Preparation method of tenofovir prodrug

Abstract

The present invention relates to a method for preparing 9-[(R)-2-[[(S)-[[[1-(isopropoxycarbonyl)-1-methyl]ethyl]amino]phenoxyphosphinyl]methoxy]propyl]adenine fumarate of a compound of formula (I). The method comprises taking (R)-9-(2-methoxypropyl phosphate)-adenine as a starting material, first reacting it with phenol in the presence of a condensing agent to obtain compound (II); further chlorinating compound (II) to obtain compound (III-1), which is then condensed with compound (IV) to obtain compound (V); salifying compound (V) with D-(+)-dibenzoyltartaric acid anhydrate, followed by separation in an acetone / water mixed solvent to obtain compound (VI); dissociating compound (VI) through crystallization to obtain compound (VII); and finally salifying compound (VII) with fumaric acid to obtain a finished compound of formula (I). This synthetic method has high yield, good stability, simple operation, and is suitable for industrial production of pharmaceuticals. #imgabs0#

Description

Technical Field

[0001] The present invention relates to the field of pharmaceutical chemicals, and in particular to a method for preparing a novel tenofovir prodrug. Background Art

[0002] Tenofovir Amibufenamide, also known as 9-[(R)-2-[[(S)-[[[1-(Isopropoxycarbonyl)-1-methyl]ethyl]amino]phenoxyphosphinyl]methoxy]propyl]adenine fumarate, has a structure shown in Formula (I). It is a phosphoramidite prodrug of tenofovir and a nucleoside reverse transcriptase inhibitor. In June 2021, the National Medical Products Administration approved the marketing of amibufenfovir tablets, providing a new treatment option for patients with chronic hepatitis B.

[0003]

[0004] Amitofovir is a new second-generation fufovir substitute and the first Chinese-developed oral anti-hepatitis B virus drug. Amitofovir is a novel nucleotide reverse transcriptase inhibitor. Its optimized structure allows for enhanced cell membrane penetration, allowing for easier entry into hepatocytes, enabling liver-targeted therapy. It also effectively improves the drug's plasma stability, reduces systemic TFV exposure, and makes long-term treatment safer.

[0005] Clinical research results show that compared to tenofovir disoproxil fumarate, amitenofovir requires less than one-tenth the dose to achieve similar antiviral efficacy, comparable to first-line drugs. Furthermore, it has less impact on bone density and kidney function, demonstrating improved bone and kidney safety.

[0006] CN103665043A reports a method for preparing emtenofovir, but the yield of this method is too low, and the optical isomers (Ia) and (Ib) produced during the liquid phase separation reaction are prepared. The operation is cumbersome and the cost is too high, making it unsuitable for large-scale preparation.

[0007] CN104558035A reports a method for using D-(+)-dibenzoyltartaric acid to form a salt and crystallize it, followed by alkali neutralization to separate the compound represented by formula (Ia) and its diastereoisomer mixture, thereby preparing a compound represented by formula (Ia) with an optical purity of 95% or more. CN109384814A discloses recrystallizing a crude compound represented by formula (Ia) in acetonitrile, a mixed solvent of acetonitrile and an aromatic hydrocarbon solvent, or a mixed solvent of acetonitrile and an ether solvent, thereby preparing a compound represented by formula (Ia) with an optical purity of 99.8% or more. However, none of the above methods solves the problems of low synthesis yield and high production cost. Therefore, there is an urgent need to find a preparation method for emtenofovir with high synthesis yield, simple operation, and suitable for industrial production.

[0008] Summary of the Invention

[0009] In order to solve the problems existing in the prior art, the present invention further studies the preparation method of the compound 9-[(R)-2-[[(S)-[[[1-(isopropoxycarbonyl)-1-methyl]ethyl]amino]phenoxyphosphinyl]methoxy]propyl]adenine fumarate.

[0010] The object of the present invention is to provide a method for preparing a compound represented by formula (I) with high synthesis yield, avoiding the use of heavy metals, simple operation and suitable for industrial production of pharmaceuticals. The process flow is as follows:

[0011]

[0012] The following steps are involved:

[0013] a. Compound (II), phenol, and a condensing agent are added to an aprotic solvent, and the reaction is carried out at a temperature of 85-95°C. The reaction is monitored until completion to obtain compound (III);

[0014] b. Compound (III) and thionyl chloride are added to a highly soluble solvent and the reaction is carried out at a temperature of 70-80°C. The reaction is monitored until completion to obtain compound (III-1). Compound (III-1) is subjected to a condensation reaction with compound (IV) to obtain compound (V);

[0015] c. Compound (V) is salified with D-(+)-dibenzoyltartaric acid anhydrate and then resolved in an acetone / water mixed solvent to obtain compound (VI);

[0016] d. Adding compound (VI) to an aprotic polar solvent, adding an inorganic base, and after the dissociation is complete, crystallizing from an organic solvent to obtain compound (VII);

[0017] e. Compound (VII) is reacted with fumaric acid in an organic solvent to form a salt to obtain a compound of formula (I).

