CADINANES FROM ARTEMISIA-ANNUA THAT MAY BE INTERMEDIATES IN THE BIOSYNTHESIS OF ARTEMISININ

A novel secocadinane and a dihydroxycadinanolide have been isolated from the aerial parts of Artemisia annua, and their structures determined by H-1 and C-13 NMR spectroscopy. A biosynthetic mechanism is proposed by which arteannuin B (the most abundant cadinanolide from A. annua) is transformed into artemisinin (the antimalarial principal from A. annua) by way of this dihydroxycadinanolide and the enol tautomer of the 4,5-secocadinane. The proposed biosynthetic route shares many features with several recent chemical syntheses.