5-Dehydro Tolvaptan

5-Dehydro Tolvaptan is a structurally related impurity of the vasopressin antagonist Tolvaptan, featuring a fully aromatic benzothiazole core substituted with a 4-chlorophenyl group and a pyridine-linked sulfonamide. The compound exhibits a conjugated double bond system at the 5-position, resulting from dehydrogenation, which enhances rigidity compared to the parent molecule. This structural modification alters hydrogen bonding capacity and electronic distribution, impacting solubility and metabolic stability. The sulfonamide moiety retains full configuration, maintaining zwitterionic character critical for receptor interactions. Synthetically, this compound arises as a byproduct during oxidative coupling steps in Tolvaptan manufacturing. Analytically, it serves as an HPLC reference standard for impurity profiling in drug substance characterization.