Structures of cepafungins I, II and III.

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.