in plant cell wa
- Simon, Clémence,Lion, Cédric,Ahouari, Hania,Vezin, Hervé,Hawkins, Simon,Biot, Christophe
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- Simplified preparation of coniferyl and sinapyl alcohols
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Coniferyl and sinapyl alcohols were prepared from commercially available coniferaldehyde and sinapaldehyde using borohydride exchange resin in methanol. This reduction is highly regioselective and exceptionally simple, making these valuable monolignols readily available to researchers lacking synthetic chemistry expertise.
- Kim, Hoon,Ralph, John
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- Total Syntheses and Anti-inflammatory Activities of Syringin and Its Natural Analogues
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Syringin (1), a natural bioactive glucoside isolated from the root of Acanthopanax senticosus (Rupr. Maxim.) Harms, possesses significant anti-inflammatory activity. In this study, we have accomplished the total syntheses of syringin (1), along with its natural analogues 2-12, from a common starting material, syringaldehyde (13), in 4-8 steps with an overall yields of 11.8-61.3%. The anti-inflammatory activities of these compounds were determined against NO production in the LPS-stimulated RAW264.7 cells. Among them, compounds 1-5, 7, and 9 exhibited different levels of anti-inflammatory activity.
- Dong, Hongbo,Du, Weihong,He, Yujiao,Shi, Zheng,Wang, Yingying,Wu, Min
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p. 2866 - 2874
(2021/11/12)
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- Non-plasmonic Ni nanoparticles catalyzed visible light selective hydrogenolysis of aryl ethers in lignin under mild conditions
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Light-driven catalysis on catalytically versatile group VIII metals, which has been widely used in thermal catalysis, holds great potential in solar-to-chemical conversion. We report a novel photocatalysis process for the selective hydrogenolysis of aryl ethers in lignin on a heterogeneous catalyst of non-precious Ni nanoparticles supported on ZrO2. Three aryl ether bonds in lignin were successfully cleaved under mild conditions with excellent conversion and good to excellent selectivity under visible light irradiation. We also used solar irradiation to demonstrate a significant reduction in the total energy consumption. The light irradiation excited interband transitions in Ni nanoparticles and the resultant energetic electrons enhanced the activity of reductive cleavage of the aryl ethers. Its application potential was illustrated by the depolymerization of dealkaline lignin to give a total monomer yield of 9.84 wt% with vanillin, guaiacol, and apocynin as the three major products.
- Baeyens, Jan,Li, Peifeng,Ouyang, Yixuan,Sarina, Sarina,Su, Haijia,Xiao, Gang,Zhao, Yilin,Zhu, Huai-Yong
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supporting information
p. 7780 - 7789
(2021/10/12)
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- First total syntheses of two natural glycosides
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Isosyringinoside (1) and 3-(O-β-D-glucopyranosyl)-α-(O-β-D-glucopyranosyl)-4-hydroxy phenylethanol (2), the natural bioactive compounds contained unique structures, were first totally synthesized using easily available materials in short convenient routes with overall yields of 20.2% and 27.0%, respectively. An efficient total synthesis of 1 was developed in six steps, which contained two key steps of highly regioselective glycosylation without any selective protection steps. The seven-step synthesis of 2 involved two steps of regioselective glycosylations using BF3–O(C2H5)2 and TMSOTf as catalysts, respectively.
- Dong, Hongbo,Du, Weihong,Yao, Zhongquan,Wu, Min,Luo, Hongbing,He, Yujiao,Cao, Shenghua
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- COMPOUNDS HAVING HEPATIAL DISEASE EFFECTIVE
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The invention discloses a compound with a hepatopathy curative effect, and the compound is a compound shown as a general formula (I), an optical isomer or pharmaceutically acceptable salt thereof, canbe applied to treatment or prevention of hepatopathy, particularly to drugs for treating or preventing fatty liver, liver fibrosis or liver cirrhosis, and has a good application prospect.
