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Structural Elucidation (structural + elucidation)
Selected AbstractsArchazolid-7- O -,- D -glucopyranoside , Isolation, Structural Elucidation and Solution Conformation of a Novel V-ATPase Inhibitor from the Myxobacterium Cystobacter violaceusEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2007Dirk Menche Abstract The novel polyketide macrolide archazolid-7- O -,- D -glucopyranoside (3) has been isolated from the myxobacterium Cystobacter violaceus and the structure of this first archazolid-glycoside has been determined by spectroscopic and degradative methods. A synthesis of simplified 7- O analogues, based on regioselective derivatisation of archazolid A, was elaborated. These structurally novel archazolids of natural and synthetic origin were evaluated in detail for V-ATPase inhibition and their biological activities are discussed in terms of their solution conformations, as determined by high-field NMR studies, including J -based conformation analysis and constrained molecular dynamics simulations. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Cyrmenins, Novel Antifungal Peptides Containing a Nitrogen-Linked ,-Methoxyacrylate Pharmacophore: Isolation and Structural ElucidationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2004Thomas Leibold Abstract The novel antifungal metabolites cyrmenin A, B1, and B2 (1,3) were isolated from Archangium gephyra and Cystobacter armeniaca strains (myxobacteria). The cyrmenins are modified N -acyldipeptide esters containing a didehydroalanine, a 3- O -methyl-didehydroserine and a (2E,4Z)-undecadienoic or -dodecadienoic acid residue. These compounds represent the first bacterial counterparts of strobilurins that are characterized by an ,-substituted ,-methoxyacrylate pharmacophore. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Isolation, Structural Elucidation, and Synthesis of Curcutetraol.CHEMINFORM, Issue 24 2005Tanja Muelhaupt Abstract For Abstract see ChemInform Abstract in Full Text. [source] Isolation, Structural Elucidation, and Synthesis of RA-XVII, a Novel Bicyclic Hexapeptide from Rubia cordifolia, and the Effect of Side Chain at Residue 1 upon the Conformation and Cytotoxic Activity.CHEMINFORM, Issue 21 2004Yukio Hitotsuyanagi No abstract is available for this article. [source] Synthesis and Structural Elucidation of 1-(3-C-Ethynyl-4-thio-,-D-ribofuranosyl)cytosine (4,-ThioECyd).CHEMINFORM, Issue 7 2003Noriaki Minakawa Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Regioselective Bridging of Calixarenes , Syntheses, Structural Elucidation and Extraction Studies of 1,2-Calix[n]dioxocrowns (n = 6, 8).CHEMINFORM, Issue 5 2002Fafu Yang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] ChemInform Abstract: The Synthesis and First Full Structural Elucidation of a Benzotriazole Azo Dye.CHEMINFORM, Issue 23 2001Duncan Graham Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Selective Treatment of Cancer: Synthesis, Biological Evaluation and Structural Elucidation of Novel Analogues of the Antibiotic CC-1065 and the DuocarmycinsCHEMISTRY - A EUROPEAN JOURNAL, Issue 16 2007Abstract Novel diastereomerically pure ,- D -galactosidic prodrugs (+)- 12,a,e of the cytotoxic antibiotics CC-1065 and the duocarmycins were prepared for an antibody directed enzyme prodrug therapy (ADEPT) using 4 as a substrate via a radical cyclization to give rac - 5 and rac - 6 followed by a chromatographic resolution of the enantiomers of rac - 5, glycosidation and linkage to the DNA-binding units 10,a,e. These only slightly toxic compounds can be toxified enzymatically by an antibody,,- D -galactosidase conjugate at the surface of malignant cells to give the cytotoxic drugs, which then alkylate DNA. The new prodrugs were tested in in vitro cytotoxicity assays showing excellent QIC50 values of 4800 and 4300 for (+)- 12,a and (+)- 12,b, respectively. The absolute configuration of precursor (+)- 5 was determined by comparison of the experimental CD spectrum with the theoretically predicted CD spectra and by X-ray structure analysis. [source] How to Produce a Chemical Defense: Structural Elucidation and Anatomical Distribution of Aplysioviolin and Phycoerythrobilin in the Sea Hare Aplysia californicaCHEMISTRY & BIODIVERSITY, Issue 5 2010Michiya Kamio Abstract We previously used bioassay-guided fractionation to identify