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0 °C

To a solution of betulin 1 (1 g, 2.26 mmol) in acetone (50 ml), cooled at 0° C., freshly prepared Jone's reagent was added dropwise. The resulting mixture was stirred for about 1.5 h at 0° C., quenched with methanol (25 ml), stirred for an additional 5 minutes, then water (40 ml) was added. The acetone was removed under vacuum and the aqueous residue was extracted with ethyl acetate (2×40 ml) and washed with water (30 ml) and brine (30 ml). Dried with Na2SO4, filtered, and concentrated under reduced pressure. The residue solid was submitted to FCC with petroleum ether 40-60° C./ethyl acetate (4:1) and afforded compound 11 (685 mg, 67%): IR (film) υmax 3070, 1703, 1686, 1642 cm−1; 1H NMR (CDCl3, 300 MHz) δ 4.77 (brs, 1H, H-29a), 4.64 (brs, 1H, H-29b), 3.04 (dt, J=10.7 Hz, J=4.3 Hz, 1H, H-19), 1.72 (s, 3H, H-30), 1.09 (s, 3H), 1.04 (s, 3H), 1.02 (s, 3H), 0.99 (s, 3H), 0.95 (s, 3H). 13C NMR (CDCl3, 75 MHz) δ 218.2 (C3), 182.2 (C28), 150.3 (C20), 109.7 (C29). EI-MS m/z (% rel. intensity): 454 (19) M+, 408 (24), 393 (20), 248 (85), 189 (100), 175 (62), 133 (55), 119 (76), 105 (69), 79 (52).

1. additionfreshly prepared Jone's reagent was added dropwise
2. customquenched with methanol (25 ml)
3. stirringstirred for an additional 5 minutes
4. additionwater (40 ml) was added
5. customThe acetone was removed under vacuum
6. extractionthe aqueous residue was extracted with ethyl acetate (2×40 ml)
7. washwashed with water (30 ml) and brine (30 ml)
8. dry with materialDried with Na2SO4
9. filtrationfiltered
10. concentrationconcentrated under reduced pressure
11. customwas submitted to FCC with petroleum ether 40-60° C./ethyl acetate (4:1)