Ready Access to the Echinopines Skeleton via Gold(I)-Catalyzed Alkoxycyclizations of Enynes

The [3,5,5,7] tetracyclic skeleton of echinopines has been stereoselectively accessed through a gold­(I)-catalyzed alkoxycyclization of cyclopropyl-tethered 1,6-enynes. The key bicyclo[4.2.1]­nonane core of the enyne precursors was readily assembled by means of a Co-catalyzed [6 + 2] cycloaddition. Furthermore, the attempted alkoxycyclization of 1,5-enyne substrates revealed an uncovered cyclopropyl rearrangement that gives rise to [3,6,5,7] tetracyclic structures.