Antibiotic LP237-F8 is the main cytotoxic metabolite isolated from the liquid cultures of the fungus Tolypocladium geodes. Complete 1H and 13C NMR resonance assignments and sequencing of the peptide was achieved by extensive high-field 2D NMR spectroscopy. The N- and C-terminals of LP237-F8 are protected with a capryloyl unit and the amino alcohol leucinol, respectively. This linear peptide is a new member of the peptaibol class of natural products, containing the unusual amino acids R-aminoisobutyric acid (Aib) and R-amino-R-ethyl-n-pentanoic acid (R-ethylnorvaline, R-EtNor).