Diazomethane → Artemisinic alcohol

Participants

Reaction Conditions

Reaction Steps

Amorpha-4,11-diene-12-ol was prepared from 100 mg artemisinic acid. The acid was dissolved in 6 mL of dry ether and esterified by adding diazomethane and mixing for 1 hour. GC-MS analyses of the reaction mixture showed the methyl ester and another compound (3:1), probably the methyl ester that was not connected to a cyclopropyl group. After removal of ether, 8.6 mg of the mixture was dissolved in 20 mL of ether-TBF (1:1) and cooled at −60° C. under a flow of dry nitrogen for 2 hours. The mixture was subsequently stirred for 1 hour at −30° C. with an excess of LiAlH4, after which the reaction was stopped by the addition of Na2SO4.10H2O. The temperature was raised to room temperature, and the reaction mixture was stirred an additional half hour. After drying with MgSO4 overnight, the mixture was filtered through a Büichner funnel and the solvent removed. The desired alcohol was isolated and purified by preparative thin layer chromatography performed on silica gel plates, using a mixture of petroleum ether-ethyl acetate (3:1) as an eluent (Rf 0.7). Amorpha-4,11-diene-12-ol was obtained in an overall yield of 14% as a mixture with 4-amorphene-12-ol (9:1). 1H NMR (400 MHz, CDCl3): δ 0.87 (d, 3H, Me15, J=6.0 Hz), δ 1.50 (br s, 3H, Me14), δ 1.0–2.2 (m, 11H), δ 2.47 (m, 1H, H6), δ 4.10 (s, 2H, H12), δ 4.83 (br s, 1H, H13′), δ 5.04 (br s, 1H, H13), δ 5.18 (br s, 1H, H4). EIMS (70 eV) m/z: 220 [M]+ (6), 202 (35), 189 (66), 187 (34), 145 (40), 132 (52), 131 (36), 121 (100), 119 (81), 105 (51), 93 (74), 91 (70), 81 (47), 79 (77), 77 (50), 55 (41), 41 (47).

Provenance & Evidence