Method for synthesizing n2-c6 amino-modified deoxyguanosine monomer

Abstract

The present invention belongs to the technical field of DNA synthesis. Provided is a method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer. The synthesis method comprises: performing a silylation protection reaction on deoxyguanosine under the protection of a silanization reagent so as to obtain a first intermediate; performing a Mitsunobu reaction on a second reaction raw material to obtain a second intermediate; performing a nucleophilic substitution reaction on the first intermediate and the second intermediate to obtain a third intermediate; and performing a desilylation protection reaction and a protective group introduction reaction, followed by an activation coupling reaction to obtain a final product. In the synthesis method, the final product is prepared by performing the silylation protection reaction, the Mitsunobu reaction, the nucleophilic substitution reaction, the protective group introduction reaction and the activation coupling reaction on the raw materials. The synthesis method has the advantages of the chemical raw materials used being simple and readily available, and being low cost; having mild reaction conditions, and easy to scale-up production; high stability of the intermediate obtained; and being a simple purification method and easily operated.

Description

A method for synthesizing N2-C6 amino-modified deoxyguanosine monomer Technical Field

[0001] The present invention belongs to the technical field of DNA synthesis, and in particular relates to a method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer. Background Art

[0002] Solid-phase phosphoramidite synthesis is a method for synthesizing oligonucleotides, such as DNA and RNA. This technique involves the stepwise synthesis of the desired oligonucleotide chain on a solid support, linking the nucleotide units via phosphoramidite chemistry. This method is currently one of the most common and efficient oligonucleotide synthesis techniques, widely used in biotechnology and pharmaceutical research.

[0003] In solid-phase synthesis, a variety of amino-modified deoxyguanosine substances can be used. These modifications are typically used to introduce specific functional groups to facilitate subsequent labeling, ligation, or functionalization. Commonly used deoxyguanosine substances include a C6 amino-modified deoxyguanosine at the 8-position (Compound 1 in Figure 1) and a C6 amino-modified deoxyguanosine at the N2 position (Compound 2 in Figure 1).

[0004] While compound 1, a C6 amino modification at the 8-position of deoxyguanosine, possesses amino functionality, it can reduce the thermal stability of the DNA duplex and, therefore, cannot completely replace deoxyguanosine in DNA synthesis. Compound 2, a C6 amino modification at the N2-position of deoxyguanosine, exhibits no significant differences in complementary pairing or thermal stability compared to deoxyguanosine and can serve as a deoxyguanosine replacement, introducing an amino group and functionalizing DNA. However, no published patents or literature reports a synthesis method for compound 2.

[0005] Summary of the Invention

[0006] To solve the above problems, the present invention provides a method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer, comprising:

[0007] S1, subjecting the first reaction raw material, deoxyguanosine, to a silane protection reaction under the protection of a silanization reagent, 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalysis of a catalyst, imidazole, to obtain a first intermediate;

[0008] S2, taking the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and performing a Mitsunobu reaction in the presence of a dehydrating agent, an azocyclic base, and an oxidizing agent to obtain a second intermediate;

[0009] S3, subjecting the first intermediate and the second intermediate to a nucleophilic substitution reaction promoted by a nucleophile, potassium carbonate, to obtain a third intermediate;

[0010] S4, taking the third intermediate and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate;

[0011] S5, using 4,4'-bismethoxytrityl chloride as a protecting group reagent, the fourth intermediate is subjected to a protecting group introduction reaction under the conditions of a basic promoter triethylamine and a nucleic acid catalyst 4-dimethylaminopyridine to obtain a fifth intermediate;

[0012] S6, subjecting the fifth intermediate to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine in the presence of diisopropylammonium tetrazolium as a catalyst to obtain the N2-C6 amino-modified deoxyguanosine monomer.

[0013] Preferably, the S1 is to subject the first reaction raw material, deoxyguanosine, to a silane protection reaction under the protection of a silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalysis of a catalyst imidazole to obtain a first intermediate, comprising:

[0014] S11, adding the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalyst imidazole to a first organic solvent at room temperature;

[0015] S12, stirring and mixing to perform a silane protection reaction, and terminating the reaction with ice water after the reaction is complete, thereby obtaining the first intermediate;

[0016] Preferably, the first organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0017] Preferably, the organic solvent is N,N-dimethylformamide;

[0018] Preferably, the reaction temperature of the silane protection reaction is 10°C-50°C;

[0019] Preferably, the reaction temperature of the silane protection reaction is 25°C.

[0020] Preferably, in step S1, the molar ratio of the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalyst imidazole is 1:1:(1-4);

[0021] Preferably, the molar ratio is 1:1:3.

[0022] Preferably, the S2 is to take the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and carry out Mitsunobu reaction under the action of a dehydrating agent, an azoheterocyclic base and an oxidizing agent to obtain a second intermediate, comprising:

[0023] S21, adding the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, a dehydrating agent, an azocyclic base, and an oxidizing agent to a second organic solvent at room temperature;

[0024] S22, performing a Mitsunobu reaction under a protective atmosphere, and after the reaction is complete, adding sodium thiosulfate to quench the reaction to obtain a reaction mixture;

[0025] S23, concentrating the reaction mixture and purifying it by chromatography to obtain the second intermediate;

[0026] Preferably, the dehydrating agent is triphenylphosphine;

[0027] Preferably, the nitrogen heterocyclic base is imidazole;

[0028] Preferably, the oxidizing agent is iodine;

[0029] Preferably, the second organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0030] Preferably, the second organic solvent is dichloromethane;

[0031] Preferably, the reaction temperature of the Mitsunobu reaction is 10°C-50°C;

[0032] Preferably, the reaction temperature of the Mitsunobu reaction is 25°C.

[0033] Preferably, in step S2, the molar ratio of the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, the dehydrating agent, the nitrogen heterocyclic base and the oxidizing agent is 1:(1-4):(1-4):(1-4);

[0034] Preferably, the molar ratio is 1:1.5:1.5:1.5.

[0035] Preferably, the step S3, wherein the first intermediate and the second intermediate are subjected to a nucleophilic substitution reaction promoted by a nucleophilic agent, potassium carbonate, to obtain a third intermediate, comprises:

[0036] S31, dissolving the first intermediate and the second intermediate in a third organic solvent;

[0037] S32, stirring and heating under a protective atmosphere;

[0038] S33, adding the nucleophilic agent potassium carbonate to carry out a nucleophilic substitution reaction to obtain the third intermediate;

[0039] Preferably, the amount of the nucleophile potassium carbonate added is 1-3 times the equivalent of the first intermediate;

[0040] Preferably, the third organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0041] Preferably, the third organic solvent is N,N-dimethylformamide;

[0042] Preferably, the reaction temperature of the nucleophilic substitution reaction is 50°C-100°C;

[0043] Preferably, the reaction temperature of the nucleophilic substitution reaction is 60°C.

[0044] Preferably, in step S3, the molar ratio of the first intermediate to the second intermediate is 1:(1-4);

[0045] The molar ratio of the first intermediate to potassium carbonate is 1:(1-3);

[0046] Preferably, the molar ratio of the first intermediate to the second intermediate is 1:1.5;

[0047] Preferably, the molar ratio of the first intermediate to potassium carbonate is 1:2.

[0048] Preferably, the step S4 comprises taking the third intermediate and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate, comprising:

[0049] S41, dissolving the third intermediate and tetrabutylammonium fluoride in a fourth organic solvent;

[0050] S42, stirring and mixing under a protective atmosphere to perform a desilication protection reaction, and after the reaction is complete, separating and purifying to obtain the fourth intermediate;

[0051] Preferably, the fourth organic solvent is selected from any one of chloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0052] Preferably, the fourth organic solvent is tetrahydrofuran;

[0053] Preferably, the reaction temperature of the desilication protection reaction is 10°C-50°C;

[0054] Preferably, the reaction temperature of the desilication protection reaction is 26°C.

[0055] Preferably, in step S4, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:(1-4);

[0056] Preferably, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:1.5.

