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Spectral Assignments (spectral + assignment)
Selected AbstractsChange in editorial policy from January 2010: Discontinuation of the Spectral Assignments and Reference Data and Notes categories, and introduction of the new category MRC LettersMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2009James Keeler Editor in Chief Cambridge, July 200 [source] Conformational and substituent effects in the 19F spectra of C7,C10 straight-chain chlorofluoroalkanesMAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2004Wallace S. Brey Abstract One- and two-dimensional fluorine NMR spectra of straight-chain chlorofluoroalkanes having 7,10 carbons were obtained and interpreted. Spectral assignments were based primarily on indirect spin,spin correlations. A scale of chlorine substituent effects was developed. The effects of asymmetric CFCl centers on chemical-shift differences in nearby CF2 groups were analyzed in terms of molecular conformational effects. Spin,spin coupling patterns of CF3 groups were elucidated. Copyright © 2004 John Wiley & Sons, Ltd. [source] DFT-GIAO1H NMR chemical shifts prediction for the spectral assignment and conformational analysis of the anticholinergic drugs (,)-scopolamine and (,)-hyoscyamineMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2010Marcelo A. Muñoz Abstract The relatively large chemical shift differences observed in the 1H NMR spectra of the anticholinergic drugs (,)-scopolamine 1 and (,)-hyoscyamine 2 measured in CDCl3 are explained using a combination of systematic/molecular mechanics force field (MMFF) conformational searches and gas-phase density functional theory (DFT) single point calculations, geometry optimizations and chemical shift calculations within the gauge including/invariant atomic orbital (GIAO) approximation. These calculations show that both molecules prefer a compact conformation in which the phenyl ring of the tropic ester is positioned under the tropane bicycle, clearly suggesting that the chemical shift differences are produced by the anisotropic effect of the aromatic ring. As the calculations fairly well predict these experimental differences, diastereotopic NMR signal assignments for the two studied molecules are proposed. In addition, a cursory inspection of the published 1H and 13C NMR spectra of different forms of 1 and 2 in solution reveals that most of them show these diastereotopic chemical shift differences, strongly suggesting a preference for the compact conformation quite independent of the organic or aqueous nature of the solvent. Copyright © 2010 John Wiley & Sons, Ltd. [source] Structural and spectral assignment of a new diterpenoid isolated from Ballota undulata and a complete 1H and 13C NMR data assignment for three other structurally related compoundsMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2007Ahmed A. Hussein Abstract The structure of 3,-hydroxyballotinone, a new labdane diterpenoid isolated from Ballota undulata, has been established by NMR spectroscopic studies. In addition, complete and unambiguous assignments of the 1H and 13C NMR spectra of three other already known labdanes (ballotinone, ballonigrin and ballonigrinone) isolated from the same source have been achieved. The assignments are based on 2D shift-correlated 1H1H COSY, 1H13C gHSQC [1J(C,H)] and 1H13C gHMBC [nJ(C,H) (n = 2 and 3)], and NOE experiments. Copyright © 2007 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR spectral assignment of ,- and ,-adenosine, 2,-deoxyadenosine and their acetate derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2007P. Ciuffreda Abstract 1H and 13C NMR chemical shifts of ,- and ,-anomers of adenosine, 2,-deoxyadenosine and their acetate derivatives were completely and definitely assigned using the concerted application of one- and two-dimensional experiments (gCOSY, gNOESY, gHSQC and gHMBC). The influence of the stereochemistry of the purine base on the NMR data of the hydrogen and carbon atoms of the furanose moiety was estimated. Copyright © 2007 John Wiley & Sons, Ltd. [source] Complete 1H and 13C NMR spectral assignment of symmetric and asymmetric bis-spiropyran derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2005Sam-Rok Keum Abstract 1H and 13C NMR spectra of symmetric and asymmetric bis-spiropyrans, Series 1-3, were completely assigned. Especially, the 1H assignment of asymmetric spiropyrans was achieved by utilizing 1H,1H COSY and nOe experiments. All of the carbons in the dye molecules were investigated through a combination of heteronuclear 2D-shift correlation spectroscopy (HETCOR), together with an attached proton test (APT). Copyright © 2005 John Wiley & Sons, Ltd. [source] Structural and spectral assignment by 2D