Synthetic method of medical intermediate PMO-G (N2-iBu)

Abstract

The invention relates to a synthetic method of a medical intermediate PMO-G (N2-iBu). N2-iBu-G is selected as a raw material, specific raw materials, reactants, a catalyst and a solvent are designed, a specific process route is designed, the target product PMO-G (N2-iBu) is efficiently synthesized in one step, the preparation process of the target product is simplified, and industrial popularization is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of nucleotide synthesis, and particularly relates to a method for synthesizing a pharmaceutical intermediate PMO-G(N2-iBu). Background Art

[0002] Morpholino antisense oligonucleotides (PMO Anti-sense Oligos, abbreviated as MO) are a special type of DNA / RNA analogs. Their structural feature is that the pentose ring on the traditional nucleotide is replaced by a morpholine ring, and at the same time, the phosphate group is also changed, making the whole molecule uncharged. This structure endows MO with high stability and anti-degradation ability, enabling it to play a role in the organism for a long time.

[0003] Morpholino antisense oligonucleotides are mainly synthesized from four morpholino nucleosides: morpholino adenosine (A), thymine (T), guanosine (G), and cytosine (C). That is, morpholino guanosine (G) is one of the important components for synthesizing morpholino antisense oligonucleotides. However, its synthesis process is relatively complex. The main reason is that guanosine has many active sites, resulting in poor selectivity of protecting groups and a relatively complex protection strategy. In nucleoside synthesis, the selection and removal of protecting groups are key steps. Improper protecting groups may lead to side reactions or be difficult to remove, thus affecting the purity and activity of the final product.

[0004] Morpholino antisense oligonucleotides (MO) have important applications in gene function research and gene therapy. To construct a complete MO sequence, it is necessary to be able to efficiently synthesize all four morpholino nucleosides (A, T, G, C). Therefore, it is essential to develop a synthesis method for a series of derivatives of morpholino guanosine (G). Summary of the Invention

[0005] To solve the above problems, the present application provides a new idea for synthesizing the pharmaceutical intermediate PMO-G(N2-iBu).

[0006] To achieve the above object, the present application is implemented through the following scheme: The present application provides a method for synthesizing a pharmaceutical intermediate PMO-G(N2-iBu), comprising the following steps: S1. Place N2-iBu-G in a first reaction vessel, add methanol and pure water, stir well, then add triphenylmethylamine, acetic acid, and sodium periodate to the first reaction vessel, stir well, mix evenly, react at room temperature for a first preset time, precipitate a first white solid, obtain a first mixed solution containing the first white solid, filter the first mixed solution, and obtain a first filtrate; S2. Place the first filtrate in the second reaction vessel, then add sodium cyanoborohydride to the second reaction vessel, stir well, mix evenly, stir and react for a second preset time under the temperature condition of 10°C to 20°C, return to room temperature, continue to stir and react for a third preset time. After monitoring that the reaction is complete, a second mixed solution is obtained. S3. Pour the second mixed solution into water, continuously stir, precipitate a second white solid, collect the second white solid, and obtain a filter cake formed by the second white solid. Dissolve the filter cake with dichloromethane, separate the organic phase, add sodium sulfate to the organic phase to obtain a suspension, filter the suspension to obtain a second filtrate, and vacuum dry the second filtrate in a water bath at 35°C to 45°C to obtain a third white solid. S4. Perform first column chromatography purification on the third white solid to obtain a fourth white solid, and the fourth white solid is PMO-G(N2-iBu).

[0007] As a further improvement of the present application, in step S1, the volume molar ratio of N2-iBu-G to methanol is 0.1 mol / L to 0.3 mol / L.

[0008] As a further improvement of the present application, in step S1, the molar ratio of N2-iBu-G to triphenylmethylamine is 0.5 to 0.8.

[0009] As a further improvement of the present application, in step S1, the molar ratio of N2-iBu-G to sodium periodate is 0.9 to 1.3.

[0010] As a further improvement of the present application, in step S1, the volume molar ratio of N2-iBu-G to acetic acid is 26 mol / L to 30 mol / L.

