Glycosidation of sugars. IV. Methanolysis of D-glucose, D-galactose, and D-mannose

1968 ◽  
Vol 46 (19) ◽  
pp. 3085-3090 ◽  
Author(s):  
V. Smirnyagin ◽  
C. T. Bishop
Keyword(s):  
Conformational Analysis ◽  
Ground States ◽  
Reaction Proceeds ◽  
Competing Reactions

Rates of methanolysis reactions of D-glucose, D-galactose, and D-mannose have been determined. The results confirm those found earlier for pentoses that the glycosidation reaction proceeds to equilibrium through four distinguishable competing reactions: (1) hexose → furanosides, (2) anomerization of furanosides, (3) furanosides → pyranosides, and (4) anomerization of pyranosides. The glycoside compositions at equilibrium are interpreted in terms of conformational analysis for furanoid and pyranoid rings. The energy differences between the ground states also contribute to an important degree in determining the relative rates of reaction.

GLYCOSIDATION OF SUGARS: II. METHANOLYSIS OF D-XYLOSE, D-ARABINOSE, D-LYXOSE, AND D-RIBOSE

1963 ◽  
Vol 41 (11) ◽  
pp. 2743-2758 ◽  
Author(s):  
C. T. Bishop ◽  
F. P. Cooper
Keyword(s):  
Conformational Analysis ◽  
Excellent Agreement ◽  
Transition States ◽  
Interaction Energies ◽  
Free Energies ◽  
Ionic Effects ◽  
Competing Reactions

Rates of methanolysis reactions of D-xylose, D-arabinose, D-lyxose, and D-ribose have been determined. It was found that methanolysis of a pentose proceeds to equilibrium through four distinguishable, competing reactions: (1) pentose → furanosides; (2) anomerization of furanosides; (3) furanosides → pyranosides; (4) anomerization of pyranosides. The glycoside compositions at equilibrium are interpreted in terms of stabilities of each of the four glycosides from each sugar as influenced by steric and ionic effects; a system of conformational analysis of furanoside rings is presented. The free energies of reaction in anomerization of pyranosides were in excellent agreement with values calculated from previously reported interaction energies in the pyranoid ring. The relative rates of the reactions were consistent with the view that non-bonded interactions in the methyl glycosides are relieved in the transition states for their interconversions.

On the role of Newman projections in conformational analysis. Evidence for nonalternating ground states in highly strained molecules

1978 ◽  
Vol 100 (10) ◽  
pp. 3149-3156 ◽  
Author(s):  
W. Douglas Hounshell ◽  
Dennis A. Dougherty ◽  
Kurt Mislow
Keyword(s):  
Conformational Analysis ◽  
Ground States ◽  
Strained Molecules ◽  
Highly Strained

Conformational analysis about the N-N bond by N.M.R. spectroscopy: N'-sulphonyl derivatives of N-Aminobicyclo[2,2,1]hept-5-ene-endo-2,3-dicarboximide

1974 ◽  
Vol 27 (6) ◽  
pp. 1227 ◽  
Author(s):  
SM Verma ◽  
Rao C Koteswara
Keyword(s):  
Conformational Analysis ◽  
Conformational Changes ◽  
Ground States ◽  
Spectral Changes ◽  
Rotational Barriers ◽  
Tosyl Group ◽  
Derivatives Of ◽  
Acyl Derivatives

A series of N'-sulphonyl and N'-acyl derivatives of N-aminobicyclo[2,2,1]hept-5-ene-endo-2,3-dicarboximide have been synthesized and their conformations have been investigated by N.M.R.spectroscopy. The effect of the sulphonyl group at the exocyclic nitrogen on the conformational process about the N-N bond has been studied. Existence of non-planar ground states about the N-N bond in the N',N?-disulphonyl and N'-sulphonyl-N'-acyl derivatives has been demonstrated.Temperature-dependent spectral changes have been related to the conformational changes about the N-N bond. It has been shown that the N'-tosyl substituent assumes a preferred conformation about the N-SO2 bond; the aryl part of the tosyl group lies exo to the cage-moiety. The N'-tosyl-N'-aroyl derivatives also show a preferred conformation about the N'-aroyl bond, the aryl part of the aroyl group lying endo to the cage-moiety. The N'-acetyl-N'-aroyl derivatives have been shown toexhibit low rotational barriers about the N'-aroyl bond.

Observations of the Thermal Decomposition of Brucite

1968 ◽  
Vol 26 ◽  
pp. 446-447
Author(s):  
P. L. Burnett ◽  
W. R. Mitchell ◽  
C. L. Houck
Keyword(s):  
Thermal Decomposition ◽  
Magnesium Oxide ◽  
Basal Plane ◽  
Magnesium Ions ◽  
A Value ◽  
Reaction Proceeds

Natural Brucite (Mg(OH)2) decomposes on heating to form magnesium oxide (MgO) having its cubic ﹛110﹜ and ﹛111﹜ planes respectively parallel to the prism and basal planes of the hexagonal brucite lattice. Although the crystal-lographic relation between the parent brucite crystal and the resulting mag-nesium oxide crystallites is well known, the exact mechanism by which the reaction proceeds is still a matter of controversy. Goodman described the decomposition as an initial shrinkage in the brucite basal plane allowing magnesium ions to shift their original sites to the required magnesium oxide positions followed by a collapse of the planes along the original <0001> direction of the brucite crystal. He noted that the (110) diffraction spots of brucite immediately shifted to the positions required for the (220) reflections of magnesium oxide. Gordon observed separate diffraction spots for the (110) brucite and (220) magnesium oxide planes. The positions of the (110) and (100) brucite never changed but only diminished in intensity while the (220) planes of magnesium shifted from a value larger than the listed ASTM d spacing to the predicted value as the decomposition progressed.

Conformational Analysis of Cyclic Opioid Peptide Analogs

1988 ◽  
Author(s):  
Peter W. Schiller ◽  
Brian C. Wilkes
Keyword(s):  
Conformational Analysis ◽  
Opioid Peptide ◽  
Peptide Analogs

Conformational Analysis of Opioid Receptor-Selective Peptides Using Nuclear Magnetic Resonance and Theoretical Calculations

1991 ◽  
Author(s):  
Victor J. Hurby ◽  
◽  
Om Prakash ◽  
Wieslaw Kazmierski ◽  
Catherine Gehrig ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Conformational Analysis ◽  
Opioid Receptor ◽  
Theoretical Calculations ◽  
Nuclear Magnetic
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