NMR of a new prenylated benzopyrancarboxylic acid and structural reassignment of a related compoundMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2003Sharon J. Burke Abstract A new prenylated benzopyrancarboxylic acid, 1a (3,4-dihydro-5-hydroxy-2,7-dimethyl-8-(2-methyl-2-butenyl)- 2-(4-methyl-1, 3-pentadienyl)-2H -1-benzopyran-6-carboxylic acid) was isolated from Peperomia amplexicaulis and fully characterized by 1D and 2D NMR and high-resolution mass spectrometry. In the course of this investigation, the structure of a related compound (minus the carboxylic acid group) which was previously assigned as 2b was corrected to structure 1b. Copyright © 2003 John Wiley & Sons, Ltd. [source] Synthesis and Photoinduced Electron-Transfer Properties of Phthalocyanine,[60]Fullerene ConjugatesCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2008Maurizio Quintiliani Dr. Abstract A series of three novel ZnPc,C60 conjugates (Pc=phthalocyanine) 1,a,c bearing different spacers (single, double, and triple bond) between the two electroactive moieties was synthesized and compared to that of ZnPc,C60 conjugate 2, in which the two electroactive moieties are linked directly. The synthetic strategy, towards the preparation of 1,a,c, involved palladium-catalyzed cross-coupling reactions over a monoiodophthalocyanine precursor 4 to introduce the corresponding spacer, and subsequent dipolar cycloaddition reaction to C60. Detailed photophysical investigations of 1,a,c and 2 prompted an intramolecular electron transfer that evolves from the photoexcited ZnPc to the electron-accepting C60. In particular, with the help of femtosecond laser photolysis charge separation was indeed confirmed as the major deactivation channel. Complementary time-dependent density functional calculations supported the spectral assignment, namely, the spectral identity of the ZnPc.+ radical cation and the C60., radical anion as seen in the differential absorption spectra. The lifetimes of the correspondingly formed radical ion-pair states depend markedly on the solvent polarity: they increase as polarity decreases. Similarly, although to a lesser extent, the nature of the linker impacts the lifetime of the radical ion-pair states. In general, the lifetimes of these states tend to be shortest in the system that lacks any spacer at all (2), whereas the longest lifetimes were found in the system that carries the triple-bond spacer (1,a). [source] Syntheses and Coordination Chemistry of Aminomethylphosphine Derivatives of AdenineEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2003Qingzhi Zhang Abstract Two aminomethylphosphane derivatives of adenine 9-(2-{bis[(diphenylphosphanyl)methyl]amino}ethyl)adenine (La) and 9-(3-{bis[(diphenylphosphanyl)methyl]amino}propyl)adenine (Lb) were synthesised. Oxidation of La and Lb with H2O2, elemental sulfur or elemental selenium led to the corresponding oxidized products 4a/b,6a/b. Both La and Lb behave as didentate ligands towards late transition metals. Reaction of La or Lb with [MX2(cod)] (M = Pd, Pt; X = Cl, Me) gave chelate complexes 7a/b,10a/b. Reaction of La or Lb with [AuCl(tht)] or [{RuCl(,-Cl)(p -MeC6H4iPr)}2] gave the didentate bridging complexes 11a/b and 12a. All compounds have been fully characterised by microanalysis, IR, 1H and 31P{1H} NMR spectroscopy, and EI/CI/FAB mass spectrometry. 1H{31P} NMR and 1H- 13C correlation experiments were used to confirm the spectral assignments where necessary. Two compounds were structurally characterised by X-ray crystallographic analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] NMR analysis of butyl acrylate/methylmethacrylate/,-methyl styrene terpolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Neil T. McManus Abstract Composition analysis for butyl acrylate (BA)/ methyl methacrylate (MMA)/,-methyl styrene terpolymers was carried out by NMR spectroscopy methods. 1H-NMR was used primarily for this analysis, but because the method did not provide independent measurements for the BA and MMA fractions, the terpolymer composition analysis was open to higher than normal levels of uncertainty. Supplementary analyses were made with quantitative 13C-NMR methods to confirm the results from 1H-NMR (quantitative 13C-NMR was used to provide corroboration of selected composition analyses). To confirm spectral assignments in the 1H- and 13C-NMR spectra, heteronuclear multiple quantum coherence and J Modulated Spin Echo (JMOD) pulse sequences were used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2093,2098, 2007 [source] Trypanocidal and antifungal activities of p -hydroxyacetophenone derivatives from Calea uniflora (Heliantheae, Asteraceae)JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2004Andréa Mendes do Nascimento The dichloromethane extract of underground parts of Calea uniflora (Heliantheae, Asteraceae) exhibited trypanocidal and antifungal activities. Four p -hydroxyacetophenone derivatives were isolated as the main compounds: 2-senecioyl-4-(hydroxyethyl)-phenol (1), 2-senecioyl-4-(angeloyloxy-ethyl)-phenol (2), and two new derivatives, 2-senecioyl-4-(methoxyethyl)-phenol (3) and 2-senecioyl-4-(pentadecanoyloxyethyl)-phenol (4). 