THE KAPAKAHINES, CYCLIC-PEPTIDES FROM THE MARINE SPONGE CRIBROCHALINA-OLEMDA

Four cyclic peptides, kapakahines A-D, were isolated from the marine s ponge Cribrochalina olemda. Their structures including complete stereo chemistry were elucidated by spectral analysis and chemical degradatio n. The unique structural feature of these peptides is the lack of an a mide linkage between two tryptophan residues. Instead the ring is clos ed by a bond from the indole nitrogen of Trp-1 to the beta-carbon of T rp-2.