Stereoselective synthesis of hyptolide and 6-epi-hyptolide

Abstract The first stereoselective syntheses of the naturally occurring, α,β-unsaturated lactone hyptolide 1 and of its nonnatural epimer at C-6 are described. Ethyl l -lactate was the chiral starting material. Key steps of these syntheses were a Brown's asymmetric allylation, a Carreira's asymmetric ethynylation and a ring closing metathesis.