WO2000075165A1

WO2000075165A1 - Sulfated sterol derivatives and processes for preparing the same

Info

Publication number: WO2000075165A1
Application number: PCT/US2000/015608
Authority: WO
Inventors: Norman Milstein; Ansgar Behler
Original assignee: Cognis Corporation
Priority date: 1999-06-07
Filing date: 2000-06-07
Publication date: 2000-12-14
Also published as: AU5326400A

Abstract

Processes for preparing high purity sulfated sterol derivatives in high yield, which processes include: (a) providing a sterol; (b) reacting the sterol with a source of SO3, whereby a sulfated sterol derivative is formed; (c) neutralizing the sulfated sterol derivative and precipitating the neutralized, sulfated sterol derivative; (d) contacting the derivative with a polar organic solvent and contacting the derivative with a non-polar organic solvent, in any order, are disclosed.

Description

TITLE OF THE INVENTION Sulfated Sterol Derivatives and Processes for Preparing the Same

BACKGROUND OF THE INVENTION Phytosterols, which are also referred to as plant-derived sterols, contain a similar, fused, four-ring carbon nucleus to that of other sterols, such as cholesterol, an animal-derived sterol, but differ in the configuration of their side chains at the 17-carbon position. Phytosterols differ from animal-derived sterols, not only in their origin but in their properties and, to some extent, their reactivity. Sterols have many different uses, for instance phytosterols, such as β-sitosterol, have been found to be effective in reducing dangerous serum cholesterol levels in humans.

Cholesterol and its derivatives are widely used in cosmetics and pharmaceutical products, often as an emulsifying agent.

Many sterols are found in mammals and exhibit several activities of biological importance. It is known that sterols can provide beneficial effects, such as stability or elasticity to skin and/or hair. Phytosterols, and mixtures thereof, are commercially available and are used as such or as a modified structure whose water solubility is increased by ethoxylating the hydroxy group of sterols.

Derivatives of cholesterol, such as cholesterol sulfate, are also used in cosmetics and pharmaceutical products, often as an emulsifying agent. However, phytosterol sulfate salts are not widely used. While, phytosterols are readily available and are significantly less expensive than cholesterol, modification of phytosterols, without destroying these high melting point compounds, is often more difficult than similar modification of cholesterol. Use of phytosterols rather than cholesterol can provide a significant cost savings in raw materials due to the decreased cost thereof.

Known methods of derivatizing sterols are lacking in either yield or purity of product. Thus, there is a need in the art for improved methods of preparing high purity sulfated sterol derivatives in high yield. BRIEF SUMMARY OF THE INVENTION The present invention includes processes for preparing high purity sulfated sterol derivatives in high yield. The processes in accordance with the present invention combine non-destructive synthesis with specified extractions to produce purified sterols with good color in high yield, with little or no destruction (e.g. , oxidation, thermal, etc.) of the sterol starting materials, nor side-reactions thereof. Products prepared in accordance with the present invention generally have purities of from 90 to 98%, and higher.

The present invention includes a process for preparing a high purity sulfated sterol derivative, wherein the process comprises: (a) providing a sterol; (b) reacting the sterol with a source of SO3, whereby a sulfated sterol derivative is formed; (c) neutralizing the sulfated sterol derivative and precipitating the neutralized sulfated sterol derivative; (d) contacting the derivative with a polar organic solvent and contacting the derivative with a non-polar organic solvent, in any order. The present invention also includes products prepared in accordance with such processes.

The present invention also includes a process for preparing a high purity sulfated sterol derivative, wherein the process comprises: (a) providing an azeotropically dried phytosterol in an organic solvent vehicle; (b) reacting the phytosterol with chlorosulfonic acid in the presence of at least an equivalent amount of tertiary amine at a temperature of from about 0°C to about 20°C, whereby a sulfated phytosterol derivative is formed; (c) neutralizing the sulfated phytosterol derivative; (d) mixing the neutralized sulfated phytosterol derivative with water, whereby a water/vehicle system containing precipitated sulfated phytosterol derivative is produced, filtering the water/vehicle system and drying the derivative; (e) contacting the derivative with a basic compound in a molar amount at least equivalent to the amount of tertiary amine; (f) contacting the derivative with a dry alcohol having from about 1 to about 6 carbon atoms at a temperature of from about 25°C to about 50°C; and (g) contacting the derivative with an alkane having from about 5 to about 10 carbon atoms at a temperature of from about 25°C to about 50°C. In preferred embodiments of the present invention, the sterol comprises a phytosterol, or a mixture of phytosterols. DETAILED DESCRIPTION OF THE INVENTION The present invention includes processes for preparing high purity sulfated sterol derivatives in high yield. Such sulfated sterols are substantially free from impurities, such as, for example, unreacted sterols, sterol hydrocarbons, and inorganic salts including sodium sulfate, sodium chloride, amines and amine salts, hydrochloride and sodium >-toluenesulfonate.

