Identification of C-24 alkyl epimers of marine sterols by 13C nuclear magnetic resonance spectroscopy

1978 ◽  
Vol 56 (14) ◽  
pp. 1898-1903 ◽  
Author(s):  
J. L. C. Sright ◽  
A. G. McInnes ◽  
S. Shimizu ◽  
D. G. Smith ◽  
J. A. Walter ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Structural Changes ◽  
Chemical Shifts ◽  
Resonance Spectroscopy ◽  
H Nmr ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

13C nuclear magnetic resonance spectra of diastereomeric C-24 alkyl sterols have been assigned. Differences in the chemical shifts of side-chain carbons permitted the determination of the absolute configuration at C-24 in several sterols since these chemical shifts are insensitive to structural changes remote from the asymmetric centre. An unknown sterol from Tetraselmissuecica has been identified as (24R)-24-methylcholest-5-en-3β-ol and the configuration assigned from 1H nmr data to the sterol from Phaeodoctylumtricornutum has been confirmed. The utility and potential of this method in characterising new sterols and their biological precursors is discussed.

13C nuclear magnetic resonance spectra of 3,6-disubstituted pyridazines

1991 ◽  
Vol 69 (6) ◽  
pp. 972-977 ◽  
Author(s):  
Gottfried Heinisch ◽  
Wolfgang Holzer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The 13C nuclear magnetic resonance spectra of 17 3,6-disubstituted pyridazine derivatives have been systematically analyzed. Chemical shifts and various 13C, 1H coupling constants are reported. Attempts were made to correlate these data with results obtained from semiempirical molecular orbital calculations as well as with substituent electronegativities and Taft's substituent constants σI and σR0. Key words: 3,6-disubstituted pyridazines, 13C NMR spectroscopy, 13C, 1H spin coupling constants.

Configurational assignment of epimeric secondary six-membered allylic alcohols by 13C nuclear magnetic resonance spectroscopy. A new approach

1986 ◽  
Vol 64 (12) ◽  
pp. 2331-2333 ◽  
Author(s):  
Teodoro S. Kaufman ◽  
Mirta P. Mischne ◽  
Manuel Gonzalez-Sierra ◽  
Edmundo A. Ruveda
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Hydroxyl Group ◽  
Allylic Alcohols ◽  
Resonance Spectroscopy ◽  
New Approach ◽  
Configurational Assignment ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

On the basis of the effects of the hydroxyl group on the 13C nuclear magnetic resonance chemical shifts of the olefinic carbons, a new parameter was defined and a new rule was proposed for the assignment of the stereochemistry of secondary six-membered cyclic allylic alcohols.

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