Stylissamides A–D – New Proline‐Containing Cyclic Heptapeptides from the Marine Sponge Stylissa caribica

Four new cyclic heptapeptides, stylissamides A–D ( 1 – 4 ), were isolated from the Caribbean sponge Stylissa caribica . The structures of these metabolites were elucidated by NMR and MS/MS methods. The peptides contain three and, in one case, four proline residues. The sequence assignment of 1 – 4 by NMR was supported by fragmentations in HR‐MS/MS measurements. The absolute configuration of all amino acid residues was assigned as L using Marfey's method and the OPA method.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)