Synthesis of (±)-8-deisopropyladunctin B.

(±)-8-Deisopropyladunctin B, the deisopropyl form of adunctin B, which was isolated from the leaves of Piper aduncum (Piperaceae) collected in Papua New Guinea, was synthesized in 0.77% overall yield in 17 steps from 5,7-dimethoxycoumarin-3-carboxylate. The key step was our original stereoconvergent skeleton transformation from 1,2,2a,8b-tetrahydro-3H-benzo[b]cyclobuta[d]pyran-3-one to 1,2,4a,9b-tetrahydrodibenzofuran-4-ol with dimethylsulfoxonium methylide.