Synthesis process for vitamin c ethyl ether

Abstract

The present invention belongs to the technical field of the synthesis of vitamin C derivatives. Disclosed is a synthesis process for vitamin C ethyl ether. The process comprises the following steps: taking L-ascorbic acid as a raw material, adding acetone, anhydrous cupric sulfate and acetyl chloride thereto, and reacting same under the protection of nitrogen at 38-40°C for 1-2 h to obtain a vitamin C protector; adding an alkali, water, an alkylating reagent and absolute ethyl alcohol to the reaction product, reacting same under the protection of nitrogen at 75-78°C for 3 h, and performing reduced-pressure distillation to obtain a vitamin C protector etherate; and finally, performing hydrolysis by using a cationic resin, removing a protecting group, and performing recrystallization by using ethyl acetate to obtain vitamin C ethyl ether. By means of the synergistic catalysis of anhydrous cupric sulfate and acetyl chloride, the process significantly shortens the reaction time, and improves the product purity and yield. The product purity is determined to be more than 99.5%, and the total yield can reach 80% or higher. Thus, an efficient and economical method is provided for the industrial production of vitamin C ethyl ether.

Description

A Synthesis Process for Vitamin C Ethyl Ether Technical Field

[0001] This invention belongs to the field of vitamin C derivative synthesis technology, specifically, it relates to a synthesis process for vitamin C ethyl ether. Background Technology

[0002] Ethyl vitamin C ether is a very useful vitamin C derivative. It is not only chemically stable and colorfast, but also an amphoteric substance, greatly expanding its applications, especially in cosmetics. Ethyl vitamin C ether easily penetrates the stratum corneum into the dermis. Once inside the body, it is readily broken down by enzymes, thus exerting the whitening, antioxidant, and collagen-boosting effects of vitamin C. Therefore, ethyl vitamin C ether is a crucial ingredient in cosmetic anti-aging and whitening agents.

[0003] There are one-step and three-step methods for synthesizing vitamin C ethyl ether. Patent CN100586941C discloses a one-step method for the separation and purification of 3-O-alkyl ascorbic acid ether from vitamin C. The preparation steps include mixing vitamin C, a base, and an alkylating agent in a solvent to react and synthesize 3-O-alkyl ascorbic acid ether. After the reaction, the reaction solvent is recovered, the residue is diluted with water, and ion exchange is performed using a strongly basic anion exchange resin column. The mixture is then washed with water, eluted with dilute acid, concentrated, and crystallized to obtain purified vitamin C ethyl ether. This method produces complex reaction products, is difficult to separate and purify, has a low yield, and is difficult to scale up for industrial production. The more common method for synthesizing vitamin C ethyl ether is the three-step method. Patent CN103113333B discloses a method for synthesizing vitamin C ethyl ether. First, vitamin C is used as a raw material, acetone dimethyl acetal as a reactant, and DMSO as a solvent. Under the action of a catalyst, the hydroxyl groups at the 5 and 6 positions of vitamin C are protected. Then, a base and an alkylating agent are added to react and form an ether bond at the 3-position hydroxyl group. Finally, the protecting groups at the 5 and 6 positions are removed by acid treatment, and vitamin C ethyl ether is obtained by crystallization with a lipid-soluble solvent. The overall yield of the three steps is 50%-50.4%. Patent CN113214197B discloses a method for preparing vitamin C ethyl ether. First, vitamin C is used as a starting material, cyclopentanone as a reactant and solvent. 5,6-O-cyclopentyl-ascorbic acid is obtained under the catalysis of acetyl chloride. Then, thionyl chloride, ethanol, and triethylamine are added to react and obtain 3-O-ethyl-5,6-O-cyclopentyl-ascorbic acid ether. Finally, the protecting group is removed by reaction with dilute hydrochloric acid, and vitamin C ethyl ether is obtained by recrystallization with ethanol. Patent CN112142697B discloses a production process for vitamin C ethyl ether. Using vitamin C as the starting material, vitamin C ethyl ether is obtained through acetone protection, etherification, and hydrolysis protection. The third step involves hydrolysis of the protecting group with concentrated hydrochloric acid and recrystallization with n-butanol. The yield of vitamin C ethyl ether can reach more than 65%.

