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DIVISION DE CHIMIE ORGANIQUE
LA CHIMIE DES CARBOHYDRATES—VI
Conferences plenieres presentees au
VIe SYMPOSIUM INTERNATIONAL SUR LA CHIMIE DES CARBOHYDRATES ä Madison, USA 14-18 aoüt 1972
Redacteur du Symposium W. M. DOANE
Northern Regional Research Laboratory. Peoria, Illinois
LONDRES
BUTTERWORTHS
DIVISION OF ORGANIC CHEMISTRY
CARBOHYDRATE CHEMISTRY—VI
Plenary lectures presented at the
Vlth INTERNATIONAL SYMPOSIUM ON CARBOHYDRATE CHEMISTRY held at Madison, USA 14-18 August 1972
Symposium Editor W. M. DOANE
Northern Regional Research Laboratory, Peoria, Illinois
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The contents of this book appear in
Pure and Applied Chemistry, Vol. 35 No. 2 (1973) Suggested U.D.C. number 547-45(063)
International Union of Pure and Applied Chemistry 1973
ISBN 0 408 70525 6
Printed in Great Britain by Page Bros (Norwich) Ltd., Norwich
ORGANIZING COMMITTEE Chairman: R. L. WfflSTLER Members: L. ANDERSON (Secretary)
R. M. ROWELL (Treasurer) W. M. DOANE M. FISCHER S. P. ROWLAND
COMPLEX FORMATION BETWEEN SUGARS AND METAL IONS S. J.
ANGYAL
School of Chemistry. The University of New South Wales Kensington, NSW Australia ABSTRACT Cyclitols and sugars containing an axial-equatorial-axial sequence of three hydroxyl groups in a six-membered ring, or a eis-eis sequence in a five-membered ring, form 1:1 complexes with metal cations in hydroxylic solvents. At least one of the hydroxyl groups can be replaced by a methoxy group without substantially affecting complex formation. Lanthanum(m) forms the strongest complexes (K about 10 m o l - 1 1 in water), followed by calcium and strontium. Complex formation causes downfield shifts of the signals in the p.m.r. spectrum, that of the hydrogen atom vicinal to the oxygen atom central in the ax-eq-ax sequence being the largest. Complex formation will change the conformational equilibrium of methyl ß-D-ribopyranoside and ß-D-lyxopyranose; it will change the anomeric equilibrium of allose, gulose, ribose, and lyxose. It will also alter the equili brium in methanol between the methyl glycosides of the above-mentioned sugars; in the presence of calcium or strontium chlorides, methyl glycosides can be synthesized which normally are only minor products of methanolysis. Complex formation makes possible the separation of some sugars by electrophoresis and on ion-exchange columns.
INTRODUCTION
The field of sugar-metal complexes is still largely unexplored. Yet it is not a small field: the chemical literature records 1 at least 70 crystalline complexes which contain a sugar (or a sugar derivative) and an inorganic salt in stoichiometric proportion (usually 1:1). Without detailed investigation of these complexes it is not possible to determine whether they are specific co ordination compounds of one molecule of sugar with one cation—which would remain associated in solution—or arrangements held together in the crystal lattice by intermolecular forces. x-Ray crystallographic analyses would be desirable but have been carried out only in two cases so far. One is that of sucrose sodium bromide dihydrate 2 in which both the cation and the anion