Synthesis process of vitamin C tetraisopalmitate

Abstract

The invention belongs to the field of organic synthesis, and particularly discloses a synthesis process of vitamin C tetraisopalmitate, which specifically comprises the following steps: firstly, adding an organic solvent A and an acylation reagent into 2-hexyldecanoic acid, and carrying out acylation reaction to obtain 2-hexyldecanoyl chloride; the preparation method comprises the following steps: dissolving L-ascorbic acid in an organic solvent B, adding tetrabutylammonium bromide, benzyltriethylammonium chloride, an acid-binding agent and 2-hexyldecanoyl chloride, carrying out an esterification reaction in an oxygen-free atmosphere, and purifying after the reaction to obtain the vitamin C tetraisopalmitate. Compared with the traditional synthesis process of the vitamin C tetraisopalmitate, the time for catalyzing the reaction of the L-ascorbic acid and the 2-hexyldecanoyl chloride to generate the vitamin C tetraisopalmitate is less than half of that of the traditional method, the purity of the target product is up to 93% or above, the conversion rate is higher, and the method is more suitable for being popularized to actual production.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to a synthesis process of vitamin C tetraisopalmitate. Background Technology

[0002] Vitamin C tetraisopalmitate is a very useful vitamin C derivative with the molecular formula C. 70 H 128 O 10 With a molecular weight of 1129.76, its structural formula is as follows: .

[0003] It is chemically very stable, a non-discoloring vitamin C derivative, and highly soluble in oil. Vitamin C tetraisopalmitate has excellent skin absorption properties, transforming into vitamin C during absorption to exert its functions. It possesses skincare benefits such as whitening, anti-oxidation, and anti-aging properties, making it a very important ingredient in cosmetics.

[0004] In the prior art, CN109320479B discloses a simple method for synthesizing vitamin C tetraisopalmitate. This invention uses 2-hexyldecaldehyde and L-ascorbic acid as raw materials, and azacarbene as a catalyst, to obtain vitamin C tetraisopalmitate in one step via an oxidative esterification reaction in the presence of an oxidant. However, this invention requires a reaction time of 36 hours at room temperature, with a yield of 82% and unknown purity.

[0005] Invention CN114230539B discloses a synthetic process for vitamin C tetraisopalmitate. Using 2-hexyldecaldehyde and L-ascorbic acid as raw materials, and modified niobic acid as a catalyst, an oxidative esterification reaction is carried out in combination with an oxide to obtain vitamin C tetraisopalmitate. The mixture is then extracted three times with water and ethyl acetate, the aqueous layer is removed, the organic layer is dried with anhydrous sodium sulfate, and purified by silica gel chromatography to obtain vitamin C tetraisopalmitate. However, the preparation of the modified niobic acid in this invention is cumbersome, time-consuming, has a yield of only 85%, and the purity is unknown.

[0006] Invention CN117362250B discloses a method for synthesizing vitamin C tetraisopalmitate using a nitrogen-doped activated carbon catalyst. The method involves thoroughly mixing ascorbic acid and DMF, adding the nitrogen-doped activated carbon catalyst and pyridine, and then adding 2-hexyldecanoyl chloride dropwise under an ice bath. After the addition is complete, the mixture is stirred overnight under an ice bath. Then, HCl solution is added, followed by repeated extraction with n-hexane. The extract is washed with saturated calcium carbonate solution, dried over anhydrous sodium sulfate, and the resulting n-hexane solution is eluted by silica gel column chromatography. The eluent is collected, concentrated, and the n-hexane is recovered to obtain crude vitamin C tetraisopalmitate. The crude product is then subjected to activated carbon adsorption treatment, filtered, and residual n-hexane is removed using an oil pump. Finally, it is purified by two-stage molecular distillation to obtain pure vitamin C tetraisopalmitate. However, the nitrogen-doped activated carbon catalyst in this invention is a NiCo bimetallic supported nitrogen-doped carbon nanotube, requiring a temperature of 800℃ and holding for 2-2.5 hours during preparation, which is quite demanding.

