New insecticidal cyclodepsipeptides from the fungus Isaria felina. II. Structure elucidation of isariins B, C and D.
Isariins B, C and D, isolated from a strain of Isaria felina, were shown to be cyclodepsipeptides constituted by a pentapeptide cyclized through a beta-hydroxyacid. The nature of the latter and the sequence of the peptide were determined for each compound. Relations between insecticidal activity and structure of the depsipeptides were pointed out.