Heteronuclear multiple-bond correlation spectroscopy

Weaker correlations, corresponding to smaller coupling constants, are identified with (w). Not all these are observed in Fig. 6.25 at the contour levels shown. 

HMQC/HSQC and then HMBC typically represent the primary techniques to turn to when addressing problems of molecular connectivity in small organic molecules. 

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HMBC Heteronuclear multiple-bond correlation spectroscopy To elucidate structure of organic molecules To establish long-range (i.e., multibond) heteronuclear coupling... 

Hadden, C.E., Martin, G.E., and Krishnamurthy, V.V., Improved performance accordion heteronuclear multiple-bond correlation spectroscopy — IMPEACH-MBC, J. Magn. Reson., 140, 274, 1999. 

The fatty acyl substituents were mainly of three types saturated straight-chain C,6-C,9 acids C21-C25 mycosanoic acids and C24-C28 mycolipanolic acids. Analysis of one of the major 2,3-di-O-acyltrehaloses by two-dimensional H-chemical-shift-correlated and H-detected heteronuclear multiple-bond correlation spectroscopy established that the C18 saturated straight-chain acyl group was located at the 0-2 position and that the C24 mycosanoyl substituent was at the 0-3 position of the same nonglycosylated terminus (structure 8). At least six molecular... 

HMBC Heteronuclear Multiple Bond Correlation 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). 

In heteronuclear multiple-bond correlation spectroscopy (HMBC) spectra, C-1 of glucose residue A-G and the other H-4 generate a coupling peak (8 101.39, 3.58), and C-4 in a glucose residue A-G and H-1 in another residue produce a coupling peak (8 80.79, 5.06), which indicates that C-1 and H-4 are connected, and C-4 and H-1 are connected, in accordance with the structure of CD main... 

Bax A, Davis DG (1985) MLEV-17 Based two-dimensional homonuclear magnetization transfer spectroscopy. J Magn Reson 65 355-360 Bax A, Drobny G (1985) Optimization of two-dimensional homonuclear relayed coherence transfer NMR spectroscopy. J Magn Reson 61 306-320 Bax A, Marion D (1988) Improved resolution and sensitivity in H-detected heteronuclear multiple-bond correlation spectroscopy. J Magn Reson 78 186-191 Bax A, Subramanian S (1986) Sensitivity-enhanced two-dimensional heteronuclear chemical shift correlation NMR spectroscopy. J Magn Reson 67 565-569 Bax A, Summers MF (1986) and Assignments from sensitivity-enhanced detection of heteronuclear multiple bond connectivity by 2D multiple-quantum NMR. J Am Chem Soc 108 2093-2094... 

Korb, J.-R, Monteilhet, L., McDonald, P.J., and Mitchell, J. 2007. Microstructure and texture of hydrated cement-based materials A proton field cycling relaxometry approach. Cem. Conor. Res. 37 295-302. Koskela, H., Kilpelainen, L, Heikkinen, S., and Cahsqc, L.R. 2003. An application of a Carr-PurceU-Meiboom-Gill-type sequence to heteronuclear multiple bond correlation spectroscopy. J. Magn. Reson. 164 228-232. Kozlov, RV. and Burdygina, G.I. 1983. The structure and properties of solid gelatin and principles of their modification. Polymers 24 651-666. 

With compound 2 in hand, various conditions wctc tried for direct Ci allylic oxidation, but none was successful. Thus, a circuitous route (Rg. 3.31) was developed. Using CCI4 as solvent, taking benzoyl peroxide as the radical initiator, NBS allylic bromination of compound 2 was triggered to obtain compound 3.63 with 90 % yield. Heteronuclear multiple-bond correlation spectroscopy (HMBC) confirmed the bromination happened at the Ci position without rearrangement. However, when compound 3.63 reacted with sodium bicarbonate and 4-methoxylpyridine Af-oxide,... 

ACF = atom-centered fragment AI = artificial intelligence BAM = bond adjacency matrix CHEMICS = combined handling elucidation method for interpretable chemical structures COSY = correlated spectroscopy FBMX = free-bond connection matrix HMBC = heteronuclear multiple bond correlation spectroscopy HMQC = heteronuclear multiple quantum coherence correlation spectroscopy SESAMI = systematic elucidation of structure applying machine intelligence. 

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