cas 6053-02-7, 3,4-dihydroxystyrene | Articles data

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Monitoring hydroxycinnamic acid decarboxylation by lactic acid bacteria using high-throughput UV-Vis spectroscopy
Hydroxycinnamic acid (HCA) decarboxylation by lactic acid bacteria (LAB) results in the production of 4-vinylplenols with great impact on the sensorial characteristics of foods. The determination of LAB decarboxylating capabilities is key for optimal strain selection for food production. The activity of LAB strains from the Ohio State University-Parker Endowed Chair (OSU-PECh) collection potentially capable of synthesizing phenolic acid decarboxylase was evaluated after incubation with HCAs for 36 h at 32 °C. A high-throughput method for monitoring HCAs decarboxylation was developed based on hypsochromic shifts at pH 1.0. Out of 22 strains evaluated, only Enterococcus mundtii, Lactobacillus plantarum and Pediococcus pentosaceus were capable of decarboxylating all p-coumaric, caffeic and ferulic acids. Other strains only decarboxylated p-coumaric and caffeic acid (6), only p-coumaric acid (2) or only caffeic acid (1), while 10 strains did not decarboxylate any HCA. p-Coumaric acid had the highest conversion efficiency, followed by caffeic acid and lastly ferulic acid. Results were confirmed by HPLC-DAD-ESI-MS analyses, showing the conversion of HCAs into their 4-vinylphenol derivatives. This work can help improve the sensory characteristics of HCA-rich foods where fermentation with LAB was used during processing.
García-Cano, Israel,Giusti, M. Monica,Jiménez-Flores, Rafael,Miyagusuku-Cruzado, Gonzalo,Rocha-Mendoza, Diana
(2020/08/24)

Phenolic Bis-styrylbenzo[ c]-1,2,5-thiadiazoles as Probes for Fluorescence Microscopy Mapping of Aβ Plaque Heterogeneity
A fluorescent bis-styryl-benzothiadiazole (BTD) with carboxylic acid functional groups (X-34/Congo red analogue) showed lower binding affinity toward Aβ1-42 and Aβ1-40 fibrils than its neutral analogue. Hence, variable patterns of neutral OH-substituted bis-styryl-BTDs were generated. All bis-styryl-BTDs showed higher binding affinity to Aβ1-42 fibrils than to Aβ1-40 fibrils. The para-OH on the phenyl rings was beneficial for binding affinity while a meta-OH decreased the affinity. Differential staining of transgenic mouse Aβ amyloid plaque cores compared to peripheral coronas using neutral compared to anionic bis-styryl ligands indicate differential recognition of amyloid polymorphs. Hyperspectral imaging of transgenic mouse Aβ plaque stained with uncharged para-hydroxyl substituted bis-styryl-BTD implicated differences in binding site polarity of polymorphic amyloid plaque. Most properties of the corresponding bis-styryl-BTD were retained with a rigid alkyne linker rendering a probe insensitive to cis-trans isomerization. These new BTD-based ligands are promising probes for spectral imaging of different Aβ fibril polymorphs.
Zhang, Jun,Konsmo, Audun,Sandberg, Alexander,Wu, Xiongyu,Nystr?m, Sofie,Obermüller, Ulrike,Wegenast-Braun, Bettina M.,Konradsson, Peter,Lindgren, Mikael,Hammarstr?m, Per
p. 2038 - 2048
(2019/02/26)

Bio-based vinylphenol family: Synthesis via decarboxylation of naturally occurring cinnamic acids and living radical polymerization for functionalized polystyrenes
A series of bio-based vinylphenols or hydroxystyrenes is prepared by simple decarboxylation of various naturally occurring cinnamic acids such as o-, m-, and p-coumaric; caffeic; ferulic; and sinapinic acids, which possess hydroxy groups and other substituents at different positions on the aromatic ring. After protection of the phenolic moieties with trialkylsilyl groups, reversible addition–fragmentation chain-transfer polymerization is accomplished with cumyl dithiobenzoate to afford various bio-based hydroxyl-protected polystyrenes with controlled molecular weights and narrow molecular weight distributions. Subsequent deprotection of the silyl groups under mild conditions results in a series of well-defined functionalized polystyrenes possessing different numbers (mono-, di-, tri-) of hydroxy groups at different positions (o, m, p). The obtained functionalized polystyrenes show unique thermal properties depending on the substituents, and those with phenol and catechol groups serve as reducing agents for silver ions.
Takeshima, Hisaaki,Satoh, Kotaro,Kamigaito, Masami
(2019/08/20)

