Design and synthesis of orally active dispiro 1,2,4,5-tetraoxanes; Synthetic antimalarials with superior activity to artemisinin

The design and synthesis of dispiro- and spirotetraoxanes through acid-catalyzed cyclocondensation of bis(hydroperoxides) with ketones were investigated. Various modular synthetic methods were used to enable many different analogues to be prepared from common achiral synthetic intermediates and some of the key reactions employed include reductive amination and mixed anhydride amide coupling reactions. The synthesis of 1,2,4,5-tetraoxanes was also dependent on several factors, including the structure of the ketone or aldehyde, temperature, solvent, pH, and the equilibria between the ketone and the precursors of cyclic peroxides. The required 1,2,4,5-tetraoxane was formed by crosscondensation of the bis(hydroperoxide) and the 1,4-cyclohexanedione was obtained in low temperature. Reductive amination of the ketone with various amino compounds also produced compounds in moderate to good quantities.