Directional preparation method of epigallocatechin palmitate based on hydroxylamine deprotection
The hydroxylamine deprotection method simplifies the catechin esterification reaction, solving the problems of complex catechin esterification reaction system and high purification difficulty, and achieving the preparation of target products with high purity and high yield, which is suitable for industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-03-31
AI Technical Summary
The existing catechin esterification reaction system is complex, produces many byproducts, and is difficult to purify, resulting in low product recovery rate and making it difficult to adapt to large-scale production. In addition, the use of highly toxic deprotecting agents leads to side reactions and low yield.
The method employs hydroxylamine deprotection, which involves protecting the ortho-phenolic hydroxyl group through acylation, directional esterification of the fatty alcohol hydroxyl group, removal of excess acyl chloride with ethanol, and washing with petroleum ether to remove impurities, thus avoiding chromatographic purification steps and directly obtaining the high-purity target product.
It improves reaction selectivity and product purity, simplifies the operation process, reduces solvent and filler consumption, and improves yield and safety, making it suitable for industrial production.
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Abstract
Description
Technical Field
[0001] This invention belongs to the technical fields of food, daily chemical, and pharmaceutical, and specifically relates to a method for the directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection. Background Technology
[0002] Catechins, as a class of natural active substances derived from tea, can effectively enhance the lipophilicity and in vivo absorption and utilization of their derivatives through palmitate modification, thus possessing broad development potential in functional foods, skincare products, and pharmaceutical formulations. Currently, the preparation of these esterified products mainly relies on chemical synthesis routes. However, since catechin molecules contain multiple phenolic and alcoholic hydroxyl groups with similar reactivity, direct esterification reactions easily form various positionally isomeric byproducts, leading to complex reaction systems and difficulties in separating and purifying the target product. Therefore, conventional techniques in this field often employ a stepwise selective protection strategy, i.e., first protecting the ortho-phenolic hydroxyl group, then specifically esterifying the fatty alcoholic hydroxyl group, and finally removing the protecting group. However, this synthetic strategy still faces shortcomings in practical applications: for example, the deprotection stage usually requires reagents such as hydrazine hydrate, subsequent processing steps are cumbersome, and the purification of the final product depends on chromatographic purification (column chromatography). Column chromatography is not only time-consuming and consumes a large amount of packing material and solvent, leading to a decrease in product recovery rate, but it is also difficult to meet the needs of large-scale production, thus seriously limiting the efficient and economical preparation and industrialization of such compounds.
[0003] To address the aforementioned issues, existing patent (CN104292201A) discloses a method for preparing 3-esterified catechins via anhydride acylation protection, alkane acyl chloride esterification, and hydrazine deprotection. While this method achieves the synthesis of the target product, it still requires chromatographic purification after deprotection to obtain a product of acceptable purity. Furthermore, the deprotecting agent, hydrazine, is highly basic and nucleophilic, easily leading to side reactions such as ester bond cleavage in the main product during acyl removal, causing decomposition of the target product and resulting in a low yield (70-75%). The aforementioned chromatographic purification steps and low yield together make the entire process cumbersome and generate a large amount of organic solvent waste, failing to meet the requirements of green chemistry and industrial production. Therefore, developing a new process for preparing catechin esterification products that improves reaction selectivity and simplifies post-processing (eliminating the need for chromatographic purification) has significant technological value and application demand. Summary of the Invention
[0004] To address the problems existing in the prior art, this invention provides a method for the directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection. This method has the advantages of simple operation, simple post-processing (no need for column chromatography purification), and high product purity.
[0005] A method for the directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection includes the following steps:
[0006] (1) Epigallocatechin was dissolved in a solvent, and then propionic anhydride and a base catalyst were added to acylate the ortho-phenolic hydroxyl group for protection. After the reaction was complete, the protected product was obtained.
[0007] (2) Dissolve the obtained protected product in the reaction solvent, add palmitoyl chloride and pyridine, and esterify the hydroxyl groups of the fatty alcohol;
[0008] (3) After the esterification reaction is completed, ethanol is added to the system and the reaction is carried out at room temperature to remove excess palmitoyl chloride;
[0009] (4) After the reaction in step (3) is completed, hydroxylamine aqueous solution is added to the system to remove the propionyl protecting group, and the epigallocatechin palmitate is obtained by post-treatment.
[0010] In step (1) above,
[0011] Preferably, the molar ratio of epigallocatechin (EGC) to propionic anhydride is 1:(2~30). More preferably, it is 1:(5~10). This ratio helps to achieve sufficient acylation of the ortho-phenolic hydroxyl groups.
