Shift correlation, heteronuclear long-range

COSY = homonuclear chemical shift correlation spectroscopy NOESY = 2D nuclear Overhauser effect (NOE) spectroscopy HMQC = heteronuclear mulltiple-quantum coherence RELAY = relayed coherence transfer COLOC = correlation via long-range coupling HMBC = heteronuclear long-range coupling INADEQUATE = incredible natural abundance double quantum transfer experiment. 

In homonudear shift-correlation experiments like COSY we were concerned with the correlation of chemical shifts between nuclei of the same nuclear species, e.g., H with H. In heteronuclear shift-correlation experiments, however, the chemical shifts of nuclei belonging to different nuclear species are determined (e.g., H with C). These may be one-bond chemical shift correlations, e.g., between directly bound H and C nuclei, or they may be long-range chemical shift correlations, in which the interactions... 

The HMBC spectrum of vasicinone along with the H-NMR assignments are shown. Determine the H/ C long-range heteronuclear shift correlations based on the HMBC experiment, and explain how HMBC correlations are useful in chemical shift assignments of nonprotonated quaternary carbons. 

The HMBC spectrum of vasicinone displays long-range heteronuclear shift correlations between the various H/ C nuclei. These correlations are very helpful to determine the C-NMR chemical shifts of quaternary carbons and allow the interlinking of the different substructures obtained. 

Besse P, B Combourieu, G Boyse, M Sancelme, H de Wever, A-M Delort (2001) Long-range H- N heteronuclear shift correlation at natural abundance a tool to study benzothiazole biodegradation by two Rhodococcus strains. Appl Environ Microbiol 67 1412-1417. 

Long-Range Heteronuclear Shift Correlation HMBC... 

LONG-RANGE HETERONUCLEAR SHIFT CORRELATION HMBC AND RELATED EXPERIMENTS... 

Unlike HMBC /GHMBC and related long-range heteronuclear chemical shift correlation experiments, which have hundreds of reported applications in the published literature, there are considerably fewer reported applications of 1,1-ADEQUATE and related long-range variants in the literature. In part, the dearth of reported applications can be attributed to the considerably lower sensitivity of these experiments relative to, for example HMBC/GHMBC. Sensitivity concerns are largely ameliorated,... 

To provide the means of sampling a wider range of potential long-range heteronuclear coupling constants, an alternative version of this heteronuclear shift correlation experiment is called the accordion-optimized HMBC, or ACCORD-HMBC [50]. Additional modifications of this experiment are also available [51]. 

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