[0057] Preferably, the step S5 is to introduce a protecting group into the fourth intermediate using 4,4'-bismethoxytrityl chloride as a protecting group reagent in the presence of a basic promoter, triethylamine, and a nucleic acid catalyst, 4-dimethylaminopyridine, to obtain a fifth intermediate, comprising:

[0058] S51, dissolving the fourth intermediate and 4,4'-bismethoxytrityl chloride in a fifth organic solvent;

[0059] S52, heating and stirring the mixture under a protective atmosphere;

[0060] S53, adding the alkaline promoter triethylamine and the nucleic acid catalyst 4-dimethylaminopyridine to carry out a protecting group introduction reaction, and separating and purifying after the reaction is complete to obtain the fifth intermediate;

[0061] Preferably, the amount of the basic promoter triethylamine added is 1-3 times the equivalent of the fourth intermediate;

[0062] Preferably, the fifth organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and pyridine;

[0063] Preferably, the fifth organic solvent is pyridine;

[0064] Preferably, the reaction temperature of the protecting group introduction reaction is 20°C-80°C;

[0065] Preferably, the reaction temperature of the protecting group introduction reaction is 40°C.

[0066] Preferably, in step S5, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:(1-3);

[0067] The molar ratio of the fourth intermediate to triethylamine is 1:(1-3);

[0068] Preferably, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:2;

[0069] Preferably, the molar ratio of the fourth intermediate to triethylamine is 1:2.

[0070] Preferably, the step S6, wherein the fifth intermediate is subjected to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine under the catalysis of diisopropylammonium tetrazolium to obtain the N2-C6 amino-modified deoxyguanosine monomer, comprises:

[0071] S61, dissolving the fifth intermediate and bis(diisopropylamino)(2-cyanoethoxy)phosphine in a sixth organic solvent;

[0072] S62, stirring and mixing under a protective atmosphere, adding the catalyst diisopropylammonium tetrazolium salt to perform an activation coupling reaction;

[0073] S63, after the reaction is complete, separation and purification are performed to obtain the N2-C6 amino-modified deoxyguanosine monomer;

[0074] Preferably, the amount of the catalyst diisopropylammonium tetrazolium added is 1-3 times the equivalent of the fifth intermediate;

[0075] Preferably, the sixth organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and pyridine;

[0076] Preferably, the sixth organic solvent is dichloromethane;

[0077] Preferably, the reaction temperature of the activated coupling reaction is 10°C-50°C;

[0078] Preferably, the reaction temperature of the activated coupling reaction is 25°C.

[0079] Preferably, in step S6, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:(1-3);

[0080] The molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:(1-3);

[0081] Preferably, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:2;

[0082] Preferably, the molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:2.

[0083] The present invention provides a method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer, comprising: subjecting deoxyguanosine, a first reaction raw material, to a silane protection reaction under the protection of a silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalysis of a catalyst imidazole to obtain a first intermediate; taking N-(6-hydroxyhexyl)trifluoroacetamide, a second reaction raw material, to a Mitsunobu reaction under the action of a dehydrating agent, an azocyclic base and an oxidizing agent to obtain a second intermediate; and subjecting the first intermediate and the second intermediate to a nucleophilic reaction under the promotion of a nucleophilic agent potassium carbonate. A substitution reaction is performed to obtain a third intermediate; the third intermediate is subjected to a desilication protection reaction using tetrabutylammonium fluoride to obtain a fourth intermediate; the fourth intermediate is subjected to a protecting group introduction reaction using 4,4'-bismethoxytrityl chloride as a protecting group reagent in the presence of an alkaline promoter, triethylamine, and a nucleic acid catalyst, 4-dimethylaminopyridine, to obtain a fifth intermediate; the fifth intermediate is subjected to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine in the presence of a catalyst, diisopropylammonium tetrazolium, to obtain the N2-C6 amino-modified deoxyguanosine monomer. The invention uses deoxyguanosine and N-(6-hydroxyhexyl)trifluoroacetamide as raw materials and respectively undergoes a silane protection reaction, a Mitsunobu reaction, a nucleophilic substitution reaction, a protecting group introduction reaction and an activation coupling reaction to prepare a final product, an N2-C6 amino-modified deoxyguanosine monomer. The chemical raw materials used in the synthesis method are simple and easily available, with low cost; the reaction conditions are mild, and the production can be easily scaled up; the obtained intermediate has high stability; and the purification method is simple and easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] FIG1 shows Compound 1 and Compound 2 (the final product N2-C6 amino-modified deoxyguanosine monomer in the present invention) mentioned in the background art;

[0085] FIG2 is a schematic flow diagram of the synthesis method of the N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0086] FIG3 is a schematic diagram of the synthesis route of step S1 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0087] FIG4 is a schematic diagram of the synthesis route of step S2 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0088] FIG5 is a schematic diagram of the synthesis route of step S3 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0089] FIG6 is a schematic diagram of the synthesis route of step S4 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0090] FIG7 is a schematic diagram of the synthesis route of step S5 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0091] FIG8 is a schematic diagram of the synthesis route of step S6 of the method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0092] FIG9 is a hydrogen nuclear magnetic resonance spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 1 of the synthesis method of the present invention;

[0093] FIG10 is a nuclear magnetic resonance phosphorus spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 1 of the synthesis method of the present invention;

[0094] FIG11 is a hydrogen nuclear magnetic resonance spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 2 of the synthesis method of the present invention;

[0095] FIG12 is a nuclear magnetic resonance phosphorus spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 2 of the synthesis method of the present invention;

[0096] FIG13 is a hydrogen nuclear magnetic resonance spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 3 of the synthesis method of the N2-C6 amino-modified deoxyguanosine monomer of the present invention;

[0097] FIG14 is a nuclear magnetic resonance phosphorus spectrum of the final product N2-C6 amino-modified deoxyguanosine monomer obtained in Example 3 of the synthesis method of the N2-C6 amino-modified deoxyguanosine monomer of the present invention.

[0098] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0099] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0100] Referring to FIG2 , the present invention provides a method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer, comprising:

[0101] S1, subjecting the first reaction raw material, deoxyguanosine, to a silane protection reaction under the protection of a silanization reagent, 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalysis of a catalyst, imidazole, to obtain a first intermediate;

[0102] S2, taking the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and performing a Mitsunobu reaction in the presence of a dehydrating agent, an azocyclic base, and an oxidizing agent to obtain a second intermediate;

[0103] S3, subjecting the first intermediate and the second intermediate to a nucleophilic substitution reaction promoted by a nucleophile, potassium carbonate, to obtain a third intermediate;

[0104] S4, taking the third intermediate and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate;

[0105] S5, using 4,4'-bismethoxytrityl chloride as a protecting group reagent, the fourth intermediate is subjected to a protecting group introduction reaction under the conditions of a basic promoter triethylamine and a nucleic acid catalyst 4-dimethylaminopyridine to obtain a fifth intermediate;

[0106] S6, subjecting the fifth intermediate to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine in the presence of diisopropylammonium tetrazolium as a catalyst to obtain the N2-C6 amino-modified deoxyguanosine monomer.

[0107] As mentioned above, silane protection is a protecting group strategy used in organic synthesis to protect reactive functional groups such as hydroxyl (-OH) groups to prevent unwanted side reactions during the reaction. Hydroxyl groups can be converted to their corresponding silyl ether protected forms using silylating agents such as trimethylchlorosilane (TMCS), triethoxysilane (TEOS), or trimethylsiloxane (TMOS). This protecting group is stable under reaction conditions and can be removed through a selective deprotection step when the original functional group needs to be restored.

[0108] The general process of silane protection reaction is as follows:

[0109] (1) Selection of silanization reagent: Select an appropriate silanization reagent based on the properties of the target molecule and the required stability of the protecting group.

[0110] (2) Reaction: The substrate containing the active functional group reacts with the silylating agent in an appropriate solvent and reaction conditions to form the corresponding silyl ether protective functional group. This step usually requires a catalyst, such as an acid or base, to promote the reaction.

[0111] (3) Deprotection: After the subsequent synthetic steps are completed, the original functional group can be restored by selective deprotection conditions (usually acidic or basic conditions, depending on the type of protecting group).

[0112] Advantages of silane protection reaction:

[0113] Selectivity: Silane protecting group strategies allow chemists to selectively protect and deprotect specific functional groups in the synthesis of complex organic molecules without affecting other functional parts in the molecule.

[0114] Stability: Silyl ether protecting groups exhibit good chemical stability under many reaction conditions, allowing multi-step synthetic routes without the need for intermediate steps to remove the protecting group.

