NOVEL OPENING OF 15,16-EPOXYBEYERANE DITERPENES IN RUTHENIUM-CATALYZED REARRANGEMENT PROCESSES - FORMATION OF ANTHERIDIOGEN-LIKE RINGS

Rearrangement reactions of 15,16-epoxybeyeranes with acetoxy substitue nts at C-12 were carried out by treatment with ruthenium acetylacetona te. The stereochemistry of the acetoxy substituent group on C-12 decis ively influences the process. In the case of the axial substituent, it aids in the stabilization of intermediate structures derived from an electron deficiency on C-15 that allows the formation of 8(15-->9)-abe o and 8(14-->9),13(12-->16)-diabeo compounds. This promotion of a posi tive charge on C-15 of the beyerene skeleton has not yet been explored in classical studies of rearrangements of tetracyclic diterpenes. The formation of some chlorinated compounds, produced by the solvent used (CHCl3), was also observed in this process. When the starting product had a C-12 acetoxy equatorial substituent, only migrations of the ace toxy group and some nucleophilic substitution processes were observed. The pathways of the rearrangements were proposed on the basis of find ings obtained from rearrangement of C-12 deuterium labeled substrates.