Title: Efforts toward the Total Synthesis of Cyclocitrinol
Description: Natural products featuring bridged seven- and eight-membered ring systems are relatively rare in nature; however, due to their interesting biological activity, they are commonly found in pharmaceuticals. Despite their importance, no general method to access bicyclic ring systems exists, thus the de novo synthesis of these complex molecules is often a significant challenge. It was with this in mind that we launched our efforts towards the first total synthesis of cyclocitrinol, a unique steroid with a fused ring system possessing a rare bicyclo[4.4.1]undec-7,10-diene A/B ring with a bridgehead double bond. Using knowledge gained from previous model studies of a strain-accelerated tandem Ireland-Claisen/Cope rearrangement to assemble the ABC tricyclic core, two approaches towards the completion of the molecule were explored: 1) an Ireland-Claisen/Cope/Claisen rearrangement followed by RCM and 2) a 1,3-allylic transposition/RCM. Of these approaches, the later, led to the completion of the ABCD tetracyclic core and installation of the fully elaborated C17 side-chain.