Purification method of branched polyethylene glycol

Abstract

To provide a method for efficiently manufacturing a high purity branch type polyethylene glycol compound having reduced vinyl ether group terminals with high purity by an industrially practical method.SOLUTION: A method for refining a branch type polyethylene glycol compound comprises: adding at least one kind of solid acids selected from a group consisting of a magnesium silicate, aluminum silicate and magnesium aluminum silicate and having a specific surface area of 50-250 m2 / g to the branch type polyethylene glycol compound having a specific structure and having a weight average molecular weight of 40000 or more in the presence of an aprotic organic solvent to obtain a mixture; and agitating the mixture to separate the solid acids.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for purifying a polyethylene glycol compound used, for example, in pharmaceutical applications. More specifically, the present invention is a purification method for obtaining a branched polyethylene glycol compound suitable as a raw material for an activated polyethylene glycol compound for chemical modification use in a drug delivery system.

[0002] The present invention is particularly suitable for pharmaceutical applications including the modification of polypeptides, enzymes, antibodies, and other low-molecular-weight drugs, nucleic acid compounds including genes and oligonucleic acids, nucleic acid pharmaceuticals, and other bioactive substances, or the application to drug delivery system carriers such as liposomes, polymer micelles, and nanoparticles.

Background Art

[0003] Polyethylene glycol (PEG) is widely known as a standard carrier in drug delivery systems and is a very useful and indispensable material. By modifying drugs such as bioactive substances and liposomes with a polyethylene glycol compound, the high hydration layer and steric repulsion effect of polyethylene glycol can suppress the capture of the drug by the reticuloendothelial system (RES) and excretion by the kidney, enabling improvement of the blood retention of the drug and reduction of antigenicity.

[0004] In recent years, in order to form a more extensive and effective hydration layer and reduce the enzymatic degradability of the linker part between polyethylene glycol and the drug, the development of drugs using branched polyethylene glycol compounds has been progressing. Among them, branched polyethylene glycol compounds having a polyhydric alcohol as a basic skeleton as shown in Patent Document 1 and Patent Document 2 do not have a linker in the basic skeleton that may be decomposed in vivo, such as an amide bond or a urethane bond. Therefore, it has a low possibility of being hydrolyzed into single-stranded polyethylene glycol during the manufacturing process and in the body, has high stability, and is useful. In particular, high-molecular-weight branched polyethylene glycol having a molecular weight of 40,000 or more is particularly suitable for pharmaceutical modification applications because of its excellent blood retention property.

[0005] As an example of a method for producing a branched polyethylene glycol compound having a polyhydric alcohol as a basic skeleton, the method for producing a dibranched polyethylene glycol compound described in Patent Document 1 is shown in FIG. 1. According to this document, after the polymerization of polyethylene glycol, the hydroxyl group at the polymerization terminal is blocked by alkyl etherification.

[0006] However, depending on the polymerization conditions of polyethylene glycol, as shown in Non-Patent Document 1, as the heat history increases with the progress of polymerization, the hydroxyl group at the polymerization terminal is likely to undergo elimination, and a side reaction occurs in which it is converted to a vinyl ether group. When this side reaction occurs, the branched polyethylene glycol compound after polymerization contains, as an impurity, a polyethylene glycol compound having a vinyl ether group at the terminal. This vinyl etherified terminal cannot be alkylated in the subsequent alkyl etherification step and may remain, and may be converted to a hydroxyl group in a subsequent step. As a result, the target branched polyethylene glycol compound contains, as an impurity, a bifunctional polyethylene glycol compound having a hydroxyl group at the polyethylene glycol terminal in addition to the hydroxyl group that serves as a modification site with the drug. The bifunctional polyethylene glycol compound causes dimerization of the drug when the drug is modified, and it is difficult to separate and purify the main component and the dimer after drug modification. For this reason, a manufacturing technique for reducing the vinyl ether group in the polyethylene glycol compound is strongly desired.

