Preparation method of 3 '-methoxy nucleoside analogue

Abstract

The invention provides a preparation method of a 3 '-methoxyl nucleoside analogue, which comprises the following steps: removing a 3'-protecting group of a compound V at high selectivity, adding methyl in situ so as to simply obtain a key methylation intermediate IV, and carrying out deprotection, acetylation, docking hydrolysis and other reactions on the intermediate IV, thereby obtaining the 3 '-methoxyl nucleoside analogue. The 3 '-methoxyl ribonucleoside analogue I is efficiently obtained. According to the present invention, the 3 '-site protection group is selectively removed so as to achieve the in-situ methylation, the reaction step is shortened, the reaction purity is substantially improved, the generation of the isomer is avoided, the purification pressure is reduced, the raw material cost is low, the reaction step is short, the use of the sodium hydrogen and other dangerous reagents is avoided, the operability is strong, and the yield is far higher than the yield in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of drug intermediate synthesis, and specifically relates to a preparation method of a 3'-methoxy nucleoside analog. Background Art

[0002] In the face of the novel coronavirus epidemic, the speed of vaccine development determines the speed of lifesaving. Therefore, mRNA vaccines with a rapid production process will play an important role in the development of coronavirus vaccines. mRNA vaccines have significant advantages such as high efficiency, low side effects and low acquisition cost, making them widely used in preclinical and clinical trials of various infectious diseases and cancers. 3′-methoxyguanosine is widely used in the synthesis of chain-terminating dinucleotide mRNA cap analogs, and it has also been reported to be used as an anti-reverse cap analog (ARCA), which effectively promotes the translation of transcripts into proteins.

[0003] The present invention relates to the synthesis of 3'-methoxy nucleoside analogs. According to existing literature and patent reports, such as the synthesis method provided by Haixin Ding, Zhizhong Ruan, Peihao Kou et al. in "Total Synthesis of Mycalisine B", tetraacetyl ribose is used as a raw material, and intermediates 3 and 4 are obtained through three-step reaction and column chromatography. Intermediate 3 is recovered and hydrolyzed for recycling. Intermediate 4 is subjected to methylation, deprotection, acetylation and docking hydrolysis reactions, and a series of column chromatography processes are performed to finally obtain the target product compound 8.

[0004]

[0005] On the one hand, this method uses precious metal silver oxide for methylation, which is relatively expensive. In the literature, it is only a small-scale test reaction. Silver oxide is easy to precipitate, which is not conducive to industrial scale-up production. On the other hand, it is necessary to increase the yield by recovering intermediate 3. Moreover, the above steps require multiple column chromatography processes for purification, which increases the production cost. Summary of the invention

[0006] The present invention provides a novel method for preparing 3'-methoxyribonucleoside. The method removes the 3'-protecting group of compound V with high selectivity, and then adds methyl in situ to obtain the key methylated intermediate IV in a relatively simple manner. After that, the intermediate IV is subjected to deprotection, acetylation, docking and hydrolysis reactions to obtain 3'-methoxyribonucleoside analog I with high efficiency.

[0007] The present invention provides a method for preparing a 3'-methoxyribonucleoside analogue having a structure as shown in formula (I);

[0008]

[0009] B in the formula I is adenine, guanine, uracil, cytosine, thymine or 2-aminoadenine.

[0010] According to the present invention, the specific preparation method comprises the following steps:

[0011]

[0012] 1. Compound V reacts with a methylating agent under the action of an inorganic base to generate compound IV;

[0013] 2. Compound IV is deprotected and acetylated to generate compound III in one pot

[0014] 3. Compound III is docked with the nucleoside base to generate compound II

[0015] 4. Compound II undergoes hydrolysis to generate compound I

[0016] As a specific embodiment, the reaction solvent in step 1 is selected from one or more of DMF, DMSO, NMP, THF, and DCM, preferably DMF;

[0017] As a specific embodiment, the methylating agent in step 1 is selected from one or more of dimethyl sulfate, methyl iodide, trimethyl phosphate, and dimethyl carbonate, preferably dimethyl sulfate;

