New Cytotoxic Sesterterpenoids and Norsesterterpenoids from Two Sponges of the Genus Sarcotragus

New norsesterterpenoids (<BO>3</BO> and<BO> 4</BO>), a sesterterpenoid (<BO>6</BO>), pyrroloterpenoids (<BO>7</BO>−<BO>10</BO>), and a stereoisomer of kurospongin (<BO>5</BO>) were isolated, along with known furanosesterterpenes (<BO>11</BO>−<BO>15</BO>), from two marine sponges of the genus Sarcotragus. The gross structures were established on the basis of NMR and MS analysis. The stereochemistry was defined by combined use of NMR and CD spectroscopy. The compounds were evaluated for cytotoxicity against five human tumor cell lines and were found to exhibit marginal to moderate activity.