MARRUBINONE-A AND MARRUBINONE-B, NEW LABDANE DITERPENOIDS FROM MARRUBIUM-ASTRACANICUM (LABIATAE)

Two new labdane diterpenoids, marrubinones A (1) and B (2), were isola ted from aerial parts of Marrubium astracanicum collected in Turkey. C ompounds 1 and 2 were mostly characterized by two-dimensional NMR. For determination of the absolute configuration, the modified Mosher's me thod was applied to the 12-hydroxy forms of 1 and 2. Compounds 1 and 2 are pentacyclic diterpenoids, which differ from each other only in th e stereochemistry at C-13, and they were identified as 9 alpha,13S:15, 16-diepoxy-12-oxo-14-labden-19,6 beta-olide and 9 alpha,13R:15,16-diep oxy-12-oxo-14-labden-19,6 beta-olide, respectively.