Application of 13C nuclear magnetic resonance to the conformational analysis of vicinally di- and trisubstituted cyclohexanes: halohydrins, methoxyhalohydrins, and their acetates

1985 ◽  
Vol 63 (8) ◽  
pp. 2143-2148 ◽  
Author(s):  
G. W. Buchanan ◽  
J. W. Bovenkamp ◽  
A. Rodrigue ◽  
R. A. B. Bannard ◽  
R. Y. Moir
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperature ◽  
Chemical Shifts ◽  
Resonance Spectroscopy ◽  
Free Energies ◽  
Relative Peak Area ◽  
13C Nuclear Magnetic Resonance ◽  
Conformational Equilibria ◽  
Nuclear Magnetic

Low temperature 13C nuclear magnetic resonance spectroscopy has been employed to obtain the chemical shifts and to examine the conformational equilibria of the four chlorohydrins and bromohydrins of 3-methoxycyclohexene. The corresponding acetates and the unsubstituted halohydrins have also been examined. The observed chemical shifts were compared with those calculated from additivity considerations. Limitations of this approach are discussed. Relative peak area measurements have been used to obtain conformational free energies in favourable cases.

A 13C nuclear magnetic resonance study of selectivity in the binding of univalent counterions by heparin

1988 ◽  
Vol 66 (10) ◽  
pp. 2601-2604 ◽  
Author(s):  
Photis Dais ◽  
Kevin R. Holme ◽  
Arthur S. Perlin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Resonance Spectroscopy ◽  
Free Energies ◽  
Binding Selectivity ◽  
Hydrated Ions ◽  
Binding Preference ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The binding selectivities of univalent counterions for heparin in the systems Ca2+/M+/HEP, where M+ = Li+, Na+, K+, Cs+, TMA+, have been studied by 13C nuclear magnetic resonance spectroscopy. Chemical shift displacements of the various 13C nuclei of heparin in these systems clearly indicate that the binding selectivity of the polymer for univalent counterions increases with an increase in the radius of the hydrated cation form, namely Li+ > Na+ > K+ > Cs+ > TMA+. An explanation for this binding preference is offered on the basis of electrostatic and entropic terms, whereby the latter is reflected in changes in the hydration volumes of the univalent cations. Differences in the magnitude of these hydration volumes, in relation to the free energies of hydration, may account for a binding selectivity that favours the more highly hydrated ions.

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.

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.

Studies of specifically fluorinated carbohydrates. Part II. Nuclear magnetic resonance studies of pentopyranosyl fluoride derivatives

1969 ◽  
Vol 47 (1) ◽  
pp. 19-30 ◽  
Author(s):  
L. D. Hall ◽  
J. F. Manville
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Resonance Spectroscopy ◽  
Magnetic Resonance Studies ◽  
Conformational Model ◽  
Nuclear Magnetic

Detailed studies, by 1H and 19F nuclear magnetic resonance spectroscopy, of a series of fully esterified pentopyranosyl fluorides, show that all such derivatives favor that conformer in which the fluorine substituent is axially oriented. This conclusion is supported by separate considerations of the vicinal and geminal19F–1H and 1H–1H coupling constants, of the long-range (4J) 1H–1H and 19F–1H coupling constants and of the 19F chemical shifts. The limitations of the above conformational model are discussed.

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