Complexes of carbohydrates with metal cations. IV. Cyclitols

Abstract

Cyclitols which contain an axial-equatorial-axial sequence of three hydroxyl groups form complexes with cations. Complex formation can be detected by the downfield shifts of the signals in their p.m.r. spectra; the signal of the hydrogen atom attached to the central carbon atom of the ax-eq-ax sequence shifts to the greatest extent. Equilibrium constants of complex formation have been determined by measuring the calcium ion concentration with an ion-selective electrode. cis-Inositol appears to form some 2 : 1 complex in addition to the prevalent 1 : 1 complex. Complexes of epi-inositol with calcium and strontium chloride have been isolated.