[0007] Invention CN105218494A discloses an L-ascorbic acid diester and its preparation method. In this invention, vitamin C is mixed with ethyl acetate, pyridine is added, followed by a phase transfer catalyst. Then, fatty acyl chloride is added dropwise to the reaction system, maintaining the dropping rate. After the addition of the fatty acyl chloride is complete, the reaction continues. The aqueous layer is separated, the oil layer is washed with water, and ethyl acetate is evaporated to obtain a colorless, oily crude vitamin C diester. Purification yields the vitamin C fatty acid diester. However, this invention can only be used to prepare vitamin C fatty acid diester; whether it can prepare vitamin C tetraisopalmitate is questionable.

[0008] In summary, existing similar preparation processes for vitamin C tetraisopalmitate have problems such as long reaction time, complicated preparation of the required catalyst, limited yield, and high cost, and still need further optimization and improvement. Summary of the Invention

[0009] The purpose of this invention is to overcome at least one deficiency of the prior art and provide a synthesis process for vitamin C tetraisopalmitate.

[0010] The technical solution adopted in this invention is: This invention provides a process for synthesizing vitamin C tetraisopalmitate, the process comprising the following steps: Step (1): Add organic solvent A and acylation reagent to 2-hexyldecanoic acid to carry out acylation reaction to obtain 2-hexyldecanoic acid chloride; Step (2): L-ascorbic acid is dissolved in organic solvent B, and then tetrabutylammonium bromide, benzyltriethylammonium chloride, acid binder, and 2-hexyldecanoyl chloride obtained in step (1) are added. Esterification reaction is carried out in an anaerobic atmosphere to obtain crude vitamin C tetraisopalmitate. Step (3): Purify the crude vitamin C tetraisopalmitate obtained in step (2) to obtain the vitamin C tetraisopalmitate.

[0011] Specifically, the acylation reaction in step (1) satisfies at least one of the following conditions: The acylation reagent is selected from either thionyl chloride or oxalyl chloride; The reaction temperature is 10–50°C; The reaction time is 1 to 2 hours; The mass ratio of 2-hexyldecanoic acid to the acylation reagent is 1:1.5 to 1:2.0.

[0012] The organic solvent A is NMP, toluene, DMF, DCM, or methyltetrahydrofuran; The volume of organic solvent A is 4.9 to 5.1 times that of 2-hexyldecanoic acid.

[0013] Since acylation is a reversible reaction, excess acylation reagent can shift the reaction equilibrium toward the formation of the acylated product, reduce raw material residue, and ensure complete reaction of 2-hexyldecanoic acid.

[0014] Specifically, the esterification reaction in step (2) satisfies at least one of the following conditions: The reaction temperature is 0–10°C; The reaction time is 1 to 2 hours; The mass ratio of L-ascorbic acid to tetrabutylammonium bromide is 1:1.5 to 1:2.0; The mass ratio of L-ascorbic acid to benzyltriethylammonium chloride is 1:0.01 to 1:0.02.

[0015] The mass ratio of L-ascorbic acid to the acid-binding agent is 1:4.5-1:8; The mass ratio of L-ascorbic acid to 2-hexyldecanoyl chloride is 1:4.5-1:8; The acid-binding agent is selected from any one of pyridine, triethylamine, potassium carbonate, sodium hydroxide, and potassium hydroxide; The organic solvent B is NMP, toluene, DMF, DCM, or methyltetrahydrofuran.

[0016] Literature reports that the phase transfer catalyst tetrabutylammonium bromide has a wide range of applications. This invention unexpectedly discovered that by adding tetrabutylammonium bromide, benzyltriethylammonium chloride, and an acid-binding agent to the reaction system, the time required to catalyze the reaction of L-ascorbic acid and 2-hexyldecanoyl chloride to produce vitamin C tetraisopalmitate is less than half that of conventional methods, and the purity of the target product, vitamin C tetraisopalmitate, reaches over 93%, demonstrating a high conversion rate.

[0017] In the esterification reaction, tetrabutylammonium bromide (TBAB) serves as the main phase transfer catalyst. Its cationic radius is large and its lipophilicity is strong, which can effectively promote the transfer of ions in the reaction system and improve the overall reaction rate.

