WO1994002495A1 - Esterification process - Google Patents
Esterification process Download PDFInfo
- Publication number
- WO1994002495A1 WO1994002495A1 PCT/GB1993/001545 GB9301545W WO9402495A1 WO 1994002495 A1 WO1994002495 A1 WO 1994002495A1 GB 9301545 W GB9301545 W GB 9301545W WO 9402495 A1 WO9402495 A1 WO 9402495A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- oxyacid
- amine
- mixture
- water
- trehalose
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
- C07H11/00—Compounds containing saccharide radicals esterified by inorganic acids; Metal salts thereof
- C07H11/04—Phosphates; Phosphites; Polyphosphates
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07F—ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM
- C07F9/00—Compounds containing elements of Groups 5 or 15 of the Periodic System
- C07F9/02—Phosphorus compounds
- C07F9/06—Phosphorus compounds without P—C bonds
- C07F9/08—Esters of oxyacids of phosphorus
- C07F9/09—Esters of phosphoric acids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/582—Recycling of unreacted starting or intermediate materials
Definitions
- the present: invention relates to a process for the esterification of hydroxylated compounds.
- Esters particularly phosphate esters, are widespread in nature and occupy a central role in biochemical processes.
- carbohydrate phosphates which are used extensively for studying biosynthetic pathways, and inositol phosphates which act as secondary cellular messengers.
- these compounds are often present at low concentration and are usually difficult to isolate in pure form, it is often necessary to synthesise them chemically.
- ester functionalities include betamethasone, which is used in the treatment of asthma, and menadiol, which is used for haemorrhage control. Both of these compounds are orthophosphates.
- Phosphate esters are structural features of several bacterial polysaccharides which are used in vaccines to protect against diseases such as pneumonia and meningitis; synthetic antigens with this type of structure have, in recent years, been prepared with a view to using them as synthetic vaccines. It is therefore clear that the introduction of the ester functional group is necessary for the preparation of a number of pharmaceutical products. Another area in which esters have proved to be useful is in detailed biochemical studies, including studying the effects of structural modifications on the biological activity of various compounds.
- Such studies include pharmacological testing of new drugs and therapeutic agents and also investigations into the mechanism of diseases including cancer. In studies such as these, it is often particularly useful to use radioactive esters into which a radioactive isotope of one of the atoms has been incorporated.
- esters It is often impossible to obtain the required ester compounds by any other method than chemical synthesis but, in fact, the chemical synthesis of esters has, in the past, proved to be extremely difficult.
- Direct methods for the synthesis of esters are available and an example of such a method is the esterification of a hydroxylated compound (HC) using phosphoric acid or polyphosphoric acid (MacDonald, The Carbohydrates, 1A, 254 (1972) W. Pigman and D. Horton (Eds). Academic Press, New York).
- HCs hydroxylated compound
- MacDonald The Carbohydrates, 1A, 254 (1972) W. Pigman and D. Horton (Eds). Academic Press, New York.
- the utility of this method is limited because many HCs are sensitive to the reaction conditions which are, of course, strongly acidic and often the products undergo further reaction to form modified compounds such as cyclic esters or anhydrides. This route cannot therefore be used for most compounds.
- the present invention is based on the discovery that ester formation can be promoted remarkably easily in solutions containing a hydroxylated compound and an oxyacid salt.
- a process for the esterification of a hydroxylated compound (HC) other than a starch, or the amidation of an organic amine characterised in that the process comprises reacting the HC or amine with an oxyacid, oxyacid anion or a mixture thereof wherein the oxyacid or its anion is capable of accepting a lone pair of electrons from the oxygen of the HC or nitrogen of the amine.
- oxygen includes within its scope hetero-oxyacids in which one or more of the oxygen atoms have been replaced by a hetero atom, in particular one such as nitrogen, sulphur or a halogen atom.
- hetero-oxyacids include thiophosphates, halophosphates and phosphonitriles.
- hydroxylated compound refers to any compound containing a hydroxyl group or an alkoxy or phenoxy anion. Preferred hydroxylated compounds are hydroxylated organic compounds although inorganic compounds, for example oxyacids may be used.
