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1.
The complete assignment of 19F, 1H and 13C NMR spectra for a monosubstituted octafluoro[2.2]paracyclophane derivative is described for the first time. The unambiguous assignments were achieved through the combination of 19F--1H HOESY, 1H COSY and 19F COSY techniques and then further confirmed employing a complementary approach using a Karplus-dependent 3JCF interaction. Interesting aspects of the coupling patterns for various JHH, JHF, JCF and JFF interactions are also discussed. 相似文献
2.
Marino Vega‐Vazquez Juan Carlos Cobas Manuel Martin‐Pastor 《Magnetic resonance in chemistry : MRC》2010,48(10):749-752
A parallel localized spectroscopy (PALSY) method is presented to speed up the acquisition of multidimensional NMR (nD) spectra. The sample is virtually divided into a discrete number of nonoverlapping slices that relax independently during consecutive scans of the experiment, affording a substantial reduction in the interscan relaxation delay and the total experiment time. PALSY was tested for the acquisition of three experiments 2D COSY, 2D DQF‐COSY and 2D TQF‐COSY in parallel, affording a time‐saving factor of 3–4. Some unique advantages are that the achievable resolution in any dimension is not compromised in any way: it uses conventional NMR data processing, it is not prone to generate spectral artifacts, and once calibrated, it can be used routinely with these and other combinations of NMR spectra. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
对一些二维NMR技术,例如^1H-^1H相关谱(^1H-^1H COSY),^1H-^13C杂核化学位移相关谱(^1H-C^13 COSY),奥氏核效应交换相关谱(NOESY)作了介绍,列举了一些典型谱图。 相似文献
4.
《Chemie in Unserer Zeit》2017,51(4):264-271
The present state of the routine 2D COSY‐ and HSQC‐NMR spectroscopy is reported. After a short introduction into the basic theory of 2D NMR the pulse sequences of COSY and HSQC are explained. Using an example from natural product chemistry the procedures during the analysis of these 2D NMR spectra are demonstrated. 相似文献
5.
Martin GE Hilton BD Blinov KA Williams AJ 《Magnetic resonance in chemistry : MRC》2008,46(11):997-1002
Long-range homonuclear coupling pathways can be observed in COSY or GCOSY spectra by the acquisition of spectra with larger numbers of increments of the evolution period, t(1), than would normally be used. Alternatively, covariance processing of COSY-type spectra acquired with modest numbers of t(1) increments, allows the observation of multistage correlations. In this work results obtained from covariance-processed GCOSY spectra are fully analyzed and compared to normally processed COSY and 80 ms TOCSY spectra. Multistage or 'RCOSY-type' correlations are observed when remote protons both exhibit correlations to the same coupling partner e.g. A --> B and B --> C gives rise to an A --> C correlation. In the strict sense, RCOSY-type responses are artifacts albeit providing useful information. Nonbeneficial artifact correlations are observed when protons couple to other protons that overlap or partially overlap. The origin of artifact responses is also analyzed. 相似文献
6.
The practical aspects of some NMR experiments designed for the simultaneous acquisition of 2D COSY and 2D TOCSY spectra are presented and discussed. Several techniques involving afterglow-based, coherence transfer pathway (CTP)-based, and NMR by Ordered Acquisition using 1H-detection (NOAH)-based strategies for the collection of different free-induction signal decays (FIDs) within the same scan are evaluated and compared. These methods offer a faster recording of these spectra in small-molecule NMR when sensitivity is not a limiting factor, with a reduction in spectrometer time about 45–60% when compared with the conventional sequential acquisition of the parent experiments. It is also shown how the optimized design of an extended three-FID approach yields one COSY and two TOCSY spectra simultaneously by combining CTP and NOAH principles in the same experiment, affording substantial sensitivity enhancements per time unit. 相似文献
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苷类化合物的糖体质子大多相互有自旋偶合作用,构成一个复杂的自旋系统。糖体端基质子(H-1)NMR 信号大多为双峰,出现在较 相似文献
9.
Li X McCord EF Baiagern S Fox P Howell JL Sahoo SK Rinaldi PL 《Magnetic resonance in chemistry : MRC》2011,49(7):413-424
Multiple two‐dimensional nuclear magnetic resonance (2D‐NMR) techniques have been used to study the structures of Krytox® perfluoro(polyalkyl ether) and its mechanism of polymerization. Model compound K4, containing four Krytox® fluoropolymer repeat units, was analyzed to interpret the multiplet patterns in the NMR spectra from the polymer model. 19F {13C}‐Heteronuclear single‐quantum correlation experiments, performed with delays optimized for 1JCF and 2JCF, provided spectra that permitted identification of resonances from individual monomer units. Selective, 19F‐19F COSY 2D‐NMR experiments were performed with different excitation regions; these experiments were combined with selective inversion pulses to remove 19F‐19F J couplings in the f1 dimension. The resulting COSY spectra were greatly simplified compared with standard 19F‐19F COSY spectra, which are too complicated to interpret. They give information regarding the attachments of monomer units and also provide insights into the nature of the stereoisomers that might be present in the polymer. Both infrared and NMR spectra show peaks identifying chain end structures. With the help of these studies, resonances can be assigned, and the average number of repeat units in the polymer chain can be calculated based on the assignments obtained. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
10.
