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Dienes
Kinds of Dienes Terms modified by Dienes Selected AbstractsHybrid Organic-Inorganic Materials Derived from a Monosilylated Hoveyda-type Ligand as Recyclable Diene and Enyne Metathesis CatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2007Xavier Elias Abstract The synthesis of a monosilylated Hoveyda-type monomer is described as well as the preparation of several organic-inorganic hybrid materials derived from it by sol-gel processes and by anchoring to commercial silica gel and MCM-41. The resulting materials were treated with first and/or second generation Grubbs' catalyst to generate Hoveyda,Grubbs' type alkylidene ruthenium complexes covalently bonded to the silica matrix. These materials are efficient recyclable catalysts for the ring-closing metathesis reaction of dienes and enynes, even for the formation of tri- and tetrasubstituted olefins. [source] Asymmetric Cyclopropanation of Alkenes with Dimethyl Diazomalonate Catalyzed by Chiral Diene,Rhodium Complexes,ANGEWANDTE CHEMIE, Issue 40 2010Dr. Takahiro Nishimura Mit Dreizahn zum Dreiring: Ein Rhodiumkomplex mit einem chiralen dreizähnigen Dienliganden (1; siehe Schema) erwies sich als Katalysator der intermolekularen asymmetrischen Cyclopropanierung von Alkenen mit Dimethyldiazomalonat unter Bildung von 1,1-Cyclopropandiestern in guten Ausbeuten und mit hohen Enantioselektivitäten. [source] Rhodium-Catalyzed Asymmetric Conjugate Addition of Organoboronic Acids to Nitroalkenes Using Chiral Bicyclo[3.3.0] Diene Ligands,ANGEWANDTE CHEMIE, Issue 33 2010Zhi-Qian Wang Nichts geht über Diene: In der Titelreaktion mit anspruchsvollen Nitroalkenen ohne ,-Substituenten als Substraten und unter ArB(OH)2/KHF2 -Bedingungen waren chirale Bicyclo[3.3.0]-Diene die besten Liganden. Np = Naphthyl. [source] 1,2,3-Trimethoxy-4-[(E)-2-phenylvinyl]benzene and (E,E)-1,4-bis(2,3,4-trimethoxyphenyl)buta-1,3-dieneACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009Jana Sopková-de Oliveira Santos The stilbene derivative 1,2,3-trimethoxy-4-[(E)-2-phenylvinyl]benzene, C17H18O3, (I), and its homocoupling co-product (E,E)-1,4-bis(2,3,4-trimethoxyphenyl)buta-1,3-diene, C22H26O6, (II), both have double bonds in trans conformations in their conjugated linkages. In the structure of stilbene (I), the aromatic rings deviate significantly from coplanarity, in contrast with coproduct (II), the core of which is rigorously planar. The deviation in stilbene (I) seems to be driven by intermolecular electrostatic interactions. Diene (II) sits on a crystallographic inversion centre, which bisects the conjugated linkage. [source] ChemInform Abstract: Spirocyclization of Six-Membered Cyclic N-Acyliminium Ions with a Conjugated Diene.CHEMINFORM, Issue 41 2009Hideki Abe Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Tandem Stille/Suzuki,Miyaura Coupling of a Hetero-Bis-Metalated Diene.CHEMINFORM, Issue 42 2005One-Pot Assembly of Polyene Systems., Rapid Abstract For Abstract see ChemInform Abstract in Full Text. [source] A Formal Total Synthesis of Eleutherobin Using the Ring-Closing Metathesis (RCM) Reaction of a Densely Functionalized Diene as the Key Step: Investigation of the Unusual Kinetically Controlled RCM StereochemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Damiano Castoldi Dr. Abstract Asymmetric oxyallylation reactions and ring-closing metathesis have been used to synthesize compound 3, a key advanced intermediate used in the total synthesis of eleutherobin reported by Danishefsky and co-workers. The aldehyde 6, which is readily prepared from commercially available R -(,)-carvone in six steps in 30,% overall yield on multigram quantities, was converted into the diene 5 utilizing two stereoselective titanium-mediated Hafner,Duthaler oxyallylation reactions. The reactions gave the desired products (8 and 12) in high yields (73 and 83,%, respectively) as single diastereoisomers, with the allylic alcohol already protected as the p -methoxyphenyl (PMP) ether, which previous work has demonstrated actually aids ring-closing metathesis compared to other protective groups and the corresponding free alcohol. Cyclization under forcing conditions, using Grubbs' second-generation catalyst 13, gave the ten-membered carbocycle (E)- 14 in 64,% yield. This result is in sharp contrast to similar, but less functionalized, dienes, which have all undergone cyclization to give the