[0007] Non-Patent Document 2 and Patent Document 3 describe that a vinyl ether group is hydrolyzed under acidic conditions such as those of a hard acid and converted to a hydroxyl group. However, when treating a polyethylene glycol compound under acidic aqueous solution conditions, an extraction step into a large amount of organic solvent is required after the treatment, which is not efficient in terms of solvent recovery.

[0008] Alternatively, in order to avoid the extraction operation, it is also conceivable to convert the vinyl ether to a hydroxyl group in the polymerization tank by adding an acid after the polymerization of ethylene oxide until the system becomes acidic. In this case, it is necessary to perform the treatment at a high temperature to prevent solidification of the polyethylene glycol in the tank. However, a high molecular weight branched polyethylene glycol compound is likely to deteriorate in quality due to degradation of the polyethylene glycol chain over time or decomposition at the branched portion under high temperature and low pH conditions.

[0009] Patent Document 4 describes a method of physically adsorbing and separating impurities with different numbers of hydroxyl groups using an adsorbent from a polyoxyalkylene derivative. However, in the case of a branched polyethylene glycol compound, there is only a description of the compound after alkyl etherification, and there is no description regarding the hydroxyl group before alkyl etherification.

Prior Art Documents

Non-Patent Documents

[0010]

Non-Patent Document 1

Non-Patent Document 2

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0012] Thus, although the branched polyethylene glycol compound with reduced vinyl ether groups is an important material in pharmaceutical applications, it has not been obtained by an industrially easy manufacturing method and has many problems.

[0013] The problem of the present invention is to efficiently produce a highly pure branched polyethylene glycol compound with a reduced vinyl ether group terminal in an industrially feasible method with good purity.

Means for Solving the Problems

[0014] As a result of intensive studies to solve the above problems, the present inventors have found a purification method for reducing by treating a branched polyethylene glycol compound having a vinyl ether group with a solid acid in an organic solvent to convert the vinyl ether group into a hydroxyl group.

[0015] That is, the present invention is as follows. (1) Impurities represented by the following formula (ii)

Chemical formula

Chemical formula

Advantages of the Invention

[0016] According to the present invention, it is possible to convert the vinyl ether group of impurities contained in the branched polyethylene glycol compound into a hydroxyl group under mild conditions by treating it in a solid acid. Therefore, the purification method of the present invention can easily provide a high-quality polyethylene glycol compound suitable for pharmaceutical use on an industrial scale.)

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present invention will be described in detail. The details of the present invention are a method for purifying a polyethylene glycol compound represented by the general formula [1].)

Chemical formula

[0019] In formula [1], Z is the residue obtained by removing the active hydrogen groups (GH)n from a compound (Z(GH)n where n = 3 to 5) having 3 to 5 active hydrogen groups (GH). The active hydrogen group (GH) means a functional group containing active hydrogen H. As the active hydrogen group (GH), a hydroxyl group (OH) is particularly preferred. Specific examples of the compound (Z(GH)n where n = 3 to 5) having 3 to 5 active hydrogen groups (GH) include polyhydric alcohols such as glycerin, diglycerin, triglycerin, trimethylolpropane, pentaerythritol, xylitol, etc., and alkanolamines such as triethanolamine, N,N,N’,N’-tetrakis(2-hydroxyethyl)ethylenediamine, etc. Compounds such as glycerin, xylitol, and pentaerythritol are preferred.

[0020] Y 1 and Y 2 are the linking groups between Z and A and between Z and Polymer, respectively, and are alkylene groups having 1 to 12 carbon atoms. Specific alkylene groups include methylene group, ethylene group, propylene group, isopropylene group, butylene group, isobutylene group, pentylene group, isopentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, etc. These may be branched. Also, Y 1 and Y 2 more preferably have 1 or more carbon atoms, and even more preferably 4 or less carbon atoms.