[0115] Easy deprotection: Although protecting functional groups are stably present when needed, they can be selectively removed under mild conditions to restore the original functional groups, which provides flexibility for complex syntheses.

[0116] In the above-mentioned silane protection reaction, the silanization reagent used is 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (TIPDSiCl2), that is, using 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane as a protecting group can increase the stability of the deoxyguanosine intermediate and prevent the hydroxyl group of deoxyguanosine from being affected by unwanted reactions in subsequent chemical reactions.

[0117] As mentioned above, imidazole acts as a catalyst in this reaction, improving the efficiency of the reaction. Imidazole is a commonly used organic base that can promote the reaction of chlorosilane (such as TIPDSiCl2) with alcohol (hydroxyl group in deoxyguanosine) by accepting chloride ions (Cl - ) to accelerate the formation of silicon-oxygen bonds (Si-O).

[0118] The Mitsunobu reaction, as mentioned above, is an organic synthesis reaction used to convert alcohols into various functional groups. This reaction is achieved by using a dehydrating agent (such as triphenylphosphine), an azocyclic base (such as imidazole), and an oxidizing agent (such as iodine). In this reaction, the alcohol first reacts with the dehydrating agent and oxidizing agent to form a stable phosphate intermediate, which then reacts with a reactive electrophile such as trifluoroacetamide to ultimately replace the alcohol's hydroxyl group.

[0119] The Mitsunobu reaction allows for highly stereoselective functional group transformations, particularly for sensitive compounds. The mild reaction conditions make it suitable for the synthesis of many sensitive functional groups.

[0120] Through specific reaction conditions, a second intermediate in which the hydroxyl group of N-(6-hydroxyhexyl)trifluoroacetamide is replaced by other functional groups can be obtained. This process realizes the functional group conversion of the hydroxyl group through the Mitsunobu reaction.

[0121] In the above, the first intermediate and the second intermediate are subjected to a nucleophilic substitution reaction promoted by potassium carbonate (K2CO3) to obtain the third intermediate. This is a nucleophilic substitution reaction. In this type of reaction, potassium carbonate, as a promoter under alkaline conditions, can provide multiple functions:

[0122] (1) Neutralization of acidic by-products: Potassium carbonate can neutralize acidic by-products that may be produced during the reaction, maintain a neutral or slightly alkaline environment in the reaction mixture, and facilitate the nucleophilic substitution reaction.

[0123] (2) Improving the effectiveness of nucleophiles: In some cases, potassium carbonate can increase the effectiveness of nucleophiles, for example, by deprotonating alcohols or phenols to convert them into stronger nucleophiles (such as alcohol oxide anions or phenol oxide anions in the form of negative ions).

[0124] (3) Promote the leaving of leaving groups: Under alkaline conditions, the leaving ability of certain leaving groups (such as halogens) can be enhanced, thereby promoting the nucleophilic substitution reaction.

[0125] The desilylation reaction mentioned in step S4 involves treating the third intermediate with tetrabutylammonium fluoride (TBAF) to remove the silicon protecting group and restore the original functional group (hydroxyl group).

[0126] The above are the principles and purposes of the desiliconization protection reaction:

[0127] Principle: Desilication is a chemical reaction used to remove silicon protecting groups from molecules and restore protected functional groups, such as hydroxyl groups. In organic synthesis, silicon protecting groups (such as TBDMS and TIPS) are used to protect hydroxyl groups from nonspecific reactions during the reaction. Tetrabutylammonium fluoride (TBAF) is a powerful desilication agent that reacts with silane compounds to break carbon-silicon (C-Si) bonds, releasing the originally protected functional groups.

[0128] The reason for this reaction is:

[0129] Selectivity: In complex organic syntheses, a particular step may require modifying only certain functional groups in a molecule while leaving others unchanged. Silicon protecting groups can be used to protect sensitive functional groups early in the synthesis until further reaction is required.

[0130] Compatibility: Silicon protecting groups are stable under many reaction conditions, allowing for many types of chemical reactions without affecting the protected functional group.

[0131] Ease of Removal: Compared to some protecting groups, silicon protecting groups can be removed by relatively mild conditions (such as TBAF treatment), which reduces the need for harsh reaction conditions that may cause damage to the molecule.

[0132] In step S4, a desiliconization protection reaction is used, which has the following advantages:

[0133] Improved synthetic efficiency: Allows for the synthesis of complex molecules via multi-step pathways while reducing side reactions.

[0134] Improved product purity: Through protection / deprotection strategies, many potential side reactions can be avoided, thereby increasing the overall yield and purity of the target molecule.

[0135] Improved flexibility in synthetic strategies: This allows chemists to design synthetic routes more flexibly and optimize the overall synthetic process by introducing or removing protecting groups at appropriate steps.

[0136] In step S5, a protecting group introduction reaction is performed using 4,4'-bis(methoxytrityl) chloride (DMT-Cl) as a protecting group reagent in the presence of triethylamine (TEA) and 4-dimethylaminopyridine (DMAP). The goal of this reaction is to introduce a DMT protecting group onto the fourth intermediate.

[0137] Different reagents play different roles in the above-mentioned protective group introduction reaction:

[0138] Protecting group reagents: 4,4'-Bismethoxytrityl chloride (DMT-Cl) is a commonly used reagent to protect hydroxyl (-OH) groups, particularly in the synthesis of nucleosides and nucleotides. The DMT protecting group reacts with the hydroxyl group in the molecule to form a stable ether bond, thereby protecting the hydroxyl group from subsequent reactions.

[0139] Alkaline accelerator: Triethylamine acts as an alkaline accelerator to neutralize the hydrochloric acid (HCl) generated in the reaction, maintaining a neutral or slightly alkaline environment in the reaction mixture, and thus facilitating the reaction.

[0140] Nucleic acid catalyst: 4-Dimethylaminopyridine (DMAP) is a highly efficient nucleic acid catalyst that can increase the rate and efficiency of the reaction between hydroxyl groups and DMT-Cl.

[0141] In step S5, the protective group introduced is DMT (4,4'-dimethoxytrityl), and its advantages include:

[0142] Selective protection: The DMT protecting group allows for the selective protection of specific hydroxyl groups, facilitating chemical manipulation at specific positions in subsequent reactions.

[0143] Stability and reversibility: The DMT protecting group is stable under a variety of reaction conditions and can be selectively removed under specific conditions (such as acidic conditions), which makes the synthetic strategy flexible and varied.

[0144] High efficiency: Under the action of catalysts such as DMAP, the introduction of DMT protecting groups has high reaction efficiency and mild reaction conditions, making it suitable for the modification of sensitive and complex molecules.

[0145] Through this protecting group introduction strategy, synthesizers can introduce functional groups at specific positions of the molecule while avoiding unwanted side reactions, which is crucial for the precise synthesis of complex organic molecules.

[0146] In step S6, the activated coupling reaction involves reacting the fifth intermediate with bis(diisopropylamino)(2-cyanoethoxy)phosphine under the catalysis of diisopropylammonium tetrazolide (DIPEA·HNTf2) to produce an N2-C6 amino-modified deoxyguanosine monomer. This step is a nucleic acid coupling reaction used in the phosphorylation reaction to form a phosphate bond in nucleoside or oligonucleotide synthesis.

[0147] Activation: Bis(diisopropylamino)(2-cyanoethoxy)phosphine is used as a phosphorylating agent (or activating agent). This compound activates the hydroxyl group or other functional groups in the fifth intermediate in the reaction to form an activated intermediate that is more susceptible to nucleophilic attack.

[0148] Coupling: After the activation step, the activated intermediate undergoes a coupling reaction with another molecule containing the target amino group through nucleophilic attack to form a new chemical bond (such as a phosphate bond or a phosphoramide bond).

[0149] Catalyst: Diisopropylammonium tetrazolium is used as a catalyst to improve the efficiency and selectivity of the reaction. Tetrazolium salt is a commonly used phase transfer catalyst that helps improve the solubility of reactants and the reaction rate.

[0150] Advantages of the activated coupling reaction performed in step S6 include:

[0151] High efficiency: It can efficiently introduce modification groups at specific positions, suitable for the synthesis of fine chemicals and biological molecules.

