Process for preparing and separating monodisperse polyethylene glycol

Abstract

A process for preparing and separating a monodisperse polyethylene glycol, including: dissolving a starting material of polyethylene glycol into an organic solvent for reaction with a compound represented by general formula I under catalytic action of an alkaline substance, to prepare a mixture of derivatives of polyethylene glycol having different polarities; separating the mixture of derivatives of polyethylene glycol by means of silica gel column chromatography, to obtain a monodisperse derivative of polyethylene glycol; and hydrolyzing the derivative of polyethylene glycol to obtain a monodisperse polyethylene glycol. The starting material is industrially prepared polyethylene glycol with a wide source and low cost, which provides a guarantee for popularization and application of a monodisperse polyethylene glycol product.

Claims

1. A process for preparing and separating a monodisperse polyethylene glycol, comprising: reacting a starting material of polyethylene glycol dissolved into an organic solvent with a compound represented by general formula I under catalytic action of an alkaline substance, to prepare a mixture of derivatives of polyethylene glycol having different polarities; separating the mixture of the derivatives of polyethylene glycol by means of silica gel column chromatography, to obtain a monodisperse derivative of polyethylene glycol; and hydrolyzing the monodisperse derivative of polyethylene glycol to obtain a monodisperse polyethylene glycol, wherein, general formula I is as follows:
RB, where: R is a C.sub.1-C.sub.4 alkyl or an aryl; and B is selected from the group consisting of a chloride ion, a bromide ion, an iodide ion, sulfydryl, sulfonyl, an isocyanate group, and an isocyanurate group.

2. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein the starting material of polyethylene glycol has general formula of: ##STR00009## wherein: n=3 to 50, and a polydispersity index thereof is greater than 1.1; and the derivatives of polyethylene glycol with different polarities have general formula of: ##STR00010## wherein: n=3 to 50.

3. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein the monodisperse polyethylene glycol has a polydispersity index of 1 to 1.03.

4. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein the C.sub.1-C.sub.4 alkyl is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, 1-butyl, 2-butyl, and isobutyl; and the aryl is selected from the group consisting of phenyl, 2-methylphenyl, 4-methylphenyl, benzyl, 2-methylbenzyl, 4-methylbenzyl, 4-tosyl, and triphenylmethyl.

5. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein a molar ratio of the starting material of polyethylene glycol to the compound represented by general formula I is 2:1 to 100:1, and a molar ratio of the starting material of polyethylene glycol to the alkaline substance is 1:1 to 20:1.

6. The process for preparing and separating a monodisperse polyethylene glycol according to claim 5, wherein the molar ratio of the starting material of polyethylene glycol to the compound represented by general formula I is 4:1 to 20:1, and the molar ratio of the starting material of polyethylene glycol to the alkaline substance is 2:1 to 7:1.

7. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein a reaction temperature for the reaction of the starting material of polyethylene glycol with the compound represented by general formula I is 20 C. to 150 C., and a reaction duration thereof is 3 h to 72 h.

8. The process for preparing and separating a monodisperse polyethylene glycol according to claim 7, wherein the reaction temperature for the reaction of the starting material of polyethylene glycol with the compound represented by general formula I is 0 C. to 60 C., the reaction duration is 8 h to 72 h.

9. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein the organic solvent is at least one selected from the group consisting of dichloromethane, trichloromethane, benzene, toluene, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran and 1,4-dioxane; the alkaline substance is at least one selected from the group consisting of an alkali metal, an alkaline-earth metal, and a corresponding oxide, hydroxide, and hydride thereof; and the eluent during the process of silica gel column chromatography is a mixture of two selected from the group consisting of formamide, acetonitrile, methanol, ethanol, propyl alcohol, acetone, dioxane, tetrahydrofuran, methyl ethyl ketone, n-butanol, ethyl acetate, diethyl ether, isopropyl ether, dichloromethane, chloroform, benzene, tetrachloromethane, carbon disulfide, cyclohexane, n-hexane and petroleum ether.

