Method for preparing polyethylene glycol dialdehyde derivative

Abstract

The present invention relates to an improved method for preparing a high purity polyethylene glycol dialdehyde derivative. The preparation method can provide the polyethylene glycol dialdehyde derivative suitable as a raw material for pharmaceuticals because of high purity and terminal activity, by using PEG-diacetal, which is prepared by reacting polyethyleneglycol methanesulfonate with dialkoxy-1-propanol, as an intermediate.

Claims

1. A method for preparing a polyethylene glycol dialdehyde derivative represented by the following formula 4, comprising (1) subjecting a compound of the following formula 2 to an activation treatment with a metal base and then subjecting it to a pegylation with a compound of the following formula 1 to prepare a compound of the following formula 3; and (2) subjecting the compound of formula 3 to an acid treatment: ##STR00006## wherein Ms is methanesulfonyl, R.sub.1 and R.sub.2 are the same or different from each other and each independently represents a (C1-C9) alkyl group, and n is an integer of 3 to 2000.

2. The method according to claim 1, characterized in that the metal base is at least one selected from the group consisting of a metal alkoxide and a metal hydride.

3. The method according to claim 2, characterized in that the metal alkoxide is at least one selected from the group consisting of sodium methoxide, sodium ethoxide, sodium t-butoxide, sodium t-pentoxide, potassium t-butoxide and potassium t-pentoxide.

4. The method according to claim 2, characterized in that the metal hydride is sodium hydride.

5. The method according to claim 1, characterized in that the activation treatment is carried out at from 20 C. to 90 C.

6. The method according to claim 1, characterized in that the pegylation is carried out at a temperature of 0 C. to 90 C.

7. The method according to claim 1, characterized in that step (1) is carried out under an inert gas atmosphere or under an inert atmosphere in which an inert gas is continuously introduced.

8. The method according to claim 7, characterized in that the inert atmosphere is formed by introducing at least one inert gas selected from the group consisting of nitrogen, argon and helium.

9. The method according to claim 1, characterized in that step (1) is carried out in at least one solvent selected from the group consisting of toluene, dichloromethane, chloroform, tetrahydrofuran, acetonitrile and 1,4-dioxane.

10. The method according to claim 1, characterized in that the compound of formula 3 prepared in step (1) is applied, as it is, in situ to step (2).

11. The method according to claim 1, characterized in that the acid treatment in step (2) is carried out using at least one acid selected from the group consisting of hydrochloric acid, acetic acid, formic acid, trifluoroacetic acid and phosphoric acid.

12. The method according to claim 1, characterized in that the acid treatment of step (2) is carried out at a temperature between 0 C. and 50 C.

13. The method according to claim 1, characterized in that step (2) is carried out in at least one solvent selected from the group consisting of water, methanol, ethanol, propanol and t-butanol.

14. The method according to claim 1, characterized in that the compound of formula 1 is prepared by reacting polyethylene glycol (PEG) and methanesulfonyl halide (halide=Cl, Br, or F) in the presence of base.

15. The method according to claim 14, characterized in that the base is at least one selected from the group consisting of triethylamine and tributylamine.

Description

EXAMPLE 1

Preparation of PEG-dialdehyde

(1) Step 1): Preparation of PEG-diethyl Acetal

(2) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(3) To one of the reaction vessels, 1.8 mL of 3,3-diethoxy-1-propanol and 40 mL of toluene were charged. Thereafter, 1.4 g of potassium t-butoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(4) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 50 mL of an aqueous saturated ammonium chloride solution was added to the reaction solution, stirred for 5 minutes, and 100 mL of dichloromethane was added to extract the organic layer. 100 mL of dichloromethane was added to the aqueous layer, and the organic layer was further extracted, and the organic layers were combined and concentrated under reduced pressure. The concentrate was dissolved in 10 mL of dichloromethane, 150 mL of methyl t-butyl ether was added dropwise, and the mixture was stirred at room temperature for 2 hours. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 9.3 g (yield: 90.0%) of the target compound PEG-diethyl acetal.

