Method for preparing rotundine by utilizing tetrahydropalmatine resolution

Abstract

The invention relates to the technical field of drug synthesis, in particular to a method for preparing rotundine through tetrahydropalmatine resolution, which comprises the following steps: S1, resolving tetrahydropalmatine in a solvent through a chiral resolving agent to obtain levodiastereoisomer salt; s2, carrying out alkalization treatment on the levodiastereoisomer salt, so as to obtain a rotundine crude product; and S3, carrying out recrystallization on the rotundine crude product to obtain rotundine. Raceme tetrahydropalmatine is used as a raw material, a tartaric acid compound is used as a chiral resolving agent for resolution, levodiastereoisomer salt is obtained, rotundine can be obtained through alkalization and recrystallization, and the raw material tetrahydropalmatine can be extracted from plants and can also be obtained through a chemical synthesis method. The raw material of the used chiral resolving agent is a natural product, and is low in toxicity and low in price; the method disclosed by the invention is simple to operate and low in industrialization cost, and the rotundine can be obtained only by three steps of splitting, alkalization and recrystallization.

Description

Technical Field

[0001] This invention belongs to the field of drug synthesis, specifically relating to a method for preparing rotundine by resolving corydaline. Background Technology

[0002] Rotundine, also known as levo-tetrahydropalmatine, chemically named 2,3,9,10-tetramethoxy-5,8,13,13a-tetrahydro-6H-dibenzo[a,g]quinazine, is an alkaloid extracted from plants of the poppy family and other families. Rotundine is a dopamine (DA) receptor blocker, a class of central nervous system analgesics with analgesic and sedative effects. Unlike common opioid receptor agonists, which exert their effects by activating opioid receptors, rotundine does not work by activating opioid receptors but by blocking dopamine receptors, effectively avoiding the risks of opioid addiction and respiratory depression, providing a safe and effective alternative for the treatment of pain and other diseases. Rotundine has a low addictive potential and has great application potential in the treatment and clinical application of drug addiction. Clinically, it is mainly used to treat visceral pain caused by digestive system diseases or functional abnormalities (such as pain from gastric ulcers and duodenal ulcers), general headaches, menstrual pain, postpartum uterine contractions, and tension pain or insomnia caused by pain; it is also used for antitussive, antiarrhythmic, antihypertensive and treatment of functional dyspepsia.

[0003] Currently, the methods for obtaining rotundine are mainly divided into two categories: plant extraction and chemical synthesis (including total synthesis and semi-synthesis). Among them, plant extraction mainly involves extracting from plants such as Corydalis yanhusuo, Tortoise shell, and Diplodocus. Due to the low content of rotundine in plants and excessive harvesting by humans, resources containing these plants are severely scarce, leading to a surge in the cost of preparing rotundine. Obtaining rotundine through extraction methods can no longer meet market demand.

[0004] Total synthesis typically uses inexpensive raw materials such as guaiacol, catechol, and 3,4-dimethoxyphenethylamine as starting materials, and finally obtains rotundine through a series of chemical synthesis reactions. For example... Figure 1 As shown, the relevant patent CN1068113A discloses a method for preparing corydaline from guaiacol as a raw material. It provides a method for the total synthesis of corydaline from guaiacol as a starting material through methylation, chloromethylation, cyanation, amination, condensation hydrogenation, cyclization, and reduction reactions. This production process ultimately yields corydaline without resolving it to obtain rotundine. Furthermore, the dimethyl sulfate, sodium cyanide, P2O5, and POCl3 used in the process are highly toxic or corrosive. The catalytic hydrogenation reduction process requires high-pressure hydrogen and a palladium / carbon catalyst, resulting in high operational risks and environmental unfriendliness.

