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Selected AbstractsReactions of Allyl Alcohols of the Pinane Series and of Their Epoxides in the Presence of Montmorillonite ClayHELVETICA CHIMICA ACTA, Issue 2 2007Irina Abstract The reactivity of allyl alcohols of the pinane series and of their epoxides in the presence of montmorillonite clay in intra- and intermolecular reactions was studied. Mutual transformations of (+)- trans -pinocarveol ((+)- 2) and (,)-myrtenol ((,)- 3a) were major reactions of these compounds on askanite,bentonite clay (Schemes,1 and 2). However, the two reactions gave different isomerization products, indicating that the reactivity of the starting alcohol (+)- 2 or (,)- 3a was different from that of the same compound (+)- 2 or (,)- 3 formed in the course of the reactions. (,)- cis - and (+)- trans -Verbenol ((,)- 16 and (+)- 12, resp.), as well as (,)- cis -verbenol epoxide ((,)- 20) reacted with both aliphatic and aromatic aldehydes on askanite,bentonite clay giving various heterocyclic compounds (Schemes,4, 5 and 7); the reaction path depended on the structure of both the terpenoid and the aldehyde. [source] Perspectives on ecological risk assessment of chiral compoundsINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 3 2009Jacob K Stanley Abstract Enantiomers of chiral contaminants can significantly differ in environmental fate as well as in effects. Despite this fact, such differences are often ignored in regulation and in practice, injecting uncertainty into the estimation of risk of chiral compounds. We review the unique challenges posed by stereochemistry to the ecological risk assessment of chiral contaminants and existing regulatory guidance for chiral pharmaceuticals and pesticides in the United States. We identify the advantages of obtaining data on fate and effects of each individual enantiomer of chiral contaminants that are either distributed as or may end up as enantiomer mixtures in the environment due to enantiomerization. Because enantiomers of the same compound are highly likely to coexist in the environment with each other and can result in nonadditive effects, we recommend treatment of enantiomers as components of a mixture using widely accepted mixture models from achiral risk assessment. We further propose the enantiomer hazard ratio for retrospectively characterizing relative enantiomer risk and examine uncertainty factor magnitudes for effects analysis. [source] A comparison of a microfocus X-ray source and a conventional sealed tube for crystal structure determinationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2009Thomas Schulz Experiments are described in which a direct comparison was made between a conventional 2,kW water-cooled sealed-tube X-ray source and a 30,W air-cooled microfocus source with focusing multilayer optics, using the same goniometer, detector, radiation (Mo,K,), crystals and software. The beam characteristics of the two sources were analyzed and the quality of the resulting data sets compared. The Incoatec Microfocus Source (IµS) gave a narrow approximately Gaussian-shaped primary beam profile, whereas the Bruker AXS sealed-tube source, equipped with a graphite monochromator and a monocapillary collimator, had a broader beam with an approximate intensity plateau. Both sources were mounted on the same Bruker D8 goniometer with a SMART APEX II CCD detector and Bruker Kryoflex low-temperature device. Switching between sources simply required changing the software zero setting of the 2, circle and could be performed in a few minutes, so it was possible to use the same crystal for both sources without changing its temperature or orientation. A representative cross section of compounds (organic, organometallic and salt) with and without heavy atoms was investigated. For each compound, two data sets, one from a small and one from a large crystal, were collected using each source. In another experiment, the data quality was compared for crystals of the same compound that had been chosen so that they had dimensions similar to the width of the beam. The data were processed and the structures refined using standard Bruker and SHELX software. The experiments show that the IµS gives superior data for small crystals whereas the diffracted intensities were comparable for the large crystals. Appropriate scaling is particularly important for the IµS data. [source] Mercury CSD 2.0, new features for the visualization and investigation of crystal structuresJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2008Clare F. Macrae The program Mercury, developed by the Cambridge Crystallographic Data Centre, is designed primarily as a crystal structure visualization tool. A new module of functionality has been produced, called the Materials Module, which allows highly customizable searching of structural databases for intermolecular interaction motifs and packing patterns. This new module also includes the ability to perform packing similarity calculations between structures containing the same compound. In addition to the Materials Module, a range of further enhancements to Mercury has been added in this latest release, including void visualization and links to ConQuest, Mogul and IsoStar. [source] Limitations of amorphous content quantification by isothermal calorimetry using saturated salt solutions to control relative humidity: Alternative methodsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2010Nawel Khalef Abstract Despite the high sensitivity of isothermal calorimetry (IC), reported measurements of amorphous content by this technique show significant variability even for the same compound. An investigation into the reasons behind such variability is presented using amorphous lactose and salbutamol sulfate as model compounds. An analysis was carried out on the heat evolved as a result of the exchange of water vapor between the solid sample during crystallization and the saline solution reservoir. The use of saturated salt solutions as means of control of the vapor pressure of water within sealed ampoules bears inherent limitations that lead in turn to the variability associated with the IC technique. We present an alternative IC method, based on an open cell configuration that effectively addresses the limitations encountered with the sealed ampoule system. The proposed approach yields an integral whose value is proportional to the amorphous content in the sample, thus enabling reliable and consistent quantifications. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2080,2089, 2010 [source] Sex pheromones and trail-following pheromone in the basal termites Zootermopsis nevadensis (Hagen) and Z. angusticollis (Hagen) (Isoptera: Termopsidae: Termopsinae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010CHRISTIAN BORDEREAU In the context of an evolutionary study of the chemical communication in termites, sex pheromones and trail-following pheromones were investigated in two Termopsidae, Zootermopsis nevadensis and Z. angusticollis. In these species, in which the presence of sex-specific pheromones has been demonstrated previously, the chemical structure of the female sex pheromone has now been identified as (5E)-2,6,10-trimethylundeca-5,9-dienal and the male sex pheromone as (+)- or (,)- syn -4,6-dimethyldodecanal. The amount of sex pheromone was estimated at 5,10 ng per individual in females and 2,5 ng in males. Because these two sympatric species do not differ in their pheromonal chemical composition, reproductive isolation is probably mediated chiefly by differences in dispersal flight chronology. The trail-following pheromone was shown to be composed of the same compound as the male sex pheromone, that is syn -4,6-dimethyldodecanal. The compound syn -4,6-dimethyldodecanal was 10 times more active than the racemic (+/,)- syn + (+/,) -anti -4,6-dimethyldodecanal in eliciting trail-following. The amount of syn -4,6-dimethyldodecanal was estimated at 0.1,0.5 ng per pseudergate. Regarding the phylogenetic aspects, the nature of the female sex pheromone of Zootermopsis is structurally akin to the trail-following pheromone of Mastotermes darwiniensis of Mastotermitidae and Porotermes adamsoni and Stolotermes victoriensis of Termopsidae. Interestingly, the nature of the trail-following pheromone of the Termopsinae Zootermopsis is clearly different from that of the Porotermitinae P. adamsoni and the Stolotermitinae S. victoriensis, which mirrors recent molecular data on the paraphyly of Termopsidae. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 519,530. [source] In Situ Spectroscopic Characterization of Rectifying Molecular Monolayers Self-Assembled on GoldCHEMPHYSCHEM, Issue 15 2007Alberto Girlando Prof. Abstract We report visible, Raman, and infrared spectra of self-assembled monolayers (SAMs) formed by the donor-(,-bridge)-acceptor chromophore, Z -,-[N -(,-acetylthioalkyl)-4-quinolinium]-,-cyano-4-styryldicyanomethanide (CH3CO-S-CnH2n -Q3CNQ where n=8, 10), on gold-coated substrates. The data are compared with the spectra collected for the same compound in solution and in the solid state, and with those obtained for a Langmuir,Blodgett (LB) monolayer of C16H33 -Q3CNQ deposited on gold. Spectral analysis confirms that in solution, in the solid state and in the LB film the chromophore has a zwitterionic (D+ -,-A,) ground state. At variance with this well-known result, our data show that in SAMs deposited on gold the chromophore has a more neutral, quinoid ground state. We relate this difference to the different packing of the molecules in the two different films: in SAMs in fact the chromophores stand almost vertical with respect to the substrate, whereas in LB films they make an angle of about 45 degrees. The Q3CNQ molecule is a well-known molecular rectifier, and for SAMs we were able to check the direction of electron flow at forward bias on the same samples that have been characterized spectroscopically, shedding light on the rectification mechanism. [source] HPLC determinations of enantiomeric ratiosCHIRALITY, Issue 1 2007Peter Wipf Abstract Evaporative light-scattering detection (ELSD) is widely applied in the HPLC analysis of organic compounds lacking a UV chromophore. However, this detection method is generally unsuitable for determination of enantiomeric ratios (er). The er calculated from a UV trace and an ELS trace of the same compound differs significantly. Because of the nonlinear concentration response of the ELS detector, a compound with an er of 95:5 appears to be enantiomerically pure by ELS detection. It is possible to obtain a calibration curve and to calculate a correction factor, but this procedure is time consuming and therefore not very practical for routine analyses. In contrast, a charged aerosol detector allows a very accurate determination of the enantiomeric ratios. Like the ELS detection, the CA detection is independent of the chromophore properties of the substrate. Therefore, we recommend the use of CA instead of ELS detection for determination of the enantiomeric ratios of non-UV active compounds. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] Aroma-active compounds of American, French, Hungarian and Russian oak woods, studied by GC,MS and GC,OFLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2008M. Consuelo Díaz-Maroto Abstract Gas chromatography,mass spectrometry (GC,MS) and gas chromatography,olfactometry (GC,O) were used to study aroma-active compounds in extracts of American, French, Hungarian and Russian oak woods. Compounds that presented high odour intensities for the non-toasted oak woods were guaiacol, hexanal, trans -2-nonenal, trans -oak lactone, cis- oak lactone, eugenol, vanillin and trans- isoeugenol, whilst the same compounds, in addition to furfural, 4-methylguaiacol and cis -isoeugenol, proved important in the toasted oaks. Like the oak lactones, cis- and trans- isoeugenol presented woody/oak odours, particularly in the toasted samples. For Hungarian and Russian samples, both characterized by their lower content of oak lactones, trans- and cis- isoeugenol presented higher odour intensities. For this reason, samples of low oak lactone concentrations, such as Hungarian and Russian oak woods, but also containing isoeugenols, can impart woody/oak odours to wines. Copyright © 2008 John Wiley & Sons, Ltd. [source] Volatile constituents of different organs of Psoralea bituminosa L.FLAVOUR AND FRAGRANCE JOURNAL, Issue 2 2004Alessandra Bertoli Abstract The essential oil and SPME samples of the leaves, ,owers and seeds of Psoralea bituminosa L. were analysed by GC and GC,MS. We have investigated also the presence of monoterpene or aliphatic alcohol glucosides. The essential oils showed both qualitative and quantitative differences. The main constituents of the leaf and the ,ower essential oils were caryophyllene (23% and 18%, respectively), , -farnesene (15% and 6%, respectively), and germacrene D (24% and 18%, respectively). Signi,cant amounts (7%) of the same compounds were also directed in the seed essential oil, but tricyclene (11%) and , -pinene (50%) were the most important constituents of this oil. The volatile fractions of remaining leaf aqueous extracts after treatment with , -glucosidase revealed qualitative differences in comparison with the composition of the corresponding essential oils, and high levels of 3-hexen-1-ol (37%) and 1-octen-3-ol (27%) were observed. The SPME analysis of the fresh leaves, ,owers and seeds of P. bituminosa con,rmed the qualitative composition of the volatile oils, even if we detected signi,cative differences in the percentage ratio between monoterpenes and sesquiterpenes in comparison with the oils, where sesquiterpenes were the main components. In fact the variation of the monoterpenes, tricyclene, , -pinene and camphene between the leaf oil and the corresponding headspace sample was remarkable: tricyclene increased from 0.1% to 8%, , -pinene from 0.1% to 16% and camphene from 0.3% to 10% in the SPME samples. Copyright © 2004 John Wiley & Sons, Ltd. [source] Characterization of Fish Sauce Aroma-Impact Compounds Using GC-MS, SPME-Osme-GCO, and Stevens' Power Law ExponentsJOURNAL OF FOOD SCIENCE, Issue 4 2008A.J. Pham ABSTRACT:, The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) coupled with Stevens' Power Law. Compounds were separated using GCMS and GCO and were identified with the mass spectral database, aroma perceived at the sniffing port, retention indices, and verification of compounds by authentic standards in the GCMS and GCO. Aromas that were isolated and present in all 4 fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), and sweet and cotton candy (benzaldehyde). All fish sauces contained the same aromas as determined by GCO and GCMS (verified using authentic standard compounds), but the odor intensity associated with each compound or group of compounds was variable for different fish sauce samples. Stevens' Power Law exponents were also determined using this analytical technique, but exponents were not consistent for the same compounds that were found in all fish sauces. Stevens' Power Law exponents ranged from 0.14 to 0.37, 0.24 to 0.34, 0.09 to 0.21, and 0.10 to 0.35 for dirty socks, fishy, buttery popcorn, and sweet aromas, respectively. This demonstrates that there is variability in Stevens' Power Law exponents for odorants within fish sauce samples. [source] Structural analysis of secondary ions by post-source decay in time-of-flight secondary ion mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 4 2006David Touboul Tandem mass spectrometry measurements have been achieved using time-of-flight secondary ion mass spectrometry (TOF-SIMS) and a post source decay (PSD)-like method. The performance of the method has been demonstrated on model molecules with well-known fragmentation pathways. Several lipids have been fragmented including the phosphocholine ion, phosphatidylcholines, cholesterol and vitamin E. Pure samples were analyzed, and the results compared with those obtained with the same compounds on a quadrupole-TOF hybrid mass spectrometer. Then, the structures of some lipids which are currently observed in the TOF-SIMS imaging of mammalian tissue sections