A process for the preparation of 9-fluorenylmethyl-n-succinimidyl carbonate

Abstract

The application belongs to the field of organic matter preparation, and particularly relates to a preparation method of 9-fluorenylmethyl-N-succinimidyl carbonate, wherein N-hydroxy succinimide is dissolved and mixed with dry chloroformate-9-fluorenylmethyl ester and a silicon-based solid base for reaction, water is used for quenching and washing after the reaction is completed, and 9-fluorenylmethyl-N-succinimidyl carbonate is obtained after drying and purification; an ester group is doped on the solid base. The method can obtain high-quality and high-purity products, can meet the demand of high-precision experiments on product purity, and is simple to operate and suitable for industrial promotion.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of organic matter preparation, and particularly relates to a preparation method of 9-fluorenylmethyl-N-succinimidyl carbonate. BACKGROUND

[0002] 9-Fluorenylmethyl-N-succinimidyl carbonate is used for preparing Fmoc-amino acid derivatives, can selectively protect hydroxyl-containing amino acids, is stable and efficient, has small impurities and fast reaction. The preparation of 9-fluorenylmethyl-N-succinimidyl carbonate is based on chloroformic acid-9-fluorenylmethyl ester and increases one step of reaction, and the one-time yield is only 65-70%, and the impurities are not easy to separate. Since it is based on the reaction of chloroformic acid-9-fluorenylmethyl ester, the problems brought by adding raw materials, solvents and alkali into the kettle first and then adding solid phosgene in batches during the preparation of chloroformic acid-9-fluorenylmethyl ester also exist here. In addition, the original production process of 9-fluorenylmethyl-N-succinimidyl carbonate adopts an aqueous solution and an inorganic alkali system, and the materials are prone to hydrolysis during the reaction process to produce impurities, and the impurities are not easy to separate. SUMMARY

[0003] In order to solve the problems in the prior art that the production process of 9-fluorenylmethyl-N-succinimidyl carbonate is prone to produce impurities which are difficult to separate, the alkali content needs to be accurately controlled, the technical difficulty is large, and the cost is high, the present application mainly provides a preparation method of 9-fluorenylmethyl-N-succinimidyl carbonate with high yield and high purity. The technical scheme is as follows:

[0004] A preparation method of 9-fluorenylmethyl-N-succinimidyl carbonate, comprising the following steps: dissolving N-hydroxy succinimide, mixing with dry chloroformic acid-9-fluorenylmethyl ester and silicon-based solid alkali for reaction, quenching and water washing after the reaction is completed, drying and purifying to obtain 9-fluorenylmethyl-N-succinimidyl carbonate; the solid alkali is doped with an ester group.

[0005] .

[0006] Further, the solvent in the reaction system is an organic solvent; the molar ratio of N-hydroxy succinimide to chloroformic acid-9-fluorenylmethyl ester is 1.1-1.5:1; and the mass ratio of chloroformic acid-9-fluorenylmethyl ester to solid alkali is 1:0.7-1.2.

[0007] Further, the preparation of the solid alkali comprises the following steps: preparing a silicon-based matrix full of silicon hydroxyl groups; using methyl chloroacetate to partially graft the silicon-based matrix to obtain a partially modified matrix; and then using a coupling agent containing an imidazole group to continue modification to obtain the solid alkali.

[0008] Further, the preparation of the solid alkali comprises the following steps:

[0009] Methyl chloroacetate is dissolved in toluene to obtain a methyl chloroacetate solution; the silicon-based substrate and sodium bicarbonate in water are mixed, and then the methyl chloroacetate solution is added; after uniform mixing, reaction is carried out at 30-50℃ for 2-4h; the product is separated, washed thoroughly, and dried to obtain a partially modified substrate;

[0010] The partially modified substrate is mixed with triethoxy-3-(2-imidazolin-1-yl)propylsilane in ethanol, and dilute sulfuric acid is added; reaction is carried out at 70-80℃ for 18-30h; the product is collected, washed thoroughly, and dried to obtain a precursor;

[0011] The precursor is dispersed in dichloromethane, and triethylamine is added; reaction is carried out at 5-15℃ for 3-5h; the solvent is evaporated; the product is washed thoroughly and dried to obtain a solid base.