(5) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(6) Step 2): Preparation of PEG-dialdehyde

(7) To another reaction vessel, 9 g of PEG-diethyl acetal obtained above was added and dissolved using 45 mL of distilled water, and then, 90 mL of 0.1N hydrochloric acid was added dropwise. The reaction solution was stirred at room temperature for 2 hours and then adjusted to pH 6 using 5% sodium bicarbonate solution. 90 mL of dichloromethane was added to the reaction solution to extract the organic layer, and 90 mL of dichloromethane was added to the aqueous layer to further extract the organic layer. The organic layers were combined, dried over sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure. The concentrate was dissolved in 9 mL of dichloromethane, 180 mL of methyl t-butyl ether was added dropwise, and the mixture was stirred at room temperature for 2 hours. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 8 g (yield: 92.0%) of the target compound PEG-dialdehyde.

(8) Terminal activity: 66.8%.

(9) .sup.1H-NMR (CDCl.sub.3, 400 MHz) 9.49 (t, 2H, J=2 Hz), 3.59-3.83 (m, 304H), 2.66-2.70 (m, 4H), 1.89 (m, 4H).

EXAMPLE 2

Preparation of PEG-dialdehyde

(10) Step 1): Preparation of PEG-diethyl Acetal

(11) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(12) To one of the reaction vessels, 1.8 mL of 3,3-diethoxy-1-propanol and 40 mL of toluene were charged. Thereafter, 1.4 g of potassium t-butoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(13) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 50 mL of an aqueous saturated ammonium chloride solution was added to the reaction solution, stirred for 5 minutes, and 100 mL of dichloromethane was added to extract the organic layer. 100 mL of dichloromethane was added to the aqueous layer to further extract the organic layer, and the organic layers were combined and concentrated under reduced pressure.

(14) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(15) Step 2): Preparation of PEG-dialdehyde

(16) To another reaction vessel, the concentrate obtained above was added and dissolved using 50 mL of distilled water, and then, 100 mL of 0.1N hydrochloric acid was added dropwise. The reaction solution was stirred at room temperature for 2 hours and then adjusted to pH 6 using 5% sodium bicarbonate solution. 100 mL of dichloromethane was added to the reaction solution to extract the organic layer, and 100 mL of dichloromethane was added to the aqueous layer to further extract the organic layer. The organic layers were combined, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure. The concentrate was dissolved in 8 mL of dichloromethane, 200 mL of methyl t-butyl ether was added dropwise, and the mixture was stirred at room temperature for 2 hours. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 8.5 g of the target compound PEG-dialdehyde (yield: 86.0%).

(17) Terminal activity: 73.1%.

EXAMPLE 3

Preparation of PEG-dialdehyde

(18) Step 1): Preparation of PEG-diethyl Acetal

(19) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(20) To one of the reaction vessels, 2.2 mL of 3,3-diethoxy-1-propanol and 40 mL of toluene were charged. Thereafter, 1.4 g of potassium t-butoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(21) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 30 mL of an aqueous saturated ammonium chloride solution was added to the reaction solution, stirred for 5 minutes, and 30 mL of dichloromethane was added to extract the organic layer.

(22) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(23) Step 2): Preparation of PEG-dialdehyde

(24) To another reaction vessel, 200 mL of 0.05N hydrochloric acid was added, and the organic layer extracted above was added dropwise over 30 minutes. The reaction solution was stirred at room temperature for 1 hours and then adjusted to pH 6 using 5% sodium bicarbonate solution. 100 mL of dichloromethane was added to the reaction solution, and the organic layer was dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure. The concentrate was dissolved in 8 mL of dichloromethane, 200 mL of methyl t-butyl ether was added dropwise, and the mixture was stirred at room temperature for 1 hours. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 7.2 g (yield: 73.0%) of the target compound PEG-dialdehyde.

(25) Terminal activity: 77.1%.

EXAMPLE 4

Preparation of PEG-dialdehyde

(26) Step 1): Preparation of PEG-diethyl Acetal

(27) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(28) To one of the reaction vessels, 2.2 mL of 3,3-diethoxy-1-propanol and 40 mL of toluene were charged. Thereafter, 1.4 g of sodium t-pentoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(29) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 30 mL of distilled water was added to the reaction solution, stirred for 10 minutes to extract the aqueous layer. 30 mL of dichloromethane and 80 mL of toluene were added to the aqueous layer and stirred for 10 minutes to extract the organic layer.