[0018] As a specific embodiment, the inorganic base in step 1 is selected from one or more of sodium hydroxide, potassium hydroxide, and sodium hydroxide, preferably sodium hydroxide;

[0019] As a specific embodiment, the reaction temperature in step 1) is -78 to 50°C, preferably -30 to 25°C;

[0020] As a specific embodiment, in step 1), the molar ratio of compound V: inorganic base: methylating agent is 1:1:1 to 1:5:10, preferably 1:2:2 to 1:5:10;

[0021] As a specific embodiment, the post-treatment method of step 1) is: after the reaction is completed, ethyl acetate and purified water are added for washing, and the organic phase is collected. The organic phase is concentrated to dryness under reduced pressure to obtain a crude product of a light yellow oily intermediate D00, and D00 is refined by a mixed solvent of ethyl acetate and n-hexane to obtain a pure product.

[0022] As a specific embodiment, the reaction solvent of step 2) is acetic acid, the deprotection reagent is selected from one of sulfuric acid, hydrochloric acid, and phosphoric acid, preferably sulfuric acid; the acetylation reagent is selected from one of acetic anhydride and acetyl chloride, preferably acetic anhydride;

[0023] As a specific embodiment, the reaction temperature of step 2) is -20°C to 40°C, preferably 0-25°C;

[0024] As a specific embodiment, the post-treatment method of step 2) is: after the reaction is completed, the reaction solution is quenched with a saturated sodium chloride solution and extracted with ethyl acetate. The organic phase is washed with purified water, a saturated sodium bicarbonate solution, and a saturated sodium chloride solution in sequence. The organic phase is dried over anhydrous sodium sulfate, filtered, and the filter cake is rinsed with ethyl acetate. The filtrate is concentrated to dryness under reduced pressure to obtain an oily intermediate III, which is directly used in the next step.

[0025] As a specific embodiment, the base B in step 3) is selected from one of adenine, guanine, uracil, cytosine, thymine, and 2-aminoadenine;

[0026] As a specific embodiment, the order of adding materials in step 3) is: the base is first reacted with BSA, and then compound III and Lewis acid are added;

[0027] As a specific embodiment, the reaction solvent in step 3) is selected from one or more of DCM, ACN, EA, THF, toluene, and DMF, preferably one of DCM, ACN, THF, and toluene;

[0028] As a specific embodiment, the Lewis acid in step 3) is selected from one of TMSOTf, SnCl4, and LiOTf, preferably TMSOTf;

[0029] As a specific embodiment, the reaction temperature of the base and BSA in step 3) is 25°C-160°C, preferably 50-130°C; the reaction temperature after adding Lewis acid is -20 to 160°C, preferably 0-130°C;

[0030] As a specific embodiment, the molar ratio of compound III, base, BSA and Lewis acid in step 3) is 1:1:3:0.2 to 1:5:12:8, preferably 1:1:3:4.5 to 1:3:8:8;

[0031] As a specific embodiment, the post-treatment method of step 3) is: cooling after the reaction is completed, slowly adding saturated sodium bicarbonate solution to quench the reaction. Then filtering, adding the filter cake to dichloromethane and stirring, filtering, washing the filtrate with purified water, saturated sodium bicarbonate solution and saturated sodium chloride solution in sequence, and collecting the organic phase. Concentrating to dryness under reduced pressure to obtain intermediate II, which is directly put into the next step.

[0032] As a specific embodiment, the hydrolysis reaction in step 4) is carried out in an alkaline reagent, and the alkaline reagent is selected from one of ammonia methanol solution, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, and concentrated ammonia water, preferably one of ammonia methanol solution;

[0033] As a specific embodiment, the reaction solvent for the hydrolysis reaction in step 4) is selected from one or more of THF, methanol, ethanol, and isopropanol, preferably methanol;

[0034] As a specific embodiment, the post-treatment method of step 4) is: after the reaction is completed, it is concentrated to dryness under reduced pressure, and then refined once with 15 times the volume of alcohol and purified water respectively, and the solid is dried in vacuum to obtain compound I; the alcohol solvent is selected from one or more of methanol, ethanol and isopropanol.