phycoerythrobilin (1) and its monomethyl ester, aplysioviolin (2), as components in the ink secretion of a marine gastropod, the sea hare Aplysia californica, that act as chemical deterrents against predatory blue crabs. This was the first report of 1 as a natural product. Compound 2 was previously reported as a natural product from three species of Aplysia (A. fasciata, A. dactylomela, and A. parvula), but the reported structure and composition of stereoisomers of 2 are different among these species. Sea hares are thought to produce 2 from phycoerythrin, a photosynthetic pigment in their red-algal diet composed of a phycobiliprotein covalently linked to the chromophore 1, by cleavage of the covalent bond and methylation of 1, but neither the sequence nor the anatomical location of the cleavage and methylation is known. In this study, we clarify the structure of 1 and 2 in ink secretion of A. californica, and describe the distribution of 1 and 2 in the tissues of sea hares. We conclude that cleavage of the covalent bond in phycoerythrin occurs first, forming 1 in the digestive gland, followed by methylation of 1 to yield 2 in the ink gland. [source] Structural elucidation of the wheat straw lignin polymer by atmospheric pressure chemical ionization tandem mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2003Joseph H. Banoub [source] Structural elucidation of four new furostanol saponins from Tupistra chinensis by 1D and 2D NMR spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 1 2009Kun Zou Abstract Four new furostanol saponins (1,4), two pairs of diastereoisomers, were isolated from methanolic extracts of Tupistra chinensis rhizomes and their structures were assigned from 1H and 13C NMR spectra, DEPT, and by 2D COSY, NOESY, HMQC, and HMBC experiments. Copyright © 2008 John Wiley & Sons, Ltd. [source] Total assignments of 1H and 13C NMR spectra of isocatalpanol and a derivative of tecomaquinoneMAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2005Allana Kellen L. Santos Abstract Isocatalpanol and tecomaquinone I were obtained from roots of Lippia sidoides, a medicinal plant from northeast Brazil. Reduction of tecomaquinone I with NaBH4 yielded a new derivative. Structural elucidation was done on the basis of spectral data, mainly by high-field NMR and electron ionization mass spectrometry. Copyright © 2005 John Wiley & Sons, Ltd. [source] Structural elucidation by 1D and 2D NMR of three isomers of a carotenoid lysophosphocholine and its synthetic precursorsMAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2004Bente Jeanette Foss Abstract A carotenoic acid was used to obtain a long-chain unsaturated lysophosphocholine. The carotenoid lysophosphocholine was synthesized by two methods. The first method resulted in mixtures of regioisomers for each step in the synthetic route. Homo- and heteronuclear 1D and 2D NMR methods were employed to elucidate the structures of the individual isomers and their intermediates. The pure regioisomer [1-(,-apo-8, -carotenoyl)-2-lyso- glycero -3-phosphocholine] was obtained by a second method, but in low yield. The 1D 1H NMR subtraction spectrum of the mixture and the pure regioisomer was used to interpret the 1H shifts of the unsaturated acyl moieties. The 1H and 13C signals of the acyl chain show characteristic shifts depending on the positions of the choline and the acyl group attached to the glycerol backbone. Therefore, the unsaturated acyl chain signals have diagnostic values for the identification of isomers of unsaturated (lyso)phosphocholines. Chemical shifts and indirect coupling constants are reported for each of the major components of the mixtures. The methods used were 1D (1H, 13C and 31P) and 2D (H,H-COSY, HMBC, HSQC and HETCOR) NMR. Copyright © 2004 John Wiley & Sons, Ltd. [source] Structural elucidation of metabolites of ginkgolic acid in rat liver microsomes by ultra-performance liquid chromatography/electrospray ionization tandem mass spectrometry and hydrogen/deuterium exchangeRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2009Z. H. Liu Ginkgolic acids have been shown to possess allergenic as well as genotoxic and cytotoxic properties. The question arises whether the metabolism of ginkgolic acids in the liver could decrease or increase their toxicity. In this study, the invitro metabolism of ginkgolic acid (15:1, GA), one component of ginkgo acids, was investigated as a model compound in Sprague-Dawley rat liver microsomes. The metabolites were analyzed by ultra-performance liquid chromatography coupled with photodiode array detector/negative-ion electrospray ionization tandem mass spectrometry (UPLC-PDA/ESI-MS/MS) and hydrogen/deuterium (H/D) exchange. The result showed that the benzene ring remained unchanged and the oxidations occurred at the side alkyl chain in rat liver microsomes. At least eight metabolites were found. Among them, six phase I metabolites were tentatively identified. This study might be useful for the investigation of toxicological mechanism of ginkgolic acids. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structural elucidation of the Bi2(n,+,2)MonO6(n,+,1) (n = 3, 4, 5 and 6) family of fluorite superstructures by transmission electron microscopyACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2009Ángel R. Landa-Cánovas The cationic framework structure of a whole new family of compounds with the general formula Bi2(n,+,2)MonO6(n,+,1) (n = 3, 4, 5 and 6) has been elucidated by transmission electron microscopy (TEM) methods. High-resolution transmission electron microscopy (HRTEM) has been used to postulate heavy-atom models based on the known structure of the n = 3 phase, Bi10Mo3O24. These models were tested by HRTEM image simulation, electron diffraction and powder X-ray diffraction simulation methods which agreed with the experimental results. The four known phases of this family correspond to n = 3, 4, 5 and 6 members and all show fluorite superstructures. They consist of a common ,-Bi2O3 fluorite-type framework, inside of which are distributed ribbons of {MoO4} tetrahedra which are infinite along b, one tetrahedron thick along c, and of variable widths of 3, 4, 5 or 6 {MoO4} tetrahedra along a depending on the family member (n value). These {MoO4} tetrahedra are isolated, i.e. without sharing any corner as in the [Bi12O14] columnar structural-type phase Bi[Bi12O14][MoO4]4[VO4]. The structure of all these family members can be described as crystallographic shear derivatives from Aurivillius-type phases such as Bi2MoO6, the n = , end member. All these compounds are good oxygen-ion conductors. [source] 5-Alpha- and 5-beta-2-deoxyintegristerone A, a 5-alpha and 5-beta isomer pair of ecdysteroids isolated from the Silene genusBIOMEDICAL CHROMATOGRAPHY, Issue 6 2002M. Báthori 5-Alpha-2-deoxyintegristerone A and 5-beta-2-deoxyintegristerone A were isolated from the aerial parts of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman using a specific combination of absorption column chromatography, preparative thin-layer chromatography and preparative HPLC. Both normal-phase and reversed-phase modes of HPLC were employed for isolation. Structural elucidation of 5-alpha-2-deoxyintegristerone A was completed by X-ray diffraction. Both 5-alpha-2-deoxyintegristerone A and 5-beta-2-deoxyintegristerone A were firstly isolated from this plant. We propose that 5-alpha-2-deoxyintegristerone A is not an artifact but an integral part of the ecdysteroid spectrum of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman. Copyright © 2002 John Wiley & Sons, Ltd. [source] Joziknipholones A and B: The First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescensCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008Gerhard Bringmann Prof. Abstract From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated, together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P -configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M -configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells. [source] Differentiation of structural isomers in a target drug database by LC/Q-TOFMS using fragmentation predictionDRUG TESTING AND ANALYSIS, Issue 6 2010Elli Tyrkkö Abstract Isomers cannot be differentiated from each other solely based on accurate mass measurement of the compound. A liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOFMS) method was used to systematically fragment a large group of different isomers. Two software programs were used to characterize in silico mass fragmentation of compounds in order to identify characteristic fragments. The software programs employed were ACD/MS Fragmenter (ACD Labs Toronto, Canada), which uses general fragmentation rules to generate fragments based on the structure of a compound, and SmartFormula3D (Bruker Daltonics), which assigns fragments from a mass spectra and calculates the molecular formulae for the ions using accurate mass data. From an in-house toxicology database of 874 drug substances, 48 isomer groups comprising 111 compounds, for which a reference standard was available, were found. The product ion spectra were processed with the two software programs and 1,3 fragments were identified for each compound. In 82% of the cases, the fragment could be identified with both software programs. Only 10 isomer pairs could not be differentiated from each other based on their fragments. These compounds were either diastereomers or position isomers undergoing identical fragmentation. Accurate mass data could be utilized with both software programs for structural elucidation of the fragments. Mean mass accuracy and isotopic pattern match values (SigmaFit; Bruker Daltonics Bremen, Germany) were 0.9 mDa and 24.6 mSigma, respectively. The study introduces a practical approach for preliminary compound identification in a large target database by LC/Q-TOFMS without necessarily possessing reference standards. Copyright © 2010 John Wiley & Sons, Ltd. [source] Determination of bupivacaine and metabolites in rat urine using capillary electrophoresis with mass spectrometric detectionELECTROPHORESIS, Issue 14 2003Ryan M. Krisko Abstract A method using capillary electrophoresis-mass spectrometry (CE-MS) was developed for the structural elucidation of bupivacaine and metabolites in rat urine. Prior to CE-MS analysis, solid-phase extraction (SPE) was used for sample cleanup and preconcentration purposes. Exact mass and tandem mass spectrometric (MS/MS) experiments were performed to obtain structural information about the unknown metabolites. Two instruments with different mass analyzers were used for mass spectrometric detection. A quadrupole time-of-flight (Q-TOF) and a magnetic sector hybrid instrument were coupled to CE and used for the analysis of urine extracts. Hydroxybupivacaine as well as five other isomerically different metabolites were detected including methoxylated bupivacaine. [source] Thioxoethenylidene C2S: A Matrix - Spectroscopic StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2004Günther Maier Abstract Thioxoethenylidene C2S (5), known for its high abundance in interstellar space, has been generated by irradiation of C3S2 (4) and C3OS (6) in an argon matrix at 10 K. Its structural elucidation is based on comparison of the experimental and calculated IR and UV spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Identification of Major Alkaloids in Rat Urine by HPLC/DAD/ESI-MS/MS Method Following Oral Administration of Cortex Phellodendri DecoctionHELVETICA CHIMICA ACTA, Issue 2 2009Chun-Hui Ma Abstract A rapid, sensitive, and specific high-performance liquid chromatography (HPLC), diode-array detection, and mass-spectrometry techniques were developed for an identification of the constituents of Cortex Phellodendri and their metabolites in rat urine. The dose of 10,ml/kg of Cortex Phellodendri decoction was used for rats' oral administration. 0,24-h Urine was purified using a C18 solid-phase extraction cartridge, and then analyzed by an on-line MS detector. A total of 13,characteristic HPLC peaks were detected in the urine samples. Nine of them, including five alkaloids and four of their metabolites, were tentatively elucidated as magnoflorine (1), the glucuronide conjugate of demethyleneberberine (2), menisperine (3), jatrorrhizine 3- O -glucuronide (4), berberubine 9- O -glucuronide (5), jatrorrhizine (6), the monomethyl and monohydroxy catabolite of berberubine (7), palmatine (8), and berberine (9). Identification and structural elucidation of the metabolites were performed by comparing their MSn spectra data with those reported. [source] Two New Endiandric Acid Analogs, a New Benzopyran, and a New Benzenoid from the Root of Beilschmiedia erythrophloiaHELVETICA CHIMICA ACTA, Issue 11 2008Ping-Shin Yang Abstract Phytochemical investigation of the root of Beilschmiedia erythrophloia led to the isolation and structural elucidation of two new endiandric acid analogs, endiandric acids I and J (1 and 2, resp.), a new benzopyran, dehydrooligandrol methyl ether (3), and a new benzenoid, farnesylol (4), together with six known compounds. Their structures were established on the basis of extensive 1D- and 