ANTINEOPLASTIC AGENTS .323. ISOLATION AND STRUCTURE OF PHAKELLISTATIN6 FROM A CHUUK ARCHIPELAGO MARINE SPONGE

Phakellistatin 6 (7), a trace (7.5 x 10(-7)% yield) constituent of the marine sponge Phakellia costata located in the Federated States of Mi cronesia has been found to significantly inhibit growth of certain hum an cancer cell lines (GI(50) 0.1 to 0.01 mu g/ml). The structure of ph akellistatin 6 (7) was deduced as cycle (Pro-Trp-Leu-Pro-Ile-Pro-Phe) employing a combination of MS/MS and high field (500 MHz) 2D-NMR proce dures followed by chiral (all S amino acids) assignments using hydroly sis --> derivatisation --> chiral chromatographic techniques.