Dihydroartemisin

Artemisinic acid can indeed be easily converted to artimisinin using conventional chemistry in three steps via reduction of the exocyclic methylene group and photooxidation of the resulting dihydroartemisinic acid, with 30% overall yield (see Scheme 9) Other artemisinin derivatives have also been prepared using artemisinic acid as the starting material. ... 

Dihydroartemisinic acid 292 undergoes slow spontaneous autooxidaton to artemisinin 9a and other products reported from A. annua. The mechanism of this complex process has been investigated in detail <2002T897, 2004T1125> and the role of the 12-carboxylic acid group elucidated <2002T909>. 

From the view of chemistry, the C-12 position of dihydroartemisin is similar to the C-1 position of carbohydrates. So, these C-12 derivatives may be divided into three types 0-glycosides, A-glycosides, and C-glycosides using a similar term in carbohydrate chemistry. 

Wallaart, T. E. Pras, N. Quax, W. J. Isolation and identification of dihydroartemisinic acid hydroperoxide from Artemisia annua—a novel biosynthetic precursor of artemisinin. J. Nat. Prod., 1999, 62(8) 1160-1162. 

Scheme 6.268 shows the synthesis of the antimalarial drug artemisinin (564) from dihydroartemisinic acid (565) photooxygenation of 565 in the presence of Methylene Blue gives 566, which is oxidized by ground-state oxygen in 30% chemical yield.1462... 

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