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Isomeric Compounds (isomeric + compound)
Selected AbstractsThree isomeric 1-(2-chloronicotinoyl)-2-(nitrophenyl)hydrazines, including three polymorphs of 1-(2-chloronicotinoyl)-2-(2-nitrophenyl)hydrazine: hydrogen-bonded supramolecular structures in two and three dimensionsACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2007Solange M. S. V. Wardell 1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N,H,O and two C,H,O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N,H,O, C,H,N and C,H,O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N,H,O, one N,H,N and three C,H,O hydrogen bonds, and an aromatic ,,, stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N,H,O, N,H,N and C,H,O types, weakly augmented by a ,,, stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N,H,O, N,H,N and C,H,O types. [source] Novel tetracyclic imidazole derivatives: Synthesis, dynamic NMR study, and anti-inflammatory evaluationJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2010Renata Rup A series of tetracyclic imidazole derivatives 9a,9v and 10a,10h are prepared by multistep route starting from the known tricyclic diketones 2a,2d. Intermediary dibenzooxepin[4,5- d]imidazoles (3a, 3c) and dibenzothiepin[4,5- d]imidazoles (3b, 3d) are N -protected to 4e, 4f and to the isomeric compounds 5a, 5b and 6a, 6b. The isomeric compounds 5 and 6 are separated. Compounds 4, 5, and 6 are formylated at C(2) to afford 7a,7j. In the last steps, aldehyde group is reduced, then alkylated to the two sets of isomeric ,-dimethylaminoalkyl derivatives 9a,9v. N -deprotection of 9i,9v led to the compounds 10a,10h. Assignment of the syn/anti structure to 5a and 6a was supported by 1D selective ROESY NMR spectra, whereas conformational mobility for the selected representatives 8a and 8b is studied by dynamic NMR. Activation energies (energy barriers for interconversion) are determined to be ,11.5 and 16.2 kcal/mol, respectively. A series of derivatives 9 and 10 were tested in vitro for their anti-inflammatory activity. J. Heterocyclic Chem., (2010). [source] Evaluation of glycosylation and malonylation patterns in flavonoid glycosides during LC/MS/MS metabolite profilingJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2008P. Kachlicki Abstract Flavonoid conjugates constitute several classes of plant phenolic secondary metabolites including many isomeric compounds differing in the hydroxylation pattern and substitution of their rings with different groups such as alkyls, acyls or sugars. These compounds occur in plant tissues mainly as glycosides and in many cases it is necessary to have reliable and detailed information concerning the structure of these natural products. Our results were obtained using leaf extracts of Arabidopsis thaliana and Lupinus angustifolius in which different glycosides of flavones, flavonols and isoflavones are present. Analysis of collision-induced dissociation (CID)/MS/MS spectra of protonated [M + H]+, sodiated [M + Na]+ or deprotonated [M , H], molecules recorded during HPLC runs may bring needed information in this respect. However, registration of mass spectra of [M + Na]+ ions with a good efficiency is possible only after post-column addition of a sodium acetate solution to the LC column eluate. The retention of sodium cation on the saccharidic parts of the molecule is observed after the CID fragmentation. In many cases, the location of this cation on the glycan attached to C-3 hydroxyl group of flavonol led to assignment of its structure. Additionally, the determination of the structure of the aglycone and of the sequence of the glycan part was made possible through the CID data obtained from the [M + H]+ and [M , H], ions. CID spectra show a different order of sugar elimination from hydroxyl groups at C-3 and C-7 in flavonol glycosides isolated from A. thaliana leaves and give sufficient information to discriminate flavonoid O-diglycosides from flavonoid di-O-glycosides. Copyright © 2007 John Wiley & Sons, Ltd. [source] Distinguishing N -oxide and hydroxyl compounds: impact of heated capillary/heated ion transfer tube