Method for synthesizing hydroxystyrene compound by one-pot process
The invention relates to a method for synthesizing a hydroxystyrene compound by one-pot process. The method comprises the following steps of under the condition of normal pressure or decompression, enabling hydroxyl-substituted benzaldehyde, malonic acid or malonic acid derivative, an alkaline catalyst and a polymerization inhibitor to react for a first preset time in a first organic solvent at the first temperature suitable for the reflux of the first organic solvent, so as to obtain a first reaction mixture; heating the reaction system to a second temperature, and reacting for a second reaction time, so as to obtain a second reaction mixture; distilling the second reaction mixture to remove solvent, so as to obtain the hydroxystyrene compound. The method has the beneficial effects that the reaction temperature for the synthesizing of the hydroxystyrene compound is mild, and the yield rate of a final product is high.
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(2018/10/24)

Preparation method of 3,4-diacetoxystyrene
The invention relates to a preparation method of 3,4-diacetoxystyrene. The method comprises the steps of allowing 3,4-dihydroxy benzaldehyde and malonic acid to react in the presence of at least one organic solvent and a catalyst at 60-70 DEG C to generate a first reaction mixture containing 3,4-dihydroxy cinnamic acid, heating up to 80-90 DEG C to allow the first reaction mixture to continue reaction to generate a second reaction mixture containing 3,4-dyhydroxy styrene, allowing 3,4-dyhydroxy styrene to react with an acetylation reagent to generate a third reaction mixture containing 3,4-diacetoxystyrene, and purifying the third reaction mixture to form 3,4-diacetoxystyrene. The invention further provides a preparation method of an acetylation derivative of styrene. The method has the benefits that raw materials for preparation are easy to obtain; the cost is low; a synthesis condition is mild; a technology is simple and convenient; a post-treatment procedure is quick; and industrialization is easy to achieve.
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(2018/07/06)

METHOD FOR THE SYNTHESIS AND PRODUCTION OF ALKENYL COMPOUND
PROBLEM TO BE SOLVED: To provide a method for producing an efficient alkenyl compound conveniently and inexpensively. SOLUTION: A first compound represented by formula (1) reacts with a second compound represented by formula (3), in the presence of amino acid, in solvent containing amine, in a range of 50-200°C, to produce an alkenyl compound represented by formula (A) [where R1 is hydrogen or an optionally substituted C1-C30 alkyl group, R2 is a carboxyl group or the like, R3 and R4 are hydrogen, an optionally substituted C1-C30 alkyl group or the like]. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPOandINPIT
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(2018/09/20)

Analysis of protein-phenolic compound modifications using electrochemistry coupled to mass spectrometry
In the last decade, electrochemical oxidation coupled with mass spectrometry has been successfully used for the analysis of metabolic studies. The application focused in this study was to investigate the redox potential of different phenolic compounds such as the very prominent chlorogenic acid. Further, EC/ESI-MS was used as preparation technique for analyzing adduct formation between electrochemically oxidized phenolic compounds and food proteins, e.g., alpha-lactalbumin or peptides derived from a tryptic digestion. In the first step of this approach, two reactant solutions are combined and mixed: one contains the solution of the digested protein, and the other contains the phenolic compound of interest, which was, prior to the mixing process, electrochemically transformed to several oxidation products using a boron-doped diamond working electrode. As a result, a Michael-type addition led to covalent binding of the activated phenolic compounds to reactive protein/peptide side chains. In a follow-up approach, the reaction mix was further separated chromatographically and finally detected using ESI-HRMS. Compound-specific, electrochemical oxidation of phenolic acids was performed successfully, and various oxidation and reaction products with proteins/peptides were observed. Further optimization of the reaction (conditions) is required, as well as structural elucidation concerning the final adducts, which can be phenolic compound oligomers, but even more interestingly, quite complex mixtures of proteins and oxidation products.
Kallinich, Constanze,Schefer, Simone,Rohn, Sascha
(2018/02/07)

