The Asymmetric Synthesis of 4,4-Dimethyl-3-Substitutedbutyrolactones

Abstract

Chiral 4,4-dimethyl-3-phenyl and 3-(3-oxobutyl)butyrolactones have been prepared in high enantiomeric excesses by a mild acid catalysed cleavage and lactonisation of the Michael adducts obtained from asymmetric additions of isopropenyl magnesium bromide to α,β-unsaturated carboxylic amides derived from 1-ephedrine.