[0018] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the condensation reagent in step a is selected from 1,3-dicyclohexylcarbodiimide (DCC) and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), preferably EDC·HCl.

[0019] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the molar ratio of compound (II), condensation agent, and phenol in step a is 1:1.5:1.5~1:3.0:2.5; preferably, the molar ratio of compound (II), condensation agent, and phenol is 1:2:2.

[0020] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the reaction temperature in step a is controlled at 85-95°C.

[0021] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the reaction time in step a is controlled to be 15 to 20 hours, preferably 15 to 16 hours.

[0022] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the reaction solvent in step a is 1-methyl-2-pyrrolidone (NMP).

[0023] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the specific operation process of step a is: compound (II) and phenol are added to an aprotic solvent, a condensing agent EDC·HCl is added, the temperature is controlled to 85-95°C, and the reaction is monitored until the reaction is completed to obtain compound (III).

[0024] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the acyl chloride reagent in step b is thionyl chloride.

[0025] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the solvent used in step b is sulfolane and toluene, preferably toluene.

[0026] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the reaction time of compound (III) and thionyl chloride in step b is controlled to be 40 to 70 hours, preferably 39 to 40 hours.

[0027] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the temperature of the reaction between compound (III) and thionyl chloride in step b is controlled at 70-90°C, preferably 70-80°C.

[0028] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the molar ratio of compound (III-1) to (IV) in step b is 1:3.5.

[0029] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the temperature of the reaction of compound (III-1) with (IV) in step b is controlled at -5 to 25°C, preferably -5 to 5°C.

[0030] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), when compound (III-1) reacts with (IV), the specific preparation method is to first add a mixed solution of compound (IV) / N,N-diisopropylethylamine (DIEA), and then dropwise add dichloromethane.

[0031] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the specific operation process of step b is as follows: adding a highly soluble solvent to compound (III) and thionyl chloride, controlling the temperature to 70-80°C for reaction, and monitoring the completion of the reaction to obtain compound (III-1), and condensing compound (III-1) with compound (IV) to obtain compound (V);

[0032] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the solvent in step c is an acetone / water mixed solvent.

[0033] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the ratio of acetone / water used in step c is 1:0.5 to 1:1.5, preferably 1:1.

[0034] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the specific operation process of step c is: compound (V) is salified with D-(+)-dibenzoyltartaric acid anhydrate and then resolved in an acetone / water mixed solvent to obtain compound (VI);

[0035] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the solvent in step d is an acetonitrile / isopropyl ether mixed solvent.

[0036] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the ratio of compound (VI) / acetonitrile / isopropyl ether used in step d is 1 g:1.5 L:3 L to 1 g:2 L:10 L, preferably the ratio of compound (VI) / acetonitrile / isopropyl ether is 1 g:1.5 L:5 L.

[0037] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the reaction solvent used in step d is an aprotic polar solvent, preferably dichloromethane or acetonitrile, more preferably dichloromethane.

[0038] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the specific preparation process of step d is: adding compound (VI) to an aprotic polar solvent, adding an inorganic base, and then crystallizing with an organic solvent after the free radical is completed to obtain compound (VII).

[0039] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the specific operation process of step e is: compound (VII) and fumaric acid are salted in an organic solvent to obtain the compound of formula (I).

[0040] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the organic solvent used in step e is a mixed solvent of n-heptane / anhydrous methanol.

[0041] In a preferred embodiment of the present invention, in the method for preparing the compound of formula (I), the ratio of n-heptane to anhydrous methanol in the mixed solvent used in step e is 1:1 to 1:5, preferably 1:4.

[0042] In the present invention, the use of EDC·HCl in step a improves the yield of the condensation process and simplifies the operation process; in step b, an unconventional feeding method is adopted, in which a compound (IV) / DIEA mixed solution is first added, and then dichloromethane is added dropwise, thereby improving the yield of the target isomer; and in step e, an ideal methanol / n-heptane mixed solvent is screened to obtain the target product with higher purity and higher homogeneity.

