GENERAL STEPS: Astragaloside IV (1) (5.00 g, mmol) was dissolved in 10% HCl-MeOH solution (TCI America) (500 mL) and the reaction was stirred at room temperature for 7 days. Upon completion of the reaction, the reaction mixture was concentrated under reduced pressure at 20 °C to half of the original volume (avoid heating). The concentrate was extracted by partitioning with aqueous sodium bicarbonate and ethyl acetate. The aqueous phase was extracted once more with ethyl acetate. The organic phases were combined, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by column chromatography (chloroform/methanol, 20:1 to 14:1 gradient elution). To displace the residual solvent, the purified product was dissolved in ethanol and the solvent was removed under reduced pressure to afford the target compound 2 (2.1 g, 64% yield).1H NMR (CDCl3) δ (ppm): 0.34 (d, J = 4.7 Hz, 1H), 0.48 (d, J = 4.3 Hz, 1H), 0.92 (s, 3H), 0.93 (s, 3H). 1.0-1.8 (m, 13H), 1.11 (s, 3H), 1.19 (s, 3H), 1.22 (s, 6H), 1.27 (s, 3H), 1.9-2.0 (m, 4H), 2.30 (d, J = 7.8 Hz, 1H), 2.54 (q, J = 11.8 Hz, 1H), 3.27 (m, 1H), 3.50 (m, 1H), 3.72 (t, J = 7.4 Hz, 1H), 4.65 (q, J = 7.4 Hz, 1H).ESI-MS m/z: Positive 491 (M + H)+, Negative 549 (M + AcO)-.TLC (Merck, Kieselgel 60) Rf = 0.33 (Chloroform/methanol, 6:1).