[0012] Further, the average particle size of the silicon-based substrate is 50-100nm, and the pore size is 2-10nm; the mass ratio of the ethyl chloroformate to the silicon-based substrate is 1:3-5; and the mass ratio of the ethyl chloroformate to sodium bicarbonate is 1:2-3.

[0013] Further, the mass ratio of the partially modified substrate to triethoxy-3-(2-imidazolin-1-yl)propylsilane is 1:1.2-1.8; the volume ratio of the ethanol to dilute sulfuric acid is 1-3:1; and the mass concentration of sulfuric acid in the dilute sulfuric acid is not more than 20%.

[0014] Further, the mass ratio of the triethylamine to the precursor is 1.5-2:1.

[0015] Further, the method comprises the following steps:

[0016] Dry chloroformic acid-9-fluorenylmethyl ester is dissolved in an organic solvent; N-hydroxysuccinimide and a solid base are mixed in the organic solvent to obtain a reaction solution; the system is cooled to below 5℃, and the reaction solution is added dropwise; after the dropwise addition is completed, reaction is carried out at room temperature, and the reaction is controlled; quenching is carried out, saturated brine is washed, and the product is filtered, dried, and purified to obtain 9-fluorenylmethyl-N-succinimidyl carbonate.

[0017] Further, the time for dropwise addition of the reaction solution is 6-10h.

[0018] Further, the solid base is dispersed in dichloromethane, and triethylamine is added; reaction is carried out at 5-15℃ for 3-5h; the solvent and unreacted triethylamine are evaporated; the product is washed thoroughly and dried to complete regeneration.

[0019] By using the above scheme, the method has the following advantages:

[0020] 1. The preparation method of the application is carried out in a water-free and solid base system, which solves the problem of easy hydrolysis of chloroformic acid-9-fluorenylmethyl ester in a water solution and inorganic base system, prevents the generation of impurities, and the solid base is easy to separate, solving the problem of difficult separation of organic base, significantly increasing the yield and purity.

[0021] 2. The solid base of the application is in a solid state, which is significantly different from the reactants and products in a liquid state in physical properties, and can be separated from the reaction system by simple physical methods such as filtration and centrifugation after the reaction is completed, which is simple to operate, reduces the separation cost and the influence on the purity of the product.

[0022] 3. The solid base of the application has high selectivity as an acid-binding agent for the preparation of 9-fluorenylmethyl-N-succinimidyl carbonate from chloroformic acid-9-fluorenylmethyl ester, has suitable basicity, has good acid-binding effect, and makes the reaction system maintain a near neutral condition; and the high specific surface area and suitable pore size of the solid base are beneficial to the diffusion of the reactants and products and promote the reaction.

[0023] 4. The high specific surface area of the solid base of the application enables the surface to load more imidazole groups, and the hydroxyl chain of the imidazole group is relatively long, the reaction steric hindrance between the imidazole group, chloroformic acid-9-fluorenylmethyl ester and N-hydroxy succinimide is small, and the reaction is easy to proceed.

[0024] 5. The solid base of the application first grafts the chlorine in chloroformic acid ethyl ester with the silicon hydroxyl group to load a small amount of ester group on the surface of the solid base, and then introduces the imidazole group; the ester group is uniformly distributed between the imidazole groups, which can regulate the distance between the imidazole groups and reduce the steric hindrance, and the ester group and the imidazole group form a catalytic promotion effect; and the ester group can form a competitive reaction with chloroformic acid-9-fluorenylmethyl ester for the trace amount of water molecules generated in the reaction process or the extremely small amount of water that cannot be avoided, which prevents the hydrolysis of chloroformic acid-9-fluorenylmethyl ester.

[0025] 6. The solid base catalyst of the application can be deprotonated by a simple method after the preparation of 9-fluorenylmethyl-N-succinimidyl carbonate, realizing the regeneration of the solid base, which can be repeatedly used for many times, reducing the amount of catalyst used, lowering the cost, and reducing the generation of waste; and the ester group on the solid base is consumed very little, and the ester group is not regenerated for cost consideration.