were verified. Copyright © 2006 John Wiley & Sons, Ltd. [source] A solution to the observed Z, = 2 preference in the crystal structures of hydrophobic amino acidsACTA CRYSTALLOGRAPHICA SECTION B, Issue 3 2009Carl Henrik Görbitz Chiral amino acids without functional groups in their side chains (hydrophobic amino acids) systematically form crystals with two molecules in the asymmetric unit. In contrast, racemates of the same compounds form crystals with Z, = 1. The present investigation addresses the origin of this important difference between enantiomeric and racemic crystals. Through a series of ab initio calculations on infinite two-dimensional slabs, derived from crystal structures, as well as calculations on full crystal structures it is shown that it is indeed possible to explain the observed behaviour. Additionally, the (not unexpected) observation that amino acids usually form racemates in the solid phase rather than undergoing racemic separation upon crystallization is rationalized on the basis of energy calculations. [source] Enteric bacteria may play a role in mammalian arsenic metabolismAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2001Koichi Kuroda Abstract The cecal content of rats administered dimethylarsinic acid for 6 months via drinking water was cultured in GAM medium with 10,mg l,1 of dimethylarsinic acid. Arsenic compounds in the culture were analyzed by ion chromatography with inductively coupled plasma mass spectrometry (IC,ICP-MS). Dimethylarsinic acid was metabolized. Two bacterial Escherichia coli strains, A3-4 and A3-6, were isolated from the culture. These strains metabolized dimethylarsinic acid and yielded two unidentified arsenic compounds, M-2 and M-3. A3-6 methylated dimethylarsinic acid to trimethylarsine oxide. Both strains metabolized trimethylarsine oxide and yielded an unidentified arsenic compound, M-1. These unknown arsenic compounds were the same compounds as detected in the urine and the feces of rats administered dimethylarsinic acid. The strains reduced arsenate to arsenite efficiently. Cysteine was required for metabolism of dimethylarsinic acid by these bacteria, but glutathione was not required. These results strongly suggested that the intestinal bacteria have a different arsenic metabolism from that in mammals and that they may play a possible role in mammalian arsenic metabolism. Copyright © 2001 John Wiley & Sons, Ltd. [source] Comparative analysis on microbial and rat metabolism of ginsenoside Rb1 by high-performance liquid chromatography coupled with tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 7 2008Guangtong Chen Abstract Ginsenoside Rb1 is an active protopanaxadiol saponin from Panax species. In order to compare the similarities and differences of microbial and mammalian metabolisms of ginsenoside Rb1, the microbial transformation by Acremonium strictum and metabolism in rats were comparatively studied. Microbial transformation of ginsenoside Rb1 by Acremonium strictum AS 3.2058 resulted in the formation of eight metabolites. Ten metabolites (M1,M10) were detected from the in vivo study in rats and eight of them were identified as the same compounds as those obtained from microbial metabolism by liquid chromatography,tandem mass spectrometry analysis and comparison with reference standards obtained from microbial metabolism. Their structures were identified as ginsenoside Rd, gypenoside XVII, 20(S)-ginsenoside Rg3, 20(R)-ginsenoside Rg3, ginsenoside F2, compound K, 12, -hydroxydammar-3-one-20(S) -O-, -d- glucopyranoside, and 25-hydroxyl-(E)-20(22)-ene-ginsenoside Rg3, respectively. The structures of the additional two metabolites were tentatively characterized as 20(22),24-diene-ginsenoside Rg3 and 25-hydroxyginsenoside Rd by HPLC-MS/MS analysis. M7,M10 are the first four reported metabolites in vivo. The time course of rat metabolism of ginsenoside Rb1 was also investigated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Liquid chromatography,tandem mass spectrometry for the identification of l -tetrahydropalmatine metabolites in Penicillium janthinellum and ratsBIOMEDICAL CHROMATOGRAPHY, Issue 1 2006Li Li Abstract l-Tetrahydropalmatine (l-THP) is an active alkaloid from Stephania ainiaca Diels. In order to compare the similarities and differences of microbial and mammalian metabolisms of l-THP, the microbial transformation by Penicillium janthinellum and metabolism in rats were investigated. Biotransformation of l-THP by Penicillium janthinellum AS 3.510 resulted in the formation of three metabolites. Their structures were identified as l-corydalmine, l-corypalmine and 9- O -desmethyl-l-THP, respectively, by comprehensive nuclear magnetic resonance and mass spectrometry (MS) analysis. Six metabolites (M1,M6) were detected from the in vivo study in rats and three of which (l-corydalmine, l-corypalmine and 9- O -desmethyl-l-THP) were identified as the same compounds as those obtained from microbial metabolism by liquid chromatography,tandem mass spectrometry (LC-MS[sol ]MS) analysis and comparison with reference standards obtained from microbial metabolism. The structures of the additional three metabolites were tentatively deduced as 2- O -desmethyl-l-THP and two di- O -demethylated l-THP by LC-MS[sol ]MS analysis. Time courses of microbial and rat metabolisms of l-THP were also investigated. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||