STEREOSELECTIVE CONSTRUCTION OF THE DITERPENE PART OF INDOLE ALKALOIDS, RADARINS, BY WAY OF INTRAMOLECULAR DIELS-ALDER REACTION

The tricyclic diterpene part of the indole alkaloids, radarins A-D (1- 4), was synthesized in a highly stereoselective manner by the exploita tion of an intramolecular Diels-Alder reaction. ,3,4,4a,5,6,7,8-octahy dro-2-oxo-5-vinylnaphthalene (7) was converted into trienes 28 and 29, possessing (1E,3E)- and (1E,3Z)-4-(phenylthio)butadiene moieties. Int ramolecular [4 + 2] cycloadditions of 28 and 29 yielded tricyclic 32 s electively, producing the ABC carbon skeleton of radarins.