Tyrokeradines C-F, New Bromotyrosine Alkaloids from the Verongid Sponges

Four new bromotyrosine alkaloids, tyrokeradines C-F (1-4), have been isolated from Okinawan marine sponges of the order Verongidae. The structures of 1-4 were elucidated on the basis of spectroscopic data. Tyrokeradines C (1) and D (2) are new bromotyrosine alkaloids possesing an imidazole ring, while tyrokeradines E (3) and F (4) are new bromotyrosine alkaloids possesing a cyano group.