Sponge's molecular diversity through the ambivalent reactivity of 2-aminoimidazole: A universal chemical pathway to the oroidin-based pyrrole-imidazole alkaloids and their palau'amine congeners

The plausible biogenetic mechanism proposed in this communication clarifies the chemical pathway leading to over 60 polycyclic pyrrole-imidazole marine alkaloids isolated from more than 20 different species of various genera (Agelas, Hymeniacidon, Axinella, Acanthella, Cymbastella, Phakellia...) of sponges. The tautomerism and ambivalent reactivity of 2-aminoimidazole precursors provide a consistent chemical pathway explaining the intriguing formation of all the compounds of this class. The mechanistic proposal proposed here for the first time is unique in the sense that the chemical pathway is universal and therefore provides fertile intellectual ground for the study of the enzymatic mechanism involved in this system.