Antimalarial activity of novel 1,2,5,6-tetraoxacycloalkanes and 1,2,5-trioxacycloalkanes

Photooxygenation of 2-phenylnorbornene 1 in the presence of 30% aqueous hydrogen peroxide afforded 1,2-bishydroperoxide 3, which could be cycloalkylated on treatment with silver oxide and a 1,ω-diiodoalkane to provide the tricyclic peroxides 12. Trimethylsilylation of 3 followed by TMSOTf-catalyzed cyclocondensation with carbonyl compounds led to the formation of the tricyclic peroxides 14 containing a 1,2,4,5-tetroxepane structure. Photooxygenation of 1 in the presence of either unsaturated hydroperoxides or unsaturated alcohols followed by bis(collidine)-iodine hexafluorophosphate promoted cyclization gave the corresponding cyclic peroxides 15-17. Several of these cyclic peroxides showed substantial antimalarial activity particularly in vitro.