[0012] Preferably, the molar volume ratio of EGC to solvent is 0.05~0.2 mol / L. More preferably, it is 0.08~0.12 mol / L.
[0013] Preferably, the solvent is anhydrous acetonitrile.
[0014] Preferably, the base catalyst is one of triethylamine, N,N-diisopropylethylamine, or pyridine. More preferably, it is triethylamine.
[0015] Preferably, the molar ratio of epigallocatechin (EGC) to the alkaline catalyst is 1:(2~30). More preferably, it is 1:(5~10), which can fully neutralize the byproduct propionic acid and at the same time fully activate the phenolic hydroxyl groups of EGC to increase the reaction rate.
[0016] Preferably, the acylation reaction is carried out at room temperature for 2 to 6 hours. More preferably, it is carried out for 4 hours.
[0017] As a preferred method, after the reaction is completed, the reaction mixture is extracted with ethyl acetate, washed twice with deionized water, dehydrated and dried with anhydrous magnesium sulfate, filtered, and then the ethyl acetate is removed by rotary evaporation to obtain the EGC protected product.
[0018] In step (2) above,
[0019] Preferably, the molar ratio of the protected product to palmitoyl chloride is 1:(1~10). More preferably, it is 1:(2~4), which helps to achieve full esterification of the fatty alcohol hydroxyl groups.
[0020] Preferably, the molar ratio of the protected product to pyridine is 1:(1~10). More preferably, it is 1:(1~4), which can greatly improve the efficiency of the esterification reaction.
[0021] Preferably, the reaction solvent is anhydrous dichloromethane.
[0022] Preferably, the molar volume ratio of the protected product to the reaction solvent is 0.05~0.2 mol / L. More preferably, it is 0.08~0.12 mol / L.
[0023] Preferably, the esterification reaction is carried out at room temperature for 0.5 to 2 hours. More preferably, it is carried out for 0.5 hours.
[0024] Pyridine and palmitoyl chloride were added dropwise to the solution protecting the product.
[0025] In step (3) above,
[0026] Preferably, the volume ratio of the added ethanol to the reaction solvent in step (2) is 1:(0.5~2). More preferably, it is 1:1.
[0027] Preferably, the concentration of ethanol is 95% (v / v).
[0028] Preferably, the reaction time for removing palmitoyl chloride is 1 to 4 hours. More preferably, it is 2 hours, which is sufficient to completely remove excess palmitoyl chloride.
[0029] In step (4) above,
[0030] The concentration of hydroxylamine aqueous solution is 50 wt.%.
[0031] Preferably, the molar ratio of epigallocatechin to hydroxylamine is 1:(10~20). More preferably, it is 1:(10~15), which can greatly improve the removal efficiency of the propionyl protecting group.
[0032] Preferably, the deprotection reaction is carried out at room temperature for 1 to 4 hours. More preferably, it is carried out for 2 hours.
[0033] As a preferred option, the following post-treatment is performed after the deprotection reaction is completed:
[0034] After extraction with ethyl acetate, the reaction solution was washed twice each with 1 mol / L hydrochloric acid solution and deionized water, and then dehydrated and dried with anhydrous magnesium sulfate. The organic phase was then collected by filtration and rotary evaporation. The resulting solid was washed with petroleum ether, filtered, and dried to obtain epigallocatechin palmitate.
[0035] The EGC palmitate obtained by the preparation method of the present invention has the following structural formula:
[0036]
[0037] As a preferred embodiment, a method for preparing epigallocatechin palmitate based on hydroxylamine deprotection and without chromatographic purification includes the following steps:
[0038] (1) EGC was dissolved in anhydrous acetonitrile, and then propionic anhydride and a base catalyst were added to it. The resulting mixture was stirred at room temperature to complete the reaction and obtain the protected product.
[0039] (2) Dissolve the protected product in anhydrous dichloromethane, then add pyridine dropwise to obtain a mixed solution, and add palmitoyl chloride dropwise to the mixed solution to carry out the fatty alcohol hydroxyl esterification reaction. After the reaction is completed, the intermediate esterified product is obtained.
[0040] (3) Add 95% (v / v) ethanol to the reaction system after the reaction in step (2) is completed, and react at room temperature to completely remove excess palmitoyl chloride;
[0041] (4) Add hydroxylamine aqueous solution to the reaction system of step (3) to selectively remove propionyl protecting group, and the target crude product is obtained after the reaction is completed.
