Six New Antimicrobial Metabolites from the Deep-Sea Sediment-Derived Fungus Aspergillus fumigatus SD-406.

Six new metabolites, including a pair of inseparable mixtures of secofumitremorgins A ( 1a ) and B ( 1b ), which differed in the configuration of the nitrogen atom, 29-hydroxyfumiquinazoline C ( 6 ), 10 R -15-methylpseurotin A ( 7 ), 1,4,23-trihydroxy-hopane-22,30-diol ( 10 ), and sphingofungin I ( 11 ), together with six known compounds ( 2 - 5 and 8 - 9 ), were isolated and identified from the deep-sea sediment-derived fungus Aspergillus fumigatus SD-406. Their structures were determined by detailed spectroscopic analysis of NMR and MS data, chiral HPLC analysis of the acidic hydrolysate, X-ray crystallographic analysis, J -based configuration analysis, and quantum chemical calculations of ECD, OR, and NMR (with DP4+ probability analysis). Among the compounds, 1a / 1b represent a pair of novel scaffolds derived from indole diketopiperazine by cleavage of the amide bond following aromatization to give a pyridine ring. Compounds 1 , 4 , 6 , 7 , 10 and 11 showed inhibitory activities against pathogenic bacteria and plant pathogenic fungus, with MIC values ranging from 4 to 64 μg/mL.