Stereoselective synthesis of cis-2,5-disubstituted THFs: application to adjacent bis-THF cores of Annonaceous acetogenins.

The iodocyclization of γ,δ-unsaturated alcohols in the presence of a silyl enol ether produced cis-2,5-disubstituted tetrahydrofurans in one pot via siloxy intermediates. N-Iodosuccinimide (NIS) effectively worked as an activator of the double bonds in the substrates and the silyl enol ether. Application to an expedient synthesis of the adjacent bis-tetrahydrofuran core of Annonaceous acetogenins with a cis/threo/cis relative stereochemistry is also described.

Asymmetric total synthesis of clavolonine.

The asymmetric total synthesis of clavolonine (1) has been achieved based on chiral auxiliary multiple-use methodology. Our synthetic route features stereoselective transformations on the cyclohexane ring utilizing the steric environment of the chiral auxiliary and an intramolecular Mannich reaction to construct the fused ring system.