Donepezil quaternary salt

Donepezil quaternary salt is a pharmacologically inert derivative featuring a permanently charged quaternary ammonium center at the piperidine nitrogen, substituted with a benzyl group and paired with a bromide counterion. This structural modification introduces a sterically hindered, non-protonatable nitrogen, distinguishing it from the parent drug’s tertiary amine. The compound arises via alkylation of Donepezil’s piperidine moiety, resulting in a zwitterionic species stabilized by bromide anion interaction. Utilized as an HPLC reference standard for quantifying quaternary transformation byproducts in API synthesis.