Method of preparing diacetyl rhein
AssigneeMadaus AG
InventorsAlfons Carcasona, Wolf Grimminger, Pentti Hietala, Helga Zaeske, Klaus Witthohn
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Abstract
Diacetylrhein which is substantially free of aloe-emodin components, is prepared by a process wherein a) rhein-9-anthrone-8-glusoside containing aloe-emodin components is subjected to a liquid-liquid partitioning of the compounds obtained is carried out between a polar organic solvent which is only partly miscible with water and an aqueous phase, b) the rhein-9-anthrone-8-glucoside contained after the partitioning in the aqueous phase is oxidized to rhein-8-glucoside, c) the glucose residue in the 8-position of the rhein-8-glucoside is split off in an acidic medium and, d) the rhein obtained is acetylated and the diacetylrhein recovered.
Claims13
The method of preparing diacetylrhein which is substantially free of aloe-emodin components, which comprises:
- a) admixing a mixture of rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside with an aqueous solution having a pH of 6.5 to 7.5 and with a polar organic solvent which is incompletely miscible with water,
- b) subjecting the resulting mixture to liquid-liquid partitioning to form a light organic phase containing said aloe-emodin-9-anthrone-8-glucoside and a heavy aqueous phase containing said rhein-9-anthrone-8-glucoside,
- c) separating said aqueous phase from said organic phase,
- d) oxidizing the rhein-9-anthrone-8-glucoside contained in said aqueous phase to rhein-8-glucoside,
- e) treating said rhein-8-glucoside with an acid to remove the glucose in the 8-position and form substantially pure rhein,
- f) acetylating said rhein to form substantially pure diacetylrhein, and
- g) recovering said diacetylrhein.
The method of preparing diacetylrhein which is substantially free of aloe-emodin components, which comprises
- a) reducing a sennoside mixture to form a mixture of rhein-9-anthrone-8-glucoside and aloe-emodin-anthrone-8-glucoside,
- b) admixing said mixture of rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside with an aqueous solution having a pH of 6.5 to 7.5 and with a polar organic solvent which is incompletely miscible with water,
- c) subjecting the resulting mixture to liquid-liquid partitioning to form a light organic phase containing said aloe-emodin-9-anthrone-8-glucoside and a heavy aqueous phase containing said rhein-9-anthrone-8-glucoside,
- d) separating said aqueous phase from said organic phase,
- e) oxidizing the rhein-9-anthrone-8-glucoside contained in said aqueous phase to rhein-8-glucoside,
- f) treating said rhein-8-glucoside with an acid to remove the glucose in the 8-position and form substantially pure rhein,
- g) acetylating said rhein to form substantially pure diacetylrhein, and
- h) recovering said diacetylrhein.
Dependencies are inferred from the claim text.