A new iron(III) chelator of coprogen-type siderophore from the deep-sea-derived fungus Mycosphaerella sp. SCSIO z059

Mycosphazine A ( 1 ), a new iron(III) chelator of coprogen-type siderophore, and mycosphamide A ( 2 ), a new cyclic amide benzoate, together with six known aryl amides ( 3−8 ), were isolated from the fermentation broth of the deep-sea-derived fungus Mycosphaerella sp. SCSIO z059. Alkaline hydrolysis of 1 afforded a new epimer of dimerum acid, mycosphazine B ( 1a ), and a new bi-fusarinine-type siderophore, mycosphazine C ( 1b ). The planar structures of the new compounds were elucidated by extensive spectroscopic data analysis. The absolute configurations of amino acid residues in 1a and 1b were determined by acid hydrolysis. And the absolute configuration of 2 was established by quantum chemical calculations of the electronic circular dichroism (ECD) spectra. Compound 1 is the first siderophore-Fe(III) chelator incorporating both L-ornithine and D-ornithine unites. Compounds 3−8 were reported as natural products for the first time, and the ¹H and ¹³C NMR data of 6 and 8 were assigned for the first time. Compounds 1 and 1a could greatly promote the biofilm formation of bacterium Bacillus amyloliquefaciens with the rate of about 249% and 524% at concentration of 100 μg·mL⁻¹, respectively.