Relation between structure and properties of cyclodepsipeptides of valinomycin series

1. Employing the optical rotation dispersion, IR, and NMR spectroscopy methods, a study was made of the conformation states of some valinomycin analogs with modified side chains, and also of their K+ complexes. 2. A change in the side chains of valinomycin affects the relative stability of its conformation forms, but does not lead to the appearance of new forms. 3. In the “propeller” conformation the L-valine isopropyl groups shield the intramolecular H bonds from the action of the solvent. 4. Replacements of the valine residues by alanine moieties in the K+ complex of valinomycin are accompanied by an enhancement of the reaction of the solvent with the central ion. Such “unilateral” solvation leads to additional distortion of the symmetry of the system of chromophore groups in the complexes. The complexes of the analogs, obtained by the replacements L-Val→ L-Ala and D-Val→-D-Ala, have opposite chiralities of the depsipeptide chains.