β‐cyclodextrin‐immobilized (4<i>S</i>)‐phenoxy‐(<i>S</i>)‐proline as a catalyst for direct asymmetric aldol reactions

Abstract

beta-Cyclodextrin-immobilized (4S)-phenoxy-(S)-proline was prepared conveniently by simply heating the amino acid and beta-cyclodextrin in ethanol-water (1/1, v/v) and removal of the solvent. This proved to be an efficient catalyst for direct asymmetric aldol reactions, and the catalyst could be recycled four times without loss of enantioselectivity.