Stereoselective synthesis of the octahydronaphthalene unit of integramycin via an intramolecular Diels-Alder reaction

The racemic cis-decalin core fragment 30 of integramycin was synthesized by a sequence involving a highly diastereoselective intramolecular Diels-Alder reaction of triene 24. A remarkable switch in stereoselectivity occurred upon changing the dienophile unit of 24 from (Z)- to (E)-geometry.