Heteronuclear single quantum correlation spectroscopy

L. Kay, P. Keifer, T. Saarinen, Pure absorption gradient enhanced heteronuclear single quantum correlation spectroscopy with improved sensitivity, J. Am. Chem. Soc. 114 (1992) 10663-10665. 

Conformations of mycothiol bimane (MSmB) were studied by H and 13C NMR using rotational nuclear Overhauser effect spectroscopy (ROESY) and heteronuclear single quantum correlation (HSQC) methods with expansions of the anomeric region <2003JOC3380>. NMR characterization of iV-acetyl-L-(Y)-cysteinyl monobimane and peracetylated MSmB was also published (Section 12.10.15.4) <2002JA3492>. 

No general studies have been carried out for these compounds, but there are several reports in which the stereochemistry of the final product has been elucidated by NOESY, correlation spectroscopy (COSY), or heteronuclear single quantum correlation (HSQC) experiments. For example, intensive NOESY experiments were used to establish the exact nature of each of the three cycloadducts 151a-c generated by the cycloaddition of a substituted nitrone to dimethyl (Z)-diethylenedicarboxylate <2000EJ03633>. 

A simple way of illustrating multidimensional NMR is through reference to hetero-nuclear correlation spectroscopy, in which two or more separate frequency dimensions are correlated with one another. For example, a particularly valuable 2D experiment is heteronuclear single quantum correlation (HSQC) spectroscopy, in which the resultant spectrum has two frequency axes, corresponding to and frequency dimensions, and one intensity axis. Analogous HSQC... 

Traditionally, homonuclear 2D double quantum filtered correlation spectroscopy (DQF-COSY) and total correlated spectroscopy (TOCSY) spectra are valuable in the identification of resonances of individual monosaccharide units. In the presence of small couplings, through space connectivities detected by NOESY/ROESY (nuclear Overhauser effect spectroscopy/ rotational nuclear Overhauser effect spectroscopy) experiments are also useful in completing the resonance assignment. When the H NMR spectra of complex oligosaccharides are too crowded to fully elucidate the structure by homonuclear correlation methods, it is efficient to use 2D heteronuclear correlation methods, such as heteronuclear single quantum correlation... 

G.P. Holland, B.R. Cherry, J.E. Jenkins, J.L. Yarger, Proton-detected heteronuclear single quantum correlation NMR spectroscopy in rigid solids with ultra- st MAS, J. Magn. Reson. 202 (2010) 64-71. 

M. Takasaki, K. Kimura, Y. Nakagawa, N. Sato, B. Bae, K. Miyatake, M. Watanabe, Complete NMR assignment of a stdfonated aromatic block copolymer via heter-onuclear single-quantum correlation, heteronuclear multiple-bond correlation and heteronuclear single-quantum correlation total correlation spectroscopy, Polym. J. 44 (2012) 845-849. 

HSQC HMQC Heteronuclear single-quantum/multiple-quantum correlation spectroscopy To elucidate structure of organic molecules To determine heteronuclear coupling connectivity... 

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 . 

Other strategies that show great promise in reducing NMR acquisition time utilise methods to obtain multiple sets of data from one experiment through a concept known as time-shared evolution. An example of this process that should find utility in natural products elucidation was demonstrated by a pulse sequence called CN-HMBC.93 Traditionally, a separate 13C-HMBC and 15N-HMBC were acquired independently. However, the CN-HMBC allows both 13C- and 15N-HMBC spectra to be obtained simultaneously. By acquiring both data sets simultaneously, an effective 50% time reduction can be achieved.93 This approach has also been demonstrated for a sensitivity-enhanced 2D HSQC-TOCSY (heteronuclear multiple bond correlation total correlation spectroscopy) and HSQMBC (heteronuclear single quantum... 

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 heteronuclear multiple-quantum correlation (HMQC) experiment is one of the two commonly employed proton-detected single-bond correlation experiments. Although this was suggested many years ago [1,2], the experiment lacked widespread use until a scheme was presented [3] that was able to overcome the technical difficulties associated with proton observation described above. Since then, and particularly since the advent of PFGs, the technique has come to dominate organic NMR spectroscopy. 

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