involving the 6-7-6-5 polycyclic carbon framework with various functional groups. The stereoselectivesynthesis of the right-hand segment of tubiferal A was achieved on the basis of the cyclopentene annulation method and the semi-pinacol rearrangement reaction of an epoxy alcohol for constructing the trans-fused 6-5 bicyclic skeleton possessing two quaternarycarbonatoms at the angular positions.