Z stereoisomers exclusively. A detailed investigation of this unusual cyclization stereochemistry by computational methods has shown that the E isomer of the ten-membered carbocycle is indeed less thermodynamically stable than the corresponding Z isomer. In fact, the selectivity is believed to be due to the dense functionality around the ruthenacyclobutane intermediate that favors the trans -ruthenacycle, which ultimately leads to the less stable E isomer of the ten-membered carbocycle under kinetic control. During the final synthetic manipulations the double bond of enedione (E)- 16 isomerized to the more thermodynamically stable enedione (Z)- 4, giving access to the advanced key-intermediate 3, which was spectroscopically and analytically identical to the data reported by Danishefsky and co-workers, and thereby completing the formal synthesis of eleutherobin. [source] Kinetic Studies Prove High Catalytic Activity of a Diene,Rhodium Complex in 1,4-Addition of Phenylboronic Acid to ,,,-Unsaturated KetonesCHEMISTRY - AN ASIAN JOURNAL, Issue 5 2006Asato Kina Abstract In the 1,4-addition of phenylboronic acid to ,,,-unsaturated ketones, [Rh(OH)(cod)]2 has a much higher catalytic activity than [Rh(OH)(binap)]2 (cod=1,5-cyclooctadiene, binap=2,2,-bis(diphenylphosphanyl)-1,1,-binaphthyl). Kinetic studies revealed that the rate-determining transmetalation step in the catalytic cycle has a large rate constant when [Rh(OH)(cod)]2 is used. [source] Undecylenic acid: A valuable renewable building block on route to Tyromycin,A derivativesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 9 2008Marijke Van der Steen Abstract A key intermediate for the synthesis of Tyromycin,A, a C-20 tetrachlorodicarboxylic acid, was produced in six steps starting with the dimerization of methyl 10-undecenoate which was obtained from a renewable resource, e.g. castor oil. The acyloin condensation product was then oxidized, transformed to the diene, followed by ozonization, chlorination and finally oxidation to the corresponding tetrachlorodicarboxylic acid. [source] Diels,Alder Reactions of Symmetrically 1,4-Disubstituted Dienes: Theoretical Study on the Influence of the Configuration of the Double Bonds on the Regio- and EndoselectivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2008Samira Baki Abstract It was experimentally shown in Diels-Alder reactions that symmetrically 1,4-disubstituted dienes exhibit high regio- and endoselectivity induced by the (E,Z) configuration of the double bonds. In order to understand the origin of this selectivity, the transition states associated with the reaction between a series of such dienes (R = OMe, CH3, NH2, F, CN) on substituted ethylene (R, = CO2Me, CN, F, OMe) were determined by DFT calculations. If the regioselectivity confirmed by a single-point MP2 calculation is predicted to be good in most cases, its direction remains difficult to predict; the R, group of the dienophile can orient itself toward either the (Z) or the (E) side of the diene. Neither primary nor secondary frontier orbital interactions appear to be able to rationalize these results. They are more likely explained by a delicate balance between steric and electrostatic interactions. This hypothesis is further supported by the calculated reactivity of the (E,E) and (Z,Z) corresponding dienes. In any case, a standard DFT calculation, confirmed by a single-point MP2 step, is likely to provide a reliable guideline for a synthesis strategy that allows the control of up to four stereogenic centres in a single reaction step.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Unexpected Tethering in the Synthesis of Methyl-Substituted Acetyl-1-oxaspiro[4.5]decanes: Novel Woody,Ambery Odorants with Improved Bioavailability,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2008Philip Kraft Abstract To study the olfactory properties of spirocyclic analogs of Iso Gamma (3) with improved water solubility and bioavailability, it was envisaged to spiroannulate 1-acetyl-1,2-dimethylcyclohexanone at the 4-position with a 3,3-dimethyltetrahydrofuran-2-yl moiety that would mimic the polarity of the double bond by its ether function. 