[0152] High selectivity: By choosing appropriate activating agents and conditions, highly selective coupling reactions can be achieved with minimal side reactions.

[0153] Wide applicability: It is suitable for the activation and coupling of various functional groups, including hydroxyl groups, amine groups, etc., making it widely used in the synthesis of complex molecules.

[0154] Easy operation: The reaction conditions are relatively mild, no extreme conditions are required, and the reaction steps are simple.

[0155] The invention uses deoxyguanosine and N-(6-hydroxyhexyl)trifluoroacetamide as raw materials and respectively undergoes a silane protection reaction, a Mitsunobu reaction, a nucleophilic substitution reaction, a protecting group introduction reaction and an activation coupling reaction to prepare a final product, an N2-C6 amino-modified deoxyguanosine monomer. The chemical raw materials used in the synthesis method are simple and easily available, with low cost; the reaction conditions are mild, and the production can be easily scaled up; the obtained intermediate has high stability; and the purification method is simple and easy to operate.

[0156] Furthermore, the S1 is to subject the first reaction raw material, deoxyguanosine, to a silane protection reaction under the protection of a silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalysis of a catalyst imidazole to obtain a first intermediate, comprising:

[0157] S11, adding the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalyst imidazole to a first organic solvent at room temperature;

[0158] S12, stirring and mixing to perform a silane protection reaction, and terminating the reaction with ice water after the reaction is complete, thereby obtaining the first intermediate;

[0159] Furthermore, the first organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0160] Furthermore, the organic solvent is N,N-dimethylformamide;

[0161] Furthermore, the reaction temperature of the silane protection reaction is 10°C-50°C;

[0162] Furthermore, the reaction temperature of the silane protection reaction is 25°C.

[0163] Furthermore, in step S1, the molar ratio of the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalyst imidazole is 1:1:(1-4);

[0164] Furthermore, the molar ratio is 1:1:3.

[0165] As described above, referring to Figure 3, in step S1, deoxyguanosine is subjected to a silane protection reaction in the presence of 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (TIPDSiCl2) and imidazole. This step is intended to protect the hydroxyl groups of deoxyguanosine through a silylation reaction to prevent them from participating in unwanted reactions in subsequent synthetic steps.

[0166] The reactants are prepared by dissolving deoxyguanosine, TIPDSiCl2, and imidazole in a selected first organic solvent at a molar ratio of 1:1:(1-4). The preferred first organic solvent is N,N-dimethylformamide (DMF), as DMF is a polar solvent that can dissolve most organic compounds well and improve reaction efficiency.

[0167] Reaction conditions: The reaction mixture was stirred at room temperature (preferably 25°C). Imidazole served as a catalyst to accelerate the silylation reaction of TIPDSiCl2 with the hydroxyl group in deoxyguanosine.

[0168] Treatment after the reaction is completed: After a certain reaction time, ice water is added to the reaction mixture to terminate the reaction, and then a white solid is obtained by filtration, namely, silane-protected deoxyguanosine (first intermediate).

[0169] The silane protection reaction performed in step S1 has the advantage of efficiently protecting the hydroxyl groups in deoxyguanosine, preventing them from being nonspecifically modified in subsequent chemical reactions. It is carried out at room temperature, eliminating the need for high temperatures, thus reducing the risk of thermal degradation of heat-sensitive compounds. Common organic solvents and catalysts are used, making the operation simple and easy to control. Generally, this reaction can achieve a high yield.

[0170] It should be noted that different solvents have a significant effect on the reaction rate and product purity. Polar solvents such as DMF and DMSO help to increase the solubility of the reactants, thereby increasing the reaction efficiency. Tetrahydrofuran (THF) and dichloromethane (DCM) provide a relatively non-polar reaction environment, which is suitable for different reaction requirements. The molar ratio of imidazole affects the catalytic efficiency. A higher ratio of imidazole (such as 1:1:3) can provide a stronger catalytic effect and accelerate the silanization reaction, but the cost and possible side reactions must also be considered. Although the reaction can be carried out at room temperature, slight adjustment of the temperature (within the range of 10°C-50°C) can optimize the reaction rate and product yield. Lower temperatures may slow down the reaction rate, while higher temperatures may increase the risk of side reactions.

[0171] Furthermore, the S2 is to take the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and carry out Mitsunobu reaction under the action of a dehydrating agent, an azoheterocyclic base and an oxidizing agent to obtain a second intermediate, including:

[0172] S21, adding the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, a dehydrating agent, an azocyclic base, and an oxidizing agent to a second organic solvent at room temperature;

[0173] S22, performing a Mitsunobu reaction under a protective atmosphere, and after the reaction is complete, adding sodium thiosulfate to quench the reaction to obtain a reaction mixture;

[0174] S23, concentrating the reaction mixture and purifying it by chromatography to obtain the second intermediate;

[0175] Furthermore, the dehydrating agent is triphenylphosphine;

[0176] Furthermore, the nitrogen heterocyclic base is imidazole;

[0177] Furthermore, the oxidant is iodine;

[0178] Furthermore, the second organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0179] Furthermore, the second organic solvent is dichloromethane;

[0180] Furthermore, the reaction temperature of the Mitsunobu reaction is 10°C-50°C;

[0181] Furthermore, the reaction temperature of the Mitsunobu reaction is 25°C.

[0182] Further, in step S2, the molar ratio of the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, the dehydrating agent, the nitrogen heterocyclic base and the oxidizing agent is 1:(1-4):(1-4):(1-4);

[0183] Furthermore, the molar ratio is 1:1.5:1.5:1.5.

[0184] As described above, referring to FIG4 , step S2 is a process for converting N-(6-hydroxyhexyl)trifluoroacetamide into the corresponding derivative using the Mitsunobu reaction. This reaction utilizes imidazole (an azoheterocyclic base), iodine (I2, an oxidizing agent), and triphenylphosphine (PPh3, a dehydrating agent) as reagents.

[0185] In the Mitsunobu reaction, the specific process includes:

[0186] (1) Prepare the reaction mixture: Mix N-(6-hydroxyhexyl)trifluoroacetamide with imidazole, iodine, and triphenylphosphine in a specified molar ratio (preferably 1:1.5:1.5:1.5) in a suitable second organic solvent at room temperature. Dichloromethane is preferred as the second organic solvent due to its good solubility and compatibility with the Mitsunobu reaction.

[0187] (2) Carrying out the reaction: Stir the mixture under gas protection (usually nitrogen or argon to prevent interference from water and oxygen) and maintain the reaction temperature at around 25°C to promote the reaction.

[0188] (3) Reaction quenching: After a certain reaction time, sodium thiosulfate is added to quench the reaction, neutralize the generated by-products, and stop the further reaction.

[0189] (4) Purification: Purify by concentration and chromatographic separation to obtain the second intermediate.

[0190] The above steps S1 and S2 can be performed simultaneously, or any one of them can be performed first.

[0191] Furthermore, the step S3 is to subject the first intermediate and the second intermediate to a nucleophilic substitution reaction promoted by a nucleophilic agent, potassium carbonate, to obtain a third intermediate, comprising:

[0192] S31, dissolving the first intermediate and the second intermediate in a third organic solvent;

[0193] S32, stirring and heating under a protective atmosphere;

[0194] S33, adding the nucleophilic agent potassium carbonate to carry out a nucleophilic substitution reaction to obtain the third intermediate;

[0195] Furthermore, the amount of the nucleophile potassium carbonate added is 1-3 times the equivalent of the first intermediate;

[0196] Furthermore, the third organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0197] Furthermore, the third organic solvent is N,N-dimethylformamide;

[0198] Furthermore, the reaction temperature of the nucleophilic substitution reaction is 50°C-100°C;

[0199] Furthermore, the reaction temperature of the nucleophilic substitution reaction is 60°C.

[0200] Further, in step S3, the molar ratio of the first intermediate to the second intermediate is 1:(1-4);

[0201] The molar ratio of the first intermediate to potassium carbonate is 1:(1-3);

[0202] Furthermore, the molar ratio of the first intermediate to the second intermediate is 1:1.5;

[0203] Furthermore, the molar ratio of the first intermediate to potassium carbonate is 1:2.