[0018] Benzyltriethylammonium chloride (TEBA) can be used as an auxiliary catalyst in conjunction with TBAB to further improve catalytic efficiency, especially to promote the esterification reaction of the less active hydroxyl groups in L-ascorbic acid molecules, thereby effectively increasing the proportion of tetraesterification products.

[0019] Hydrogen chloride is generated during the esterification reaction. The accumulation of HCl will inhibit the reaction from proceeding in the forward direction and may even cause L-ascorbic acid to decompose. Therefore, an acid-binding agent needs to be added to neutralize the generated HCl, maintain the alkaline environment of the reaction system, and promote the forward shift of the reaction equilibrium.

[0020] Furthermore, this esterification reaction is exothermic, and L-ascorbic acid is easily oxidized at high temperatures; therefore, a relatively low reaction temperature is necessary. Maintaining the temperature within the range of 0–10°C can slow down the exothermic reaction rate, prevent a sudden rise in the reaction system temperature, and effectively suppress the oxidation side reactions of L-ascorbic acid, thereby improving the purity of the target product. If the temperature exceeds 10°C, the oxidation side reactions intensify, and the amount of incomplete esterification products increases.

[0021] Optionally, the purification operation in step (3) is as follows: add a lower alcohol to dissolve the crude vitamin C tetraisopalmitate, then slowly add 5% to 20% of the mass of the lower alcohol in ice water, stir thoroughly and the product precipitates and separates from the lower alcohol, discard the lower alcohol phase, repeat the above operation three times, and finally distill to obtain pure vitamin C tetraisopalmitate.

[0022] In some embodiments, the lower alcohol is selected from isopropanol, tert-butanol, or ethanol.

[0023] Optionally, the purification operation in step (3) is: to purify and separate crude vitamin C tetraisopalmitate by high-speed countercurrent chromatography.

[0024] In some embodiments, the solvent system is dichloromethane / methanol / n-hexane = 4:1:2 or dichloromethane / isopropanol / n-hexane = 4:1.5:2. The solvent is prepared in proportion, allowed to stand and separate into layers, and then ultrasonically degassed for 20 minutes. After being placed at room temperature, the upper phase is used as the stationary phase and the lower phase is used as the mobile phase.

[0025] In some embodiments, the high-speed countercurrent chromatography purification operation steps are as follows: 1. Pump stationary phase: Pump the stationary phase at a flow rate of 30-50 ml / min. Stop the pump after about 20-50 ml of stationary phase flows out of the detector outlet. 2. System equilibration: Turn on the UV detector to start preheating. Rotate the main unit clockwise to 800-900 rpm, and simultaneously pump the mobile phase at a flow rate of 10-20 ml / min until the mobile phase flows out of the outlet and the UV signal is stable, indicating that the system is basically equilibrated. 3. Sample injection: Dissolve a certain amount of sample in the upper and lower phases of the system, sonicate to dissolve evenly, switch the injection six-way valve to load, pour the sample solution into the sample syringe, push out air bubbles, and aspirate until all the sample enters the injection ring. Switch the load to inject, zero the detector and workstation, and start recording. 4. Receive fraction: Record the fractions received on the workstation. The equipment running time is 1000 min. Save the data and collect it. 5. Equipment cleaning: Disconnect the pump from the main unit, connect the main unit inlet to the gas tube outlet, and purge with air.

[0026] The beneficial effects of this invention are: 1. Tetrabutylammonium bromide, benzyltriethylammonium chloride, and an acid-binding agent were used together as a catalyst for the reaction of L-ascorbic acid with 2-hexyldecanoyl chloride to produce vitamin C tetraisopalmitate. This shortened the reaction time, improved the conversion rate, and achieved a purity of over 93% for vitamin C tetraisopalmitate.

