On the Development of Pseudoephenamine and Its Applications in Asymmetric Synthesis

Pseudoephedrine is well established as a chiral auxiliary in the alkylation of amide enolates to form tertiary and quaternary carbon stereocenters. However, due to its facile transformation into the illegal narcotic methamphetamine, pseudoephedrine is either illegal or highly regulated in many countries, which limits its use in academic and industrial settings. To address this issue, pseudoephenamine has been developed as a replacement for pseudoephedrine in organic synthesis. This new auxiliary suffers no regulatory issues and exhibits several practical advantages over pseudoephedrine, including the high diastereoselectivities observed in alkylation reactions forming quaternary carbon stereocenters, the propensity for pseudoephenamine amides to be free-flowing crystalline solids, and the sharp, well-defined peaks that typically compose the 1H NMR spectra of these amides.