[0204] As mentioned above, referring to FIG5 , step S3, there is provided a method of subjecting the first intermediate and the second intermediate to a nucleophilic substitution reaction in the presence of a nucleophilic agent, potassium carbonate (K 2 CO 3 ), to obtain a third intermediate. The specific process and advantages of this step are as follows:

[0205] The nucleophilic substitution reaction in step S3 may have the following reaction process:

[0206] First, the reactants are prepared: the first intermediate (silane-protected deoxyguanosine) and the second intermediate [N-(6-hydroxyhexyl)trifluoroacetamide derivative obtained by Mitsunobu reaction] are dissolved in a selected third organic solvent according to a certain molar ratio (preferably 1:1.5), preferably N,N-dimethylformamide (DMF) due to its good solubility.

[0207] Next, activation is performed under alkaline conditions: a nucleophile, potassium carbonate (K2CO3), is added to the mixed solution as a nucleophile promoter under alkaline conditions. Potassium carbonate primarily deprotonates the nucleophile in this reaction, enhancing its nucleophilic properties.

[0208] Then, a nucleophilic substitution reaction is carried out: the reaction mixture is stirred under gas protection (usually nitrogen to prevent the reactants and products from being affected by water and oxygen in the air) and at a suitable reaction temperature (preferably 60°C), so that the first intermediate and the second intermediate undergo a nucleophilic substitution reaction through the action of potassium carbonate to generate a mixture containing the third intermediate.

[0209] Finally, post-reaction treatment is performed: After the reaction is completed, appropriate post-treatment is performed, such as adding ice water to the mixture to quench the reaction, filtering and washing, and finally purifying by chromatographic separation to obtain a pure third intermediate.

[0210] The above step S3 has the following advantages: First, under this reaction condition, the nucleophilic substitution reaction has good selectivity and can accurately modify specific functional groups in complex molecules. Secondly, the reaction is carried out in the range of room temperature to 60°C, avoiding side reactions or decomposition that may occur under high temperature conditions. Thirdly, the use of common alkaline promoters (potassium carbonate) and organic solvents is simple to operate and easy to control. Finally, potassium carbonate, as a non-overly strong base, has good compatibility and is suitable for reactions of complex molecules containing multiple functional groups.

[0211] Furthermore, the step S4 comprises taking the third intermediate and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate, comprising:

[0212] S41, dissolving the third intermediate and tetrabutylammonium fluoride in a fourth organic solvent;

[0213] S42, stirring and mixing under a protective atmosphere to perform a desilication protection reaction, and after the reaction is complete, separating and purifying to obtain the fourth intermediate;

[0214] Furthermore, the fourth organic solvent is selected from any one of chloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide;

[0215] Furthermore, the fourth organic solvent is tetrahydrofuran;

[0216] Furthermore, the reaction temperature of the desiliconization protection reaction is 10°C-50°C;

[0217] Furthermore, the reaction temperature of the desiliconization protection reaction is 26°C.

[0218] Further, in step S4, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:(1-4);

[0219] Furthermore, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:1.5.

[0220] As described above, referring to Figure 6, step S4 involves reacting the third intermediate with tetrabutylammonium fluoride (TBAF) to remove the silane protecting group, thereby obtaining the fourth intermediate. This step is a desilylation reaction, which is used to remove the protecting group introduced by the silylation reaction.

[0221] The specific reaction can be carried out through the following specific process:

[0222] Reactant preparation: The third intermediate is dissolved in an appropriate fourth organic solvent, such as tetrahydrofuran (THF), which is preferred due to its good solubility and adaptability to the TBAF reaction.

[0223] Desilication reaction: Add an appropriate amount of tetrabutylammonium fluoride (TBAF) to the mixed solution as a desilication agent. TBAF's primary function in this reaction is to attack the silicon atom on the silane protecting group, removing the protecting group through a nucleophilic substitution reaction and releasing the original functional group (such as a hydroxyl group).

[0224] Reaction conditions: Under gas protection (usually nitrogen or argon), stir the mixture at room temperature (25°C) to mild heating conditions to promote the reaction.

[0225] Post-reaction treatment: After the reaction is completed, appropriate work-up treatment is performed, such as dilution, extraction, washing, drying and chromatographic separation steps to obtain a purified fourth intermediate.

[0226] This step offers several advantages. First, TBAF is a highly effective desilanization agent, specifically capable of removing silane protecting groups without affecting other functional groups in the molecule. Second, this step can be performed at room temperature and is also suitable for mild heating, reducing the risk of potential thermal degradation or side reactions of sensitive functional groups. Third, it is suitable for removing a wide range of different types of silane protecting groups, making it widely applicable in synthetic routes. Finally, using TBAF as a desilanization agent is simple to operate, and the post-processing steps are standardized and easy to execute.

[0227] Furthermore, in S5, the fourth intermediate is subjected to a protecting group introduction reaction using 4,4'-bismethoxytrityl chloride as a protecting group reagent in the presence of a basic promoter, triethylamine, and a nucleic acid catalyst, 4-dimethylaminopyridine, to obtain a fifth intermediate, comprising:

[0228] S51, dissolving the fourth intermediate and 4,4'-bismethoxytrityl chloride in a fifth organic solvent;

[0229] S52, heating and stirring the mixture under a protective atmosphere;

[0230] S53, adding the alkaline promoter triethylamine and the nucleic acid catalyst 4-dimethylaminopyridine to carry out a protecting group introduction reaction, and separating and purifying after the reaction is complete to obtain the fifth intermediate;

[0231] Furthermore, the amount of the basic promoter triethylamine added is 1-3 times the equivalent of the fourth intermediate;

[0232] Furthermore, the fifth organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and pyridine;

[0233] Furthermore, the fifth organic solvent is pyridine;

[0234] Furthermore, the reaction temperature of the protective group introduction reaction is 20°C-80°C;

[0235] Furthermore, the reaction temperature of the protecting group introduction reaction is 40°C.

[0236] Further, in step S5, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:(1-3);

[0237] The molar ratio of the fourth intermediate to triethylamine is 1:(1-3);

[0238] Furthermore, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:2;

[0239] Furthermore, the molar ratio of the fourth intermediate to triethylamine is 1:2.

[0240] As described above, referring to Figure 7, step S5 involves reacting the fourth intermediate with 4,4'-bismethoxytrityl chloride (DMT-Cl) in the presence of triethylamine (TEA) and catalyzed by 4-dimethylaminopyridine (DMAP) to introduce a protecting group to obtain the fifth intermediate. The purpose of this step is to introduce the DMT protecting group into the fourth intermediate.

[0241] The specific process of the reaction may include:

[0242] Reactant preparation: The fourth intermediate is dissolved in a fifth organic solvent, such as pyridine, since pyridine provides good solubility and performs well as a solvent in this type of reaction.

[0243] Protecting Group Introduction: 4,4'-Bismethoxytrityl chloride (DMT-Cl) and triethylamine (TEA) are added to the mixed solution. DMT-Cl acts as a protecting group reagent to protect the active functional group, typically a hydroxyl group, on the fourth intermediate. Triethylamine acts as a base to neutralize the hydrochloric acid (HCl) produced during the reaction.

[0244] Catalytic reaction: A small amount of 4-dimethylaminopyridine (DMAP) is added as a catalyst. DMAP is a highly efficient nucleic acid catalyst that accelerates the reaction between hydroxyl groups and DMT-Cl, improving the efficiency and selectivity of protecting group introduction.

[0245] Reaction conditions: Under gas protection (usually nitrogen or argon), stir the reaction at room temperature to slightly heated conditions (preferably 40° C.) to promote the reaction.

[0246] Post-treatment: After the reaction is completed, appropriate work-up is performed, including dilution, extraction, washing, drying and chromatographic separation steps to obtain a purified fifth intermediate.

[0247] This step reaction has the following advantages: First, the protective group introduction reaction using DMT-Cl under DMAP catalysis can efficiently and selectively protect hydroxyl groups, especially in the synthesis of complex molecules. Second, mild reaction conditions: the reaction is carried out under room temperature to slightly heated conditions, reducing the risk of potential thermal degradation or side reactions of sensitive functional groups. Third, this method is compatible with a variety of functional groups, allowing for the protection of specific functional groups without affecting other functional parts. Finally, the reagents and catalysts used are easily obtained in the laboratory, and the reaction steps are relatively simple and easy to operate.

