Progress Towards the Total Synthesis of Steroidal Natural Products Clionastatins A and B
A total synthesis of naturally occurring polychlorinated steroids, clionastatins A and B, was undertaken. Efforts were first directed at the synthesis of a truncated tricyclic steroid core and multiple synthetic routes were developed, many of which featured a Diels–Alder reaction. Ultimately, these efforts culminated in the successful synthesis of the clionastatin core. Efforts then focused on development of a bicyclic diene that would allow us to apply the successful Diels–Alder route to the synthesis of a tetracycle, which could be elaborated into clionastatin A. While a suitable diene was made and a tetracyclic cycloadduct was synthesized, the undesired stereochemistry of that cycloadduct suggests that an alternative route to the clionastatins may be necessary.