in inducing atmospheric pressure ionization source decompositionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Dilrukshi M. Peiris Abstract In the pharmaceutical industry, a higher attrition rate during the drug discovery process means a lower drug failure rate in the later stages. This translates into shorter drug development time and reduced cost for bringing a drug to market. Over the past few years, analytical strategies based on liquid chromatography/mass spectrometry (LC/MS) have gone through revolutionary changes and presently accommodate most of the needs of the pharmaceutical industry. Among these LC/MS techniques, collision induced dissociation (CID) or tandem mass spectrometry (MS/MS and MSn) techniques have been widely used to identify unknown compounds and characterize metabolites. MS/MS methods are generally ineffective for distinguishing isomeric compounds such as metabolites involving oxygenation of carbon or nitrogen atoms. Most recently, atmospheric pressure ionization (API) source decomposition methods have been shown to aid in the mass spectral distinction of isomeric oxygenated (N -oxide vs hydroxyl) products/metabolites. In previous studies, experiments were conducted using mass spectrometers equipped with a heated capillary interface between the mass analyzer and the ionization source. In the present study, we investigated the impact of the length of a heated capillary or heated ion transfer tube (a newer version of the heated capillary designed for accommodating orthogonal API source design) in inducing for-API source deoxygenation that allows the distinction of N -oxide from hydroxyl compounds. 8-Hydroxyquinoline (HO-Q), quinoline- N -oxide (Q-NO) and 8-hydroxyquinoline- N -oxide (HO-Q-NO) were used as model compounds on three different mass spectrometers (LCQ Deca, LCQ Advantage and TSQ Quantum). Irrespective of heated capillary or ion transfer tube length, N -oxides from this class of compounds underwent predominantly deoxygenation decomposition under atmospheric pressure chemical ionization conditions and the abundance of the diagnostic [M + H , O]+ ions increased with increasing vaporizer temperature. Furthermore, the results suggest that in API source decompostion methods described in this paper can be conducted using mass spectrometers with non-heated capillary or ion transfer tube API interfaces. Because N-oxides can undergo in-source decomposition and interfere with quantitation experiments, particular attention should be paid when developing API based bioanalytical methods. Copyright © 2004 John Wiley & Sons, Ltd. [source] Redox reactions of copper(II) upon electrospray ionization in the presence of acridine ligands with an amide side chainJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2009Aura Tintaru Abstract The complexation of copper(II) to acridine derivatives has been studied by means of electrospray ionization (ESI) mass spectrometry. Under soft conditions of ionization, the ESI mass spectra of methanolic solutions of copper(II) chloride and the acridine ligands show abundant signals of the mononuclear complexes formed from the metal and ligand. Depending on the position of the N -benzoylamino substituent in the acridinic heterocycle, however, the copper atom involved in the complexation process adopts different oxidation states in the resulting cations. Hence, the metal is reduced to copper(I) in the monocationic complex with the compound substituted in position 2, whereas it keeps its divalent state in the monocation formed with the compound substituted in position 4. As a consequence, the regioisomers lead to monocations with different masses in the ESI spectra. In order to understand this unusual behavior of two isomeric compounds, additional experiments have been performed with quinoline as a model. Copyright © 2008 John Wiley & Sons, Ltd. [source] Identification of isomeric dicaffeoylquinic acids from Eleutherococcus senticosus using HPLC-ESI/TOF/MS and 1H-NMR methodsPHYTOCHEMICAL ANALYSIS, Issue 6 2002Ari Tolonen Abstract Liquid chromatography,electrospray time-of-flight mass spectrometry (HPLC-ESI/TOF/MS) and a novel NMR technique, developed to maximise the sensitivity obtained from the standard NMR spectrometer, have been applied to the identification of the phenolic constituents of Eleutherococcus senticosus. In addition, molecular modelling and dihedral bond angle calculations based on the vicinal 3JHH -coupling constants have been used in the unambiguous assignment of signals in the 1H-NMR spectra. 