Terminal Alkenes from Acrylic Acid Derivatives via Non-Oxidative Enzymatic Decarboxylation by Ferulic Acid Decarboxylases
Fungal ferulic acid decarboxylases (FDCs) belong to the UbiD-family of enzymes and catalyse the reversible (de)carboxylation of cinnamic acid derivatives through the use of a prenylated flavin cofactor. The latter is synthesised by the flavin prenyltransferase UbiX. Herein, we demonstrate the applicability of FDC/UbiX expressing cells for both isolated enzyme and whole-cell biocatalysis. FDCs exhibit high activity with total turnover numbers (TTN) of up to 55000 and turnover frequency (TOF) of up to 370 min?1. Co-solvent compatibility studies revealed FDC's tolerance to some organic solvents up 20 % v/v. Using the in-vitro (de)carboxylase activity of holo-FDC as well as whole-cell biocatalysts, we performed a substrate profiling study of three FDCs, providing insights into structural determinants of activity. FDCs display broad substrate tolerance towards a wide range of acrylic acid derivatives bearing (hetero)cyclic or olefinic substituents at C3 affording conversions of up to >99 %. The synthetic utility of FDCs was demonstrated by a preparative-scale decarboxylation.
Aleku, Godwin A.,Prause, Christoph,Bradshaw-Allen, Ruth T.,Plasch, Katharina,Glueck, Silvia M.,Bailey, Samuel S.,Payne, Karl A. P.,Parker, David A.,Faber, Kurt,Leys, David
p. 3736 - 3745
(2018/08/03)

CSJ acting as a versatile highly efficient greener resource for organic transformations
Simple, new, greener and efficient alternatives to the existing protocols have been developed for the reduction of aromatic aldehydes to their corresponding alcohols, decarboxylation of substituted benzoic acids (C6-C1) and substituted cinnamic acids (C6-C3) with a hydroxyl group at the para position with respect to the acid group to corresponding phenolic compounds and vinyl phenols respectively by using a natural feedstock, cucumber juice (CSJ), which acts as a greener solvent system, performing a substrate-selective reaction. Additionally, the hydrolysis of the acetyl as well as the benzoyl group of aromatic compounds has been carried out to afford excellent yield by CSJ.
Maity, Himadri Sekhar,Misra, Kaushik,Mahata, Tanushree,Nag, Ahindra
p. 24446 - 24450
(2016/03/15)

Activation of the Nrf2 cell defense pathway by ancient foods: Disease prevention by important molecules and microbes lost from the modern western diet
The Nrf2 (NFE2L2) cell defense pathway protects against oxidative stress and disorders including cancer and neurodegeneration. Although activated modestly by oxidative stress alone, robust activation of the Nrf2 defense mechanism requires the additional presence of co-factors that facilitate electron exchange. Various molecules exhibit this co-factor function, including sulforaphane from cruciferous vegetables. However, natural co-factors that are potent and widely available from dietary sources have not been identified previously. The objectives of this study were to investigate support of the Nrf2 cell defense pathway by the alkyl catechols: 4-methylcatechol, 4-vinylcatechol, and 4-ethylcatechol. These small electrochemicals are naturally available from numerous sources but have not received attention. Findings reported here illustrate that these compounds are indeed potent co-factors for activation of the Nrf2 pathway both in vitro and in vivo. Each strongly supports expression of Nrf2 target genes in a variety of human cell types; and, in addition, 4-ethylcatechol is orally active in mice. Furthermore, findings reported here identify important and previously unrecognized sources of these compounds, arising from biotransformation of common plant compounds by lactobacilli that express phenolic acid decarboxylase. Thus, for example, Lactobacillus plantarum, Lactobacillus brevis, and Lactobacillus collinoides, which are consumed from a diet rich in traditionally fermented foods and beverages, convert common phenolic acids found in fruits and vegetables to 4-vinylcatechol and/or 4-ethylcatechol. In addition, all of the alkyl catechols are found in wood smoke that was used widely for food preservation. Thus, the potentially numerous sources of alkyl catechols in traditional foods suggest that these co-factors were common in ancient diets. However, with radical changes in food preservation, alkyl catechols have been lost from modern foods. The absence of alkyl catechols from the modern Western diet suggests serious negative consequences for Nrf2 cell defense, resulting in reduced protection against multiple chronic diseases associated with oxidative stress.
Senger, Donald R.,Li, Dan,Jaminet, Shou-Ching,Cao, Shugeng
(2016/03/19)

