Correlation of specific rotation with conformation. A new approach to the study of conformational equilibria

1968 ◽  
Vol 46 (8) ◽  
pp. 1453-1455 ◽  
Author(s):  
R. U. Lemieux ◽  
A. A. Pavia
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Optical Rotation ◽  
Specific Rotation ◽  
New Approach ◽  
Conformational Equilibria ◽  
Nuclear Magnetic

The marked changes in optical rotation which occur on dissolving the methyl 2-deoxy-α-L-and 3-deoxy-β-L-erythro-pentopyranosides in a variety of solvents including chloroform, acetone, acetonitrile, pyridine, dimethylsulfoxide, and water were found by nuclear magnetic resonance to result almost exclusively from changes in conformational equilibria. The changes in rotation are in agreement with those expected from Brewster's rules.

THE STRUCTURE OF RETAMINE AND THE PARTIAL SYNTHESIS OF THE (−)-ENANTIOMORPH

1965 ◽  
Vol 43 (7) ◽  
pp. 2012-2016 ◽  
Author(s):  
Kju Hi Shin ◽  
L. Fonzes ◽  
Léo Marion
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Opposite Sign ◽  
Optical Rotation ◽  
Partial Synthesis ◽  
Dehydration Product ◽  
Layer Chromatography ◽  
Nuclear Magnetic

Previous work by many authors has led to the assumption that retamine might be (+)-12-hydroxysparteine. A partial synthesis of the enantiomorph of this compound has been effected by dehydration of (+)-13-hydroxylupanine and hydroboration of the product. The dehydration product consisted of two components that were separated by thin-layer chromatography and identified by the characteristics of their nuclear magnetic resonance (n.m.r.) spectra as Δ12,13-and Δ13,14-dehydrolupanine. Hydroboration of the Δ12,13-isomer gave rise to (−)-12-hydroxy-sparteine having, in thin-layer chromatography, the same Rf value as natural retamine and the same optical rotation numerically, although of opposite sign. The synthetic base had the same infrared and n.m.r. spectra as the alkaloid and the two had superimposable Debye–Scherrer patterns. Evidence is given showing the hydroxyl to be equatorial.

The structures of the two lipopolysaccharide O-chains produced by Salmonella boecker

1988 ◽  
Vol 66 (10) ◽  
pp. 1066-1077 ◽  
Author(s):  
Jean-Robert Brisson ◽  
Malcolm B. Perry
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
High Molecular Weight ◽  
Nitrous Acid ◽  
Optical Rotation ◽  
Partial Hydrolysis ◽  
Magnetic Resonance Studies ◽  
High Molecular Weight Polymers ◽  
Nuclear Magnetic

Salmonella boecker, which belongs to group 0:6, 14(H) and shows the antigenic factors 6, 14, [1], and [25], defined by the Kauffmann–White system, produces two lipopolysaccharides differing from each other in the structures of their 0-polysaccharide moieties. By glycose composition, partial hydrolysis, nitrous acid deamination, methylation, optical rotation, and 1H and 13C nuclear magnetic resonance studies, the O-polysaccharides were demonstrated to be high-molecular-weight polymers (I and II) composed of either structurally related repeating tetrasaccharide or repeating pentasaccharide units having the structuresand[Formula: see text][Formula: see text]

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