[0011] As a further improvement of the present application, in step S2, the molar ratio of N2-iBu-G to sodium cyanoborohydride is 0.2 to 0.5.

[0012] As a further improvement of the present application, N2-iBu-G is prepared by the following steps: Add guanosine and pyridine to the third reaction vessel, stir well, cool down to 4°C to 6°C, add trimethylchlorosilane, stir well again, and stir and react for a fourth preset time. Add isobutyryl chloride. After monitoring that the reaction is complete, quench the reaction, concentrate, and perform second column chromatography purification to obtain a pale yellow solid, and the pale yellow solid is N2-iBu-G.

[0013] As a further improvement of the present application, the volume molar ratio of guanosine to pyridine is 0.1 mol / L to 0.2 mol / L.

[0014] As a further improvement of the present application, the volume molar ratio of guanosine to trimethylchlorosilane is 0.8 mol / L to 1.2 mol / L.

[0015] As a further improvement of the present application, the molar ratio of guanosine to isobutyryl chloride is 0.8 to 1.2.

[0016] The beneficial effect of the present application is that a new specific process route for synthesizing PMO-G(N2-iBu) is designed. Compared with the existing synthesis of PMO-G(N2-iBu), the process route is simplified, which is conducive to industrial promotion. Description of the Drawings

[0017] Figure 1 1H NMR spectrum of the pharmaceutical intermediate PMO-G(N2-iBu) prepared in Example 1; Figure 2 HPLC spectrum of the pharmaceutical intermediate PMO-G(N2-iBu) prepared in Example 1; Figure 3 1H NMR spectrum of the pharmaceutical intermediate N2-iBu-G prepared in Example 2; Figure 4 HPLC spectrum of the pharmaceutical intermediate N2-iBu-G prepared in Example 2. Detailed Embodiments

[0018] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with specific embodiments of the present application and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments, and are not used to limit the scope of the present invention. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0019] To solve the above technical problems, the present application provides a new idea for synthesizing the pharmaceutical intermediate PMO-G(N2-iBu), which includes the following steps: A method for synthesizing a pharmaceutical intermediate PMO-G(N2-iBu) (full name: Morpholino-G(N2-iBu)), which includes the following steps: S1. Place N2-iBu-G (fully named: N2-iBu-Guanosine) in the first reaction vessel, add methanol and pure water, stir well, then add triphenylmethylamine, acetic acid, and sodium periodate to the first reaction vessel, stir well to mix evenly, react at room temperature for the first preset time, precipitate the first white solid, obtain the first mixed solution containing the first white solid, filter the first mixed solution, and obtain the first filtrate; S2. Place the first filtrate in the second reaction vessel, then add sodium cyanoborohydride to the second reaction vessel, stir well to mix evenly, stir and react at a temperature of 10°C to 20°C for the second preset time, return to room temperature, continue to stir and react for the third preset time, and after monitoring that the reaction is complete, obtain the second mixed solution; S3. Pour the second mixed solution into water, continuously stir, precipitate the second white solid until the amount of the second white solid no longer increases, collect the second white solid, and obtain the filter cake formed by the second white solid. Dissolve the filter cake with dichloromethane, separate the organic phase, add sodium sulfate to the organic phase to obtain a suspension, filter the suspension to obtain the second filtrate, and vacuum-dry the second filtrate in a water bath at 35°C to 45°C to obtain the third white solid; S4. Perform first column chromatography purification on the third white solid to obtain the fourth white solid, and the fourth white solid is PMO-G(N2-iBu).

[0020] It should be noted that the first preset time period is set according to the amounts of N2-iBu-G, methanol, triphenylmethylamine, acetic acid, and sodium periodate participating in the reaction, and takes the complete mixing and reaction of N2-iBu-G, methanol, triphenylmethylamine, acetic acid, and sodium periodate as the cut-off point, and can be but not limited to 5 min to 1 h, etc. Preferably, it can be but not limited to 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc.; the second preset time period is set according to the amounts of the first filtrate and sodium cyanoborohydride participating in the reaction, and can be but not limited to 1 h to 5 h, etc. Preferably, it can be but not limited to 1 h, 2 h, 3 h, 4 h, 5 h, etc.; the third preset time period is also set according to the amounts of the first filtrate and sodium cyanoborohydride participating in the reaction, and takes the complete reaction of the first filtrate and sodium cyanoborohydride as the cut-off point, and can be but not limited to 10 h to 20 h, etc. Preferably, it can be but not limited to 10 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, etc.

