Synthesis of new artemisinin analogues from artemisinic acid modified at C-3 and C-13 and their antimalarial activity.

Artemisinic acid (2) was modified through allylic oxidation at C-3 or conjugate addition at C-13 to afford 12 methyl artemisinate derivatives (4-15). Photooxidation of the derivatives yielded eight new artemisinin analogues, including 13-cyanoartemisinin (16), 13-methoxycarbonyl artemisinin (17), 13-methoxyartemisinin (18), 13-ethylsulfonylartemisinin (19), 13-nitromethylartemisinin (20), 13-(1-nitroethyl)artemisinin (21), (3R)-3-hydroxyartemisinin (22), and (3R)-3-acetoxyartemisinin (23). Among the analogues, only compound 20 had antimalarial activity comparable to artemisinin (1).