[0021] A is a protecting group that protects an active group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a thiol group. The protecting group is, for example, John Wiley & Sons Inc.'s "Protecting Groups in Organic Synthesis", Theodora W. Greene and Peter It is described in G.M.Wuts. The protecting group is preferably a protecting group that can withstand ethylene oxide polymerization reaction conditions and may span multiple residues in Z. When the active group is a hydroxyl group, the protecting groups for the hydroxyl group include a benzyl group, a THP group (tetrahydropyranyl group), a t-butyl group, a triphenylmethyl group, a methylenedioxy group, a benzylidene acetal group, and an isopropylidene group. When the active group is a carboxyl group, the protecting groups for the carboxyl group include orthoesters such as a 2,6,7-trioxabicyclo[2.2.2]octyl group (OBO ester). When the active group is an amino group, the protecting groups for the amino group include a tosyl group, a THP group, a triphenylmethyl group, and a benzyl group. When the active group is a thiol group, the protecting groups for the thiol group include a benzyl group and a t-butyl group. Among these, the protecting group for the hydroxyl group is preferred, and a benzyloxy group is more preferred.

[0022] The Polymer is a linear or branched polyethylene glycol chain. A branched polyethylene glycol chain is a polyethylene glycol chain that branches into two or more chains via a linker in the middle, and there may be multiple branching points. As an example, it is a polyethylene glycol chain that branches into two or more chains with a polyhydric alcohol such as glycerin shown in the following formula (i) as a branching point.

[0023]

Chemical formula

[0024] The weight average molecular weight of the polyethylene glycol compound is 40,000 or more, preferably 60,000 or more. The by-production of vinyl ether groups during polymerization varies depending on the temperature, type, and amount of the catalyst, but by-production may start when it is 40,000 or more, and tends to increase as the molecular weight increases. Moreover, there is no particular upper limit to the weight-average molecular weight of the polyethylene glycol compound, but it is often 100,000 or less.

[0025] l = 0 or 1, m = 0 or 1, and a and b are integers satisfying 1 ≤ a ≤ 4, 2 ≤ b ≤ 4, and 3 ≤ a + b ≤ 5

[0026] (Production Example of the Compound of Formula [1]) The compound of formula [1] can be produced, for example, as follows. Ethylene oxide is reacted with the compound represented by the following formula [2] in the presence of an alkali catalyst for polymerization, and then an inorganic acid is added until the pH ranges from 6 to 8 to neutralize the alkali catalyst. [Chemical Formula] (In formula [2], Z, Y 1 , Y 2 , A, l, m, a, and b are the same as described above.)

[0027] The alkali catalyst is not particularly limited, and examples thereof include metallic sodium, metallic potassium, sodium hydride, potassium hydride, sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, and the like. Regarding the concentration of the alkali catalyst, 50 to 150 mol% is preferable. If it is less than 50 mol%, the polymerization reaction rate of alkylene oxide becomes slow, resulting in an increase in heat history and side reactions such as terminal vinyl etherification, and the quality of the target product tends to deteriorate. If it exceeds 150 mol%, the viscosity of the reaction solution increases during the alcoholization reaction, or it solidifies, the stirring efficiency decreases, and the alcoholization tends not to be promoted.

[0028] Before ethylene oxide polymerization, in order to suppress the by-production of polyethylene glycol compounds derived from moisture, an organic solvent may be added and azeotropic dehydration may be performed to reduce the moisture content in the system. The organic solvent for azeotropic dehydration is not particularly limited, and examples thereof include methanol, ethanol, toluene, benzene, xylene, etc. Toluene, whose boiling point is close to that of water, is preferred. The azeotropic temperature is preferably 50 to 130 °C. If it is lower than 50 °C, the viscosity of the reaction solution increases and moisture tends to remain. If it is higher than 130 °C, there is a risk of condensation reaction. If there is residual moisture, it is preferable to repeat azeotropic dehydration.

[0029] The polymerization of ethylene oxide is carried out without solvent or in a solvent. The reaction solvent is not particularly limited as long as it is an aprotic solvent such as toluene, benzene, xylene, acetonitrile, ethyl acetate, tetrahydrofuran, chloroform, methylene chloride, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, etc., but toluene or no solvent is preferred. The reaction time is preferably 1 to 24 hours. If it is shorter than 1 hour, the reaction may not be completed. If it is longer than 24 hours, the above-mentioned decomposition reaction may occur.