[0004] Currently, the reaction of vitamin C with acetone to produce the intermediate 5,6-O-isopropyl-L-ascorbic acid typically takes 3-5 hours. This prolonged reaction not only increases energy consumption but also limits production efficiency. The extended reaction time can lead to increased byproducts, reducing the purity of the target product and consequently affecting subsequent purification steps. Furthermore, in existing technologies, after removing the protecting group using ion exchange resins or dilute hydrochloric acid, multiple crystallizations are required to obtain high-purity vitamin C ethyl ether. This process is time-consuming and complex, resulting in a prolonged production cycle. Moreover, due to the multiple crystallization and purification steps, the overall product yield is typically only 50%-60%. This not only increases production costs but also limits the feasibility of large-scale industrial production. Summary of the Invention

[0005] 1. The problem to be solved

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an improved process for synthesizing vitamin C ethyl ether, thereby solving the following key problems:

[0007] Shortening reaction time: In existing processes, the reaction of vitamin C with acetone to produce the intermediate 5,6-O-isopropyl-L-ascorbic acid takes a long time, typically 3-5 hours. This invention aims to significantly reduce reaction time and improve production efficiency by optimizing the catalyst combination.

[0008] Improving purification efficiency and yield: Existing technologies require multiple crystallizations and complex purification steps to obtain high-purity vitamin C ethyl ether, resulting in low yields (typically 50%-60%). This invention improves the purification method, reduces the number of crystallization steps, and increases the purity and yield of the final product.

[0009] To achieve the above objectives, this invention introduces anhydrous copper sulfate and acetyl chloride as catalysts during the reaction of vitamin C with acetone, shortening the reaction time to 1-2 hours. In the deprotection step, hydrolysis is performed using a cationic resin, followed by extraction with a fat-soluble solvent. Only one crystallization is required to obtain vitamin C ethyl ether with a purity greater than 99%, and the overall yield can reach over 80%. Through these improvements, this invention not only increases the production efficiency of vitamin C ethyl ether but also reduces production costs, making it more suitable for large-scale industrial production.

[0010] 2. Technical Solution

[0011] To solve the above problems, the technical solution provided by the present invention is as follows:

[0012] A process for synthesizing vitamin C ethyl ether includes the following steps:

[0013] (1) Using L-ascorbic acid as raw material and acetone as reactant and solvent, heat to 38-40℃ and react for 1-2 hours under the action of anhydrous copper sulfate and acetyl chloride. Take the solid obtained after centrifugation, which is the vitamin C protective body.

[0014] (2) Add alkali, water and alkylating agent to the vitamin C protected body of the reaction product in step (1), and then add anhydrous ethanol. The weight of anhydrous ethanol is 5-8 times the weight of L-ascorbic acid added in step (1). Stir the reaction at 75-78℃ for 3 hours under nitrogen protection. Distill the reaction solution under reduced pressure to obtain vitamin C protected body ether.

[0015] (3) Dissolve the vitamin C protected ether, the reaction product of step (2), in a lower alcohol. Hydrolyze the solution in a column packed with cationic resin at 55-60°C for 5 hours. Add water to the hydrolysate and extract twice with a fat-soluble solvent. After recovering the solvent from the extract, recrystallize the obtained solid in ethyl acetate, collect the solid by centrifugation, and dry it under vacuum to obtain vitamin C ethyl ether.

[0016] Preferably, in step (1), the weight ratio of L-ascorbic acid to acetone is 1:1.5.

[0017] Preferably, in step (1), the amounts of anhydrous copper sulfate and acetyl chloride used are 3% and 1% of the weight of acetone, respectively.

[0018] Preferably, in step (1), the centrifugation speed is 5000 rpm and the centrifugation time is 10 min.

[0019] Preferably, the molar ratio of alkali to L-ascorbic acid in step (2) is 1:1 to 1.5:1;

[0020] In step (2), the molar ratio of water to L-ascorbic acid is 0.2:1 to 0.3:1;

[0021] In step (2), the molar ratio of the alkylating agent to L-ascorbic acid is 1:1 to 1.5:1.