(30) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(31) Step 2): Preparation of PEG-dialdehyde

(32) By repeating the same procedure as in step 2) of Example 3 above using the organic layer extracted in step 1) above, 4.7 g (yield: 48%) of the target compound PEG-dialdehyde was obtained.

(33) Terminal activity: 82.6%.

EXAMPLE 5

Preparation of PEG-dialdehyde

(34) Step 1): Preparation of PEG-diethyl Acetal

(35) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(36) To one of the reaction vessels, 4.5 mL of 3,3-diethoxy-1-propanol and 40 mL of toluene were charged. Thereafter, 1.6 g of sodium t-pentoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(37) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 30 mL of distilled water was added to the reaction solution, stirred for 10 minutes to extract the aqueous layer. 30 mL of dichloromethane and 80 mL of toluene were added to the aqueous layer and stirred for 10 minutes to extract the organic layer.

(38) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(39) Step 2): Preparation of PEG-dialdehyde

(40) By repeating the same procedure as in step 2) of Example 3 above using the organic layer extracted in step 1) above, 4.7 g (yield: 48%) of the target compound PEG-dialdehyde was obtained.

(41) Terminal activity: 85.8%.

(42) .sup.1H-NMR (CDCl.sub.3, 400 MHz) 9.49 (t, 2H, J=2 Hz), 3.59-3.83 (m, 304H), 2.66-2.70 (m, 4H), 1.89 (m, 4H).

(43) The number average molecular weight (Mn) measured by GPC: 3321.

(44) Polydispersity(PDI): 1.04.

(45) MPF (main peak fraction) purity: 99.51%.

EXAMPLE 6

Preparation of PEG-dialdehyde

(46) Step 1): Preparation of PEG-diethyl Acetal

(47) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(48) To one of the reaction vessels, 40 mL of toluene and 4.48 mL of 3,3-diethoxy-1-propanol were charged. Thereafter, 0.78 g of sodium methoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(49) To the other reaction vessel, 10 g of PEG-Ms obtained in Preparation Example 1 and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 30 mL of water was added to the reaction solution to separate the layers, and 30 mL of dichloromethane and 80 mL of toluene were added to the aqueous layer to extract the organic layer.

(50) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 1.1 L/min.

(51) Step 2): Preparation of PEG-dialdehyde

(52) To another reaction vessel, 200 mL of 0.05N hydrochloric acid solution was added, and the previously extracted organic layer was added dropwise over 30 minutes. The reaction solution was stirred at room temperature for 30 minutes and then adjusted to pH 6 using 5% sodium bicarbonate solution. 100 mL of dichloromethane was added to the reaction solution to extract the organic layer, and then sodium sulfate was added to the organic layer and stirred for 30 minutes. The reaction solution was filtered and the filtrate was concentrated under reduced pressure. The concentrate was dissolved in 8 mL of dichloromethane and 200 mL of methyl t-butyl ether was added dropwise over 20 minutes. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 2.98 g (yield: 30.0%) of the target compound PEG-dialdehyde.

(53) Terminal activity: 81.4%.

EXAMPLE 7

Preparation of PEG-dialdehyde

(54) The same procedure as in Example 6 was repeated to obtain 3.67 g (yield: 37%) of PEG-dialdehyde, except that 0.98 g of sodium ethoxide was used as the metal base.

(55) Terminal activity: 77.8%.

EXAMPLE 8

Preparation of PEG-dialdehyde

(56) The same procedure as in Example 6 was repeated to obtain 2.98 g (yield: 30%) of PEG-dialdehyde, except that 1.38 g of sodium t-butoxide was used as the metal base.

(57) Terminal activity: 81.7%.

EXAMPLE 9

Preparation of PEG-dialdehyde

(58) The same procedure as in Example 6 was repeated to obtain 3.37 g (yield: 34%) of PEG-dialdehyde, except that 1.60 g of potassium t-butoxide was used as the metal base.

(59) Terminal activity: 81.7%.

EXAMPLE 10

Preparation of PEG-dialdehyde

(60) The same procedure as in Example 6 was repeated to obtain 4.68 g (yield: 48%) of PEG-dialdehyde, except that 1.58 g of sodium t-pentoxide was used as the metal base.