[0030] The polymerization temperature is preferably 50 to 130 °C. If it is lower than 50 °C, the rate of the polymerization reaction is slow, and the quality of the compound represented by formula [1] tends to deteriorate due to an increase in the heat history. If it is higher than 130 °C, side reactions such as terminal vinyl etherification may occur during polymerization, and the quality of the target product tends to deteriorate. During polymerization, as the molecular weight increases, the viscosity of the reaction solution increases, so an aprotic solvent, preferably toluene, may be added as appropriate.

[0031] Inorganic acids used for neutralizing the alkali catalyst after recombination include hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, sulfurous acid, etc., and phosphoric acid is preferred. The addition amount is adjusted to achieve a pH of 6 to 8. If the pH is less than 6, decomposition may occur between Z and Polymer. When the pH is greater than 8, since the neutralization is not complete, the solid acid added later may be deactivated, and there is a risk that the de-vinyl etherification may not proceed sufficiently. Regarding the neutralization temperature, 90 to 130 °C is preferred. If it is lower than 90 °C, the viscosity of the polyethylene glycol compound increases, and the stirring efficiency decreases, resulting in a locally increased acid concentration and a risk of decomposition between Z and Polymer. Also, if it is higher than 130 °C, the oxidative degradation of the polyethylene glycol compound is promoted, and there is a tendency for the acidity to increase somewhat.

[0032] (Treatment with solid acid) For the compound represented by formula [1], in the presence of an aprotic organic solvent, at least one solid acid selected from the group consisting of magnesium silicate, aluminum silicate, and aluminum magnesium silicate having a specific surface area of 50 to 250 m 2 / g is added to convert the vinyl ether group to a hydroxyl group and purify the impurity having a vinyl ether group.

[0033] The impurity having a vinyl ether group is one in which a part of the polyethylene glycol terminal is substituted with a vinyl ether group, and specifically has the structure shown in the following formula (ii). [Chemical formula] TIFF0007688818000007.tif3123 (In the formula, Z, Y 1 , Y 2 , A, Polymer, l, m, a are the same as above, and satisfy 0 ≦ c ≦ 3, 1 ≦ d ≦ 4 and 3 ≦ a + c + d ≦ 5.)

[0034] An aprotic solvent is a solvent lacking acidic hydrogen and having no proton-donating property. A solvent with low polarity and high solubility of the polyethylene glycol compound is desirable. Examples of aprotic organic solvents include toluene, xylene, benzene, ethyl acetate, butyl acetate, chloroform, dichloromethane, acetone, acetonitrile, tetrahydrofuran, etc. Preferred aprotic organic solvents are toluene and ethyl acetate, and more preferably toluene. Protic solvents and highly polar solvents are not preferred because there is a risk that metal components will elute from the solid acid.

[0035] The amount of the solvent is preferably 5 times by weight or more based on the polyethylene glycol compound represented by the formula [1]. If it is less than 5 times by weight, the viscosity of the solution is high, resulting in poor reaction efficiency and further poor yield. Therefore, it is advantageous in production to set it at 5 times by weight or more. Even if the amount of the solvent is 30 times by weight or more, the reaction efficiency does not change and is good. However, in the subsequent filtration operation, the processing capacity increases, the man-hours increase, the yield decreases, and it is disadvantageous in terms of cost. For these reasons, the preferred amount of the solvent is 5 to 20 times by weight, and more preferably 7 to 15 times.

[0036] Using the above solvent, the polyethylene glycol compound is dissolved. The charging order into the processing container can be either the polyethylene glycol compound or the aprotic organic solvent. Depending on the molecular weight of the polyethylene glycol compound, heating may be required. There is no particular limitation on the method, but generally, it can be dissolved by heating to 30 °C or higher.

[0037] The solid acid is at least one selected from the group consisting of magnesium silicate, aluminum silicate, and aluminum silicate - magnesium silicate, and has a specific surface area of 50 to 250 m 2A solid acid with a specific surface area of / g is used. The larger the specific surface area of the solid acid, the more effective it is for converting a vinyl ether group to a hydroxyl group as a solid acid. However, since it leads to a decrease in productivity due to a decrease in the filtration rate when filtering the solid acid and the solution, the above range is preferred. From this perspective, the specific surface area of the solid acid is preferably 100 m 2 / g or more, and more preferably 200 m 2 / g or less.

