Synthetic Studies towards Communesins: Diastereoselective Oxidative Rearrangement of Aurantioclavine Derivatives

Communesins are a class of heptacyclic indole alkaloids that contain two aminal moieties and two contiguous quaternary carbon centers. We have investigated the construction of the pentacyclic skeleton of the communesins by employing the oxidative rearrangement of aurantioclavine derivatives, which are believed to be biosynthetic intermediates of the polycyclic communesin alkaloids. The quaternary C-7 carbon center was constructed in a stereoselective manner, whereas the installation of the C-11 stereocenter requires an epimerization process. The isolation of a 2-ethoxyindolenine prior to the reduction of the nitro group and cyclization steps was critical to the success of this strategy. The pentacyclic skeleton of the communesins has been prepared by the oxidative rearrangement of aurantioclavine derivatives, which are believed to be biosynthetic intermediates of the communesin alkaloids. The quaternary C-7 carbon center was constructed in a stereoselective manner, and the isolation of a 2-ethoxyindolenine intermediate was critical to the success of the strategy