Stereoselective enol tosylation:: Preparation of trisubstituted α,β-unsaturated esters

The stereoselective preparation of (E)- or (Z)-trisubstituted alpha,beta-unsaturated esters in three steps from N-protected glycine is presented. The key step in the synthesis is the highly selective enol tosylation of gamma-amino beta-keto esters. The enol tosylates are stable. crystalline compounds that undergo smooth and effective Suzuki-Miyaura coupling reaction with a variety of aryl boronic acids.