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- Profiling of the formation of lignin-derived monomers and dimers from: Eucalyptus alkali lignin
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Lignin is a renewable and the most abundant aromatic source that can be used for extensive chemicals and materials. Although approximately 50 million tons of lignin are produced annually as a by-product of the pulp and paper industry, it is currently underutilized. It is important to know the structural features of technical lignin when considering its application. In this work, we have demonstrated the formation of low-molecular-weight constituents from hardwood (Eucalyptus) lignin, which produces much more low-molecular-weight constituents than softwood (spruce) lignin, after a chemical pulping process, and analyzed the micromolecular compositions in the alkali lignin after fractionation by dichloromethane (DCM) extraction. By applying analytical methods (gel-permeation chromatography, 2D NMR and GC-MS) with the aid of evidence from authenticated compounds, a great treasure trove of lignin-derived phenolic compounds from Eucalyptus alkali lignin were disclosed. Except for some common monomeric products, as many as 15 new lignin-derived monomers and dimers including syringaglycerol, diarylmethane, 1,2-diarylethanes, 1,2-diarylethenes, (arylvinyl ether)-linked arylglycerol dimers and isomeric syringaresinols were identified in the DCM-soluble fraction. Regarding the formation and evolution of the Cα-condensed β-aryl ether structure, a novel route that is potentially responsible for the high content of β-1 diarylethenes and diarylethanes in the lignin low-molecular-weight fraction, in addition to the β-1 (spirodienone) pathway, was proposed. This work not only provides novel insights into the chemical transformation of S-G lignin during the alkali pulping process, but also discovered lignin-derived phenolic monomers and dimers that can potentially be used as raw materials in the chemical or pharmaceutical industries. This journal is
- Hu, Zhenhua,Li, Suxiang,Lu, Fachuang,Shi, Lanlan,Wang, Chen,Yue, Fengxia,Zhang, Han,Zhao, Chengke
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supporting information
p. 7366 - 7375
(2020/11/18)
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- Improved Pd/Ru metal supported graphene oxide nano-catalysts for hydrodeoxygenation (HDO) of vanillyl alcohol, vanillin and lignin
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Pd and Ru nanoparticles supported on graphene oxide (GO) [Pd?GO and Ru?GO] and bimetallic [Pd/Ru?GO] were prepared and well characterized by XRD, FT-IR, EDS, TEM, XPS and ICP-AES analyses. The prepared nano-catalysts were tested for hydrodeoxygenation (HDO) of lignin monomer molecules-vanillyl alcohol and vanillin. In comparison with previously reported methods, Ru?GO and bimetallic Pd/Ru?GO catalysts showed high activity and selectivity, under milder conditions, at room temperature and 145 psi H2 pressure, for the formation of p-creosol, a value added product, as a potential future biofuel with antibacterial and anti-insecticidal properties. The multifold advantages of both these catalysts are in terms of reduced catalyst loading with a lower metal content and ambient temperture conditions resulting in higher conversion of the starting material. Furthermore, the efficacy of the developed methodology using Ru?GO and bimetallic Pd/Ru?GO catalysts under the optimized conditions was tested on the phenolic components of commercial lignin obtained by photo-catalytic fragmentation using TiO2, to obtain a mixture after HDO which contained vanillyl alcohol and p-creosol among others, as indicated by HPLC-MS analysis.
- Arora, Shalini,Gupta, Neeraj,Singh, Vasundhara
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supporting information
p. 2018 - 2027
(2020/04/07)
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- Microbial Production of Natural and Unnatural Monolignols with Escherichia coli
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Phenylpropanoids and phenylpropanoid-derived plant polyphenols find numerous applications in the food and pharmaceutical industries. In recent years, several microbial platform organisms have been engineered towards producing such compounds. However, for the most part, microbial (poly)phenol production is inspired by nature, so naturally occurring compounds have predominantly been produced to date. Here we have taken advantage of the promiscuity of the enzymes involved in phenylpropanoid synthesis and exploited the versatility of an engineered Escherichia coli strain harboring a synthetic monolignol pathway to convert supplemented natural and unnatural phenylpropenoic acids into their corresponding monolignols. The performed biotransformations showed that this strain is able to catalyze the stepwise reduction of chemically interesting unnatural phenylpropenoic acids such as 3,4,5-trimethoxycinnamic acid, 5-bromoferulic acid, 2-nitroferulic acid, and a “bicyclic” p-coumaric acid derivative, in addition to six naturally occurring phenylpropenoic acids.