[0022] Preferably, in step (2), the molar ratio of alkali to L-ascorbic acid is 1.2:1;

[0023] In step (2), the molar ratio of water to L-ascorbic acid is 0.3:1;

[0024] In step (2), the molar ratio of the alkylating agent to L-ascorbic acid is 1.2:1;

[0025] The weight of anhydrous ethanol in step (2) is 6 times the weight of L-ascorbic acid added in step (1).

[0026] Preferably, the base in step (2) is triethylamine;

[0027] In step (2), the alkylating agent is diethyl carbonate;

[0028] The parameters for vacuum distillation in step (2) are as follows:

[0029] Distillation temperature: 50℃, condensation temperature: 4℃, vacuum degree: 20mmHg.

[0030] Preferably, the lower alcohol in step (3) is isopropanol or ethanol;

[0031] In step (3), the cationic resin is either HYA-10 cationic resin from Xi'an Hanyu Resin Technology Co., Ltd. or LXT-142 cationic resin from Xi'an Lanxiao Technology New Material Co., Ltd.

[0032] It should be noted that this application also designs a new modified cationic resin. The LXT-142 type cationic resin is soaked in a 5% (w / w) NaOH solution for 2 hours, then rinsed with distilled water until neutral, and then soaked in a 5% (w / w) HCl solution for 3 hours, followed by rinsing with distilled water to remove impurities. Finally, it is soaked in a 15% (w / w) copper chloride solution at 50°C for 4 hours. Immediately after soaking, a 10% (w / w) sodium sulfonate solution is added at 60°C for 2 hours, followed by rinsing with distilled water until no residue remains.

[0033] In step (3), the lipid-soluble solvent is a mixture of petroleum ether and ethyl acetate, wherein the weight ratio of petroleum ether to ethyl acetate is 1:1-1:3;

[0034] The recrystallization conditions in step (3) are as follows: the amount of ethyl acetate is 5 times the weight of the solid, dissolved at 60-65℃, allowed to stand at 2-8℃ for 4-6 hours, cooling rate: 2℃ / min, and crystallization temperature is 4℃.

[0035] The vacuum drying conditions in step (3) are as follows: drying temperature is 58-62℃, and drying time is 5h.

[0036] Preferably, the vitamin C ethyl ether obtained in step (3) is subjected to high performance liquid chromatography for purity determination.

[0037] Preferably, the parameters for purity detection in step (3) are as follows:

[0038] The chromatographic column was a C18 column with an inner diameter of 4.6 mm and a length of 250 mm. The packing particle size was 5 μm. The column temperature was 35 °C, the detection wavelength was 242 nm, the flow rate was 0.7 mL / min, and the time was 25 min. The gradient elution mobile phase consisted of acetonitrile and 0.1% (w / w) aqueous phosphoric acid solution in a volume ratio ranging from 5:95 to 80:20.

[0039] This invention significantly improves the production efficiency and product quality of vitamin C ethyl ether through an innovative synthesis process. The invention utilizes a combination of anhydrous copper sulfate and acetyl chloride as a catalyst to accelerate the reaction between vitamin C and acetone. This combination not only shortens the reaction time to 1-2 hours (less than half that of conventional methods) but also improves the purity and yield of intermediates. This highly efficient catalyst combination reduces the formation of byproducts and optimizes reaction conditions, making the entire reaction process more economical and efficient. During the deprotection process, this invention introduces a cationic resin for hydrolysis, followed by extraction using a specific lipid-soluble solvent. This step not only simplifies the purification process but also significantly improves the purity (greater than 99%) and yield (up to 80% or more) of vitamin C ethyl ether. By reducing the number of crystallization steps, the production cycle is significantly shortened, reducing energy consumption and production costs. By shortening the reaction time and simplifying the purification steps, this invention effectively reduces raw material and energy consumption, significantly lowering production costs. This improvement makes the industrial production of vitamin C ethyl ether more economical, providing the market with an efficient, environmentally friendly, and economical solution.

