Method for purifying polyethylene glycol compound

Abstract

To provide a method for reducing a polyfunctional body served as an impurity to efficiently refine a polyethylene glycol compound having one amino group at a terminal with high purity by an industrially practical method.SOLUTION: A method for refining a polyethylene glycol compound comprises: a (A) step of dissolving the compound of the formula [1] in an organic solvent having a Hildebrand solubility parameter of 8-10(cal / cm3)1 / 2 to obtain a solution; and a (B) step of mixing 0.1-1 mass part of an adsorbent consisting of hydrotalcite having a specific surface area of 50-200 m2 / g to 1 mass part of the compound of the formula [1] with the solution to prepare slurry.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for purifying a polyethylene glycol compound having one amino group, which is preferably used for pharmaceutical applications. More specifically, the present invention relates to a high-molecular-weight activated polyethylene glycol for chemical modification applications in drug delivery systems, and a purification method for obtaining a high-purity polyethylene glycol compound having one amino group, which is used as a raw material thereof.

[0002] The present invention is particularly suitable for pharmaceutical applications including the modification of polypeptides, enzymes, antibodies, other low-molecular-weight drugs, nucleic acid compounds including genes and oligonucleic acids, nucleic acid drugs 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 polyethylene glycol compounds, the high hydration layer and steric repulsion effect of polyethylene glycol can suppress the capture of drugs by the reticuloendothelial system (RES) and excretion by the kidneys, and improve the blood retention of drugs and reduce antigenicity. Among them, a polyethylene glycol compound having an amino group at the terminal is not only a modifier for drugs having a carboxyl group itself, but also a raw material for synthesizing other activated polyethylene glycol compounds such as terminal maleimide, azide, and iodoacetamide compounds by reacting with low-molecular-weight activating reagents, and also a raw material for block copolymers for forming polymer micelles by reacting with α-amino acid-N-carboxy anhydrides. Therefore, it is a particularly important material.

[0004] For activated polyethylene glycol compounds intended for such pharmaceutical uses, those with few impurities are required from the viewpoints of the performance and safety of drugs produced by modifying them. Currently, polyethylene glycol compounds having one amino group at the terminal have been developed with various skeletons, and the impurities by-produced depending on the production method are various. However, when a polyethylene glycol compound having a plurality of amino groups is contained as an impurity, it is preferable to reduce it as much as possible because it causes an increase in the amount of the drug when the drug is modified. However, both the polyethylene glycol compound having one amino group and the polyethylene glycol compound having a plurality of amino groups as impurities are polymers and have amino groups that are ionic, so their physicochemical properties are similar, and separation and purification are difficult with general techniques.

[0005] Patent Document 1 describes a method for purifying a polyethylene glycol compound having one amino group by column chromatography using an ion exchange resin. In this method, by continuously changing the composition of the eluent, it is possible to separate and purify the polyethylene glycol compound according to the difference in the number of amino groups. However, such a purification method using an ion exchange resin is a method that utilizes the interaction with the solid surface and the adsorption phenomenon in principle, so a purification treatment using a large amount of resin is required under dilute solution conditions. The concentration of the polyethylene glycol compound during the process must be in a dilution condition of about 1-2% in order to suppress a decrease in separation ability, so it does not sufficiently satisfy industrial productivity. In addition, finally, a large amount of ion exchange resin becomes waste, and it is a purification method that also has problems in industrial use.

[0006] In Patent Document 2, a method for purifying a polyethylene glycol compound having one amino group is described, which involves dissolving the compound in a strongly acidic aqueous solution with a pH of 1 to 3 to ionize the terminal amino group, and then extracting it within a specific temperature range using a specific mixed organic solvent. In this patent, the polyethylene glycol compound having an amino group with enhanced hydrophilicity due to ionization is partitioned into the aqueous layer, while the polyethylene glycol compound without an amino group is partitioned into the mixed organic layer, enabling selective separation and purification. However, this purification method separates polyethylene glycol compounds based on the presence or absence of amino groups. Thus, when both the target substance and impurities contain one or more amino groups, they cannot be separated based on the difference in the number of amino groups.