- Aschenbrenner, Jennifer,Marx, Patrick,Pietruszka, J?rg,Marienhagen, Jan
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p. 949 - 954
(2019/02/26)
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- Comparative transcriptomics analysis for gene mining and identification of a cinnamyl alcohol dehydrogenase involved in methyleugenol biosynthesis from asarum sieboldii miq
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Asarum sieboldii Miq., one of the three original plants of TCM ASARI RADIX ET RHIZOMA, is a perennial herb distributed in central and eastern China, the Korean Peninsula, and Japan. Methyleugenol has been considered as the most important constituent of Asarum volatile oil, meanwhile asarinin is also employed as the quality control standard of ASARI RADIX ET RHIZOMA in Chinese Pharmacopeia. They both have shown wide range of biological activities. However, little was known about genes involved in biosynthesis pathways of either methyleugenol or asarinin in Asarum plants. In the present study, we performed de novo transcriptome analysis of plant tissues (e.g., roots, rhizomes, and leaves) at different developmental stages. The sequence assembly resulted in 311,597 transcripts from these plant materials, among which 925 transcripts participated in ‘secondary metabolism’ with particularly up to 20.22% of them falling into phenylpropanoid biosynthesis pathway. The corresponding enzymes belong to seven families potentially encoding phenylalanine ammonia-lyase (PAL), trans-cinnamate 4-monooxygenase (C4H), p-coumarate 3-hydroxylase (C3H), caffeoyl-CoA O-methyltransferase (CCoAOMT), cinnamoyl-CoA reductase (CCR), cinnamyl alcohol dehydrogenase (CAD), and eugenol synthase (EGS). Moreover, 5 unigenes of DIR (dirigent protein) and 11 unigenes of CYP719A (719A subfamily of cytochrome P450 oxygenases) were speculated to be involved in asarinin pathway. Of the 15 candidate CADs, four unigenes that possessed high FPKM (fragments per transcript kilobase per million fragments mapped) value in roots were cloned and characterized. Only the recombinant AsCAD5 protein efficiently converted p-coumaryl, coniferyl, and sinapyl aldehydes to their corresponding alcohols, which are key intermediates employed not only in biosynthesis of lignin but also in that of methyleugenol and asarinin. qRT-PCR revealed that AsCAD5 had a high expression level in roots at three developmental stages. Our study will provide insight into the potential application of molecular breeding and metabolic engineering for improving the quality of TCM ASARI RADIX ET RHIZOMA.
- Liu, Jinjie,Xu, Chong,Zhang, Honglei,Liu, Fawang,Ma, Dongming,Liu, Zhong
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- Microwave-Assisted Synthesis of Phenylpropanoids and Coumarins: Total Synthesis of Osthol
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Herein we describe a one-pot microwave-assisted method for the synthesis of cinnamic acid and coumarin derivatives. The synthesis begins with an aldehyde synthon, and the chosen reaction conditions determine whether a cinnamic acid or coumarin derivative is formed. A regioselective Claisen rearrangement was also efficiently incorporated into the synthetic sequence to further increase the complexity of the product. Notably, this approach provides high product yields and selectivities without the need of a phenol protecting group.
- Konrádová, Daniela,Kozubíková, Hana,Dole?al, Karel,Pospí?il, Ji?í
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p. 5204 - 5213
(2017/09/29)
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- First total synthesis of a new phenylpropanoid glycoside: natural cytotoxic compound from Cirsium japonicum
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Phenylpropanoid glycoside compound 1, the natural anti-tumor compound isolated from the erial parts of Cirsium japonicum, was first totally synthesized using easily available materials in short, convenient route with overall yield of 13.9%.
