Usnic acid derivatives as potential antineoplastic agents

Abstract
Usnic acid, a lichen [Cladonia alpestris and Ramalina reticulata] antibiotic, showed low-level activity in the Lewis [mouse] lung carcinoma test system. In an effort to produce new agents of potential use in the treatment of lung cancer, derivatives of the natural product were synthesized and evaluated with a cytotoxicity assay. Structure-activity analysis of the cytotoxicity data indicated the importance of the lipophilicity and the .beta.-triketone moiety of usnic acid on cytotoxicity. No significant increases in survival of mice over controls were shown by any of the synthetic compounds in the [mouse] P388 leukemia or the Lewis lung carcinoma test systems.