A practical and enantiospecific conversion of d-galactose to a substituted α,β-unsaturated δ-lactone synthon

A multi-gram synthesis of a substituted α,β-unsaturated δ-lactone synthon, 1, was developed from commercially available d-galactose. The use of a Horner-Wadsworth-Emmons reaction was able to furnish, with Z selectivity, the enone ester that spontaneously lactonised to provide enantiomerically pure 1.