Heteronuclear multiple-quantum spectroscopy

Tolman, J. R., Chung, J. and Prestegard, J. H. Pure-phase heteronuclear multiple-quantum spectroscopy using field gradient selection. J. Magn. Reson. 98 462—467, 1992. 

Nuclear Overhauser effect (NOE) difference measurements were used to assign structure 79 for the product of reaction of diphenylnitrile imine with 5-ethylsulfonyl-2-methyl(27/)pyridazinone. Thus in the H NMR spectrum the ot/, o-protons of the arylhydrazino moiety (which were identified by two-dimensional heteronuclear multiple quantum correlation (2-D HMQC) spectroscopy) were shown in differential NOE (DNOE) experiment to be significantly enhanced on irradiation of pyridazine hydrogen H-7, proving their steric proximity <2000JST13>. 

The vast literature associated with flavanoid chemistry precludes a discussion here but two valuable reviews have been published. The first reviews a number of spectroscopic techniques used for flavonoid analysis, with a strong emphasis on NMR spectroscopy (plus also mass spectrometry, vibrational spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, X-ray crystallography, and circular dichrosim (CD)) . The second review deals with NMR methods that have been successful in the characterization of phenolic acids and flavonoids from plant extracts that have not been separated or isolated as single components. The emphasis of the article is 2-D NMR methodology and a variety of experiments such as total correlated spectroscopy (TOCSY), COSY, nuclear Overhauser enhancement spectroscopy (NOESY) and heteronuclear multiple quantum correlation (HMQC) are discussed . 

By way of example, useful 2-D techniques are homonuclear correlation spectroscopy (COSY), total correlation spectroscopy (TOCSY), heteronuclear multiple quantum coherence (HMQC) spectroscopy, and heteronuclear multiple quantum coherence/total... 

A complex, multiply bridged 1,2,3,4-adduct of C60 (168) (Scheme 1.11) including a noninherently chiral addition pattern as well as a multitude of stereogenic centers in the addend moiety was obtained in a tandem reaction between the alkaloid scandine and Ceo-324 The sequence included a photoin-duced addition of the tertiary amine subunit of the alkaloid and a [2 + 2] cycloaddition of its vinyl group to the adjacent intrahexagonal formal double bond of the fullerene. The structural elucidation included 1H-1 H COSY-, HMQC- (heteronuclear multiple quantum coherence), HMBC-, and ROESY-(rotating frame Overhauser enhancement spectroscopy) NMR experiments and... 

The structural connectivity derived from examination of the 111, 13C/DEPT, DQF-COSY, HMQC, and HMBC data (DEPT = distortionless enhancement by polarization transfer DQF = double quantum filtering COSY = correlation spectroscopy HMQC = heteronuclear multiple quantum correlation HMBC = heteronuclear multiple bond correlation) resulted in global reevaluation of sclerophytin B structure and demonstrated that this compound and the related alcohol are not composed of two ether bridges as in the originally formulated structure 37, but share the structural features depicted as 38 <20000L1879>. Comparison of 13C and 111 NMR data of Norte s... 

DFT = density functional theory HMQC = heteronuclear multiple quantum coherence SOMO = singly occupied molecular orbital PES = photoelectron spectroscopy Cl = configuration interaction LUMO = lowest unoccupied molecular orbital HOMO = highest occupied molecular orbital TLC = thin layer chromatography. 

Heteronuclear multiple-quantum correlation Experiment for tailored correlation spectroscopy of H and H resonances in peptides and proteins Homonuclear Hartmann-Hahn spectroscopy Heteronuclear quadruple-quantum coherence Heteronuelear triple-quantum coherence Heteronuclear single-quantum coherence TOCSY sequences developed at the Indian Institute of Chemical Technology Insensitive nucleus enhancement by polarization transfer... 

The structures of the natural products, ceratospongamides from marine red alga (Rhodophyta) Ceratodictyon spongiosum, which each consist of two L-phenylalanine residues, one (L-isoleucine)-methyloxazoline residue, one L-proline residue, and one (L-proline)thiazole residue, were established through extensive NMR experiments, including heteronuclear multiple quantum correlation total correlated spectroscopy (HMQC-TOCSY), and... 

HMQC Heteronuclear Multiple Quantum Correlation spectroscopy... 

HETERONUCLEAR MULTIPLE-QUANTUM COHERENCE (HMQC) SPECTROSCOPY... 

For smaller quantities of compounds more sensitive inverse detected techniques are available, such as HMQC ( IH-I C one bond correlation via heteronuclear multiple quantum coherence, analogous to HETCOR) and HMBC (proton detected heteronuclear multiple bond correlation spectroscopy) (15). The last provide, in addition to the intraresidue multiple bond correlations, interresidue correlations between the anomeric carbon and the aglycone protons.We follow this general strategy for the structural determination of tri terpenoid saponins of Bupleurum fruticosum (16) andArdisia japonica (9). 

Field desorption mass spectrometry Heteronuclear multiple-quantum correlation Heteronuclear multiple-quantum correlation Homonuclear Hartmann-Hash spectroscopy High performance liquid chromatography High resolution electrospray ionization High resolution first atom bombardment massspectrometry... 

C NMR was a reliable source of detection and identification of carbon nuclei in the saccharide molecule. However, greater quantities were requiredfor ID experiments as compared with H NMR spectroscopy and often extended periods for acquisition (sometimes 3 days) were required. The H- C heteronuclear multiple quantum correlation (HMQC) was one experiment that allowed the assigiunent of carbon resonances, by correlation with their proton nuclei, and where smaller quantities were used. A conscious ID P NMR investigation quickly revealed the presence of phosphate or a 2-aminoethyl phosphate unit in the core OS. 2D H-3 P HMBC NMR spectroscopy was a reliable method for efficient detection and sometimes placement of the phosphate substituents. 

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