反应详情

In 100-ml flask stir 2 g of Betulin in 50 ml of CH2Cl2 at 0° C. Add 5 ml of 99% CF3COOH and stir for 30 minutes. Pour, reaction mixture in 100 ml of cracked ice and separate the organic part. Extract with CH2Cl2 (3×10 ml) and wash combined organic extracts with conc. NaHCO3 (2×20 ml) and water (2×20 ml), and dry the extract over Na2SO4 (anh.). Evaporation of solvent gives 1.98 g of Allobetulin, which was recrystallized from hexane-dichloromethane to yield white needles mp. 268-269° C. [lit. 265-268], IR (KBr) 3448.5, 2941.5, 2866.6, 1780.7, 1456.6, 1384.4, 1168.9, 1035.0, cm−1; 1H NMR (CDCl3) d 3.75 (D, J=10.3 Hz, 1H, 28-H), 3.51 (S, 1-H, 19-H), 3.41 (D, J=10.3 Hz, 1H, 28-H), 3.18 (DD, 1H, 3-H), 0.74, 0.76, 0.81, 0.88, 0.89, 0.94, 0.94 (all S, 7×3H, 27-, 23-, 24-, 25-, 26-, 29-, 30-Me), 1.01-1.74 (complex CH—, CH2, 25 H,); 13C NMR (CDCl3) d 88.41, 79.38, 71.49, 55.77, 51.35, 47.07, 41.78, 40.99, 40.88, 40.87, 39.16, 37.52, 36.95, 36.51, 34.40, 34.18, 32.96, 29.08, 28.27, 27.57, 26.72, 26.72, 26.50, 24.82, 21.26, 18.54, 16.79, 15.96, 15.72, 13.82; MS (EI) 442, 424, 411, 371, 355, 303, 273, 257, 245, 231, 220, 207, 203, 189, 177, 162, 149, 135, 121, 107.

1. additionPour
2. customseparate the organic part
3. extractionExtract with CH2Cl2 (3×10 ml)
4. washwash
5. customdry the
6. extractionextract over Na2SO4 (anh.)
7. customEvaporation of solvent