3.10 Alkaloid-Derived Auxiliaries: Ephedra Alkaloids
This chapter covers the synthesis and application of chiral auxiliaries derived from the Ephedra alkaloids. The first half of the chapter is focused on the biosynthetic origins of the Ephedra and their use in acyclic chiral auxiliaries: the use of Ephedra of β -hydroxyhydrazones as developed by Takahashi, asymmetric reductions catalyzed by Ephedra derivatives, Myers’ pseudoephedrine-based asymmetric alkylation, and the Abiko–Masamune chiral auxiliary for the creation of antialdol subunits. The section on acyclic chiral auxiliaries also briefly covers the use of Ephedra amides in the Tsuji–Trost reaction and in diorganozinc reactions. The latter half of the chapter addresses cyclic chiral auxiliaries including Meyers’ oxazolines, oxazolidines, Evans’ oxazolidinones, and other heterocycle systems.