Cori Ester as the Ligand for Monovalent Cations

Gerty T. and Carl F. Cori discovered, during research on the metabolism of sugars in organisms, the important role of the phosphate ester of a simple sugar. Glucose molecules are released from glycogen-the glucose stored in the liver-in the presence of phosphates and enter the blood as alpha-D-glucose-1-phosphate (Glc-1PH(2)). Currently, the crystal structure of three phosphates, Glc-1PNa(2)center dot 3.5 center dot H2O, Glc-1PK(2)center dot 2H(2)O, and Glc-1PHK, is known. Research has shown that reactions of Glc-1PH(2) with carbonates produce new complexes with ammonium ions [Glc-1P(NH4)(2)center dot 3H(2)O] and mixed complexes: potassium-sodium and ammonium-sodium [Glc-1P(X)(1.5)Na-0.5 center dot 4H(2)O; X = K or NH4]. The crystallization of dicationic complexes has been carried out in aqueous systems containing equimolar amounts of cations (1:1; X-Na). It was found that the first fractions of crystalline complexes always had cations in the ratio 3/2:1/2. The second batch of crystals obtained from the remaining mother liquid consisted either of the previously studied Na+, K+ or NH4+ complexes, or it was a new sodium hydrate-Glc-1PNa(2)center dot 5 center dot H2O. The isolated ammonium-potassium complex shows an isomorphic cation substitution and a completely unique composition: Glc-1PH(NH4)(x)K1-x (x = 0.67). The Glc-1P(2-) ligand has chelating fragments and/or bridging atoms, and complexes containing one type of cation show different modes of coordinating oxygen atoms with cations. However, in the case of the potassium-sodium and ammonium-sodium structures, high structural similarities are observed. The 1D and 2D NMR spectra showed that the conformation of Glc-1P(2-) is rigid in solution as in the solid state, where only rotations of the phosphate group around the C-O-P bonds are observed.