3,3-Dimethyl-4-methylenehex-5-en-1-ol (9) was prepared by copper(I)-mediated 1,4-conjugate addition of the Grignard reagent of chloroprene (7) to 3-methylbut-2-enal with subsequent LAH reduction. However, the Diels,Alder reaction of diene 9 with (E)-3-methylpent-3-en-2-one in the presence of Me2AlCl unexpectedly provided exclusively the undesired meta adduct 10, as was discovered after cyclization to 11 with MeSO3H. The wrong selectivity was due to a tethering effect of the Lewis acid, and this could be evaded by changing the carbonyl function of the dienophile to a hydroxy group. Thereby the (5,R*,7,S*,8,S*)-configured 1-(4,,4,,7,,8,-tetramethyl-1,-oxaspiro[4.5]decan-7,/8,-yl)ethan-1-ones 11 and 14, as well as the like -configured 1-(4,,4,,7,-trimethyl-1,-oxaspiro[4.5]decan-7,/8,-yl)ethan-1-ones 16 and 19, were prepared selectively and studied for their odor characters, threshold values, and octanol/water partition coefficients. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Alternative Mechanistic Paths in the Hetero-Diels,Alder Reaction of ,-Oxothiones: A Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007Laura Legnani Abstract DFT calculations at the B3LYP/6-311+G(d,p) level for the C, H, and O atoms and at the 6-311+G(2df,p) level for the S atom were used to study the hetero-Diels,Alder reactions between several ,-oxothiones and ethylene or methyl vinyl ether (MVE). All the transition states and the intermediates along the reaction pathways, as well as the reaction products, were located. The reactions with ethylene are all concerted though asynchronous whereas in the reactions with MVE the electron-releasing character of the methoxy substituent lowers the energy barriers and enhances the asynchronicity and the charge transfer process to such an extent that the reaction may become unconcerted and exhibit a two-step mechanism with a zwitterionic intermediate derived from nucleophilic attack of electron-rich MVE to the sulfur atom of the strongly electrophilically activated ,-oxothiones. The reactions are also favored by the conjugation of the newly formed C=C bond. Moreover, the geometric features of the diene exert a nonnegligible role, as dienes that are planar or almost planar in their ground state show a lower energy barrier. Thus, both geometric and electronic features of the dienes as well as of the dienophiles play a significant role in the easiness of the reactions and in their mechanism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] An Efficient Route to 4/5/6 Polycyclic ,-LactamsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2004Nicolas Desroy Abstract The synthesis of 4/5/6 polycyclic ,-lactams by enyne metathesis and Diels,Alder reactions is described. Compared to the synthesis of 4/6/6 and 4/7/6 polycyclic ,-lactams previously reported by our laboratory, formation of the strained 4/5/6 compounds requires alternative reaction conditions. Indeed, the synthesis of the 4/5 bicyclic diene 12 was more difficult than those of the 4/6 (13) and 4/7 (14) dienes. The strain of the 4/5 system could be observed by NMR spectroscopy and molecular modelling. Moreover, the reactivity of 4/5 diene 12 towards Diels,Alder cycloaddition was also different from that of the 4/6 (13) and 4/7 (14) dienes. Cycloadditions with 4/5 diene 12 therefore had to be performed in lithium perchlorate/diethyl ether (LPDE) or in an ionic liquid in order to proceed in good yields with various dienophiles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] A C2 -Chiral Bis(amidinium) Catalyst for a Diels,Alder Reaction Constituting the Key Step of the Quinkert,Dane Estrone SynthesisEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2003Svetlana B. Tsogoeva Abstract A novel C2 -chiral bis(amidinium) salt 12 has been synthesised from 5-(tert -butyl)isophthalic acid. The hydrogen-bond-mediated association of dienophiles 3a and 3b with the chiral host molecule 12 accelerates the Diels,Alder reactions with diene 2 by more than three orders of magnitude. In addition, enantioselective formation of the desired adducts is observed under catalysis with 12. Good ratios of 4a(b) + ent - 4a(b)/5a(b) + ent - 5a(b) from 1:10 to 1:22 were found in all reactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Quantification of Grafting Densities Achieved via Modular "Grafting-to" Approaches onto Divinylbenzene MicrospheresADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Leena Nebhani Abstract The surface modification of divinylbenzene (DVB)-based microspheres is performed via a combination of reversible addition fragmentation chain transfer (RAFT) polymerization and rapid hetero-Diels,Alder (HDA) chemistry with the aim of