[0005] like Figure 2As shown, the relevant patent CN108358913A discloses a green synthesis process for rotundine sulfate, which uses catechol as raw material and obtains rotundine through esterification, acylation, nitration, reduction, condensation and reduction, cyclization, and reduction, and then obtains rotundine sulfate by sulfation. However, in this process, dimethyl sulfate is a highly toxic carcinogen, phosphorus trichloride is highly corrosive, catalytic hydrogenation requires high pressure conditions (20-30 atm), the catalyst is expensive, and a large amount of organic solvent is used.

[0006] like Figure 3 As shown, relevant patent CN113896728A discloses a method for preparing rotundine, using 3,4-dimethoxyphenethylamine and 2,3-dimethoxybenzaldehyde as raw materials. After condensation, reduction, and cyclization, berberine is obtained. Berberine then undergoes an asymmetric hydrogenation-reduction reaction catalyzed by a bisphosphine-nickel complex to obtain rotundine. The synthesis steps of the chiral bisphosphine ligand are not disclosed, possibly due to the complexity and high cost of the preparation.

[0007] In the total synthesis of rotundine, isoquinoline cyclic compounds need to undergo an asymmetric hydrogenation reduction reaction to obtain rotundine. This process usually requires the use of expensive chiral catalysts (rhodium, ruthenium, iridium, palladium and ligands, etc.), which results in high production costs and is not conducive to industrial production.

[0008] The semi-synthetic process typically uses berberine hydrochloride or berberine as raw materials, and then resolves them using a chiral resolving agent to prepare rotundine. For example... Figure 4 As shown, a five-step reaction process using berberine hydrochloride as raw material, involving demethylene, O-methylation, sodium borohydride reduction, (+)-di-p-methylbenzoyl tartaric acid resolution, and alkalization to obtain rotundine, was disclosed, with an overall yield of approximately 25%. The yield of this resolution process needs further improvement.

[0009] like Figure 5 As shown, the improved synthesis process of Rotondin uses berberine as the starting material and obtains the target compound Rotondin through a three-step reaction of potassium borohydride reduction, L-tartaric acid resolution, and alkalization. The yield is 40.4% and the product content is 99.9%.

[0010] like Figure 6 As shown, patent CN106518864A discloses a method for synthesizing levomopathogenic acid from berberine. Using berberine as a raw material, levomopathogenic acid is obtained through ring-opening, methoxylation, racemization with sodium borohydride, and resolution with D-p-methyldibenzoic acid and tartaric acid. The dextromopathogenic acid contained therein can be recycled and reused.

[0011] In the synthesis of Rotondin, the semi-synthetic process demonstrates significant industrial advantages. Compared to the lengthy reaction steps of total synthesis, semi-synthesis significantly shortens the process through streamlined design, with the key step being the resolution process. Utilizing an efficient resolution process, chiral compounds can be precisely separated, and after alkalization, high-purity products can be directly obtained. This not only simplifies the separation operation but also reduces impurities at the source, resulting in significantly lower byproducts compared to total synthesis.

[0012] Total synthesis involves multiple lengthy reaction steps, resulting in a long production cycle and large amounts of byproducts, which significantly increases the difficulty of separation and purification, and raises labor and equipment costs. Its key asymmetric catalytic reduction step also relies on expensive chiral catalysts, further increasing production costs and imposing stringent requirements on reaction conditions, severely limiting its industrialization potential. Clearly, semi-synthesis, with its high purity achieved through efficient resolution, simple separation, and low byproducts, is superior to total synthesis and has become the preferred option for the synthesis of Rotondin. Summary of the Invention

[0013] This application provides a method for preparing rotundine using tetrahydropalmatine, addressing the shortcomings of existing processes that use berberine hydrochloride or berberine as raw materials. In the latter, the synthesis of berberine from berberine hydrochloride requires two steps: Lewis acid-catalyzed ring-opening and methylation, resulting in a yield of only about 66%. Furthermore, the ring-opening product is complex and requires purification, and the obtained berberine needs further reduction to be converted into tetrahydropalmatine, increasing production costs. The purpose of this invention is to provide a method for preparing rotundine using tetrahydropalmatine as a raw material, employing tartaric acid compounds as chiral resolving agents for efficient separation of rotundine, thus solving the problems of numerous steps, low yield, difficult separation, and high production costs associated with existing processes.