[0007] In Patent Documents 3 and 4, methods for purifying polyethylene glycol compounds by utilizing the interaction between a polyethylene glycol compound having a hydroxyl group and a carboxyl group and an adsorbent are described. When an appropriate adsorbent that interacts with these functional groups is used, the polyethylene glycol with more functional groups is preferentially adsorbed onto the adsorbent. Therefore, separation and purification can be achieved based on the presence or absence of functional groups and, in some cases, the number of functional groups. However, there is no description regarding selectively removing impurities based on the presence or absence and the number of amino groups.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0009] Thus, although a polyethylene glycol compound having one amino group at its terminal is an important material in pharmaceutical applications, it has not been obtained by an industrially easy manufacturing method and has many problems.

[0010] An object of the present invention is to reduce polyfunctional impurities from the main component and to purify a polyethylene glycol compound having one amino group at its terminal with high efficiency and good purity by an industrially feasible method.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventors have found that an adsorbent composed of hydrotalcite has an effect of selectively adsorbing and removing a polyethylene glycol compound having a plurality of basic amino groups, and have completed the present invention.

[0012] That is, the present invention is as follows. The following step (A) 、 (B) step and step (C) A method for purifying a polyethylene glycol compound represented by formula [1], characterized by having the following. (A) step: A step of obtaining a solution by dissolving the compound represented by the formula [1] in an organic solvent having a Hildebrand solubility parameter of 8 to 10 (cal / cm 3 ) 1 / 2 (B) step: A step of preparing a slurry by mixing 0.1 to 1 part by mass of an adsorbent composed of hydrotalcite having a specific surface area of 50 to 200 m / g with 1 part by mass of the compound of the formula [1] in the solution 2 (C) step: By removing the adsorbent from the slurry, a solution containing the compound represented by the formula [1] is obtained, and the organic solvent is removed from the solution after removing the adsorbent to isolate the compound represented by the formula [1].

Chemical formula

Advantages of the Invention

[0013] According to the present invention, by allowing an adsorbent composed of hydrotalcite to act on a polyethylene glycol compound having one amino group at the terminal, it is possible to selectively remove polyethylene glycol having a plurality of amino groups as impurities. Therefore, the production 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

[0014] [Fig. 1] The HPLC chromatogram of the raw material (before purification) of Example 1-1 is shown. [Fig. 2] The HPLC chromatogram after purification of Example 1-1 is shown.

Modes for Carrying Out the Invention

[0015] Details of the present invention are a method for purifying a polyethylene glycol compound having one amino group represented by the general formula [1] by a treatment step including the following operations.

[0016]

Chem.

[0017] Z is a residue obtained by removing active hydrogen groups from a compound (Z(GH)n: n = 2 to 5) having 2 to 5 active hydrogen groups (-GH). An active hydrogen group is a functional group having active hydrogen. Examples of the active hydrogen group include a hydroxyl group, a carboxyl group, an amino group, a secondary amino group, and a thiol group. When the active hydrogen group (GH) is a hydroxyl group or a carboxyl group, the residue Z is a deacidation group residue, and when the active hydrogen group is an amino group, a secondary amino group, or a thiol group, the residue Z is a dehydrogenation residue.

[0018] Specific examples of the compound (Z(GH)n: n = 2 to 5) having 2 to 5 active hydrogen groups (-GH) include polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylene glycol, isopropylene glycol, butylene glycol, tetramethylene glycol, trimethylolpropane, glycerin, diglycerin, triglycerin, pentaerythritol, and xylitol, or compounds such as lysine and glutamic acid, amino acids and peptides having an amino group, a carboxyl group, or a thiol group, or organic amines and organic carboxylic acids.

[0019] Y 1 is a linking group between the residue Z and A, and there is no particular limitation as long as it is a covalent bond. Y 1 and Y 2 each independently represent an ether bond, an amide bond, an ester bond, a urethane bond, a carbonate bond, a secondary amino group, a thioether bond, a disulfide bond, a thioester bond, or an alkylene group which may contain these. Preferred examples of the alkylene group portion include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a pentylene group, an isopentylene group, and a hexylene group, and these may be branched.

[0020] A represents an amino group. 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 the branching point.

[0021]

Chemical formula

[0022] The weight average molecular weight of the polyethylene glycol compound is not particularly limited, but is preferably 2,000 to 100,000, and more preferably 2,000 to 80,000. l = 0 or 1, m = 0 or 1, and a and b are integers satisfying 0 ≤ a ≤ 4, 0 ≤ b ≤ 4 and 1 ≤ a + b ≤ 4

[0023] Hereinafter, each step will be described in more detail. (Step (A)) is a step of obtaining a solution by dissolving the compound represented by formula [1] in an organic solvent having a Hildebrand solubility parameter of 8 to 10 (cal / cm 3 ) 1 / 2 is.