[0038] As magnesium silicate, those with an MgO / SiO 2 ratio in the range of 10 / 90 to 30 / 70 are used. Specifically, synthetic magnesium silicates such as Kyoward 600 (manufactured by Kyowa Chemical Industry Co., Ltd.) and Tomita AD600 (manufactured by Tomita Pharmaceutical Co., Ltd.) can be mentioned. As aluminum silicate, those with an Al 2 O 3 / SiO 2 ratio in the range of 10 / 90 to 25 / 75 are used. Specifically, synthetic aluminum silicates such as Kyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.), Tomita AD700 (manufactured by Tomita Pharmaceutical Co., Ltd.), and silica alumina (manufactured by Catalytic Chemical Industry Co., Ltd.) can be mentioned. The above solid acids may be used alone or in combination. Preferably, it is synthetic aluminum silicate.

[0039] The amount of the solid acid is preferably in the range of 0.2 to 1 weight times based on the polyethylene glycol compound represented by the formula [1]. If it is less than 0.2 weight times, vinyl ether cannot be decomposed sufficiently. If it is more than 1 weight times, polyethylene glycol compound remains in the filter cake when filtering the slurry solution after treatment, resulting in a decrease in yield. Therefore, 0.2 to 1.0 weight times is preferred, and more preferably 0.3 to 1.0 weight times.

[0040] The treatment temperature is preferably 25 to 60 °C. If the temperature is lower than 25 °C, the viscosity of the solution is high and the purification efficiency deteriorates. Also, depending on the structure and molecular weight of the polyethylene glycol compound, crystals may precipitate, so 25 °C or higher is preferred. The preferred temperature range is 40 to 60 °C.

[0041] The processing time is not particularly limited, but preferably it is between 30 minutes and 12 hours, more preferably 1 to 3 hours. Also, the atmosphere for carrying out this operation is not particularly limited, but preferably, for the purpose of minimizing oxidation, it can also be carried out in the presence of an inert gas such as nitrogen. Also, the apparatus is not particularly limited, but considering the operation under nitrogen where oxidation degradation is less likely to occur and in a sealed state, it can also be carried out in a pressure-resistant container.

[0042] There is no particular limitation on the method for removing the solid acid, but generally, it is removed by vacuum filtration or pressure filtration. At this time, it is desirable to pre-heat the filter to about the processing temperature in order to prevent the precipitation of crystals due to the temperature drop during filtration.

[0043] Regarding the processing step after removing the solid acid, although this is not particularly limited, typically, a solution containing a polyethylene glycol compound is cooled, or hydrocarbons such as hexane and cyclohexane, higher alcohols such as isopropanol, and ethers such as diethyl ether and methyl tert-butyl ether are added as poor solvents to crystallize the polyethylene glycol compound, which can be isolated by filtration and then dried. Also, it is also possible to remove the solvent by desolvation and isolate the polyethylene glycol compound by drying and solidifying it. Also, if the organic solvent used does not inhibit the subsequent reaction, it is also possible to directly use the solution containing the polyethylene glycol compound in the next alkyl etherification reaction without these crystallization or desolvation operations. Also, prior to this reaction operation, if strict control of the water content is required, additionally, the solution containing the polyethylene glycol compound can typically be dehydrated using a dehydrating agent such as magnesium sulfate or sodium sulfate, or by azeotroping the solvent.

[0044] The compound of formula [1] thus obtained is a branched polyethylene glycol compound substantially free of vinyl ether groups. Since the compound of formula [1] is substantially free of vinyl ether groups, a high-purity polyethylene glycol compound with a low content of bifunctional polyethylene glycol compound can be obtained in subsequent steps. When the vinyl ether group content in the polyethylene glycol compound is high, it leads to an increase in the bifunctional polyethylene glycol compound in subsequent steps, which may cause dimerization of the drug when the drug is modified, posing a problem.

Example

[0045] Hereinafter, the present invention will be described more specifically based on examples. In the examples, the quantification of the vinyl ether content in the compounds in the examples was 1 performed using 1H-NMR. TOF-MS was used for measuring the molecular weight of the polyethylene glycol compound.