[0014] This application provides a method for preparing rotundine by resolving corydaline, the method comprising the following steps: S1, resolving corydaline in a solvent using a chiral resolving agent to obtain a levorotatory diastereomer salt; S2, alkalizing the levorotatory diastereomer salt to obtain crude rotundine; S3, recrystallizing the crude rotundine to obtain rotundine.

[0015] Optionally, the specific method of S1 is as follows: the molar ratio of chiral resolving agent to corydaline is 0.5-3, the reaction temperature is 30-110℃, the levorotatory diastereomer salt is obtained, the crystallization temperature is -20℃ to room temperature, and the crystallization time is 6-24h.

[0016] Optionally, the chiral resolving agent is D-tartaric acid, D-dibenzoyl tartaric acid, L-dibenzoyl tartaric acid, D-p-methoxydibenzoyl tartaric acid, L-p-methoxydibenzoyl tartaric acid, di-p-toluyl-L-tartaric acid, or L-diacetyl tartaric acid.

[0017] Optionally, the amount of solvent used is 100-500 mL.

[0018] Optionally, the solvent is any single solvent or a mixture of two or more solvents selected from methanol, ethanol, isopropanol, dichloromethane, acetone, ethyl acetate, acetonitrile, n-propanol, or tetrahydrofuran.

[0019] Optionally, the specific method of S2 is as follows: dissolve the levorotatory diastereomer salt in deionized water, add an alkaline solution to adjust the pH value to 10-14 after complete dissolution, react at room temperature for 0.5-3 hours, filter, and collect the solid to obtain crude Rotondine.

[0020] Optionally, the alkaline solution is sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, or sodium bicarbonate.

[0021] Optionally, the specific method of S3 is as follows: add the crude rotundine to ethanol, heat and stir at 70-90°C until completely dissolved, reflux, then add purified water at 70-100°C, cool at room temperature and stand for 2-24 hours, filter, and dry to obtain the finished rotundine product.

[0022] Optionally, the mass-volume ratio of crude rotundine, ethanol and purified water in S3 is 1:(6-15):(6-15).

[0023] This application proposes an application for preparing rotundine using the resolution of corydaline, and the prepared rotundine is used to prepare analgesic, sedative and hypnotic drugs.

[0024] Therefore, this application has at least the following beneficial effects: (1) In the embodiments of this application, corydaline is used as a raw material, dissolved in a solvent, and under the action of chiral resolving agents such as tartaric acid compounds, as Figure 8 As shown, the carboxyl group in the chiral resolving agent tartaric acid reacts with the tertiary amine group in fumarate ethyl to form a diastereomer salt. The two isomer salts (levorotatory and dextrorotatory) are separated by their differences in crystallization rate and solubility, yielding the levorotatory diastereomer salt. Then, by adding a base, the protonated H of the levorotatory diastereomer is removed, resulting in the dissociation of the protonated alkaloid cation and tartrate anion, thus obtaining crude rotundine. Finally, recrystallization purification yields optically pure rotundine, significantly increasing the yield. (2) This invention uses tartaric acid and its derivatives as an efficient and inexpensive chiral resolution system. This type of resolving agent can not only form diastereomer salts with significantly different solubilities with the enantiomers of fumaric acid, thereby achieving efficient resolution with high optical purity, but also performs well in industrialization: its raw material (tartaric acid) is a renewable natural product with obvious cost advantages; the fractional crystallization process used is mature and stable, and the production scale is easy to scale up, avoiding the industrialization bottlenecks of expensive equipment and small processing capacity of chiral chromatography and harsh conditions and high cost of enzyme catalysis, laying a solid foundation for the green and economical preparation of Rotonin. (3) The raw material cost of the present invention is low. The raw material, corydaline, is widely available and easy to obtain. It can be extracted from plants or obtained by chemical synthesis, which greatly reduces the production cost. (4) The preparation and synthesis route of the present invention is short and simple to operate. The rotundine can be obtained by resolving, alkalizing and purifying corydaline, avoiding the multiple complex chemical transformations required by the traditional semi-synthetic method starting from berberine hydrochloride or berberine, and reducing the cumulative loss and impurity introduction risk caused by multiple reactions.

