Chrysosporide, a Cyclic Pentapeptide from a New Zealand Sample of the Fungus Sepedonium chrysospermum

A new cyclic pentapeptide, chrysosporide (1), was isolated from a New Zealand sample of the mycoparasitic fungus Sepedonium chrysospermum by bioactivity-guided fractionation. The planar structure was deduced by detailed spectroscopic analysis, and the absolute configurations of the amino acid residues were defined by Marfey's method. As both enantiomers of Leu occurred in chrysosporide, molecular mechanics calculations were applied to the analysis to distinguish between the possible structural isomers. Only the lowest energy conformers of the cyclo-(l -Val-d-Ala-l-Leu-l-Leu-d-Leu) isomer were in agreement with the observed NOEs, suggesting that this was the most probable amino acid sequence for chrysosporide (1).