Ringschlussreaktionen an Pleiocarpa‐Alkaloiden

Abstract

Alkaloids with the pleiocarpin skeleton have been found to undergo ring closure on pyrolysis to give heptacyclic compounds with the kopsan (XI) carbon skeleton. Kopsinic acid (V), the main example, gave kopsanone (XIII). The structure XIII for kopsanone has been established by physical and chemical methods, degradation to the methine base XVII and reduction to kopsan (XI). A mechanism to explain these cyclizations is discussed.