| In this dissertation, we have investigated direct and efficient syntheses of biologically active natural products and natural product derivatives.;Chapter 1 reviews the classical methods of synthesizing xanthones, which include the Grover, Shah and Shah reaction, the synthesis via benzophenone intermediates, and the synthesis via diphenyl ether intermediates. New methods are also reported. Our approach to bioactive xanthones from Hypericum perforatum was via a benzophenone intermediate, which was the adduct from the photoacylation of benzoquinone with 1,6-dimethoxybenzaldehyde. This was the first example of the photoacylation using a hindered aldehyde. A regioselective Claisen rearrangement of 7-(allyloxy)-1-methoxy-9H-xanthen-9-one resulted in 1-allyl-2,8-dihydroxy-9H-xanthen-9-one, which is being investigated as a key intermediate in the total synthesis of psoroxanthin, a cytotoxic xanthone isolated from the Madagascar rain forest. Chapter 2 describes the synthesis of chroman aldehydes bearing an acetyl group plus alkoxy or hydroxy groups that inhibit HIV infectivity in HeLa37 cells.;Chapter 3 describes the selective metalation at the C-5 position of 4,6-dibromoresorcinol dimethyl ether with tetramethylpiperidide (LiTMP). |
