Towards a Biomimetic Synthesis of the Marine Alkaloids Papuamine and Haliclonadiamine: Model Studies

A plausible biosynthetic pathway for the isomeric marine alkaloids papuamine and haliclonadiamine via the double tandem ene cyclisation of a tetraenediimine is proposed. Initial model studies directed toward the biomimetic synthesis of these alkaloids are described which illustrate that the Lewis acid-promoted ene cyclisation of methyl-2-(methoxycarbonyl)dodeca-2,8-dienoate is critically dependent on the Δ-8 geometry.