ANTINEOPLASTIC AGENTS .315. ISOLATION AND STRUCTURE OF THE MARINE SPONGE CANCER CELL-GROWTH INHIBITOR PHAKELLISTATIN-5

The Federated State of Micronesia (Chuuk) marine sponge Phakellia cost ada has been found to contain (9.6 x 10(-6) % yield) a new human cance r cell growth inhibitor designated phakellistatin 5 (3). Structural el ucidation was accomplished employing high resolution FAB tandem MS/MS and high field (500 MHz) 2D-NMR techniques. Extension of the NMR exper iments over the temperature range -25 to 25 degrees C allowed the prin cipal solution conformation of phakellistatin 5 to be assigned (Figure 2). The absolute configuration was found to correspond to S-amino aci d units except for R-Asn.