FORMAL TOTAL SYNTHESIS OF HEMIBREVETOXIN B VIA THE INTRAMOLECULAR ALLYLATION FOLLOWED BY RING-CLOSING METATHESIS

A formal total synthesis of hemibrevetoxin B (1) is described. Intramolecular allylation of α-chloroacetoxy ether 10, prepared from carboxylic acid 11 and alcohol 12, was carried out with MgBr 2 ·OEt 2 to give 27. Ring-closing metathesis of 27 furnished tetracycle 29, which was converted to a known synthetic intermediate 9, to complete a formal total synthesis of 1.