A One-Pot Cascade Reaction Combining an Encapsulated Decarboxylase with a Metathesis Catalyst for the Synthesis of Bio-Based Antioxidants
The combination of enzymes with traditional chemical catalysts unifies the high selectivity of the former with the versatility of the latter. A major challenge of this approach is the difference in the optimal reaction conditions for each catalyst type. In this work, we combined a cofactor-free decarboxylase with a ruthenium metathesis catalyst to produce high-value antioxidants from bio-based precursors. As suitable ruthenium catalysts did not show satisfactory activity under aqueous conditions, the reaction required the use of an organic solvent, which in turn significantly reduced enzyme activity. Upon encapsulation of the decarboxylase in a cryogel, the decarboxylation could be conducted in an organic solvent, and the recovery of the enzyme after the reaction was facilitated. After an intermediate drying step, the subsequent metathesis in pure organic solvent proved to be straightforward. The synthetic utility of the cascade was demonstrated by the synthesis of the antioxidant 4,4′-dihydroxystilbene in an overall yield of 90 %.
Gómez Baraibar, álvaro,Reichert, Dennis,Mügge, Carolin,Seger, Svenja,Gr?ger, Harald,Kourist, Robert
supporting information
p. 14823 - 14827
(2016/11/23)

Photo-degradation of trans-caffeic acid in aqueous solution and influence of complexation by metal ions
The photo-degradation of metal complexes of caffeic acid was compared to the photo-degradation of free caffeic acid by using UV-vis spectroscopy and HPLC-ESI-mass spectrometry. This article reports first the determination of the products that are formed from the photo-degradation of trans-caffeic acid in aqueous solution and the investigation of the mechanism by a kinetic approach. The good fit between the model and the experimental concentration profiles confirms the photo-isomerization route of the molecule to cis-caffeic acid which then undergoes a cyclization to form the esculetin photo-product. In addition, it reveals, for the first time, another route of major importance leading to the product vinylcatechol. The presence of oxygen leads to an increase of the photo-isomerization rate. Then we report that metallic cations such as Al(III), Pb(II) and Cu(II) can influence the rate and mechanism of caffeic acid photodegradation. Al(III) ions slow down the photo-degradation whereas Pb(II) and Cu(II) ions have a promoter effect on the production of esculetin. In all cases, the photo-isomerization is reduced by the presence of metal ions and the formation of vinylcatechol does not occur.
Le Person, Anna?g,Lacoste, Anne-Sophie,Cornard, Jean-Paul
p. 10 - 19
(2013/10/22)

Synthesis of the antiepileptic (R)-Stiripentol by a combination of lipase catalyzed resolution and alkene metathesis
The enantiopure (ee >99%) antiepileptic (R)-(+)-Stiripentol has been stereoselectively synthesized via cross metathesis of 5-vinylbenzo[d][1,3] dioxole 1 and (R)-(+)-4,4-dimethylpent-1-en-3-ol (R)-(+)-2. A novel one-pot two-step pathway for the synthesis of 5-vinylbenzo[d][1,3]dioxole 1 starting from 3,4-dihydroxycinnamic acid has been introduced. A lipase catalyzed kinetic resolution access to enantiopure (R)-(+)-4,4-dimethylpent-1-en-3-ol (R)-(+)-2 (ee >99%) has also been developed.
El-Behairy, Mohammed Farrag,Sundby, Eirik
p. 285 - 289
(2013/05/21)

