5-Carboxy Tolterodine

5-Carboxy Tolterodine is a degradation byproduct of Tolterodine, characterized by a quinuclidine ring linked to a 5-carboxy-substituted tolyl group. The carboxylic acid functional group introduces polarity and hydrogen-bonding capacity, distinguishing it from the parent compound. This structural modification arises via oxidative cleavage of the Tolterodine aromatic ring, yielding a meta-substituted carboxylic acid derivative. The compound retains the quinuclidine core but exhibits altered physicochemical properties due to the electron-withdrawing carboxylate moiety. It serves as an HPLC reference standard for impurity profiling in Tolterodine drug substance analysis.