CN111848665B - Synthesis method of sofosbuvir impurity - Google Patents

Abstract

The invention discloses a synthetic method of a sofosbuvir impurity, which comprises the following steps: (a) grafting a terminal hydroxyl group of the first compound with a first protective group to obtain a first intermediate; (b) grafting a second protecting group on the cyclic hydroxyl of the first intermediate to obtain a second intermediate, wherein the second protecting group is tert-butyldimethylsilyloxy; (c) removing the first protective group on the second intermediate to obtain a third intermediate; (d) grafting a third protecting group on the terminal hydroxyl of the third intermediate to obtain a fourth intermediate; (e) and removing the third protecting group on the fourth intermediate to obtain the Sofosbuvir impurity. Thereby effectively matching and realizing the purification of the intermediate to obtain the high-purity sofosbuvir impurity which can be directly used as a corresponding reference substance.

Description

Synthesis method of sofosbuvir impurity

Technical Field

The invention belongs to the field of organic synthesis, relates to a synthetic method of drug impurities, and particularly relates to a synthetic method of sofosbuvir impurities.

Background

The impurities of the medicine refer to substances which have no treatment effect or influence the stability and the curative effect of the medicine and are even harmful to the health of human bodies. In the aspects of research, production, storage, clinical application and the like of the medicine, the purity of the medicine must be maintained, and the impurities of the medicine are reduced, so that the effectiveness and the safety of the medicine can be ensured. The purity of a drug can be generally evaluated by integrating the structure, appearance, physicochemical constants, impurity inspection, content measurement, and the like of the drug into a whole.

Impurities contained in the medicine are main factors influencing the purity of the medicine, and if the medicine contains more than limited amount of impurities, the physicochemical constants can be changed, the appearance character can be changed, and the stability of the medicine can be influenced; the increase of impurities also inevitably causes the content of the medicine to be lower or the activity to be reduced, and the toxic and side effects are obviously increased. It is therefore necessary to have a thorough and thorough study of the impurities of the drug, which requires the synthesis of high purity intermediate impurities.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for synthesizing the sofosbuvir impurity.

The invention aims to provide a method for synthesizing Sofosbuvir impurities, which comprises the following steps:

(a) the terminal hydroxyl of a first compound is grafted with a first protective group to obtain a first intermediate, and the general chemical structure formula of the first compound is

(b) Grafting a second protecting group on the cyclic hydroxyl of the first intermediate to obtain a second intermediate, wherein the second protecting group is tert-butyldimethylsilyloxy;

(c) removing the first protective group on the second intermediate to obtain a third intermediate;

(d) grafting a third protecting group on the terminal hydroxyl of the third intermediate to obtain a fourth intermediate;

(e) removing a third protecting group on the fourth intermediate to obtain the Sofosbuvir impurity, wherein the chemical structural general formula of the Sofosbuvir impurity is shown in the specification

And TBSO is tert-butyldimethylsiloxy.

Preferably, the first protecting group is tert-butyldimethylsilyloxy, the third protecting group is BzO and Bz is benzoyl.

Further, the step (a) includes the steps of:

(a1) adding the first compound into a mixed solvent of dichloromethane and pyridine, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a first mixture;

(a2) and washing the first mixture with HCl, saturated sodium bicarbonate and saturated saline in sequence, drying, concentrating, and performing column chromatography to obtain a white first intermediate.

Further, in the step (a1), the molar ratio of the first compound to the pyridine to the imidazole to the tert-butyldimethylsilyl chloride is 1: 2-3: 1.5-2: 1.5 to 2.

Further, the step (b) comprises the steps of:

(b1) adding dichloromethane and pyridine into the first intermediate, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a second mixture;

(b2) and adding water into the second mixture for quenching, extracting by using dichloromethane, drying, concentrating, and performing column chromatography to obtain an oily second intermediate.

Further, in the step (b1), the molar ratio of the first intermediate, pyridine, imidazole and tert-butyldimethylsilyl chloride is 1: 2-3: 4.5-5.5: 3.5 to 4.5.

Still further, step (c) comprises the steps of:

(c1) dissolving the second intermediate in tetrahydrofuran, dropwise adding a tetrahydrofuran hydrochloride alcohol solution under an ice bath condition, and carrying out heat preservation reaction to obtain a third mixture; the molar ratio of the first oily matter to the tetrahydrofuran hydrochloride alcohol solution is 1: 1.8-2.2;

(c2) and adding saturated sodium bicarbonate into the third mixture for quenching, extracting for multiple times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating, and performing column chromatography to obtain an oily third intermediate.

