A survey of the proton spin–lattice relaxation rates of selected furanose derivatives

Bock, Klaus; Hall, Laurance D.; Pedersen, Christian

doi:10.1139/v80-306

Cited by 13 publications

(2 citation statements)

References 3 publications

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“…It seems reasonable to infer from this experiment that the relaxation of all the protons of 1, and by inference of all of the protons of the other seven isomers, are mediated by the dipole-dipole mechanism; and on the basis of the data given in Table 5 it ring. This could cause the proton-proton distances to be changed, but a conformational equilibrium could also offer an alternative source of relaxation (5). This explanation is supported by an X-ray examination of 1,danhydro-P-D-allopyranose (6), which shows that this compound even in the crystal adopts three different conformations with the 6-membered ring flattened.…”

Section: Discussion and Resultsmentioning

confidence: 94%

An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

Bock¹,

Hall²,

Pedersen³

1980

Can. J. Chem.

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. Can. J. Chem. 58, 1916Chem. 58, (1980. The nonselective spin-lattice relaxation rates (R,-values) have been determined for all of the ring protons of the eight isomers of 2,3,4-tri-0-acetyl-1,6-anhydro-~-~-hexopyranose as 0. I molar solutions in benzene-d,. The effects on the proton R,-values of changes in solvent, concentration, temperature, and proton impurities are documented and 13C R,-values are given to show that the first two sets of variations are due to changes in motional correlation times of the molecules. The proton relaxation datacan be fitted by regressional analyses to a single set of interproton relaxation contributions, the numerical values of which accord with a lC, conformation for the pyranose ring somewhat distorted by the 1,Ganhydro bridge.KLAUS BOCK. LAURANCE D. HALL et CHRISTIAN PEDERSEN. Can. J. Chem. 58,1916Chem. 58, (1980. On a determine les vitesses de relaxation spin-rCseau non selectives (valeur R,) de tous les protons du cycle des 8 isomeres du tri-0-acetyl-2,3,4 anhydro-1.6 P-D-hexopyrannose dans des solutions 0.1 molaire dans le benzene-d,. On a etudiC les effets des variations du solvant, de laconcentration, de la temperatureet des impuretis du proton sur les valeurs R , des protons et ondonne les valeurs R , du "C pour montrer que les deux premiers ensembles de variation sont dus aux changements des temps decorrelation du mouvement des molecules. Les donnees de relaxation du proton peuvent s'adapter par analyse regressive a un ensemble simple de contributions de relaxation interproton, dont les valeurs numeriques sont en accord avec une conformation lC, du cycle pyrannose quelque peu deformke par le pont anhydro-1,6.[Traduit par le journal]

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Section: Discussion and Resultsmentioning

confidence: 94%

An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

Bock¹,

Hall²,

Pedersen³

1980

Can. J. Chem.

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“…An exception has been noted in the case of androstanolone (12), in which the 19-methyl group relaxes slightly faster than the 18-methyl group; however, this compound is subject to steric perturbations in both the A and the D rings. 12 We shall now discuss the effects on the relative relaxation rates of introducing a carbon-carbon double bond; the expectation is that elimination of a 1,3syn-clinal interaction should enhance the R , value of a nearby methyl group. The data summarized below support this contention and, coupled with the previous observations, support the following generalizations.…”

Section: Relaxation Characteristics Of the Methyl Resonancesmentioning

confidence: 99%

A general survey of the proton spin–lattice relaxation rates of steroids

Colebrook¹,

Hall²

1983

Org. Magn. Reson.

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The spin-lattice relaxation rates of the aromatic, alkene, hydroxyl, methine and methyl protons of 19 steroid derivatives have been measured using the null point method. A simple procedure is described whereby the Itl values of molecules which have different motional tumbling rates can be directly inter-compared, and it is shown that such 'normalized' relaxation data can provide novel insight concerning both the geometry and the local molecular motion of these substances in solution.With the development' of rapid, routine procedures for determining the spin-lattice relaxation rates (R, values) of the protons of complex organic molecules, it is appropriate to begin to survey the diagnostic potential of these parameters in various areas of natural products chemistry. In this paper we report data for the directly assignable protons (aromatic, alkene, hydroxyl, methine and methyl) of several families of steroid derivatives.Under conditions which are readily realizable in routine studies2 (typically using c O . 1 M solute concentrations in a deuteriated solvent), the spin-lattice relaxation of most protons is dominated3 by the intramolecular dipole-dipole m e~h a n i s m ,~ which is summarized in Eqn (1) in terms of the relaxation contribution between two non-equivalent nuclei i, j :where yc and y1 are the magnetogyric ratios of the i and j nuclei, respectively, ri,j is their internuclear separation and -rc(i, j ) is the motional correlation time of the vector between them. As a result, the R , value of each proton reflects the composite influence of (a) the total spatial separation of that proton from the other protons of the same molecule, together with (b) its motional correlation time; the latter represents the summation of the overall tumbling rate of the molecule as a unit, plus any additional motion of the substituent group which bears that particular proton.Separate identification of the two contributions (a) and (b) can lead to two distinct types of structural information-solution geometry and molecular mobility-and one of the questions posed here is how best to effect this separation in a simple fashion. Since, for chemical purposes, change in the overall tumbling rate is not as important as knowledge of local motional freedom, our strategy has been to 'normalize' the experimental data in such a manner that the effect of * Author to whom correspondence should be addressed. Permanent address: Department of Chemistry, Concordia University, 1455 de Maisonneuve Blvd., West, Montreal, Quebec, Canada H3G 1M8.the overall tumbling represents a constant background (see Ref. 4 for a similar expression of this approach), and, as we shall show, the subsequent distinction between effects associated with changes in 'distance' and those involving 'mobility' can then be made because of the rapid decrease of the former with distance. RESULTS AND DIXUSSIONThe general features of the relaxation experiment itself and of the chemical significance of the R , values are concisely illustrated by reference to l-dehydrotestosterone ...

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ChemInform Abstract: APPLICATIONS OF PULSED NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY. PART 12. A SURVEY OF THE PROTON SPIN‐LATTICE RELAXATION RATES OF SELECTED FURANOSE DERIVATIVES

Bock¹,

Hall²,

Pedersen³

1981

Chemischer Informationsdienst

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A survey of the proton spin–lattice relaxation rates of selected furanose derivatives

Cited by 13 publications

References 3 publications

An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

An experimental evaluation of nonselective proton spin–lattice relaxation rates: analyses of data for the eight isomeric 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-hexopyranoses

A general survey of the proton spin–lattice relaxation rates of steroids

ChemInform Abstract: APPLICATIONS OF PULSED NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY. PART 12. A SURVEY OF THE PROTON SPIN‐LATTICE RELAXATION RATES OF SELECTED FURANOSE DERIVATIVES

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