[0024] In step (A), the Hildebrand solubility parameter is 8 to 10 (cal / cm 3 ) 1 / 2An organic solvent is used. If the Hildebrand solubility parameter of this organic solvent is less than 8, the polyethylene glycol compound will not dissolve. If it exceeds 10, there is a risk of desorption and elution of metal components from the adsorbent, which is not preferable. The Hildebrand solubility parameter of this organic solvent is preferably 8.5 to 9.5, more preferably 8.5 to 9.0. This organic solvent is preferably an organic solvent selected from toluene, xylene, benzene, chloroform, and dichloromethane, more preferably toluene and chloroform, and even more preferably toluene.

[0025] In step (A), when the amount of the organic solvent relative to 1 part by mass of the compound of formula [1] is W and the weight average molecular weight of the compound represented by formula [1] is M, 2.0M×10 -4 +2.0 ≤ W ≤ 50 is preferably satisfied, and 2.0M×10 -4 +2.0 ≤ W ≤ 30 is more preferably satisfied.

[0026] Using the above organic solvent, the polyethylene glycol compound is dissolved. The charging order into the treatment container may be either the polyethylene glycol compound or the 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.

[0027] Step (B) is a step of preparing a slurry by mixing 0.1 to 1 part by mass of an adsorbent composed of hydrotalcite having a specific surface area of 50 to 200 m 2 / g into the solution per 1 part by mass of the compound of formula [1].

[0028] The adsorbent in step (B) is composed of at least one hydrotalcite selected from the group consisting of compounds having the following general formula. (M 2+ ) 1-x 1 (M 3+ ) x 1 (OH) 2 (An- ) x 1 / n·aH 2 O (wherein M 2+ represents a divalent metal ion, M 3+ represents a trivalent metal ion, A n- represents an n-valent anion, n represents the valence of the anion of A n- , x 1 and a each represent a range of 0 < x 1 < 0.5, 0 ≤ a < 1.) or x 2 (M 2+ )O·y(M 3+ ) 2 O 3 ·z(A n- )·b H 2 O (wherein M 2+ represents a divalent metal ion, M 3+ represents a trivalent metal ion, A n- represents an n-valent anion, n represents the valence of the anion of A n- , x 2 , y, z, b each represent a range of 0 < x 2 ≤ 10, 0 < y ≤ 10, 0 ≤ z ≤ 10, 0 ≤ b ≤ 20.)

[0029] M 2+ is preferably a divalent ion of Mg, Ca or Zn, M 3+ is preferably a trivalent ion of Al or Fe, A n- is preferably OH, ClO 4 , NO 3 , SO 4 , CO 3 , SiO 3 , HPO 4 , PO 4 or CH 3 COO. Among them, M 2+ is Mg, M 3+ is Al, A n- is CO3 A hydrotalcite is preferred. Particularly preferred is (Mg) 1-x 1 (Al) x 1 (OH) 2 (CO 3 ) x 1 / 2 ·aH 2 O (0.2 ≦ x 1 ≦ 0.4, 0.4 ≦ a ≦ 0.7), or x 2 MgO·yAl 2 O 3 ·z(CO 3 )·bH 2 O (1 ≦ x 2 ≦ 4, 0.5 ≦ y ≦ 3, 0 ≦ z ≦ 3, 0 ≦ b ≦ 10), and most preferably x 2 MgO·yAl 2 O 3 ·z(CO 3 )·bH 2 O (1 ≦ x 2 ≦ 5, 0.5 ≦ y ≦ 3, 0 ≦ z ≦ 3, 0 ≦ b ≦ 10). Specific examples include STABIACE HT-1 (Mg 0.67 Al 0.33 (OH) 2 (CO 3 ) 0.17 ·0.5H 2 O), STABIACE HT-P (Mg 0.69 Al 0.31 (OH) 2 (CO 3 ) 0.15 ·0.54H 2 O), Kyoward 300 (2.5MgO·Al 2 O 3 ·0.7CO 3 ·aH 2 O, 6 ≦ a ≦ 7), manufactured by Kyowa Chemical Industry Co., Ltd., Kyoward 500 (Mg 0.75 Al 0.25 (OH) 2 (CO 3 ) 0.13 ·aH 2 O, 0.50 ≦ a ≦ 0.63), Kyoward 1000 (Mg0.69 Al 0.31 (OH) 2 (CO 3 ) 0.15 ·aH 2 O, 0.46 ≦ a ≦ 0.62), etc. can be obtained from the market. Among them, Kyoward 300 is preferable. The above adsorbent may be used alone or in combination.

