Studies aimed at the synthesis of angularly fused tricyclopentanoid have been performed. The key step of the sequence utilized intramolecular diyl trapping reaction via cyclopropanation of alkylidene carbene. When a variety of different substrates were subjected to annulation, methylene tricyclo [$5.2.1.0^{1,5}$] decane system was obtained, instead of angular triquinane that initially we expected. It seemed that the stability of transition state did a significant role in determining the regiochemical course of diyl trapping reactions.
Although attempts to convert acyclic ketone bearing two double bonds to angularly fused tricyclopentanoid, was not fruitful, we developed a new method for the preparation of bridged tricyclic compound.