Cepafungin III

New acylpeptide antibiotics named cepafungins I, II and III were isolated from the culture broth of a strain identified as Pseudomonas sp. These antibiotics are neutral substances, soluble in aqueous alcohols and dimethyl sulfoxide, and show UV maxima at 260.5 nm. The IR spectra indicated these to be peptides. Molecular formulas C28H46N4O6, C27H44N4O6 and C26H42N4O6 for cepafungins I, II and III were indicated by elemental analysis and SI-MS. Cepafungins exhibited inhibitory activity against yeast and fungi, and antitumor activity against P388 leukemia in mice.

Structures of interesting acylpeptide antibiotics cepafungins I, II and III were elucidated by NMR spectroscopic studies and some degradation experiments. The antibiotics contain a common peptide part that consists of threonine and two unusual amino acid residues, gamma-hydroxylysine and 4-amino-2-pentenoic acid. The unusual amino acid residues compose an interesting 12-membered ring with an exocyclic N-terminus to which the threonine is connected. Different fatty acyl groups connected to the N-terminus of the threonine distinguish the three cepafungins. The major component I and minor component III are new substance, but the minor component II has a structure identical with that of the recently reported antibiotic glidobactin A.