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DOI: 10.1055/s-0033-1348666
New Fiscalin, Tryptoquivaline, and Fumiquinazoline Analogues from an Endophytic Isolate of Neosartorya aureola
In the course of our ongoing investigations of endophytes from crop plants, an isolate of Neosartorya aureola (ENDO-3483) was obtained from a healthy stem of Secale cereale (Rye grass) harvested from a crop field near Kilbourne, IL. The crude extract of solid-substrate fermentation cultures of this isolate exhibited antifungal activity against F. verticillioides. Chemical separation of this extract resulted in the isolation of five new fiscalin analogues, a new fumiquinazoline analogue, and three new tryptoquivaline analogues. Multiple known compounds, including sterigmatocystin, nortryptoquivaline, and tryptoquivalines A, B, I, and N were also isolated and/or identified as components of individual chromatographic fractions. The groß structures of the new analogues were established using various 1D and 2D NMR techniques. Relative configurations were assigned by interpretation of NOESY data and/or X-ray diffraction analysis. Absolute configurations of amino acid units present in these metabolites were determined by GCMS analysis of trifluoroacetyl-(S)-2-butyl ester derivatives of the individual amino acids obtained upon acid hydrolysis. A combination of these results, together with X-ray crystallography, and/or electronic circular dichroism (ECD) data allowed the assignment of the absolute configurations of the new analogues.