- hydroxylated organic compounds include sugars, proteins, glycoproteins, peptides, glycopeptides and glycoconjugates and other molecules having sugar functionality, amino acids, alditols, cyclitols, phosphate esters and carboxylic acids.
- the conditions of the process of the present invention are quite surprisingly mild and one particular advantage of this is that, because of the mild pH conditions, it is not necessary to protect (and subsequently to deprotect) other functional groups of the HC. This means that the overall number of steps in the process is reduced and that therefore the overall yield of the final product is increased, thus increasing the cost-effectiveness of the esterification process. Furthermore, the mild reaction conditions also ensure that the reaction is suitable for nearly any starting material and that there is little likelihood of products undergoing unwanted further reaction.
- the oxyacid may be an oxyacid of an element M, which is capable of forming trimeric oxyacids of the structure:
- M is an electron accepting element
- X is oxygen or a hetero-atom such as sulphur or a substituted nitrogen atom
- Y is oxygen, hydrogen or a hetero atom such as sulphur or a substituted nitrogen atom
- n is 0 or 1 and m is 0 to 2, depending on the valency of M.
- elements M which are capable of forming trimeric oxyacids include phosphorus, boron and silicon.
- the nitrogen atom will be substituted by hydrogen or an alkyl group.
- Phosphorus is capable of forming the metaphosphate oxyacid. Because of electron deficiency at the phosphorus atom, the ion tends to polymerise and may form the following trimer:
- boron forms an oxyacid having the following structure:
- metaphosphoric acid One suggestion for the reaction mechanism for esterification using a metaphosphate is as follows:
- This reaction mechanism indicates that it is the metaphosphate monomer rather than the trimer which is the reactive species.
- the usefulness of the invention is net dependent on the accuracy or otherwise of this reaction mechanism.
- phosphate oxyacids and anions It is not always necessary to use a salt of the oxyacid anion which forms the type of monomer structure shown above.
- a salt of the oxyacid anion which forms the type of monomer structure shown above.
- phosphorus although metaphosphate salts are preferred, other oxyacid salts such as orthophosphate, diphosphate, triphosphate, polyphosphate, phosphonate, phosphinate, peroxyphosphate, and hypophosphate salts or their free acids may also be used.
- orthophosphate esters is indeed the metaphosphate monomer
- the reactivity of ortho-, di-, tri- and polyphosphate oxyacids can be explained by the fact that in solution these oxyacids and their anions will be in equilibrium with the metaphosphate species via which the reaction appears to proceed.
- metaphosphate is continuously reacting with the HC and so the equilibrium with the other phosphates will be driven to the metaphosphate side allowing the reaction to continue.
- phosphorus based oxyacids which have been found to be useful in the present invention are hetero-oxyacids such as thiophosphate, halophosphates and phosphonitriiic compounds.
- the cation of the oxyacid salt will be such as to ensure that the salt is soluble in the solvent in which the reaction is carried out.
- the cation may be an alkali or alkaline earth metal such as sodium, potassium or magnesium.
- larger cations such as lanthanum, caesium or less ionic species such as lithium and ammonium may be more appropriate.
- the cation may be chosen because of its catalytic effect on the reaction.
- the counter ion will be chosen so that the salt does not have an inappropriate pK value, particularly bearing in mind the preferred pH operating conditions which will be discussed in more detail below.
- the reaction can be carried out in both aqueous and organic solvents.
- organic solvent it is preferred that it is a highly polar solvent such as dimethyl sulphoxide (DMSO).
- This method of forming the reaction mixture works particularly well if the water in the KC/oxyacid salt solution is initially present in considerable excess (for example, at least 2, 5, 10, 20, 50 or 100 .fold (on a weight basis).
- most of the water is removed, so as to leave, say, less than one part (for example from 0.1 to 30% w/w), based on the starting amount of HC or amine.
- a balance has to be struck between considerations of yield, which favour removal of a large amount of water, and considerations of time and energy expenditure, which favours the converse. The optimal place to draw the balance will doubtless vary with the nature of the reactants and the operator's process conditions.
- the water can be removed by any appropriate physical or chemical method. Examples of suitable physical methods, which are generally preferred, are evaporation, evaporation under reduced pressure and freeze drying. Considerations of energy consumption and time will often dictate the best in any particular circumstances.
