Studies toward the total synthesis of gambieric acids, potent antifungal polycyclic ethers: Convergent synthesis of the CDEFG-Ring system

(Chemical Equation Presented) A convergent synthetic route to the CDEFG-ring system of gambieric acids, potent antifungal polycyclic ether marine natural products, has been developed. The present synthesis features convergent union of the CD- and G-rings through esterification, formation of the E-ring as a lactone form, stereoselective allylation to set the C₂₆ stereocenter, and ring-closing metathesis reaction to construct the nine-membered F-ring.