Stereoselective synthesis of hyptolide and 6-epi-hyptolide

The first stereoselective syntheses of the naturally occurring, α,β-unsaturated lactone hyptolide 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 Brownʹs asymmetric allylation, a Carreiraʹs asymmetric ethynylation and a ring closing metathesis.