Unified Enantioselective, Convergent Synthetic Approach toward the Furanobutenolide-Derived Polycyclic Norcembranoid Diterpenes: Synthesis of a Series of Ineleganoloids by Oxidation-State Manipulation of the Carbocyclic Core

Late-stage synthetic efforts to advance the enatio- and diastereoselectively
constructed [6,7,5,5]-fused tetracyclic scaffold toward the polycyclic
norditerpenoid ineleganolide are disclosed. The described investigations
focus on oxidation-state manipulation around the central cycloheptane
ring. Computational evaluation of ground-state energies of dihydroineleganolide
is used to rationalize empirical observations and provide insight
for further synthetic development, enhancing the understanding of
the conformational constraints of these compact polycyclic structures.
Advanced synthetic manipulations generated a series of natural product-like
compounds termed the ineleganoloids.