摘要:
[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.