[0040] 3. Beneficial effects

[0041] Compared with traditional methods, it has the following significant beneficial effects:

[0042] Significantly reduced reaction time: By using anhydrous copper sulfate and acetyl chloride as catalysts, the reaction time of vitamin C with acetone is shortened from 3-5 hours in traditional methods to 1-2 hours. This not only improves production efficiency but also reduces energy consumption and production costs. Increased product purity and yield: In the deprotection step, this invention uses cationic resin hydrolysis followed by extraction with a fat-soluble solvent, requiring only one crystallization to obtain vitamin C ethyl ether with a purity greater than 99%. The overall yield is increased to over 80%, significantly improving raw material utilization and economic benefits compared to the 50%-60% of traditional methods. Simplified process flow: The optimized process reduces the number of crystallization steps and complex purification procedures, making the production process simpler and more efficient. This improvement not only reduces operational complexity but also shortens the production cycle, facilitating large-scale industrial production. Reduced environmental impact: Due to the optimization of reaction and purification steps, this invention reduces the use of solvents and chemical reagents, thereby reducing waste generation and demonstrating better environmental friendliness.

[0043] In summary, this invention provides a more feasible solution for the large-scale application of vitamin C ethyl ether by improving reaction efficiency, product quality, and production economy. Attached Figure Description

[0044] Figure 1 is a flowchart of the synthesis process of vitamin C ethyl ether prepared in Example 1 of this invention.

[0045] Figure 2 is the original chromatographic analysis report of the vitamin C ethyl ether prepared in Example 2 of this invention.

[0046] Figure 3 is the original infrared analysis report of the vitamin C ethyl ether prepared in Example 2 of this invention.

[0047] Figure 4 is the original carbon spectrum analysis report of the vitamin C ethyl ether prepared in Example 2 of this invention.

[0048] Figure 5 is the original 1H NMR spectrum of the vitamin C ethyl ether prepared in Example 2 of this invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

[0050] It should be noted that in this invention, all weight parts or other weight ratios are in the international standard unit kilogram.

[0051] Example 1

[0052] As shown in Figure 1, the synthesis process of vitamin C ethyl ether includes the following steps:

[0053] (1) Weigh 352g L-ascorbic acid and 528g acetone, put them into a 10L reaction flask, turn on the stirrer, heat to 38℃, add 5.28g acetyl chloride and 15.84g anhydrous copper sulfate, react for 1h and then centrifuge to obtain vitamin C protectant.

[0054] (2) Add 202g of triethylamine, 7.2g of water and 236g of diethyl carbonate to the vitamin C protectant, then add 1760g of anhydrous ethanol. Under nitrogen protection, stir the reaction at 75°C for 3h, and distill under reduced pressure to obtain the vitamin C protectant ether.

[0055] (3) The vitamin C protective ether was dissolved in 352g of isopropanol and hydrolyzed at 55°C for 5h in a column packed with 17.6g of cationic resin (HYA-10 cationic resin from Xi'an Hanyu Resin Technology Co., Ltd.) to remove the protecting groups at positions 5 and 6. 352g of water was added and the mixture was extracted twice with 500g of petroleum ether:ethyl acetate (weight ratio 1:1). After recovering the solvent from the extract, the solid was crystallized once with ethyl acetate under the following conditions: dissolved at 60°C, allowed to stand at 8°C for 4h, collected by centrifugation, dried under vacuum at 62°C for 5h, and weighed to obtain 327.2g of solid. The purity of vitamin C ethyl ether was 99.5% and the yield of vitamin C ethyl ether was 80.2%.

[0056] Example 2

[0057] The synthesis process of vitamin C ethyl ether includes the following steps:

[0058] (1) Weigh 352g L-ascorbic acid and 528g acetone, put them into a 10L reaction flask, turn on the stirrer, heat to 39℃, add 5.28g acetyl chloride and 15.84g anhydrous copper sulfate, react for 2 hours and then centrifuge to obtain vitamin C protective body.

[0059] (2) Add 242.4g of triethylamine, 10.8g of water and 283.2g of diethyl carbonate to the vitamin C protectant, then add 2112g of anhydrous ethanol. Under nitrogen protection, stir and react at 77°C for 3h, and distill under reduced pressure to obtain the vitamin C protectant ether.