A selection of mono‐ and pseudo ortho di‐substituted octafluoro[2.2]paracyclophane derivatives were analyzed using 19F‐1H HOESY, 1H COSY and 19F COSY techniques. This resulted in the unambiguous assignment of the 19F and 1H NMR resonances, and also revealed interesting solvent effects and noteworthy coupling patterns for various JHH, JHF, and JFF interactions, including observable through bond 7JFF and 8JFF couplings. For the four mono‐substituted derivatives, the assignments were achieved through the combination of 19F‐1H HOESY, 1H COSY and 19F COSY techniques. The C2 symmetry of the six pseudo ortho di‐substituted derivatives that were examined produced simplified spectra, and careful inspection of the characteristic 1H coupling patterns led to the assignment of 1H signals. Therefore only 19F‐1H HOESY experiments were required to complete the assignments for those molecules. Refinements and alternative strategies for previous protocols are presented for the molecules that were less responsive to nuclear Overhauser effect (nOe) experiments. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
11.
Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed. 相似文献
12.
Silver triflate [AgOTf] assisted de‐bromination gives [Ni(dppm/dppe/(PPh3)2) (OTf)2], which on reaction with 4,4′‐bpy and gold(I) phosphines in dichloromethane medium by the self assemble technique leads to [{(L)Ni}{(4,4‐bpy)Au(PPh3)}2](OTf)4, ( 1,2,3 ) [{(L)Ni(4,4‐bpy)}4](OTf)8, ( 4,5,6 ) [L = dppm/dppe/(PPh3)2 = diphenyl phosphino‐methane, ‐ethane, bis‐triphenylphosphine, OSO2CF3 is the triflate anion]. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. Ir spectra of the complexes show ‐C=C‐, ‐C=N‐, as well as phosphine stretching. The 1H NMR spectra as well as 31P (1H)NMR suggest solution stereochemistry, proton movement, and phosphorus proton interaction. Considering all the moieties, there are a lot of carbon atoms in the molecule reflected by the 13C NMR spectrum. In the 1H‐1H COSY spectrum of the present complexes and contour peaks in the 1H?13C HMQC spectrum, we assign the solution structure and stereoretentive transformation in each step. 相似文献
13.
Judith Schlagnitweit Gerhard Zuckerstätter Norbert Müller 《Magnetic resonance in chemistry : MRC》2010,48(1):1-8
Standard phase cycled NMR pulse sequences were generalized such that for each individual step of the pulse phase cycle the free induction decay is stored separately without phase correction. This is in contrast to the usual practice, where pulse responses are phase shifted immediately (by applying a ‘receiver phase’) and co‐added as they are stored. The approach used here allows one to extract different types of NMR information, which are usually referred to as different ‘experiments’, from the same raw data set a posteriori by using complex linear combinations. Storing the free induction decays of individual phase cycle steps separately and using specific linear combinations of these data to obtain a particular type of information increase the overall efficiency of a given set of NMR experiments substantially, because all information can be derived from a single multiplexed data set. This ‘super‐experiment’ requires only as much time as the most complex of the derived specific experiments alone. The principle of this multipurpose approach was demonstrated by performing different multiple‐quantum filtered COSY experiments. It also becomes possible to generate linear combinations, which differ from the conventionally acquired spectra a posteriori. For example, we implemented diagonal peak reduction by using zero‐ and single‐quantum filtered COSY contributions without requiring additional experiment time. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Luísa R. Carvalho Marta C. Corvo Ramu Enugala M. Manuel B. Marques Eurico J. Cabrita 《Magnetic resonance in chemistry : MRC》2010,48(4):323-330
The solid‐phase synthesis (SPS) of a structurally complex glycopeptide, using Sieber amide resin, was monitored by high resolution magic angle spinning NMR, demonstrating the further application of this technique. A synthetic peptidoglycan derivative, a precursor of a biologically active PGN, known to be involved in the cellular recognition, was prepared by SPS. The synthesis involved the preparation of an N‐alloc glucosamine moiety and the synthesis of a simple amino acid sequence L ‐Ala‐D ‐Glu‐L ‐Lys‐D ‐Ala‐D ‐Ala. Last step consisted the coupling, on solid‐phase, of the protected muramyl unit to the peptide chain. Proton spectra with good suppression of the polystyrene signals in swollen resin samples were obtained in DMF‐d7 as a solvent and by using a nonselective 1D TOCSY/DIPSI‐2 scheme, thus allowing to follow the SPS without losses of compound and cleavage from the resin. The assignment of the proton spectra of the resin‐bound amino acid sequence and of the bound glycopeptide was achieved through the combination of MAS COSY, TOCSY and NOESY. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Seroka P Płosiński M Czub J Sowiński P Pawlak J 《Magnetic resonance in chemistry : MRC》2006,44(2):132-138
D-Glucose, D-mannose and L-rhamnose were reacted with a racemic mixture of 2-butanol, and the resulting alpha-glycosides were analyzed by 1H NMR with COSY and NOESY experiments. Conformational analysis of alpha-glycosidic bonds performed with molecular modeling and appropriate heteronuclear long-range coupling measurements and combined with analysis of dipolar couplings observed in NOESY spectra allowed the assignment of absolute configuration in the aglycones of elucidated alpha-glycosides. 相似文献
17.