The term sterol is well known to those skilled in the art and generally refers to those compounds having a perhydrocyclopentanophenanthrene ring system (the ring system depicted in Formula I herein) and having one or more OH substituents, examples of which include, but are not limited to, animal sterols (e.g., cholesterol), and phytosterols, such as, for example, campesterol, ergosterol, sitosterol, stigmasterol, mixtures thereof, and the like.

Preferred sterols for use in accordance with the present invention correspond to the general formula I:

wherein R is an alkyl, substituted alkyl, alkenyl or substituted alkenyl group having

4 from one to about 10 carbon atoms. R preferably represents a substituent such as a branched alkyl group having 10 carbon atoms. A most preferred R substituent is an alkyl group of the formula II:

It is common to obtain phytosterols as mixtures of compounds such as, for example, GENEROL® 122N sterol mixtures, a product of Cognis Corporation, Cincinnati, OH. GENEROL® 122N sterol mixtures contain about 25-30% campesterol, about 17-22% stigmasterol and about 45-50% sitosterol, in addition to minor amounts of other phytosterols. Phytosterols and mixtures thereof are preferred sterols for use in accordance with the present invention. Preferred mixtures of phytosterols will generally include campesterol, ergosterol, stigmasterol, sitosterol or a combination thereof. A particularly preferred phytosterol is β-sitosterol.

In another preferred embodiment of the present invention, the sterol is azeotropically dried in an organic solvent prior to sulfating the sterol. Generally, any organic solvent capable of forming an azeotropic mixture with water for removal of the water by distillation can be used. Benzene and toluene are preferred examples of organic solvents for azeotropic drying in accordance with preferred embodiments of the present invention. Toluene is most preferred for environmental and safety reasons. In accordance with the present invention, a sterol is reacted with a source of SO3. Sources of SO3 suitable for use in accordance with the present invention include, but are not limited to, chlorosulfonic acid, oleum, amine salts of SO3, and sulfur trioxide gas, optionally contained in an inert gas carrier such as nitrogen. The preferred source of SO3 for use in accordance with the present invention is chlorosulfonic acid. A more preferred embodiment of the present invention includes the use of chlorosulfonic acid as the source of SO3, with the use of an acceptor to reduce oxidation and color formation.

The source of SO3 is generally present in a molar excess of from about 1 to about 25% excess, with respect to the amount of sterol present, preferably the amount of excess of the source of SO3 is from about 5 to about 15% molar excess.

An organic solvent is preferably used as a vehicle for the reaction. Examples of suitable organic solvent include, but are not limited to, benzene and toluene. Toluene is the preferred solvent for the reaction for environmental and safety reasons, even though benzene may be considered a poorer competitor for sources of SO3, and thus, advantageous. Additionally, it is preferred to use the same solvent as a reaction vehicle which was used for azeotropic drying of the sterol in accordance with other preferred embodiments of the present invention.

The temperature of the reaction is preferably from about 0° C to about 20° C and more preferably from about 5° C to about 10° C, though slightly lower or slightly higher temperatures are acceptable for sulfation. The reaction is highly exothermic. The temperature is preferably kept within the preferred ranges so as to limit the production of by-products, such as, for example, sulfonated toluene.

As described above, when chlorosulfonic acid is used as the source of SO3, in accordance with a preferred embodiment of the present invention, it is further preferred to react the sterol with the chlorosulfonic acid in the presence of an acceptor. The acceptor is added to compensate for hydrochloric acid produced by use of the chlorosulfonic acid. The acceptor is generally present in a molar excess of from about 1 to about 25%, with respect to the amount of phytosterol, preferably the molar excess of acceptor is from about 5 to about 15%. The preferred acceptor is triethylamine although other tertiary amine acceptors can be used in accordance with the preferred embodiments.

After the sterol has been reacted with the source of SO3, the reaction preferably having gone to completion with respect to the source of SO3, acidity of the resulting sulfated sterol derivative is neutralized. The neutralization agent can be any base that will neutralize acid groups which are present (e.g. , sulfonic acid moieties at the previous alcohol functionality). Examples of bases suitable for use as a neutralization agent in accordance with the present invention include, but are not limited to, KOH, NaOH, sodium methylate in methanol, and CaO.

Once the reaction mixture has been neutralized, water is added to the reaction mixture. Where a hydroxide base is used to neutralize the reaction mixture, further addition of water may be unnecessary to cause precipitation of the sulfated sterol derivative. Thus, neutralization and precipitation may occur substantially simultaneously. When neutralizing agents such as CaO, or sodium methylate are used, additional water is needed. Distilled, deionized water is preferred. The precipitate is preferably filtered and dried in air. In preferred embodiments including the use of chlorosulfonic acid as the source of SO₃, and wherein an acceptor is present during the reaction with the chlorosulfonic acid, it is also preferable to contact (i.e., extract) the filtered and dried precipitate with a basic reagent, preferably NaOH in methanol, though any base could be used. The quantity of base is determined by the quantity of acceptor, such as triethylamine originally charged. The sulfated sterol derivative is filtered again and preferably dried.

