合成路线1

The (+)-isolimonene (I) was submitted to a regioselective hydroboration with dicyclohexylborane to give the alcohol (II), which was oxidized with CrO3 to the corresponding carboxylic acid (III). The iodolactonization of (III) by means of KI, I2 and NaHCO3 yielded a separable, diastereomeric mixture of iodolactones (IV) + (V). The suitable isomer (IV) was condensed with methyl vinyl ketone (VI) by means of tris(trimethylsilyl)silane and AIBN in refluxing toluene to afford the alkylated lactone (VII) as an inseparable diastereomeric mixture. The ketonic group of (VII) was treated with ethanedithiol (VIII) and BF3/Et2O in dichloromethane to provide a separable mixture of thioketal lactones (IX)+(X). The suitable isomer (X) was hydrolyzed with NaOH in refluxing methanol to give the hydroxyacid (XI), which was treated with diazomethane to yield the corresponding methyl ester (XII). The oxidation of the OH group of (XII) by means of PCC affords the ketoester (XIII), which is submitted to a Wittig condensation with methoxymethyltriphenylphosphonium chloride (XIV) by means of KHMDS in THF/HMPA to provide the methoxymethylene derivative (XV). The cleavage of the dithioketal group of (XV) by means of HgCl2 and CaCO3 in acetonitrile regenerates the keto group giving compound (XVI), which is finally transformed into the target (+)-artemisinin by photooxidation with O2 in methanol in the presence of Rose Bengal, followed by a treatment with 70 % HClO4.

合成路线2