Antineoplastic Agents 390. Isolation and Structure of Phakellistatin 12 from a Chuuk Archipelago Marine Sponge

A new cancer cell growth inhibitory (P388 lymphocytic leukemia ED50 2.8 μg/mL) cyclodecapeptide designated phakellistatin 12 (2) has been isolated as a trace (1.7×10−6% yield) constituent of the Western Pacific Ocean (Federated States of Micronesia-Chuuk) sponge Phakellia sp. Employing principally a combination of high resolution FAB with high field (500 MHz) 1H, 13C and 2-D NMR and chiral GC analyses the structure (all S chirality) cyclo-Ile-Phe-Thr-Leu-Pro-Pro-Tyr-Ile-Pro-Pro was assigned.