Synthetic Studies of Sesquiterpenes with the Dunniane Skeleton
The first synthetic approach to the entire carbon skeleton of the sesquiterpenes dunniane and cumacrene has been developed. The sequence features a [2+2] photochemical reaction of a chiral 2(5H)-furanone with ethylene to form the cyclobutane, a Meyer–Schuster-type rearrangement of an α-acetylenic alcohol to an α,β-unsaturated aldehyde, and a microwave-assisted Diels–Alder reaction of an elaborated dienamine with methyl acrylate to construct the six-membered ring with the desired 1,4-substitution pattern.