Mass Spectrometry-Guided Discovery of Multi- N -Methylated Cyclodecapeptides Auyuittuqamides E-H from Sesquicillium sp. QL0466.

Mass spectrometry-based dereplication and prioritization led to the discovery of four multi- N -methylated cyclodecapeptides, auyuittuqamides E-H ( 1 - 4 ), from a soil-derived Sesquicillium sp. The planar structures of these compounds were elucidated based on analysis of HRESIMS and NMR data. Absolute configurations of the chiral amino acid residues were assigned by a combination of the advanced Marfey's method, chiral-phase LC-MS analysis, and J -based configuration analysis, revealing that 1 - 4 contain both d- and l-isomers of N -methylleucine (MeLeu). Differentiation of d- and l-MeLeu in the sequence was achieved by advanced Marfey's analysis of the diagnostic peptide fragments generated from partial hydrolysis of 1 . Bioinformatic analysis identified a putative biosynthetic gene cluster ( auy ) for auyuittuqamides E-H, and a plausible biosynthetic pathway was proposed. These newly identified fungal cyclodecapeptides ( 1 - 4 ) displayed in vitro growth inhibitory activity against vancomycin-resistant Enterococcus faecium with MIC values of 8 μg/mL.