- Dong, Hong-Bo,Hou, Ming,Ma, Wen-Bo,Zhang, Jing-Xia,Li, Zhe-Yu,Luo, Hong-Bing,Tang, Ke-Hui,Cao, Sheng-Hua
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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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- Isolation of functionalized phenolic monomers through selective oxidation and CO bond cleavage of the β-O-4 linkages in Lignin
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Functionalized phenolic monomers have been generated and isolated from an organosolv lignin through a two-step depolymerization process. Chemoselective catalytic oxidation of β-O-4 linkages promoted by the DDQ/tBuONO/ O2 system was achieved in model compounds, including polymeric models and in real lignin. The oxidized β-O-4 linkages were then cleaved on reaction with zinc. Compared to many existing methods, this protocol, which can be achieved in one pot, is highly selective, giving rise to a simple mixture of products that can be readily purified to give pure compounds. The functionality present in these products makes them potentially valuable building blocks.
- Lancefield, Christopher S.,Ojo, O. Stephen,Tran, Fanny,Westwood, Nicholas J.
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p. 258 - 262
(2015/02/19)
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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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- In vitro analysis of the monolignol coupling mechanism using dehydrogenative polymerization in the presence of peroxidases and controlled feeding ratios of coniferyl and sinapyl alcohol
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In this study, dehydrogenative polymers (DHP) were synthesized in vitro through dehydrogenative polymerization using different ratios of coniferyl alcohol (CA) and sinapyl alcohol (SA) (10:0, 8:2, 6:4, 2:8, 0:10), in order to investigate the monolignol coupling mechanism in the presence of horseradish peroxidase (HRP), Coprinus cinereus peroxidase (CiP) or soybean peroxidase (SBP) with H2O2, respectively. The turnover capacities of HRP, CiP and SBP were also measured for coniferyl alcohol (CA) and sinapyl alcohol (SA), and CiP and SBP were found to have the highest turnover capacity for CA and SA, respectively. The yields of HRP-catalyzed DHP (DHP-H) and CiP-catalyzed DHP (DHP-C) were estimated between ca. 7% and 72% based on the original weights of CA/SA in these synthetic conditions. However, a much lower yield of SBP-catalyzed DHP (DHP-S) was produced compared to that of DHP-H and DHP-C. In general, the DHP yields gradually increased as the ratio of CA/SA increased. The average molecular weight of DHP-H also increased with increasing CA/SA ratios, while those of DHP-C and DHP-S were not influenced by the ratios of monolignols. The frequency of β-O-4 linkages in the DHPs decreased with increasing CA/SA ratios, indicating that the formation of β-O-4 linkages during DHP synthesis was influenced by peroxidase type.
- Moon, Sun-Joo,Kwon, Mi,Choi, Donha,Won, Keehoon,Kim, Yong Hwan,Choi, In-Gyu,Choi, Joon Weon
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- Growth inhibitory activities of oxyprenylated and non-prenylated naturally occurring phenylpropanoids in cancer cell lines
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A series of 25 selected oxyprenylated natural phenylpropanoids were synthesized, and their growth inhibitory activities were evaluated in vitro together with 14 other commercially available non-alkylated compounds belonging to the same chemical series. The compounds were tested on six human cancer cell lines using MTT colorimetric assays. The data reveal that of the six chemical groups (G) studied, coumarins (G1), cinnamic and benzoic acids (G2), chalcones (G3), acetophenones (G4), anthraquinones (G5), and cinnamaldehydes and cinnamyl alcohols (G6), G2-related compounds displayed the weakest growth inhibitory activities in vitro, whereas G5-related compounds displayed the highest activities. Quantitative videomicroscopy analyses were then carried out on human U373 glioblastoma cells, which are characterized by various levels of resistance to different pro-apoptotic stimuli. These analyses revealed that compounds 20 (4,2′,4′-trihydroxychalcone), and 30 and 31 (two cinnamaldehydes) were cytostatic and able to overcome the intrinsic resistance of U373 cancer cells to pro-apoptotic stimuli.
