Highly Enantioselective Protonation of Thiol Ester Enolates

Abstract

Impressive enantiomer excesses of 99% were achieved in the protonation of thioester enolate 2, prepared from racemic 1, with the chiral proton sources (−)- and (+)-N-isopropylephedrine ((−)-3 and (+)-3). This large-scale procedure allows access to many enantiopure terpenoids.