Dynamics of nuclear Overhauser enhancement in proton decoupled carbon-13 nuclear magnetic resonance

1976 ◽  
Vol 64 (6) ◽  
pp. 2533 ◽  
Author(s):  
Stanley J. Opella
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Overhauser Enhancement ◽  
Nuclear Overhauser ◽  
Nuclear Magnetic

Major saponins from the starfish Asteriasforbesi. Complete structures by nuclear magnetic resonance methods

1987 ◽  
Vol 65 (6) ◽  
pp. 1384-1391 ◽  
Author(s):  
John A. Findlay ◽  
Mahesh Jaseja ◽  
D. Jean Burnell ◽  
Jean-Robert Brisson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Sodium Sulfate ◽  
Nuclear Overhauser Enhancement ◽  
Nuclear Overhauser ◽  
Nuclear Magnetic

The structures of the two major saponins isolated from the starfish Asteriasforbesi have been deduced totally by nuclear magnetic resonance methods applied to the undegraded molecules. The structure of forbeside A, 6α-O-{β-D-galactopyranosyl-(1 → 3)-β-D-fucopyranosyl-(1 → 2)-β-D-galactopyranosyl-(1 → 4)-[β-D-quinovopyranosyl-(1 → 2)]-β-D-xylopyranosyl-(1 → 3)-β-D-quinovopyranosyl}-20-hydroxy-23-oxo-5α-cholest-9(11)-en-3β-yl sodium sulfate, was deduced principally from 1H 2D-COSY, J-resolved, nuclear Overhauser enhancement and selected decoupling experiments. The structure of forbeside B, 6α-O-{β-D-quinovopyranosyl-(1 → 2)-β-D-galactopyranosyl-(1 → 4)-[β-D-quinovopyranosyl-(1 → 2)]-β-D-xylopyranosyl-(1 → 3)-β-D-quinovopyranosyl}-20-hydroxy-23-oxo-5α-cholest-9(11)-en-3β-yl sodium sulfate, was deduced principally from 2D-COSY, HCORR, RECSY, and NOESY experiments.

4,6-Dinitro-benzofuroxan and -benzofurazan adducts of 1,8-bis(dimethylamino)naphthalene. A conformational study by low temperature nuclear magnetic resonance

1987 ◽  
Vol 65 (2) ◽  
pp. 404-408 ◽  
Author(s):  
Marie-Paule Simonnin ◽  
Jean-Claude Halle ◽  
Marie-José Pouet ◽  
François Terrier ◽  
Daniel Davoust
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Proton Sponge ◽  
Conformational Study ◽  
Difference Spectra ◽  
Nuclear Overhauser Enhancement ◽  
Nuclear Magnetic Resonance Spectra ◽  
Nuclear Overhauser ◽  
Nuclear Magnetic

Low temperature 1H nuclear magnetic resonance spectra of the zwitterionic and anionic carbon-bonded adducts resulting from the addition of 4,6-dinitrobenzofuroxan (DNBF) or 4,6-dinitrobenzofurazan (DNBZ) to 1,8-bis(dimethylamino)naphthalene, the proton sponge PS, have been recorded at 500 MHz inDMF-d7. They reveal the presence of two conformers due to restricted rotation around the [Formula: see text] bond between C-4 of PS and the sp3 carbon C-7′ of the negatively charged DNBF− or DNBZ− moiety. The geometry of these conformers was deduced from nuclear Overhauser enhancement difference spectra. The results show that in all systems there is a large preference for the less strained s-trans type of conformation, whose population lies between 80 and 90%. An interesting feature is the dependence of the chemical shift of the peri H5 proton on the conformation. In accordance with previously reported peri effects, a significant deshielding of H5 is observed in the major conformers, where this proton is spatially close to H7′. In contrast, H5 moves upfield in the minor conformers, in which it lies in the vicinity of the DNBF− or DNBZ− moiety.

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