gambierol analogues have been prepared from an advanced intermediate of our totalsynthesis of gambierol and investigated for their toxicity against mice, thus providing the first systematic structure-activity relationships (SAR) of this polycyclic ether class of marine toxin. The SAR studies described herein clearly indicate that 1) the C28=C29 double bond within the H ring and the unsaturated side chain
toxin, isolated as a toxic constituent from the marine dinoflagellate Gambierdiscus toxicus. We describe here the synthesis and biologicalevaluation of structural analogues of gambierol. The present preliminary structure-activity relationship studies clearly indicate that the H ring functionality and the unsaturated sidechain of gambierol are crucial for its potenttoxicity.