The structure and antimalarial activity of dispiro-1,2,4,5-tetraoxanes derived from (+)-dihydrocarvone.

An unsaturated dispiro 1,2,4,5-tetraoxane formed by peroxidation of (+)-dihydrocarvone was converted into four structurally diverse derivatives. X-ray crystallographic analysis shows that the structures possess central tetraoxane rings with spiro-2,5-disubstituted cyclohexylidene substituents and 6-membered rings in classical chair conformations. As polarity in the tetraoxane series increased, in vitro potency against Plasmodium falciparum decreased.