Highly Efficient, Enantioselective Synthesis of (+)-Grandisol from a C2-Symmetric Bis(α,β-butenolide)

A new, very efficient, enantioselective synthesis of the sexual attracting insect pheromone (+)-grandisol has been developed, in which the key step is the double [2 + 2] photocycloaddition of ethylene to a bis(α,β-butenolide) readily available from d-mannitol. The C2 symmetry of the substrate and the appropriate protection of the central diol unit are the crucial features for the high diastereofacial discrimination during the cycloaddition process.