- Bruyre, Céline,Genovese, Salvatore,Lallemand, Benjamin,Ionescu-Motatu, Alexandra,Curini, Massimo,Kiss, Robert,Epifano, Francesco
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scheme or table
p. 4174 - 4179
(2011/08/06)
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- Insights into lignin primary structure and deconstruction from Arabidopsis thaliana COMT (caffeic acid O-methyl transferase) mutant Atomt1
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The Arabidopsis mutant Atomt1 lignin differs from native lignin in wild type plants, in terms of sinapyl (S) alcohol-derived substructures in fiber cell walls being substituted by 5-hydroxyconiferyl alcohol (5OHG)-derived moieties. During programmed lignin assembly, these engender formation of benzodioxane substructures due to intramolecular cyclization of their quinone methides that are transiently formed following 8-O-4′ radical-radical coupling. Thioacidolytic cleavage of the 8-O-4′ inter-unit linkages in the Atomt1 mutant, relative to the wild type, indicated that cleavable sinapyl (S) and coniferyl (G) alcohol-derived monomeric moieties were stoichiometrically reduced by a circa 2:1 ratio. Additionally, lignin degradative analysis resulted in release of a 5OHG-5OHG-G trimer from the Atomt1 mutant, which then underwent further cleavage. Significantly, the trimeric moiety released provides new insight into lignin primary structure: during polymer assembly, the first 5OHG moiety is linked via a C8-O-X inter-unit linkage, whereas subsequent addition of monomers apparently involves sequential addition of 5OHG and G moieties to the growing chain in a 2:1 overall stoichiometry. This quantification data thus provides further insight into how inter-unit linkage frequencies in native lignins are apparently conserved (or near conserved) during assembly in both instances, as well as providing additional impetus to resolve how the overall question of lignin macromolecular assembly is controlled in terms of both type of monomer addition and primary sequence.
- Moinuddin, Syed G. A.,Jourdes, Michael,Laskar, Dhrubojyoti D.,Ki, Chanyoung,Cardenas, Claudia L.,Kim, Kye-Won,Zhang, Dianzhong,Davin, Laurence B.,Lewis, Norman G.
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experimental part
p. 3928 - 3946
(2010/09/17)
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- A novel and efficient procedure for the preparation of allylic alcohols from α,β-unsaturated carboxylic esters using LiAlH4/BnCl
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A new and efficient method for the reduction of α,β-unsaturated carboxylic esters to allylic alcohols utilizing LiAlH4/BnCl is described. Various α,β-unsaturated esters, including the coumarins bearing α,β-unsaturated lactone skeleton, can be converted smoothly into their corresponding allylic alcohols in high yields under mild conditions with short reaction times.
- Wang, Xiaolong,Li, Xiaodong,Xue, Jijun,Zhao, Yuling,Zhang, Yumei
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experimental part
p. 413 - 415
(2009/05/11)
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- Biomimetic preparation of the racemic modifications of the stilbenolignan aiphanol and three congeners
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A chromatographically separable mixture of the racemic modification, (±)-1, of the stilbenolignan (-)-aiphanol and congeners (±)-2-4 has been generated by a silver(I)-mediated and potentially biomimetic oxidative coupling of piceatannol (5) with sinapic a
- Chand, Satish,Banwell, Martin G.
