阅读说明：本技术 一种GalNAc中间体的制备方法 (Preparation method of GalNAc intermediate ) 是由 徐苗焕 祝小平 郭四根 于 2020-05-19 设计创作，主要内容包括：本发明涉及一种GalNAc中间体(式III化合物)的制备方法,包括以下步骤：1)式I化合物经脱保护反应得到式II化合物；2)式II化合物与式X化合物经缩合反应或式II化合物与活化后式X化合物在有机碱下反应生成式III化合物。该合成方法工艺路线简单、成本低廉、适合工业化生产。(The invention relates to a preparation method of a GalNAc intermediate (a compound in a formula III), which comprises the following steps: 1) carrying out deprotection reaction on the compound of the formula I to obtain a compound of a formula II; 2) the compound of formula II and the compound of formula X are subjected to condensation reaction or the compound of formula II and the activated compound of formula X are reacted under organic base to generate the compound of formula III. The synthesis method has simple process route and low cost and is suitable for industrial production.)

1. A process for the preparation of a GalNAc intermediate (compound of formula III) comprising the steps of:

deprotecting the compound of formula I to obtain a compound of formula II;

reacting a compound of a formula II with a compound of a formula X in a condensing agent or reacting the compound of the formula II with an acyl chloride form of the compound of the formula X in an organic base condition to obtain a compound of a formula III;

wherein R1 is Ac or Bz, and R2 is Boc or Cbz.

2. The method according to claim 1, wherein the reaction solvent in step 1 is one or more selected from methanol, ethanol and isopropanol, and the reaction solvent in step 2) is one or more selected from tetrahydrofuran, 2-methyltetrahydrofuran, dichloromethane, DMF, DMSO and acetonitrile.

3. The method according to claim 1, wherein the deprotection reaction at R2 ═ Boc in step 1 is carried out under acidic conditions using an organic solvent solution of hydrochloric acid, formic acid, trifluoroacetic acid, or hydrogen chloride at a reaction temperature of 40 to 60 ℃.

4. The method according to claim 3, wherein the organic solvent solution of hydrogen chloride in step 1 is one or more of an ethyl hydrogen chloride solution, a methanol hydrogen chloride solution and an ethanol hydrogen chloride solution.

5. The process of claim 1 wherein in step 1, when R2 ═ Cbz, the deprotection reaction is carried out under palladium on carbon catalyst conditions, with palladium on carbon in an amount of 5 to 15% by weight of the compound of formula I.

6. The process of claim 1, wherein in step 2 the condensation reaction is performed using CDI, DSC, HBTU, HATU, HOBt/EDCI. HCl, and the molar ratio of condensation agent to compound of formula X is 1.0-4.0: 1, the reaction temperature is 0-40 ℃.

7. The process of claim 1, wherein the acid chloride form of the compound of formula X in step 2 is prepared in an activating agent and the acid chloride form of the compound of formula X is reacted with the compound of formula II in the presence of an organic base to form the compound of formula III.

8. The preparation method of claim 7, wherein the activating agent used in step 2 is one or more of oxalyl chloride and thionyl chloride, and the organic base is one or more of DIPEA, triethylamine and DMAP.

9. The process of claim 1, wherein the compound of formula I is prepared by:

the compound of formula A and the compound of formula B react under the conditions of a condensing agent, an organic base and an organic solvent to prepare the compound of formula I, wherein the reaction formula is as follows:

Technical Field

The present invention relates to an improved process for the preparation of GalNAc intermediates.