[0042] (5) The target crude product obtained in step (4) is washed with petroleum ether to remove small polar molecular impurities, and high-purity target product EGC palmitate can be obtained.
[0043] The present invention discloses a method for the directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection. This method involves acylation protection of the ortho-phenolic hydroxyl group of epigallocatechin, directional esterification of the protected product, removal of excess acyl chloride by adding ethanol, selective removal of the propionyl protecting group by adding hydroxylamine reagent, and washing with petroleum ether to remove small polar molecular impurities, thereby obtaining high-purity epigallocatechin palmitate. This method has the advantages of simple operation, simple post-processing (no column chromatography purification required), and high product purity.
[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0045] (1) High deprotection selectivity, improved purity and yield: Hydroxylamine can selectively remove propionyl protecting group under mild conditions and has minimal effect on the target palmitate bond, which fundamentally reduces side reactions and decomposition of the main product, and significantly improves the purity and yield of the product.
[0046] (2) Simplified process and reduced cost: By optimizing the ethanol removal of excess palmitoyl chloride and the petroleum ether washing process, the chromatographic purification steps required in the prior art are completely avoided. This not only greatly simplifies the operation, but also significantly reduces the consumption of solvents and packing materials and the purification cost.
[0047] (3) Safe and environmentally friendly, easy to scale up: It abandons the highly toxic hydrated hydrazine and uses relatively safe hydroxylamine, which improves the greenness and operational safety of the process. Attached Figure Description
[0048] Figure 1 The 1H NMR spectrum of the EGC palmitate obtained in Example 1;
[0049] Figure 2 This is the mass spectrum of the EGC palmitate obtained in Example 1. Detailed Implementation
[0050] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.
[0051] Example 1
[0052] Propionic anhydride (131.5 μL, 1.0 mmol) and triethylamine (138.6 μL, 1.0 mmol) were added dropwise to anhydrous acetonitrile (2 mL) containing dissolved EGC (61.2 mg, 0.2 mmol). The resulting mixture was stirred at room temperature for 4 h. After the reaction was complete, the reaction mixture was extracted with ethyl acetate, washed twice with deionized water, and then dried over anhydrous magnesium sulfate. After filtration, ethyl acetate was removed by rotary evaporation to obtain the protected EGC product. Pyridine (24.2 μL, 0.3 mmol) was added dropwise to anhydrous dichloromethane (2 mL) containing dissolved EGC protected product (117.2 mg, 0.2 mmol), followed by slow dropwise addition of palmitoyl chloride (125.8 μL, 0.4 mmol). The resulting mixture was stirred at room temperature for 0.5 h to obtain the intermediate esterified product.
[0053] After the esterification reaction was completed, 2 mL of 95% (v / v) ethanol was added to the above reaction system, and the reaction was continued for 2 h to completely remove excess palmitoyl chloride. Subsequently, 122.5 μL (2.0 mmol) of 50 wt.% hydroxylamine aqueous solution was slowly added to the above reaction system, and the reaction was stirred at room temperature for 2 h. The reaction solution was extracted with ethyl acetate, washed twice each with 1 mol / L hydrochloric acid solution and deionized water, and dehydrated and dried with anhydrous magnesium sulfate. The organic phase was collected by filtration and rotary evaporation. The resulting crude solid product was suspended in petroleum ether, filtered, and dried to obtain EGC palmitate, with a directed esterification yield of 89% and a purity of 95%.
[0054] Structural determination data: 1H NMR spectrum of EGC palmitate ( Figure 1 The characteristic saturated fatty acid chain signal was observed in the 0.8–1.4 ppm range, confirming the successful attachment of the palmitoyl chain to the EGC molecule. (Mass spectrometry) Figure 2 This further confirms the structural characteristics ([2M-H]). - 1087.18).
[0055] Example 2
[0056] Propionic anhydride (131.5 μL, 1.0 mmol) and N,N-diisopropylethylamine (170.7 μL, 1.0 mmol) were added dropwise to anhydrous acetonitrile (2 mL) containing dissolved EGC (61.2 mg, 0.2 mmol). The resulting mixture was stirred at room temperature for 4 h. After the reaction was complete, the reaction mixture was extracted with ethyl acetate, washed twice with deionized water, and then dried over anhydrous magnesium sulfate. After filtration, ethyl acetate was removed by rotary evaporation to obtain the protected EGC product. Pyridine (24.2 μL, 0.3 mmol) was added dropwise to anhydrous dichloromethane (2 mL) containing dissolved EGC protected product (117.2 mg, 0.2 mmol), followed by slow dropwise addition of palmitoyl chloride (125.8 μL, 0.4 mmol). The resulting mixture was stirred at room temperature for 0.5 h to obtain the intermediate esterified product.