- An alternat ⁇ ve method for preparing the reaction mixture is to dissolve the HC or amine and the oxyacid or oxyacid salt in an organic solvent which may also contain water in an amount of up to 30% (w/w) based on the starting amount of HC or amine.
- a polar solvent such as dimethylsulphoxide should generally be used. It has been found that in many cases the process is more efficient if the reaction mixture contains water in an amount of from 0.1 to 15% w/w of the HC.
- the reaction can be carried out at almost any pH but a preferred pH range is from 1 to 9 and the best results are obtained when the pH is from 2 to 6.
- a preferred pH range is from 1 to 9 and the best results are obtained when the pH is from 2 to 6.
- one advantage of the reaction is that it does work well under mild conditions of pH, for example from pH 4.5 to 6 and this can be particularly important when the HC or the product ester is sensitive to highly acidic conditions.
- the pH will preferably be greater than 7 in order to ensure that a free amine exists in the reaction mixture.
- the pH will be between 7.5 and 9, although use of pH of 10 or even higher may be necessary in some cases.
- Any hydroxylated compound may be esterified or any amine amidated by this method but, in particular, the method is suitable for the esterification of organic compounds such as: sugars, particularly non-reducing sugars such as trehalose and sucrose and reducing-sugars such as lactose and maltose; proteins; glycoproteins, peptides, giycopeptides and giycoconjugates and other molecules having sugar functionality; amino acids, particularly, serine and threonine; and other organic compounds such as alditols and cyclitols, carboxylic acids, organic oxyacids, particularly phosphates, and compounds containing hydroxyl groups or alkoxy or phenoxy anions.
- organic compounds such as: sugars, particularly non-reducing sugars such as trehalose and sucrose and reducing-sugars such as lactose and maltose; proteins; glycoproteins, peptides, giycopeptides and giy
- the invention has application to polysaccharides other than starch, oligosaccharides (say with 3 to 10 monosaccharide units) and di- and mono-saccharides.
- Inorganic hydroxylated compounds which may be esterified by the method of the invention include oxyacids themselves and, for example, the esterification reaction of the invention is of use for the synthesis of di-, tri- and poly-phosphates.
- reaction is most successful for primary and secondary HCs and amines, although it is possible to esterify tertiary derivatives, particularly if the substituents are not too bulky.
- the reaction mixture After the formation of the starting mixture, it may then be further treated to maximise the esterification reaction. In some cases, it may be preferable to heat the reaction mixture for a time between 0.1 hour and 40 days at a temperature of from 20 to 200°C, preferably 50 to 100°C. The heating may be carried out in a sealed system, particularly if a high temperature is used and will increase the rate of the esterification reaction. Since water is a product of the esterification process, removal of water from the system as the reaction proceeds will cause the equilibrium to be shifted so that more ester is formed from the reaction. One way of removing the water would be to heat the mixture in an unsealed system allowing water to evaporate.
- the ester or amidate products may be isolated by any suitable method: by ion exchange chromatography, for example. If more than one reaction product is obtained, it is generally easy to separate the different products by chromatography. Alternatively, the ester may be left in the resulting mixture and treated or allowed to react further to produce a compound, or mixture, of choice.
- the process of the present invention has made it possible to obtain new esters and amidates which could not be prepared by any previously known route.
- esters of acid-labile sugars such as sucrose and trehalose and therefore, in further aspects of the invention, there are provided trehalose-2-phosphate, trehalose-3-phosphate, trehalose-4-phosphate and a number of mono-orthophosphates of sucrose. These compounds are new and could only have been prepared by previously known methods with considerable difficulty and cost.
- FIGURE 1 is a 1 H nmr spectrum of trehalose-6-phosphate obtained from an orthophosphate salt by the method of the present invention
- FIGURE 2 is a 1 H nmr spectrum of trehalose-2-phosphate obtained from an orthophosphate salt by the method of the present invention
- FIGURE 3 is a 1 H nmr spectrum of trehalose-4-phosphate obtained from an orthophosphate salt by the method of the present invention
- FIGURE 4 is a 1 H nmr spectrum of trehalose-3-phosphate obtained from an orthophosphate salt by the method of the present invention
- FIGURE 5 is a HPLC ion-exchange chromatogram obtained from a sample of ⁇ , ⁇ '-trehalose treated with sodium phosphate according to the method of the present invention.
