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

We describe here the highly stereoselective total synthesis of the C acetogenins (3)- and (3)-elatenynes having a 7,12-dibromo-6,9--10,13- 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--6,9--THF intermediate 10, deployment of the sequential ate complex (-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--THF ring, and a modified Nakata chloromethanesulfonate-mediated S2 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 adjacent bis-THF acetogenin class.

Total Synthesis and Structure Confirmation of (-)-Asimitrin, a C Annonaceous Acetogenin with a Hydroxylated Adjacent Bis-Tetrahydrofuran Core.

The total synthesis and structure confirmation of the potent cytotoxic agent (-)-asimitrin (), a C annonaceous acetogenin having a hydroxylated adjacent bis-tetrahydrofuran (THF) core, are described. The present synthesis features a highly stereoselective, chelate-controlled intramolecular amide enolate alkylation (IAEA) for the synthesis of key intermediate 17-hydroxy-16,17--16,19--THF , our direct ketone synthesis/l-Selectride reduction protocol for stereoselective introduction of the C(21)-C(34) unit, Sharpless asymmetric dihydroxylation (SAD), and internal Williamson etherification for construction of the 20,23--THF ring.

Highly Stereodivergent Construction of a C-Symmetric ,- and ,-2,6-Dioxabicyclo[3.3.0]octane Framework by Double Intramolecular Amide Enolate Alkylation: Total Synthesis of (+)-Laurenidificin and (+)-Aplysiallene.

The highly stereoselective construction of C-symmetric ,- and ,-2,6-dioxabicyclo[3.3.0]octane (fused -tetrahydrofuran) skeletons and has been accomplished via a novel stereodivergent double intramolecular amide enolate alkylation of common cyclization substrate through the judicious choice of "chelate" versus crown ether-promoted "nonchelate" control.