Background

GalNAc-siRNA is a single conjugate formed by carbohydrate and siRNA, and N-acetylated galactosamine (GalNAc) is covalently conjugated to the 3' end of a sense strand of siRNA with different sequences in a trivalent state to form polysaccharide-siRNA single conjugate. GalNAc is a targeting ligand of a sialic acid receptor (ASGPR), and has higher affinity and rapid internalization capacity with liver surface cells, so that the siRNA conjugate is specifically combined with membrane protein to enter cells, the siRNA conjugate has good application potential in treatment of liver-related diseases related to gene overexpression, and researches show that when the single administration dose of the GalNAc-siRNA single conjugate is 1ug/g, effective silencing of specific target genes of livers can be realized through subcutaneous injection, and the silencing efficiency is far higher than that of siRNA encapsulated by lipid nanoparticles. RNAi is undoubtedly a safer targeted gene therapy tool relative to the time-critical gene editing therapies. The GalNAc-siRNA optimized by chemical modification has better stability and interference efficiency, the siRNA conjugate has good application potential in treatment of liver related diseases related to abnormal high expression of genes, and the GalNAc has the following structural formula:

wherein the compound of the formula III is a key intermediate of a GalNAc compound. Currently, there are two major synthetic routes:

route 1: synthetic route reported in patent CN104717982B

When R1 is Ac, scheme 1 provides a compound of formula N by condensing a compound of formula D with a compound of formula M, by: the active ester is prepared in situ from a compound of formula D to which a compound of formula M is added (in the opposite direction resulting in incomplete substitution). During the operation, the compound of the formula M is found to be a paste, the solubility of the compound is extremely poor, the transfer is extremely difficult, the yield of the compound of the formula M is higher than the theoretical amount due to residual trifluoroacetic acid, the metering of the compound of the formula M is difficult, the subsequent reaction is seriously influenced, the excessive compound of the formula M causes the excessive compound of the formula D, the incomplete reaction is caused due to the excessive compound of the formula M, the conversion rate is low, the reaction controllability is poor, and a large amount of impurities Imp1 and Imp2 are generated, and the structural formulas of the impurities are as follows:

route 2: synthetic route reported in patent CN102006890A

Preparing a compound shown in a formula 17A from tert-butyl acrylate, performing condensation reaction with a compound shown in a formula 15A to obtain a compound shown in a formula 18A, selectively removing tert-butyl ester under the formic acid condition to obtain a compound shown in a formula 19A, performing condensation deprotection to obtain a compound shown in a formula 25A, performing condensation reaction with a compound shown in a formula 13A, and performing multi-step reaction to obtain a compound shown in a formula 27A. The route has the advantages that Bz protection is introduced after the condensation of the carbonyl part, which is beneficial to the reaction monitoring and improves the stability of the protecting group. However, in the route, the compound of formula 17A is a key intermediate and is not commercially available at home, and the compound of formula 17A is prepared from tert-butyl acrylate in the original route and the reported literature, so that the yield is low, the reaction time is long, and the operation is complicated.

Therefore, there is a need in the art for a method for preparing the compound of formula III, which has high yield, simple operation, high product purity, and easy isolation.

Disclosure of Invention

The invention provides a method for synthesizing a GalNac intermediate, which overcomes the defects in the prior art. The method has the advantages of mild reaction conditions, simple steps, high yield, high product purity and easy industrial production.

A process for preparing a GalNac intermediate (Compound III) comprising the steps of:

1) carrying out deprotection reaction on the compound of the formula I to obtain a compound of a formula II;

2) the compound of formula X and the compound of formula II are directly subjected to condensation reaction or the compound of formula X is activated and then reacts with the compound of formula II.

In some embodiments, the step 1 reaction solvent is one or more of methanol, ethanol, isopropanol, preferably ethanol;

in the above reaction, when R2 is Boc, the reaction is carried out under acidic conditions, and the acid is hydrochloric acid, formic acid, trifluoroacetic acid or a hydrogen chloride solution of an organic solvent, preferably a hydrogen chloride ethyl acetate solution;

when R2 is Boc in the above reaction, the reaction temperature is 40-60 ℃;

in the above reaction, when R2 ═ Cbz, a hydrogenation deprotection reaction was carried out under a palladium on carbon catalyst;

