Sponges provide the largest number of biologically active natural products known from the marine environment and continue to be a very well studied phylum of marine fauna. The Mediterranean sponge Aplysina aerophoba accumulates brominated isoxazoline alkaloids such as Aplysinamisin‐1, Aerophobin‐2, Isofistularin‐3 and the biotransformation product Aeroplysinin‐1, which possesses, for example, antibiotic and cytotoxic propertie...