The Isolation and Structure Elucidation of Tasiamide B, a 4-Amino-3-hydroxy-5-phenylpentanoic Acid Containing Peptide from the Marine Cyanobacterium Symploca sp.

A new cytotoxic peptide, which displayed an IC₅₀ value of 0.8 μM against KB cells, has been isolated from the marine cyanobacterium Symploca sp. The planar structure of tasiamide B (1), deduced by 2D NMR experiments, contains the unusual amino acid-derived residue 4-amino-3-hydroxy-5-phenylpentanoic acid (Ahppa). The configuration of 1 was deduced by HPLC analysis of degradation products.