A preparation method of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine

Abstract

The present application relates to a method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine, comprising the following steps: S1: reacting 2'-O-methyladenosine with TIPDSiCl2 in a pyridine alkaline environment; S2: reacting the product of step S1 with Boc2O through DMAP catalysis; S3: reacting the product of step S2 with iodomethane under the action of cesium carbonate to obtain intermediate 1, then removing the BOC group from intermediate 1 under the action of TFA, and removing the TIPDSi protection under the action of TBAF; S4: reacting the product of step S3 with DMTrCl in a pyridine alkaline environment to obtain N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine. The present application obtains the target product through a 4-step reaction, which is significantly shorter than the 6-step reaction steps of the prior art route, and the total yield is significantly improved.

Description

Technical Field

[0001] The present application belongs to the technical field of pharmaceutical intermediates, and in particular relates to a method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine. Background Art

[0002] Oligonucleotides have broad application prospects in cancer treatment and genetics. For example, oligonucleotides are short single-stranded DNA or RNA, usually composed of a few to dozens of nucleotides. They can bind to complementary DNA or RNA sequences to form a stable double-stranded structure. Specifically, oligonucleotides can cross-link with the internal or terminal positions of DNA or RNA in cells. This cross-linking can prevent cell replication. Therefore, oligonucleotides can be used as a special drug that binds to the DNA or RNA of cancer cells, preventing cancer cell replication and thus killing cancer cells. This treatment method is called gene targeted therapy because it targets specific gene mutations rather than all healthy or diseased cells.

[0003] In genetics, oligonucleotides are often used as probes to study the structure and function of DNA and RNA. They can also be used in gene therapy, which involves modifying DNA or RNA sequences to treat genetic diseases. In this process, oligonucleotides can be designed to bind to abnormal gene sequences, thereby preventing the expression of harmful genes.

[0004] RNAi is a common mechanism for regulating gene expression in organisms, inhibiting the expression of specific genes by degrading target RNA. In the RNAi process, double-stranded RNA (dsRNA) is a key effector molecule. It can be cleaved into multiple small fragments by the cellular enzyme RNase III, known as siRNA (small interfering RNA). siRNA can bind to the target RNA, causing its degradation and thereby inhibiting the expression of a specific gene.

[0005] During siRNA synthesis, the 2' position is a crucial modification site. Chemical groups (such as methyl and ethyl groups) can be added to alter the siRNA's physicochemical properties and functionality. These modifications can increase siRNA stability and specificity, enabling it to more effectively bind to target RNA and thereby inhibit specific gene expression. Sugar-modified oligonucleotides are particularly important for altering siRNA's physicochemical properties and functionality. For example, sugar-modified oligonucleotides can activate the 2'-deoxy-erythro-pentofuranosyl nucleoside subsequence of RNase H, thereby promoting the degradation of target nucleic acids.

[0006] 2'-O-Methyladenosine (2'-O-Methyladenosine) is an adenine residue with unique biological activity. It can be detected in the urine of healthy individuals and patients with adenosine deaminase deficiency and exhibits significant antihypertensive activity. Furthermore, 2'-O-Methyladenosine plays a crucial role in the formation of the mRNA cap structure. When the first transcribed nucleotide is 2'-O-methyladenosine, it can be further modified to N6,2'-O-dimethyladenosine (m6Am). This modification helps regulate mRNA binding to proteins and participates in various other biological processes. 2'-O-Methyladenosine is not only widely used in basic research but also a potential target for drug development due to its unique pharmacological effects.

[0007] N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine is an important pharmaceutical intermediate, but its preparation methods are rarely reported in domestic and international literature. Existing technology reports that the preparation of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine is generally completed from 2'-O-methyladenosine via a six-step reaction, as shown in the following reaction formula: .

