Callipeltins B and C; bioactive peptides from a marine Lithistida sponge Callipelta sp

Following the characterization of callipeltin A (I) two new cytotoxic peptides, callipeltin A (II) and C (III), were isolated from the New Caledonian sponge Callipelta sp. Callipeltin B possess the same cyclic depsipeptidal structure as in callipeltin A and differs from I by having the N-terminal 2,3-dimethylpyroglutamic acid unit instead of the tripeptide chain with the N-terminus blocked by an hydroxyacid. Callipeltin C is simply the acyclic callipeltin A. The structures II-III have been detd. by NMR expts., FAB mass spectrometry, evaluation of the amino acids obtained by acid hydrolysis and by comparison of the data with those of callipeltin A