Home About us Contact
|
Home About us Contact | ||
|
|
||
Two-dimensional NMR Experiments (two-dimensional + nmr_experiment)
Selected AbstractsCharacterization of nonderivatized plant cell walls using high-resolution solution-state NMR spectroscopy,MAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2008Daniel J. Yelle Abstract A recently described plant cell wall dissolution system has been modified to use perdeuterated solvents to allow direct in-NMR-tube dissolution and high-resolution solution-state NMR of the whole cell wall without derivatization. Finely ground cell wall material dissolves in a solvent system containing dimethylsulfoxide- d6 and 1-methylimidazole- d6 in a ratio of 4:1 (v/v), keeping wood component structures mainly intact in their near-native state. Two-dimensional NMR experiments, using gradient-HSQC (heteronuclear single quantum coherence) 1-bond 13C1H correlation spectroscopy, on nonderivatized cell wall material from a representative gymnosperm pinus taeda (loblolly pine), an angiosperm Populus tremuloides (quaking aspen), and a herbaceous plant Hibiscus cannabinus (kenaf) demonstrate the efficacy of the system. We describe a method to synthesize 1-methylimidazole- d6 with a high degree of perdeuteration, thus allowing cell wall dissolution and NMR characterization of nonderivatized plant cell wall structures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Synthesis of rhodium(III) complexes with tris/tetrakis-benzimidazoles and benzothiazoles,quick identification of cyclometallation by nuclear magnetic resonance spectroscopyMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2009N. Chandrashekhar Abstract Reactions of rhodium(III) halides with multidentate N,S -heterocycles, (LH3) 1,3,5-tris(benzimidazolyl)benzene (L1H3; 1), 1,3,5-tris(N -methylbenzimidazolyl) benzene (L2H3; 2) and 1,3,5-tris(benzothiazolyl)benzene (L3H3; 3), in the molar ratio 1:1 in methanol,chloroform produced mononuclear cyclometallated products of the composition [RhX2(LH2)(H2O)] (X = Cl, Br, I; LH2 = L1H2, L2H2, L3H2). When the metal to ligand (1,3 or 1,2,4,5-tetrakis(benzothiazolyl)benzene [L4H2; 4]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh2Cl5(LH2)(H2O)3] (LH2 = L1H2, L2H2, L3H2) and [Rh2X4(L4)(H2O)2] (X = Cl, Br, I). Elemental analysis, IR and 1H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional 13C NMR spectra that showed a doublet around ,190 ppm. Cyclometallation was also detected by gradient-enhanced heteronuclear multiple bond correlation (g-HMBC) experiment that showed cross-peaks between the cyclometallated carbon and the central benzene ring protons of 1,3. Cyclometallation was substantiated by two-dimensional 1H1H correlated experiments (gradiant-correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and 1H13C single bond correlated two-dimensional NMR experiments (gradient-enhanced heteronuclear single quantum coherence). The 1H15N g-HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen. Copyright © 2009 John Wiley & Sons, Ltd. [source] Complete assignments of 1H and 13C NMR spectra of leucanthoside A, a new triterpenoid saponin from Cephalaria leucantha L.MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2006D. Go, evac Abstract Leucanthoside A, a new allose-containing triterpenoid saponin (1), was isolated from the aerial parts of Cephalaria leucantha L. Its structure was determined by electrospray ionization mass spectrometry and NMR spectroscopy. Complete assignments of the 1H and 13C NMR chemical shifts were achieved by two-dimensional NMR experiments: DQF-COSY, NOESY, TOCSY, HSQC, DINE-HSQC, HMBC, 13C- 1H 2D- J -resolved spectroscopy, and 1,1-ADEQUATE. Copyright © 2006 John Wiley & Sons, Ltd. [source] Characterization of reduced iso-,-acids derived from hops (Humulus lupulus) by NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2003Lars I. Nord Abstract Reduced forms of iso-,-acids (isohumulones), used in modern beer brewing were separated and characterized by 1H and 13C NMR spectroscopy. Components from mixtures of rho-iso-,-acids, tetrahydro-iso-,-acids, and hexahydro-iso-,-acids were isolated using high-performance liquid chromatography (HPLC) and analyzed by use of one- and two-dimensional NMR experiments. The data presented assign the identities of the main peaks in the HPLC traces for the reduced iso-,-acids. Previous tentative assignments regarding the cis and trans configurations and the structures of the acyl residues of the reduced iso-,-acids were confirmed and extensive NMR assignments were made. Furthermore, the previously unknown stereochemistry in the C-4 side-chain of the rho- and hexahydro-iso-,-acids was assigned. Copyright © 2003 John Wiley & Sons, Ltd. [source] Synthesis of benzo[b][1,4]thiazepines by the reaction of 3-aryl-1-(3-coumarinyl)propen-1-ones with 2-aminothiophenol,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2007Albert Lévai 3-(2-Aryl-2,3-dihydro-benzo[b][1,4]thiazepin-4-yl)chromen-2-ones (2a, e, f) and (Z)-3-(2,3-dihydro-2-arylbenzo[b][1,4]thiazepin-4(5H)-ylidene)chroman-2-ones (3a-f) have been synthesized by the reaction of 3-aryl-1-(3-coumarinyl)propen-1-ones (1a-f) with 2-aminothiophenol in a hot mixture of toluene and acetic acid. Structures of all new compounds and their complete 1H and 13C assignments were achieved applying different one- and two-dimensional nmr experiments in combination with various spectroscopic techniques. [source] | ||||||||||