- FIGURE 6 is a 1 H nmr spectrum of trehalose-3-phosphate obtained from a metaphosphate salt by the method of the present invention.
- FIGURE 7 is a 1 H nmr spectrum of trehalose-6-phosphate obtained from a metaphosphate salt by the method of the present invention.
- Bio-Rad AG 1 The preparation, closed to the atmosphere, is heated at 56 °C for 10 days after which it is reconstituted in deionised water (100 ml) and the solution applied to an anion-exchanged column, 120 ⁇ 2 cm, Bio-Rad AG 1 resin which had been washed successively with 1M sodium hydroxide, water, IM sodium acetate, water and is therefore in the acetate form.
- the expression Bio-Rad AG 1 is a trade mark.
- the column was first washed with water to remove unreacted trehalose (for recycling if so desired) and any other unbound material, and then eluted with a 0.2 to 0.8M ammonium acetate aqueous solution gradient to give fractions containing the isomeric trehalose mono-orthophosphates separated from inorganic orthophosphate.
- the fractions containing the trehalose phosphates were then analysed on an analytical ion-exchange column (Dionex BioLC PA 100) and the fractions containing each of the four pure isomers were combined and their solutions freeze-dried to give as analytically pure amorphous solids, trehalose monophosphates as their ammonium salts.
- Dionex BioLC PA 100 is a trade mark. Fraction 1, 0.085 g (6.6%), fraction 2, 0.035g (2.7%), fraction 3, 0.041g (3.1%), fraction 4, 0.027% (2.1%). Total 0.188g (14.6%). All four products gave, on treatment with the enzyme alkaline phosphates, ⁇ , ⁇ '-trehalose (identified by HPLC ion-exchange chromatography) and inorganic orthophosphate (identified colorimetrically using ammonium molybdate).
- Example 2 Using conditions similar to those of Example 1, but modified as shown in the six entries (a) to (f) for Example 2 in Table 1, phosphate esters of ⁇ , ⁇ '-trehalose were prepared from ⁇ , ⁇ '-trehalose.
- sucrose is an extremely acid labile disaccharide and consequently is not amenable to direct phosphorylation with phosphoric acid.
- sucrose is an extremely acid labile disaccharide and consequently is not amenable to direct phosphorylation with phosphoric acid.
- the majority of the sucrose isomeric esters are new compounds and, furthermore, would be very difficult to creoare using existing methods. Examples 4 to 7
- esterification method of the invention is extremely flexible and can be used to esterify a large range of compounds under relatively mild conditions.
- the starting materials can be recycled so that increased amounts of product can be obtained.
- Example 8 Formation of phosphate esters from preparations of ⁇ , ⁇ ' -trehalose and sodium metaphosphate.
- Example 2 The procedure of Example 1 was repeated except that ⁇ , ⁇ '-trehalose dihydrate (1.0 g, 2.6 mmol) was dissolved in a solution of sodium metaphosphate (0.1 M, 100 mi). The preparation is frozen to -78° as before, freeze dried, closed to the atmosphere and heated at 56°C for either 5 days or 12 days. The reaction was repeated at different PH values and the results are shown in Table 2 below.
- the percentage of phosphate shown in Table 2 is determined from detector response and is therefore an underestimate, possibly by a factor as high as 2.
