Methanol → Qing Hau Sau

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

To a solution of the crude dihydroartemisinin in chloroform (40 mL) and methanol (1 mL, 24.8 mmol) was added boron trifluoride etherate (0.16 mL, 1.24 mmol) at 0° C. The reaction was stirred at 0° C. for 15 minutes, slowly warmed up to room temperature and stirred at room temperature for 3 hours. The reaction was monitored by TLC until all starting material was consumed. The reaction mixture was quenched with water (50 mL) and diluted with chloroform (25 mL). The two phases were separated, and the aqueous layer was extracted with chloroform (30×2 mL). The combined organic layers were washed with brine, dried over magnesium sulfate, filtered and concentrated under reduced pressure to afford crude product which was further purified by column chromatography on Florisil (1%-10% EtOAc/hexanes) to give two artemisinin isomers as white solids: β-isomer (0.29 g, 0.98 mmol, 79%) mp 73°-74.5° C.; α-isomer (0.05 g, 0.17 mmol, 14%), with each having a 1H NMR spectrum identical to that reported in the literature. ##STR33##

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