[0248] Furthermore, the S6, wherein the fifth intermediate is subjected to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine under the catalysis of diisopropylammonium tetrazolium to obtain the N2-C6 amino-modified deoxyguanosine monomer, comprises:

[0249] S61, dissolving the fifth intermediate and bis(diisopropylamino)(2-cyanoethoxy)phosphine in a sixth organic solvent;

[0250] S62, stirring and mixing under a protective atmosphere, adding the catalyst diisopropylammonium tetrazolium salt to perform an activation coupling reaction;

[0251] S63, after the reaction is complete, separation and purification are performed to obtain the N2-C6 amino-modified deoxyguanosine monomer;

[0252] Furthermore, the amount of the catalyst diisopropylammonium tetrazolium added is 1-3 times the equivalent of the fifth intermediate;

[0253] Furthermore, the sixth organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and pyridine;

[0254] Furthermore, the sixth organic solvent is dichloromethane;

[0255] Furthermore, the reaction temperature of the activation coupling reaction is 10°C-50°C;

[0256] Furthermore, the reaction temperature of the activated coupling reaction is 25°C.

[0257] Further, in step S6, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:(1-3);

[0258] The molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:(1-3);

[0259] Furthermore, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:2;

[0260] Furthermore, the molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:2.

[0261] As described above, referring to Figure 8, step S6 is the final step in the synthesis process, involving a chemical reaction between the fifth intermediate and bis(diisopropylamino)(2-cyanoethoxy)phosphine, catalyzed by diisopropylammonium tetrazolium, to synthesize an N2-C6 amino-modified deoxyguanosine monomer. This step is an activated coupling reaction used to introduce a specific amino modification into the fifth intermediate.

[0262] The reaction in this step may include the following specific processes:

[0263] Preparation of reactants: The fifth intermediate, bis(diisopropylamino)(2-cyanoethoxy)phosphine and diisopropylammonium tetrazolium are dissolved in a selected sixth organic solvent, which includes dichloromethane (DCM) and N,N-dimethylformamide (DMF), among which DCM is preferred due to its good solubility and low boiling point.

[0264] Activated coupling reaction: Under a protective atmosphere (usually nitrogen), the mixture is stirred at room temperature (e.g., 25°C). Bis(diisopropylamino)(2-cyanoethoxy)phosphine is used as an activator to promote the coupling reaction. Diisopropylammonium tetrazolium is used as a catalyst to improve reaction efficiency.

[0265] Post-reaction treatment: After the reaction is completed, it may be necessary to add an appropriate quencher to terminate the reaction, and then separate and purify the target product N2-C6 amino-modified deoxyguanosine monomer through conventional extraction, washing and purification steps (such as column chromatography).

[0266] The reaction carried out in step S6 has the following advantages: first, by using bis(diisopropylamino)(2-cyanoethoxy)phosphine and diisopropylammonium tetrazolium, the reaction can efficiently introduce amino modifications at specific positions, which plays a key role in the synthesis of complex modified nucleosides. Secondly, under the reaction conditions, the introduction of amino modifications at specific positions on the deoxyguanosine monomer can be accurately controlled to ensure high selectivity. Thirdly, it is carried out at room temperature, avoiding unnecessary reactions or decomposition of sensitive functional groups that may be caused by high temperatures. Finally, the reagents used are easily available, the reaction steps are relatively simple, and easy to operate and control.

[0267] The present invention is further described below by way of specific examples. However, it should be understood that these examples are merely provided for more detailed description and are not to be construed as limiting the present invention in any form.

[0268] Example 1:

[0269] Experimental methods:

[0270] Step 1: Prepare the first intermediate.

[0271] (1) In a 500 mL three-necked flask, the first reaction raw material deoxyguanosine (20 g, 75 mmol), imidazole (15.3 g, 3.0 eq), 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (23.7 g, 1.0 eq) and the first organic solvent N,N-dimethylformamide 200 mL were added in sequence;

[0272] (2) The reaction was carried out at 25°C for 1 hour to obtain the product.

[0273] (3) The reaction solution was poured into 800 mL of ice water, and a white precipitate was precipitated;

[0274] (4) After filtration, the filter cake was taken and dried to obtain 132 g of the first intermediate.

[0275] Step 2: Prepare the second intermediate.

[0276] (1) Imidazole (8.7 g, 1.5 eq), iodine (32.4 g, 1.5 eq), and triphenylphosphine (33.6 g, 1.5 eq) were added sequentially to a 1 L reaction flask. The second organic solvent was 200 mL of DCM. The mixture was stirred in the dark at 25 °C under nitrogen protection for 0.5 h.

[0277] (2) The second reaction raw material, N-(6-hydroxyhexyl)trifluoroacetamide (18.2 g, 85.47 mmol), was added, the nitrogen atmosphere was replaced, and the mixture was stirred in the dark at room temperature for 1 hour to obtain the product.

[0278] (3) adding sodium thiosulfate to quench, filtering the reaction solution to remove solid triphenylphosphine;

[0279] (4) The reaction solution was concentrated and separated by normal phase column chromatography to obtain 25 g of the second intermediate.

[0280] Step 3: Prepare the third intermediate.

[0281] (1) In a 500 mL reaction flask, the first intermediate (18.0 g, 35.3 mmol), the second intermediate (17.1 g, 1.5 eq), potassium carbonate (12.2 g, 2.0 eq), and the third organic solvent (150 mL of N,N-dimethylformamide) were added in sequence and stirred at 60 °C for 1 h to obtain the product.

[0282] (2) concentrating the reaction solution;

[0283] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 7.0 g of the third intermediate.

[0284] Step 4: Prepare the fourth intermediate.

[0285] (1) The third intermediate (2.8 g, 3.98 mmol), TBAF (2.56 g, 1.5 eq), and 40 mL of tetrahydrofuran (the fourth organic solvent) were added sequentially to a 100 mL reaction bottle and reacted at 25°C for 0.5 h to obtain the product;

[0286] (2) concentrating the reaction solution;

[0287] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 1.0 g of the fourth intermediate.

[0288] Step 5, preparing the fifth intermediate.

[0289] (1) The fourth intermediate (0.8 g, 1.72 mmol), the fifth organic solvent (8 mL of pyridine), 4,4'-bismethoxytrityl chloride (1.16 g, 2.0 eq.), 4-dimethylaminopyridine (0.04 g, 0.2 eq.), and triethylamine (0.26 g, 1.5 eq.) were added sequentially to a 25 mL reaction bottle and reacted at 40°C for 2 h to obtain the product;

[0290] (2) concentrating the reaction solution;

[0291] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.7 g of the fifth intermediate.

[0292] Step 6: Prepare the sixth intermediate.

[0293] (1) The fifth intermediate (0.50 g, 0.66 mmol), diisopropylammonium tetrazolium salt (0.25 g, 2.0 eq), 30 mL of anhydrous dichloromethane (the sixth organic solvent), and bis(diisopropylamino)(2-cyanoethoxy)phosphine (0.39 g, 2.0 eq) were added to a 25 mL reaction flask and reacted at 40 ° C for 2 h to obtain the product.

[0294] (2) diluting the reaction solution with 30 mL of dichloromethane, washing the reaction solution with saturated sodium bicarbonate, water, and saturated brine, respectively, collecting the organic phase and concentrating it;

[0295] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.4 g of the final product, N2-C6 amino-modified deoxyguanosine monomer.

[0296] By performing resonance tests on the final product prepared in Example 1, as shown in the hydrogen spectrum in FIG9 and the phosphorus spectrum in FIG10 , its structure can be determined to be an N2-C6 amino-modified deoxyguanosine monomer.

[0297] Example 2:

[0298] Experimental methods:

[0299] Step 1: Prepare the first intermediate.

[0300] (1) In a 500 mL three-necked flask, the first reaction raw material deoxyguanosine (20 g, 75 mmol), imidazole (5.1 g, 1.0 eq), 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (23.7 g, 1.0 eq) and the first organic solvent N,N-dimethylformamide 200 mL were added in sequence;

[0301] (2) The reaction was carried out at 25°C for 1 hour to obtain the product.

[0302] (3) The reaction solution was poured into 800 mL of ice water, and a white precipitate was precipitated;

[0303] (4) After filtration, the filter cake was taken and dried to obtain 111 g of the first intermediate.

