Enantioselective total synthesis of (+)-obtusenyne.

A total synthesis of the laurencia metabolite (+)-obtusenyne has been completed. The key steps include a Sharpless kinetic resolution and an asymmetric glycolate alkylation to establish the stereogenic centers adjacent to the ether linkage and a ring-closing metathesis reaction to construct the nine-membered ether without the aid of a cyclic conformational constraint. The synthesis was completed in 20 linear steps from commercially available 1,5-hexadiene-3-ol.