The palladium catalyzed enyne cycloisomerization reaction in a general approach to the asymmetric syntheses of the picrotoxane sesquiterpenes. Part I. First-generation total synthesis of corianin and formal syntheses of picrotoxinin and picrotin

The palladium-catalyzed enyne cycloisomerization is used as a key ring-form ing process for the obtention of the cis-fused hydrindane carbon skeleton c haracteristic of the picrotoxanes sesquiterpenes. The enyne cycloisomerizat ion product is suitably functionalized so that each carbon of the hydrindan e core can be modified to permit access to many members of the picrotoxane family, not only to picrotoxinin itself. Part I of this report describes ou r first-generation approach to the picrotoxane sesquiterpenes as illustrate d by the asymmetric synthesis of corianin and the asymmetric formal synthes es of picrotoxinin and picrotin. A new catalyst system to effect the cycloi somerization emerged from this study. Subsequent work proved the generality of this catalyst system.