[0008] The reaction formula references for the above-mentioned preparation of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine are as follows: Step A: WO2021 / 119325A1, the patent applicant is ALIGOS THERAPEUTICS INC, and the patent was published in 2021; Step B: CN115611954A, the patent applicants are Tianjin Oruifu Biotechnology Co., Ltd. and Tianjin Lianlong New Materials Co., Ltd., and the patent was published in 2023; Step CF: WO2022155418A1, the patent applicant is ALNYLAM PHARMACEUTICALS, INC. and the patent was published in 2022.

[0009] The above-mentioned process for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine comprises the following steps:

[0010] Step A: Compound 1 was dissolved in pyridine. Under nitrogen, TMSiCl was added at 0°C and the reaction was stirred at 0°C for 5 hours. Benzoyl chloride was then added at 0°C and stirred at 15°C for 2 hours. The reaction temperature was cooled to 0°C, H2O was added, and the reaction was stirred at 15°C for 0.5 hours. NH3·H2O was then added at 15°C and stirred for 2 hours. The reaction solution was concentrated under reduced pressure and stirred with DCM at 15°C for 1 hour to obtain a crude white solid. The product was then slurried with H2O at 15°C for 1 hour and filtered to obtain Compound B as a white solid (yield 88.17%).

[0011] Step B: Compound B was dissolved in pyridine and distilled under reduced pressure at 45°C until no fraction was recovered, and then pyridine was added to dissolve Compound B; DMTr-Cl and pyridine were mixed and stirred at 45°C to dissolve; the temperature of the microchannel reactor was set at 45°C, and the solution of Compound B and the solution of DMTr-Cl were added to the mixing module of the microchannel reactor at flow rates of 30 mL / min and 20 mL / min, respectively, for reaction, with a residence time of 50 s. The reaction solution and 25 mL of methanol were then added to the quenching module of the microchannel reactor at flow rates of 50 mL / min and 43 mL / min, respectively, to terminate the reaction, with a residence time of 35 s. TLC (dichloromethane:methanol = 10:1) was used to detect the completion of the reaction; the quenched reaction solution was rotary evaporated to dryness in a 45°C water bath to obtain a yellow foaming solid, which was Compound C (yield 96.8%).

[0012] Step C: Compound C was dissolved in pyridine under nitrogen protection. Imidazole and TBSCl were added at room temperature and stirred for 16 hours. The reaction solution was poured into a mixture of n-heptane, ether, and water and stirred vigorously. The white solid was filtered and dissolved in DCM. The organic phase was dried over anhydrous sodium sulfate, filtered, rinsed, and concentrated to obtain white Compound D (yield 100%).

[0013] Step D: Compound D was dissolved in dry acetonitrile, and DBU and iodomethane were added dropwise at 0°C. The mixture was stirred at room temperature for 16 hours, and concentrated under reduced pressure to obtain a crude product. The crude product was purified by column chromatography (gradient: ethyl acetate / n-heptane = 0-50%) to obtain Compound E (yield 52%).

[0014] Step E: Compound E was dissolved in THF, and TBAF (1.0 M in THF) was added at room temperature. The reaction was stirred for 2 hours. The reaction was controlled by TLC. The crude product was concentrated under reduced pressure and purified by column chromatography (gradient: ethyl acetate / n-heptane = 30-100%) to obtain Compound F as a white solid (yield 97.2%).

[0015] Step F: Compound F was dissolved in methanol, sodium methoxide (25% methanol solution) was added, and the mixture was stirred at room temperature for 8 hours. The mixture was concentrated under reduced pressure and purified by column chromatography (gradient: methanol / dichloromethane = 0-5%) to obtain Compound 5.

[0016] However, the total yield of the first five steps of the above-mentioned process for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine is only 43.1%, and the yield of the sixth step is not reported, resulting in high production costs of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine. Summary of the Invention

[0017] The technical problem to be solved by the present invention is: to solve the above-mentioned deficiencies in the prior art, thereby providing a method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine.