[0025] This solved the problems of the original process, such as many steps, low yield, difficult separation, and high production cost.

[0026] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0027] The following will clearly illustrate the preparation process route, related aspects, and advantages of the present application of rotundine, in conjunction with the accompanying drawings and embodiments, wherein: Figure 1 This is a flowchart illustrating a method for preparing rotundine using tetrahydropalmatine according to an embodiment of this application; Figure 2 A flowchart of the synthesis process route 1 provided by the prior art; Figure 3 A flowchart of the synthesis process route 2 provided by the prior art; Figure 4 A flowchart of the synthesis process route 3 provided for the prior art; Figure 5 A flowchart of the synthesis process route 4 provided for the prior art; Figure 6 A flowchart of the synthesis process route 5 provided for the prior art; Figure 7 A flowchart of the synthesis process route 6 provided for the prior art; Figure 8 A flowchart of the synthesis process route 1 provided by the prior art; Figure 9 Circular dichroism chromatograms of corydaline, dextrorotatory corydaline, and rotundine provided for the prior art; Figure 10 High-resolution mass spectra of rotundine provided for existing technologies; Figure 11 The hydrogen NMR spectrum of Rotonde provided for existing technology; Figure 12 The carbon NMR spectrum of Rotonde provided for existing technology; Figure 13 The ultraviolet absorption spectrum of rotundine provided for existing technology; Figure 14 Infrared absorption spectrum of rotundine provided for existing technology; Figure 15 High-performance liquid chromatogram of rotundine provided for existing technology; Figure 16 Chiral liquid chromatograms of corydaline and rotundine provided for the prior art. Detailed Implementation

[0028] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] In the embodiments of this application, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0030] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0031] In this embodiment, the tetrahydropalmatine was purchased from Hubei Weideli Chemical Reagent Co., Ltd., with a purity of ≥98.6%; the chiral resolving agent was purchased from Anaiji Chemical, with a purity of ≥98.6%; the solvent was purchased from Chengdu Kelong Chemical Co., Ltd.; the alkali was from Tianjin Kemio Chemical Reagent Co., Ltd.; and the purified water was prepared by the laboratory ultrapure water system.

[0032] This application provides a method for preparing rotundine using the resolution of corydaline, such as... Figure 1 As shown, it includes the following steps: S1. Resolve corydaline in a solvent using a chiral resolving agent to obtain the levorotatory diastereomer salt.

[0033] The amount of solvent used is 100-500 mL, and the solvent is any single solvent or a mixture of two or more solvents selected from methanol, ethanol, isopropanol, dichloromethane, acetone, ethyl acetate, acetonitrile, n-propanol or tetrahydrofuran.

[0034] It is understood that the embodiments of this application use a chiral resolving agent to separate corydaline in a solvent and obtain a levorotatory diastereomer salt. The core function is to achieve precise separation of the optical isomers of corydaline. Compared with the unresolved mixed isomers, the diastereomer salt of the specific levorotatory configuration can effectively avoid the side effects or activity interference that may be caused by other configurations. It can not only improve the purity and bioavailability of the target active ingredient (such as analgesic pharmacological effects), but also obtain a highly active configuration by direction. This lays a key material foundation for the subsequent development of corydaline drugs with more defined efficacy, higher safety and more precise dosage.

[0035] In the embodiments of this application, the specific method of S1 is as follows: the molar ratio of chiral resolving agent to corydaline is 0.5-3, the reaction temperature is 30-110℃, the reaction time is 1-5h, and the levorotatory diastereomer salt is obtained. The crystallization temperature is -20℃ to room temperature, and the crystallization time is 6-24h.