[0046] <Quantification method for vinyl ether group content> 1 In 1H-NMR analysis, JNM-ECP400 manufactured by JEOL DATUM Co., Ltd. was used, and deuterated chloroform was used as the deuterated solvent. When the integral value of the benzylic proton (4.5 ppm, q, 2H) of the polyethylene glycol compound was set to 2, the integral value × 100 of the peak of the vinyl ether group (6.5 ppm, q) was defined as the vinyl ether group content (%).

[0047] <Analysis method of TOF-MS> TOF-MS (Bruker, autoflexIII) was used for molecular weight measurement, and dithranol was used as the matrix and sodium trifluoroacetate was used as the salt for the measurement. Analysis was performed using FlexAnalysis, and molecular weight distribution analysis was performed using Polytools. The obtained centroid value was described as the molecular weight value.

[0048] (Example 1-1) Into a 5 L autoclave, 18.2 g (0.1 mol) of 3-benzyloxy-1,2-propanediol, 87 g of dehydrated toluene, and 4 g (18.2 mmol) of a 28% sodium methoxide methanol solution were charged and dissolved at room temperature. After adding 87 g of dehydrated toluene, alcoholization was carried out while performing methanol / toluene removal at 60 °C under reduced pressure. After alcoholization, 174 g of dehydrated toluene was added, and then the system was purged with nitrogen and heated. Ethylene oxide (1982 g, 45.0 mol) was added at 80 to 120 °C under a pressure of 1 MPa or less, and then the reaction was continued for another 1 hour. Approximately 1000 g of the resulting reaction product was withdrawn, ethylene oxide (2000 g, 45.5 mol) was added at 80 to 130 °C under a pressure of 1 MPa or less, and then the reaction was continued for another 1 hour. The entire content was withdrawn, the pH was adjusted to 7.5 with an 85% phosphoric acid aqueous solution, and 0.75 g of BHT (dibutylhydroxytoluene) was added to obtain the compound represented by formula (iii). TOF-MS analysis value (molecular weight centroid value): 58,663 As a result of NMR analysis, the vinyl ether group content in the compound represented by formula [iii] was 13%.

[0049]

Chemical formula

[0050] (Example 1-2) Into a 10 L four-necked flask equipped with a mechanical stirrer, thermometer, and nitrogen inlet tube, 450 g of polyethylene glycol represented by formula (iii) (molecular weight: 60,000, vinyl ether content: 13%) and 3600 g of toluene were charged and dissolved at 55 °C using a mantle heater. 180 g of Kyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.) dispersed in 900 g of toluene was added thereto. After stirring at 55 °C for 2 hours under nitrogen conditions, filtration was performed and the filtrate was collected. Hexane was added to the filtrate, and the precipitated crystals were collected by filtration and dried under vacuum. As a result of NMR analysis, the vinyl ether group content in the polyethylene glycol compound represented by formula [iii] was N.D.

[0051] (Comparative Example 1-1, Comparative Example 1-2, and Comparative Example 1-3) In the method of Example 1-2, Zeolite 700, which is aluminum silicate, was replaced with Zeolite 200, which is an amphoteric oxide (manufactured by Kyowa Chemical Industry Co., Ltd.: Al 2 O 3 ), Zeolite 300, which exhibits solid basicity (manufactured by Kyowa Chemical Industry Co., Ltd.: 2.5MgO·Al 2 O 3 0.7CO 3 ·nH 2 O), and Zeolite 1000 (manufactured by Kyowa Chemical Industry Co., Ltd.: Mg 4.5 Al 2 (OH) 13 (CO 3 )·3.5H 2 O), and the same operation was performed. The results are shown in Table 1.

[0052]

Table 1

[0053] As described above, when it is not a solid acid such as aluminum silicate, there is no effect of reducing the vinyl ether group.