[0021] In an alternative embodiment, in step S1, the volume molar ratio of N2-iBu-G to methanol is 0.1 mol / L to 0.3 mol / L, the molar ratio of N2-iBu-G to triphenylmethylamine is 0.5 to 0.8, the molar ratio of N2-iBu-G to sodium periodate is 0.9 to 1.3, and the volume molar ratio of N2-iBu-G to acetic acid is 26 mol / L to 30 mol / L. In step S2, the molar ratio of N2-iBu-G to sodium cyanoborohydride is 0.2 to 0.5.

[0022] The technical route for synthesizing the pharmaceutical intermediate PMO-G(N2-iBu) of the present application is as follows in Formula I: Formula I.

[0023] In the technical solution of the present application: By screening specific raw materials, solvents, catalysts and other components and designing a specific process route, the pharmaceutical intermediate - PMO-G(N2-iBu) is synthesized through a one-step reaction process: N2-iBu-G serves as the starting material to provide the core structure; methanol serves as the solvent to dissolve the reactants and facilitate the progress of the reaction; pure water is used to adjust the polarity of the reaction system and promote the progress of the reaction; triphenylmethylamine serves as a nucleophile to introduce a triphenylmethyl protecting group, and the nucleophilicity of triphenylmethylamine can react with the aldehyde group oxidized by sodium periodate; acetic acid serves as an acidic catalyst to provide an acidic environment, which is beneficial to the oxidation of the aldehyde group and subsequent nucleophilic addition reactions, and promotes the progress of the reaction; sodium periodate (NaIO 4 ) serves as an oxidant to selectively oxidize the aldehyde group to a carboxyl group, providing an active site for subsequent nucleophilic addition reactions; sodium cyanoborohydride (NaBH 3 CN) serves as a reducing agent to reduce the imine formed by the reduction of the aldehyde group and the amino group to form a stable product.

[0024] The specific reaction principle of the present application is as follows: N2-iBu-G is first oxidized by sodium periodate in a mixed solvent of methanol and pure water to form an aldehyde group intermediate; subsequently, triphenylmethylamine undergoes a nucleophilic addition reaction with the aldehyde group under the catalysis of acetic acid to form an imine intermediate; finally, sodium cyanoborohydride reduces the imine to a stable product to obtain PMO-G(N2-iBu). The reactions of the technical solution of the present application are all carried out at room temperature or below room temperature. The low-temperature reaction can avoid side reactions caused by high temperature and ensure the smooth progress of the reaction.

[0025] In an alternative embodiment, the N2-iBu-G is prepared by the following steps: Add guanosine and pyridine into a third reaction vessel, stir well, cool down to 4 - 6 °C, add trimethylchlorosilane, stir well again, return to room temperature (25 °C ± 5 °C), and react for a fourth preset time under room temperature conditions. Then add isobutyryl chloride, stir well, return to room temperature (25 °C ± 5 °C), and react for a fifth preset time under room temperature conditions. After monitoring the completion of the reaction, quench the reaction, concentrate, and purify by second column chromatography to obtain a pale yellow solid, which is N2-iBu-G.

[0026] It should be noted that the fourth preset time period is set according to the amounts of guanosine, pyridine, and trimethylchlorosilane participating in the reaction, and is terminated when guanosine, pyridine, and trimethylchlorosilane are fully mixed and reacted. It can be, but is not limited to, 10 h - 20 h, etc. Preferably, it can be, but is not limited to, 10 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, etc.; The fifth preset time period is set according to the amount of isobutyryl chloride participating in the reaction, and is terminated when isobutyryl chloride is fully reacted. It can be, but is not limited to, 1 h - 5 h, etc. Preferably, it can be, but is not limited to, 1 h, 2 h, 3 h, 4 h, 5 h, etc.

