New Sesterterpenes from the Antarctic Sponge Suberites sp.

Chemical investigation of the Antarctic sponge <i>Suberites</i> sp. has previously led to the identification of new suberitane derivatives, some of which show bioactivity toward respiratory syncytial virus (RSV). Our ongoing NMR-guided investigation of new specimens of the sponge resulted in the isolation of five new analogs (<b>1</b>-<b>5</b>), previously reported suberitenones A-D (<b>6</b>-<b>9</b>), and oxaspirosuberitenone (<b>10</b>). Suberitenone K (<b>1</b>) was characterized as the 8-keto derivative of <b>6</b>, while three new phenols, suberitandiol (<b>2</b>), abeosuberitandiol (<b>3</b>), and furanosuberitandiol (<b>4</b>), and the degraded sesterterpene norsuberitenone B (<b>5</b>) were also found. Compound <b>3</b> displays a ring contraction while <b>4</b> has a new dihydrofuran ring. Structural characterization was achieved by a combination of NMR, HR-MS, and X-ray diffraction (XRD). Moderate activity towards RSV was reported for <b>9</b> and the new metabolite <b>1</b>, with IC₅₀ values of 15.0 μM and 39.8 μM, respectively.