THE LOBATAMIDES, NOVEL CYTOTOXIC MACROLIDES FROM SOUTHWESTERN PACIFICTUNICATES

Novel macrolides, lobatamides A-F (1-6), have been isolated from shall ow water Australian collections of Aplidium lobatum, from a deep water collection of Aplidium sp., and from an unidentified Philippine ascid ian. Full details of the isolation and structure elucidation of 1-6 ar e provided herein, along with results and analyses of the testing of l obatamides A-D (1-4) in the NCI human tumor 60 cell-line screen. The l obatamides share a common core structure with the recently described s alicylihalamides, which were isolated from a Haliclona sp. sponge. COM PARE analyses of the mean-graph differential cytotoxicity profiles of the lobatamides and the salicylihalamides showed high correlations wit h each other but not with members of the NCI's standard agents databas e. These compounds, therefore, appear to comprise a new mechanistic cl ass, meriting further antitumor investigations.