[0027] In an alternative embodiment, the volume molar ratio of the guanosine to the pyridine is 0.1 mol / L - 0.2 mol / L, the volume molar ratio of the guanosine to the trimethylchlorosilane is 0.8 mol / L - 1.2 mol / L, and the molar ratio of the guanosine to the isobutyryl chloride is 0.8 - 1.2.

[0028] For N2-iBu-G, the present application is synthesized through the following technical route of Formula II: Formula II, In the synthesis of N2-iBu-G, guanosine is used as the starting material to provide the core purine base structure. Pyridine is used as a catalyst to promote the reaction. Trimethylchlorosilane (TMSCl) is used as a protecting reagent to protect the 2, 3, and 4 positions of the sugar ring of guanosine and the O4 position of the purine ring. TMSCl reacts with the N2 position of guanosine to form a trimethylsilyl-protected intermediate, providing a stable structure for subsequent reactions. Isobutyryl chloride (iBuCl) is used as an acylating reagent to introduce an isobutyryl group into the N2 position of guanosine. Isobutyryl chloride undergoes an acylation reaction with the N2 position of guanosine under the catalysis of pyridine to form an N2-isobutyryl-protected guanosine intermediate (N2-iBu-G). Ammonia water is used to remove the protecting TMS group.

[0029] The reaction principle of N2-iBu-G synthesis is as follows: Under low temperature conditions of 4-6 °C, guanosine reacts with trimethylchlorosilane, and the N2 position is protected by trimethylsilyl. Subsequently, isobutyryl chloride is added, and under the catalysis of pyridine, the trimethylsilyl group at the N2 position is replaced by an isobutyryl group to form an intermediate of N2-isobutyryl-protected guanosine. After the reaction is completed, water or concentrated ammonia water is added to quench the reaction and remove the protecting group to obtain N2-iBu-G. The low temperature conditions of 4-6 °C help control the reaction rate, prevent side reactions from occurring, and improve the selectivity of the reaction.

[0030] To verify the feasibility and excellent effects of the technical solution of this application, the following examples are provided as evidence. Among them, the sources of the raw materials used in the examples are as follows: Guanosine is a product with batch number 20081303 produced by Wuhu Huaren Technology Co., Ltd., trimethylchlorosilane is a product with batch number P2283031 produced by Shanghai Titan Technology Co., Ltd., isobutyryl chloride is a product with batch number P2676302 produced by Shanghai Titan Technology Co., Ltd., pyridine is a product with batch number 20230614 produced by Sinopharm Chemical Reagent Co., Ltd., concentrated ammonia water is a product with batch number P2416834 produced by Shanghai Titan Technology Co., Ltd., sodium periodate is a product with batch number P2680477 produced by Shanghai Titan Technology Co., Ltd., triphenylmethylamine is a product with batch number P2217520 produced by Shanghai Titan Technology Co., Ltd., sodium cyanoborohydride is a product with batch number P2512762 produced by Shanghai Titan Technology Co., Ltd., and methanol is a product with batch number 20230711 produced by Jiangsu Qiangsheng Functional Chemical Co., Ltd., Baimao Branch.

