Synthetic studies towards the total synthesis of Herquline A

Abstract

The highly strained bowl-shaped pentacyclic structure of herquline A has rendered it one of the most difficult problems in organic synthesis yet to be solved. Herquline A remains as a four-decade-old challenge in the synthetic community and has been well documented in 5 Ph.D. dissertations and 6 reports on its simpler congeners. The uniqueness of herquline A arises from the C-N bond connectivity and the key challenge is to form the mentioned C-N bond through unique and inventive synthetic strategies. Through the recently proposed biosynthesis of herqulines A, B, and C by Tang and coworkers, these compounds have been re-highlighted in the synthetic community, and the quest to access herquline A continues. In this thesis, through innovative and novel synthetic routes, we for the first time, showcase the first pentacyclic structure of herquline A. Moreover, we highlight the synthesis of 1-hydroxyherquline A and the scope for the reactivities of 1-hydroxyherquline A for the completion of the total synthesis.