Specifically, the step (d) includes the steps of:

(d1) adding dichloromethane, triethylamine and 4-dimethylaminopyridine into the third intermediate, dropwise adding benzoyl chloride under an ice bath condition, and moving to room temperature for reaction;

(d2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting with dichloromethane, drying, concentrating, and performing column chromatography to obtain a fourth intermediate.

More specifically, step (e) comprises the steps of:

(e1) adding tetrahydrofuran to dissolve the fourth intermediate, dropwise adding tetrabutylammonium fluoride trihydrate under an ice bath condition, and naturally heating to room temperature for reacting overnight;

(e2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting for many times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating and performing column chromatography.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: according to the method for synthesizing the sofosbuvir impurity, the operation of grafting the protecting group and removing the protecting group is carried out on the first compound for multiple times, so that the purification of the intermediate is effectively realized in a matching manner, the high-purity sofosbuvir impurity is obtained, and the sofosbuvir impurity can be directly used as a corresponding reference substance.

Drawings

FIG. 1 is a route diagram of a synthetic method of Sofosbuvir impurities of the present invention;

FIG. 2 is a nuclear magnetic spectrum of a first intermediate in the synthetic method of the sofosbuvir impurity of the invention;

FIG. 3 is a nuclear magnetic spectrum of a fourth intermediate in the method for synthesizing the Sofosbuvir impurity;

FIG. 4 is a nuclear magnetic spectrum of the Sofosbuvir impurity in the synthetic method of the invention.

Detailed Description

The synthesis method of the sofosbuvir impurity disclosed by the invention comprises the following steps as shown in figure 1: (a) the terminal hydroxyl of a first compound is grafted with a first protective group to obtain a first intermediate, and the general chemical structure formula of the first compound is

(b) Grafting a second protecting group on the cyclic hydroxyl of the first intermediate to obtain a second intermediate, wherein the second protecting group is tert-butyldimethylsilyloxy; (c) removing the first protective group on the second intermediate to obtain a third intermediate; (d) grafting a third protecting group on the terminal hydroxyl of the third intermediate to obtain a fourth intermediate; (e) removing a third protecting group on the fourth intermediate to obtain the Sofosbuvir impurity, wherein the chemical structural general formula of the Sofosbuvir impurity is shown in the specification

And TBSO is tert-butyldimethylsiloxy. The operation of grafting the protecting group and removing the protecting group is carried out on the first compound for multiple times, so that the purification of the intermediate is effectively realized in a matching way, and the high-purity sofosbuvir impurity can be obtained and can be directly used as a corresponding reference substance.

The first protective group is tert-butyldimethylsilyloxy, the third protective group is BzO and Bz is benzoyl.

Step (a) preferably comprises the steps of: (a1) adding the first compound into a mixed solvent of dichloromethane and pyridine, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a first mixture; (a2) washing the first mixture with HCl, saturated sodium bicarbonate and saturated saline solution in sequence, drying, concentrating, and performing column chromatography to obtain a white first intermediate; in step (a1), the molar ratio of the first compound to pyridine to imidazole to tert-butyldimethylsilyl chloride is 1: 2-3: 1.5-2: 1.5 to 2. The step (b) comprises the steps of: (b1) adding dichloromethane and pyridine into the first intermediate, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a second mixture; (b2) adding water into the second mixture for quenching, extracting by using dichloromethane, drying, concentrating, and performing column chromatography to obtain an oily second intermediate; in step (b1), the molar ratio of the first intermediate, pyridine, imidazole and tert-butyldimethylsilyl chloride is 1: 2-3: 4.5-5.5: 3.5 to 4.5. The step (c) comprises the steps of: (c1) dissolving the second intermediate in tetrahydrofuran, dropwise adding a tetrahydrofuran hydrochloride alcohol solution under an ice bath condition, and carrying out heat preservation reaction to obtain a third mixture; the molar ratio of the first oily matter to the tetrahydrofuran hydrochloride alcohol solution is 1: 1.8-2.2; (c2) and adding saturated sodium bicarbonate into the third mixture for quenching, extracting for multiple times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating, and performing column chromatography to obtain an oily third intermediate. The step (d) comprises the steps of: (d1) adding dichloromethane, triethylamine and 4-dimethylaminopyridine into the third intermediate, dropwise adding benzoyl chloride under an ice bath condition, and moving to room temperature for reaction; (d2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting with dichloromethane, drying, concentrating, and performing column chromatography to obtain a fourth intermediate. The step (e) comprises the steps of: (e1) adding tetrahydrofuran to dissolve the fourth intermediate, dropwise adding tetrabutylammonium fluoride trihydrate under an ice bath condition, and naturally heating to room temperature for reacting overnight; (e2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting for many times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating and performing column chromatography. The steps are all for further or high-purity products on the basis of ensuring the yield of the sofosbuvir impurities.

