Total synthesis of (+/-)-asteriscanolide.

The total synthesis of asteriscanolide (1) has been achieved by taking advantage on an intermolecular Pauson-Khand cycloaddition and a ring-closing metathesis as key bond-forming transformations. The approach incorporates the cyclooctane stereogenic center prior to ring formation. Interestingly, the ring-closing metathesis generates a new eight-membered ring with an "in-out" intrabridgehead relationship.