6-Chloro Imidazopyridine Carboxamide Salt Forms for Low-pH Solubility

The patent applies parameter changes by converting the free base form into salt forms (hydrochloride, phosphate, tosylate) which fundamentally alters the solubility parameter of the compound. This transformation enables the compound to achieve adequate solubility in aqueous formulations while preserving its anti-tubercular activity, directly resolving the contradiction between activity and solubility.

The patent transforms the free base into salt forms through chemical reaction with acids (HCl, phosphate, tosylate), which changes the chemical stability parameter. The salt forms exhibit enhanced stability under storage conditions compared to the free base, while maintaining the core anti-tubercular activity, thus resolving the contradiction between activity and stability.

The patent segments the salt formation process into distinct, manageable steps: (1) preparation of the free base compound, (2) selection of appropriate acid counterion, (3) mixing in stoichiometric ratio, (4) evaporation of solvent, and (5) isolation of salt form. This segmentation simplifies the manufacturing complexity while achieving the desired solubility improvement through salt formation.

The patent applies partial action by providing a selective set of salt forms (hydrochloride, phosphate, tosylate) rather than exhaustively synthesizing all possible salt forms. This partial approach optimizes solubility and stability for pharmaceutical purposes while controlling production time, avoiding the excessive time consumption that would result from synthesizing every possible salt variant.