Flabelliferins A and B, Sesterterpenoids from the South Pacific Sponge Carteriospongia flabellifera

Two new sesterterpenoids named flabelliferins A (1) and B (2) were isolated from the lipophilic extract of the sponge Cateriospongia flabellifera, collected in the South Pacific near Vanuatu. The structure and absolute configuration of these two compounds were assigned by a combination of one- and two-dimensional NMR spectroscopy and by Mosher's ester analysis. Flabelliferin A (1) has a rare 25-homocheilanthane carbon skeleton, while flabelliferin B (2) is a 24-nor-25-homoscalarane sesterterpenoid.