The following provides a detailed description of preferred embodiments of the invention.

Example 1

The invention provides a synthetic method of a sofosbuvir impurity, which comprises the following steps:

(a) a first intermediate is obtained by connecting a terminal hydroxyl group of a first compound (namely KD002) with a first protective group, and the chemical structural general formula of the first compound is

Namely, it is

The method specifically comprises the following steps:

(a1) adding KD002(4.6g, 0.028mol and 1.0eq) into a reaction vessel, adding DCM (dichloromethane, 46mL) and pyridine (5.5g, 0.07mol and 2.5eq) into the reaction vessel, adding imidazole (3.1g, 0.045mol and 1.6eq) and TBSCl (tert-butyldimethylchlorosilane, 6.3g, 0.042mol and 1.5eq) into the reaction vessel respectively under an ice bath condition, naturally raising the temperature to room temperature, and reacting overnight to obtain a first mixture (TLC shows that a small amount of raw materials are not reacted completely);

(a2) adding 1N HCl (namely 1mol/L) into the first mixture for washing, adding saturated sodium bicarbonate for washing, then washing with saturated sodium chloride, drying, concentrating, and performing column chromatography (eluent PE: EA is 5: 1 in volume ratio) to obtain 4.47g of a white solid (namely the first intermediate, KD003-1), wherein the yield is 57.3% and the purity is 99.5%; the nuclear magnetic spectrum is shown in figure 2.

(b) Grafting a second protecting group on the cyclic hydroxyl of the first intermediate to obtain a second intermediate, wherein the second protecting group is tert-butyldimethylsilyloxy; namely, it is

The method specifically comprises the following steps:

(b1) adding dichloromethane (DCM, 50mL) and pyridine (2.46g, 0.031mol, 2.5eq) into the first intermediate (KD003-1, 3.46g, 0.012mol, 1.0eq), adding imidazole (4.22g, 0.062mol, 5.0eq) and tert-butyldimethylchlorosilane (TBSCl, 7.5g, 0.050mol, 4.0eq) under ice bath condition, naturally raising to room temperature, and reacting overnight to obtain a second mixture (TLC shows that a small amount of raw materials are not reacted completely);

(b2) the second mixture was quenched with water, extracted with dichloromethane, dried, concentrated, and chromatographed (eluent PE: EA 10: 1 by volume) to give the second intermediate as an oil (10 g of oil, over theoretical yield, with possible TBS residue).

(c) Removing the first protective group on the second intermediate to obtain a third intermediate; namely, it is

The method specifically comprises the following steps:

(c1) dissolving the crude product (KD004-4, 10.0g, namely oily second intermediate) in tetrahydrofuran (40mL), dropwise adding a 3N tetrahydrofuran hydrochloride solution (prepared by concentrated hydrochloric acid and tetrahydrofuran) (10mL) under an ice bath condition, and carrying out heat preservation reaction for 2h (TLC shows that the raw materials are reacted) to obtain a third mixture;

(c2) adding saturated sodium bicarbonate into the third mixture for quenching, extracting twice with dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating, performing column chromatography (eluent PE: EA is 2: 1 in volume ratio) to obtain an oily third intermediate (4.38g, TBS is not completely removed), and directly feeding the next step.