[0030] With respect to 1 part by mass of the compound represented by formula [1], the amount of the adsorbent is preferably in the range of 0.1 to 1.0 parts by mass times. If the amount of the adsorbent is less than 0.1 part by mass, a sufficient purification effect cannot be obtained. If the amount of the adsorbent is more than 1 part by mass, the polyethylene glycol compound remains in the filter cake when the slurry solution after treatment is filtered, and the yield decreases. More preferably, the amount of the adsorbent is 0.1 to 0.5 parts by mass.

[0031] As the treatment temperature in step (B), 25 to 60 °C is preferable. If it 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 preferable. A more preferable temperature range is 40 to 60 °C.

[0032] As the treatment time in step (B), the range of 0.1 to 24 hours is preferable. 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 in consideration of the operation under nitrogen where oxidation deterioration is unlikely to occur and in a sealed state, it can also be carried out in a pressure-resistant container.

[0033] Recovery step: A step of recovering the polyethylene glycol compound from the slurry This step is to remove the adsorbent and the solvent from the adsorption treatment solution (slurry) in the above step (B) to isolate the target polyethylene glycol compound. The method for removing the adsorbent is not particularly limited, but generally, it is removed by vacuum filtration or pressure filtration. At this time, it is desirable to pre-heat the filter to the same temperature as the treatment temperature in step (B) in order to prevent the precipitation of crystals due to the temperature drop during filtration. After filtration, the target polyethylene glycol compound is contained in the filtrate. Regarding the treatment step after the removal of the adsorbent, although it is not particularly limited, typically, the solution containing the 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 drying. It is also possible to remove the solvent by desolvation and isolate the polyethylene glycol compound by drying and solidifying.

Example

[0034] Hereinafter, the present invention will be described more specifically based on examples. For the quantification of the polyfunctional PEG content in the compounds in the examples, after binding a fluorescent substance to the amino group by derivatization using the following analytical method A or B, it was measured by RP-HPLC.

[0035] <Derivatization> Analytical method A: 100 mg of the sample, 11.3 mg of 6-[[7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazol-4-yl]amino]hexanoic acid succinimidyl, 4 mL of toluene, and 1 mL of acetonitrile were charged into a 9 mL screw tube and dissolved at 25 °C. 5.5 μL of N-methylmorpholine was added thereto, and the mixture was stirred at 25 °C for 1 hour. After the reaction, it was diluted with ethyl acetate and crystallized with hexane. The precipitated crystals were filtered off and vacuum dried to recover the sample for analysis.

[0036] Analytical method B: Add 1.5 mL of tetrahydrofuran to 300 mg of 3,5-dinitrobenzoyl chloride (DNB) and dissolve to prepare a DNB solution. Charge 10 mg of the sample and 60 μL of tetrahydrofuran into a 1 mL screw tube and dissolve at 25°C. Add 4 μL of pyridine and 36 μL of the DNB solution thereto, and conduct derivatization at 40°C for 1 hour. After completion of the derivatization, dilute with 0.4 mL of a 0.1% aqueous trifluoroacetic acid solution and filter to obtain a sample for analysis.

[0037] <RP-HPLC Analysis Method> Analysis Method A: Use an alliance (Waters) as the HPLC system and conduct measurement under the following conditions. Mobile Phase Mobile Phase D: 1 mmol / L hydrochloric acid / acetonitrile (2 / 1) Mobile Phase A: 1 mmol / L hydrochloric acid / acetonitrile (1 / 1) Gradient Conditions 0 min Mobile Phase D:Mobile Phase A = 100:0 22 min Mobile Phase D:Mobile Phase A = 0:100 24 min Mobile Phase D:Mobile Phase A = 0:100 26 min Mobile Phase D:Mobile Phase A = 100:0 35 min Mobile Phase D:Mobile Phase A = 100:0 Flow Rate: 1 ml / min Column: apHera C4, φ4.6 mm, 15 cm (SUPELCO) Column Temperature: 33°C (when the molecular weight is 20,000) or 25°C (when the molecular weight is 40,000) Detector: Fluorescence Detector (ex384 nm, em520 nm) Sample Concentration: 1 mg / mL Injection Volume: 50 μl (when the molecular weight is 20,000) or 20 μl (when the molecular weight is 40,000)