1 and 4 were active towards Trypanosoma cruzi trypomastigotes, reducing their number by 70 and 71% at 500 ,g mL,1, whereas 2 and 3 were inactive. All the compounds tested showed antifungal activity with minimal inhibitory concentration values between 500 and 1000 ,g mL,1 against pathogenic Candida spp. and dermatophytes. The isolation, structure elucidation, NMR spectral assignments and bioactivity results of these compounds are reported. [source] Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two-dimensional nuclear magnetic resonance spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2001A. S. Brar Abstract Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from 1H NMR spectra, and comonomer reactivity ratios were determined by the Kelen,Tudos (KT) method and the nonlinear least-squares error-in-variable method (EVM). The reactivity ratios obtained from KT and EVM were rG = 37.4 ± 12.0 and rV = 0.036 ± 0.019 and rG = 35.2 and rV = 0.03, respectively. Complete spectral assignments of 13C and 1H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two-dimensional 13C,1H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051,4060, 2001 [source] Structure elucidation and complete NMR spectral assignments of two new oleanane-type pentacyclic triterpenoid saponins from the husks of Xanthoceras sorbifolia BungeMAGNETIC RESONANCE IN CHEMISTRY, Issue 11 2009Ying Guo Abstract Two new saponins were isolated from husks of Xanthoceras sorbifolia Bunge and their structures were elucidated as 3-O-[,-D-galactopyranosyl(1,2)]-,-L-arabinofuranosyl(1,3)-,-D-methyl glucuronic acid-21-O-(3,4-diangeloyl)-,-L-rhamnose-3,, 16,, 21,, 22,, 28,-pentahydroxyl-22-acetoxy-olean-12-ene(1) and 3-O-[,-D-galactopyranosyl(1,2)]-,-L-arabinofuranosyl(1,3)-,-D-methyl glucuronic acid-21,22-O-diangeloyl-3,,15,,16,,21,,22,,28,-hexahydroxyl-olean-12-ene(2) on the basis of 1D and 2D NMR (including 1H, 13C-NMR, 1H1H COSY, HSQC, HMBC and DEPT), ESI-MS spectrometry and chemical methods. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structure elucidation and NMR assignments of two new pyrrolidinyl quinoline alkaloids from chestnut honeyMAGNETIC RESONANCE IN CHEMISTRY, Issue 5 2009Giangiacomo Beretta Abstract The complete 1H, 13C and 15N NMR spectral assignments of two new alkaloids isolated from chestnut honey and structurally related to kynurenic acid have been made using 1-D and 2-D NMR techniques, including COSY, HMQC and HMBC experiments. The new compounds have been identified as 3-(2,-pyrrolidinyl)-kynurenic acid and its ,-lactam derivative. Copyright © 2009 John Wiley & Sons, Ltd. [source] Structure elucidation and complete NMR spectral assignments of four new diterpenoids from Smallantus sonchifoliusMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2008De-Qiang Dou Abstract Four new diterpenoids, named smaditerpenic acid A,D, together with five known compounds, were isolated from the H2O extract of the leaves of Smallantus sonchifolius (yacon) cultivated in Liaoning, China and their structures were elucidated on the basis of one- and two-dimensional NMR (including 1H, 13C-NMR, 1H1H COSY, HSQC, TOCSY, HMBC, and ROESY), electrospray ionization mass spectrometry (ESI-MS), and chemical methods. Copyright © 2008 John Wiley & Sons, Ltd. [source] 1H and 13C NMR spectral assignments of some novel 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-one derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2008Paramasivam Parthiban Abstract The 1H and 13C NMR spectra of 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-ones (1,2), oximes (3,8) and O -benzyl oximes (9,12) were recorded. The chemical shifts were unambiguously assigned using 1D and 2D NMR spectral data. The results clearly indicate that the compounds exist in chair-boat conformation with equatorial and axial orientation of the aryl groups in the chair and boat forms, respectively. Since the molecules are flexible and dynamic in solution, the chair and boat forms are mutually interconvertible. In 3,12, because of the effect of oximation/oximination, all the protons in the heterobicyclic systems gave distinct signals except the benzylic protons of the boat form. In all synthesized compounds, the aryl group protons at C-6,8 are shielded by the aryl groups at C-2,4 and therefore appear in the lower frequency region than the aryl groups at