Gold(I)-catalyzed cycloisomerization of 1,7- and 1,8-enynes: application to the synthesis of a new allocolchicinoid.

Gold(I)-catalyzed cycloisomerization of 1,7- and 1,8-enyne propargylic acetates afforded cyclopropyl derivatives containing seven- and eight-membered rings, respectively. This reaction was used for the synthesis of a new allocolchicinoid having a cyclopropane ring fused to the B seven-membered ring at the C6-C7 positions.