quantifying the grafting densities achieved using this "grafting-to" method. Two variants of the RAFT-HDA concept are employed to achieve the functionalization of the microspheres. In the first approach, the microspheres are functionalized with a highly reactive diene, i.e., cyclopentadiene, and are subsequently reacted with polystyrene chains (number-averaged molecular weight, Mn,=,4200,g,mol,1; polydispersity index, PDI,=,1.12.) that carry a thiocarbonyl moiety functioning as a dienophile. The functionalization of the microspheres is achieved rapidly under ambient conditions, without the aid of an external catalyst. The surface grafting densities obtained are close to 1.2,×,1020 chains per gram of microspheres. In the second approach, the functionalization proceeds via the double bonds inherently available on the microspheres, which are reacted with poly(isobornyl acrylate) chains carrying a highly dienophilic thiocarbonyl functionality; two molecular weights (Mn,=,6000,g,mol,1, PDI,=,1.25; Mn,=,26,000,g,mol,1, PDI,=,1.26) are used. Due to the less reactive nature of the dienes in the second approach, functionalization is carried out at elevated temperatures (T,=,60,°C) yet in the absence of a catalyst. In this case the surface grafting density is close to 7,chains,nm,2 for Mn,=,6000,g,mol,1 and 4,chains,nm,2 for Mn,=,26,000,g,mol,1, or 2.82,×,1019 and 1.38,×,1019,chains g,1, respectively. The characterization of the microspheres at various functionalization stages is performed via elemental analysis for the quantification of the grafting densities and attenuated total reflectance (ATR) IR spectroscopy as well as confocal microscopy for the analysis of the surface chemistry. [source] Composition of the essential oil of flowers of Chloranthus spicatus (Thunb.) MakinoFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2006Hailemichael Tesso Abstract The composition of the essential oil of the flowers of Chloranthus spicatus (Thunb.) Makino (Chloranthaceae) was investigated using capillary GC-GC/MS, preparative GC and NMR techniques. Forty-seven compounds were identified either by comparing their retention indices and mass spectra with a library of authentic samples established under identical experimental conditions or, by isolating the compounds and deriving their structures by one- and two-dimensional NMR investigations. Thus, four minor components, viz. chloranthalactone A (0.5%), isogermafurenolide (0.7%), eudesma-4(15),7(11),9-trien-12-olide (0.5%), and 7, -hydroxyeudesm-4-en-6-one (3.3%), were isolated for the first time as constituents of the essential oil of the flowers of C. spicatus and their structures established. The major components of the oil include (Z)- , -ocimene (6.3%), allo-aromadendrene (6.2%), sarisane (2-allyl-4,5-methylenedioxyanisol, 4.2%) and selina-4(15),7(11)-diene (6.4%). Copyright © 2006 John Wiley & Sons, Ltd. [source] Reactions of 2-amino-3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene and 2-amino-3-cyano-4,7-diphenyl-5-methyl-4H -pyrano[2,3- c] pyrazole with phenylisocyanate, carbon disulfide, and thioureaHETEROATOM CHEMISTRY, Issue 1 2005Ahmed S. A. Youssef 2-Amino-3-cyano-4,5,6,7-tetrahydrobenzo[b]thiophene 1a or 2-amino-3-cyano-4,7-di- phenyl-5-methyl-4H -pyrano[2,3- c]pyrazole 2a reacted with phenylisocyanate in dry pyridine to give 2-(3-phenylureido)-3-cyanobenzo[b]thiophene 1b or 2-disubstituted amino-3-cyanopyranopyrazole 2b derivative. However, when 1a and 2a were refluxed with carbon disulfide in 10% ethanolic sodium hydroxide solution, they afforded the thieno[2,3- d]pyrimidin-2,4-dithione derivative 5 in the former case, 2,4-dicyano-1,3-bis(dithio carboxamino)cyclobuta-1,3- diene 6 and pyrazolopyranopyrido[2,3- d]pyrimidin- 2,4-dithione derivative 7 in the latter one. Treatment of 2a with thiourea in refluxing ethanol in the presence of potassium carbonate gave 2,2,-dithiobispyrimidine derivative 9 (major) in addition to pyranopyrazole derivative 10 and 2,2,-dithiobis ethoxypyrimidine derivative 11 in minor amounts. The structures of all products were evidenced by microanalytical and spectral data. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:6,11, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20070 [source] Effect of different precooking methods on chemical composition and lipid damage of silver carp (Hypophthalmichthys molitrix) muscleINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2010Mahmood Naseri Summary The influence of three precooking methods (steaming, oven-baking and microwave-cooking) on the chemical composition and lipid quality of silver carp fillets was evaluated. The changes in protein, fat and moisture were found to be significant for all the treatments (P , 0.05). The iron content in the samples subjected to steam-cooking increased; however, the other precooking methods did not change the mineral contents (P , 0.05). The free fatty acid content of the fillets did not change by the different precooking methods, while thiobarbituric acid (TBA) values increased for oven- and microwave-cooked fillets and remained constant in the steam-cooked samples. Conjugated diene and browning colour formation levels significantly increased in the oven-baked fillets. Oven-baking and microwave-cooking marginally affected the fatty acid composition of the silver carp. On comparing the raw and precooked fillets, steam-cooking was found to be the best precooking method on retaining nutritional constituents. [source] Use of Commercially Available Ruthenium Fischer-Type Carbenes for Ring-Closing Metathesis Reactions: Scope and Limitations of an in situ Activation ProcedureADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Debra Abstract An evaluation of two commercially available Fischer-type ruthenium carbenes in a range of ring-closing diene and enyne metathesis reactions has been carried out. A method to activate such catalysts for ring-closing reactions is presented. [source] Stereoselectivity in the Rhodium-Catalysed Reductions of Non-Conjugated DienesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Bao Nguyen Abstract The stereochemical course of rhodium-catalysed addition of hydrogen and catecholborane to bicyclo[2.2.1]heptadiene, and of hydrogen to a range of cyclic dienes has been analysed. For hydroboration, the overall catalytic reaction possesses exo -selectivity, but the initial step is endo -selective. For hydrogenation (deuteration), the first step may occur with either exo- or endo- selectivity, depending on the structure of the diene. This enables a distinction to be made between pathways involving prior dissociation of the diene, and direct addition to the complexed diene without full dissociation. The relative ease of hydrogenation of the first and second double bonds varies markedly with reactant structure, and also depends on the choice of catalyst ligands. For dicyclopentadiene, hydrogenation of the cyclopentene double bond is accompanied by rapid alkene isomerisation, as revealed by deuterium addition. The asymmetric hydrogenation of acyclic skipped meso -dienes is reported, demonstrating control of relative rates of the two sequential steps, with ees of up to 53% after the first reduction. [source] Structural determination of ethylene-propylene-diene rubber (EPDM) containing high degree of controlled long-chain branchingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009Susanta Mitra Abstract This work highlights an attempt to characterize the degree and nature of long-chain branching (LCB) in an unknown sample of ethylene-propylene-diene rubber (EPDM). Two EPDM rubbers selected for this study were comparable in comonomer compositions but significantly different with respect to molar mass and the presence of LCB. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were used for different characterization techniques. 1H-NMR, and 13C-NMR were used for assessing the comonomer ratios and LCB. Size exclusion chromatography (SEC) equipped with triple detector system was used to determine the molar mass (both absolute and relative) and polydispersity index (PDI). Presence of branching was also detected using sec-viscometry. Rheological analysis has also been used for characterizing LCB. Finally, on the basis of the experimental findings and the available theories, an attempt was made to identify the chemical nature and degree of LCB. This study reveals the possibility of detailed characterization of molecular architecture of EPDM containing LCB by comparing with an essentially linear EPDM in light of an existing theory. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] The existence of secondary orbital interactionsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2007Chaitanya S. Wannere Abstract B3LYP/6-311+G** (and MP2/6-311+G**) computations, performed for a series of Diels-Alder (DA) reactions, confirm that the endo transition states (TS) and the related Cope-TSs are favored energetically over the respective exo -TSs. Likewise, the computed magnetic properties (nucleus-independent chemical shifts and magnetic susceptibililties) of the endo - (as well as the Cope) TS's reveal their greater electron delocalization and greater aromaticity than the exo -TS's. However, Woodward and Hoffmann's original example is an exception: their endo -TS model, involving the DA reaction of a syn - with an anti -butadiene (BD), actually is disfavored energetically over the corresponding exo -TS; magnetic criteria also do not indicate the existence of SOI delocalization in either case. Instead, a strong energetic preference for endo -TSs due to SOI is found when both BDs are in the syn conformations. This is in accord with Alder and Stein's rule of "maximum accumulation of double bonds:" both the dienophile and the diene should have syn conformations. Plots along the IRC's show that the magnetic properties typically are most strongly exalted close to the energetic TS. Because of SOI, all the points along the endo reaction coordinates are more diatropic than along the corresponding exo pathways. We find weak SOI effects to be operative in the endo -TSs involved in the cycloadditions of cyclic alkenes, cyclopropene, aziridine, cyclobutene, and cyclopentene, with cyclopentadiene. While the endo -TSs are only slightly lower in energy than the respective exo -TSs, the magnetic properties of the endo -TS's are significantly exalted over those for the exo -TS's and the Natural Bond Orbitals indicate small stabilizing interactions between the methylene cycloalkene hydrogen orbitals (and lone pairs in case of aziridine) with ,-character and the diene , MOs. © 2006 Wiley Periodicals, Inc. J Comput Chem 2007 [source] Carotenoid lutein protects rats from paracetamol-, carbon tetrachloride- and ethanol-induced hepatic damageJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 8 2010Edakkadath R. Sindhu Abstract Objectives, Carotenoids are a class of natural fat-soluble pigments that are found in many fruits and vegetables. Consumption of a diet rich in carotenoids has been epidemiologically correlated with a lower risk for several diseases. In the present study the carotenoid lutein (3,3,-dihydroxy- ,,, -carotene) was evaluated for its hepatoprotective activity in rats. Methods, Paracetamol, 20% ethanol and carbon tetrachloride were used to induce liver toxicity. Key findings, Levels of serum glutamate oxaloacetate transaminase, serum glutamate pyruvate transaminase and alkaline phosphatases, which were increased in the serum, were found to be significantly reduced by the treatment of lutein in a dose-dependent manner, indicating that lutein may reduce the hepatotoxicity induced by these agents. Serum bilirubin was also significantly lower in lutein-treated groups compared with control. Increased lipid peroxidation, conjugated diene and hydroperoxides in the liver tissue produced by the administration of paracetamol were found to be reduced in the lutein-treated groups. Levels of antioxidant enzymes, like superoxide dismutase, catalase, glutathione peroxidase and glutathione, were found to be increased in lutein-treated groups compared with control group during alcohol- and CCl4 -induced liver toxicity. Hydroxyproline, which is an indicator of fibrosis in liver tissue, was high in the ethanol-treated control group. Hydroxyproline levels were decreased by simultaneous lutein administration. Conclusions, Histopathological evidence confirmed the protection offered by lutein from the tissue damage caused by hepatotoxins. The hepatoprotective action may be due to lutein's ability to scavenge reactive oxygen radicals. [source] Abnormal alterations in the metabolic patterns of patients on valproate therapyJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 7 2002U. Kreher Four cases of abnormal metabolic patterns which were obtained from three infantile patients and one adult on valproate (valproic acid; 2-n-propyl-pentanoic acid) therapy are reported. Serum levels of valproate and 15 metabolites were measured by gas chromatography/mass spectrometry. A mentally retarded, 11-month-old boy developed an extremely altered metabolic profile after having been treated with valproate polytherapy for 3 months. The altered pattern included strongly elevated serum levels of the 4-ene as well as of the x-/x 1-metabolites, with