Marine sponges are the source of the greatest diversity of marine natural products. Among these is the pyrrole–imidazole alkaloid family, where the common skeleton is observed in oroidin 1. 1 Various modes of cyclisation give rise to a large number of natural products with different geometries and functionalizations. Many of these compounds display a broad range of biological properties including antibacterial, antiinflammatory, anticancer and antiviral activities. ...