[0027] 2. The crude product after concentration of the reaction solution in the second step is washed three times with a lower alcohol, and the solvent is removed by vacuum evaporation to obtain vitamin C tetraisopalmitate with a purity greater than 98%. The total yield of vitamin C tetraisopalmitate can reach more than 85%, which greatly reduces the production cost compared with silica gel chromatography purification. Alternatively, high-speed countercurrent chromatography can be used for purification, which only requires one separation to obtain vitamin C tetraisopalmitate with a purity of 99.9%. The total yield of vitamin C tetraisopalmitate can reach more than 90%, which can be recycled and reused, making it more green and environmentally friendly, and reducing production costs. Attached Figure Description

[0028] Figure 1 The liquid chromatogram is of the product prepared in Example 1-1.

[0029] Figure 2 The liquid chromatograms are of the crude products prepared in Examples 1-2.

[0030] Figure 3 The liquid chromatogram is shown for the product prepared in Comparative Example 1-1.

[0031] Figure 4 The liquid chromatograms are of the products prepared in Comparative Examples 1-2.

[0032] Figure 5 The liquid chromatograms are of the products prepared in Comparative Examples 1-3.

[0033] Figure 6 The product prepared in Example 2-1 1 H NMR spectrum.

[0034] Figure 7 The product prepared in Example 2-1 13 C NMR spectrum.

[0035] Figure 8 The IR spectrum of the product prepared in Example 2-1.

[0036] Figure 9 This is a liquid chromatogram of pure vitamin C tetraisopalmitate.

[0037] Figure 10 The liquid chromatogram is of the product prepared in Example 2-1.

[0038] Figure 11 The liquid chromatograms are of the products prepared in Examples 2-3.

[0039] Figure 12 The liquid chromatogram is shown for the product prepared in Comparative Example 2-2. Detailed Implementation

[0040] The following disclosure provides many different embodiments or examples for implementing various aspects of the invention. Unless otherwise indicated, all solvents and reagents used in the following examples and comparative examples are commercially available and used as is.

[0041] To address the problems of long reaction time, cumbersome catalyst preparation, limited yield, and high cost in existing technologies, the present invention provides the following synthetic route for vitamin C tetraisopalmitate: Specifically, the following steps are included: 1. Add 2-hexyldecanoic acid to a solvent, then add an acylation reagent, control the temperature at 10-50℃, stir, cool and concentrate to obtain 2-hexyldecanoic acid chloride; 2. Dissolve L-ascorbic acid in a solvent, then add tetrabutylammonium bromide, benzyltriethylammonium chloride and an acid-binding agent. Add 2-hexyldecanoyl chloride dropwise under ice bath, and then stir the reaction at 0-10℃. 3. Concentrate the reaction solution from step 2 to obtain the crude product, dissolve it in a lower alcohol, and then slowly add 5% to 20% ice water (based on the amount of the lower alcohol). After thorough stirring, the product precipitates and separates from the lower alcohol. 2-Hexyldecanoic acid and impurities remain in the lower alcohol. Discard the lower alcohol phase, remove excess 2-hexyldecanoic acid and impurities, repeat the washing process three times, and evaporate the solvent under reduced pressure to obtain vitamin C tetraisopalmitate with a purity greater than 98%; or purify and separate it using high-speed countercurrent chromatography.

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0043] In the embodiments and comparative examples of this invention, the yield is calculated using the following formula: Vitamin C tetraisopalmitate yield = (weight of pure vitamin C tetraisopalmitate / theoretical amount of vitamin C tetraisopalmitate produced) × 100%.

[0044] Example 1-1 A process for synthesizing vitamin C tetraisopalmitate includes the following steps: 1. Add 6.55 g of 2-hexyldecanoic acid to a three-necked flask, dissolve it in 30 mL of dichloromethane, and then add 9.83 g of oxaloyl chloride dropwise. Maintain the reaction at 10 °C for 1 hour, then evaporate the dichloromethane under reduced pressure to obtain 2-hexyldecanoic acid chloride. 2. Add 0.56g L-ascorbic acid to a three-necked flask, dissolve it in 5mL DMF, add 0.84g tetrabutylammonium bromide and 0.01g benzyltriethylammonium chloride, add 2.8g triethylamine, cool to below 5℃ and stir, add 2-hexyldecanoyl chloride dropwise to the three-necked flask, control the temperature at ≤10℃, keep the reaction at this temperature for 1 hour, evaporate the DMF under reduced pressure to obtain the crude oily liquid product.