the b-metabolites (2-ene; 2,3,-diene) being diminished. Two samples obtained previously had shown a common pattern. The infant died 3 weeks after the last sample had been taken. Two boys of the same age showed similar but less intense deviations in their metabolic profiles at the onset of valproate therapy. Within a few weeks they approached, in a step-wise fashion, the average pattern common for children under 3 years of age. The striking alterations were paralleled by the metabolic profiles of an adult patient who suffered from intrahepatic metastasis and renal insufficiency. From the close resemblance of the abnormal metabolic patterns it was concluded that liver dysfunction results in alteration of the whole metabolic system. Regular inspection of the entire profile of an individual might help to recognize conspicuous alterations in time to avoid severe side effects. [source] Melatonin inhibits oxidative modification of low-density lipoprotein particles in normolipidemic post-menopausal womenJOURNAL OF PINEAL RESEARCH, Issue 3 2000Akihiko Wakatsuki In this study, we investigated the short-term effect of melatonin on the susceptibility of low-density lipoprotein (LDL) to oxidation in normolipidemic post-menopausal women. Fifteen post-menopausal women received 6.0 mg melatonin daily for 2 wk. Blood samples were obtained before and after the treatment and the plasma levels of total cholesterol, total triglyceride, high-density lipoprotein (HDL)-cholesterol, LDL-cholesterol, LDL-triglyceride, and LDL-apolipoprotein B were determined. LDL oxidation was performed by incubation with copper ions and was analyzed by monitoring the kinetics of conjugated diene formation and measuring the concentration of thiobarbituric-acid-reactive substances (TBARS). LDL-apolipoprotein B derivatization was analyzed by measuring trinitrobenzene sulfonic acid (TNBS) reactivity. Melatonin treatment significantly increased the plasma triglyceride levels (P<0.05), but did not significantly alter the plasma levels of total cholesterol, HDL-cholesterol, or LDL-lipids. The kinetics analysis of conjugated diene production revealed that melatonin treatment significantly prolonged the lag time of conjugated diene formation (from 64.71±11.89 to 70.15±10.52 min, P<0.05). The oxidation rate and the amount of conjugated diene, however, did not change significantly. The TBARS concentration was significantly reduced by melatonin treatment (from 49.31±7.57 to 38.69±23.90 nM/mg LDL, P<0.05). Furthermore, melatonin treatment significantly reduced the copper-induced decrease of TNBS reactivity (from 79.43±6.19 to 86.50±9.07% at 1 hr and from 71.03±6.74 to 76.31±4.99% at 2 hr, P<0.05). These results indicate that melatonin treatment may reduce LDL susceptibility to oxidative modification in normolipidemic post-menopausal women. [source] Ferrocenyl-functionalized long chain branched polydienesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2009Frederik Wurm Abstract A convenient two-step approach for the synthesis of ferrocenyl-functionalized long chain branched polydienes, based on both butadiene and isoprene, respectively, is presented. Classical living anionic polymerization was used to synthesize different ABn type poly(diene) macromonomers with moderate molecular weights between 1700 and 3200 g/mol and narrow polydispersity. Quantitative end-capping with chlorodimethylsilane resulted in the desired ABn macromonomer structures. In the ensuing Pt-catalyzed hydrosilylation polyaddition, branched, functionalized polydienes were obtained by a concurrent ABn + AR type of copolymerization with mono- and difunctional ferrocenyl silanes (fcSiMe2H or fc2SiMeH). Molecular weights of the branched polymers were in the range of 10,000 to 44,000 g/mol (SEC/MALLS). Because of the large number of functional end groups, high loading with ferrocene units up to 63 wt % of ferrocene was achieved. Detailed studies showed full conversion of the functional silanes and incorporation into the branched polymer. Further studies using DSC, TGA, and cyclovoltammetry (CV) measurements have been performed. Electrochemical studies demonstrated different electrochemical properties for fcSiMe2 - and fc2SiMe-units. The CVs of polymers modified with diferrocenylsilane units exhibit the pattern of communicating ferrocenyl sites with two distinct, separate oxidation waves. The polymers were also deposited on an electrode surface and the electrodes investigated via CV, showing formation of electroactive films with promising results for the use of the materials in biosensors. