One-step synthesis of paclitaxel side-chain precursor: benzamide-based asymmetric aminohydroxylation of isopropyl trans-cinnamate

Abstract

A highly enantioselective (up to 97% ee) one-step synthesis of paclitaxel side chain precursor, (2R,3S)-isopropyl 3-benzamido-2-hydroxy-3-phenylpropionate has been achieved by osmium-catalyzed asymmetric aminohydroxylation of isopropyl trans-cinnamate with N-bromobenzamide as an oxidant/nitrogen source in the presence of (DHQ)(2)PHAL as a chiral ligand. Simple recrystallization of crude product (containing regioisomer and diol) from ethyl acetate gave the enantiomerically pure product. (C) 1999 Elsevier Science Ltd. All rights reserved.