Intermolecular Radical Cation Diels–Alder (RCDA) Reaction of Bicyclooctadienes: Biomimetic Formal Total Synthesis of Kingianin A and Total Syntheses of Kingianins D, F, H, and J

Three endo bicyclooctadienol dimers corresponding to kingianins A and H, D, and F and J were obtained by the intermolecular radical cation Diels–Alder (RCDA) reaction. Each isomer was cleanly isolated without the aid of preparative HPLC. Kingianins D, F, H, and J were prepared by way of these intermediates from commercially available materials in 10, 13, 9, and 17 steps, respectively. Kingianin A has already been prepared from one of these compounds. Completion of the synthesis of kingianin H relied on Manchand’s one-step, three-carbon homologation.