5,- O -Caffeoylquinic acid and three isomeric compounds, 1,,5,- O -dicaffeoylquinic acid, 3,,5,- O -dicaffeoylquinic acid and 4,,5,- O -dicaffeoylquinic acid, have been isolated and identified from a sample. The isolation and structure determination of the latter two compounds are reported for the first time from this plant. Copyright © 2002 John Wiley & Sons, Ltd. [source] Electron ionization mass spectra of phosphorus-containing heterocycles.RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006The electron ionization mass spectra of cis - and trans -fused 1,2,3,4,4a,5,6,7,8,8a-decahydro-1,3,2-benzodiazaphosphinine 2-oxides (1,17) were recorded, and the fragmentation pathways were established and compared with those of 1,4,4a,5,6,7,8,8a-octahydro-2H -3,1,2-benzoxazaphosphinine 2-oxides. In general, the mass spectral behaviors of the isomeric compounds were very similar and it was mostly impossible to differentiate them from each other on the basis of the relative abundances of their characteristic fragment ions. The compounds in which R2,=,Ph or OPh exhibited a series of common fragments, e.g. [R2H]+, R2PONHR1(3)+, [M,C3H7]+ and [M,C4H9]+, the latter two ions being present in the spectra of only two of the derivatives with an N(CH2CH2Cl)2 substituent on the P atom. When R2,=,Ph, numerous other alkyl radicals, alkenes and a cycloalkane were also ejected and these compounds also lost NH2, NH3, CH3N, CH4N or CH3NH2. The compounds with an N(CH2CH2Cl)2 substituent on the P atom most closely resembled their 3,1,2-O,N,P analogs in respect of the dominant role of this substituent. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hydrogen-bonded structures of the isomeric compounds of quinoline with 2-chloro-5-nitrobenzoic acid, 3-chloro-2-nitrobenzoic acid, 4-chloro-2-nitrobenzoic acid and 5-chloro-2-nitrobenzoic acidACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009Kazuma Gotoh The structures of four isomeric compounds, all C7H4ClNO4·C9H7N, of quinoline with chloro- and nitro-substituted benzoic acid, namely, 2-chloro-5-nitrobenzoic acid,quinoline (1/1), (I), 3-chloro-2-nitrobenzoic acid,quinoline (1/1), (II), 4-chloro-2-nitrobenzoic acid,quinoline (1/1), (III), and 5-chloro-2-nitrobenzoic acid,quinoline (1/1), (IV), have been determined at 185,K. In each compound, a short hydrogen bond is observed between the pyridine N atom and a carboxyl O atom. The N...O distances are 2.6476,(13), 2.5610,(13), 2.5569,(12) and 2.5429,(12),Ĺ for (I), (II), (III) and (IV), respectively. Although in (I) the H atom in the hydrogen bond is located at the O site, in (II), (III) and (IV) the H atom is disordered in the hydrogen bond over two positions with (N site):(O site) occupancies of 0.39,(3):0.61,(3), 0.47,(3):0.53,(3) and 0.65,(3):0.35,(3), respectively. [source] Three substituted (Z)-5-benzylidene-2-thioxothiazolidin-4-ones: hydrogen-bonded dimers that can be effectively isolated or linked into chains either by aromatic ,,, stacking interactions or by dipolar carbonyl,carbonyl interactionsACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2006Paula Delgado In each of the isomeric compounds (Z)-5-(2-fluorobenzylidene)-2-thioxothiazolidin-4-one, C10H6FNOS2, (I), and (Z)-5-(4-fluorobenzylidene)-2-thioxothiazolidin-4-one, C10H6FNOS2, (II), there is a very wide C,C,C angle (ca 130°) at the methine C atom linking the two rings. In each isomer, paired N,H,O hydrogen bonds link the molecules into centrosymmetric R22(8) dimers; the hydrogen-bonded dimers are linked into chains by an aromatic ,,, stacking interaction in isomer (I) and by an antiparallel dipolar carbonyl,carbonyl interaction in isomer (II). (Z)-5-(3,4,5-Trimethoxybenzylidene)-2-thioxothiazolidin-4-one, C13H13NO4S2, (III), which crystallizes with Z, = 2 