N-Benzylquininium chloride is an ionic organic compound derived from the natural alkaloid quinine. It features a quinuclidine core structure with a benzyl group attached to the tertiary nitrogen atom, forming a quaternary ammonium salt. This modification significantly alters its solubility and reactivity profile compared to the parent quinine. This compound is primarily utilized as a chiral phase-transfer catalyst (PTC) in organic synthesis. Its most notable application is in the highly enantioselective alkylation of glycine derivatives under phase-transfer conditions, a key step in the synthesis of unnatural α-amino acids. The rigid, well-defined chiral environment provided by the quinidine scaffold is crucial for inducing high enantiomeric excess in the products. It is a cornerstone reagent in asymmetric synthesis methodologies. Beyond its catalytic role, N-Benzylquininium chloride serves as a valuable chiral building block or intermediate for the preparation of more complex chiral catalysts and ligands. Its stability and ionic nature also make it a subject of study in chiral recognition and separation science.