Convergent synthesis of the FGHI ring system of yessotoxin: stereoselective construction of the G ring

A convergent synthetic route to the FGHI ring system of yessotoxin, a marine ladder polyether, has been developed. The synthesis features convergent coupling of the diol and the aldehyde to form alpha-cyano ethers via acetal formation followed by ring closing metathesis and reductive etherification to construct the oxocane ring G and tetrahydropyran ring H, respectively. The beta-methyl group on the G ring was stereoselectively introduced by alkylation of the corresponding ketone. (c) 2005 Elsevier Ltd. All rights reserved.