Abstract
Chemical analysis of the Indonesian sponge Plakortis cfr. lita afforded two new analogues of the potent trypanocidal agent manadoperoxide B (1), namely 12-isomanadoperoxide B (2) and manadoperoxidic acid B (3). These compounds were isolated along with a new short chain dicarboxylate monoester (4), bearing some interesting relationships with the polyketide endoperoxides found in this sponge. Some semi-synthetic analogues of manadoperoxide B (6-8) were prepared and evaluated for antitrypanosomal activity and cytotoxicity. These studies revealed crucial structure-activity relationships that should be taken into account in the design of optimized and simplified endoperoxyketal trypanocidal agents.