[0045] like Figure 1 As shown, the purity of vitamin C tetraisopalmitate was 93.8% according to analysis.

[0046] Examples 1-2 A synthesis process for vitamin C tetraisopalmitate differs from Example 1 in that the acylation reagent oxaloyl chloride is used in step 1. This example uses thionyl chloride as the acylation reagent, and specifically includes the following steps: 1. Add 6.55 g of 2-hexyldecanoic acid to a three-necked flask, dissolve it in 30 mL of dichloromethane, and add 11.79 g of thionyl chloride dropwise. Maintain the reaction at 10 °C for 1.5 hours, then evaporate the dichloromethane under reduced pressure to obtain 2-hexyldecanoyl chloride; 2. Add 0.56g L-ascorbic acid to a three-necked flask, dissolve it in 5mL dichloromethane, add 1.12g tetrabutylammonium bromide and 0.01g benzyltriethylammonium chloride, add 2.8g pyridine, cool to below 5℃ and stir. Add 2-hexyldecanoyl chloride dropwise to the three-necked flask, control the temperature at ≤10℃, keep the reaction at this temperature for 1.5 hours, and evaporate the dichloromethane under reduced pressure to obtain an oily crude product.

[0047] like Figure 2 As shown, the purity of vitamin C tetraisopalmitate was 93.1% according to analysis.

[0048] Comparative Example 1-1 A synthesis process for vitamin C tetraisopalmitate is basically the same as in Examples 1-1, except that benzyltriethylammonium chloride is not added in step 2, and the reaction time is extended to 5 hours compared to 1.5 hours in Example 1.

[0049] like Figure 3 As shown, the peak heights of the two small impurity peaks before the elution time of the crude product peak, as determined by high performance liquid chromatography (HPLC), significantly increased, suggesting that they were unsaturated substitution products of vitamin C isopalmitoate. NMR confirmed that the impurity peaks indicated that one or both of the 2,3-hydroxyl groups of vitamin C failed to be substituted with 2-hexyldecanoyl chloride, indicating incomplete reaction of the raw vitamin C. This resulted in a final product purity of only 48.1%, failing to meet the requirements.

[0050] Comparative Examples 1-2 A synthesis process for vitamin C tetraisopalmitate is basically the same as in Examples 1-1, except that tetrabutylammonium bromide is not added in step 2, and the reaction time is extended to 5 hours compared to 1.5 hours in Example 1.

[0051] like Figure 4 As shown, the purity of the crude product was 83.8% according to high performance liquid chromatography, suggesting the presence of a large number of unsaturated substituted products of vitamin C isopalmitoate, which failed to meet the requirements.

[0052] Comparative Examples 1-3 A synthesis process for vitamin C tetraisopalmitate is basically the same as in Examples 1-1, except that in step 2, benzyltriethylammonium chloride is replaced with benzyltrimethylammonium chloride.

[0053] like Figure 5 As shown, the purity of the crude product was 66.3% according to high performance liquid chromatography, suggesting the presence of a large number of unsaturated substituted products of vitamin C isopalmitoate, which failed to meet the requirements.

[0054] Example 2-1 This example involves the purification of vitamin C tetraisopalmitate, and the specific procedures are as follows: The crude product obtained in Example 1-1 was dissolved in 30 mL of isopropanol, and ice water of 5% to 20% of the isopropanol amount was slowly added dropwise. After stirring thoroughly, the product precipitated and separated into layers. The isopropanol phase was discarded, and the product was washed three times. After removing the residual solvent under reduced pressure, 3.08 g of colorless and odorless vitamin C tetraisopalmitate product was obtained.

[0055] After testing, such as Figure 6 As shown, the product's 1¹H NMR (400MHz, CDCI3) data are as follows: δ (ppm) 5.51 (s, 1H, C4-H), 5.42 (m, 1H, C5-H), 4.50–4.40 (m, 1H, C6-H), 4.30–4.20 (m, 1H, C6-H), 2.55–2.40 (m, 2H), 2.35–2.20 (m, 2H), 1.85–1.10 (m, 86H), 1.00–1.75 (m, 24H).

