Acetone → (+)-Betulonic acid

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

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).

Herkunft & Nachweise