[0035] The beneficial effects of the present invention are that by selectively removing the 3'-protecting group and then adding a methyl group in situ, the reaction steps are shortened, the reaction purity is greatly improved, the generation of isomers is avoided, and the purification pressure is reduced. In general, compared with the prior art, the method has low raw material cost, short reaction steps, avoids the use of dangerous reagents such as sodium hydrogen, has strong operability, and the yield is much higher than the yield in the prior art. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments. The following embodiments are used to understand the methods and core ideas of the present invention. For those skilled in the art, any possible changes or substitutions without departing from the concept of the present invention are within the scope of protection of the present invention. The experimental methods in the embodiments of the present invention that do not specify specific conditions are usually conventional conditions, or according to the conditions recommended by the raw material or commodity manufacturer; reagents that do not specify the source are usually conventional reagents that can be purchased through commercial channels.

[0037] Example 1 Preparation of Compound V

[0038]

[0039] Add acetone (3.95kg) and tetraacetyl ribose (1kg) to the reaction tank, stir until dissolved, control the temperature of the reaction at 25°C, slowly drop iodine (0.04kg) in acetone (0.79kg) solution, and complete the dropwise addition over (30-60) minutes. React at room temperature overnight, and control the reaction endpoint by TLC. After the reaction is completed, control the reaction temperature at 25°C, and drop 30% sodium sulfite aqueous solution into the reaction solution to quench (the endpoint is based on pH = 7-8). Extract three times with ethyl acetate (4.5kg×3), and combine the organic phases. Wash the organic phase with 10% sodium chloride aqueous solution (3.3kg). Dry the organic phase with anhydrous sodium sulfate, filter, and rinse the filter cake with ethyl acetate. The filtrate is concentrated to dryness under reduced pressure at (50±5)°C to obtain a yellow oily intermediate 1-1 with a molar yield of 91%.

[0040] Methanol (3.6 kg) and intermediate 1-1 (0.9 kg) were added to the reaction tank, and anhydrous potassium carbonate solid (0.9 kg) was added after stirring to dissolve. The internal temperature was controlled at 25 ° C. The reaction was carried out for (0.5-1) h, and the reaction end point was controlled by TLC. After the reaction was completed, the mixture was filtered and rinsed with methanol. The filtrate was transferred to a reaction tank and the pH was adjusted to 8-9 with a saturated aqueous solution of ammonium chloride. Filter (with diatomaceous earth pad) and the filter cake was rinsed with methanol. The filtrate was concentrated to dryness under reduced pressure at (50 ± 5) ° C. After concentration to dryness, dichloromethane (5.99 kg) and anhydrous sodium sulfate (0.3 kg) were added and slurried overnight. Filter, slurry the filter cake with dichloromethane (5.99 kg), filter, combine the filtrates, and the filtrate was concentrated to dryness under reduced pressure at (40 ± 5) ° C to obtain a crude intermediate 1-2, which was purified by column chromatography with a molar yield of 83%.

[0041] Add dichloromethane (4.25L) and intermediate 1-2 (0.425kg) to the reaction tank, stir to dissolve, and add triethylamine (1.36L). The temperature of the reaction solution drops to (-5±5)℃, and slowly add a solution of benzoyl chloride (0.693kg) in dichloromethane (0.757kg), control the internal temperature below 10℃, and add for (1~2)h. After the addition is complete, heat to (20±5)℃, react for (0.5~1.5)h, and control the reaction endpoint by TLC. After the reaction is completed, add methanol to quench and stir for 10min. Wash with purified water (2.125kg), dry the organic phase with anhydrous sodium sulfate, filter, and rinse the filter cake with dichloromethane. The filtrate is concentrated to dryness under reduced pressure at (40±5)℃ to obtain a crude intermediate 1-3.

[0042] Add methanol (1.5 kg) and the crude intermediate C00 to the reaction tank, control the internal temperature to (55±5)°C, and stir to dissolve. Cool the reaction tank to (-5±3)°C, keep warm and stir to crystallize for 1 hour. Filter by suction, and rinse the filter cake with cold methanol. Dry the wet product under vacuum at (40±5)°C for (12-20)h to obtain intermediate 1-3 with a molar yield of 90%.