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p. 243 - 250
(2008/02/11)
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- Arabidopsis thaliana β-Glucosidases BGLU45 and BGLU46 hydrolyse monolignol glucosides
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In higher plants, β-glucosidases belonging to glycoside hydrolase (GH) Family 1 have been implicated in several fundamental processes including lignification. Phylogenetic analysis of Arabidopsis thaliana GH Family 1 has revealed that At1g61810 (BGLU45), At1g61820 (BGLU46), and At4g21760 (BGLU47) cluster with Pinus contorta coniferin β-glucosidase, leading to the hypothesis that their respective gene products may be involved in lignification by hydrolysing monolignol glucosides. To test this hypothesis, we cloned cDNAs encoding BGLU45 and BGLU46 and expressed them in Pichia pastoris. The recombinant enzymes were purified to apparent homogeneity by ammonium sulfate fractionation and hydrophobic interaction chromatography. Among natural substrates tested, BGLU45 exhibited narrow specificity toward the monolignol glucosides syringin (Km, 5.1 mM), coniferin (Km, 7 mM), and p-coumaryl glucoside, with relative hydrolytic rates of 100%, 87%, and 7%, respectively. BGLU46 exhibited broader substrate specificity, cleaving salicin (100%), p-coumaryl glucoside (71%; Km, 2.2 mM), phenyl-β-d-glucoside (62%), coniferin (8%), syringin (6%), and arbutin (6%). Both enzymes also hydrolysed p- and o-nitrophenyl-β-d-glucosides. Using RT-PCR, we showed that BGLU45 and BGLU46 are expressed strongly in organs that are major sites of lignin deposition. In inflorescence stems, both genes display increasing levels of expression from apex to base, matching the known increase in lignification. BGLU45, but not BGLU46, is expressed in siliques, whereas only BGLU46 is expressed in roots. Taken together with recently described monolignol glucosyltransferases [Lim et al., J. Biol. Chem. (2001) 276, 4344-4349], our enzymological and molecular data support the possibility of a monolignol glucoside/β-glucosidase system in Arabidopsis lignification.
- Escamilla-Trevino, Luis L.,Chen, Wei,Card, Marcella L.,Shih, Ming-Che,Cheng, Chi-Lien,Poulton, Jonathan E.
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p. 1651 - 1660
(2008/02/12)
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- Isolation and biomimetic synthesis of anti-inflammatory stilbenolignans from Gnetum cleistostachyum
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One new stilbenolignan, gnetucleistol F (1), and four known stilbenolignans, gnetofuran A (2), lehmbachol D (3), gnetifolin F (4) and gnetumontanin C (5) were isolated from the lianas of Gnetum cleistostachyum C. Y. CHENG (Gnetaceae). Their structures and relative configurations were determined by means of spectroscopic evidence. Compounds 1, 2, 3 and 4 were synthesized for the first time on the basis of their biogenetic pathway, and their possible biomimetical synthetic mechanisms were discussed. The pharmacological activities of all stilbenolignans have been tested. Among them, 1, 2, 3, 4 and 5 showed moderate inhibitory activities on TNF-α and 1 also showed potent inhibitory activity on malondialdehyde.
- Yao, Chun-Suo,Lin, Mao,Wang, Lin
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p. 1053 - 1057
(2007/10/03)
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- A mild synthesis of coumaryl, coniferyl, sinapyl aldehydes and alcohols
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Acetylconiferyl aldehyde is obtained from acetylvanillin by a Wittig reaction under phase-transfer conditions; basic hydrolysis gives coniferyl aldehyde, or after reduction with sodium borohydride affords coniferyl alcohol. This method is extended to the sinapyl and coumaryl series.
- Daubresse,Francesch,Mhamdi,Rolando
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p. 369 - 371
(2007/10/02)
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- A one-pot synthesis of coumaryl, coniferyl and sinapyl alcohol
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The side chain of 4-allylphenol can be easily deprotonated if the butyl-lithium/potassium tert-butoxide superbase is employed. Consecutive treatment with fluorodimethoxyboron and hydrogen peroxide affords directly 3-(4-hydroxy-phenyl)-2-propen-1-ol ('coumaryl alcohol'). In the same way, 4-allyl-2-methoxyphenol can be converted to coniferyl alcohol and 4-allyl-2,6-dimethoxyphenol to sinapyl alcohol.
- Rothen,Schlosser
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p. 2475 - 2476
(2007/10/02)
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- PHENOLIC COMPOUNDS FROM ROOTS OF URTICA DIOICA
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Root extracts from Urtica dioica were separated into several classes of compounds by extraction with organic solvents at different pH values.The phenolic fraction was analysed by GC-MS after trimethylsilylation.This procedure allowed the identification of 18 phenolic compounds as well as the detection of eight lignans.The occurrence of some of these substances in this plant was previously unknown.
