Synthesis of the ABC and IJ ring fragments of yessotoxin

Synthesis of a 6/6/6 tricyclic ether system (3) corresponding to the ABC ring fragment of yessotoxin (1) has been achieved via coupling of a triflate and a 2-lithiofuran followed by intramolecular hetero-Michael addition. The IJ ring fragment (4) of 1 was readily synthesized via successive Sharpless epoxidation and 6-endo cyclization of the resulting vinyl epoxide.