Synthesis of the Pyrrole-ImidazoleAlkaloids

This review article gives a detailed account on the chemistryof the pyrrole-imidazole alkaloids from marine sponges. The pyrrole-imidazolealkaloids share a key building block, oroidin being the underlyingstructural motif of a diverse range of exclusively marine alkaloids.After outlining the reactivity of 2-amino-4(5)-vinylimidazoles,biomimetic and non-biomimetic total syntheses of the non-cyclized,cyclized, and 'dimerized' pyrrole-imidazole alkaloidsdeveloped over the past 30 years are discussed in a comprehensivemanner. Beyond the identified pyrrole-imidazole alkaloids the theoreticalcyclization map based on oroidin contains many white spots and therebyopportunities to assemble novel pyrrole-imidazole alkaloids notobserved in nature before.