Marine natural products from Pseudopterogorgia elisabethae:: Structures, biosynthesis, pharmacology, and total synthesis

In the late 1990s, the Caribbean octocoral Pseudopterogorgia elisabethae became the target of extensive chemical investigations leading to the isolation and characterization of a remarkable number of diterpenoid secondary metabolites. Most of these newly discovered compounds are based on so far unprecedented carbon skeletons and often feature unusual structural characteristics. Besides their exciting structures, many of these marine natural products display potent pharmacological activity against various diseases, for instance tuberculosis or cancer. Although at first glance it is not always evident, all structures are consistent with a biosynthesis pathway starting from geranylgeranyl phosphate to deliver via serrulatane intermediates an enormous variety of diterpenoid natural products. Thus, the organism Pseudopterogorgia elisabethae is capable of performing a kind of diversity-oriented synthesis creating stereochemical and structural complexity from simple precursors. The intricate molecular architecture of these natural products also drew the attention of synthetic chemists. Over the last few years considerable synthetic efforts have been made resulting in several total syntheses. Therefore, this class of diterpenoids is now also synthetically accessible, with cycloaddition reactions proving to be the ultimate tool for the construction of the carbon skeletons.