2D-NMR analyses in combination with HR-MS experiments. [source] N -Cyanomethyl- N -Methyl-1-(3,,4,-methylenedioxyphenyl)-2-propylamine: An MDMA Manufacturing By-ProductJOURNAL OF FORENSIC SCIENCES, Issue 5 2008Helen Salouros B.Sc. Abstract:, This paper describes the structural elucidation of a compound produced during the synthesis of 3,4-methylenedioxymethylamphetamine (MDMA) via the reductive amination of 3,4-methylenedioxyphenyl-2-propanone (3,4-MDP-2-P) with methylamine and sodium cyanoborohydride. The compound was isolated from MDMA by column chromatography, proton and carbon nuclear magnetic resonance spectroscopy, LC/mass spectrometry, and total synthesis were used to identify the compound as N -cyanomethyl- N -methyl-1-(3,,4,-methylenedioxyphenyl)-2-propylamine. This compound has been identified as a potential synthetic route marker for the reductive amination of 3,4-MDP-2-P with methylamine and sodium cyanoborohydride and as such it should prove valuable to forensic scientists engaged in profiling illicit drugs. Profiling MDMA can provide useful information to law enforcement agencies relating to synthetic route, precursor chemicals and reagents employed and may be used for comparative analyses of different drug seizures. This paper also describes the structural elucidation of the analogous methylamphetamine synthetic route marker compound, N -cyanomethyl- N -methyl-1-phenyl-2-propylamine, produced during the reductive amination of phenyl-2-propanone using methylamine and sodium cyanoborohydride. [source] Structure analysis of triterpene saponins in Polygala tenuifolia by electrospray ionization ion trap multiple-stage mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2007Jiangyun Liu Abstract Eighteen different triterpene saponins isolated from Polygala tenuifolia were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. MS1 -MS3/MS4 spectra of the both modes were analyzed, and they all gave fragments in line and shared common fragmentation patterns. Key fragments from MSn spectra of both the modes and their proposed fragmentation pathways were constructed with examples illustrated for the formation of characteristic fragments in the saponins. Two special fragmentation patterns were proposed: (1) the formation of fragments by cleavage of CH2O from ,12 -14,-CH2OH of the oleanene-type saponin aglycone in both positive and negative MSn (n , 2) modes; (2) the occurrence of fragments by cleavage of CO2 and 3-glucose as the characteristic structure feature of 23-COOH at the oleanene-type saponin aglycones coupled with 3-Glc substitutes in the negative MSn (n , 2) modes. Peak intensities in MSn spectra were also correlated with structural features and fragmentation preferences of the investigated saponins, which are discussed in detail. In general, fragments formed predominantly by cleavages of glycosidic bonds in the positive mode, while selective cleavages of acyl bonds preceded that of glycosidic bonds in negative MSn (n , 2) mode, both of which could well be applied to the structural analysis of these saponins. Interpretation of MSn spectra presented here provided diagnostic key fragment ions important for the structural elucidation of saponins in P.tenuifolia. Copyright © 2007 John Wiley & Sons, Ltd. [source] Oligosaccharide sequences in Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Susanna Broberg Abstract Ten different samples with 13 previously identified saponin structures from Quillaja saponaria Molina were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. Both positive and negative ion mode MS1,MS4 spectra were analyzed, showing that structural information on the two oligosaccharide parts in the saponin can be obtained from positive ion mode spectra whereas negative ion mode spectra mainly gave information on one of the oligosaccharide parts. Analysis of MS1,MS4 spectra identified useful key fragment ions important for the structural elucidation of Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from MS1,MS3 spectra was constructed for the identification of structural elements in the saponin. Peak intensity ratios in MS3 spectra were found to be correlated with structural features of the investigated saponins and are therefore of value for the identification of terminal monosaccharide residues. Copyright © 2004 John Wiley & Sons, Ltd. [source] Utilisation of electrospray time-of-flight mass