Three furan-containing scalarane sesterterpenoids (1⁻3) and a novel pyrrole-containing analog (4) were isolated from the sponge Scalarispongia species. Compound 3, reported in the literature as a synthetic derivative of furoscalarol 2, was for the first time isolated from a natural source. During the separation performed using a silica column in the presence of methanol, 16-methoxy derivatives (5, 6) were obtained from the unintended reaction of 2. The isolated natural products 3 and 4 and the artifact 5 showed moderate to high cytotoxicity against six human cancer cell lines, whereas compound 6, the C-16 epimer of 5, showed no cytotoxicity at a concentration of 60 μΜ.
Keywords: Scalarispongia; conjugate addition; cytotoxicity; furan; pyrrole; sesterterpenoid.