Total Synthesis of (-)-Phorbaketal A

A convergent asymmetric total synthesis of phorbaketal,A was achieved in 10 steps through a Au(I)-catalyzed intramolecular spiroketalization reaction of an alkyne, diol intermediate prepared from (R)-catvone and geranial. The spirciketalization reaction was ratio, and stereoselective and was accompanied by isomerization of an exo-olefin into the trisubstittned olefin to form a unique spiroketal structure of phorbaketals.