[0036] The chiral resolving agents are D-tartaric acid, D-dibenzoyl tartaric acid, L-dibenzoyl tartaric acid, D-p-methoxydibenzoyl tartaric acid, L-p-methoxydibenzoyl tartaric acid, di-p-toluyl-L-tartaric acid, and L-diacetyl tartaric acid.

[0037] Specifically, the optimal chiral resolving agent is dextrorotatory tartaric acid, the solvent is methanol, the reaction temperature is 70℃, the reaction time is 3h, the crystallization temperature is room temperature, the crystallization time is 12h, and the solvent volume is 100mL.

[0038] Specifically, dextrorotatory tartaric acid, as a natural, high-optical-purity acidic reagent, has a molecular structure that allows it to form stable salt bonds with levofloxacin via the carboxyl and amino groups. Due to spatial complementarity, the diastereomeric salt formed has a much lower solubility in polar solvents than the salt formed with dextrorotatory tartaric acid, and it avoids the residual impurities associated with benzene ring resolving agents, resulting in lower costs. Methanol, as a polar protic solvent, has a dielectric constant suitable for the solubility of both tartaric acid and fumarate, ensuring complete dissolution of the raw materials through hydrogen bonding while amplifying the solubility difference between the two diastereomeric salts. With a low boiling point, it is easy to recover and its toxicity is controllable. A dosage of 100 mL achieves a balance between the dissolution of the raw material and the precipitation of the target salt, avoiding the problem of insufficient solubility of ethanol or the narrowing of the solubility difference of highly polar solvents. A reaction at 70℃ for 3 hours can ensure that the salt formation reaction is complete and there is no raw material residue, avoiding the decrease in system stability caused by excessive time. Room temperature crystallization can avoid the crystallization rate being too slow due to excessively low temperature and the impurity encapsulation caused by local overcooling, which affects the purity. A crystallization time of 12 hours can ensure that the target salt is fully precipitated, improving the yield, while preventing crystal agglomeration due to excessive crystallization, which increases the difficulty of separation.

[0039] S2. The levorotatory diastereomer salt was alkalized to obtain crude Rotondine.

[0040] It is understood that the embodiments of this application utilize an acid-base neutralization reaction. The levorotatory diastereomer salt is an ionic salt formed by levorotatory corydaline and a chiral resolving agent through the carboxyl and amino groups. The alkaline reagent added during the alkalization treatment provides OH- - , with H in salt + A neutralization reaction occurs, generating water-soluble tartrate salts. At the same time, levo-tetracycline is converted from an ionic state to a free molecular state. Since the free state of rotundine has low solubility in the aqueous phase, it will precipitate out in solid form, thereby achieving the separation of rotundine from the chiral resolving agent and finally obtaining crude rotundine.

[0041] In the embodiments of this application, the specific method of S2 is as follows: the levorotatory diastereomer salt is dissolved in deionized water, and after complete dissolution, an alkaline solution is added to adjust the pH value to 10-14. The mixture is reacted at room temperature for 0.5-3 hours, filtered, and the solid is collected to obtain crude Rotondine.

[0042] The alkaline solution is sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate, or sodium bicarbonate.

[0043] Specifically, the optimal base is sodium hydroxide, the optimal pH is 12, and the optimal reaction time is 0.5 h.

[0044] It is understandable that sodium hydroxide was chosen as the optimal base in this application embodiment because, as a strong alkaline reagent, it can dissociate to release a high concentration of OH⁻, which can quickly neutralize the acid radical in the levorotatory diastereomer salt. Furthermore, the reaction product is readily soluble in water, laying the foundation for subsequent separation of the target product by filtration. The pH value was controlled within the optimal range of 12. This alkalinity ensures complete ion bond breakage in the salt, allowing levorotatory corydaline to be fully converted into a free state, avoiding incomplete dissociation due to insufficient alkalinity at pH < 12, while also preventing excessive alkalinity at pH > 12 from damaging the rotonidine molecular structure. A reaction time of 0.5 h was set as the optimal reaction time, ensuring complete reaction while effectively preventing a decrease in system stability due to excessively long reaction times. Finally, the solid was collected by filtration, successfully obtaining crude rotonidine. The entire process, through the synergistic effect of various conditions, achieved the efficient preparation of crude rotonidine.

