During the present report period, substantial efforts have been directed toward both anti-HIV and antitumor leads. Projects pursued during the current report period include: bulk isolation of the HIV-1 specific reverse transcriptase inhibitor costatolide from the latex of Calophyllum teysmannii var. inophylloide and the synthesis and SAR studies of structurally modified costatolide derivatives; a chemotaxonomic analysis of the pyranocoumarins present in the extracts from Calophyllum in the NCI Repository; the structure elucidation and enzymatic transformation of macrolides from a novel Australian sponge; structure elucidation of metabolites from Stelleta sp.; and the structure elucidation of novel macrocycles from Aplidium lobatum.