[0056] like Figure 7 As shown, the product's 13 The C10 NMR spectra (100 MHz, CDCl3) data are as follows: δ (ppm) 175.8, 174.5, 171.4, 170.1, 164.9, 150.9, 122.3, 75.0, 66.0, 61.6, 45-45.9 (4C), 25-32.2 (40C), 14.1-22 (16C).

[0057] like Figure 8 As shown, the IR chromatogram data of this product are: 2954.95, 2926.01, 2856.58, 1799.59, 1780.30, 1743.65, 1708.93, 1465.90, 1377.17, 1338.60, 1201.65, 1134.14, 1099.43, 956.69, 891.11, 748.38, 723.31 cm⁻¹ - ¹.

[0058] like Figure 9 and Figure 10 As shown, the purity of vitamin C tetraisopalmitate was greater than 98% and the yield of vitamin C tetraisopalmitate was 85.8%.

[0059] Example 2-2 This example involves the purification of vitamin C tetraisopalmitate, and the specific procedures are as follows: The crude products obtained in Examples 1-2 were purified by high-speed countercurrent chromatography using a Shanghai Tongtian Biochemical TBE300C. The solvent system was dichloromethane / methanol / n-hexane 4:1:2. The solvent was prepared according to the ratio, and after standing and separating into layers, the products were degassed by sonication for 20 min. After being placed at room temperature, the upper phase was used as the stationary phase and the lower phase was used as the mobile phase.

[0060] The steps for chromatographic purification are as follows: 1. Pumping stationary phase: Pump the stationary phase at a flow rate of 40 ml / min. Stop pumping after about 30 ml of stationary phase flows out of the detector outlet.

[0061] 2. System equilibrium: Turn on the UV detector to start preheating, rotate the main unit to 900 rpm, and simultaneously pump in the mobile phase at a flow rate of 20 ml / min until the mobile phase flows out of the outlet and the UV signal is stable, indicating that the system is basically in equilibrium.

[0062] 3. Sample injection: Dissolve a certain amount of sample in the upper and lower phases of the system, sonicate to dissolve evenly, switch the six-way injection valve to load, pour the sample solution into the sample injector, push out air bubbles and aspirate until the sample is completely in the injection ring, switch load to inject, zero the detector and workstation and start recording.

[0063] 4. Receive stream: The workstation records the device running time as 1000 minutes, saves the data, and then saves it.

[0064] 5. Equipment Cleaning: Disconnect the pump from the main unit, connect the main unit inlet to the air pipe outlet, and blow air. After removing the target component solvent by vacuum distillation, 3.24g of colorless and odorless vitamin C tetraisopalmitate is obtained.

[0065] Analysis showed that the purity of vitamin C tetraisopalmitate reached 99.9%, and the yield of vitamin C tetraisopalmitate was 90.2%.

[0066] Example 2-3 This example involves the purification of vitamin C tetraisopalmitate, and the specific procedures are as follows: The crude products obtained in Examples 1-2 were purified by high-speed countercurrent chromatography using a Shanghai Tongtian Biochemical TBE300C. The solvent system was dichloromethane / isopropanol / n-hexane = 4:1.5:2. After the solvent was prepared according to the ratio, the mixture was allowed to stand for layering, and then ultrasonically degassed for 20 min. After being placed at room temperature, the upper phase was used as the stationary phase and the lower phase was used as the mobile phase. The specific chromatographic purification operation was the same as in Examples 2-2, and 3.17 g of colorless and odorless vitamin C tetraisopalmitate was finally obtained.

[0067] like Figure 11 As shown, the purity of vitamin C tetraisopalmitate reached 99.3% and the yield of vitamin C tetraisopalmitate was 88.2%.

[0068] Comparative Example 2-1 A process for synthesizing vitamin C tetraisopalmitate, the crude product of which is derived from Example 1-1, the difference being that: in step 3, the product is washed three times with ethanol, while the rest is the same as in Example 2-1.