[0038] Analysis Method B: Use a Thermo Fisher Ultimate 3000 as the HPLC system. Mobile Phase: Mobile Phase A: 0.1% Aqueous trifluoroacetic acid solution Mobile phase B: 0.1% Trifluoroacetic acid acetonitrile solution Gradient conditions At 0 min, mobile phase A:mobile phase B = 70:30 At 30 min, mobile phase A:mobile phase B = 50:50 At 30.1 min, mobile phase A:mobile phase B = 5:95 At 35 min, mobile phase A:mobile phase B = 5:95 Flow rate: 0.6 min Column: Sun Shel HFC 18-30, φ3 mm, 15 cm Column temperature: 50 °C Detector: UV detector (220 nm) Sample concentration: 20 mg / mL Injection volume: 5 μL

[0039] For both analytical methods A and B, in the HPLC measurement values, the main peak derived from the target monofunctional group and the derivatized polyfunctional PEG peak were vertically divided with respect to the baseline, and the polyfunctional PEG content was calculated from the area values of each obtained peak using the following formula.

Number

[0040] Analytical method A detects the impurities represented by the following formula (ii), and analytical method B detects the impurities represented by the following formula (iii).

[0041]

Chemical formula

[0042]

Chemical formula

[0043] (In formulas (ii) and (iii), Z is the residue obtained by removing the active hydrogen groups from a compound having 2 to 5 active hydrogen groups, A is an amino group, Y 1 and Y 2 is, independently of each other, an ether bond, an amide bond, an ester bond, a urethane bond, a carbonate bond, a secondary amino group, a thioether bond, a disulfide bond, a thioester bond or an alkylene group containing these, Polymer represents a polyethylene glycol chain, X is a hydrocarbon group having 1 to 7 carbon atoms, an acetal group having 3 to 9 carbon atoms, a hydroxyl group, a protecting group for a hydroxyl group, a carboxyl group, a protecting group for a carboxyl group, a thiol group, a protecting group for a thiol group, a cyano group or an alkylene group containing these, l and m are l = 1 or 0, m = 1 or 0, respectively, a' and b are integers satisfying 1 ≤ a' ≤ 4, 0 ≤ b ≤ 4 and 1 ≤ a' + b ≤ 4)

[0044] (Example 1-1) 100 g of a branched polyethylene glycol compound having two polyethylene glycol chains in the glycerin skeleton shown in the following formula (iv) (weight average molecular weight: 20,000, bifunctional PEG content: 1.3%, trifunctional PEG content: not detected) and 1150 g of toluene were charged into a 2 L four-necked flask, equipped with a three-one motor, a condenser, and a nitrogen blowing tube, and dissolved at 50 °C using a water bath. 30 g of Kyoward 300 (Kyowa Chemical Industry) was added thereto, and stirring was carried out at 50 °C for 1 hour. Thereafter, the filtrate was recovered by filtration, and after concentration, hexane was added to precipitate crystals. The precipitated crystals were filtered off and vacuum dried to recover the crystals (yield 91%). As a result of RP-HPLC analysis by Analytical Method A, the bifunctional PEG content was 0.1%.

[0045] [Chemical formula]

[0046] (Examples 1-2 to 1-3) Using the same raw materials as in Example 1-1 and in the same manner, Keyword 300 was changed to the adsorbents shown in the following table and the operation was carried out. The results are shown below. In the following table, the keyword is abbreviated as "KW".

[0047]

Table 1

[0048] From the above results, all of Keyword 300, Keyword 500, and Keyword 1000, which are hydrotalcites, had a bifunctional PEG removal effect. Among them, 300 had the highest effect and also had a good yield.

[0049] (Comparative Examples 1-1 to 1-3) Using the same branched polyethylene glycol compound as in Example 1-1 (weight average molecular weight: 20,000, bifunctional PEG content: 1.4%, trifunctional PEG content: not detected) and in the same manner, Keyword 300 was changed to the inorganic salts shown in the following table and the operation was carried out. The results are shown below.

[0050]

Table 2

[0051] From the above results, Keyword 700, which is aluminum silicate, had an effect of removing bifunctional PEG because it is an acidic adsorbent, but the target product was also adsorbed together, so the yield decreased significantly. On the other hand, inorganic oxides such as alumina and inorganic salts such as magnesium sulfate had no purification effect.

[0052] (Examples 1-4 to 1-5) Using the same raw materials as in Example 1-1 and in the same manner, Keyword 300 was changed to the amounts shown in the following table and the operation was carried out. The results are shown below.