The extraction with a base necessary when an acceptor is used, and the subsequent contacting (i.e., extracting) of the sulfated sterol derivative with a polar organic solvent and a nonpolar organic solvent may be preformed in any order. Additionally, where no acceptor is used, the contacting of the sulfated sterol derivative with a polar organic solvent and a nonpolar organic solvent may be performed in any order. All extractions are generally carried out at elevated temperatures of from about 25°C to about 50°C. Although higher or lower temperatures can be employed depending on the volatility of the extraction solvent being used. Extractions with the polar and/or nonpolar solvents are most preferably carried out as continuous extractions. Moreover, additional subsequent extractions with polar and/or nonpolar solvents may be carried out as continuous extractions. The amount of time required to run the continuous extraction to reach maximum purity will depend upon many factors, the size of the sample, the rate of turnover of the solvent, etc. Polar and nonpolar solvents for use in accordance with the present invention are preferably dry. Polar solvents which may be used in accordance with the present invention include one or more alcohols having from about 1 to about 6 carbon atoms. Ethanol and/or methanol are preferred polar organic solvents for use in accordance with the present invention. Nonpolar solvents which may be used in accordance with the present invention include one or more alkanes having from about 5 to about 10 carbon atoms. Hexane and/or heptane are preferred nonpolar solvents for use in accordance with the present invention.

A particularly preferred process for preparing a high purity sulfated sterol derivatives in accordance with the present invention includes providing a phytosterol mixture, such as GENEROL® 122N, which has been azeotropically dried in toluene. The dried phytosterol mixture, in toluene, is combined with a molar excess of triethylamine. A molar excess of chlorosulfonic acid is slowly added to the sterol/acceptor/toluene reaction mixture. The rate of addition of the chlorosulfonic acid is slow in order to control the rate of reaction. After the reaction is completed, the solution containing the sulfated sterol derivative is neutralized with sodium methylate in methanol. Following neutralization, water is added to the reaction mixture and the sulfated sterol derivative precipitates. The precipitate is recovered via filtration and dried. The filter cake containing the sulfated sterol derivative is extracted with NaOH in methanol. The quantity of base being determined by the quantity of acceptor, such as triethylamine, originally charged. The filter cake is then dried. The dry filter cake is again extracted using a dry polar organic solvent. This is followed by an extraction with a non-polar organic solvent. A final extraction with a non-polar organic solvent is preferably carried out as a continuous extraction. Preferred processes in accordance with the present invention can achieve a product with the purity as high as 98% or higher.

The present invention will now be illustrated in more detail by reference to the following specific, non-limiting examples. EXAMPLE 1 Approximately 100 grams (0.25 moles) of GENEROL® 122N sterol mixture (Cognis Corp., Cincinnati, OH), containing about 25-30% campesterol, about 17-22% stigmasterol and about 45-50% sitosterol, in addition to other minor component phytosterols, were combined with about 900 grams of toluene and mixed until dissolved. The GENEROL® 122N sterol mixture was azeotropically dried in the toluene. The dry toluene solution was cooled to room temperature and combined with approximately a 10% molar excess of triethylamine (27.8 g, 0.275 moles), with respect to the GENEROL® 122N sterol mixture. The reaction mixture was then allowed to cool to about 5° C, and approximately a 10% molar excess of chlorosulfonic acid, (32 grams, 0.275 moles), with respect to the amount of GENEROL® 122N sterol mixture, was added drop- wise while the reaction mixture was kept at a temperature of about 5-10° C. After the chlorosulfonic acid has reacted with the sterol mixture, the reaction mixture was neutralized with a solution of 25% sodium methylate in methanol (59.4 grams, 0.275 moles). Approximately 200 grams of water were added, and the sulfated sterol derivative precipitated. The reaction mixture was filtered. The wet filter cake (precipitate) was dried, extracted with about 11 grams of sodium hydroxide dissolved in 25 grams water and 225 grams of methanol at 40° C and then air dried. The filter cake was then washed with 200 grams of dry methanol. After methanol washing, 74 grams of crude product were recovered. The crude product was then extracted with 250 ml of heptane at a temperature of about 50° C. An aliquot (8 grams) of the heptane extracted-product was again extracted with heptane using a continuous SOXHLET® extractor at 50° C for 4 hours, resulting in 7.1 grams of product containing < 1% unreacted sterol and 0.2% sodium -toluenesulfonate. The resulting sulfated sterol product was measured to be 98% pure using NMR spectroscopy.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A process for preparing a high purity sulfated sterol derivative, said process comprising:

(a) providing a sterol;

(b) reacting the sterol with a source of SO3, whereby a sulfated sterol derivative is formed;

(c) neutralizing the sulfated sterol derivative, and precipitating the neutralized, sulfated sterol derivative;

(d) contacting the derivative with a polar organic solvent; and contacting the derivative with a non-polar organic solvent, in any order.