10. The process for preparing and separating a monodisperse polyethylene glycol according to claim 9, wherein the organic solvent is tetrahydrofuran or 1,4-dioxane; the alkaline substance is sodium metal, sodium hydroxide or sodium hydride; and the eluent during the process of silica gel column chromatography is a mixed solvent of ethyl acetate and petroleum ether, or a mixed solvent of dichloromethane and methanol.

11. The process for preparing and separating a monodisperse polyethylene glycol according to claim 1, wherein the monodisperse polyethylene glycol has a polydispersity index of 1 to 1.005.

12. A process for obtaining a monodisperse polyethylene glycol, comprising: reacting a starting material of polyethylene glycol having a polydispersity index greater than 1.1 that is dissolved into an organic solvent with a compound represented by general formula I under catalytic action of an alkaline substance, to prepare a mixture of derivatives of polyethylene glycol having different polarities; separating the mixture of the derivatives of polyethylene glycol by means of silica gel column chromatography, to obtain a monodisperse derivative of polyethylene glycol; and hydrolyzing the monodisperse derivative of polyethylene glycol to obtain a monodisperse polyethylene glycol having a polydispersity index of 1 to 1.03, wherein, general formula I is as follows:
RB, where: R is a C.sub.1-C.sub.4 alkyl or an aryl; and B is selected from the group consisting of a chloride ion, a bromide ion, an iodide ion, sulfydryl, sulfonyl, an isocyanate group, and an isocyanurate group.

13. The process for obtaining a monodisperse polyethylene glycol according to claim 12, wherein the monodisperse polyethylene glycol has a polydispersity index of 1 to 1.005.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a high performance liquid chromatography (HPLC) spectrum of the content of octaethylene glycol (n=7); and

(2) FIG. 2 is a nuclear magnetic resonance spectrum of octaethylene glycol (n=7).

DETAILED DESCRIPTION

(3) The following describes the present invention with reference to specific embodiments, but the present invention is not limited thereto.

Embodiment 1

(4) 40 g (0.1 mol) of polyethylene glycol PEG-400 was taken as a starting material, which has a molecular weight distribution range of 380 to 420 and a distribution index of 1.15. The polyethylene glycol was dissolved in 1,000 ml of 1,4-dioxane and cooled to 0 C. Then, to the resulting solution, 2 g (0.025 mol) of 50% (mass percentage content, the same below) sodium hydroxide solution was added dropwise and further stirred for 2 h. 2.3 g (0.025 mol) of isobutyl chloride was then added for reaction at a temperature of 0 C. over 24 h. 300 ml of saturated ammonium chloride solution was added to the reaction liquid and then stirred for stratification. An organic phase was washed with saturated aqueous solution of sodium chloride to neutral, and after the solvent was removed by means of vacuum concentration, a mixed sample of 8.0 g of polyethylene glycol mono(isobutyl) ester was obtained. To the above sample, 12 g of silica gel and 50 ml of ethyl acetate were added, evenly dispersed and dried to prepare a silica gel sample. 200 g of silica gel was added into a glass chromatography column with a diameter of 80 mm, and vibrated to become dense. Then, the above silica gel sample and a small amount of anhydrous sodium sulfate were added into the glass chromatography column, to prevent surface disturbance of the silica gel sample. After a silica gel column for chromatography was formed, a mixed solvent (P/E=1:1) of ethyl acetate and petroleum ether with a volume ratio of 1:1 was slowly added as an eluent continuously. Samples of different components were collected according to different polarities, and after the eluent was removed, derivatives of polyethylene glycol with a pure component were obtained. Then, 100 ml of 5% sodium hydroxide solution was separately added into the derivatives of polyethylene glycol, stirred at 50 C. and hydrolyzed for 8 h. After being cooled, the derivatives of polyethylene glycol were separately extracted with 100 ml of dichloromethane for 3 times. Then organic phases were combined and dichloromethane was removed by means of vacuum concentration, to obtain products of 1.5 g of octaethylene glycol

(5) ##STR00003##
with a polydispersity index of 1.001, a structure determined by nuclear magnetic resonance spectroscopy (as shown in FIG. 2), and a purity detected by high performance liquid chromatography (HPLC) (as shown in FIG. 1) under HPLC detection conditions of a C18 chromatographic column, an evaporative light-scattering detector, and a mobile phase of acetonitrile and water (30:70); and 3.4 g of nonaethylene glycol

(6) ##STR00004##
with a polydispersity index of 1.000.

