EPR EVIDENCE FOR THE INVOLVEMENT OF FREE-RADICALS IN THE IRON-CATALYZED DECOMPOSITION OF QINGHAOSU (ARTEMISININ) AND SOME DERIVATIVES - ANTIMALARIAL ACTION OF SOME POLYCYCLIC ENDOPEROXIDES

EPR experiments confirm that reaction of qinghaosu and some related en doperoxides with Fe2+ in aqueous acetonitrile leads to the production of carbon-centred radicals derived by rapid rearrangement of first-for med cyclic alkoxyl radicals. Signals obtained from qinghaosu itself wi th spin-traps DMPO and DBNBS are assigned to the adducts (15) and (16) , a finding which accounts for the formation of the major products (11 ) and (14).