Euryjanicin A: a new cycloheptapeptide from the Caribbean marine sponge Prosuberites laughlini

The isolation and structure determination of an unusual cyclic heptapeptide, euryjanicin A, from a Puerto Rican marine sponge, Prosuberites laughlini, is reported. The peptide exists in multiple, slowly exchanging conformations in CDCl3 and contains 1 mol each of valine, phenylalanine, tryptophan, serine, and isoleucine, as well as 2 mol of proline residues.