Mirabegron Impurity 5

Mirabegron Impurity 5 is a synthetic byproduct arising from the oxidation of a sulfide intermediate during the final stages of Mirabegron synthesis. It features a substituted benzamide core linked to a piperazine ring, with a key structural distinction being the presence of a sulfonyl group (–SO2–) in place of the parent compound's sulfide moiety. This impurity retains the β-adrenergic agonist scaffold but exhibits altered electronic properties due to the sulfonyl oxygen's electron-withdrawing effect. It serves as a critical HPLC reference standard for quantifying process-related impurities in Mirabegron drug substance batches.