[0060] (3) The vitamin C protective ether was dissolved in 352g of ethanol and hydrolyzed at 60°C for 5h in a column packed with 35.2g of cationic resin (LXT-142 cationic resin from Xi'an Lanxiao Technology New Material Co., Ltd.) to remove the protecting groups at the 5 and 6 positions. Then, 352g of water was added and the mixture was extracted twice with 500g of petroleum ether:ethyl acetate (weight ratio 1:3). The solvent in the extract was removed, and the solid obtained was crystallized once with ethyl acetate under the following conditions: dissolved at 65°C, stood at 2°C for 6h, and vacuum dried at 58°C for 5h. The solid was weighed to obtain 338.3g. The purity of vitamin C ethyl ether was 99.6% and the yield of vitamin C ethyl ether was 82.9%.

[0061] Comparative Example 1

[0062] The synthesis process of vitamin C ethyl ether is basically the same as in Example 2, except that in step (1), anhydrous copper sulfate was not added, and only acetyl chloride was used as a catalyst. After a reaction time of 4 hours, 294.2 g of solid was obtained after drying. The purity of vitamin C ethyl ether was 99.0% and the yield of vitamin C ethyl ether was 72.1%.

[0063] The calculation formula is as follows: Vitamin C ethyl ether yield = (weight of pure vitamin C ethyl ether / theoretical amount of vitamin C ethyl ether produced) × 100%.

[0064] Table 1. Calculation of Vitamin C Ethyl Ether Yield

[0065] Table 1 shows the calculated yields of vitamin C ethyl ether in Examples 1, 2, and Comparative Example 1. Regarding purity, the products from the examples all had a purity above 99.5%, slightly higher than the comparative example. This indicates that the synthesis method of the present invention not only improves product yield but also enhances product purity. The present invention, for the first time, further optimizes the reaction conditions by combining anhydrous copper sulfate with acetyl chloride. This combination significantly shortens the reaction time, improves the purity and yield of the target product, and solves the problem of low product purity in traditional methods. The present invention achieves a more efficient synthesis route by optimizing the catalyst combination. This improvement not only increases production efficiency but also reduces production costs, making the industrial production of vitamin C ethyl ether more competitive. The short reaction time and high-purity product provide broader possibilities for subsequent applications, especially in fields with stringent product quality requirements, such as the pharmaceutical and cosmetic industries. Therefore, the innovation and practicality of the present invention in the synthesis of vitamin C ethyl ether have been verified, providing an efficient, economical, and environmentally friendly solution for the large-scale application of this compound.

[0066] Meanwhile, as shown in Figure 2, taking the vitamin C ethyl ether prepared in Example 2 as an example, the chromatographic peak information is interpreted as follows: The report shows that three main peaks were detected in the sample (peak 1, peak 2, and peak 3 from left to right in the figure), appearing at retention times of 7.107 min, 9.942 min, and 15.004 min, respectively. Peak 1 (7.107 min): Area percentage: 0.0842%, Area value: 13.59696 mAU*s. This may be an impurity or background noise. Peak 2 (9.942 min): Area percentage: 99.6613%, Area value: 16087.4 mAU*s. This peak occupies the majority of the total area and is the target product, vitamin C ethyl ether. Peak 3 (15.004 min): Area percentage: 0.2545%, Area value: 41.08047 mAU*s. This may be a byproduct or other impurities. Sample Purity: Based on the area percentage, the purity of the target product (peak 2) is 99.6613%, indicating extremely low impurity content in the sample. The sum of the remaining impurities (peaks 1 and 3) accounts for only 0.3387%, indicating high product purity. Retention Time Analysis: The retention time of peak 2 is 9.942 min, which is the characteristic retention time of the main target product. The stable and sharp main peak indicates good separation, and the chromatographic conditions are suitable for analyzing vitamin C ethyl ether. The total area is 16142.1 mAU*s, indicating a high sample concentration and strong detection signal. Conclusion: The target product vitamin C ethyl ether accounts for as high as 99.6613% in the sample, with very high purity, meeting the requirements for industrial production or laboratory research. The impurity content is extremely low, with only two small impurity peaks (7.107 min and 15.004 min), which do not significantly interfere with the main component. The chromatographic conditions are good, and the separation effect is clear, suitable for subsequent quantitative analysis or quality control.

