Total Synthesis of Methyl Sarcophytoate, a Marine Natural Biscembranoid

The total synthesis of methyl sarcophytoate (<b>1</b>), a marine natural biscembranoid, has been achieved by the thermal Diels−Alder reaction between the 14-membered dienophile unit, methyl sarcoate (<b>2</b>), and the 14-membered diene unit <b>64</b>. Methyl sarcoate (<b>2</b>) was prepared using <i>n</i>-BuLi-Bu<sub>2</sub>Mg-mediated dithiane coupling, Kosugi−Migita−Stille coupling, and Grubbs ring-closing metathesis. The diene unit <b>64</b> was prepared using Sharpless asymmetric epoxidation, Grubbs ring-closing metathesis, 6-exo-tet epoxide opening, and <i>n</i>-BuLi-Bu<sub>2</sub>Mg-mediated Ito−Kodama cyclization. The final Diels−Alder reaction between <b>2</b> and <b>64</b> proceeded with high site, endo/exo, π-face, and regioselectivities. During this reaction, partial <i>E</i> → <i>Z</i> isomerization at the C4 position was observed.