[0054] (Comparative Example 2) Into a 1 L four-necked flask equipped with a mechanical stirrer, a thermometer, and a nitrogen blowing tube, 30 g of the branched polyethylene glycol represented by the formula (iii) obtained in Example 1-1 (molecular weight: 60,000, vinyl ether content: 13%) and 300 g of toluene were charged and dissolved at 55 °C using a mantle heater. After adding 30 mg of BHT to the treatment solution, it was heated to reflux at 120 °C to remove water by azeotropy. After cooling to room temperature, 0.13 g (1.3 mmol) of triethylamine and 0.12 g (1.1 mmol) of methanesulfonyl chloride were added and reacted at 40 °C for 3 hours. Next, 0.85 g (4.4 mmol) of a 28% sodium methoxide methanol solution was added and reacted at 40 °C for 3 hours. After the reaction, the reaction solution was kept at 40 °C and the pressure was reduced to remove the methanol / toluene mixed solution, followed by filtration, and the filtrate was collected. After adding 30 mg of BHT to the treatment solution, it was heated to reflux at 120 °C to remove water by azeotropy.

[0055] After cooling to room temperature, 0.13 g (1.3 mmol) of triethylamine and 0.12 g (1.1 mmol) of methanesulfonyl chloride were added and reacted at 40 °C for 3 hours. Next, 0.85 g (4.4 mmol) of a 28% sodium methoxide methanol solution was added and reacted at 40 °C for 3 hours. After the reaction, the reaction solution was kept at 40 °C and the pressure was reduced to remove the methanol / toluene mixed solution, followed by filtration, and the filtrate was collected. The solution was washed twice with 90 g of 25% brine, then concentrated, dehydrated with magnesium sulfate, and crystallized with hexane. The precipitated crystals were collected by filtration and dried to obtain 26 g of the methoxylated product of the formula [iv] (yield 85%). As a result of NMR analysis, the vinyl ether group content in the methoxylated product represented by the formula [iv] did not change and was 13%.

Chemical formula

[0056] From the above results, when the solid acid treatment was not carried out, the vinyl ether group remained without disappearing even after the methoxylation step. When the vinyl ether group remains, it causes an increase in the bifunctional polyethylene glycol compound in the subsequent steps, which may cause dimerization of the drug when the drug is modified, and may become a problem.

[0057] (Example 2-1) 0.73 kg of 2,2-bis{2-(benzyloxy)ethoxymethyl}-1,3-propanediol , 72.5 g of a 28% sodium methoxide methanol solution, and 45 kg of dehydrated toluene were charged into a 100 L reaction kettle, and the system was purged with nitrogen. After heating to 50 °C, the pressure was gradually reduced while maintaining the temperature, and about 9 kg of methanol and toluene were distilled off while blowing nitrogen. After continuing the distillation for 1 hour, the system was purged with nitrogen again, heated to 100 °C, and 8.5 kg of ethylene oxide was added at a pressure of 100 - 130 °C and 1 MPa or less, and then the reaction was continued for another 3 hours. After withdrawing 30 kg from the kettle, about 15 kg of the remaining reaction solution in the kettle was heated to 120 °C , and 9.0 kg of ethylene oxide was injected at a pressure of 100 - 130 °C and 1 MPa or less, and the reaction was continued for another 4 hours. After withdrawing 12 kg from the kettle, about 12 kg of the remaining reaction solution in the kettle was heated to 120 °C , and 6.2 kg of ethylene oxide was injected at a pressure of 100 - 130 °C and 1 MPa or less, and the reaction was continued for another 8 hours. The entire content was withdrawn, and the pH was adjusted to 7.5 with an 85% phosphoric acid aqueous solution to obtain the following compound (v). TOF-MS analysis value (molecular weight centroid value): 40,929

[0058] [Chemical formula]

[0059] (Example 2-2) A 5 L four-necked flask equipped with a mechanical stirrer, a thermometer, and a nitrogen injection tube was charged with 250 g of polyethylene glycol (molecular weight: 40,000, vinyl ether content: 7%) represented by formula (v) and 2250 g of toluene, and dissolved at 55 °C using a mantle heater. To this was added 100 g of Kyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.) dispersed in 250 g of toluene. After stirring at 55 °C for 2 hours under nitrogen conditions, filtration was performed and the filtrate was collected. Hexane was added to the filtrate, and the precipitated crystals were collected by filtration and dried under vacuum. As a result of NMR analysis, the vinyl ether group content in the polyethylene glycol compound represented by formula (v) was N.D.

