Some reactions of the diterpene marrubiin and its congeners

Abstract

The dehydration and catalytic hydrogenation of marrubiin have been studied and structures assigned to the products. In the absence of pyridine dehydration of marrubiin with phosphorus trichloride appears to yield exclusively the Δ⁹⁽¹¹⁾-olefin whereas in its presence the Δ⁸-isomer predominates. During extraction of marrubiin (I) from Marrubium vulgare two further diterpenoids, marrubenol (XVI) and the hemiacetal (XIV), have been isolated.