[0043] Example 2 Preparation of Compound IV

[0044] Add DMF (6.56L) and intermediate V (0.656kg) to the reaction tank and stir to dissolve. Add dimethyl sulfate (0.83kg), control the internal temperature at 20℃, add potassium hydroxide solid (0.37kg), continue to keep warm for 1.5h, and control the reaction end point by liquid phase detection (the reaction can be stopped when the remaining raw material is less than 2%). If the reaction is not complete, add (0.5-1)eq potassium hydroxide until the reaction is complete. After the reaction is completed, add ethyl acetate (17.7kg), stir for 10min, wash with purified water (19.68kg), and collect the organic phase. The organic phase is dried with anhydrous sodium sulfate, filtered, and the filter cake is rinsed with ethyl acetate. The filtrate is concentrated to dryness under reduced pressure at (40±5)℃ to obtain a light yellow oily intermediate IV. The oil is added with n-hexane / ethyl acetate = 10 / 1 and stirred for crystallization, and the pure product is obtained by suction filtration, with a molar yield of 80% and a purity of 99.2%.

[0045] Example 3 Preparation of Compound IV

[0046] Add DMF (6.56L) and intermediate V (0.656kg) to the reaction tank and stir to dissolve. Add iodomethane (0.93kg), control the internal temperature at 20℃, add potassium hydroxide solid (0.37kg), continue to keep warm for 1.5h, and control the reaction end point by liquid phase detection (the reaction can be stopped when the remaining raw material is less than 2%). If the reaction is not complete, add (0.5-1)eq potassium hydroxide until the reaction is complete. After the reaction is completed, add ethyl acetate (17.7kg), stir for 10min, wash with purified water (19.68kg), and collect the organic phase. The organic phase is dried over anhydrous sodium sulfate, filtered, and the filter cake is rinsed with ethyl acetate. The filtrate is concentrated to dryness under reduced pressure at (40±5)℃ to obtain a light yellow oily intermediate IV. The oil is added with n-hexane / ethyl acetate = 10 / 1 and stirred for crystallization, and the pure product is obtained by suction filtration, with a molar yield of 84% and a purity of 99.1%.

[0047] Example 4 Preparation of Compound III

[0048] Add acetic acid (3.55kg) and intermediate IV (0.34kg) to the reaction tank and stir to dissolve. Control the internal temperature at 15°C, slowly add a solution of sulfuric acid (0.05kg) in acetic acid (0.17kg), and stir for 1.5h. Control the internal temperature at 15°C, slowly add acetic anhydride (0.676kg), and the addition time is (30-40)min. After the addition is complete, heat to 25°C, stir the reaction for 2h, and control the reaction end point by liquid phase detection. After the reaction is completed, control the internal temperature at 15°C, quench the reaction solution with ice water (12.17kg), and extract with ethyl acetate (3.04kg). The organic phase is washed with purified water (3.38kg), saturated sodium bicarbonate solution (4.06kg), and saturated sodium chloride solution (1.86kg) in sequence. The organic phase is dried over anhydrous sodium sulfate, filtered, and the filter cake is rinsed with ethyl acetate. The filtrate was concentrated to dryness under reduced pressure at (45±5)°C to obtain an oily intermediate III with a molar yield of 95%.

[0049] Example 5 Preparation of Compound II (one reaction for each base, five in total)

[0050] Base B is adenine: Add acetonitrile (7.9kg), adenine (0.77kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drip TMSOTf (3.15kg) in acetonitrile. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly dripped to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 85%.

[0051] Base B is guanine: Add acetonitrile (7.9kg), guanine (0.86kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drip TMSOTf (3.15kg) in acetonitrile. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly dripped to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 80%.

[0052] Base B is uracil: Add acetonitrile (7.9kg), uracil (0.64kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drop TMSOTf (3.15kg) in acetonitrile. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly added to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 54%.

[0053] Base B is cytosine: Add acetonitrile (7.9kg), cytosine (0.63kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drip TMSOTf (3.15kg) in acetonitrile. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly dripped to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 75%.

[0054] Base B is thymine: Add acetonitrile (7.9kg), thymine (0.72kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drop TMSOTf (3.15kg) in acetonitrile solution. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly added to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 61%.