(d) Grafting a third protecting group on the terminal hydroxyl of the third intermediate to obtain a fourth intermediate; namely, it is

The method specifically comprises the following steps:

(d1) feeding the crude KD004-5 in the previous step according to 100% yield (3.46g, 0.012mol, 1.0eq), adding DCM (40ml), triethylamine (1.51g, 0.015mol, 1.2eq) and DMAP (0.2g), dropwise adding benzoyl chloride (1.92g, 0.014mol, 1.1eq) under the ice bath condition, and moving to room temperature to react until TLC shows that the reaction is finished;

(d2) quenching with saturated sodium bicarbonate, extracting with dichloromethane, drying, concentrating, and performing column chromatography (eluent PE: EA: 5: 1, volume ratio) to obtain the fourth intermediate (3.529 g white solid; yield of 74.3% (purity 99.5%) in steps (b) - (d), and its nuclear magnetic spectrum is shown in FIG. 3).

(e) Removing a third protecting group on the fourth intermediate to obtain the Sofosbuvir impurity, wherein the chemical structural general formula of the Sofosbuvir impurity is shown in the specification

And wherein TBSO is tert-butyldimethylsilyloxy; namely, it is

The method specifically comprises the following steps:

(e1) dissolving the fourth intermediate (KD004-6, 3.2g, 8.37mmol, 1.0eq) in tetrahydrofuran (64mL), and adding tetrabutylammonium fluoride trihydrate (TBAF & H) dropwise under the ice-bath condition₂O, 5.3g, 16.74mmol, 2.0eq), naturally warmed to room temperature for reaction overnight (TLC showed the starting material was essentially completely reacted);

(e2) adding saturated sodium bicarbonate to quench, extracting with dichloromethane twice at temperature less than 10 deg.C, drying, concentrating, and performing column chromatography (eluent PE: EA is 2: 1, volume ratio) to obtain white solid 1.71g, yield 76.5% (purity 99.6%), and nuclear magnetic spectrum is shown in FIG. 4.

Example 2

The present embodiment provides a method for synthesizing sofosbuvir impurity, which is basically the same as in embodiment 1, except that: in the step (a1), KD002(4.6g, 0.028mol, 1.0eq) is added into a reaction vessel, DCM (dichloromethane, 46mL) and pyridine (4.4g, 0.056mol, 2.0eq) are added, imidazole (2.90g, 0.042mol, 1.5eq) and TBSCl (tert-butyldimethylsilyl chloride, 6.3g, 0.042mol, 1.5eq) are added respectively under the condition of ice bath, the mixture is naturally warmed to room temperature, and the reaction is carried out overnight; the final step (a) yielded 4.92g of a white solid (i.e., the first intermediate, KD003-1) in 63.0% yield and 99.3% purity.

Example 3

The present embodiment provides a method for synthesizing sofosbuvir impurity, which is basically the same as in embodiment 1, except that: in the step (a1), adding KD002(4.6g, 0.028mol, 1.0eq) into a reaction vessel, adding DCM (dichloromethane, 46mL) and pyridine (6.6g, 0.084mol, 3.0eq) into the reaction vessel, adding imidazole (3.87g, 0.056mol, 2.0eq) and TBSCl (tert-butyldimethylchlorosilane, 8.4g, 0.056mol, 2.0eq) into the reaction vessel under an ice bath condition, naturally raising the temperature to room temperature, and reacting overnight to obtain a first mixture; the final step (a) yielded 4.76g of a white solid (i.e., the first intermediate, KD003-1) in 61.0% yield and 99.1% purity.

Comparative example 1

This example provides a method for synthesizing sofosbuvir as an impurity, which is basically the same as that in example 1, except that: step (d) and step (e) were not carried out, which gave an oily third intermediate (4.38g, TBS not completely removed) in low yield and purity, which did not meet the requirements for the impurity control.

Comparative example 2

This example provides a method for synthesizing sofosbuvir as an impurity, which is basically the same as that in example 1, except that: in step (a1), no pyridine was used, and TLC showed that a large amount of starting material was not reacted (yield of the first intermediate was less than 30%, purity about 80%).

Comparative example 3

This example provides a method for synthesizing sofosbuvir as an impurity, which is basically the same as that in example 1, except that: in step (a1), imidazole was not used and the reaction was not allowed to proceed.