spectrometry for solving complex fragmentation patterns: application to benzoxazinone derivativesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 10 2003L. S. Bonnington Abstract In this paper we describe the application of electrospray time-of-flight mass spectrometry (ESI-TOFMS) to structural elucidation of the fragment ions formed from a range of natural and synthetic allelochemical derivatives. The extensive mass spectrometric characterisation of ten non-glucosylated benzoxazinone derivatives using this method is described here for the first time. The analytes include six naturally occurring 1,4-benzoxazin-3(4H)-one derivatives, including the hydroxamic acids DIMBOA [2,4-dihydroxy-7-methoxy-2H -1,4-benzoxazin-3(4H)-one] and DIBOA [2,4-dihydroxy-2H -1,4-benzoxazin-3(4H)-one], lactams HBOA [2-hydroxy-2H -1,4-benzoxazin-3(4H)-one] and HMBOA [2-hydroxy-7-methoxy-2H -1,4-benzoxazin-3(4H)-one], benzoxazolinones BOA [benzoxazolin-2(3H)-one] and MBOA [6-methoxy-benzoxazolin-2(3H)-one] and four synthetic variations, 2,H-DIBOA [4-hydroxy-2H -1,4-benzoxazin-3(4H)-one], 2,OMe-DIBOA [2-methoxy-4-hydroxy-2H -1,4-benzoxazin-3(4H)-one], 2,H-HBOA [2H -1,4-benzoxazin-3(4H)-one] and 2,OMe-HBOA [2-methoxy-2H -1,4-benzoxazin-3(4H)-one]. Assignments of the mass spectral fragments were aided by elemental composition calculation results, comparison of structural analogues and background literature, and acquired knowledge regarding feasible structures for the compounds. The influence of substituents on the chemical reactivity of the compounds with respect to the observed MS behaviour over varying nozzle potentials is addressed and, through comparison of the structural analogues, generic fragmentation patterns have also been identified. Copyright © 2003 John Wiley & Sons, Ltd. [source] Oxidative metabolism by Thalassiosira weissflogii (Bacillariophyceae) of a diol-ester of okadaic acid, the diarrhetic shellfish poisoningJOURNAL OF PHYCOLOGY, Issue 2 2000Anthony J. Windust Previous investigations into the comparative toxicity of the diarrhetic shellfish poisoning (DSP) toxins to Thalassiosira weissflogii (Grun.) Fryxell et Hasle found that this diatom oxidatively metabolized okadaic acid diol-ester (OA diol-ester) to a more water-soluble product. This oxidative transformation of OA diol-ester by the diatom is significant for two reasons. First, it is known that dinophysistoxin-4 (DTX-4), the primary DSP toxin produced by the dinoflagellate Exuviaella lima (Ehr.) Butschli, will be hydrolyzed to the diol-ester following cell rupture (e.g. ingestion by a predator). Second, it implies that the ester, an uncharged, lipophilic intermediate, can easily enter cells and therefore may play an important role in the uptake and transfer of DSP toxins through the food web. It has been suggested that the water soluble DTX-4 may also be the form in which DSP toxins are excreted from the producing cell. Therefore, the stability of DTX-4 was examined when incubated either in fresh seawater medium into which washed cells of E. lima were introduced or in seawater medium conditioned by E. lima cells. Rapid hydrolysis of DTX-4 to the diol-ester took place in both cases. Thus, regardless of the route by which DTX-4 is liberated from the cell, either by cell disruption or excretion, the diol-ester will be the dominant form of the toxin to challenge associated organisms. To examine the metabolism of OA diol-ester by T. weissflogii in more detail, serial cultures of the diatom were challenged with OA diol-ester at a concentration of 2.0 ,g·mL,1. The metabolism and fate of the diol-ester in both cellular and medium fractions were monitored over 3 days using liquid chromatography with either ultraviolet (LC-UV) or mass spectrometric (LC-MS) detection. During the course of the experiment, all of the diol-ester was metabolized. LC-MS analysis revealed the presence of multiple oxidative products of OA diol-ester in the medium fraction, including a carboxylic acid derivative. The major metabolites were isolated in sufficient quantity to permit structural elucidation by NMR and MS. All the metabolites identified resulted from oxidation of the diol-ester side chain with the primary sites of attack at the terminal, subterminal, and unsaturated carbons. OA was found in both cellular and medium fractions, and its production was directly correlated with the metabolism of the