Enantioselective synthesis of natural (−)-tochuinyl acetate, (−)-dihydrotochuinyl acetate and (+)-β-cuparenone using both enantiomers of the same building block

The first enantioselective synthesis of tochuinyl acetate and dihydrotochuinyl acetate, two natural marine products isolated from Tochuina tetraquetra and Gersemia rubiformis, has been achieved starting from an enantiopure building block. The key feature of the present synthesis is complete control of two vicinal quaternary stereogenic centers present in the natural products and elucidation of their absolute stereochemistry, which was previously unknown. Furthermore, starting from the enantiomer of the same building block, the applied methodology provided a new approach towards natural (R)-(+)-β-cuparenone.