(61) Terminal activity: 85.8%.

EXAMPLE 11

Preparation of PEG-dialdehyde

(62) The same procedure as in Example 6 was repeated to obtain 3.47 g (yield: 35%) of PEG-dialdehyde, except that 8.4 mL of potassium t-pentoxide (1.7M toluene solution) was used as the metal base.

(63) Terminal activity: 82.3%.

EXAMPLE 12

Preparation of PEG-dialdehyde

(64) The same procedure as in Example 6 was repeated to obtain 4.36 g (yield: 44%) of PEG-dialdehyde, except that 0.58 g of 60% sodium hydride was used as the metal base.

(65) Terminal activity: 81.9%.

EXAMPLE 13

Preparation of PEG-dialdehyde

(66) Step 1): Preparation of PEG-diethyl Acetal

(67) Nitrogen gas was continuously introduced into two 500 mL reaction vessels, and these reaction vessels were flame dried to remove moisture.

(68) To one of the reaction vessels, 20 mL of toluene and 2.24 mL of 3,3-diethoxy-1-propanol were charged. Thereafter, 0.79 g of sodium t-pentoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour.

(69) To the other reaction vessel, 5 g of PEG-Ms obtained in Preparation Example 1 and 20 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours. 15 mL of water was added to the reaction solution to separate the layers, and 15 mL of dichloromethane and 40 mL of toluene were added to the aqueous layer to extract the organic layer.

(70) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel at a flow rate of 0.56 L/min.

(71) Step 2): Preparation of PEG-dialdehyde

(72) To another reaction vessel, 100 mL of 0.05N hydrochloric acid solution was added, and the previously extracted organic layer was added dropwise over 30 minutes. The reaction solution was stirred at room temperature for 30 minutes and then adjusted to pH 6 using 5% sodium bicarbonate solution. 50 mL of dichloromethane was added to the reaction solution to extract the organic layer, and then sodium sulfate was added to the organic layer and stirred for 30 minutes. The reaction solution was filtered and the filtrate was concentrated under reduced pressure. The concentrate was dissolved in 4 mL of dichloromethane and 100 mL of methyl t-butyl ether was added dropwise over 20 minutes. The resulting crystals were filtered, washed with methyl t-butyl ether, and dried by nitrogen at room temperature to obtain 1.80 g (yield: 36%) of the target compound PEG-dialdehyde.

(73) Terminal activity: 83.7%.

EXAMPLE 14

Preparation of PEG-dialdehyde

(74) The same procedure as in Example 13 was repeated to obtain 1.93 g (yield: 39%) of PEG-dialdehyde, except that the flow of nitrogen gas was adjusted to 1.1 L/min and 5 mL of toluene was further added to the activated solution.

(75) Terminal activity: 86.4%.

EXAMPLE 15

Preparation of PEG-dialdehyde

(76) The same procedure as in Example 13 was repeated to obtain 1.88 g (yield: 38%) of PEG-dialdehyde, except that the flow of nitrogen gas was adjusted to 2.8 L/min and 13 mL of toluene was further added to the activated solution.

(77) Terminal activity: 82.1%.

EXAMPLE 16

Preparation of PEG-dialdehyde

(78) The same procedure as in Example 13 was repeated to obtain 2.03 g (yield: 41%) of PEG-dialdehyde, except that the flow of nitrogen gas was adjusted to 3.7 L/min and 18 mL of toluene was further added to the activated solution.

(79) Terminal activity: 81.4%.

EXAMPLE 17

Preparation of PEG-dialdehyde

(80) The same procedure as in Example 5 was repeated to obtain 4.6 g (yield: 47%) of PEG-dialdehyde, except for using argon gas instead of nitrogen gas as an inert gas.

(81) Terminal activity: 83.1%.

EXAMPLE 18

Preparation of PEG-dialdehyde

(82) The same procedure as in Example 5 was repeated to obtain 4.3 g (yield: 44%) of PEG-dialdehyde, except for using helium gas instead of nitrogen gas as an inert gas.

(83) Terminal activity: 82.4%.

Comparative Example 1

Preparation of PEG-dialdehyde

(84) The same procedure as in Example 6 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 2.38 g (yield: 24%) of PEG-dialdehyde.

