Salts and Ionic Liquid of The Antituberculosis Drug <i>S,S</i>-Ethambutol

A salt screen of the antituberculosis chiral basic drug Ethambutol with protic acids resulted in the formation of several salts and an ionic liquid. The protic salt/ionic liquid product was characterized by spectroscopic (ATR-IR and ss-NMR), thermal (DSC and TGA), and X-ray diffraction. Similar to the marketed Ethambutol dihydrochloride salt of the drug, all the new salts were found to be hygroscopic. Moisture-free conditions of the desiccator and rotavapor gave nonhygroscopic materials in a few cases. X-ray crystal structures of two new salts were determined and that of the Ethambutol base and Ethambutol dihydrochloride salt were redetermined in this work.