[0045] S3. Recrystallize the crude rotundine to obtain rotundine.

[0046] It is understood that in this embodiment, rotundine is dissolved in ethanol. Under heating and stirring at 70-90°C, crude rotundine can be completely dissolved to form a homogeneous solution. At the same time, a small amount of insoluble impurities that may remain in the crude product remain in a solid state. The reflux process can further ensure that rotundine is fully dissolved. Adding purified water at 70-100°C can maintain the system temperature to prevent premature precipitation of rotundine and narrow the solubility window of rotundine in the solvent by adjusting the polarity of the mixed solvent. When the system is cooled at room temperature and left to stand for 2-24 hours, the solubility of rotundine drops sharply due to the temperature decrease and the change in solvent polarity. It will precipitate in the form of regular crystals. The soluble impurities in the crude product have high solubility in the mixed solvent system and remain stably dissolved in the mother liquor even after cooling. They will not precipitate with the rotundine crystals. Finally, high-purity rotundine product is obtained by filtering to separate the crystals and drying.

[0047] In this embodiment, the specific method of S3 is as follows: crude rotundine is added to ethanol, heated and stirred at 70-90°C until completely dissolved, refluxed, then purified water at 70-100°C is added, cooled at room temperature and allowed to stand for 2-24 hours, filtered, and dried to obtain the finished rotundine product.

[0048] The mass-volume ratio of crude rotundine, ethanol and purified water is 1:(6-15):(6-15).

[0049] Specifically, the optimal heating temperature is 80℃, the optimal purified water temperature is 80℃, and the optimal crystallization time is 12h.

[0050] Specifically, a heating temperature of 80℃ ensures complete dissolution of crude rotundine in ethanol while preventing excessive ethanol evaporation at higher temperatures, which could lead to concentration fluctuations and reduce impurity co-crystallization caused by localized supersaturation. At this temperature, rotundine molecules exhibit good stability with no risk of thermal degradation. The purified water temperature is controlled at 80℃ to match the ethanol heating system, preventing premature precipitation of rotundine due to sudden temperature drops caused by the addition of cold water, thus avoiding impurity encapsulation and reduced purity. Furthermore, the 80℃ water temperature prevents excessive solvent evaporation or system boiling, ensuring a stable mixed solvent ratio. A 12-hour crystallization time ensures sufficient crystallization, preventing excessively small crystal particles from adsorbing impurities. Simultaneously, 12 hours of settling allows crystals to slowly grow into regularly shaped, uniformly sized particles, improving filtration and drying efficiency, ensuring rotundine purity, and achieving high yield and good crystal physical properties.

[0051] This application also proposes an application for preparing rotundine by resolving corydaline, and the prepared rotundine is used to prepare analgesic, sedative and hypnotic drugs.

[0052] Specifically, rotundine exerts a mild and long-lasting analgesic effect by acting on specific receptors in the central nervous system to inhibit pain signal transmission. It is particularly suitable for chronic persistent pain and visceral colic. Simultaneously, it regulates the balance between excitation and inhibition in the central nervous system, producing a sedative-hypnotic effect, improving sleep quality, and is less likely to induce significant dependence. This application not only expands the channels for transforming the medicinal value of corydalis ethylsin but also provides a high-quality candidate ingredient for the research and development and production of clinical analgesics and sedative-hypnotic drugs. This will help develop drug formulations with more definite efficacy and higher safety, meeting the diverse clinical needs for such drugs.