[0055] Base B is 2-aminoadenine: Add acetonitrile (7.9kg), 2-aminoadenine (0.85kg) and BSA (3.46kg) to the reaction tank, heat to reflux, and continue stirring for 30min after the reaction solution is dissolved. Control the internal temperature of the reaction solution to 10°C, add intermediate III (1kg), and slowly drip TMSOTf (3.15kg) in acetonitrile. After the addition is complete, keep warm and stir for 15min. The reaction solution is heated to reflux and the reaction continues for 16-18 hours. The reaction end point is controlled by TLC. After the reaction is completed, the temperature is reduced to 0°C, and a saturated sodium bicarbonate solution is slowly dripped to quench the reaction, and the internal temperature is controlled not to exceed 10°C. Filter, add the filter cake to dichloromethane (79.8kg), stir for 20min, and filter (pad with diatomaceous earth). The filtrate is washed twice with purified water, twice with 5% sodium bicarbonate solution, and washed with saturated sodium chloride solution (35kg), and the organic phase is collected. The organic phase was dried over anhydrous sodium sulfate, filtered, and the filter cake was rinsed with dichloromethane. The filtrate was concentrated to dryness under reduced pressure at (40±5)°C to obtain Intermediate II with a molar yield of 86%.

[0056] Example 4 Preparation of Compound I

[0057]

[0058] Base B is adenine: methanol (1.2 kg) and intermediate II (0.3 kg) are added to the reaction tank, and concentrated ammonia (1.4 kg) is added. The internal temperature is controlled at 42°C for 12-16 hours, and the reaction end point is controlled by TLC. After the reaction is completed, the reaction solution is concentrated to dryness under reduced pressure at 50°C, and then purified once with 15 times the volume of ethanol and purified water respectively. The solid is vacuum dried at 40°C to constant weight to obtain compound I a , molar yield 73%, purity: 99.1%.

[0059] Base B is guanine: methanol (1.3 kg) and intermediate II (0.33 kg) are added to the reaction tank, and concentrated ammonia (1.5 kg) is added. The internal temperature is controlled at 40°C for 12-16 hours, and the reaction end point is controlled by TLC. After the reaction is completed, the reaction solution is concentrated to dryness under reduced pressure at 50°C, and then purified once with 15 times the volume of ethanol and purified water respectively. The solid is vacuum dried at 40°C to constant weight to obtain compound I b , molar yield 85%, purity 99.5%.

[0060] Base B is uracil: methanol (0.71 kg) and intermediate II (0.18 kg) are added to the reaction tank, and concentrated ammonia (0.8 kg) is added. The internal temperature is controlled at 40°C for 12-16 hours, and the reaction end point is controlled by TLC. After the reaction is completed, the reaction solution is concentrated to dryness under reduced pressure at (55±5)°C (with tetrahydrofuran), and then purified once with 15 times the volume of ethanol and purified water, and the solid is vacuum dried at 40°C for 24-48 hours to obtain compound I c , molar yield 70%, purity: 98.9%.

[0061] Base B is cytosine: methanol (1 kg) and intermediate II (0.25 kg) are added to the reaction tank, and concentrated ammonia (1.1 kg) is added. The internal temperature is controlled at 40°C for 12-16 hours, and the reaction end point is controlled by TLC. After the reaction is completed, the reaction solution is concentrated to dryness under reduced pressure at 50°C, and then purified once with 15 times the volume of ethanol and purified water respectively. The solid is vacuum dried at 40°C to obtain compound I d , molar yield 80%, purity: 99.3%.

[0062] Base B is thymine: methanol (0.83kg) and intermediate II (0.21) are added to the reaction tank, and concentrated ammonia (1kg) is added. The internal temperature is controlled at 40°C for 12-16 hours, and the reaction end point is controlled by TLC. After the reaction is completed, the reaction solution is concentrated to dryness under reduced pressure at 50°C, and then purified once with 15 times the volume of ethanol and purified water respectively. The solid is vacuum dried at 40°C for 24-48 hours to obtain compound I e , molar yield 79%, purity: 99.0%.