(85) Terminal activity: 13.0%.

Comparative Example 2

Preparation of PEG-dialdehyde

(86) The same procedure as in Example 7 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 2.68 g (yield: 27%) of PEG-dialdehyde.

(87) Terminal activity: 33.6%.

Comparative Example 3

Preparation of PEG-dialdehyde

(88) The same procedure as in Example 8 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 2.38 g (yield: 24%) of PEG-dialdehyde.

(89) Terminal activity: 33.9%.

Comparative Example 4

Preparation of PEG-dialdehyde

(90) The same procedure as in Example 9 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 3.18 g (yield: 32%) of PEG-dialdehyde.

(91) Terminal activity: 69.5%.

Comparative Example 5

Preparation of PEG-dialdehyde

(92) The same procedure as in Example 10 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 2.88 g (yield: 29%) of PEG-dialdehyde.

(93) Terminal activity: 49.1%.

Comparative Example 6

Preparation of PEG-dialdehyde

(94) The same procedure as in Example 11 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 3.37 g (yield: 34%) of PEG-dialdehyde.

(95) Terminal activity: 69.8%.

Comparative Example 7

Preparation of PEG-dialdehyde

(96) The same procedure as in Example 12 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 3.18 g (yield: 32%) of PEG-dialdehyde.

(97) Terminal activity: 68.0%.

Comparative Example 8

Preparation of PEG-dialdehyde

(98) ##STR00005##

(99) Step 1): Preparation of Diethoxypropyl Methanesulfonate

(100) To the reaction vessel, 1.69 g of 3,3-diethoxy-1-propanol and 17 mL of dichloromethane were charged. While keeping the reaction temperature below 10 C., 1.9 mL of triethylamine and 1.06 mL of methanesulfonyl chloride were added, and the mixture was stirred at 5 C. for 1 hour. To the reaction solution, 20 mL of toluene and 2.24 mL of 3,3-diethoxy-1-propanol were added. When the reaction was completed, 50 mL of water was added, and the mixture was stirred for 5 minutes. After extracting the organic layer, 50 mL of dichloromethane was further added to the aqueous layer to further extract the organic layer. The organic layers were combined, washed with 50 mL of distilled water, dried over magnesium sulfate, filtered, and the filtrate was concentrated under reduced pressure to give diethoxypropyl methanesulfonate

(101) .sup.1H-NMR (CDCl.sub.3, 400 MHz) 4.65 (t, 1H, J=5.6 Hz), 4.32 (t, 2H, J=5.6 Hz), 3.71-3.64 (m, 2H), 3.56-3.48 (m, 2H), 3.01 (s, 3H), 2.07-2.03 (m, 2H), 1.21 (t, 6H, J=7.2 Hz),

(102) Step 2): Preparation of PEG-diethyl Acetal

(103) Nitrogen gas was continuously introduced into two reaction vessels, and these reaction vessels were flame dried to remove moisture.

(104) To one of the reaction vessels, 40 mL of toluene and 10 g of polyethylene glycol were charged. Thereafter, 0.70 g of sodium t-pentoxide was added and the temperature was raised to 50 C., and the solution was activated by stirring for 1 hour and cooled to room temperature.

(105) To the other reaction vessel, 2.7 g of diethoxypropyl methanesulfonate prepared in step 1) above and 40 mL of toluene were added, and the previously activated solution was added dropwise over 1 hour and then stirred at room temperature for 2 hours.

(106) All the above reaction procedures were carried out under the condition that nitrogen gas was continuously introduced into the reaction vessel.

(107) As a result of TLC, it was confirmed that diethoxypropyl methanesulfonate was disappeared, but the reaction was proceeded only at a rate of about 30%. The reason why the reaction was not completed as described above seems to be that the intermediate diethoxypropyl methanesulfonate was unstable and thus decomposed.

Comparative Example 9

Preparation of PEG-dialdehyde

(108) The same procedure as in Example 13 was repeated, under the condition that no nitrogen gas was introduced into the reaction vessel, to obtain 1.49 g (yield: 30%) of PEG-dialdehyde.

(109) Terminal activity: 50.1%.