[0304] Step 2: Prepare the second intermediate.

[0305] (1) Imidazole (5.8 g, 1.0 eq), iodine (21.6 g, 1.0 eq), and triphenylphosphine (22.3 g, 1.0 eq) were added sequentially to a 1 L reaction flask. The second organic solvent was 200 mL of DCM. The mixture was stirred in the dark at 25 °C under nitrogen protection for 0.5 h.

[0306] (2) The second reaction raw material, N-(6-hydroxyhexyl)trifluoroacetamide (18.2 g, 85.47 mmol), was added, the nitrogen atmosphere was replaced, and the mixture was stirred at room temperature in the dark for 1 hour to obtain the product.

[0307] (3) adding sodium thiosulfate to quench, filtering the reaction solution to remove solid triphenylphosphine;

[0308] (4) The reaction solution was concentrated and separated by normal phase column chromatography to obtain 8.0 g of the second intermediate.

[0309] Step 3: Prepare the third intermediate.

[0310] (1) In a 500 mL reaction flask, the first intermediate (9.0 g, 17.7 mmol), the second intermediate (5.7 g, 1.0 eq), potassium carbonate (2.4 g, 1.0 eq), and 80 mL of N,N-dimethylformamide (the third organic solvent) were added in sequence and stirred at 60°C for 1 h to obtain the product.

[0311] (2) concentrating the reaction solution;

[0312] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 2.3 g of the third intermediate.

[0313] Step 4: Prepare the fourth intermediate.

[0314] (1) The third intermediate (2.0 g, 2.84 mmol), TBAF (0.8 g, 1.0 eq), and 20 mL of tetrahydrofuran (the fourth organic solvent) were added sequentially into a 100 mL reaction bottle and reacted at 25°C for 0.5 h to obtain the product;

[0315] (2) concentrating the reaction solution;

[0316] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.6 g of the fourth intermediate.

[0317] Step 5, preparing the fifth intermediate.

[0318] (1) The fourth intermediate (0.6 g, 1.29 mmol), the fifth organic solvent (8 mL of pyridine), 4,4'-bismethoxytrityl chloride (0.44 g, 1.0 eq.), 4-dimethylaminopyridine (0.05 g, 0.2 eq.), and triethylamine (0.13 g, 1.0 eq.) were added sequentially to a 25 mL reaction bottle and reacted at 40°C for 2 h to obtain the product;

[0319] (2) concentrating the reaction solution;

[0320] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.1 g of the fifth intermediate.

[0321] Step 6: Prepare the sixth intermediate.

[0322] (1) Add the fifth intermediate (1.0 g, 1.31 mmol), diisopropylammonium tetrazolium salt (0.22 g, 1.0 eq), 5 mL of anhydrous dichloromethane (the sixth organic solvent), and bis(diisopropylamino)(2-cyanoethoxy)phosphine (0.39 g, 1.0 eq) into a 25 mL reaction flask, and react at 40 ° C for 2 h to obtain the product.

[0323] (2) diluting the reaction solution with 30 mL of dichloromethane, washing the reaction solution with saturated sodium bicarbonate, water, and saturated brine, respectively, collecting the organic phase and concentrating it;

[0324] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.2 g of the final product, N2-C6 amino-modified deoxyguanosine monomer.

[0325] By performing resonance tests on the final product prepared in Example 2, as shown in the hydrogen spectrum in FIG11 and the phosphorus spectrum in FIG12 , its structure can be determined to be an N2-C6 amino-modified deoxyguanosine monomer.

[0326] Example 3:

[0327] Experimental methods:

[0328] Step 1: Prepare the first intermediate.

[0329] (1) In a 500 mL three-necked flask, the first reaction raw material deoxyguanosine (20 g, 75 mmol), imidazole (20.4 g, 4.0 eq), 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane (23.7 g, 1.0 eq) and the first organic solvent N,N-dimethylformamide 200 mL were added in sequence;

[0330] (2) The reaction was carried out at 25°C for 1 hour to obtain the product.

[0331] (3) The reaction solution was poured into 800 mL of ice water, and a white precipitate was precipitated;

[0332] (4) After filtration, the filter cake was taken and dried in a spin cycle to obtain 128 g of the first intermediate.

[0333] Step 2: Prepare the second intermediate.

[0334] (1) Imidazole (23.3 g, 4.0 eq), iodine (86.5 g, 4.0 eq), triphenylphosphine (89.2 g, 4.0 eq) were added sequentially to a 1 L reaction flask. The second organic solvent was 400 mL of DCM. The mixture was stirred in the dark at 25 °C for 0.5 h under nitrogen protection.

[0335] (2) The second reaction raw material, N-(6-hydroxyhexyl)trifluoroacetamide (18.2 g, 85.47 mmol), was added, the nitrogen atmosphere was replaced, and the mixture was stirred at room temperature in the dark for 1 hour to obtain the product.

[0336] (3) adding sodium thiosulfate to quench, filtering the reaction solution to remove solid triphenylphosphine;

[0337] (4) The reaction solution was concentrated and separated by normal phase column chromatography to obtain 18.0 g of the second intermediate.

[0338] Step 3: Prepare the third intermediate.

[0339] (1) In a 500 mL reaction flask, the first intermediate (9.0 g, 17.7 mmol), the second intermediate (22.9 g, 4.0 eq), potassium carbonate (7.4 g, 3.0 eq), and 80 mL of N,N-dimethylformamide (the third organic solvent) were added in sequence and stirred at 60°C for 1 h to obtain the product.

[0340] (2) concentrating the reaction solution;

[0341] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 2.1 g of the third intermediate.

[0342] Step 4: Prepare the fourth intermediate.

[0343] (1) The third intermediate (2.0 g, 2.84 mmol), TBAF (3.0 g, 4.0 eq), and 20 mL of tetrahydrofuran (the fourth organic solvent) were added sequentially into a 100 mL reaction bottle and reacted at 25°C for 0.5 h to obtain the product;

[0344] (2) concentrating the reaction solution;

[0345] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.6 g of the fourth intermediate.

[0346] Step 5, preparing the fifth intermediate.

[0347] (1) The fourth intermediate (0.6 g, 1.29 mmol), the fifth organic solvent (8 mL of pyridine), 4,4'-bismethoxytrityl chloride (1.3 g, 3.0 eq.), 4-dimethylaminopyridine (0.05 g, 0.2 eq.), and triethylamine (0.39 g, 3.0 eq.) were added sequentially to a 25 mL reaction bottle and reacted at 40°C for 2 h to obtain the product;

[0348] (2) concentrating the reaction solution;

[0349] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.5 g of the fifth intermediate.

[0350] Step 6: Prepare the sixth intermediate.

[0351] (1) Add the fifth intermediate (1.0 g, 1.31 mmol), diisopropylammonium tetrazolium salt (0.67 g, 3.0 eq), 5 mL of anhydrous dichloromethane (the sixth organic solvent), and bis(diisopropylamino)(2-cyanoethoxy)phosphine (1.18 g, 3.0 eq) into a 25 mL reaction bottle, and react at 40 ° C for 2 h to obtain the product.

[0352] (2) diluting the reaction solution with 30 mL of dichloromethane, washing the reaction solution with saturated sodium bicarbonate, water, and saturated brine, respectively, collecting the organic phase and concentrating it;

[0353] (3) Purification was performed using a reverse phase C18 preparative chromatography column (ACN / H2O) to obtain 0.8 g of the final product, N2-C6 amino-modified deoxyguanosine monomer.

[0354] By performing resonance tests on the final product prepared in Example 3, as shown in the hydrogen spectrum in FIG13 and the phosphorus spectrum in FIG14 , its structure can be determined to be an N2-C6 amino-modified deoxyguanosine monomer.

[0355] In summary, the present invention uses deoxyguanosine and N-(6-hydroxyhexyl)trifluoroacetamide as raw materials, and respectively undergoes a silane protection reaction, a Mitsunobu reaction, a nucleophilic substitution reaction, a protecting group introduction reaction, and an activation coupling reaction to prepare the final product, an N2-C6 amino-modified deoxyguanosine monomer. The chemical raw materials used in the synthesis method are simple and readily available, with low cost; the reaction conditions are mild, and scale-up production is easy; the obtained intermediate is highly stable; and the purification method is simple and easy to operate.

