Ketoconazole trans tosylate

Ketoconazole trans tosylate is a stereoisomeric impurity derived from the antifungal parent drug, featuring a tosylate ester substitution at the 4-hydroxy position of one phenolic ring. The trans configuration of the diphenylethylene bridge distinguishes it from cis analogs, introducing steric hindrance and altered electronic properties. This derivative retains the core 1,2-diphenylethylene scaffold but incorporates a para-toluenesulfonyl group, enhancing its electrophilic character. It arises as a synthetic byproduct during API manufacturing due to regioselective tosylation. This compound serves as a critical HPLC reference standard for quantifying process-related impurities in ketoconazole formulations.