diol-ester. The relative partitioning of both OA diol-ester and its oxidation products between cells and medium supports the contention that OA diol-ester can readily enter cells, be metabolized, and then excreted in more water-soluble forms. [source] 1,1,1-Trichloro-3-(1-phenethylamino-ethylidene)- pentane-2,4-dione,synthesis, spectroscopic, theoretical and structural elucidationJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2007Tsonko M. Kolev Abstract 1,1,1-Trichloro-3-(1-phenethylamino-ethylidene)-pentane-2,4-dione is spectroscopically and structurally elucidated by means of linear-polarized IR spectroscopy (IR-LD) of oriented solids as a colloidal suspension in nematic liquid crystal. Structural information and IR-spectroscopic assignment are supported by quantum chemical calculations at MP2 and B3LYP level of theory and 6-311++G** basis set. The geometry is characterized with an inramolecular hydrogen bond of NH,OC with length of 2.526,Ĺ and a NHO angle of 140.5(1)°. The NHC(CH3)CCCO(CH3) fragment is nearly flat with a maximal deviation of total planarity of 10.4°. Copyright © 2007 John Wiley & Sons, Ltd. [source] Production of bioactive metabolites by Nocardia levis MK-VL_113LETTERS IN APPLIED MICROBIOLOGY, Issue 4 2009A. Kavitha Abstract Aims:, To isolate and identify the bioactive compounds produced by Nocardia levis MK-VL_113. Methods and Results:, Cultural characteristics of Noc. levis isolated from laterite soils of Guntur region were recorded on International Streptomyces Project media. Morphological studies of the strain through scanning electron microscopy revealed the clear pattern of its hyphal fragmentation into rod-shaped bacilli. Chemical examination of the secondary metabolites of the strain grown on sucrose,tryptone broth led to the isolation of three fractions active against Bacillus cereus. Further analysis of second fraction resulted in the isolation of two active subfractions. Two different phthalate esters, namely, bis-(2-ethylhexyl) phthalate and bis-(5-ethylheptyl) phthalate, were purified from the first active subfraction, and the structural elucidation of these compounds was confirmed on the basis of FT-IR, mass and NMR spectroscopy. The partially purified second subfraction subjected to Gas Chromatography,Mass spectroscopy contained nine components: decanedioic acid; 2,6-piperdione monooxime; 1-eicosanol; beta-1-arabinopyranoside, methyl; cyclopentaneundecanoic acid; hexadecanoic acid; silane, trichloro eicosyl; 1-hexacosanol; and 1,2-dodecanediol. The antimicrobial activity of the bioactive compounds produced by Noc. levis was expressed in terms of minimum inhibitory concentration. Conclusions:, The present study clearly revealed that the metabolites of Noc. levis act as bioactive compounds against Gram-positive and Gram-negative bacteria, yeast and filamentous fungi. It also supports the idea that there are a number of rare actinomycetes remained to be explored for new bioactive compounds. Significance and Impact of the Study:, Metabolites of Noc. levis exhibited antibacterial and antifungal activities. This is the first report of bis-(5-ethylheptyl) phthalate as well as the nine partially purified compounds from actinomycetes. In addition, this is also the first report of bis-(2-ethylhexyl) phthalate from the genus Nocardia. [source] Complete assignment of the 1H and 13C NMR spectra of garciniaphenone and keto-enol equilibrium statements for prenylated benzophenonesMAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2008Priscilla B. M. C. Derogis Abstract This article reports the structural elucidation by IR, UV and MS spectroscopic data along with 1H and 13C NMR chemical shift assignments of two benzophenones isolated from the fruit pericarp of Garcinia brasiliensis Mart. (Clusiaceae): garciniaphenone, (1R,5S,7S)-3-benzoyl-4-hydroxy-6,6-dimethyl-5,7-di(3-methyl-2-butenyl)bicyclo[3.3.1]non-3-ene-2,9-dione, a novel triprenylated benzophenone; and 7- epi -clusianone, a tetraprenylated benzophenone that has already been extracted from another species of the same family. Furthermore, the keto-enol tautomeric equilibrium at solution-state was described for these compounds by 1D and 2D NMR spectral methods and one attempt to rationalize the different ratios between the noted tautomers was based on stereochemical features. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||||||||