C-2,4. Copyright © 2008 John Wiley & Sons, Ltd. [source] Substituent effects of the N,N -dimethyl- sulfamoyl group on the 1H and 13C NMR spectra of positional isomers of quinolines,MAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2008Andrzej Ma, lankiewicz Abstract The complete 1H and 13C NMR spectral assignments of seven positional isomers of N,N -dimethylsulfamoylquinolines 2,8 and quinoline have been made using 1D and 2D NMR techniques, including COSY, HMQC and HMBC experiments. ,,H and ,,C substituent effects induced by the sulfamoyl group were determined. The sulfamoyl substituent affects proton and carbon chemical shifts both in the parent and in the fused (pyridine or benzene) ring. Copyright © 2007 John Wiley & Sons, Ltd. [source] Structure elucidation and NMR spectral assignments of three new lignan glycosides from Akebia trifoliataMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2008Shu-hong Guan Abstract Three new lignan glycosides (1,3) were isolated from the stems of Akebia trifoliata. Their structures were elucidated as (7R,8R,7,R,8,R)3,3,,5,5,tetramethoxy-4,4,dihydroxy-7,9,:7,,9-diepoxylignan-4- O -,- D -glucopyranoside (1), (7S,8S,8,R)-4,4,,9-trihydroxy-3,3,,5,5,-tetramethoxy-7,9,-epoxylignan-7,-one 9- O -,- D -glucopyranoside (2), (7R,8R,8,S)-4,4,,9-trihydroxy3,3,,5,5,-tetramethoxy-7,9,-epoxylignan-7,-one 9- O -,- D -glucopyranoside (3) by spectral analyses, primarily NMR, MS and CD. The NMR assignments for the compounds were carried out using 1H, 13C, DEPT, COSY, HSQC, HMBC and ROESY NMR experiments. Copyright © 2007 John Wiley & Sons, Ltd. [source] Temperature and solvent dependent NMR studies on mangiferin and complete NMR spectral assignments of its acyl and methyl derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2006Shaheen Faizi Abstract By employing concerted 1 and 2D NMR techniques, exact NMR spectral assignments have been made of the acyl (2,7) and methyl (8 and 9) derivatives of mangiferin (1) isolated from the leaves of Bombax ceiba. Derivatives 2, 8 and 9 have been reported in literature, while 3,7 represent new compounds. The acetates 2 and 3 were found to be unstable and were converted into the same penta-acetate 4 at room temperature. Extensive NMR studies on mangiferin (1) and its derivatives showed that H-4 exchanges with deuterium of the solvent molecule more easily. This exchange under acidic conditions occurred at that position (C-4) where electrophilic substitution reactions can easily take place. This is the first report describing the exchange of C-4 proton of mangiferin (1), or any other xanthone, with deuterium of solvent molecules. Copyright © 2006 John Wiley & Sons, Ltd. [source] Structural analysis of 3-,-acetyl-20(29)-lupene-24-oic acid, a novel pentacyclic triterpene isolated from the gum resin of Boswellia serrata, by NMR spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2003Klaus Belsner Abstract 3,-Acetyl-20(29)-lupene-24-oic acid (1) was isolated from the gum resin of Boswellia serrata. Its presence evidently suggests, that the oxidosqualene triterpene pathway of Boswellia serrata closely resembles the biosynthetic route already found in other plants. Complete 1H and 13C spectral assignments were derived from 1D and 2D NMR spectra. This is the first compound with the lupene backbone combining a 3,-hydroxy or 3,-acetyl group with the 24-carboxyl group, a configuration which is typical of the classical boswellic acids. Copyright © 2003 John Wiley & Sons, Ltd. [source] Structural determination and complete NMR spectral assignments of a new diterpenoid obtained from triptonide by biotransformationMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2003Lili Ning Abstract A new diterpenoid, 12,,13,-dihydroxytriptonide, was obtained from the transformed culture of triptonide by Catharanthus roseus cell suspension cultures. The complete 1H and 13C NMR assignments of the compound were carried out by using DEPT, COSY, HSQC, g-HMBC and NOESY techniques. Copyright © 2003 John Wiley & Sons, Ltd. [source] MassSieve: Panning MS/MS peptide data for proteinsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 16 2010Douglas J. Slotta Abstract We present MassSieve, a Java-based platform for visualization and parsimony analysis of single and comparative LC-MS/MS database search engine results. The success of mass spectrometric peptide sequence assignment algorithms has led to the need for a tool to merge and evaluate the increasing data set sizes that result from LC-MS/MS-based shotgun proteomic experiments. MassSieve supports reports from multiple search engines with differing search characteristics, which can increase peptide sequence coverage and/or identify conflicting or ambiguous spectral assignments. [source] | |||||||||||||