[0067] As shown in Figure 3, infrared spectra are mainly used to analyze the functional group characteristics of molecular structures in samples. The following is a detailed interpretation of this infrared spectrum: wavenumber range and corresponding characteristic absorption peak: 3408.22 cm⁻¹ -1 (Broad peak): Corresponds to the stretching vibration of the hydroxyl group (-OH), indicating the possible presence of free hydroxyl groups or phenolic structures in the sample. 2929.87 cm⁻¹ -1 and 2877.79cm -1 The CH stretching vibration corresponding to alkyl (methyl and methylene) groups indicates the presence of saturated hydrocarbon chains in the sample. 1743.65 cm⁻¹ -1 The stretching vibration corresponding to the ester group (C=O) indicates the possible presence of ester compounds in the sample. This is an important characteristic peak of vitamin C ethyl ether, confirming the presence of the target product. 1425.50 cm⁻¹ -1 and 1382.96cm -1The presence of an alkyl structure was further confirmed by the CH bending vibration. (1271.08 cm) -1 and 1187.71cm -1 The stretching vibration corresponding to the ether bond (COC) indicates the presence of ether bonds in the sample. This is one of the important characteristics of vitamin C ethyl ether. 1056.82 cm⁻¹ -1 and 1031.92cm -1 The stretching vibration corresponding to the CO bond further supports the presence of ether and ester structures in the sample. Combined with the characteristic absorption peaks in the infrared spectrum, the following conclusion can be drawn: hydroxyl groups are present in the sample (3408.22 cm⁻¹). -1 This may be unreacted vitamin C residue. Ester group (1743.65cm) -1 ) and ether bonds (1271.08cm) -1 1187.71cm -1 The absorption peak of ) is clearly visible, indicating that the target product, vitamin C ethyl ether, has been successfully synthesized. The characteristic peak of the saturated hydrocarbon chain (2929.87 cm⁻¹) is also clearly visible. -1 2877.79cm -1 This further supports the presence of the alkyl moiety in the target product structure. The key absorption peaks in the infrared spectrum are consistent with the molecular structure of vitamin C ethyl ether, verifying the successful synthesis of the target product. The appearance of hydroxyl and other impurity peaks may be related to small amounts of unreacted starting materials or byproducts, but overall, it is consistent with the characteristics of a high-purity product.

[0068] As shown in Figure 4, carbon nanotube spectra are used to analyze the chemical environment of carbon atoms in compounds, helping to confirm molecular structure. The following is a detailed interpretation of this carbon nanotube spectrum: Chemical shift range: Chemical shift (δ) is in ppm, and the horizontal axis represents the chemical environment of different carbon atoms. The figure shows multiple clear peaks, indicating that the sample contains different types of carbon atoms. Main peak positions and corresponding structures:

[0069] Based on the chemical shift range and typical carbon signal characteristics, the following inferences are made:

[0070] 170-180 ppm: This region typically corresponds to the chemical shift of the carbonyl group (C=O).

[0071] The peak values ​​at 173.42 ppm and 177.86 ppm indicate the possible presence of ester or carboxylic acid groups in the sample, consistent with the structure of vitamin C ethyl ether.

[0072] 60-100ppm: This region typically corresponds to a chemical environment with ether bonds (CO) or saturated carbon bonded to oxygen.

[0073] The peak values ​​at 70.02 ppm and 72.04 ppm indicate the presence of ether bonds (COC) in the sample, which is an important characteristic of vitamin C ethyl ether.

[0074] 40-60ppm: This corresponds to a chemical environment where saturated carbon (such as methylene or methyl) is bonded to electronegative atoms (such as oxygen or nitrogen).

[0075] The peak values ​​at 63.59 ppm and 61.20 ppm are likely characteristic signals of the ethyl ether moiety.

[0076] 10-40 ppm: This region typically corresponds to a chemical environment with saturated alkyl carbon atoms. The peak at 14.60 ppm may be a signal from an ethyl-terminated methyl group.

