Isolation, structure determination, and synthesis of galaxamide, a rare cytotoxic cyclic pentapeptide from a marine algae Galaxaura filamentosa.

Galaxamide (1), a rare cyclic pentapeptide, was isolated from the marine algae Galaxaura filamentosa. A preliminary bioassay of Galaxamide showed remarkable in vitro antiproliferative activities against GRC-1 and HepG2 cell lines. The first total synthesis of the cyclic peptide was achieved for further biological evaluation.