[0018] The technical solution adopted by the present invention to solve its technical problem is:

[0019] A method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine comprises the following steps:

[0020] S1: 2'-O-methyladenosine (compound 1) reacts with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (TIPDSiCl2) in a pyridine alkaline environment to obtain compound 2;

[0021] S2: Compound 2 is reacted with di-tert-butyl dicarbonate (Boc2O) using 4-dimethylaminopyridine (DMAP) as a catalyst to obtain compound 3;

[0022] S3: Compound 3 is reacted with iodomethane in the presence of cesium carbonate to obtain intermediate 1, and then the BOC group of intermediate 1 is removed in the presence of trifluoroacetic acid (TFA), and the TIPDSi protection is removed in the presence of tetrabutylammonium fluoride (TBAF) to generate compound 4. The structure of intermediate 1 is ;

[0023] S4: Compound 4 is reacted with 4,4'-dimethoxytrityl chloride (DMTrCl) in a pyridine alkaline environment to obtain compound 5, namely N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine;

[0024] The synthetic route of the N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine (Compound 5) is as follows: .

[0025] Preferably, in step S1, 2'-O-methyladenosine is first placed in a pyridine base environment, and then TIPDSiCl2 is added to react; and TIPDSiCl2 is further added dropwise.

[0026] Preferably, the reaction in step S1 is carried out under an inert gas environment.

[0027] Preferably, the reaction solvent of step S2 is at least one of tetrahydrofuran, dichloromethane, 1,2-dichloroethane, chloroform, toluene, and ethyl acetate.

[0028] Preferably, after step S2, a Boc group of the by-product 1 is removed by aminolysis to generate compound 3, wherein the structure of the by-product 1 is .

[0029] Preferably, in step S3, the reaction solvent for the reaction of compound 3 with iodomethane under the action of cesium carbonate is N,N-dimethylformamide and / or dimethyl sulfoxide, the reaction solvent for removing the BOC group under the action of trifluoroacetic acid (TFA) is at least one of dichloromethane, 1,2-dichloroethane, chloroform, toluene, and ethyl acetate, and the reaction solvent for removing TIPDSi protection to generate compound 4 under the action of tetrabutylammonium fluoride (TBAF) is at least one of tetrahydrofuran, acetonitrile, methanol, and ethanol.

[0030] Preferably, in step S4, compound 4 is first placed in a pyridine base environment, and then DMTrCl is added for reaction, and further DMTrCl solution is added dropwise.

[0031] Preferably, any reaction of steps S1-S4 is carried out at room temperature.

[0032] The main reaction mechanism of this application is as follows:

[0033] (1) In the alkaline environment of pyridine, the hydroxyl groups at the 3' and 5' positions of compound 1 attack TIPDSiCl2 ( ) is substituted by nucleophilic substitution to form compound 2;

[0034] (2) In DMAP ( ) catalyzed by the amine group of compound 2, which is protected by one Boc to generate compound 3, or protected by two Boc to generate by-product 1 ( ), further, the by-product 1 undergoes an ammonia decomposition reaction with ammonia to remove a Boc and regenerate compound 3;

[0035] (3) Compound 3 is exposed to the action of the hydrogen-binding reagent cesium carbonate, and the Boc-protected amine group removes a hydrogen ion, thereby attacking the methyl group of iodomethane to generate intermediate 1. The structure of intermediate 1 is Subsequently, intermediate 1 was deprotected from Boc by trifluoroacetic acid, and deprotected from TIPDSi by tetrabutylammonium fluoride to generate compound 4;

[0036] (4) Under the action of pyridine, due to the steric hindrance effect, the 5' hydroxyl group of compound 4 attacks the 4,4'-dimethoxytrityl chloride (DMTrCl) decomposed 4,4'-dimethoxytrityl carbonium ion ( ), and finally compound 5 was obtained.

[0037] The beneficial effects of the present invention are:

[0038] This application discloses for the first time a method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine (Compound 5) from 2'-O-methyladenosine (Compound 1) through a four-step reaction. Compared with the existing technical route: 1) the target product is obtained through a four-step reaction, which is significantly shorter than the six-step reaction steps of the existing technical route, simpler to operate, and lower in cost; 2) the total yield of the route reaches more than 69%, which is much greater than the yield of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine disclosed in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The technical solution of the present application is further described below with reference to the accompanying drawings and embodiments.