Resveratrol derived butyrylcholinesterase inhibitors
Novel polyhydroxylated (E)-stilbenes were synthesized by Mizoroki-Heck reactions and tested for their ability to inhibit the enzymes acetyl- and butyrylcholinesterase. Several of them are good inhibitors of butyrylcholinesterase; one of them carrying an extra fluorine substituent is a 94-fold stronger inhibitor of butyrylcholinesterase than of acetylcholinesterase. Novel polyhydroxylated (E)-stilbenes synthesized by Mizoroki-Heck reactions were tested for their ability to inhibit the enzymes acetyl- and butyrylcholinesterase. Several of them were found to be good inhibitors of butyrylcholinesterase. One of them carrying an extra fluorine substituent is a 94-fold stronger inhibitor of butyrylcholinesterase than of acetylcholinesterase.
Csuk, Rene,Albert, Sabrina,Kluge, Ralph,Stroehl, Dieter
p. 499 - 503
(2013/07/26)

Synthesis and radical scavenging activities of resveratrol analogs
Highly substituted polyhydroxylated (E)-stilbenes were synthesized by Mizoroki-Heck reactions and tested for their ability to act as radical scavenger. One of the 56 stilbenes included in this study and investigated in DPPH assays gave an SC50 value of 11.0 μM, hence exhibiting an about 9.3 times higher activity than resveratrol. As shown in a photometric SRB assay using mouse NiH 3T3 fibroblasts, this compound is not cytotoxic up to concentrations of 30 μM. Highly substituted polyhydroxylated (E)-stilbenes synthesized by Mizoroki-Heck reactions were tested for their ability to act as radical scavengers. One of the 56 stilbenes included exhibited about 9.3 times higher activity than resveratrol. At concentrations 30 μM, this compound was not cytotoxic.
Csuk, Rene,Albert, Sabrina,Siewert, Bianka
p. 504 - 510
(2013/07/26)

New greener alternatives for bioreduction of aromatic aldehydes and decarboxylation of aromatic acids using juice of fruits
Cocos nucifera L. and Borassus flabellifer L. juices act as bio catalytic system for the reduction of aromatic aldehydes to alcohols and selective decarboxylation of substituted cinnamic acid to styrene and substituted benzoic acid to polyphenolic compound. Both juices exhibit good activity when aromatic aldehydes and aromatic acids contain electron-donating groups at specific positions. Moreover, C. nucifera juice exhibits good result for the reduction and decarboxylation properties than B. flabellifer juice under the same reaction condition.
Misra, Kaushik,Maity, Himadri Sekhar,Chanda, Subhankar,Nag, Ahindra
experimental part
p. 92 - 95
(2012/09/22)

Synthesis and antimicrobial activity of (E) stilbene derivatives
Plants use multiple defence mechanisms comprising both constitutive and inducible barriers to prevent entering of phytopathogenic micro-organisms. In many plant species one of the most efficient responses to combat attacking microbes is the rapid synthesis of antimicrobial low molecular weight phytoalexins, for example, resveratrol, 3,5,4′-trihydroxystilbene (1). Resveratrol and its natural derivatives, however, display only moderate antimicrobial effects. Nevertheless, resveratrol may be a useful lead structure for the chemical synthesis of antimicrobials. In this study, several series of stilbenes have been synthesized, starting from the aldehydes using Wittig reactions to access the corresponding styrenes that were subjected to Mizoroki-Heck reactions to yield the stilbenes in good yields. The stilbenes were tested in an agar diffusion assay against several bacteria and fungi. For some of these compounds the inhibiting zones for bacteria and fungi were comparable with those of the antibiotics tetracycline, streptomycin, ampicillin, or kanamycin, directed against prokaryotes, and nourseothricin or hygromycin controlling fungi, respectively.
Albert, Sabrina,Horbach, Ralf,Deising, Holger B.,Siewert, Bianka,Csuk, René
supporting information; experimental part
p. 5155 - 5166
(2011/10/04)