[0026] 7. Compared with the yield of 65-70% and the purity of 99% reached by the existing process, the preparation method of the application can make the yield reach more than 80% and the purity reach more than 99.5%, even reaching 99.9%, which can obtain high-quality and high-purity products, meet the demand of high-precision experiments for product purity, solve the problem of bottleneck of product purity improvement in the prior art, and the preparation operation is simple and suitable for industrial promotion. Attached Figure Description

[0027] Fig. 1 The liquid chromatogram of the product of Example 1 of the present invention;

[0028] Fig. 2 The liquid chromatogram of the product of Example 2 of the present invention;

[0029] Fig. 3 This is a liquid chromatogram of the product of Example 3 of the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: (1) Dissolve 0.5g of methyl chloroacetate in 25mL of toluene to obtain a methyl chloroacetate solution; mix 2g of mesoporous silicon matrix with an average particle size of 80nm and a pore size of 3nm and 1.2g of sodium bicarbonate in water, then add it to the methyl chloroacetate solution, mix evenly and react at 40℃ for 3h; separate the product, wash thoroughly, and dry at 60℃ to obtain a partially modified matrix;

[0032] (2) 1.5g of the modified matrix and 2.3g of triethoxy-3-(2-imidazolin-1-yl)propylsilane were placed in 100mL of anhydrous ethanol and mixed thoroughly. 70mL of 10% dilute sulfuric acid was added and the mixture was reacted at 75℃ for 24h. The product was collected, washed thoroughly and dried at 60℃ to obtain the precursor.

[0033] (3) Take 2g of precursor and disperse it fully in dichloromethane, add 3.5g of triethylamine, react at 10℃ for 4h, remove the solvent and unreacted triethylamine in stages, wash thoroughly and dry to obtain solid base;

[0034] (4) Fluorene-methanol and solid phosgene are reacted in dichloromethane to prepare 9-fluorenyl methyl chloroformate; the prepared 9-fluorenyl methyl chloroformate is thoroughly dried;

[0035] (5) 0.6 g N-hydroxysuccinimide and 1 g solid base were uniformly dispersed in dichloromethane to obtain a reaction solution; 1 g of dry 9-fluorenylmethyl chloroformate was dissolved in dichloromethane; the system was cooled to 0°C, and the reaction solution was added dropwise, and the dropwise addition was completed in 8 h, and then the reaction was carried out at room temperature; after the completion of the reaction, the reaction was quenched, washed with saturated brine, and then filtered and dried to enter the crystallization kettle; part of the solution was distilled, petroleum ether was added for crystallization, centrifuged and dried to obtain the finished product; the yield was 88.3%, and the purity was 99.95%.

[0036] Example 2: The difference from Example 1 is that:

[0037] (1) 0.5 g of methyl chloroacetate was dissolved in 25 mL of toluene to obtain a methyl chloroacetate solution; 2.5 g of a silicon-based matrix with an average particle size of 80 nm and a pore size of 3 nm, and 1.2 g of sodium bicarbonate were mixed in water, and then the methyl chloroacetate solution was added, and after being uniformly mixed, the reaction was carried out at 40°C for 3 h; the product was separated, washed thoroughly, and dried at 60°C to obtain a partially modified matrix; the yield was 85.8%, and the purity was 99.85%.

[0038] Example 3: The difference from Example 1 is that:

[0039] (1) 0.5 g of methyl chloroacetate was dissolved in 25 mL of toluene to obtain a methyl chloroacetate solution; 1.5 g of a silicon-based matrix with an average particle size of 80 nm and a pore size of 3 nm, and 1.2 g of sodium bicarbonate were mixed in water, and then the methyl chloroacetate solution was added, and after being uniformly mixed, the reaction was carried out at 40°C for 3 h; the product was separated, washed thoroughly, and dried at 60°C to obtain a partially modified matrix; the yield was 86.4%, and the purity was 99.77%.

