Asymmetric synthesis of optically active threo- and erythro-pyrrolidinylbenzyl alcohol by the highly stereospecific arylation of (S)-proline and the subsequent highly diastereoselective reduction of the α-amino ketone

Abstract

Optically active α-amino phenyl ketones in 92–94% enantiomeric excess (e.e.) were obtained from the stereospecific arylation of (S)-proline or its derivatives by Friedel–Crafts reaction or by Grignard reaction. The subsequent complementary diastereoselective reductions of the α-amino ketone afforded respectively (S)- and (R)-α-[(S)-pyrrolidin-2-yl]benzyl alcohol in 93–100% e.e. and in 100% diastereoisomeric excess. The stereochemical course of the reduction of the α-amino ketone is discussed.