Embodiment 2

(7) 50 g (0.25 mol) of polyethylene glycol PEG-200 was taken as a starting material and dissolved in 1,000 ml of tetrahydrofuran. Then, to the resulting solution, 10 g (0.125 mol) of 50% sodium hydroxide solution was added dropwise and further stirred for 2 h. 7 g (0.025 mol) of triphenylmethyl chloride was then added for reaction at a temperature of 20 C. over 12 h. 300 ml of saturated ammonium chloride solution was added into the reaction liquid and stirred for stratification. The organic phase was washed with saturated aqueous solution of sodium chloride to neutral. After the solvent was removed by means of vacuum concentration, a mixed sample of 9.5 g of polyethylene glycol mono(triphenylmethyl) ester and polyethylene glycol bis(triphenylmethyl) ester was obtained. To the above sample, 12 g of silica gel and 50 ml of ethyl acetate were added, evenly dispersed and dried to prepare a silica gel sample. 200 g of silica gel was added into a glass chromatography column with a diameter of 80 mm, and vibrated to become dense. Then, the above silica gel sample and a small amount of anhydrous sodium sulfate were added into the glass chromatography column, to prevent surface disturbance of the silica gel sample. After a silica gel column for chromatography was formed, an eluent (P/E=1:1) was slowly added continuously. Samples of different components were collected according to different polarities, and after the eluent was removed, derivatives of polyethylene glycol with a pure component were obtained. Then, 100 ml of 5% hydrochloric acid solution was separately added into the derivatives of polyethylene glycol, stirred at 50 C. and hydrolyzed for 8 h. After being cooled, the derivatives of polyethylene glycol were separately extracted with 100 ml of dichloromethane for 3 times. Then organic phases were combined and dichloromethane was removed by means of vacuum concentration, to obtain products of 3.7 g of tetraethylene glycol

(8) ##STR00005##
with a polydispersity index of 1.000, and 1.1 g of pentaethylene glycol

(9) ##STR00006##
with a polydispersity index of 1.001.

Embodiment 3

(10) 300 g (0.50 mol) of polyethylene glycol PEG-600 was taken as a starting material and dissolved in 1,000 ml of tetrahydrofuran. Then, to the resulting solution, 1.8 g (0.075 mol) of sodium hydride solution was added in portions and further stirred for 2 h. 4.6 g (0.025 mol) of 4-methylbenzyl bromide was then added for reaction at a temperature of 0 C. over 72 h. 300 ml of saturated ammonium chloride solution was added into the reaction liquid and stirred for stratification. The organic phase was washed with saturated aqueous solution of sodium chloride to neutral. After the solvent was removed by means of vacuum concentration, a mixed sample of 7.2 g of polyethylene glycol mono(4-methylbenzyl) ester was obtained. To the above sample, 12 g of silica gel and 50 ml of ethyl acetate were added, evenly dispersed and dried to prepare a silica gel sample. 200 g of silica gel was added into a glass chromatography column with a diameter of 80 mm, and vibrated to become dense. Then, the above silica gel sample and a small amount of anhydrous sodium sulfate were added into the glass chromatography column, to prevent surface disturbance of the silica gel sample. After a silica gel column for chromatography was formed, a mixed solvent (D/M=10:1) of dichloromethane and methanol was slowly added as an eluent continuously. Samples of different components were collected according to different polarities, and after the eluent was removed, derivatives of polyethylene glycol with a pure component were obtained. Then, 100 ml of 5% hydrochloric acid solution was separately added into the derivatives of polyethylene glycol, stirred at 50 C. and hydrolyzed for 8 h. After being cooled, the derivatives of polyethylene glycol were separately extracted with 100 ml of dichloromethane for 3 times. Then organic phases were combined and dichloromethane was removed by means of vacuum concentration, to obtain a product of 2.7 g of trideca(ethylene glycol)

(11) ##STR00007##
(n=12) with a polydispersity index of 1.002.

