Ichthyotoxic sesterterpenoids from the New Guinean sponge Carteriospongia foliascens

Article abstract of DOI:10.1016/S0040-4020(01)82355-3

Six 20,24-dimethylscalarane derivatives (5, 12, 15, 17, 19, and 21) have been isolated from the New Guinean sponge Carteriospongia foliascens. Compound 12 is identical with a C₂₇ tetracyclic terpene previously isolated from an Australian specimen of the same sponge. The five other derivatives are new and their structures have been established on the basis of their spectral data. The structure of 5 was confirmed by single-crystal X-ray diffraction and that of 15 by chemical correlation with 12. The configuration at C-4 for all these compounds has been determined through ¹³C NMR data. Evidence leading to reverse the configuration at this centre in previously reported C₂₇ tetracyclic terpenes is discussed. An ecological function is suggested for these molecules.