Table 1.

In situ transformation of dihydroartemisinic acid (4) or its ester 19 into artemisinin (1).

No.	Substrate	Condition of Peroxidation Step	Condition of Rearrangement/Cyclization Step	Yield of 1, %	Reference
1	4	O2/hv, Methylene Blue, acetone, 0 °C, 30 min	TFA (cat.), petroleum ether, air, r.t., 4 days	30	[59]
2	crude mixture of 19 and isomer with double bond C6-C7 position	O2/hv, Methylene Blue, CH2Cl2, 20 °C, 90 min	TFA (cat.), petroleum ether, air, 20 °C, 4 days	30	[64]
3	crude mixture of 4 and isomer with double bond C6-C7 position	O2/hv, Methylene Blue, acetone, 0 °C, 30 min	TFA (cat.), petroleum ether, air, 20 °C, 24 h	26	[65]
4	19	O2/hv, Rose bengal, CH3CN, −30 °C, 6 h	(1) O2, Cu(OTf)2, CH3CN, −20 °C;	25	[66]
			(2) p-TsOH (cat.), CH2Cl2, 20 °C, 4 h