- the amount of phosphate formed will depend upon the moisture content and on the temperature at which the reaction is carried cut. In several separate experiments carried cut at higher temperature but for shorter times, the yield of phosphates increased to about 40% based on detector response. Again, this is an underestimate and the true value may be as much as twice the detector response value.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP6504297A JPH07509457A (en) | 1992-07-28 | 1993-07-22 | Esterification method |
EP93917889A EP0652886A1 (en) | 1992-07-28 | 1993-07-22 | Esterification process |
AU47147/93A AU4714793A (en) | 1992-07-28 | 1993-07-22 | Esterification process |
NO950321A NO950321D0 (en) | 1992-07-28 | 1995-01-27 | Esterification Process |
FI950381A FI950381A (en) | 1992-07-28 | 1995-01-27 | Procedure for esterification |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9216026.6 | 1992-07-28 | ||
GB929216026A GB9216026D0 (en) | 1992-07-28 | 1992-07-28 | Esterification process |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994002495A1 true WO1994002495A1 (en) | 1994-02-03 |
Family
ID=10719437
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB1993/001545 WO1994002495A1 (en) | 1992-07-28 | 1993-07-22 | Esterification process |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP0652886A1 (en) |
JP (1) | JPH07509457A (en) |
AU (1) | AU4714793A (en) |
CA (1) | CA2141301A1 (en) |
FI (1) | FI950381A (en) |
GB (1) | GB9216026D0 (en) |
NO (1) | NO950321D0 (en) |
WO (1) | WO1994002495A1 (en) |
ZA (1) | ZA935408B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6146886A (en) * | 1994-08-19 | 2000-11-14 | Ribozyme Pharmaceuticals, Inc. | RNA polymerase III-based expression of therapeutic RNAs |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2865762A (en) * | 1954-09-16 | 1958-12-23 | Int Minerals & Chem Corp | Pudding mix |
US2884413A (en) * | 1956-04-06 | 1959-04-28 | Corn Products Co | Orthophosphate esters of starch |
US2884412A (en) * | 1953-09-04 | 1959-04-28 | Int Minerals & Chem Corp | Phosphate-modified starches and preparation |
US2961440A (en) * | 1956-01-23 | 1960-11-22 | Corn Products Co | Process for preparing inorganic starch esters |
EP0228612A2 (en) * | 1985-12-16 | 1987-07-15 | Ss Pharmaceutical Co., Ltd. | A derivative of alpha, alpha-trehalose and a process for preparing the same |
-
1992
- 1992-07-28 GB GB929216026A patent/GB9216026D0/en active Pending
-
1993
- 1993-07-22 WO PCT/GB1993/001545 patent/WO1994002495A1/en not_active Application Discontinuation
- 1993-07-22 EP EP93917889A patent/EP0652886A1/en not_active Withdrawn
- 1993-07-22 AU AU47147/93A patent/AU4714793A/en not_active Abandoned
- 1993-07-22 JP JP6504297A patent/JPH07509457A/en active Pending
- 1993-07-22 CA CA002141301A patent/CA2141301A1/en not_active Abandoned
- 1993-07-27 ZA ZA935408A patent/ZA935408B/en unknown
-
1995
- 1995-01-27 FI FI950381A patent/FI950381A/en not_active Application Discontinuation
- 1995-01-27 NO NO950321A patent/NO950321D0/en unknown
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2884412A (en) * | 1953-09-04 | 1959-04-28 | Int Minerals & Chem Corp | Phosphate-modified starches and preparation |
US2865762A (en) * | 1954-09-16 | 1958-12-23 | Int Minerals & Chem Corp | Pudding mix |
US2961440A (en) * | 1956-01-23 | 1960-11-22 | Corn Products Co | Process for preparing inorganic starch esters |
US2884413A (en) * | 1956-04-06 | 1959-04-28 | Corn Products Co | Orthophosphate esters of starch |
EP0228612A2 (en) * | 1985-12-16 | 1987-07-15 | Ss Pharmaceutical Co., Ltd. | A derivative of alpha, alpha-trehalose and a process for preparing the same |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6146886A (en) * | 1994-08-19 | 2000-11-14 | Ribozyme Pharmaceuticals, Inc. | RNA polymerase III-based expression of therapeutic RNAs |
US6852535B1 (en) | 1994-08-19 | 2005-02-08 | Sirna Therapeutics, Inc. | Polymerase III-based expression of therapeutic RNAS |
Also Published As
Publication number | Publication date |
---|---|
JPH07509457A (en) | 1995-10-19 |
ZA935408B (en) | 1995-01-27 |
NO950321L (en) | 1995-01-27 |
FI950381A0 (en) | 1995-01-27 |
NO950321D0 (en) | 1995-01-27 |
AU4714793A (en) | 1994-02-14 |
EP0652886A1 (en) | 1995-05-17 |
GB9216026D0 (en) | 1992-09-09 |
FI950381A (en) | 1995-01-27 |
CA2141301A1 (en) | 1994-02-03 |
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