[0040] Example 4: The difference from Example 1 is that:

[0041] (2) 1.5 g of the partially modified matrix was mixed with 2.3 g of triethoxy-3-(2-imidazoline-1-yl) propyl silane in 100 mL of anhydrous ethanol, 100 mL of 10% mass concentration dilute sulfuric acid was added, and the reaction was carried out at 75°C for 24 h; the product was collected, washed thoroughly and dried at 60°C to obtain a precursor; the yield was 82.9%, and the purity was 99.64%.

[0042] Example 5: The difference from Example 1 is that:

[0043] (2) 1.5 g of the partially modified matrix was mixed with 2.3 g of triethoxy-3-(2-imidazoline-1-yl) propyl silane in 100 mL of anhydrous ethanol, 35 mL of 10% mass concentration dilute sulfuric acid was added, and the reaction was carried out at 75°C for 24 h; the product was collected, washed thoroughly and dried at 60°C to obtain a precursor; the yield was 85.4%, and the purity was 99.79%.

[0044] Example 6: The difference from Example 1 is that:

[0045] (3) 2 g of the precursor was dispersed in dichloromethane, 3 g of triethylamine was added, and the reaction was carried out at 10°C for 4 h. The unreacted triethylamine and solvent were removed by fractional distillation, and the product was washed and dried to obtain a solid base; the yield was 81.8%, and the purity was 99.58%.

[0046] Comparative Example: The difference from Example 1 is that:

[0047] Fluorene methyl alcohol and solid carbonyl chloride were reacted in dichloromethane to obtain chloroformic acid-9-fluorenylmethyl ester. 0.5-0.7 g of N-hydroxy succinimide was dissolved in water, and then mixed with 1 g of the obtained chloroformic acid-9-fluorenylmethyl ester. 0.7-1.2 g of sodium carbonate was added, and the reaction was carried out for 3-4 h. The crude product was filtered and purified to obtain the product; the yield was 68.3%, and the purity was 99.24%.

[0048] Example sample test:

[0049] The appearance of the samples of each example was visually inspected, and white or light yellow powder was qualified. The melting point of the samples of each example was tested using a melting point apparatus, and the melting point of 147-151°C was qualified. The drying loss of the samples of each example was tested by a moisture meter, and the maximum was not more than 0.5%. 1 g of the sample of each example was dissolved in 10 mL of acetonitrile, and the clarity was observed, and the clear and transparent sample was qualified. The sample content was tested by a high performance liquid chromatograph. The results are as follows:

[0050]

[0051] According to the liquid chromatogram of the above table and Figs. 1-3 It can be seen from the signal on the chromatogram that the signal corresponds to 9-fluorenylmethyl-N-succinimidyl carbonate, and there is no obvious unknown signal. The purity of the obtained product is at least 99.77%, and even can reach 99.95%, and the impurities are very few. It is proved that the method of the present application can produce high-purity 9-fluorenylmethyl-N-succinimidyl carbonate. The appearance and melting point of the sample prepared by the method of Comparative Example 1 are different from those of the sample prepared by the present application, and there are more obvious impurities in the sample, and the yield is less than 70%, and the purity is also much lower than that of each example. It is proved that the method of the present application can significantly improve the yield and purity of 9-fluorenylmethyl-N-succinimidyl carbonate.

[0052] The content of methyl chloroacetate directly relates to the distribution of silicon hydroxyl in the silicon-based substrate in the step of modification of step (1) using methyl chloroacetate. The more the content of methyl chloroacetate, the less the silicon hydroxyl remaining for imidazole grafting. By changing the ratio of the silicon-based substrate to ethyl chloroformate, thereby changing the grafting ratio of methyl chloroacetate to triethoxyl-3-(2-imidazoline-1-yl) propyl silane, the sample yield and content of examples 2 and 3 are both decreased compared with example 1. In the order of 0.1%, the decrease of content is not only affected by error factors, but also by the change of formula, which shows that the grafting ratio of ester group and imidazole will affect the purity of the product. More dilute sulfuric acid is added in example 4, and the sample yield and content are both decreased compared with example 1. It is possible that the degree of protonation of imidazole group is higher, and the difficulty of deprotonation after grafting is also higher, so the alkalinity of solid base is easily affected. The content of dilute sulfuric acid in example 5 is less, and the yield and content are also less than those of example 1. It is possible that the inhibition of ester group hydrolysis by less sulfuric acid is decreased, and the capture of free water molecules by the remaining ester group on the solid base is also decreased. The content of triethylamine added for deprotonation of imidazole in example 6 is less, which will affect the deprotonation effect, and the yield and content of example 6 are decreased.

