Nuclear magnetic resonance heteronuclear enhancement

Due to the great complexity of this class of molecules, nuclear magnetic resonance (NMR) and mass spectroscopy (MS) are the tools most widely used to identify cucurbitacins. Both one- and two-dimensional NMR techniques have been employed for the structural elucidation of new compounds 2D NMR, 1H-NMR, 13C-NMR, correlated spectroscopy (COSY), heteronuclear chemical shift correlation (HETCOR), attached proton test (APT), distortionless enhancement by polarization transfer (DEPT), and nuclear Overhauser effect spectroscopy (NOESY) are common techniques for determining the proton and carbon chemical shifts, constants, connectivity, stereochemistry, and chirality of these compounds [1,38,45-47]. 

Lerner L, Bax A (1986) Sensitivity-enhanced two-dimensional heteronuclear relayed coherence transfer NMR spectroscopy. J Magn Reson 69 375-380 Leupin W, Wagner G, Denny WA, Wiithrich K (1987) Assignment of the carbon-13 nuclear magnetic resonance spectrum of a short DNA-duplex with proton-detected two-dimensional heteronuclear correlation spectroscopy. Nucl Acid Res 15 267-275 Levy GC, Lichter RL (1979) Nitrogen-15 nuclear magnetic resonance spectroscopy. John Wiley, New York... 

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