Preparation Of Ginsenosides 25-OH-Rg2 Group

In this paper,the Re,and an unknown saponin were transformed into 20（S,R）-Rg2and20（S,R）-25-OH-Rg2 by using FeCl₃ as catalyst under the organic alcohol system.Using ginsenoside Re as substrate FeCl₃ as catalyst,the organic alcohol system,alcohol concentration and Fe³⁺concentration,reaction temperature,reaction time and substrate concentration were optimized respectively.The optimum conditions for Fe³⁺to catalyze re saponins in glycerol system are as follows:concentration of propanol 50%（V/V）,iron ion concentration 0.35 mol/L,substrate reaction concentration 1.2%,reaction time 26 h at50℃,ethanol concentration 20%（V/V）,reaction concentration of iron ion 0.8 mol/L,reaction of substrate The concentration was 0.7%and the reaction time was 17 h at 50℃.Under the optimum reaction conditions,the yields of 20 g Re at 50%（V/V）propanol and 20%（V/V）were 65%（W/W）and 63（W/W）,respectively.The 13 g product was desacked by AB-8 macroporous resin,and the product was 10.52 g,and the yield was 75%（W/W）The5 g desugar product was separated by silica gel column chromatography,and a pure 2 g mixture of 20（S,R）-25-OH-Rg2 was obtained in 40%（W/W）yield.