Study On The Synthetic Process Of Chrysophanic Acid And Rhein

As an active ingredient of many traditional Chinese drugs, such as rhubarb, fleeceflower root and giant knotweed rhizome, Chrysophanic acid and rhein have a lot of pharmacological action, which belong to 1,8-dihydroxyanthraquinone derivatives of mono-anthraquinone compounds.There are a great deal of chrysophanic acid and rhein in vegetable kingdom, but there are some reasons cause that the cost of them is very high, which include low content and low extraction, the total count of anthraquinone is only 3%～5% in rhubarb. At present, chrysophanic acid and rhein is prepared by biological extraction from Chinese drugs. Therefore, it has some practical significance that chrysophanic acid and rhein are totally synthesized by chemical method.Chrysophanic acid in total yield of 40.4% was synthesized from 3-nitrophthalic acid by dehydration, friedel-crafts acylation, reduction, diazotization, hydrolysis and cyclization. Rhein in total yield of 22.3% was synthesized from chrysophanic acid by acylation, oxidation and deacetylation. The structures of them were characterized by ~1H-NMR.We took some improvements and innovations on its technics in the synthetic process of chrysophanic acid. First of all, in the friedel-crafts acylation reaction, we have changed the purification of the product from dissolving it in alkali and separating it out from acid to crystallizing it from nonpolar solvent. The yield and purity of product have been improved. The second, in the reduction reaction, the introduction of anhydrous ammonium formic acid resulted in mild reaction condition,short reaction time,simple after-treatment and high yield. The last, in the the cyclization reaction, the purification of chrysophanic acid was changed to extract -ion in the nonpolar solvent, which got rid of the column chromatography, the purity is very high.We also took some improvements on its technics in the synthetic process of rhein. First, in the oxidation reaction, diacetyl chrysophanic acid which wasn't purified was directly oxidated, which got rid of the column chromatography and decreased the cost largely. Second, in the deacetylation reaction, raw material which wasn't purified was directly deacetylated, which wasn't influenced the purity.