Investigating Biogenetic Hypotheses of the Securinega Alkaloids: Enantioselective Total Syntheses of Secu'amamine E/ent-Virosine A and Bubbialine

The synthesis of the Securinega alkaloid secu'amamine E (ent-virosine A) has been accomplished for the first time in 12 steps and 8.5% overall yield. In addition, bubbialine has been prepared and characterized. These two alkaloids and bubbialidine, all featuring an azabicydo[2.2.2]-octane core, were rearranged to their azabicydo[3.2.1]octane congeners, a framework found in many Securinega alkaloids. These experiments suggest that azabicydo[2.2.2]octane derivatives rearranged azabicydo [3.2.1] octane products. could serve as intermediates in the biosynthesis of the rearranged azabicydo [3.2.1] octane products.