Experimental Example 1

Analysis of Yield and Terminal Activity Depending on Treatment Conditions

(110) The tendency of yield and terminal activity of PEG-dialdehydes prepared in the above Examples and Comparative Examples according to the production conditions were analyzed as follows:

(111) (1) Analysis of Changes in Terminal Activity Depending on Inert Atmosphere During Activation

(112) The present invention is carried out in an inert atmosphere when activated, and table 1 below compares and analyzes terminal activity of PEG-dialdehyde which is finally obtained in the presence or absence of inert atmosphere

(113) TABLE-US-00001 TABLE 1 Terminal activity (%) Non-use Use of of nitrogen nitrogen (Comparative Item Metal base (Example) Example) Example 6/ Sodium 81.4 13.0 Comparative Example 1 methoxide Example 7/ Sodium 77.8 33.6 Comparative Example 2 ethoxide Example 8/ Sodium 81.7 33.9 Comparative Example 3 t-butoxide Example 9/ Potassium 81.7 69.5 Comparative Example 4 t-butoxide Example 10/ Sodium 85.8 49.1 Comparative Example 5 t-pentoxide Example 11/ Potassium 82.3 69.8 Comparative Example 6 t-pentoxide Example 12/ Sodium 81.9 68.0 Comparative Example 7 hydride

(114) Referring to table 1, it can be seen that only when the activation is carried out in a nitrogen atmosphere, it is possible to produce PEG-dialdehyde with excellent terminal activity.

(115) (2) Analysis of Changes in Yield and Terminal Activity Depending on the kind of Inert Gas During Activation

(116) Table 2 below compares yield and terminal activity depending on the type of gas in the inert atmosphere.

(117) TABLE-US-00002 TABLE 2 Item Inert gas Yield (%) Terminal activity (%) Example 5 Nitrogen 48 85.8 Example 17 Argon 47 83.1 Example 18 Helium 44 82.4 Comparative Example 5 X 29 49.1

(118) Referring to table 2, it can be seen that when the inert gas was used during the activation, terminal activity is almost doubled and has no significant difference depending on the type of inert gas, but when nitrogen is used, it is more advantageous in terms of yield and terminal activity.

(119) Analysis of Changes in Yield and Terminal Activity Depending on the Flow Rate of Inert Gas During Activation

(120) Table 3 below compares yield and terminal activity depending on the flow rate of the inert gas.

(121) TABLE-US-00003 TABLE 3 Flow rate of Amount of Solution Terminal N.sub.2 remaining after Yield activity Item (L/min) activation (mL) (%) (%) Comparative 0 23 30 50.1 Example 9 Example 13 0.56 23 36 83.7 Example 14 1.1 15 39 86.4 Example 15 2.8 7 38 82.1 Example 16 3.7 2 41 81.4

(122) Referring to table 3, it can be seen that when the activation is carried out in an inert atmosphere, PEG-dialdehyde with high terminal activity can be obtained. In that case, referring to the results depending on the flow rate of the inert gas, it can be seen that PEG-dialdehyde with high terminal activity can be produced at a flow rate of 1.1 L/min.

(123) (4) Purification Treatment after Pegylation

(124) There was a difference in yield and terminal activity depending on the separation and purification method of PEG-diethyl acetal prepared after the pegylation of step 1), and the results are shown in table 4 below.

(125) TABLE-US-00004 TABLE 4 Separation and Terminal Item Metal base purification method activity (%) Example 1 Potassium t-butoxide Extraction- 66.8 concentration- crystallization Example 2 Potassium t-butoxide Extraction- 73.1 concentration Example 3 Potassium t-butoxide Extraction 77.1 (used in-situ) Example 4 Sodium t-pentoxide Extraction 82.6 (used in-situ) Example 5 Sodium t-pentoxide Extraction 85.8 (used in-situ)

(126) Referring to table 4, it can be seen that terminal activity of the finally obtained PEG-dialdehyde differs depending on the separation and purification process of PEG-diethyl acetal after the pegylation. Referring to Examples 1 and 2, it can be seen that when performing up to crystallization, terminal activity decreases, and when using the solution separated after the extraction process with the organic layer in the next step (in-situ), it is possible to prepare PEG-dialdehyde with excellent terminal activity.

(127) It can be seen that this tendency was the same even when comparing to Examples 4 and 5 using different kinds of metal bases