Stylissamides E and F, Cyclic Heptapeptides from the Caribbean Sponge <i>Stylissa caribica</i>

2010-04-23T00:00:00Z (GMT) by Christine Cychon Matthias Köck
In addition to the four known stylissamides, A (<b>1</b>), B (<b>2</b>), C, and D, two new cyclic heptapeptides, stylissamides E (<b>3</b>) and F (<b>4</b>), were isolated from the Caribbean sponge <i>Stylissa caribica</i>. The structures of <b>3</b> and <b>4</b> were elucidated from a combination of mass spectrometric and NMR spectroscopic data as cyclo-(<i>cis</i>-Pro<sup>1</sup>-Tyr<sup>2</sup>-<i>trans</i>-Pro<sup>3</sup>-Ala<sup>4</sup>-Ile<sup>5</sup>-Gln<sup>6</sup>-Ile<sup>7</sup>) for stylissamide E (<b>3</b>) and cyclo-(<i>trans</i>-Pro<sup>1</sup>-<i>cis-</i>Pro<sup>2</sup>-Phe<sup>3</sup>-Asp<sup>4</sup>-<i>trans</i>-Pro<sup>5</sup>-Arg<sup>6</sup>-Phe<sup>7</sup>) for stylissamide F (<b>4</b>).