2. The process according to claim 1 , wherein the sterol comprises a phytosterol.

3. The process according to claim 2, wherein the phytosterol is selected from the group consisting of campesterol, ergosterol, stigmasterol, sitosterol, and mixtures thereof.

4. The process according to claim 2, wherein the phytosterol is azeotropically dried.

5. The process according to claim 1 , wherein the source of SO3 comprises chlorosulfonic acid.

6. The process according to claim 5, wherein the sterol is reacted with the source of SO3 in the presence of an acceptor.

7. The process according to claim 6, wherein the acceptor comprises a tertiary amine.

8. The process according to claim 6, further comprising contacting the derivative with a basic compound subsequent to neutralizing and precipitating the derivative.

9. The process according to claim 1 , wherein the sterol is reacted with the source of SO3 at a temperature of from about 0°C to about 20°C.

10. The process according to claim 6, wherein the sterol is reacted with the source of SO3 at a temperature of from about 0°C to about 20°C.

11. The process according to claim 1 , wherein the reaction of the sterol with the source of SO3 is carried out in a vehicle comprising an organic solvent and the precipitation of the sulfated sterol derivative comprises adding water to the reaction vehicle, whereby a water/vehicle system containing the precipitated sulfated sterol derivative is produced.

12. The process according to claim 11, wherein the water/vehicle system is filtered and dried prior to contacting the derivative with the polar or nonpolar organic solvents.

13. The process according to claim 1, wherein the polar organic solvent comprises a dry alcohol having from about 1 to about 6 carbon atoms.

14. The process according to claim 13, wherein the alcohol is selected from methanol, ethanol and mixtures thereof.

15. The process according to claim 1 , wherein the nonpolar organic solvent comprises an alkane having from about 5 to about 10 carbon atoms.

16. The process according to claim 15, wherein the alkane is selected from hexane, heptane and mixtures thereof.

17. The process according to claim 13, wherein the contacting of the derivative with the polar organic solvent comprises a continuous extraction.

18. The process according to claim 15, wherein the contacting of the derivative with the polar organic solvent comprises a continuous extraction.

19. The process according to claim 1, wherein the sulfated sterol derivative is contacted with the polar organic solvent prior to being contacted with the nonpolar organic solvent.

20. The process according to claim 19, further comprising subjecting the derivative to one or more continuous extractions with a solvent selected from polar organic solvents and nonpolar organic solvents subsequent to contacting the derivative with the nonpolar organic solvent.

21. A process for preparing a high purity sulfated sterol derivative, said process comprising: (a) providing an azeotropically dried phytosterol in an organic solvent vehicle;

(b) reacting the phytosterol with chlorosulfonic acid in the presence of at least an equivalent amount of tertiary amine at a temperature of from about 0°C to about 20°C, whereby a sulfated phytosterol derivative is formed;

(c) neutralizing the sulfated phytosterol derivative;

(d) mixing the neutralized, sulfated phytosterol derivative with water, whereby a water/vehicle system containing precipitated sulfated phytosterol derivative is produced, filtering the water/vehicle system and drying the derivative;

(e) contacting the derivative with a basic compound in a molar amount at least equivalent to the amount of tertiary amine;

(f) contacting the derivative with a dry alcohol having from about 1 to about 6 carbon atoms at a temperature of from about 25°C to about 50°C; and

(g) contacting the derivative with an alkane having from about 5 to about 10 carbon atoms at a temperature of from about 25°C to about 50°C.

22. The process according to claim 21 wherein contacting the derivative with the dry alcohol comprises a continuous extraction.

23. The process according to claim 21 , wherein contacting the derivative with the alkane comprises a continuous extraction.

24. The process according to claim 21 , wherein contacting the derivative with the dry alcohol comprises a continuous extraction, and wherein contacting the derivative with the alkane comprises a continuous extraction.

25. The process according to claim 21, further comprising subjecting the derivative to one or more continuous extractions with a dry solvent selected from polar organic solvents and nonpolar organic solvents subsequent to contacting the derivative with the alkane.

26. The process according to claim 21 , wherein the phytosterol comprises a mixture of two or more phytosterols selected from the group consisting of campesterol, ergosterol, stigmasterol, and sitosterol.

27. The process according to claim 26, wherein the phytosterol comprises from about 25 to about 30% campesterol, from about 17 to about 22% stigmasterol and from about 45-50% sitosterol.

28. A product prepared by the process according to claim 21.