Isolation and Structural Elucidation of Euryjanicins B−D, Proline-Containing Cycloheptapeptides from the Caribbean Marine Sponge Prosuberites laughlini

Three new cyclic peptides, euryjanicins B (2), C (3), and D (4), have been isolated from the Puerto Rican marine sponge Prosuberites laughlini, and the structures were elucidated by chemical degradation, ESIMS/MS, and extensive 2D NMR methods. When tested against the National Cancer Institute 60 tumor cell line panel, all of the purified isolates displayed weak cytotoxicity.