Two novel pyrrole-imidazole alkaloids from the Mediterranean sponge Agelas oroides

The novel pyrrole-imidazole alkaloids cyclooroidin (7) and taurodispacamide A (8) have been isolated from the Mediterranean sponge Agelas oroides, and their structures established from spectroscopic data. Although both these alkaloids may be conceived as derivatives of the C11N5 skeleton of the known oroidin (1), remarkably cyclooroidin (7) possesses the unprecedented N1/C9 connection. Taurodispacamide A (8) exhibited a good antihistaminic activity, tested on the isolated guinea pig ileum.