Dihydrohymenialdisines, new pyrrole-2-aminoimidazole alkaloids from the marine sponge Cymbastela cantharella

In our investigation of bioactive marine natural products, we revisited an ethanolic extract of the New Caledonian sponge Cymbastela cantharella. Four new natural compounds (3–6) were isolated and their structural determinations as dihydrohymenialdisine derivatives were achieved by spectral data analysis and chemical conversion. These products did not show any activity in the Polo Like kinase bioassay, demonstrating thus the importance of the unique structure of hymenialdisine, known as an improved kinase inhibitor.