[0053]

Table 3

[0054] From the above results, although the efficiency slightly decreased, it was found that even 0.1 mass times of the bifunctional PEG had the effect of removing it. Also, there was almost no decrease in the yield between 0.1 and 0.4 mass times.

[0055] (Example 2) 10 g of a branched polyethylene glycol compound having two polyethylene glycol chains in the glycerin skeleton shown in formula (iv) (molecular weight: 40,000, bifunctional PEG content: 1.1%, trifunctional PEG content: not detected) and 180 g of toluene were charged into a 500 mL four-necked flask, equipped with a three-one motor, a condenser tube, and a nitrogen blowing tube, and dissolved at 50 °C using a water bath. 3 g of KYOWARD 300 (Kyowa Chemical Industry) was added thereto, and stirring was carried out at 50 °C for 1 hour. Then, the filtrate was collected by filtration, concentrated, and hexane was added to precipitate crystals. The precipitated crystals were filtered off and vacuum dried to recover the crystals (yield 86%). As a result of RP-HPLC analysis by analytical method A, the bifunctional PEG content was less than 0.1% (0.03%).

[0056] (Example 3) 20 g of α-aminopropyl-, ω-methoxy-polyethylene glycol (molecular weight: 20,000, bifunctional PEG content: 2.8%) shown in the following formula (v) and 360 g of toluene were charged into a 1 L four-necked flask, equipped with a three-one motor, a condenser tube, and a nitrogen blowing tube, and dissolved at 50 °C using a water bath. 6 g of KYOWARD 300 was added thereto, and stirring was carried out at 50 °C for 1 hour. Then, the filtrate was collected by filtration, concentrated, and hexane was added to precipitate crystals. The precipitated crystals were filtered off and vacuum dried to recover the crystals (yield 82%). As a result of RP-HPLC analysis by analytical method A, the bifunctional PEG content of the sample was 0.5%.

[0057] [Chemical formula]

[0058] (Example 4) 10 g of α-aminopropyl-, ω-methoxy-polyethylene glycol (molecular weight: 2,000, bifunctional PEG content: 1.8%) shown in formula (v) and 45 g of toluene were charged into a 300 mL four-necked flask, equipped with a three-one motor, a condenser, and a nitrogen blowing tube, and dissolved at 40 °C under nitrogen using a water bath. 3 g of Kyoward 300 was added thereto, and stirring was carried out at 40 °C for 30 minutes. Then, the filtrate was collected by filtration, and after concentration, hexane was added to precipitate crystals. The precipitated crystals were filtered off and vacuum dried to recover the crystals (yield 84%). As a result of RP-HPLC analysis by Analytical Method B, the bifunctional PEG content of the sample was 0.9%.

Claims

【Claim 1】 A method for purifying a polyethylene glycol compound represented by formula [1], characterized by having the following steps (A), (B), and (C). Step (A): Dissolving the compound represented by the formula [1] in an organic solvent having a Hildebrand solubility parameter of 8 to 10 (cal / cm ３ ) １／２ to obtain a solution Step (B): By mixing 0.1 to 1 part by mass of an adsorbent composed of hydrotalcite having a specific surface area of 50 to 200 m ２ / g into 1 part by mass of the compound of the formula [1] in the solution, a slurry is prepared Step (C): By removing the adsorbent from the slurry, a solution containing the compound represented by formula [1] is obtained, and the organic solvent is removed from the solution after removing the adsorbent to isolate the compound represented by formula [1]. 【Chemical 1】 (In formula [1], Z is a residue obtained by removing the active hydrogen groups from a compound having 2 to 5 active hydrogen groups, A is an amino group, Y １ and Y ２ each independently represents an ether bond, an amide bond, an ester bond, a urethane bond, a carbonate bond, a secondary amino group, a thioether bond, a disulfide bond, a thioester bond, or an alkylene group containing these, Polymer represents a polyethylene glycol chain, X is a hydrocarbon group having 1 to 7 carbon atoms, an acetal group having 3 to 9 carbon atoms, a hydroxyl group, a protecting group for a hydroxyl group, a carboxyl group, a protecting group for a carboxyl group, a thiol group, a protecting group for a thiol group, a cyano group, or an alkylene group containing these, l and m are each l = 1 or 0, m = 1 or 0, a and b are integers satisfying 0 ≦ a ≦ 4, 0 ≦ b ≦ 4, and 1 ≦ a + b ≦ 4)

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