Synthesis of novel trypanosome alternative oxidase inhibitors for the treatment of African trypanosomiasis

African trypanosomiasis is a protozoan infection affecting tens of thousands of people and millions of livestock animals across sub-Saharan Africa. In humans the disease is fatal without chemotherapeutic intervention and in animals it causes a severe anaemia that greatly impairs productivity. Available drug compounds are difficult to administer and unacceptably toxic. A natural product, ascofuranone, inhibits a key trypanosome specific respiratory enzyme, trypanosome alternative oxidase, and was shown over a decade ago to be trypanocidal using both in vitro and in vivo experiments. The compound suffers from rapid metabolism and contains several functionalities undesirable in a drug compound. Despite the promising activity the lack of applicable synthetic methods available hampered the development of chemotherapeutics from ascofuranone. In this work, novel synthetic routes were completed to explore the lead compound. New synthetic methods were successfully developed using palladium catalysed Suzuki couplings and Lewis acid catalysed rearrangements. Ortho-lithiation approaches also afforded potent novel inhibitors. Of particular note is a benzisoxazole, which is expected to alleviate many of the metabolic issues associated with ascofuranone. Alternate heterocycle analogues were explored and an interesting indazole analogue obtained. Finally, chemical methods were developed towards the benzisoxazole and indazole motifs with carboxylic acids, amenable to diversification by amide coupling. A preliminary range of novel amide containing 5, 6-heterocycles were synthesized to begin SAR exploration of these structures.