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2518,2529, 2009 [source] Synthesis and Fourier transform Raman spectroscopic study of diene-terminated polystyrene oligomersJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2005N. J. Ward Abstract Polystyrene oligomers capped with a known number of butadiene or isoprene units were synthesized by ,living' anionic polymerization in cyclohexane. The FT-Raman spectra of these compounds show small but significant differences in ,(CC) wavenumber position depending on whether just a single unit or several units of the diene are present at the chain end. However, if the butadiene experiments are repeated under polar-modified conditions, so that 1,2- rather than 1,4-addition takes place, the ,(CC) Raman band position is found to be independent of the number of ,out-of-chain' vinyl double bonds which are present. This conclusion is explained in terms of the mass change on diene addition to the polymer chains. Application of the method for the quantitation of polymer chain-end diene termination is proposed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Branching and Crosslinking in Coordination TerpolymerizationsMACROMOLECULAR REACTION ENGINEERING, Issue 4 2007Rolando C. S. Dias Abstract A general kinetic method, based upon population balances of generating functions, is applied to the prediction of the microstructure and molecular size of non-linear terpolymers obtained through the coordination polymerization of two monovinyl monomers and a non-conjugated diene. A rather complex kinetic scheme involving crosslinking and long-chain branching is considered. It is shown that even in these conditions it is possible to carry out the prediction of molecular size and mass distributions, sequence size distributions, and z -average mean-square radius of gyration of the polymers. The influence of some kinetic parameters on the properties of the products is studied, considering a homogeneous operation in a semi-batch reactor. The used simulation method is able to predict these properties before and after gelation whenever it occurs. [source] Structure determination of new steroids from Abutilon pakistanicum by NMR techniquesMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2008Munawar Hussain Abstract Two new steroids provisionally named as pakisteroid-A (1) and pakisteroid-B (2) have been isolated in crystalline form from Abutilon pakistanicum. Their structures have been assigned as 3- O -,- D -glucopyranosyl-stigmasta-5,11(12)-diene (1) and 24,-ethylcholesta-5, 9(11), 22E-trien-3,-benzoate (2), respectively through extensive NMR studies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Artichoke leaf extract reduces oxidative stress and lipoprotein dyshomeostasis in rats fed on high cholesterol dietPHYTOTHERAPY RESEARCH, Issue 4 2010Z. Küskü-Kiraz Abstract Hypercholesterolemia and lipid peroxidation play complementary role in atherosclerosis. Artichoke leaf extract (ALE) is rich in natural antioxidants and has a cholesterol-reducing effect. However, there is no study investigating the effect of ALE on lipid levels and lipid peroxidation in experimental hypercholesterolemic conditions. Rats were fed on 4% (w/w) cholesterol and 1% (w/w) cholic acid supplemented diet for 1 month. ALE (1.5,g/kg/day) was given by gavage during the last 2 weeks. Serum lipid composition, malondialdehyde (MDA) and diene conjugate (DC) levels and plasma antioxidant activity (AOA) were measured. In addition, endogenous DC and copper-induced MDA levels were determined in apo B-containing lipoproteins (LDL+VLDL fraction). Serum cholesterol and triglyceride levels and the ratio of cholesterol to HDL-cholesterol decreased due to ALE treatment in rats fed on HC diet. Significant decreases in serum MDA and DC levels and increases in plasma AOA were detected in serum in ALE-treated hypercholesterolemic rats. Endogenous DC and copper-induced MDA levels were also lower in LDL+VLDL fraction due to ALE-treatment in hypercholesterolemic rats. Our results indicate that ALE may be useful for the prevention of hypercholesterolemia-induced pro-oxidant state in LDL+VLDL fraction and the reduction of increased serum cholesterol and triglyceride levels. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||||||||