Structure–selectivity studies on catalysts for the phase-transfer catalysed asymmetric alkylation of glycine imine esters

In this paper, we describe the synthesis of a series of chiral quaternary ammonium salts with core structures that are closely related to the cinchona alkaloid, cinchonine. By employing these salts as asymmetric phase-transfer agents in the benzylation of a glycine imine, an optimal catalyst structure is identified.