Three new metabolites having a spiro-heterocyclic γ-lactam core, cephalimysins B−D (1−3), as well as FD-838 (4) were isolated from a culture broth of Aspergillus fumigatus that was originally separated from the marine fish Mugil cephalus. Compounds 1−3 are the diastereomers of 4. Compounds 2 and 3 exhibit an opposite absoluteconfiguration at a spiro carbon to that of other known naturally occurring