- Kraus, Rupert,Spiteller, Gerhard
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p. 1653 - 1659
(2007/10/02)
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- Synthesis and Structural Elucidation of Coumarinolignans
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Coumarinolignans are a relatively new class of natural products combining a coumarin skeleton with a phenylpropene moiety.We describe here details of the first biomimetic syntheses of compounds in this series (1-16) utilizing both chemical and enzymatic approaches and the application of the selective INEPT nmr technique for unambiguous structure assignment.Chemical oxidation using silver oxide as an oxidizing agent typically produced two regioisomeric trans-substituted coumarinolignans.Enzymatic oxidation on the other hand normally gave rise to a single regioisomer.Almost all of the known natural coumarinolignans and several new compounds which may subsequently be obtained as natural products were synthesized.Three nmr strategies are described for the structure elucidation of the coumarinolignans, but only one of these techniques, the selective INEPT method, affords an unambiguous structure when only one regioisomer is present.Using this technique the structures and complete proton and carbon-13 chemical shift assignments of sixteen synthetic coumarinolignans were established.The described nmr strategy should prove useful for the unambiguous structure determination of all natural 2-aryl benzodioxanes, including the flavonolignans, the xanthonolignans and certain neolignans.
- Lin, Lee-Juian,Cordell, Geoffrey A.
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p. 3052 - 3080
(2007/10/02)
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- Synthesis and Reactivity of Vinyl Quinone Methides
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Vinyl quinone methides 4a and 4b were obtained in high yields by Ag2O oxidation of eugenol (3a) and of 2,6-dimethoxy-4-(2-propenyl)phenol (3b).Vinyl quinone methides (VQMs) reacted with alcohols, with phenols, and with acetic acid giving compounds 5 and 6.As the former rearranged to the latter in the reaction medium, the addition of the reported substrates to VQMs turned out to be wholly regioselective toward the formation of coniferyl and sinapyl derivatives 6.In contrast, addition of carbon nucleophiles (acetylacetone and EtNO2) to VQMs gave both compounds 7 and 8.By reaction of the acetates 6a and 6b (CR=CH3CO) with LiAlH4 it was possible to perform a novel synthesis of coniferyl and sinapyl alcohols (1a and 1b).Treatment of the same acetates with an aqueous solution of NaHCO3 reproduced VQMs 4, which by subsequent reduction with NaBH4, gave propenylphenols 2 and allylphenols 3.Formation of the latter compounds from coniferyl and sinapyl acetates via VQM is here proposed as a possible biosynthetic pathway.
- Zanarotti, Antonio
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p. 941 - 945
(2007/10/02)
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- NOUVELLE SYNTHESE DE PRECURSEURS PHENOLIQUES DES LIGNINES UTILISANT LES SELS D'IMINIUM DES ACIDES p-HYDROXY CINNAMIQUES
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4-Hydroxy cinnamic esters, thiolesters, aldehydes and alcohols, or related compounds, implied in the biosynthesis of lignins are easily synthesized in good yields from iminium salts of coumaric 1a, ferulic 1b and sinapic 1c acids.No prior protection of the phenol group is needed in this method.
- Duran, E.,Gorrichon, L.,Cazaux, L.,Tisnes, P.
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p. 2755 - 2758
(2007/10/02)
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- PREPARATION AND REACTIVITY OF 2,6-DIMETHOXY-4-ALLYLIDENE-2,5-CYCLOHEXADIEN-1-ONE (VINYL QUINONE METHIDE) A NOVEL SYNTHESIS OF SINAPYL ALCOHOL
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Title compound (3b), prepared in concentrated CHCl3 or benzene solution and spectroscopically characterized, is shown to be an useful intermediate for the synthesis of sinapyl alcohol (1b) and its derivatives.
- Zanarotti, A.
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p. 3815 - 3818
(2007/10/02)
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