when R2 is equal to Cbz in the reaction, the amount of the palladium carbon catalyst is 5-15%, preferably 10% of that of the compound in the formula I;

in some embodiments, the step 2 reaction solvent is one or more of tetrahydrofuran, 2-methyltetrahydrofuran, dichloromethane, DMF, DMSO, acetonitrile, preferably dichloromethane or 2-methyltetrahydrofuran;

in the reaction, the condensation reaction is carried out in the step 2 under the condition of a condensing agent, wherein the condensing agent is one or more of CDI, DSC, HBTU, HOBt/EDCI.HCl and HATU;

in the above reaction, the molar ratio of the condensing agent of step 2 to the compound of formula X is 1.0 to 4.0: 1, the reaction temperature is 0-40 ℃, preferably 30-35 ℃;

in some embodiments, step 2 the compound of formula X is activated under the conditions of an activating agent, such as oxalyl chloride, thionyl chloride;

in the reaction, the organic base used in the step 2 is one or more of DIPEA, triethylamine and DMAP, and the molar ratio of the organic base to the compound in the formula X is 3.0-10: 1;

in some embodiments, the method for preparing the compound of formula I further comprises the steps of reacting the compound of formula a and the compound of formula B under the conditions of a condensing agent, an organic base and an organic solvent to obtain the compound of formula I;

the reaction formula is as follows:

the invention changes the dropping sequence of the active substances, can add the compound of the formula II into the activated solution of the compound of the formula X to complete the reaction, well solves the problem of material transfer, and is convenient for large-scale production. More surprisingly, because the compound of formula II is resistant to hydrogen chloride, the hydrochloride of the compound of formula II (R2 ═ Boc) can be obtained as a hydrochloride in a solid form by adding hydrogen chloride/ethanol directly to an ethanol solution of the compound of formula I or the hydrochloride of the compound of formula II (R2 ═ Cbz) can be isolated by ethanol with hydrochloric acid directly after deprotection, solving the problem that the amine salt cannot be metered accurately. And the compound of the formula X is prepared by taking acrylonitrile as a raw material, so that the yield is high, the purification is easy, and the use of an intermediate of the compound of the formula 17A is omitted. When R1 is Bz, the early introduction of Bz facilitates the HPLC monitoring of each step in the preparation of the compound of formula 27A, and the reaction yield of each step is high and solid, thus facilitating purification.

On the basis of the common knowledge in the field, the above conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

Detailed Description

In the examples herein, if no specific description is made about the reaction temperature or the operation temperature, the temperature is usually referred to as room temperature (15 to 30 ℃).

The invention is further illustrated by the following examples. It is to be understood that these examples are for illustrative purposes only and are not limiting upon the present invention. Various changes or modifications thereof, which may occur to those skilled in the art based on the teachings of the present invention, are within the scope of the present invention.

The addition amount, content and concentration of various substances are referred to herein, wherein the percentage refers to the mass percentage unless otherwise specified.

Purity as referred to herein generally refers to HPLC purity.

Agilent 1200, Bruker NMR 400 MHz.

Reagent: the organic solvents and the like used in the examples of the present invention are all industrial grade and used directly.

Examples

Example 1: synthesis of I (R1 ═ Ac, R2 ═ Boc)

A (38.0g, 1.0eq) was dissolved in Dichloromethane (DCM) and CDI (16.3g, 1.1eq) and triethylamine (12.9g, 1.5eq) were added with stirring and stirred at room temperature for three hours. B (16.3g, 1.1eq) was then added and the reaction was allowed to proceed overnight at room temperature. After the reaction, the reaction mixture was poured into a saturated aqueous sodium bicarbonate solution (100mL), extracted and separated, and the organic phase was collected. The organic phase was washed once more with clear water (100mL), the organic phase was separated, 2N diluted hydrochloric acid was added to the organic phase, extraction was carried out for delamination, the organic phase was washed once more with clear water (100mL), and finally the organic phase was washed with saturated brine (100mL), and the organic phase was collected, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain beige solid I (38.7g, yield 75.5%).

