Isolation of callipeltins A–C and of two new open-chain derivatives of callipeltin A from the marine sponge Latrunculia sp. A revision of the stereostructure of callipeltins

Two new callipeltin-related acyclic peptides (2 and 3) have been isolated, together with callipeltins A–C from the marine sponge Latrunculia sp. collected at the Vanuatu Islands. The gross structures of new compounds were elucidated by spectroscopic data. The application of the Marfeyʹs analysis on the new derivatives and on callipeltin A (1), allowed us to revise the configuration of two amino acid units in callipeltin A.