Metal Binding Induced Conformational Interconversions in Methyl ?-D-xylopyranoside

摘要

A detailed conformational search for 4C1,1C4, and 2SO ring structures of methyl ß-D-xylopyranoside is performed by density functional theory calculations. For low energy structures in addition a composite energy approach is used. Complexation by divalent metal cations (Mg2+, Ca2+, Zn2+, Cd2+) induces a conformational interconversion 4C1 → 1C4. Relative Gibbs’ free energy differences between these two forms of the complexes roughly follow the respective ionic radii. In addition, for each ring conformation different binding sites of the cation are considered. In CHCl3 (PCM approximation for solvation), the shift toward the 1C4 chair form is substantially reduced or, in the case of the Cd2+ complexes, even reversed.