[0077] The following conclusions can be drawn from the main peaks in the carbon spectrum:

[0078] The sample contains ester groups (C=O) and ether bonds (COC), consistent with the molecular structure of vitamin C ethyl ether. The saturated alkyl signal indicates the presence of an ethyl moiety. The clear peak distribution and absence of obvious impurity signals in the carbon spectrum indicate high sample purity. Analysis of the characteristic peaks in the carbon spectrum confirms the sample as vitamin C ethyl ether, verifying the presence of ester groups, ether bonds, and the ethyl moiety in its molecular structure. Furthermore, the spectrum shows high sample purity and low impurity content. This result is consistent with the findings of liquid chromatography and infrared spectroscopy.

[0079] As shown in Figure 5, a proton NMR spectrum is used to analyze the chemical environment of hydrogen atoms in a compound. The following is a detailed interpretation of this proton NMR spectrum:

[0080] Chemical shift range:

[0081] 0.5-5ppm.

[0082] Main peak positions and corresponding structures:

[0083] ~1.5 ppm: This may correspond to a methyl or methylene hydrogen atom in an alkyl chain. This is a common chemical shift in saturated hydrocarbon chains.

[0084] ~3.5-4.5 ppm: Corresponds to a methylene hydrogen atom bonded to oxygen. This indicates the presence of ether or ester bonds in the sample.

[0085] ~5 ppm: This may correspond to an enol structure or other special chemical environment bonded to oxygen. Peaks in this region may be key structural features in vitamin C ethyl ether.

[0086] Sample characteristic analysis:

[0087] Saturated hydrocarbon chains: The signal in the low field region (~1.5 ppm) indicates that the sample contains saturated hydrocarbon chains.

[0088] Oxygen-linked hydrogen: The signal in the mid-range region (~3.5-4.5 ppm) indicates the presence of an ether or ester structure in the sample.

[0089] High purity: The peaks in the spectrum are clear and there are no obvious impurity signals, indicating that the sample has high purity.

[0090] Analysis of the characteristic peaks in the above proton NMR spectrum confirms that the sample possesses the typical structural features of vitamin C ethyl ether. The hydrogen signals of the saturated hydrocarbon chain and oxygen linkage are consistent with the expected molecular structure, indicating successful synthesis and high purity.

[0091] Compared with the traditional three-step synthesis process of vitamin C ethyl ether, the present invention has the following significant advantages:

[0092] Shorter reaction time, improved purity and yield of target product: This invention shortens the reaction time of vitamin C with acetone to 1-2 hours by using anhydrous copper sulfate and acetyl chloride as a catalyst, less than half that of traditional methods. This optimization significantly improves reaction efficiency while reducing by-product formation, thereby greatly increasing the purity and yield of the target product. Simplified purification steps, improved production efficiency: In the third step of deprotection, this invention uses cationic resin for hydrolysis to remove the protecting groups at the 5 and 6 positions. Subsequently, the hydrolysate is extracted with a lipid-soluble solvent, and the solvent in the extract is recovered. Through this optimization, vitamin C ethyl ether with a purity greater than 99% can be obtained with only one crystallization, and the total yield can reach over 80%. Compared with the complex operation of multiple crystallizations required by traditional processes, this invention greatly simplifies the purification process and significantly shortens the production cycle. Reduced production costs: By shortening the reaction time, reducing purification steps, and increasing the yield, this invention effectively reduces raw material and energy consumption, significantly reducing production costs. This improvement makes the industrial production of vitamin C ethyl ether more economical. In summary, this invention outperforms traditional processes in terms of reaction efficiency, product quality, and production cost, providing an efficient, economical, and environmentally friendly solution for the large-scale industrial production of vitamin C ethyl ether.