[0053] Example 1 A method for preparing rotundine using tetrahydropalmatine resolution includes the following steps: S1. Add 5g of corydaline to a 250mL flask, add 350mL of ethanol, and then add 2.5g of dextrorotatory tartaric acid. Stir the reaction at 80℃ for 5h, cool to room temperature, and then crystallize at -20℃ for 12h to obtain the levorotatory diastereomer salt.

[0054] S2. Add the levorotatory diastereomer salt obtained in S1 to a 250 mL flask, add deionized water to dissolve it completely, then add 4.5 mol / L potassium hydroxide solution to adjust the pH of the solution to 12, stir the reaction at room temperature for 0.5 h, and then filter to obtain crude Rotondin.

[0055] S3. Add the crude rotundine obtained in S2 to a 100 mL flask, add ethanol and heat to dissolve at 80 °C, then add an equal amount of purified water at 85 °C, stir thoroughly, cool and crystallize at room temperature for 10 h, filter and dry to obtain rotundine.

[0056] Example 2 A method for preparing rotundine using tetrahydropalmatine resolution includes the following steps: S1. Add 5g of corydaline to a 250mL flask, add 300mL of methanol, and then add 2.5g of dextrorotatory tartaric acid. Stir the reaction at 70℃ for 4h, cool to room temperature, and then crystallize at 0℃ for 12h to obtain the levorotatory diastereomer salt.

[0057] S2. Add the levorotatory diastereomer salt obtained in S1 to a 250 mL flask, add deionized water to dissolve it completely, then add 4.5 mol / L sodium hydroxide solution to adjust the pH of the solution to 12, stir the reaction at room temperature for 0.5 h, and then filter to obtain crude Rotonide.

[0058] S3. Add the crude rotundine obtained in S2 to a 100 mL flask, add ethanol and heat to dissolve at 70 °C, then add an equal amount of purified water at 90 °C, stir thoroughly, cool and crystallize at room temperature for 24 h, filter and dry to obtain rotundine.

[0059] Example 3 A method for preparing rotundine using tetrahydropalmatine resolution includes the following steps: S1. Add 5g of corydaline to a 250mL flask, add 100mL of methanol, and then add 2.5g of dextrorotatory tartaric acid. Stir the reaction at 70℃ for 3h, and crystallize at room temperature for 12h to obtain the levorotatory diastereomer salt.

[0060] S2. Add the levorotatory diastereomer salt obtained in S1 to a 250 mL flask, add deionized water to dissolve it completely, then add 4.5 mol / L sodium hydroxide solution to adjust the pH of the solution to 12, stir the reaction at room temperature for 0.5 h, and then filter to obtain crude Rotonide.

[0061] S3. Add the crude rotundine obtained in S2 to a 100 mL flask, add ethanol and heat to dissolve at 80 °C, then add an equal amount of purified water at 80 °C, stir thoroughly, cool and crystallize at room temperature for 12 h, filter and dry to obtain rotundine.

[0062] Performance testing The melting point of the product was determined by capillary method to be 141-143℃, which is a narrow melting point range, indicating high purity.

[0063] Specific rotation: Accurately weigh the product, dissolve and dilute to volume with ethanol, and measure the specific rotation using a polarimeter at 20°C. = -290° to -295° (c 0.5, EtOH) (literature value: -292° (c 0.5, EtOH)), further confirming its left-handed configuration and optical purity.

[0064] like Figure 9 As shown, circular dichroism spectroscopy analysis of different configurations of corydaline revealed that the racemic corydaline spectrum was a flat, near-zero straight line with no Cotton effect signal. Since the circular dichroism signals of equal amounts of the levorotatory and dextrorotatory enantiomers completely canceled each other out, it exhibited optical inertness and could be used as a baseline reference to prove that the starting material was not optically active. The dextrorotatory corydaline spectrum showed a strong characteristic Cotton effect peak, with a negative peak at approximately 285 nm and a positive peak near 230 nm, confirming that it is an optically pure enantiomer with a specific absolute configuration (R-configuration). The spectral line of rotundine (levorotatory corydaline) showed near-perfect mirror symmetry with the dextrorotatory form, with a positive peak at 285 nm and a negative peak near 230 nm. This mirror symmetry served as the basis for determining the enantiomer.