[0040] Figure 1 This is an HPLC chart of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine prepared in Example 4 of the present application;

[0041] Figure 2 This is the H NMR spectrum of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine prepared in Example 4 of the present application. DETAILED DESCRIPTION

[0042] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0043] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0044] The sources of the raw materials used in this application are as follows:

[0045] 2'-O-Methyladenosine (Compound 1) was produced by Tianjin Xiens Biochemical Technology Co., Ltd. with batch number 500+D080325LF02, 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (TIPDSiCl2) was produced by Tianjin Xiens Biochemical Technology Co., Ltd. with batch number 500+D0317028LF01, methanol was produced by Shanghai Lingfeng Chemical Reagent Co., Ltd. with batch number 20230405, dichloromethane was produced by Shanghai Lingfeng Chemical Reagent Co., Ltd. with batch number 20230508, di-tert-butyl dicarbonate (Boc2O) was produced by Shanghai Titan Technology Co., Ltd. with batch number P1602458, 4-dimethylaminopyridine (DMAP) was produced by Shanghai Titan Technology Co., Ltd. with batch number P2913528, and 7N ammonia in methanol was produced by Sigma-Aldrich (Shanghai) Trading Co., Ltd. with batch number 20230122. Ethyl acetate is the product of batch number 20230213 produced by Shanghai Lingfeng Chemical Reagent Co., Ltd., pyridine is the product of batch number 20230518 produced by Shanghai Lingfeng Chemical Reagent Co., Ltd., tetrahydrofuran is the product of batch number 20230316 produced by Shanghai Lingfeng Chemical Reagent Co., Ltd., N,N-dimethylformamide is the product of batch number 20230316 produced by Shanghai Lingfeng Chemical Reagent Co., Ltd., cesium carbonate is the product of batch number Q9DRRRQP produced by Anage Chemical Reagent Co., Ltd., iodomethane is the product of batch number DGE5RRAH produced by Anage Chemical Reagent Co., Ltd., trifluoroacetic acid is the product of batch number OOWERAYK produced by Anage Chemical Reagent Co., Ltd., tetrabutylammonium fluoride is the product of batch number P2986747 produced by Shanghai Titan Technology Co., Ltd., and 4,4'-bismethoxytrityl chloride (DMTrCl) is the product of batch number 240514ST01 produced by Shitong Bio. Example 1

[0046] This example provides a method for preparing compound 2, and the synthetic route is as follows:

[0047] ;

[0048] The preparation method of compound 2 comprises the following steps:

[0049] In a flask, 20 g of compound 1 was added to 150 mL of pyridine. After stirring at room temperature for 10 min, the mixture was replaced with nitrogen three times under vacuum, and 24.7 g of TIPDSiCl2 (1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane) was added dropwise. The mixture was stirred at room temperature for 3-6 h. HPLC monitoring showed that the reaction was almost complete. The reaction solution was placed in an oil pump and concentrated under reduced pressure to remove the solvent. The mixture was passed through a silica gel column (200 g, DCM:MeOH=20:0 to 20:1). The eluate was concentrated to obtain 35 g of compound 2. 1H NMR (400 MHz, DMSO) δ8.20 (s, 1H), 8.07 (s, 1H), 5.96 (s, 1H), 4.96 (dt, J = 17.3, 8.7 Hz, 1H),4.31 (t, J = 9.2 Hz, 1H), 4.05 (dd, J = 12.7, 2.0 Hz, 1H), 3.99–3.87 (m, 2H), 3.54 (s, 3H), 1.08 – 0.98 (m, 28H). The purity of compound 2 was 95.1% by HPLC, and the yield was 94.0%. Example 2

[0050] This example provides a preparation method of compound 3, and the synthetic route is as follows:

[0051] ;

[0052] The preparation method of compound 3 comprises the following steps:

[0053] In a round-bottom flask, 48 g of compound 2 was added and dissolved in 200 mL of THF. 60 g of di-tert-butyl dicarbonate (Boc2O) and 1.12 g of 4-dimethylaminopyridine (DMAP) were added and stirred overnight. The reaction was essentially complete. The reaction solution was concentrated under reduced pressure and dissolved in 200 mL of methanol. 130 mL of 7 N ammonia in methanol was added and stirred overnight. The results were monitored by HPLC. The reaction solution was concentrated under reduced pressure and mixed with 150 g of silica gel. The product was purified by column chromatography (600 g of silica gel, PE:EA = 1:0 to 5:1 to 4:1 to PE:EA:DCM = 4:1:0.5). The eluate was concentrated to give 45 g of a solid (compound 3). 1H NMR (400 MHz, DMSO) δ 10.14 (d, J = 19.1 Hz, 1H), 8.52 (s, 1H), 8.49 (s, 1H), The δ values ​​were 6.05 (s, 1H), 4.94 (dt, J = 13.5, 6.7 Hz, 1H), 4.38 (t, J = 6.8 Hz, 1H), 4.06 (d, J = 12.9 Hz,1H), 4.02 – 3.89 (m, 2H), 3.55 (s, 3H), 1.46 (d, J = 7.9 Hz, 9H), 1.09 – 0.98 (m, 28H). The purity of compound 3 was 96.3% by HPLC, and the yield was 78.7%. Example 3

[0054] This example provides a preparation method of compound 4, and the synthetic route is as follows:

[0055] ;

[0056] The preparation method of compound 4 comprises the following steps:

[0057] 20 g of compound 3 and 200 mL of DMF were added to a round-bottom flask, and the mixture was ultrasonically dissolved. 12.53 g of cesium carbonate and 6.83 g of iodomethane were added, and the mixture was stirred at room temperature for 2-4 h. The results were monitored by HPLC. The DMF was concentrated under reduced pressure, 200 mL of DCM was added, and the mixture was extracted and washed with 200 mL×3 of water. The organic phase was concentrated under reduced pressure; 200 mL of DCM was added to dissolve the mixture, and 20 mL of trifluoroacetic acid was added dropwise. The mixture was stirred at room temperature for 6 h. The intermediate was monitored by spot plate monitoring to confirm that there was basically no residue. The mixture was concentrated under reduced pressure, and the crude product was dissolved in 200 mL of DCM and concentrated again. The crude product was added to 125 mL of THF solution to dissolve the mixture, and 125 mL of 1 N tetrabutylammonium fluoride in tetrahydrofuran solution was added. The mixture was stirred at room temperature overnight and the results were monitored by HPLC. After the product was qualified, it was concentrated under reduced pressure, and the concentrate was dissolved in 300 ml of dichloromethane. 200 ml of water was added to extract the oil layer, and the layers were separated. The dichloromethane layer was dried and concentrated, and then purified by column chromatography. The eluent was methanol / dichloromethane = 20 / 1~8 / 1 to obtain 9.3 g of solid (Compound 4). 1H NMR (400 MHz, DMSO) δ 8.38 (s, 1H), 8.23 ​​(s, 1H), 7.84 (s, 1H),6.01 (d, J = 5.9 Hz, 1H), 5.43 (dd, J = 6.7, 4.8 Hz, 1H), 5.27 (d, J = 4.9 Hz, 1H), 4.40 – 4.29 (m, 2H), 3.98 (q, J = 3.2 Hz, 1H), 3.67 (dt, J = 12.0,4.1 Hz, 1H), 3.61 – 3.52 (m, 1H), 3.30 (s, 3H), 2.95 (s, 3H). The purity of compound 4 determined by HPLC was 95.6%, and the yield was 98.2%. Example 4

[0058] This example provides a method for preparing compound 5, namely N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine. The synthetic route is as follows:

[0059] ;

[0060] The preparation method of compound 5 comprises the following steps:

[0061] A round-bottom flask was charged with 21.3 g of compound 4 and 400 mL of pyridine. In another round-bottom flask, 36.66 g of DMTrCl (4,4'-dimethoxytrityl chloride) was added and dissolved in 200 mL of DCM. The DMTrCl solution in DCM was added dropwise to the reaction flask containing compound 4 (30-60 min) with stirring. The mixture was stirred at room temperature overnight and monitored by HPLC. 20 mL of methanol was added and stirred for 0.5 h to quench the reaction. The reaction solution was concentrated under reduced pressure, 500 mL of DCM and 500 mL of water were added, and the mixture was extracted with 200 mL of DCM. The combined organic phases were concentrated under reduced pressure and purified by column chromatography (PE:EA = 1:0 to PE:EA = 1:1 to DCM:MeOH = 20:1) to obtain 41.0 g of a solid (compound 5). The purity of compound 5 was 97.1% by HPLC, and the yield was 95.1%.

[0062] The HPLC purity analysis of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine prepared in this example is as follows: Figure 1 shown.

[0063] The 1H NMR spectrum of N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine prepared in this example is as follows: Figure 2 The specific details are as follows: 1H NMR (400 MHz, DMSO-d6): 8.29(s, 1H),8.23(s, 1H), 7.84(s, 1H), 7.38-7.40(d, 2H), 7.21-7.30 (m, 8H), 6.83-6.88 (t,4H), 6.07-6.09 (d, 1H),5.31-5.33 (d, 1H), 4.47-4.51 (m, 2H), 4.07-4.11 (m,1H), 3.75 (s, 6H), 3.25-3.26 (m, 3H), 2.98 (s, 3H).

[0064] Based on the above-mentioned ideal embodiments of this application, and in accordance with the above description, relevant personnel can make various changes and modifications without departing from the scope of the technical concept of this application. The technical scope of this application is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine, characterized in that: The steps include: S1: Compound 1 is reacted with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in a pyridine alkaline environment to obtain compound 2; S2: Compound 2 is reacted with di-tert-butyl dicarbonate using 4-dimethylaminopyridine as a catalyst to obtain compound 3; S3: Compound 3 is reacted with iodomethane under the action of cesium carbonate to obtain intermediate 1, and then the BOC group of intermediate 1 is removed under the action of trifluoroacetic acid, and the TIPDSi protection is removed under the action of tetrabutylammonium fluoride to generate compound 4. The structure of intermediate 1 is ; S4: Compound 4 is reacted with 4,4'-dimethoxytrityl chloride in a pyridine alkaline environment to obtain compound 5, namely N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine; The synthetic route of compound 5 is as follows: 。 2. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine according to claim 1, characterized in that: In step S1, compound 1 is first placed in a pyridine base environment, and then 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane is added to react.

3. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytrityl)-2'-O-methyladenosine according to claim 2, characterized in that: 1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane was added dropwise.

4. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: The reaction in step S1 is carried out under an inert gas environment.

5. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: The reaction solvent of step S2 is at least one of tetrahydrofuran, dichloromethane, 1,2-dichloroethane, chloroform, toluene, and ethyl acetate.

6. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: After step S2, a Boc group of the by-product 1 is removed by aminolysis to generate compound 3. The structure of the by-product 1 is .

7. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: In step S3, the reaction solvent for the reaction of compound 3 with iodomethane under the action of cesium carbonate is N,N-dimethylformamide and / or dimethyl sulfoxide, the reaction solvent for removing the BOC group under the action of trifluoroacetic acid is at least one of dichloromethane, 1,2-dichloroethane, chloroform, toluene, and ethyl acetate, and the reaction solvent for removing TIPDSi protection to generate compound 4 under the action of tetrabutylammonium fluoride is at least one of tetrahydrofuran, acetonitrile, methanol, and ethanol.

8. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: In step S4, compound 4 is first placed in a pyridine base environment, and then 4,4'-dimethoxytrityl chloride is added to react.

9. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 8, characterized in that: The 4,4'-dimethoxytrityl chloride solution was added dropwise.

10. The method for preparing N-methyl-5'-O-(4,4'-dimethoxytriphenyl)-2'-O-methyladenosine according to claim 1, characterized in that: Any reaction of steps S1 to S4 is carried out at room temperature.

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