Synthesis of aspergillide A from a synthetic intermediate of aspergillide B

The first synthesis of aspergillide A, a cytotoxin produced by a marine-derived fungus, has been achieved from a synthetic intermediate of aspergillide B by using a proline-mediated epimerization of a 2,6-trans-substituted tetrahydropyran-2-acetaldehyde intermediate into the corresponding cis-isomer via a retro-oxy-Michael/oxy-Michael sequence as the key transformation.