Comparative analysis of the crystal structures of hydrates and sodium salts of monensin and its new C-26 succinate ester

Monensin succinate ester hydrate (2-H2O) has been synthesized by the succinylation of C-26 hydroxyl group of monensin (1) using a simple reaction with succinic anhydride. Additionally, the sodium salt (2-Na) of monensin succinate ester has been obtained. Molecular structures of both compounds (2-H2O and 2-Na) were studied using X-ray diffraction of single crystals and spectroscopic methods. According the crystallographic studies of 2-H2O and 2-Na, the molecules are held together as dimers linked by the centrosymmetric pairs of intermolecular hydrogen bonds between the carboxylic groups. The crystal structures of compounds 2-H2O and 2-Na are compared to those of the known monensin acid hydrate (1-H2O) and 1:1 inclusion complex of monensin A sodium salt with acetonitrile (1-Na-CH3CN) and that of newly obtained monensin sodium salt monohydrate (1-Na-H2O). Comparison of these structures showed a significant impact of C-26 succinate ester moiety on the coordination of the Na+ cation and hydrogen bond.