This project is designed to study the chemistry, stereochemistry, and antitumor activity of the novel antitumor epoxyfuranoxanthone, psorospermin, and other related compounds. Psorospermin shows significant activity over a wide dose range in P388 mouse leukemia, and is also active in a mammary (CD) and colon (C6) tumor system. Specific aims include 1) completion of the structural elucidation of psorospermin by establishment of the absolute configuration of the compound; 2) design and completion of the total synthesis of psorospermin as an alternate source of the compound for further anticancer testing; 3) synthesis and testing of a limited series of related xanthones and acridones in order to establish structure-active relationships in this series. A sufficient amount of psorospermin is urgently needed to complete antitumor testing and other biological studies persuant to consideration for further preclinical evaluation.