[0031] Example 1 The specific steps for synthesizing the pharmaceutical intermediate PMO-G(N2-iBu) in this example are as follows: First, add 50.3 g (0.14 mol, 1.00 eq) of N2-iBu-G into the first reaction vessel, add 750 ml of methanol and 250 ml of pure water, stir well, then add 56 g (0.21 mol, 1.50 eq) of triphenylmethylamine, 5 ml of acetic acid, and 45 g (0.12 mol, 1.50 eq) of sodium periodate into the first reaction vessel, stir well, mix evenly, and stir and react at room temperature (25 °C ± 5 °C) for 40 min. A first white solid slowly precipitates to obtain a first mixed solution containing the first white solid. Filter the first mixed solution to obtain a first filtrate; Secondly, place the first filtrate into a second reaction vessel, and place the second reaction vessel in an ice-water bath. Cool down to 15 °C, and add 13 g (0.42 mol, 3.00 eq) of sodium cyanoborohydride to the second reaction vessel containing the first filtrate. Under the temperature condition of 15 °C ± 5 °C, stir the reaction thoroughly for 3 h, and then let it warm up to room temperature (25 °C ± 5 °C) naturally. Continue to stir the reaction for 16 h. After monitoring that the reaction is complete, a second mixed solution is obtained. Thirdly, pour the second mixed solution into water, and keep stirring continuously to precipitate a second white solid until the amount of the second white solid no longer increases. Collect the second white solid and obtain a filter cake formed by the second white solid. Dissolve the filter cake with 300 ml of dichloromethane, separate the organic phase, add sodium sulfate to the organic phase to obtain a suspension, filter the second suspension to obtain a second filtrate, and dry the second filtrate under vacuum in a water bath at 35 °C - 45 °C to obtain a third white solid. Finally, perform the first column chromatography purification on the third white solid to obtain 9 g of a fourth white solid, and the fourth white solid is PMO-G(N2-iBu). Among them, the first column chromatography purification is carried out by the process of gradient washing. The eluent used is a mixed solution of methanol (MeOH) and dichloromethane (DCM), and its ratio starts from pure dichloromethane (0% methanol, 100% dichloromethane), and gradually increases the proportion of methanol, in turn: 0% methanol, 100% dichloromethane; 1% methanol, 99% dichloromethane; 2% methanol, 98% dichloromethane; 5% methanol, 95% dichloromethane; 10% methanol, 90% dichloromethane.

[0032] The 1H NMR nuclear magnetic resonance spectrum and HPLC spectrum of the pharmaceutical intermediate PMO-G(N2-iBu) prepared in this example are shown in Figure 1 and Figure 2 respectively. The analysis data of the 1H NMR spectrum are as follows: 1H NMR (400 MHz, CDCl3) δ 13.06 (s, 1H), 11.96 (s, 1H), 8.62 (s, 1H), 7.66 – 6.85 (m, 15H), 5.95 (s, 1H), 4.33 (s, 1H), 3.63 (s, 2H), 3.39 (d, J = 11.3 Hz, 1H), 3.12 (d, J = 11.9 Hz, 1H), 1.58 – 1.22 (m, 6H).

[0033] Example 2 This example gives the synthesis process of N2-iBu-G, which is as follows: 100 g (353 mmol, 1.00 eq) of guanosine and 2.5 L of pyridine were added into the third reaction vessel and stirred thoroughly. The third reaction vessel was placed in an ice-water bath and cooled to 5 °C. 330 mL of trimethylchlorosilane (TMSCl) was added and stirred again thoroughly. The reaction was stirred for 16 h. The third reaction vessel was placed in the ice-water bath again and cooled to 5 °C. 42 g (388 mmol, 1.10 eq) of isobutyryl chloride (iBuCl) was added. After stirring, the solution was allowed to warm to room temperature (25 °C ± 5 °C) naturally and stirred for 3 h. After monitoring the completion of the reaction, the quenching reaction, concentration, and second column chromatography purification were carried out to obtain 90 g of a pale yellow solid, and the pale yellow solid is N2-iBu-G.

[0034] The specific steps of the quenching reaction are as follows: The third reaction vessel was placed in the ice-water bath again and cooled to 9 °C (±5 °C). 400 mL of water was added into the third reaction vessel and stirred at 9 °C (±5 °C) for 1 h. Then 400 mL of concentrated ammonia water was added into the third reaction vessel. The temperature of the solution rose during the dropping process. The temperature was kept below 20 °C. After the addition was completed, it was stirred at 20 °C (±5 °C) for 1 h.

[0035] In the second column chromatography purification, gradient washing was used for the second column chromatography purification. The washing solution (eluent) used was a mixed solution of methanol (MeOH) and dichloromethane (DCM). The ratio started from pure dichloromethane (0% methanol, 100% dichloromethane) and gradually increased the proportion of methanol, in turn: 0% methanol, 100% dichloromethane; 1% methanol, 99% dichloromethane; 2% methanol, 98% dichloromethane; 5% methanol, 95% dichloromethane; 10% methanol, 90% dichloromethane.