[0063] Base B is 2-aminoadenine: Methanol (1.26 kg) and intermediate II (0.32 kg) were added to the reaction tank, and concentrated ammonia (1.5 kg) was added. The internal temperature was controlled at 40°C for 12-16 hours, and the reaction end point was controlled by TLC. After the reaction was completed, the reaction solution was concentrated to dryness under reduced pressure at 50°C, and then purified once with 15 times the volume of ethanol and purified water, and the solid was dried in vacuum at 40°C to obtain compound I. f , molar yield 73%, purity: 98.7%.

Claims

1. A method for preparing a 3'-methoxyribonucleoside analogue of formula I, characterized in that: The method comprises reacting the compound represented by formula V with a methylating agent under the action of an inorganic base to obtain a compound represented by formula IV, 2. A method for preparing a 3'-methoxyribonucleoside analogue of formula I, characterized in that: The method comprises reacting a compound represented by formula V with a methylating agent under the action of an inorganic base to obtain a compound represented by formula IV, wherein B in the compound represented by formula I is adenine, guanine, uracil, cytosine, thymine, or 2-aminoadenine, 3. The method according to claim 1 or 2, characterized in that: The methylating agent is selected from one or more of dimethyl sulfate, methyl iodide, trimethyl phosphate and dimethyl carbonate.

4. The method according to claim 1 or 2, characterized in that: The inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide and sodium hydroxide.

5. The method according to claim 1 or 2, characterized in that: The reaction solvent is selected from one or any two or more of DMF, DMSO, NMP, THF and DCM.

6. The method according to claim 1 or 2, characterized in that: The molar ratio of the compound represented by formula V to the inorganic base and the methylating agent is 1:1:1 to 1:5:10, preferably 1:2:2 to 1:5:

10.

7. The method according to claim 1 or 2, characterized in that: The reaction temperature is -78 to 50°C, preferably -30 to 25°C.

8. The method according to claim 1 or 2, characterized in that: The invention also includes reacting compound IV with a deprotection agent and an acetylation agent to generate compound III, 9. The method according to claim 8, characterized in that: The deprotection agent is selected from one or more of sulfuric acid, hydrochloric acid and phosphoric acid, preferably sulfuric acid.

10. The method according to claim 8, characterized in that: The acetylating agent is selected from acetic anhydride and acetyl chloride, preferably acetic anhydride; 11. The method according to claim 8, characterized in that: The reaction solvent is acetic acid.

12. The method according to claim 8, characterized in that: The reaction temperature is -20°C to 40°C, preferably 0-25°C; 13. The method according to claim 1 or 2, characterized in that: The method further comprises docking compound III with base B of the nucleoside to generate compound II, 14. The method according to claim 13, characterized in that: The base B is first reacted with BSA, and then compound III and Lewis acid are added.

15. The method according to claim 13, characterized in that: The base B is selected from one of adenine, guanine, uracil, cytosine, thymine and 2-aminoadenine.

16. The method of claim 13, wherein: The Lewis acid is selected from one of TMSOTf, SnCl4, and LiOTf, preferably TMSOTf.

17. The method of claim 13, wherein: The reaction solvent is selected from one or more of DCM, ACN, EA, THF, toluene and DMF, preferably one of DCM, ACN, THF and toluene.

18. The method of claim 13, wherein: The reaction temperature of the base B and BSA is 25°C-160°C, preferably 50-130°C; the reaction temperature after adding Lewis acid is -20 to 160°C, preferably 0-130°C.

19. The method of claim 13, wherein: The molar ratio of the compound III, base, BSA and Lewis acid is 1:1:3:0.2 to 1:5:12:8, preferably 1:1:3:4.5 to 1:3:8:

8.

20. The method according to claim 1 or 2, characterized in that: The method also includes 21. The method of claim 20, wherein: The reaction is carried out in an alkaline reagent, which is selected from one of ammonia methanol solution, potassium carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, and concentrated ammonia water, preferably one of ammonia methanol solution.

22. The method of claim 20, wherein: The reaction solvent of the reaction is selected from one or more of THF, methanol, ethanol and isopropanol, preferably methanol.

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