Stereocontrolled synthesis of trichodermatide A.

Hard core made easy: The pentacyclic core of trichodermatide A was stereoselectively synthesized from a bis(1,3-cyclohexanedione) derivative by a ring-closing reaction followed by an intramolecular ketal formation (see scheme; PPTS=pyridinium p-toluenesulfonate). The first total synthesis of trichodermatide A was then completed by the introduction of three hydroxy groups.