Pteratides I-IV, new cytotoxic cyclodepsipeptides from the Malaysian basidiomycete Pterula sp.

Formula chem. Four new cyclodepsipeptides, pteratides I-IV (1-4), have been isolated from the extract of a Pterula species collected from a Malaysian tropical forest. Homonuclear and heteronuclear 2D NMR techniques as well as MS fragmentation experiments, in combination with methanolysis, determined the gross structures of the peptides and showed that pteratides I and II each contained the nonproteinogenic amino acid 4-methylproline. The absolute configurations of the amino acids in pteratides I-IV were established using Marfey's method. Pteratides I and II are each potently cytotoxic against the P388 murine leukemia cell line (IC 50 values of 41 and 40 nM, respectively). Pteratides III and IV show weaker, but still notable, activity with IC 50 values of 7.4 and 2.9 μM, respectively.