THE RELATIVE REACTIVITIES OF 1,2-<i>trans</i>-SUGAR ACETATES

Lemieux, R. U.; Brice, Carol

doi:10.1139/v56-132

Cited by 17 publications

(2 citation statements)

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“…Borate-complex formation with pyranose sugar derivatives which contain vicinal ci8-hydroxyl groups flanked by a ci8-methoxyl group is hindered (Foster, 1957). Certain neighbouring group reactions of some sugar acetates are hindered (Lemieux & Brice, 1956), since they involve intermediates structurally related to (IV). A detailed interpretation of these steric effects is given elsewhere (Foster, 1957;Lemieux & Brice, 1956).…”

Section: Discussionmentioning

confidence: 99%

“…Certain neighbouring group reactions of some sugar acetates are hindered (Lemieux & Brice, 1956), since they involve intermediates structurally related to (IV). A detailed interpretation of these steric effects is given elsewhere (Foster, 1957;Lemieux & Brice, 1956). Such a steric effect operating in the hydrolysis of glycerol 1-(inositol 2-phosphate) would oppose the formation of an inositol cyclic phosphate and hence divert the hydrolysis along the alternative pathway involving a glycerol cyclic phosphate.…”

Section: Discussionmentioning

confidence: 99%

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Phosphoinositides. 1. Configuration of the inositol phosphate in liver phosphatidylinositol

Hawthorne

1960

Biochemical Journal

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INSULIN AND AMINO ACID ACCUMULATION 495 in certain ['4C]amino acids has been investigated, together with the effect of insulin thereon. No important differences between the behaviour of the cut and intact preparations was observed. 2. With alanine, m-aminoi8obutyric acid, glycine, leucine, lysine, ornithine and phenylalanine the ratio of concentration of radioactivity in tissue water to that in the medium exceeded unity. With glutamic acid and aspartic acid the ratio was below unity, probably because of the rapid metabolism of these amino acids in isolated rat diaphragm. 3. The addition of insulin to the medium significantly raised the ratio for glycine and m-aminoi8obutyric acid, but not for the other amino acids under study. The effect ofinsulin was similar whether or not glucose was added to the medium. It was abolished by anoxia and by cooling the system to 120. 4. Under anoxic conditions, both in the presence or absence of insulin, the ratio was significantly raised by the addition of glucose to the medium. A similar effect of glucose was not seen under any other conditions studied. 5. No substantial evidence has been obtained to suggest that insulin promotes the incorporation of amino acids into protein in isolated diaphragm by enhancing the rate of entry of amino acids into the cytoplasm of the cells from the medium. This work has been greatly helped by a generous grant from the British Diabetic Association for the purchase of radioactive amino acids.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Phosphoinositides. 1. Configuration of the inositol phosphate in liver phosphatidylinositol

Hawthorne

1960

Biochemical Journal

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Syntheses and uses of isotopically labelled carboxylic acids

Zieliński

1969

Carboxylic Acids and Esters (1969)

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Konformationsanalyse, III. exo‐Anomerer Effekt und Circulardichroismus von Glycopyranosylaziden

1974

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Tetra-0-acetyl-pentopyranosen und Penta-0-acetyl-hexopyranosen setzen sich mit Trimethylsilylazid bei Gegenwart von BF3 oder SnC14 leicht zu den entsprechenden Glycosylaziden l a bis 11 um (Tab. I). Es entsteht stets nur das anomere Glycosylazid. in dem die Azidogruppe und 2-OAc ,,trans" zueinander angeordnet sind. In Glycosylaziden sind die Bindungen CI -N, und N,--N, in der Weise polarisiert, daR der Dipol in beiden Flllen zum N, weist. Hieraus wird abgeleitet, daD bei Glycosylaziden wie bei Methylglycosiden ein exo-anomerer Effekt wirksam sein sollte. der die Konformeren 9 und 12 stark bevorzugt. Die Anwendung der Arid-Oktantenregel sagt fur das a-D-Glycosylazid 12 einen negativen, fur das p-D-Glycosylazid 9 einen positiven Cotton-Effekt voraus. Messungen des Circulardichroismus stimmen mit diesen Voraussagen gut uberein, was fur einen exo-anomeren Effekt bei Glycosylaziden spricht. Conformational Analysis, 111 1) em-Anomeric Effect and Circular Didvoism of Glycopyranosyl AzidesTetra-0-acetyl-aldopentopyranoses and penta-0-acetyl-aldohexopyranoses react readily with trimethylsilyl azide in the presence of BF3 or SnC14 to afford the corresponding glycosyl azides l a -11 (table 1). Only the anomeric glycosyl atide having the azido group ,,trans" to the 2-acetoxy group is obtained in each case. The polarization of thc C1 -N, and N, -N, bonds in glycosyl azides is such that in both cases the dipole is directed towards N,. It can be deduced that glycosyl azides, like methyl glycopyranosides, should exhibit an exo-anomeric effect which strongly favors the conformers 9 and 12. The application of the azide-octant rule predicts a negative Cotton effect for the a-D-glycosyl a i d e 12 and a positive effect for the p-o-glycosyl azide 9. Circular dichroism measurements are in good agreement with these predictions, indicating the operation of an exo-anomeric effect in the glycosyl azides.

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THE RELATIVE REACTIVITIES OF 1,2-trans-SUGAR ACETATES

Cited by 17 publications

References 14 publications

Phosphoinositides. 1. Configuration of the inositol phosphate in liver phosphatidylinositol

Phosphoinositides. 1. Configuration of the inositol phosphate in liver phosphatidylinositol

Syntheses and uses of isotopically labelled carboxylic acids

Konformationsanalyse, III. exo‐Anomerer Effekt und Circulardichroismus von Glycopyranosylaziden

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