Example 2: synthesis of I (R1 ═ Bz, R2 ═ Cbz)

A (63.3g, 0.1mol) was dissolved in THF1.3L, EDCI. HCl 23.0 g, HOBt 16.2 g, triethylamine 50.5 g were added with stirring, stirring was carried out at room temperature for three hours, then B62.4 g was added, and the reaction was allowed to warm to 40 ℃ overnight. After the reaction, the solvent was removed by rotation, 500mL of water and 500mL of dichloromethane were added, and the organic phase was collected by extraction and separation. The organic phase was washed once with 500mL of clear water, the organic phase was separated, 300mL of 2N diluted hydrochloric acid was added to the organic phase, extraction was carried out for delamination, the organic phase was washed once with 500mL of clear water, and finally washed with 500mL of saturated saline, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain a pale yellow solid I (61.4g, yield: 74.6%).

Example 3: synthesis of I (R1 ═ Bz, R2 ═ Boc)

A (6.33g, 0.01mol) was dissolved in 80mL of 2-methyltetrahydrofuran, and HBTU 5.69g and DIPEA 1.93g were added with stirring and stirred at room temperature for three hours. Then, 2.09g of B was added and the reaction was allowed to warm to 40 ℃ overnight. After the reaction, 50mL of water was added, followed by extraction and separation, 30mL of 2N diluted hydrochloric acid was added to the organic phase, followed by extraction and separation, and the organic phase was washed once with 50mL of clear water and finally with 50mL of saturated saline solution, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain pale yellow solid I (5.63g, yield: 71.3%).

Example 4: synthesis of II (R1 ═ Bz, R2 ═ Cbz):

dissolving I (53.8g, 68.1mmol) in ethanol (200mL), dropwise adding a 20% hydrogen chloride ethanol solution (100mL) at normal temperature, heating the reaction system to 45 ℃ after dropwise adding, and keeping the temperature for reaction for 6 hours. After the completion of the reaction, the reaction mixture was spin-dried under reduced pressure, and then steamed 3 times with n-hexane to obtain II (41.0g, yield: 87.0%) as a white solid.

Example 5: synthesis of II (R1 ═ Ac, R2 ═ Boc)

Dissolving I (20g, 33.0mmol) in ethanol (70mL), dropwise adding a 20% hydrogen chloride ethyl acetate solution (35mL) at normal temperature, heating the reaction system to 45 ℃ after dropwise adding, and keeping the temperature for reaction for 24 hours. After the completion of the reaction, the reaction liquid was spin-dried under reduced pressure, and then steamed 3 times with n-hexane to obtain II (15.0g, yield: 90%) as a white solid.

Example 6: synthesis of II (R1 ═ Bz, R2 ═ Cbz)

Dissolving I (6.3g, 7.6mmol) in ethanol (30mL), adding 10% palladium carbon 0.5 g, introducing hydrogen gas 0.1bar, stirring overnight at normal temperature, filtering, dropwise adding 20% hydrogen chloride ethanol solution (10mL) at normal temperature into the filtrate, precipitating solid after dropwise adding, and filtering to obtain II (4.3g, yield: 82.3%) as white solid.

Example 7: synthesis of II (R1 ═ Ac, R2 ═ Cbz)

Dissolving I (32.0g, 50.2mmol) in isopropanol (150mL), adding 3.2 g of 5% palladium carbon containing 50% of water, introducing 0.1bar of hydrogen, stirring at normal temperature overnight, filtering, dropwise adding a 20% hydrogen chloride ethanol solution (10mL) into the filtrate at normal temperature, precipitating a solid after dropwise adding, and filtering to obtain II (4.3g, yield: 82.3%) as a white solid.