Embodiment 4

(12) 150 g (0.10 mol) of polyethylene glycol PEG-1500 was taken as a starting material and dissolved in 1,000 ml of tetrahydrofuran. Then, to the resulting solution, 0.46 g (0.02 mol) of sodium metal was added in portions and further stirred for 2 h. 4.8 g (0.025 mol) of 4-methylbenzenesulfonyl chloride was then added for reaction at a temperature of 60 C. over 8 h. 300 ml of saturated ammonium chloride solution was added into the reaction liquid and stirred for stratification. The organic phase was washed with saturated aqueous solution of sodium chloride to neutral. After the solvent was removed by means of vacuum concentration, a mixed sample of 11.2 g of polyethylene glycol p-toluenesulfonate was obtained. To the above sample, 12 g of silica gel and 50 ml of ethyl acetate were added, evenly dispersed and dried to prepare a silica gel sample. 200 g of silica gel was added into a glass chromatography column with a diameter of 80 mm, and vibrated to become dense. Then, the above silica gel sample and a small amount of anhydrous sodium sulfate were added into the glass chromatography column, to prevent surface disturbance of the silica gel sample. After a silica gel column for chromatography was formed, an eluent (P/E=3:1) was slowly added continuously. Samples of different component were collected according to different polarities, and after the eluent was removed, derivatives of polyethylene glycol with a pure component were obtained. Then, 100 ml of 5% sodium hydroxide solution was separately added into the derivatives of polyethylene glycol, stirred at 50 C. and hydrolyzed for 8 h. After being cooled, the derivatives of polyethylene glycol were separately extracted with 100 ml of dichloromethane for 3 times. Then organic phases were combined and dichloromethane was removed by means of vacuum concentration, to obtain a product of 5.3 g of tritriaconta(ethylene glycol)

(13) ##STR00008##
(n=32) with a polydispersity index of 1.004.

Control Example

(14) 8 g of starting material of polyethylene glycol PEG-400 was taken as a starting material, to which 12 g of silica gel and 50 ml of ethyl acetate were added, evenly dispersed and dried to prepare a silica gel sample. 200 g of silica gel was added into a glass chromatography column with a diameter of 80 mm, and vibrated to become dense. Then, the above silica gel sample and a small amount of anhydrous sodium sulfate were added into the glass chromatography column, to prevent surface disturbance of the silica gel sample. After a silica gel column for chromatography was formed, an eluent (a mixed solvent of ethyl acetate and petroleum ether with a volume ratio of 1:1) was slowly added. Then, samples were collected and analyzed. The product was still a mixture of polyethylene glycols, and had not been separated. For the starting material, products and polydispersity index in Embodiment 1 to Embodiment 4, refer to Table 1.

(15) TABLE-US-00001 TABLE 1 Starting Material, Products and Polydispersity Index in Embodiment 1 to Embodiment 4 Starting Molecular weight Polydispersity Polydispersity material distribution index R-B Eluent n index Embodiment 1 PEG-400 380-420 1.15 Isobutyl chloride P/E = 1:1 7 1.001 8 1.000 Embodiment 2 PEG-200 180-220 1.12 Triphenylmethyl P/E = 1:1 3 1.000 chloride 4 1.001 Embodiment 3 PEG-600 540-660 1.27 4-methylbenzyl bromide D/M = 10:1 1 1.002 2 Embodiment 4 PEG-1500 1350-1650 1.32 4-methylbenzenesulfonyl P/E = 3:1 3 1.004 chloride 2