scholarly journals Conformational analysis in carbohydrate chemistry. V. Formation of glycosidic anhydrides from heptoses

1981 ◽  
Vol 59 (2) ◽  
pp. 379-383 ◽  
Author(s):  
Stephen John Angyal ◽  
Trung Quang Tran
Keyword(s):  
Conformational Analysis ◽  
Major Product ◽  
Carbohydrate Chemistry ◽  
Dioxane Ring

The position of the equilibrium between aldoheptoses and their glycosidic anhydrides depends crucially on the configuration of the heptose. Depending on that configuration, the 1,6-anhydropyranose, the 1,7-anhydropyranose, or the 1,6-anhydrofuranose is the major product, its proportion varying from 99% to less than 1%. The position of the equilibrium is predictable from conformational considerations. 1,7-Anhydrofuranoses have not been encountered. The 1,3-dioxane ring of the 1,7-anhydropyranoses was found to assume a skew form.

Conformational analysis about the N-N bond by P.M.R. spectroscopy: N'-derivatives of N-amino-1,2,3,4-tetrahydro-9-oxo-1,4-ethanonaphthalene-endo-2,3-dicarboximide

1973 ◽  
Vol 26 (9) ◽  
pp. 1963 ◽  
Author(s):  
SM Verma ◽  
O Subba Rao
Keyword(s):  
Maleic Anhydride ◽  
Conformational Analysis ◽  
Conformational Changes ◽  
Major Product ◽  
Diels Alder ◽  
Conformational Study ◽  
Temperature Dependent ◽  
Spectral Changes ◽  
Derivatives Of

A series of N?-derivatives of N-amino-1,2,3,4-tetrahydro-9-oxo-1,4- ethanonaphthalene-endo-2,3-dicarboximide have been prepared and their p.m.r. spectra studied. The non-planar ?cage-moiety? structure has been used in the conformational study. Temperature dependent spectral changes have been related to conformational changes about the N-N bond. ��� The endo configuration of the major product obtained in Diels-Alder addition of maleic anhydride on β-naphthol has been strongly evidenced.

Conformational analysis in carbohydrate chemistry. II. Equilibria between reducing sugars and their glycosidic anhydrides

1968 ◽  
Vol 21 (11) ◽  
pp. 2747 ◽  
Author(s):  
SJ Angyal ◽  
K Dawes
Keyword(s):  
Gas Chromatography ◽  
Conformational Analysis ◽  
Reducing Sugars ◽  
Interaction Energies ◽  
Carbohydrate Chemistry ◽  
Conformational Interaction ◽  
Good Agreement

The position of the equilibria between aldohexoses and 3-deoxyaldohexoses and their 1,6-anhydrides, and between heptuloses and their 2,7-anhydrides, has been determined by gas chromatography. The results are in good agreement with data calculated from conformational interaction energies. D-Talose gives equal amounts of the 1,6-anhydropyranose and the 1,6-anhydrofuranose. D-glycero-D-gulo-Heptose gives 66% of the 1,7- and only 9% of the 1,6-anhydride.

Conformational analysis in carbohydrate chemistry. III. The 13C N.M.R. spectra of the hexuloses

1976 ◽  
Vol 29 (6) ◽  
pp. 1249 ◽  
Author(s):  
SJ Angyal ◽  
GS Bethell
Keyword(s):  
Aqueous Solution ◽  
Conformational Analysis ◽  
Carbohydrate Chemistry ◽  
Related Compounds

All the resonances have been assigned in the 13C N.M.R. spectra of the hexuloses and some of their derivatives by the use of specifically deuterated compounds and comparison with related compounds. The composition of the hexuloses at equilibrium in aqueous solution has been determined and is discussed in terms of conformational analysis. The synthesis of D-fructose[l-D], D-fructose[3-D] and D-fructose[4-D] is described.

Conformational analysis in carbohydrate chemistry. I. Conformational free energies. The conformations and α : β ratios of aldopyranoses in aqueous solution

1968 ◽  
Vol 21 (11) ◽  
pp. 2737 ◽  
Author(s):  
SJ Angyal
Keyword(s):  
Aqueous Solution ◽  
Free Energy ◽  
Conformational Analysis ◽  
Reasonable Agreement ◽  
Anomeric Effect ◽  
Interaction Energies ◽  
Free Energies ◽  
Carbohydrate Chemistry ◽  
Predominant Conformation

The relative free energies of the aldopyranoses in aqueous solution have been calculated, taking non-bonded interaction energies and the anomeric effect into account. It is shown that the calculated free-energy values correctly predict the predominant conformation of the α- and β-pyranose forms of each aldose. The α- to β-pyranose ratios of the aldoses in aqueous solution, calculated from these values, are in reasonable agreement with those determined experimentally.

Carbanions in Carbohydrate Chemistry: Synthesis of C-Glycosyl Malonates

1974 ◽  
Vol 52 (8) ◽  
pp. 1266-1279 ◽  
Author(s):  
Stephen Hanessian ◽  
Andre G. Pernet
Keyword(s):  
Acetic Acid ◽  
Malonic Acid ◽  
Diethyl Malonate ◽  
Major Product ◽  
Carbohydrate Chemistry ◽  
Anomeric Configuration ◽  
Bromide Ion ◽  
Chemical Correlation ◽  
Shift Reagents

The condensation of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide with sodio diethyl malonate led to crystalline diethyl 2-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl) malonate. The corresponding dibenzyl ester proved to be a versatile intermediate for the preparation of crystalline β-D-glucopyranosyl malonic acid and β-D-glucopyranosyl acetic acid derivatives. The anomeric configuration in these C-glycosides was determined by a chemical correlation. With 2,3,4,6-tetra-O-acetyl- β-D-glucopyranosyl chloride and sodio diethyl malonate, the major product was a 1,2-O-ketal derivative resulting from an attack of the carbanion on the 1,2-acetoxonium ion. The condensation of 2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl bromide with sodio diethyl malonate was conducted with, and without added bromide ion and the mechanistic implications of the results are discussed. C-Glycosides were also prepared in the D-mannofuranose series and their transformation into the D-lyxofuranose series (anomeric mixture) is described. The utility of n.m.r. shift reagents, and an apparent differential complexation by Eu(DPM)3 and Eu(FOD)3-d27 is demonstrated.

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