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.