[0057] After the esterification reaction was completed, 2 mL of 95% (v / v) ethanol was added to the above reaction system, and the reaction was continued for 2 h to completely remove excess palmitoyl chloride. Subsequently, 122.5 μL (2.0 mmol) of 50 wt.% hydroxylamine aqueous solution was slowly added to the above reaction system, and the reaction was stirred at room temperature for 2 h. The reaction solution was extracted with ethyl acetate, washed twice each with 1 mol / L hydrochloric acid solution and deionized water, and then dehydrated and dried with anhydrous magnesium sulfate. The organic phase was collected by filtration and rotary evaporation. The resulting crude solid product was suspended in petroleum ether, filtered, and dried to obtain the directed esterification product of EGC palmitate. The structural determination data were the same as in Example 1.
[0058] Example 3
[0059] Propionic anhydride (131.5 μL, 1.0 mmol) and pyridine (80.7 μL, 1.0 mmol) were added dropwise to anhydrous acetonitrile (2 mL) containing dissolved EGC (61.2 mg, 0.2 mmol). The resulting mixture was stirred at room temperature for 4 h. After the reaction was complete, the reaction mixture was extracted with ethyl acetate, washed twice with deionized water, and then dried over anhydrous magnesium sulfate. After filtration, ethyl acetate was removed by rotary evaporation to obtain the protected EGC product. Pyridine (24.2 μL, 0.3 mmol) was added dropwise to anhydrous dichloromethane (2 mL) containing dissolved EGC protected product (117.2 mg, 0.2 mmol), followed by slow dropwise addition of palmitoyl chloride (125.8 μL, 0.4 mmol). The resulting mixture was stirred at room temperature for 0.5 h to obtain the intermediate esterified product.
[0060] After the esterification reaction was completed, 2 mL of 95% (v / v) ethanol was added to the above reaction system, and the reaction was continued for 2 h to completely remove excess palmitoyl chloride. Subsequently, 122.5 μL (2.0 mmol) of 50 wt.% hydroxylamine aqueous solution was slowly added to the above reaction system, and the reaction was stirred at room temperature for 2 h. The reaction solution was extracted with ethyl acetate, washed twice each with 1 mol / L hydrochloric acid solution and deionized water, and then dehydrated and dried with anhydrous magnesium sulfate. The organic phase was collected by filtration and rotary evaporation. The resulting crude solid product was suspended in petroleum ether, filtered, and dried to obtain the directed esterification product of EGC palmitate. The structural determination data were the same as in Example 1.
Claims
1. A method for the directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection, characterized in that, Includes the following steps: (1) Epigallocatechin was dissolved in a solvent, and then propionic anhydride and a base catalyst were added to acylate the ortho-phenolic hydroxyl group for protection. After the reaction was complete, the protected product was obtained. (2) Dissolve the obtained protected product in the reaction solvent, add palmitoyl chloride and pyridine, and esterify the hydroxyl groups of the fatty alcohol; (3) After the esterification reaction is completed, ethanol is added to the system and the reaction is carried out at room temperature to remove excess palmitoyl chloride; (4) After the reaction in step (3) is completed, hydroxylamine aqueous solution is added to the system to remove the propionyl protecting group, and the epigallocatechin palmitate is obtained by post-treatment.
2. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, In step (1), the molar ratio of epigallocatechin to propionic anhydride is 1:(2~30).
3. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, In step (1), the solvent is anhydrous acetonitrile.
4. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, The base catalyst is one of triethylamine, N,N-diisopropylethylamine, or pyridine.
5. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, The molar ratio of epigallocatechin to alkaline catalyst is 1:(2~30).
6. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, In step (2), the molar ratio of the protected product to palmitoyl chloride is 1:(1~10).
7. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, The molar ratio of the protected product to pyridine is 1:(1~10).
8. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, The reaction solvent is anhydrous dichloromethane.
9. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, In step (3), the volume ratio of the added ethanol to the reaction solvent in step (2) is 1:(0.5~2); The concentration of ethanol is 95%.
10. The method for directional preparation of epigallocatechin palmitate based on hydroxylamine deprotection according to claim 1, characterized in that, The molar ratio of epigallocatechin to hydroxylamine is 1:(10~20).
Citation Information
Patent Citations
Method for preparing 3-ester group catechin
CN104292201A