This project involves the bioassay-guided fractionation and structure elucidation of the active constituents from extracts selected on the basis of their anti-HIV or antitumor activity in the primary screens. The HIV-inhibitory extracts under investigation currently include: extracts from tropical trees of the genus Calophyllum, which produce dipyranocoumarins such as calanolide A; and, extracts from the marine sponge Theonella sp. The current antitumor lead studies include: the isolation and characterization of a new series of macrolides, the lobatamides, from the tunicate Aplidium lobatum; and, new, acylated tedanolide derivatives from an Australian sponge.