Mactanamide, a new fungistatic diketopiperazine produced by a marine Aspergillus sp.

Mactanamide (1), a new diketopiperazine containing the uncommon amino acid D-2,6-dihydroxyphenylalanine, has been isolated from the mycelium of an undescribed marine fungus of the genus Aspergillus. The new fungal strain was obtained from the surface of the brown marine alga Sargassum sp. collected near Mactan Island in the Philippines. The structure and absolute stereochemistry of I was determined by interpretation of spectral data, by comparison with model compounds, and by measurement of the CD spectra of its component amino acids.