[0043] Therefore, the preparation method of the present invention has a higher yield, and its total yield is at least 4 times higher than that of the prior art. In addition, the product has high purity, is simple to operate, and is suitable for the industrial production of medicines. DETAILED DESCRIPTION

[0044] In order to clearly illustrate the technical solution and technical effects of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0045] Example 1

[0046] To a reaction flask, add 1-methyl-2-pyrrolidone (NMP) (150 mL), triethylamine (30 mL), phenol (35 g), and Compound II (50 g). Stir at 45-55°C for 15-20 minutes. Then add the condensation reagent. After addition, stir at 85-95°C for 15-16 hours. After the reaction is complete, adjust the pH to 10-11 with sodium hydroxide solution. Extract and wash with ethyl acetate, and collect the aqueous layer. Add purified water and anhydrous methanol to the aqueous layer, adjust the pH to 3-4 with hydrochloric acid, and stir to crystallize. Filter and dry to obtain Compound III as a white solid. The reaction profiles for different condensation reagents are shown in Table 1.

[0047] Table 1 Reaction results of compound III prepared by using different condensation reagents

[0048]

[0049] Conclusion: The results show that the use of EDC·HCl as a condensation reagent is simple to post-process and has a higher yield.

[0050] Example 2

[0051] Toluene (2000 mL), compound III (100 g), and thionyl chloride (64 mL) were added to a reactor, and the reaction was stirred at 70-80°C for 39-40 hours. The temperature was lowered to -5-0°C, and a mixed solution of compound IV (140 g) and N,N-diisopropylethylamine (107 g) was added dropwise. After addition, the reaction was stirred at -5-5°C for 1-1.5 hours. Dichloromethane (400 mL) was added dropwise, and the reaction was stirred at -5-5°C for 15-16 hours. After the addition, the temperature was raised to 10-30°C, and the reaction was stirred for 15-16 hours. After the reaction, purified water and dichloromethane were added sequentially for extraction. The organic phase was washed with sodium dihydrogen phosphate solution, and hydrochloric acid was added to adjust the pH to 3-4. The layers were separated, and the aqueous layer was collected. After the aqueous layer was washed with ethyl acetate, dichloromethane was added, and potassium carbonate solution was added to adjust the pH to 9-10. The organic layer was collected and dried over anhydrous sodium sulfate. The residue was concentrated under reduced pressure to obtain compound V (65 g) as a yellow oil, which was determined by HPLC to have compound Ia accounting for 62.78% and compound Ib accounting for 37.22%.

[0052] Example 3

[0053] Toluene (2000 mL), compound III (100 g), and thionyl chloride (64 mL) were added to a reactor, and the reaction was stirred at 70–80°C for 39–40 hours. The temperature was then lowered to -5–0°C, and a mixture of compound IV (140 g) / N,N-diisopropylethylamine (107 g) / dichloromethane (400 mL) was added dropwise. After the addition, the temperature was raised to 10–30°C, and the reaction was stirred for 15–16 hours. After the reaction, purified water and dichloromethane were added sequentially for extraction. The organic phase was washed with sodium dihydrogen phosphate solution, and the pH was adjusted to 3–4 with hydrochloric acid. The layers were separated, and the aqueous layer was collected. After washing with ethyl acetate, dichloromethane was added, and the pH was adjusted to 9–10 with potassium carbonate solution. The organic layer was collected and dried over anhydrous sodium sulfate. The mixture was concentrated under reduced pressure to yield compound V (60 g) as a yellow oil. HPLC analysis showed that compound Ia accounted for 53.97% and compound Ib accounted for 46.03%.

[0054] Example 4

[0055] Acetone (200 mL) and compound V (50 g) were added to a reaction flask. The temperature was maintained at 15-30°C and stirred for 15-20 minutes. D-(+)-dibenzoyltartaric acid anhydrate (16.4 g) and purified water (200 mL) were added and the reaction was stirred at 15-30°C for 18-19 hours. The mixture was filtered, the filter cake collected, and dried to obtain compound VI-1 (50 g). Acetone (150 mL), compound VI-1 (50 g), and purified water (150 mL) were added to the reaction flask. The mixture was stirred at 40-50°C for 30-60 minutes. The mixture was then cooled and stirred at 10-20°C for 3-3.5 hours to allow crystallization. The mixture was filtered, the filter cake collected, and dried to obtain compound VI-1 (45 g). After repeating the beating process four times, compound VI (27 g) was weighed with a purity of 98% and an isomer content of 2%.

[0056] Example 5

[0057] To a reaction flask, add dichloromethane (450 mL), compound VI (30 g), and purified water (450 mL). Sodium hydroxide solution was added to adjust the pH to 9-10. The layers were separated, and the organic layer was collected, washed with sodium chloride solution, and dried over anhydrous sodium sulfate. Filter and concentrate under reduced pressure until the remaining material in the kettle (50-100 L) remained. Transfer the solution to a 50-L rotary evaporator, control the water bath temperature at 40-50°C, and concentrate under reduced pressure to obtain 20 g. Add acetonitrile (30 mL) to the reaction flask, control the temperature at 40-50°C, and dissolve for 20-30 minutes. Cool to -5-5°C, and add isopropyl ether (100 mL) dropwise. After addition, stir and crystallize at -5-5°C for 3-3.5 hours. Filter and dry to obtain compound VII (16 g) as a white solid with a three-step molar yield of 19%. HPLC analysis revealed a purity of 99.92%, with 0.33% isomers.

