Improved procedure for Juliá–Colonna asymmetric epoxidation of α,β-unsaturated ketones: total synthesis of diltiazem and TaxolTM side-chain

Abstract

Poly-L-leucine catalyses the asymmetric epoxidation of enones 1–6 efficiently in a non-aqueous medium to provide the epoxy ketones 7–12 (70–91% yield; 80 to 95% ee). The strategy was used to make diltiazem 16 and the Taxol^TM side chain 23 in single enantiomer form.