A novel route to the F-ring of halichondrin B.: Diastereoselection in Pd(0)-mediated meso and C2 diol desymmetrization

[GRAPHICS] Both sigma and C-2 symmetric diol diacetates were synthesized via two-directional chain elongation. A palladium-mediated, ligand-controlled C-2 diol desymmetrization provided the desired tetrahydrofuran with the correct relative and absolute stereochemistries. Simple functional group manipulation led to the desired F-ring of halichondrin B. Desymmetrization of the meso substrate enantioselectively provided the diastereomer, leading to a refinement of our understanding of the transition state model.