Dorzolamide hydrochloride impurity 5

Dorzolamide hydrochloride impurity 5 is a structurally related synthetic byproduct arising from incomplete sulfamation during Dorzolamide production. It retains the 1,3-thiadiazole core and 2-methylbenzoyl moiety of the parent drug but lacks the terminal sulfamate group, featuring instead a free thiol (-SH) functionality at the terminal position. This thiol group introduces distinct redox reactivity compared to the parent compound. The compound serves as a critical HPLC reference standard for quantifying process-related impurities in Dorzolamide hydrochloride bulk drug substance.