A convergent coupling strategy for the formation of polycyclic ethers: Stereoselective synthesis of the BCDE fragment of brevetoxin A

A stereoselective synthesis of the BCDE fragment of brevetoxin A has been completed. ant Glycolate aldol, glycolate alkylation, and ring-closing metathesis reactions were employed as key bond-forming events. A convergent assembly strategy was employed that relied on a Horner-Wadsworth-Emmons union of two complex fragments. Subsequent cyclization and dehydration led to efficient generation of an intermediate endocyclic enol ether, which was advanced to a tetracyclic fragment.