19-Residue and 18-Residue Peptaibiotics Isolated from the Soil-Derived Fungus Trichoderma sp. XJ1083

Four previously undescribed peptaibotics, designated trichorzianines 1924B, 1910B, 1796, and 1777 (1-4), were obtained from the soil-derived fungus Trichoderma sp. XJ1083. Structural elucidation, including determination of absolute stereochemistry, was achieved by detailed interpretation of NMR spectra, tandem mass spectrometric analysis, and Marfey's derivatization. All compounds possess a conserved peptaibol framework with the sequence Ac-Aib¹-Ala²-Aib³-Aib⁴-Iva/Aib⁵-Gln⁶-Aib⁷-Aib⁸-Aib⁹-Ser¹⁰-Leu¹¹-Aib¹²-Pro¹³-Leu¹⁴-Aib¹⁵-Aib¹⁶-Gln¹⁷, a plausible biosynthetic pathway was proposed. Compounds 1-3 exhibited moderate inhibitory activity against Staphylococcus aureus and methicillin-resistant S. aureus, with MIC values of 32 and 64 μg/mL, respectively.