Ga(III)-catalyzed cycloisomerization strategy for the synthesis of icetexane diterpenoids: total synthesis of (+/-)-salviasperanol.

[reaction: see text] A general approach to the tricyclic core of the icetexane natural products via the cycloisomerization of alkynyl indenes using GaCl(3) is presented. This strategy provides an efficient synthesis of the natural product salviasperanol and sets the stage for access to other members of this family of diterpenoids.