Two-dimensional (2D) 59Co correlation spectroscopy (COSY)/double-quantum-filtered (DQF)COSY experiments are reported for three tetrahedral mixed-metal clusters HFeCo3(CO)11L with L = PPh3, P(OMe)3, and PCy3 (Cy = cyclohexyl) in which the L-substituted Co center is chemically different from the other two. The 2D 59Co COSY and DQFCOSY NMR spectra of these clusters in solution prove the existence of a scalar coupling constant between the 59Co nuclei. To determine this value for each cluster, 2D 59Co COSY and DQFCOSY NMR spectra have been simulated by numerical density-matrix calculations. The predicted spectra mimic well the features of the experimental spectra if a scalar coupling is introduced between the Co nuclei. It was initially observed that the scalar coupling constants between the Co nuclei obtained from the 2D COSY and DQFCOSY NMR spectra differed significantly. In contrast to the 2D COSY spectra, the diagonal and cross peaks are of comparable intensity in the 2D DQFCOSY spectra, which leads to a considerable increase in the accuracy of the determination of the scalar coupling constant. 相似文献
18.
《Magnetic resonance in chemistry : MRC》2003,41(11):908-920
Structure elucidation of compounds in the benzisoxazole series ( 1 – 6 ) and naphtho[1,2‐d][1,3]‐ ( 7 – 10 ) and phenanthro[9,10‐d][1,3]oxazole ( 11 – 14 ) series was accomplished using extensive 2D NMR spectroscopic studies including 1H–1H COSY, long‐ range 1H–1H COSY, 1H–13C COSY, gHMQC, gHMBC and gHMQC‐TOCSY experiments. The distinction between oxazole and isoxazole rings was made on the basis of the magnitude of heteronuclear one‐bond 1JC2, H2 (or 1JC3, H3) coupling constants. Complete analysis of the 1H NMR spectra of 11 – 14 was achieved by iterative calculations. Gradient selected gHMQC‐TOCSY spectra of phenanthro[9,10‐d][1,3]oxazoles 11 – 14 were obtained at different mixing times (12, 24, 36, 48 and 80 ms) to identify the spin system where the protons of phenanthrene ring at H‐5, H‐6 and at H‐9 and H‐7 and H‐8 were highly overlapping. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
19.
Meerakhan Pathan Benoît Charrier Illa Tea Serge Akoka Patrick Giraudeau 《Magnetic resonance in chemistry : MRC》2013,51(3):168-175
Ultrafast (UF) 2D NMR is a very promising methodology enabling the acquisition of 2D spectra in a single scan. In the last few years, the analytical performance of UF 2D NMR has been highly increased, consequently maximizing its range of applications. However, its implementation and use by non‐specialists are far from being straightforward, because of the specific acquisition and processing procedures and parameters characterizing UF NMR. To make this methodology implementable and applicable by non‐specialists, we developed a simple routine capable of translating conventional parameters (spectral widths and transmitter frequencies) into specific UF parameters (gradient and chirp pulse parameters). This macro was subsequently implemented in a Web page, which is available for external users. Although the algorithm was designed for two widely used 2D experiments, COSY and HSQC, it can easily be extended to any other pulse sequence. The robustness of this routine was verified successfully on a variety of small molecules. We believe that this tool will eliminate much of the technical difficulties related to UF 2D NMR and will make the technique accessible to a wider audience of organic and analytical chemists. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
20.
The interaction of proline with self-assembled monolayers (SAMs) of l-glutathione (gamma-glu-cys-gly) on gold was investigated by a combination of attenuated total reflection (ATR-IR) infrared and modulation excitation spectroscopy (MES). The latter technique makes use of phase-sensitive detection of periodically varying signals and allows discrimination between species with different kinetics such as dissolved proline and adsorbed molecules. By applying a convection-diffusion model coupled to adsorption and desorption, it was possible to extract relative adsorption and desorption rates from the experimental data for the two enantiomers of proline, fully accounting for mass transport within the flow-through cell. The results show that, in particular, the desorption kinetics is different for the two enantiomers. Therefore, the l-glutathione SAM can discriminate between enantiomers, d-proline being stronger bound. The IR spectra reveal that upon interaction with proline the adsorbed l-glutathione is protonated at the gly part of the molecule, which, in the absence of proline, is bound to the gold surface as carboxylate. The observed protonation of adsorbed l-glutathione upon interaction with proline goes along with a structural change of the former, which seems to play an important role for enantiodiscrimination. 相似文献