Total synthesis of natural and non-natural Δ(5,6)Δ(12,13)-jatrophane diterpenes and their evaluation as MDR modulators.

We report the details of the total synthesis of natural and non-natural jatropha-5,12-dienes. The successful tactic for the assembly of the strained trans-bicyclo[10.3.0]pentadecane scaffold employed a B-alkyl Suzuki-Miyaura cross-coupling for the formation of the C5/C6 double bond and a ring-closing metathesis for the construction of the C12/C13 double bond. The key step of the synthesis of the cyclopentane fragment, an uncatalyzed intramolecular carbonyl-ene reaction, was studied computationally by DFT calculations. The members of the ensemble of synthetic natural and non-natural jatrophanes were subsequently examined as modulators for the ABCB1, ABCG2, and ABCC1 efflux proteins, which are associated with multidrug resistance in cancer chemotherapy.