Comparative example 4

This example provides a method for synthesizing sofosbuvir as an impurity, which is basically the same as that in example 1, except that: in the step (b1), imidazole (5.064g, 0.0744mol, 6.0eq) and tert-butyldimethylsilyl chloride (TBSCl, 9.375g, 0.0625mol, 5.0eq) are added, and the mixture is naturally warmed to room temperature to react overnight to obtain a second mixture; finally, 3.11g of a fourth intermediate white solid is obtained in the step (d); the yield of the steps from step (b) to step (d) was 65.5%.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (9)

1. A synthetic method of a sofosbuvir impurity is characterized by comprising the following steps:

(a) enabling terminal hydroxyl of a first compound to react in the presence of imidazole and pyridine to attach a first protective group to obtain a first intermediate, wherein the first compound has a chemical structural general formula

；

(b) Grafting a second protecting group on the cyclic hydroxyl of the first intermediate to obtain a second intermediate, wherein the second protecting group is tert-butyldimethylsilyloxy;

(c) removing the first protective group on the second intermediate to obtain a third intermediate;

(d) grafting a third protecting group on the terminal hydroxyl of the third intermediate to obtain a fourth intermediate;

(e) removing a third protecting group on the fourth intermediate to obtain the Sofosbuvir impurity, wherein the chemical structural general formula of the Sofosbuvir impurity is shown in the specification

And TBSO is tert-butyldimethylsiloxy.

2. The method for synthesizing the sofosbuvir impurity according to claim 1, wherein the method comprises the following steps: the first protecting group is tert-butyl dimethyl siloxy, the third protecting group is BzO and Bz is benzoyl.

3. The method for synthesizing the sofosbuvir impurity as claimed in claim 2, wherein the step (a) comprises the steps of:

(a1) adding the first compound into a mixed solvent of dichloromethane and pyridine, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a first mixture;

(a2) and washing the first mixture with HCl, saturated sodium bicarbonate and saturated saline in sequence, drying, concentrating, and performing column chromatography to obtain a white first intermediate.

4. The method for synthesizing the sofosbuvir impurity according to claim 3, wherein the method comprises the following steps: in step (a1), the molar ratio of the first compound to pyridine to imidazole to tert-butyldimethylsilyl chloride is 1: 2-3: 1.5-2: 1.5 to 2.

5. The method for synthesizing the Sofosbuvir impurity of claim 3, wherein the step (b) comprises the steps of:

(b1) adding dichloromethane and pyridine into the first intermediate, respectively adding imidazole and tert-butyldimethylsilyl chloride under an ice bath condition, naturally heating to room temperature, and reacting overnight to obtain a second mixture;

(b2) and adding water into the second mixture for quenching, extracting by using dichloromethane, drying, concentrating, and performing column chromatography to obtain an oily second intermediate.

6. The method for synthesizing sofosbuvir as impurity as claimed in claim 5, wherein in the step (b1), the molar ratio of the first intermediate, pyridine, imidazole and tert-butyldimethylsilyl chloride is 1: 2-3: 4.5-5.5: 3.5 to 4.5.

7. The method for synthesizing the Sofosbuvir impurity of claim 5, wherein the step (c) comprises the steps of:

(c1) dissolving the second intermediate in tetrahydrofuran, dropwise adding a tetrahydrofuran hydrochloride alcohol solution under an ice bath condition, and carrying out heat preservation reaction to obtain a third mixture; the molar ratio of the second intermediate to the tetrahydrofuran hydrochloride solution is 1: 1.8-2.2;

(c2) and adding saturated sodium bicarbonate into the third mixture for quenching, extracting for multiple times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating, and performing column chromatography to obtain an oily third intermediate.

8. The method for synthesizing the sofosbuvir impurity as claimed in claim 7, wherein the step (d) comprises the steps of:

(d1) adding dichloromethane, triethylamine and 4-dimethylaminopyridine into the third intermediate, dropwise adding benzoyl chloride under an ice bath condition, and moving to room temperature for reaction;

(d2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting with dichloromethane, drying, concentrating, and performing column chromatography to obtain a fourth intermediate.

9. The method for synthesizing the sofosbuvir impurity as claimed in claim 8, wherein the step (e) comprises the steps of:

(e1) adding tetrahydrofuran to dissolve the fourth intermediate, dropwise adding tetrabutylammonium fluoride trihydrate under an ice bath condition, and naturally heating to room temperature for reacting overnight;

(e2) after the reaction is finished, adding saturated sodium bicarbonate to quench, extracting for many times by using dichloromethane at the temperature of less than or equal to 10 ℃, drying, concentrating and performing column chromatography.

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