Antioxidant properties of 4-vinyl derivatives of hydroxycinnamic acids
The compounds 4-vinylphenol (4-VP), 4-vinylguaiacol (4-VG), 4-vinylsyringol (4-VS) and 4-vinylcatechol (4-VC) were prepared by thermal decarboxylation of the corresponding hydroxycinnamic acids p-coumaric, ferulic, sinapic and caffeic acid, respectively. For confirmation of the synthesised products LC-MS followed by NMR analysis was used. To evaluate their antioxidant potential, their reducing power and efficiency in scavenging the alkylperoxyl radical generated in an emulsion system, the 2,2-diphenyl-1-picrylhydrazyl (DPPH ·) radical and the superoxide anion radical (O2-) were determined. All tested 4-vinyl derivatives revealed weaker antioxidant activity in a homogeneous polar medium than the corresponding phenolic acids. In the emulsion system the activity for 4-vinyl derivatives was higher than was the activity of their corresponding phenolic acids, with 4-VG as the most active among the tested phenolic compounds.
Terpinc, Petra,Polak, Toma?,?egatin, Nata?a,Hanzlowsky, Andrej,Ulrih, Nata?a Poklar,Abramovi?, Helena
experimental part
p. 62 - 69
(2012/03/22)

New urinary metabolites formed from ring-oxidized metabolic intermediates of styrene
The urine from mice exposed to styrene vapors (600 and 1200 mg/m 3, 6 h) was analyzed for ring-oxidized metabolites of styrene. To facilitate the identification of metabolites in urine, the following potential metabolites were prepared: 2-, 3-, and 4-vinylphenol (2-, 3-, and 4-VP), 4-vinylpyrocatechol, and 2-, 3-, and 4-vinylphenylmercapturic acid (2-, 3-, and 4-VPMA). For the analysis of vinylphenols β-glucuronidase-treated urine was extracted and derivatized with acetanhydride/triethylamine before injection into GC/MS. Three isomers, 2-, 3-, and 4-VP, were found in the exposed urine using authentic standards. Additionally, three novel minor urinary metabolites, arylmercapturic acids 2-, 3-, and 4-VPMA, were identified by LC-ESI-MS 2 by comparison with authentic standards. Excretion of the most abundant isomer, 4-VPMA, amounted to 535 ± 47 nmol/kg and 984 ± 78 nmol/kg, representing approximately 0.047 and 0.043% of the absorbed dose for the exposure levels of 600 and 1200 mg/m3, respectively. The ratio of 2-VPMA, 3-VPMA, and 4-VPMA was approximately 2:1:6. In model reactions of styrene 3,4-oxide (3,4-STO) with N-acetylcysteine in aqueous solutions and of its methyl ester in methanol, 4-vinylphenol was always the main product, while 3-vinylphenol has never been detected. No mercapturic acid was found in the reaction of 3,4-STO with N-acetylcysteine in aqueous solution at pH 7.4 or 9.7, but a small amount of 4-VPMA methyl ester was detected by LC-ESI-MS after the reaction of 3,4-STO with N-acetylcysteine methyl ester. In contrast, no mercapturic acid was found in the reaction of 3,4-STO with N-acetylcysteine in aqueous solution at pH 7.4 or 9.7. These findings indicate a capability of 3,4-STO to react with cellular thiol groups despite its rapid isomerization to vinylphenol in an aqueous environment. Moreover, the in vivo formation of 2- and 3-isomers of both VP and VPMA, neither of which was formed from 3,4-STO in vitro, strongly suggests that another arene oxide, styrene 2,3-oxide, might be a minor metabolic intermediate of styrene.
Linhart, Igor,Mraz, Jaroslav,Scharff, Jan,Krouzelka, Jan,Duskova, Sarka,Nohova, Hana,Vodickova, L'udmila
body text
p. 251 - 257
(2011/02/16)