[0036] The 1H NMR nuclear magnetic resonance spectrum and HPLC spectrum of the pharmaceutical intermediate N2-iBu-G prepared in this example are shown in Figure 3 and Figure 4 respectively. The analysis data of the 1H NMR spectrum are as follows: 1H NMR (400 MHz, DMSO) δ 12.08 (s, 1H), 11.68 (s, 1H), 8.26 (s, 1H), 5.81 (d, J = 5.8 Hz, 1H), 5.75 (s, 1H), 5.62 – 4.79 (m, 2H), 4.43 (t, J = 5.4 Hz, 1H), 4.12 (t, J = 4.2 Hz, 1H), 3.90 (q, J = 4.0 Hz, 1H), 3.71 – 3.46 (m, 2H), 2.77 (hept, J = 6.7 Hz, 1H), 1.12 (d, J = 6.8 Hz, 6H).

[0037] Comparative Example 1 To demonstrate that the technical solution of the present application has excellent technical effects, this comparative example is provided. The technical route for preparing PMO-G(N2-iBu) in the prior art is as shown in Formula III: III, In the first step, using guanosine as the starting material, the reaction is carried out by adding tert-butyldiphenylchlorosilane (TBDPSCl), triethylamine, 4-dimethylaminopyridine (DMAP), dichloromethane, and DMF to achieve the protection of the TBS group and obtain the first intermediate product (G1). The reaction principle is that TBDPSCl acts as an electrophilic reagent and undergoes an electrophilic substitution reaction with the hydroxyl group of guanosine. Triethylamine acts as an acid-binding agent to neutralize the generated acid, DMAP acts as a catalyst to accelerate the reaction, and dichloromethane and DMF act as solvents.

[0038] In the second step, using the first intermediate product as the raw material and sodium periodate as the oxidant, the hydroxyl group in the glycoside part is oxidized to an aldehyde group; ammonium borate tetrahydrate is used as the ammonia source to prevent over-oxidation. Subsequently, sodium cyanoborohydride is used as the reducing agent to reduce the imine to ammonia, and 4A molecular sieve is used to adsorb moisture to ensure the smooth progress of the reaction. Acetic acid is used to adjust the reaction environment to promote the reductive amination reaction. Finally, through filtration, extraction, drying, and column chromatography purification, the second intermediate product (G2) is obtained.

[0039] In the third step, using the second intermediate product as the raw material, it is dissolved in N,N-dimethylformamide (DMF), cooled to 0 °C, and then triethylamine (acid-binding agent) is added, followed by the addition of triphenylchloromethane (protecting group). Triethylamine neutralizes the acid generated in the reaction and promotes the nucleophilic substitution reaction between triphenylchloromethane and the second intermediate product to protect the amino group in the second intermediate product. After the reaction is completed, it is quenched with methanol to terminate the reaction. The crude product is diluted with ethyl acetate, washed with water and saturated brine, the organic phase is separated and dried with sodium sulfate, and finally purified by silica gel column chromatography to obtain the third intermediate product (G3).

[0040] In the fourth step, the third intermediate is used as a raw material. After dissolving it in DMF, isobutyric anhydride is added as an acylating agent, and triethylamine is used as an acid-binding agent to neutralize the acid generated in the reaction, promoting the progress of the acylation reaction. The reaction is carried out at 140 °C, and isobutyric anhydride and triethylamine are added midway to ensure complete reaction. After the reaction solution is concentrated under reduced pressure, the crude product is dissolved in chloroform, washed with water, saturated sodium bicarbonate solution and saturated brine, the organic phase is separated and dried with sodium sulfate, and finally the acylated product, that is, the fourth intermediate (G4), is obtained.

