Isolation and Total Synthesis of Albu­peptins A–D: 11‐Residue Peptaibols from the Fungus Gliocladium album

Abstract

Four new 11‐mer peptaibols, named albupeptins A–D (1–4), were isolated from cultures of the fungus Gliocladium album. Their structures were elucidated on the basis of 1D and 2D NMR spectroscopy, as well as ESI‐HRMSn analysis. The sequence of albupeptin A (1) was thus identified as Ac‐Aib1‐Aib2‐Val3‐Leu4‐Aib5‐Pro6‐Iva7‐Leu8‐Gln9‐Aib10‐Leuol11. Albupeptins B (2) and C (3) feature an exchange of Aib5 by Iva5 and of Aib1 by Iva1, respectively, and albupeptin D (4) contains both Iva1 and Iva5 residues. The stereochemistry of the isolated peptaibols 1–4 was unambiguously assigned by 1H NMR chemical shift analysis in conjunction with solid‐phase peptide synthesis. By using this approach, the absolute configuration of the Iva residues in albupeptins A (1) and C (3) was determined to be D, whereas albupeptins B (2) and D (4) feature an additional Iva5 residue with an L configuration. Thus, albupeptins B (2) and D (4) belong to the rare class of peptaibols that have both stereoisomers of Iva in the same sequence.

Longibramides A–E, Peptaibols Isolated from a Mushroom Derived Fungus Trichoderma longibrachiatum Rifai DMG‐3‐1‐1

“…Peptaibols were a family of linear peptides generally composed of 5–20 amino acid residues, characterized by N‐acyl terminus, C‐amino alcohol terminus, and a high proportion of nonproteinogenic amino acids such as α ‐aminoisobutyric acid (Aib) or isovaline (Iva) [5–12] . Peptaibols usually showed antibacterial, [6,7] antifungal, [6–9] antiviral [10] or cytotoxic activities [5,11,12] . The bioactivities of peptaibols were affected strongly by the number of amino residues, and enhanced with the increasing of the amino residues [13] .…”

“…The bioactivities of peptaibols were affected strongly by the number of amino residues, and enhanced with the increasing of the amino residues [13] . And species of the amino residues composed of the peptaibols also affected their bioactivities, Gln residues at the C‐terminus and the presence of Aib or Iva residues might improve the bioactivities of them [5,9,14,15] …”

Tulasporins A–D, 19-Residue Peptaibols from the Mycoparasitic Fungus Sepedonium tulasneanum

“…General: Specific rotation, Jasco P-2000 polarimeter; UV, Jasco V-560 UV/Vis spectrophotometer; CD, Jasco J-815 CD spectrophotometer; NMR, Agilent VNMRS 600 system; Size exclusion column chromatography, Sephadex LH 20 (Fluka, Germany); TLC, precoated silica gel F 254 plates; Peptaibols were visualized on TLC plates using a modified acidic ninhydrin reagent, as described previously [9]. 1 Antiphytopathogenic bioassay: Pure compounds were tested in a 96-well microtiter plate assay against Botrytis cinerea Pers., Septoria tritici Desm., and Phytophthora infestans (Mont.)…”

“…1 Antiphytopathogenic bioassay: Pure compounds were tested in a 96-well microtiter plate assay against Botrytis cinerea Pers., Septoria tritici Desm., and Phytophthora infestans (Mont.) De Bary, as described previously [9].…”

“…A variety of interesting secondary metabolites [2-6] were isolated from Sepedonium species which may be responsible for the observed biological phenomenon. One of the most prominent structural class within this genus is represented by the peptaibols due to their biological activity against molds [7][8][9][10] and striking mode of action [11].…”