[0069] After removing the residual solvent by vacuum distillation, 2.94g of colorless and odorless vitamin C tetraisopalmitate was obtained. Analysis showed that the purity of vitamin C tetraisopalmitate was greater than 98%, and the yield of vitamin C tetraisopalmitate was 81.8%.

[0070] Comparative Example 2-2 A process for synthesizing vitamin C tetraisopalmitate, the crude product is derived from Example 1-1, the difference being: in step 3, the crude product is separated by silica gel column chromatography (solvent ratio is petroleum ether: ethyl acetate = 30: 1), the rest is the same as in Example 2-1.

[0071] like Figure 12 As shown, 2.58g of vitamin C tetraisopalmitate was finally obtained. The purity of vitamin C tetraisopalmitate was 95.3% and the yield of vitamin C tetraisopalmitate was 71.9%.

[0072] The above is a further detailed description of the present invention and should not be considered as a limitation on the specific implementation of the present invention. For those skilled in the art, simple deductions or substitutions without departing from the concept of the present invention are all within the protection scope of the present invention.

Claims

1. A process for synthesizing vitamin C tetraisopalmitate, characterized in that, The synthesis process includes the following steps: Step (1): Add organic solvent A and acylation reagent to 2-hexyldecanoic acid to carry out acylation reaction to obtain 2-hexyldecanoic acid chloride; Step (2): L-ascorbic acid is dissolved in organic solvent B, and then tetrabutylammonium bromide, benzyltriethylammonium chloride, acid binder, and 2-hexyldecanoyl chloride obtained in step (1) are added. Esterification reaction is carried out in an anaerobic atmosphere to obtain crude vitamin C tetraisopalmitate. Step (3): Purify the crude vitamin C tetraisopalmitate obtained in step (2) to obtain the vitamin C tetraisopalmitate.

2. The synthesis process according to claim 1, characterized in that, The esterification reaction in step (2) satisfies at least one of the following conditions: The reaction temperature is 0–10°C; The reaction time is 1 to 2 hours; The mass ratio of L-ascorbic acid to tetrabutylammonium bromide is 1:1.5 to 1:2.0; The mass ratio of L-ascorbic acid to benzyltriethylammonium chloride is 1:0.01 to 1:0.

02.

3. The synthesis process according to claim 1, characterized in that, The acylation reaction in step (1) satisfies at least one of the following conditions: The reaction temperature is 10–50°C; The reaction time is 1 to 2 hours; The mass ratio of 2-hexyldecanoic acid to the acylation reagent is 1:1.5 to 1:2.

0.

4. The synthesis process according to claim 1, characterized in that, In step (2), the mass ratio of L-ascorbic acid to the acid-binding agent is 1:4.5-1:

8.

5. The synthesis process according to claim 1, characterized in that, In step (2), the mass ratio of L-ascorbic acid to 2-hexyldecanoyl chloride is 1:4.5-1:

8.

6. The synthesis process according to claim 1 or 3, characterized in that, The acylation reagent is selected from either thionyl chloride or oxalyl chloride.

7. The synthesis process according to claim 1, characterized in that, The acid-binding agent is selected from any one of pyridine, triethylamine, potassium carbonate, sodium hydroxide, and potassium hydroxide.

8. The synthesis process according to claim 1, characterized in that, The purification operation in step (3) is as follows: add a lower alcohol to dissolve the crude vitamin C tetraisopalmitate, then slowly add 5% to 20% of the mass of the lower alcohol in ice water. After stirring thoroughly, the product precipitates and separates from the lower alcohol. Discard the lower alcohol phase. Repeat the above operation three times. Finally, distill to obtain pure vitamin C tetraisopalmitate.

9. The synthesis process according to claim 8, characterized in that, The lower alcohol is selected from isopropanol, tert-butanol, or ethanol.

10. The synthesis process according to claim 1, characterized in that, The purification operation in step (3) is as follows: the crude vitamin C tetraisopalmitate is purified and separated by high-speed countercurrent chromatography.

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