[0053] For those skilled in the art, various corresponding changes and modifications can be made to the technical solutions and concepts described above, and all these changes and modifications should belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing 9-fluorenylmethyl-N-succinimide carbonate, characterized in that, The process includes the following steps: dissolving N-hydroxysuccinimide, reacting it with dried chloroformate-9-fluorenylmethyl ester and a silicon-based solid base, quenching and washing with water after the reaction is complete, drying and purifying to obtain 9-fluorenylmethyl-N-succinimide carbonate; the solid base is doped with ester groups; The preparation of the solid alkali includes the following steps: Methyl chloroacetate was dissolved in toluene to obtain a methyl chloroacetate solution. A silicon-based matrix with an average particle size of 50-100 nm and a pore size of 2-10 nm was mixed with sodium bicarbonate in water, and then added to the methyl chloroacetate solution. After mixing evenly, the mixture was reacted at 30-50°C for 2-4 hours. The product was separated, thoroughly washed, and dried to obtain a partially modified matrix. The mass ratio of ethyl chloroformate to silicon-based matrix was 1:3-5, and the mass ratio of ethyl chloroformate to sodium bicarbonate was 1:2-3. A portion of the modified matrix and triethoxy-3-(2-imidazolin-1-yl)propylsilane were thoroughly mixed in ethanol, and dilute sulfuric acid with a mass concentration not exceeding 20% ​​was added. The mixture was reacted at 70-80°C for 18-30 h. The product was collected, thoroughly washed, and dried to obtain the precursor. The mass ratio of the modified matrix to triethoxy-3-(2-imidazolin-1-yl)propylsilane was 1:1.2-1.8; the volume ratio of ethanol to dilute sulfuric acid was 1-3:

1. The precursor was fully dispersed in dichloromethane, triethylamine was added, and the reaction was carried out at 5-15°C for 3-5 hours. The solvent was evaporated, and the product was thoroughly washed and dried to obtain a solid base.

2. The method for preparing 9-fluorenylmethyl-N-succinimide carbonate according to claim 1, characterized in that, The solvent in the reaction system is an organic solvent; the molar ratio of N-hydroxysuccinimide to 9-fluorenyl chloroformate is 1.1~1.5:1; the mass ratio of 9-fluorenyl chloroformate to solid base is 1:0.7~1.

2.

3. The method for preparing 9-fluorenylmethyl-N-succinimide carbonate according to claim 1, characterized in that, The mass ratio of triethylamine to the precursor is 1.5 to 2:

1.

4. The method for preparing 9-fluorenylmethyl-N-succinimide carbonate according to claim 1, characterized in that, Includes the following steps: Take dried chloroformate-9-fluorenyl methyl ester and dissolve it thoroughly in an organic solvent; mix N-hydroxysuccinimide and solid base in an organic solvent to obtain a reaction solution; cool the system to below 5°C and add the reaction solution dropwise; after the addition is complete, react at room temperature and control the reaction to complete; quench, wash with saturated brine, filter, dry and purify to obtain 9-fluorenylmethyl-N-succinimide carbonate.

5. The method for preparing 9-fluorenylmethyl-N-succinimide carbonate according to claim 4, characterized in that, The time required for the dropwise addition of the reaction solution is 6 to 10 hours.

6. The method for preparing 9-fluorenylmethyl-N-succinimide carbonate according to any one of claims 1 to 5, characterized in that, The solid base is fully dispersed in dichloromethane, triethylamine is added, and the reaction is carried out at 5-15°C for 3-5 hours. The solvent and unreacted triethylamine are removed by evaporation, and the mixture is thoroughly washed and dried to complete the regeneration.

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