Sequences of Acretocins, Peptaibiotics Containing the Rare 1‐Aminocyclopropanecarboxylic Acid, from Acremonium crotocinigenum CBS 217.70

Dedicated to the memory of Walter Gams (1934-2017), a great mycologist who isolated strain CBS 217.70 and described the species Acremonium crotocinigenumSeven non-ribosomal polypeptide antibiotics, named acretocins (ACRs), were obtained from Acremonium crotocinigenum strain CBS 217.70.The microheterogeneous peptide mixture was isolated from the culture broth by column chromatography on XAD-2 and Sephadex LH-20.Sequences were determined by ESI-MS n and amino acid composition by GC/MS.Besides Gly, Leu, and Ala, the peptides contain the nonproteinogenic amino acids Acc (1-aminocyclopropane-1-carboxylic acid), Aib (α-aminoisobutyric acid), Iva (isovaline), Pip (pipecolic acid), β-Ala (β-alanine), and a C-terminal heterocyclic residue N-peptido-1-isobutyl-2-(2,3,4,6,7,8-hexahydro-1-pyrrolo[1,2-a]pyrimidinio)ethylamine (abbreviated X).After vigorous acidic total hydrolysis, release of L-Iva besides D-Iva was established by chiral GC/MS.ACRs show in part sequence identity with neoefrapeptins.Two sequences, ACR-5(6), are new: Ac-L-Pip-Aib-L-Pip-D-Iva-D-Iva(Aib)-L-Leu- β-Ala-Gly-Acc-Aib-L-Pip-Aib-L-Ala-L-Leu-L-Iva-X.The taxonomy of fungal producers of acretocins and neoefrapeptins is compared.