Example 8: synthesis of III (R1 ═ Bz)

X (11.8g, 25mmol) was dissolved in dichloromethane (DCM, 250mL), 2 drops of N, N-Dimethylformamide (DMF) were added, oxalyl chloride (10.2g, 3.2eq) was added dropwise at ambient temperature, and the reaction was continued for 5 hours after the addition was completed. After the reaction, the reaction solution was directly dried under reduced pressure to obtain triacyl chloride (18.7g, yield: 94.0%), and 100mL of DCM was added and dissolved for use.

II (72.7g, 4.0eq) was added to dichloromethane (DCM, 600mL), N-diisopropylethylamine (16.1g, 5.0eq) was added to dissolve, and the above triacyl chloride in dichloromethane was added dropwise to the solution with stirring. After the addition, the reaction was continued at room temperature for 6 hours. After the reaction is finished, 500mL of water is added, 2N hydrochloric acid is used for adjusting the acidity to 2-3, extraction and demixing are carried out, and an organic phase is collected. The organic phase was washed once with 500mL of clear water, 400mL of saturated sodium bicarbonate solution was added to the organic phase, the organic phase was separated by extraction, the organic phase was washed once with 500mL of clear water, the organic phase was separated, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to give orange solid III (60.2g, yield: 97.0%).

1H NMR(400MHz,DMSO-d6)δ7.993(d,J＝9.3Hz,3H),7.961–7.880(m,12H), 7.838(t,J＝5.6Hz,3H),7.797–7.642(m,12H),7.684–7.598(m,3H),7.626–7.529 (m,9H),7.493(t,J＝7.8Hz,6H),7.429–7.236(m,11H),6.540(s,1H)，5.754(d,J＝3.4 Hz,3H),5.367(dd,J＝11.1,3.4Hz,3H),4.965(s,2H),4.736(d,J＝8.5Hz,3H),4.510– 4.409(m,6H),4.401–4.217(m,6H),3.798(q,J＝4.7,4.0Hz,3H),3.578–3.453(m, 15H),3.032(qd,J＝6.5,3.4Hz,12H),2.271(t,J＝6.4Hz,6H),2.056(t,J＝8.2Hz,6H), 1.703(s,9H),1.559–1.445(m,5H),1.503(s,13H)。

Example 9: synthesis of III (R1 ═ Ac)

X (11.8g, 25mmol) was dissolved in 180mL of 2-methyltetrahydrofuran, 13.4 g of CDI was added, and the reaction was continued for 1 hour or more after the addition. After the reaction, 20.2 g of triethylamine was added, and II (41.9g, 3.1eq) was added, followed by incubation at 35 ℃ for overnight reaction. After the reaction is finished, 200mL of water is added, 2N hydrochloric acid is used for adjusting acidity to 2-3, extraction and layering are carried out, an organic phase is collected, 200mL of saturated sodium bicarbonate solution is added into a 500mL clear water organic phase, the organic phase is extracted and separated, the organic phase is washed once by 200mL of clear water, the organic phase is separated, dried by anhydrous sodium sulfate, filtered and concentrated under reduced pressure to obtain an orange solid III (46.5g, yield: 96.3%).

Example 10: synthesis of III (R1 ═ Ac)

X (11.8g, 25.0mmol) was dissolved in DMF 120mL, and HATU 34.4 g and DIPEA 18.1 g were added, and the reaction was continued for 1 hour or more after the addition. After the reaction, II (56.79g, 4.2eq) was added and the temperature was raised to 35 ℃ after the addition was completed for overnight reaction. After the reaction, 200mL of water was added, 2N hydrochloric acid was used to adjust the acidity to 2-3, 100mL of isopropyl acetate was added and 2 extractions were performed, and the organic phases were combined. Washing with 200mL of 2 water for 2 times, separating the organic phase, drying over anhydrous sodium sulfate, filtering, and concentrating under reduced pressure to obtain orange solid III (40.7g, yield: 84.3%).