Enantioselective total synthesis of 3-epi-ottelione A

An enantioselective total synthesis of (+)-3-epi-ottelione A (2), the earlier proposed stereostructure of the antitumor natural product ottelione A (4), was achieved for the first time starting from the known tetracyclic compound 9. The synthesis involves the following three crucial steps: (i) a coupling reaction of aldehyde 8 and aryllithium 7 to introduce the aromatic portion, (ii) base-induced lactol-opening/epimerization at the C1 position of 6 to deliver the requisite hydrindane 15, and (iii) Corey-Winter's reductive olefination of the cyclic thiocarbonate 19 to install the C5-C6 double bond.