Asperelines A−F, Peptaibols from the Marine-Derived Fungus Trichoderma asperellum

Fermentation of the marine-derived fungus Trichoderma asperellum, collected from the sediment of the Antarctic Penguin Island, resulted in the isolation of six new peptaibols named asperelines A−F (1−6), which are characterized by an acetylated N-terminus and a C-terminus containing an uncommon prolinol residue. Structures were determined by extensive 1D and 2D NMR (1H−1H COSY, HMQC, HMBC, NOESY) spectroscopic data analysis combined with ESIMS/MS fragmentation. The absolute configurations of the amino acid residues possessing a chiral α-carbon and of the prolinol residue were determined to be l and S, respectively, using a new method of 1H NMR spectroscopic comparison of complexes formed between the chiral reagent Ru(d4-Por*)CO and amino acids derived from the peptaibols with those formed with reference standards.