Characterization of the p-coumaric acid decarboxylase from Lactobacillus plantarum CECT 748T
It was previously reported that cell cultures from Lactobacillus plantarum CECT 748T were able to decarboxylate phenolic acids, such as p-coumaric, m-coumaric, caffeic, ferulic, gallic, and protocatechuic acid. The p-coumaric acid decarboxylase (PDC) from this strain has been overexpressed and purified. This PDC differs at its C-terminal end when compared to the previously reported PDC from L. plantarum LPCHL2. Because the C-terminal region of PDC is involved in enzymatic activity, especially in substrate activity, it was decided to biochemically characterize the PDC from L. plantarum CECT 748T. Contrarily to L. plantarum LPCHL2 PDC, the recombinant PDC from L. plantarum CECT 748T is a heat-labile enzyme, showing optimal activity at 22°C. This PDC is able to decarboxylate exclusively the hydroxycinnamic acids p-coumaric, caffeic, and ferulic acids. Kinetic analysis showed that the enzyme has a 14-fold higher KM value for p-coumaric and caffeic acids than for ferulic acid. PDC catalyzes the formation of the corresponding 4-vinyl derivatives (vinylphenol and vinylguaiacol) from p-coumaric and ferulic acids, respectively, which are valuable food additives that have been approved as flavoring agents. The biochemical characteristics showed by L. plantarum PDC should be taken into account for its potential use in the food-processing industry.
Rodriguez, Hector,Landete, Jose Maria,Curiel, Jose Antonio,De Las Rivas, Blanca,Mancheno, Jose Miguel,Munoz, Rosario
p. 3068 - 3072
(2008/09/20)

One-pot two-step synthesis of 4-vinylphenols from 4-hydroxy substituted benzaldehydes under microwave irradiation: a new perspective on the classical Knoevenagel-Doebner reaction
The classical Knoevenagel-Doebner reaction is reinvestigated wherein the direct synthesis of substituted 4-vinylphenols instead of the expected 4-hydroxycinnamic acids is described. The condensation reaction is performed on 4-hydroxy substituted benzaldehydes and malonic acid with a mixture of acetic acid-piperidine as condensing agent under focused microwave irradiation. The occurrence of simultaneous condensation-double decarboxylation without the use of any decarboxylating agent is a new finding, the reaction being facilitated solely by the hydroxy substituent and microwave irradiation effect.
Sinha, Arun K.,Sharma, Anuj,Joshi, Bhupendra P.
p. 960 - 965
(2007/10/03)

Obtaining 4-vinylphenols by decarboxylation of natural 4-hydroxycinnamic acids under microwave irradiation
4-Vinylphenols, useful compounds for industrial applications, were obtained by decarboxylation of 4-hydroxycinnamic acids under microwave irradiation in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as base and basic aluminum oxide as solid support. The reactions were fast (15-30 min). The selective extraction of the final products with ethyl acetate avoids chromatographic purifications. The conversions are quantitative and the yields are satisfactory. Only the unstable 4-vinylcatechol was obtained in moderate yield. This procedure was successfully extended to a natural sample of ferulic acid extracted from wheat bran to get the corresponding 4-vinylguaiacol, a FEMA GRAS (Flavor and Extract Manufacturer's Association; General Regarded as Safe) approved flavoring agent.
Bernini, Roberta,Mincione, Enrico,Barontini, Maurizio,Provenzano, Gianfranco,Setti, Leonardo
p. 9663 - 9667
(2008/02/11)

Pathway leading to the formation of anthocyanin-vinylphenol adducts and related pigments in red wines
On the basis of observations from Vitis vinifera cv. Pinotage wines and experiments performed in model wine medium, a new chemical pathway responsible for the formation of anthocyanin-vinylphenol adducts in red wines is described. Until now, these pigments have been considered to be reaction products of anthocyanins and vinylphenols, the latter being generated during fermentation by enzymatic decarboxylation of the respective cinnamic acids. The mechanism of the novel pathway, involving intact hydroxycinnamic acid and anthocyanin, is explained. Only cinnamic acids with electrondonating substituents on the aromatic ring, such as coumaric acid, ferulic acid, caffeic acid, and sinapic acid, undergo this conversion, as they stabilize an intermediately formed carbenium ion. Decarboxylation and oxidation of the pyran moieties are the final steps in the generation of the corresponding 4-vinylphenol, 4-vinylguaiacol, 4-vinylcatechol, and 4-vinylsyringol adducts of anthocyanins in red wine.
Schwarz, Michael,Wabnitz, Tobias C.,Winterhalter, Peter
p. 3682 - 3687
(2007/10/03)