Long-range heteronuclear chemical shift

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,... 

Long-range heteronuclear chemical shift correlations were observed for... 

Based on experience in one of the author s laboratories (GEM), cryogenic NMR probe technology may have the single biggest positive impact on increasing the facility with which long-range heteronuclear chemical shift correlation data may be acquired. 

Long-range Heteronuclear Chemical Shift Correlation... 

Even incomplete long-range heteronuclear chemical shift data... 

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. 

The general structure, stereochemistry at the five stereocenters, the N1 and N4 chemical shifts, and the observed long-range heteronuclear couplings of the series of oxindole alkaloids are shown in Table 2. The chemical shift range of the alkaloids described in this report was a useful reporter of stereochemical differences at the various stereocenters. The N1 shifts range from 136.9 to 135.1 ppm while in contrast, the N4 shifts ranged from 54.6 to 64.8 ppm. The a//<9-type isomers (35, 205) uncarine-C and E exhibited substantial shift differences at N4 (8-10 ppm) relative to the epiallo-iypQ... 

Fig. 6. HMBC spectrum of cryptospirolepine (1) in d6-DMSO recorded at 400 MHz. While most of the responses contained in the spectrum arise via long-range heteronuclear coupling pathways of interest, there are several incompletely canceled direct responses still observable. Incompletely canceled direct responses in an HMBC spectrum are readily identified as a 120-180 Hz doublet centered about the proton chemical shift at the carbon chemical shift of the directly bound carbon identifiable from the HMQC spectrum...

Martin GE, Zektzer AS (1988) Long-range two-dimensionalear heteronuclear chemical shift correlation. Magn Reson Chem 26 631-652 Massiot G, Nuzillard JM, Richard B, Le Men-Olivier L (1990) Alternative partial synthesis of bisindole alkaloids. Tetrahedron Lett 31 2883-2884 Meksuriyen D, Cordell GA (1988) Biosynthesis of staurosporine. 1. and C NMR assingments. J Nat Prod 51 884-892... 

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