| Abstract
| - The sponge Cacospongia scalaris from Tarifa Island,Spain, contains in addition to five knowncompounds (1−5), the new scalaranesestertepenes 18-epi-scalaradial (6),19-dihydroscalaradial(7), 12-epi-acetylscalarolide (8), and16-acetylfuroscalarol (9) together with threeuncommonnorscalaranes norscalaral A (10), norscalaral B(11), and norscalaral C (12). The structureswereelucidated by interpretation of spectral data.18-epi-Scalaradial (6) represents themissingstereoisomer on structure−activity studies carried out with compoundsof this series and did notreact with methylamine. The new compounds isolated from C.scalaris showed significant in vitrocytotoxicity against five tumor cell lines with18-epi-scalaradial showing the greatest activity(ED50= 0.2 μg/mL).
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