Stereoselective total synthesis of (3 Z )- and (3 E )-elatenynes.

We describe here the highly stereoselective total synthesis of the Laurencia C 15 acetogenins (3 Z )- and (3 E )-elatenynes having a 7,12-dibromo-6,9- cis -10,13- cis adjacent bis-tetrahydrofuran (THF) core. The present synthesis features a highly stereoselective, protecting group-dependent, chelate-controlled intramolecular amide enolate alkylation (IAEA) for the synthesis of key intermediate 7-hydroxy-6,7- cis -6,9- cis -THF intermediate 10, deployment of the sequential ate complex ( n -BuLi/DIBAL-H) reduction/Keck allylation/cross metathesis (CM) protocol for the stereoselective introduction of the C(10)-C(15) unit, a sequential Sharpless asymmetric dihydroxylation (SAD)/intramolecular Williamson etherification for the construction of the 10,13- cis -THF ring, and a modified Nakata chloromethanesulfonate-mediated S N 2 displacement for the 7,12-dibromo functionality. Furthermore, our strategy based on chelate-controlled IAEA methodology would provide access to any member of the C 15 adjacent bis-THF acetogenin class.