[0093] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A process for synthesizing vitamin C ethyl ether, comprising the following steps: (1) Using L-ascorbic acid as raw material and acetone as reactant and solvent, heat to 38-40℃ and react for 1-2 hours under the action of anhydrous copper sulfate and acetyl chloride. Take the solid obtained after centrifugation, which is the vitamin C protective body. (2) Add alkali, water and alkylating agent to the vitamin C protected body of the reaction product in step (1), and then add anhydrous ethanol. The weight of anhydrous ethanol is 5-8 times the weight of L-ascorbic acid added in step (1). Stir the reaction at 75-78℃ for 3 hours under nitrogen protection. Distill the reaction solution under reduced pressure to obtain vitamin C protected body ether. (3) Dissolve the vitamin C protected ether, the reaction product of step (2), in a lower alcohol. Hydrolyze the solution in a column packed with cationic resin at 55-60°C for 5 hours. Add water to the hydrolysate and extract twice with a fat-soluble solvent. After recovering the solvent from the extract, recrystallize the obtained solid in ethyl acetate, collect the solid by centrifugation, and dry it under vacuum to obtain vitamin C ethyl ether.

2. The synthesis process of vitamin C ethyl ether according to claim 1, characterized in that: In step (1), the weight ratio of L-ascorbic acid to acetone is 1:1.

5.

3. The synthesis process of vitamin C ethyl ether according to claim 2, characterized in that: In step (1), the amounts of anhydrous copper sulfate and acetyl chloride used are 3% and 1% of the weight of acetone, respectively.

4. The synthesis process of vitamin C ethyl ether according to claim 3, characterized in that: In step (1), the centrifugation speed is 5000 rpm and the centrifugation time is 10 min.

5. The synthesis process of vitamin C ethyl ether according to claim 4, characterized in that: In step (2), the molar ratio of alkali to L-ascorbic acid is 1:1 to 1.5:1; In step (2), the molar ratio of water to L-ascorbic acid is 0.2:1 to 0.3:1; In step (2), the molar ratio of the alkylating agent to L-ascorbic acid is 1:1 to 1.5:

1.

6. The synthesis process of vitamin C ethyl ether according to claim 5, characterized in that: In step (2), the molar ratio of alkali to L-ascorbic acid is 1.2:1; In step (2), the molar ratio of water to L-ascorbic acid is 0.3:1; In step (2), the molar ratio of the alkylating agent to L-ascorbic acid is 1.2:1; The weight of anhydrous ethanol in step (2) is 6 times the weight of L-ascorbic acid added in step (1).

7. The synthesis process of vitamin C ethyl ether according to claim 6, characterized in that: In step (2), the alkali is triethylamine; In step (2), the alkylating agent is diethyl carbonate; The parameters for vacuum distillation in step (2) are as follows: Distillation temperature: 50℃, condensation temperature: 4℃, vacuum degree: 20mmHg.

8. The synthesis process of vitamin C ethyl ether according to claim 7, characterized in that: In step (3), the lower alcohol is isopropanol or ethanol; In step (3), the cationic resin is either HYA-10 cationic resin from Xi'an Hanyu Resin Technology Co., Ltd. or LXT-142 cationic resin from Xi'an Lanxiao Technology New Material Co., Ltd. In step (3), the lipid-soluble solvent is a mixture of petroleum ether and ethyl acetate, wherein the weight ratio of petroleum ether to ethyl acetate is 1:1-1:3; The recrystallization conditions in step (3) are as follows: the amount of ethyl acetate is 5 times the weight of the solid, dissolved at 60-65℃, allowed to stand at 2-8℃ for 4-6 hours, cooling rate: 2℃ / min, and crystallization temperature is 4℃. The vacuum drying conditions in step (3) are as follows: drying temperature is 58-62℃, and drying time is 5h.

9. The synthesis process of vitamin C ethyl ether according to claim 8, characterized in that: The purity of the vitamin C ethyl ether obtained in step (3) was determined by high performance liquid chromatography.

10. The synthesis process of vitamin C ethyl ether according to claim 9, characterized in that: The parameters for purity testing in step (3) are as follows: The chromatographic column was a C18 column with an inner diameter of 4.6 mm and a length of 250 mm. The packing particle size was 5 μm. The column temperature was 35 °C, the detection wavelength was 242 nm, the flow rate was 0.7 mL / min, and the time was 25 min. The gradient elution mobile phase consisted of acetonitrile and 0.1% (w / w) aqueous phosphoric acid solution in a volume ratio ranging from 5:95 to 80:20.

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