Abstract: The present invention relates to novel biologically active compounds from fungi of the species Ganoderma pfeifferi DSM 13239, processes for their preparation, and their use. From the fruit body and mycelium of the species Ganoderma pfeifferi DSM 13239, extracts can be obtained which have antimicrobial activity and are suitable as preserving agents, for pharmaceutical and cosmetic preparations, for controlling infections, and for use in fish breeding. Antimicrobially active substances called ganomycins having activity against multiresistant germs are isolated from the extracts. The total synthesis of the ganomycins and their derivatization enables their use an antibiotics.