[0356] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for synthesizing an N2-C6 amino-modified deoxyguanosine monomer, characterized in that: include: S1, subjecting the first reaction raw material, deoxyguanosine, to a silane protection reaction under the protection of a silanization reagent, 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalysis of a catalyst, imidazole, to obtain a first intermediate; S2, taking the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and performing a Mitsunobu reaction in the presence of a dehydrating agent, an azocyclic base, and an oxidizing agent to obtain a second intermediate; S3, subjecting the first intermediate and the second intermediate to a nucleophilic substitution reaction promoted by a nucleophile, potassium carbonate, to obtain a third intermediate; S4, taking the third intermediate and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate; S5, using 4,4'-bismethoxytrityl chloride as a protecting group reagent, the fourth intermediate is subjected to a protecting group introduction reaction under the conditions of a basic promoter triethylamine and a nucleic acid catalyst 4-dimethylaminopyridine to obtain a fifth intermediate; S6, subjecting the fifth intermediate to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine in the presence of diisopropylammonium tetrazolium as a catalyst to obtain the N2-C6 amino-modified deoxyguanosine monomer.

2. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: Said S1, the first reaction raw material deoxyguanosine is subjected to a silane protection reaction under the protection of a silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalysis of a catalyst imidazole to obtain a first intermediate, comprising: S11, adding the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane, and the catalyst imidazole to a first organic solvent at room temperature; S12, stirring and mixing to perform a silane protection reaction, and terminating the reaction with ice water after the reaction is complete, thereby obtaining the first intermediate; Preferably, the first organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide; Preferably, the organic solvent is N,N-dimethylformamide; Preferably, the reaction temperature of the silane protection reaction is 10°C-50°C; Preferably, the reaction temperature of the silane protection reaction is 25°C; Preferably, in step S1, the molar ratio of the first reaction raw material deoxyguanosine, the silanization reagent 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and the catalyst imidazole is 1:1:(1-4); Preferably, the molar ratio is 1:1:

3.

3. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: Said S2, taking the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, and carrying out Mitsunobu reaction under the action of a dehydrating agent, an azoheterocyclic base and an oxidizing agent to obtain a second intermediate, comprising: S21, adding the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, a dehydrating agent, an azocyclic base, and an oxidizing agent to a second organic solvent at room temperature; S22, performing a Mitsunobu reaction under a protective atmosphere, and after the reaction is complete, adding sodium thiosulfate to quench the reaction to obtain a reaction mixture; S23, concentrating the reaction mixture and purifying it by chromatography to obtain the second intermediate; Preferably, the dehydrating agent is triphenylphosphine; Preferably, the nitrogen heterocyclic base is imidazole; Preferably, the oxidizing agent is iodine; Preferably, the second organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide; Preferably, the second organic solvent is dichloromethane; Preferably, the reaction temperature of the Mitsunobu reaction is 10°C-50°C; Preferably, the reaction temperature of the Mitsunobu reaction is 25°C; Preferably, in step S2, the molar ratio of the second reaction raw material N-(6-hydroxyhexyl)trifluoroacetamide, the dehydrating agent, the nitrogen heterocyclic base and the oxidizing agent is 1:(1-4):(1-4):(1-4); Preferably, the molar ratio is 1:1.5:1.5:1.

5.

4. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: The step S3 is to subject the first intermediate and the second intermediate to a nucleophilic substitution reaction promoted by a nucleophilic agent, potassium carbonate, to obtain a third intermediate, comprising: S31, dissolving the first intermediate and the second intermediate in a third organic solvent; S32, stirring and heating under a protective atmosphere; S33, adding the nucleophilic agent potassium carbonate to carry out a nucleophilic substitution reaction to obtain the third intermediate; Preferably, the amount of the nucleophile potassium carbonate added is 1-3 times the equivalent of the first intermediate; Preferably, the third organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide; Preferably, the third organic solvent is N,N-dimethylformamide; Preferably, the reaction temperature of the nucleophilic substitution reaction is 50°C-100°C; Preferably, the reaction temperature of the nucleophilic substitution reaction is 60°C; Preferably, in step S3, the molar ratio of the first intermediate to the second intermediate is 1:(1-4); The molar ratio of the first intermediate to potassium carbonate is 1:(1-3); Preferably, the molar ratio of the first intermediate to the second intermediate is 1:1.5; Preferably, the molar ratio of the first intermediate to potassium carbonate is 1:

2.

5. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: Said S4, taking said third intermediate, and performing a desilication protection reaction with tetrabutylammonium fluoride to obtain a fourth intermediate, comprising: S41, dissolving the third intermediate and tetrabutylammonium fluoride in a fourth organic solvent; S42, stirring and mixing under a protective atmosphere to perform a desilication protection reaction, and after the reaction is complete, separating and purifying to obtain the fourth intermediate; Preferably, the fourth organic solvent is selected from any one of chloromethane, N,N-dimethylformamide, tetrahydrofuran and dimethyl sulfoxide; Preferably, the fourth organic solvent is tetrahydrofuran; Preferably, the reaction temperature of the desilication protection reaction is 10°C-50°C; Preferably, the reaction temperature of the desilication protection reaction is 26°C.

6. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 5, wherein: In step S4, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:(1-4); Preferably, the molar ratio of the third intermediate to tetrabutylammonium fluoride is 1:1.

5.

7. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: Said S5, using 4,4'-bismethoxytrityl chloride as a protecting group reagent, carries out a protecting group introduction reaction on the fourth intermediate in the presence of a basic promoter triethylamine and a nucleic acid catalyst 4-dimethylaminopyridine to obtain a fifth intermediate, comprising: S51, dissolving the fourth intermediate and 4,4'-bismethoxytrityl chloride in a fifth organic solvent; S52, heating and stirring the mixture under a protective atmosphere; S53, adding the alkaline promoter triethylamine and the nucleic acid catalyst 4-dimethylaminopyridine to carry out a protecting group introduction reaction, and separating and purifying after the reaction is complete to obtain the fifth intermediate; Preferably, the amount of the basic promoter triethylamine added is 1-3 times the equivalent of the fourth intermediate; Preferably, the fifth organic solvent is selected from any one of dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide, and pyridine; Preferably, the fifth organic solvent is pyridine; Preferably, the reaction temperature of the protecting group introduction reaction is 20°C-80°C; Preferably, the reaction temperature of the protecting group introduction reaction is 40°C.

8. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 7, wherein: In step S5, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:(1-3); The molar ratio of the fourth intermediate to triethylamine is 1:(1-3); Preferably, the molar ratio of the fourth intermediate to 4,4'-bismethoxytrityl chloride is 1:2; Preferably, the molar ratio of the fourth intermediate to triethylamine is 1:

2.

9. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 1, wherein: The step S6, wherein the fifth intermediate is subjected to an activation coupling reaction with bis(diisopropylamino)(2-cyanoethoxy)phosphine under the catalysis of diisopropylammonium tetrazolium to obtain the N2-C6 amino-modified deoxyguanosine monomer, comprises: S61, dissolving the fifth intermediate and bis(diisopropylamino)(2-cyanoethoxy)phosphine in a sixth organic solvent; S62, stirring and mixing under a protective atmosphere, adding the catalyst diisopropylammonium tetrazolium salt to perform an activation coupling reaction; S63, after the reaction is complete, separation and purification are performed to obtain the N2-C6 amino-modified deoxyguanosine monomer; Preferably, the amount of the catalyst diisopropylammonium tetrazolium added is 1-3 times the equivalent of the fifth intermediate; Preferably, the sixth organic solvent is selected from dichloromethane, N,N-dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and pyridine Any of; Preferably, the sixth organic solvent is dichloromethane; Preferably, the reaction temperature of the activated coupling reaction is 10°C-50°C; Preferably, the reaction temperature of the activated coupling reaction is 25°C.

10. The method for synthesizing the N2-C6 amino-modified deoxyguanosine monomer according to claim 9, wherein: In step S6, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:(1-3); The molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:(1-3); Preferably, the molar ratio of the fifth intermediate to bis(diisopropylamino)(2-cyanoethoxy)phosphine is 1:2; Preferably, the molar ratio of the fifth intermediate to diisopropylammonium tetrazolium is 1:2.

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