[0041] In the fifth step, the fourth intermediate is used as a raw material. After dissolving it in dry tetrahydrofuran, a solution of tetrabutylammonium fluoride (TBAF) is added dropwise. TBAF, as a fluoride ion source, undergoes a nucleophilic substitution reaction with the TBS protecting group in the fourth intermediate to remove the TBS protecting group and restore the active hydroxyl group. The reaction is completed by stirring at room temperature. After the reaction solution is concentrated, the crude product is diluted with ethyl acetate, washed with water and saturated brine, the organic phase is separated and dried with sodium sulfate, and finally the deprotected product, that is, PMO-G(N2-iBu), is obtained.

[0042] In this comparative example, guanosine is used as the starting material and PMO-G(N2-iBu) is obtained through 5 steps of reaction. The preparation process is cumbersome, time-consuming and laborious.

[0043] In summary, compared with the prior art, the present application selects the pharmaceutical intermediate N2-iBu-G as the raw material, and through designing specific raw materials, reactants, catalysts, solvents, and designing a specific process route, the target product PMO-G(N2-iBu) is efficiently synthesized in one step, with high purity and high yield, and is conducive to industrial promotion.

[0044] Although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0045] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing a pharmaceutical intermediate PMO-G (N2-iBu), characterized in that: The steps include: S1, placing N2-iBu-G in a first reaction container, adding methanol and pure water, stirring thoroughly, then adding triphenylamine, acetic acid, and sodium periodate into the first reaction container, stirring thoroughly, mixing evenly, reacting at room temperature, precipitating a first white solid, obtaining a first mixed solution containing the first white solid, filtering, and obtaining a first filtrate; S2, placing the first filtrate in a second reaction container, adding sodium cyanoborohydride to the second reaction container, stirring thoroughly, mixing evenly, stirring the mixture at 10°C to 20°C, returning to room temperature, continuing to stir the mixture, and monitoring the reaction until it is complete, to obtain a second mixed solution; S3, pouring the second mixed solution into water, stirring continuously, precipitating a second white solid, collecting the second white solid, and obtaining a filter cake formed by the second white solid, dissolving the filter cake with dichloromethane, separating an organic phase, and adding sodium sulfate to the organic phase to obtain a suspension, filtering the suspension to obtain a second filtrate, and vacuum drying the second filtrate in a water bath at 35° C. to 45° C. to obtain a third white solid; S4. Purify the third white solid by a first column chromatography to obtain a fourth white solid, wherein the fourth white solid is PMO-G (N2-iBu).

2. The synthesis method according to claim 1, characterized in that In step S1, the volume molar ratio of the N2-iBu-G to the methanol is 0.1 mol / L to 0.3 mol / L.

3. The synthesis method according to claim 1, characterized in that In step S1, the molar ratio of the N2-iBu-G to the triphenylamine is 0.5 to 0.

8.

4. The synthesis method according to claim 1, characterized in that In step S1, the molar ratio of the N2-iBu-G to the sodium periodate is 0.9 to 1.

3.

5. The synthesis method according to claim 1, characterized in that In step S1, the volume molar ratio of the N2-iBu-G to the acetic acid is 26 mol / L to 30 mol / L.

6. The synthesis method according to claim 1, characterized in that In step S2, the molar ratio of the N2-iBu-G to the sodium cyanoborohydride is 0.2 to 0.

5.

7. The synthesis method according to any one of claims 1 to 6, characterized in that The N2-iBu-G is prepared by the following steps: Guanosine and pyridine are added to the third reaction container, stirred fully, cooled to 4-6°C, trimethylsilyl chloride is added, stirred fully again, and stirred for the fourth preset time, isobutyryl chloride is added, and after monitoring the completion of the reaction, the reaction is quenched, concentrated, and purified by a second column chromatography to obtain a light yellow solid, which is N2-iBu-G.

8. The synthesis method according to claim 7, characterized in that The volume molar ratio of the guanosine to the pyridine is 0.1 mol / L to 0.2 mol / L.

9. The synthesis method according to claim 7, characterized in that: The volume molar ratio of the guanosine to the trimethylsilyl chloride is 0.8 mol / L to 1.2 mol / L.

10. The synthesis method according to claim 7, characterized in that: The molar ratio of the guanosine to the isobutyryl chloride is 0.8 to 1.2.

Images