[0058] Example 6

[0059] Compound VII (100 g), fumaric acid (24 g), and various solvents were added to a reaction flask. Stir in a water bath at 65-75°C for 1-2 hours. The temperature was then lowered to 0-10°C and stirred for 3-4 hours to allow crystallization. Filter and dry to obtain Compound I as a white solid.

[0060] Table 2 Effect of different solvents on the crystallization of compound I

[0061]

[0062] Conclusion: Compound I obtained by recrystallization from methanol / n-heptane has high yield, high purity, good homogeneity, and low solvent usage, making it more suitable for industrial production.

Claims

1. A method for preparing 9-[(R)-2-[[(S)-[[[1-(isopropoxycarbonyl)-1-methyl]ethyl]amino]phenoxyphosphinyl]methoxy]propyl]adenine fumarate of the compound of formula (I), characterized in that: The following steps are involved: a. The compound of formula (II) reacts with phenol under condensation reagent conditions to obtain the compound of formula (III), ， b. The compound of formula (III) reacts with an acyl chloride reagent to obtain a compound of formula (III-1), and the compound of formula (III-1) and the compound of formula (IV) undergo condensation reaction to obtain a compound of formula (V). ， c. The compound of formula (V) is salified with D-(+)-dibenzoyltartaric acid anhydrate and then resolved to obtain the compound of formula (VI). ， d. The compound of formula (VI) is freed under alkaline conditions and then crystallized to obtain the compound of formula (VII). ， e. The compound of formula (VII) is salified with fumaric acid in an organic solvent to obtain the compound of formula (I), ； in: The condensation reagent described in step a is EDC·HCl; In step b, when compound (III-1) reacts with (IV), the specific preparation method is to first add a mixed solution of compound (IV) / N,N-diisopropylethylamine, and then dropwise add dichloromethane; The organic solvent in step e is a mixed solvent of n-heptane / anhydrous methanol.

2. The preparation method according to claim 1, characterized in that In step a, the reaction solvent is 1-methyl-2-pyrrolidone, the reaction temperature is 85-95° C., the reaction time is 15-16 hours, and the molar ratio of compound (II), condensation reagent, and phenol is 1:1.5:1.5-1:3.0:2.

5.

3. The preparation method according to claim 1, characterized in that In step a, the molar ratio of compound (II), condensation reagent, and phenol is 1:2:

2.

4. The preparation method according to claim 1, characterized in that In step b, the acyl chloride reagent is thionyl chloride, the solvent used is toluene, the reaction time of compound (III) and thionyl chloride is 39-40 hours, and the reaction temperature of compound (III) and thionyl chloride is 70-80°C.

5. The preparation method according to claim 1, characterized in that In step b, the reaction temperature of compound (III-1) and (IV) is -5 to 5°C, and the molar ratio of compound (III-1) to (IV) is 1:3.

5.

6. The preparation method according to claim 1, characterized in that The solvent used in step c is an acetone / water mixed solvent, wherein the acetone / water ratio is 1:

1.

7. The preparation method according to claim 1, characterized in that The solvent used for crystallization in step d is a mixed solvent of acetonitrile / isopropyl ether, and the ratio of compound (VI) / acetonitrile / isopropyl ether used is 1 g:1.5 L:5 L.

8. The preparation method according to claim 1, characterized in that The reaction solvent used for the alkaline reaction in step d is dichloromethane.

9. The preparation method according to claim 1, characterized in that The ratio of n-heptane to anhydrous methanol in the mixed solvent in step e is 1:

4.

10. The preparation method according to claim 1, characterized in that The steps include: a. Compound (II), phenol, and a condensing agent are added to an aprotic solvent, and the reaction is carried out at a temperature of 85-95°C. The reaction is monitored until completion to obtain compound (III); b. Compound (III) and thionyl chloride are added to a highly soluble solvent and the temperature is controlled to 70-80°C for reaction. After the reaction is completed, compound (III-1) is obtained. Compound (III-1) is subjected to a condensation reaction with compound (IV) to obtain compound (V); c. Compound (V) is salified with D-(+)-dibenzoyltartaric acid anhydrate and then resolved in an acetone / water mixed solvent to obtain compound (VI); d. Adding compound (VI) to an aprotic polar solvent, adding an inorganic base, and after the dissociation is complete, crystallizing from an organic solvent to obtain compound (VII); e. Compound (VII) is reacted with fumaric acid in an organic solvent to form a salt to obtain a compound of formula (I).

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