in the space group P, shows the same very wide angle at the bridging methine C atom; the two independent molecules are linked into an isolated dimer having no crystallographic symmetry. [source] Two one-dimensional zinc(II) coordination polymers: catena -poly[[bis(pentane-2,4-dionato-,2O,O,)zinc]-,-1,4-bis(x -pyridyl)-2,3-diazabuta-1,3-diene] (x = 3, 4)ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2006Juan Granifo The structures of the two title isomeric compounds, [Zn(C5H7O2)2(C12H10N4)]n, are built up around two non-equivalent symmetry centres, one of them at the cation position and the other bisecting the N,N bond in the 1,4-bis(3/4-pyridyl)-2,3-diazabuta-1,3-diene (3pdb/4pdb) units. Both Zn cations have the Zn atoms an inversion centres and present tetragonally distorted octahedral environments, but differences in their linkage through the 3pdb and 4pdb ligands give rise to differently shaped weakly interacting chains. [source] High-performance liquid chromatography and LC-ESI-MS method for identification and quantification of two isomeric polyisoprenylated benzophenones isoxanthochymol and camboginol in different extracts of Garcinia speciesBIOMEDICAL CHROMATOGRAPHY, Issue 8 2009Satyanshu Kumar Abstract A rapid, sensitive and simple reverse-phase high-performance liquid chromatography,electrospray ionization mass spectrometric method has been developed for the identification and quantification of two isomeric polyisoprenylated benzophenones, isoxanthochymol and camboginol, in the extracts of the stem bark, seeds and seed pericarps of Garcinia indica and in the fruit rinds of Garcinia cambogia. The separation of isoxanthochymol and camboginol was achieved on a Perkin Elmer RP8 column (10 × 2.1 mm with 5.0 µm particle size) using a solvent system consisting of a mixture of acetonitrile,water (80:20, v/v) and methanol,acetic acid (99.0:1.0, v/v) as a mobile phase in a gradient elution mode. The limits of detection and quantification were 5 and 10 µg/mL for isoxanthochymol and 50 and 100 µg/mL for camboginol, respectively. The intra- and inter-day precisions were 2.34 and 3.41% for isoxanthochymol and 3.35 and 3.66% for camboginol. The identity of the two isomeric compounds in the samples was determined on a triple quadrupole mass spectrometer with ESI interface operating in the negative ion mode. The method was used to identify and quantify isoxanthochymol and camboginol in the different extracts of two Garcinia species, Garcinia indica and Garcinia cambogia. Copyright © 2009 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography and LC-ESI-MS method for the identification and quantification of two biologically active isomeric coumarinolignoids cleomiscosin A and cleomiscosin B in different extracts of Cleome viscosaBIOMEDICAL CHROMATOGRAPHY, Issue 12 2008Sunil K. Chattopadhyay Abstract A rapid, sensitive and simple reverse-phase high-performance liquid chromatographic,electrospray ionization,mass spectrometry method for simultaneous determination of cleomiscosin A and cleomiscosin B has been developed and validated. The isomeric coumarinolignoids cleomiscosin A (1) and cleomiscosin B (2) were separated on a Waters symmetry C18 column with a solvent system composed of acetonitrile,methanol (1:2) and acetic acid,water (0.5 : 99.5) in a gradient elution mode. The absorption at 326 nm was chosen as the measuring wavelength in which resolution and baseline separation of compounds 1 and 2 could be obtained. The identity of the two isomeric compounds 1 and 2 in the samples were determined on a triple quadrupole mass spectrometer with ESI interface operating in the positive mode. Calibration curves were linear (r2 > 0.993) over the concentration range 20,200 µg/mL for cleomiscosin A and 10,200 µg/mL for cleomiscosin B with acceptable accuracy and precision, respectively. The intra-day and inter-day precision were 1.13 and 0.82% for cleomiscosin A and 1.78 and 1.28% for cleomiscosin B, respectively. The validated method was successfully applied for the analysis of the above two compounds in different extracts of Cleome viscosa. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||