[0060] (Example 3-1) 3.4 g of potassium hydroxide was added to a 100 ml beaker containing 23.7 g of methanol and 6.8 g of water and dissolved at room temperature. After dissolution, the prepared potassium hydroxide solution and 18.0 g (0.07 mol) of 1-benzylxylitol were added to a 5 L autoclave. After stirring at room temperature for 15 minutes, 180 g of toluene was added, and the mixture was stirred at 100 - 110 °C while blowing nitrogen to remove water and methanol by toluene azeotropy. The inside of the 5 L autoclave system was purged with nitrogen, heated to 100 °C, and 122 g (2.7 mol) of ethylene oxide was added at a pressure of 80 - 120 °C and 1 MPa or less, and then the reaction was continued for another 1 hour. Toluene in the 5 L autoclave was removed under reduced pressure, heated to 100 °C, and 2662 g (60.5 mol) of ethylene oxide was added at a pressure of 80 - 130 °C and 1 MPa or less, and then the reaction was continued for another 1 hour. The entire amount of the content was taken out, and the pH was adjusted to 7.5 with an 85% aqueous phosphoric acid solution to obtain the following compound (vi). TOF-MS analysis (molecular weight centroid value): 43,440 As a result of NMR analysis, the vinyl ether group content in the methoxylated product represented by formula (vi) was 7%.

[0061] [Chemical formula]

[0062] (Example 3-2) In a 10 L four-necked flask equipped with a mechanical stirrer, a thermometer, and a nitrogen blowing tube, 300 g of polyethylene glycol represented by formula (vi) (molecular weight: 40,000, vinyl ether content: 7%) and 2700 g of toluene were charged and dissolved at 55 °C using a mantle heater. To this, 120 g of Kyoward 700 (manufactured by Kyowa Chemical Industry Co., Ltd.) dispersed in 600 g of toluene was added. After stirring at 55 °C for 2 hours under nitrogen conditions, filtration was performed and the filtrate was collected. Hexane was added to the filtrate, and the precipitated crystals were collected by filtration and dried under vacuum. As a result of NMR analysis, the vinyl ether group content in the polyethylene glycol compound represented by formula (vi) was N.D.

Claims

【Claim 1】 An impurity represented by the following formula (ii) 【Chemical 1】 (In formula (ii), Z is a residue obtained by removing the active hydrogen groups from a compound having 3 to 5 active hydrogen groups, Y1 and Y2 each independently represent an alkylene group having 1 to 12 carbon atoms, A represents a protecting group for an active group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a thiol group, Polymer represents a polyethylene glycol chain, l is 0 or 1, m is 0 or 1, 1 ≤ a ≤ 3, and 0 ≤ c ≤ 3, 1 ≤ d ≤ 4, and 3 ≤ a + c + d ≤ 5 are satisfied.) A branched polyethylene glycol compound having a weight average molecular weight of 40,000 or more and represented by the following formula [1], which contains the above [Chemical Formula 2] (In formula [1], Z is a residue obtained by removing the active hydrogen groups from a compound having 3 to 5 active hydrogen groups, Y １ and Y ２ each independently represents an alkylene group having 1 to 12 carbon atoms, A represents a protecting group for an active group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and a thiol group, Polymer represents a polyethylene glycol chain, l is 0 or 1, m is 0 or 1, a and b are integers satisfying 1 ≤ a ≤ 3, 2 ≤ b ≤ 4, and 3 ≤ a + b ≤ 5.) In the presence of an aprotic organic solvent, at least one solid acid selected from the group consisting of magnesium silicate, aluminum silicate, and aluminum magnesium silicate, having a specific surface area of 50 to 250 m ２ / g is added to obtain a mixture, and the mixture is stirred to convert the vinyl ether group of the impurity into a hydroxyl group, and then the solid acid is separated. A method for purifying branched polyethylene glycol, characterized by this.

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