[0065] In summary, the method of this invention successfully separated racemic corydaline to obtain the optically active levorotatory and dextrorotatory forms. By comparing with known standard spectra, the levorotatory form can be clearly identified as the target product, rotundine, and its clear and strong CD signal proves that the final product has high optical purity.

[0066] The product structure was confirmed by a combination of high-resolution mass spectrometry (HR-MS), proton nuclear magnetic resonance (¹H NMR), carbon nuclear magnetic resonance (¹³C NMR), ultraviolet absorption spectroscopy (UV-vis), and free-float infrared absorption spectroscopy (FT-IR).

[0067] like Figure 10 As shown, the measured [M+H]⁺m / z is 356.1865, which is consistent with the theoretical value (C). 21 H 26 NO4 + (356.1862) matches, confirming the molecular formula.

[0068] like Figure 11 The image shown is the ¹H NMR spectrum of Rotondin.

[0069] 1H NMR (600 MHz, DMSO-d6) δ 6.88 (s, 2H), 6.87 (s, 1H), 6.68 (s, 1H), 4.07 (d, J = 15.7 Hz, 1H), 3.77 (s, 3H), 3.75 (s, 3H), 3.73 (s, 3H), 3.72 (s,3H), 3.39 (t, J = 9.8 Hz, 2H), 3.36 (d, J = 5.3 Hz, 2H), 3.10 (s, 1H), 2.93(s, 1H), 2.62 – 2.44 (m, 2H). The above characterization data are consistent with the structure of rotundine and with the rotundine standard spectrum. Figure 1 To.

[0070] like Figure 12 The image shown is the carbon nuclear magnetic resonance (¹³C NMR) spectrum of Rotondin.

[0071] 13 C NMR (151 MHz, DMSO-d6) δ 149.80, 147.17, 147.15, 144.37, 129.65, 128.30, 127.68, 126.35, 123.64, 111.66, 111.13, 109.37, 59.54, 58.78, 55.70, 55.66, 55.38, 53.41, 50.91, 35.67, 28.57. The number of carbon signals and chemical shifts are consistent with the structure.

[0072] The ultraviolet-visible spectrophotometry method was used. Accurately weigh the sample, dissolve it in 0.5% sulfuric acid solution, and quantitatively dilute it to prepare a solution containing approximately 30 μg per ml. The absorbance was measured at a wavelength of 281 nm. The absorption coefficient (…) The value is 150-160.

[0073] like Figure 13 The image shows the UV absorption spectrum of rotundine and the spectrum of rotundine standard. Figure 1 To.

[0074] Fourier transform infrared spectroscopy (FT-IR) was used in this experiment. Dry powdered potassium bromide was placed in a mortar and the test sample was mixed with potassium bromide at a ratio of 1:100. After being pressed into thin sheets using a tablet press, the test was performed. The instrument scanning range was 500-4000 cm-1.

[0075] like Figure 14The image shows the infrared absorption spectrum (FT-IR) of Rotonde.

[0076] IR(KBr) σ: 3001, 2936, 2828, 2748, 1608, 1513, 1493, 1457, 1386, 1336, 1278, 1257, 1228, 1139, 1106, 1080, 1053, 1026, 997, 956, 855, 806, 781 cm －1 Its infrared spectrum is consistent with the standard spectrum.

[0077] The above data fully confirm that the obtained product is rotundine.

[0078] High-performance liquid chromatography (HPLC) was used with octadecylsilane-bonded silica gel as the stationary phase; the mobile phase was phosphate buffer [0.05 mol / L potassium dihydrogen phosphate solution and 0.05 mol / L sodium heptanesulfonate solution (1:1), containing 0.2% triethylamine, with the pH adjusted to 6.5±0.05 by phosphoric acid]-methanol (35:65); the detection wavelength was 280 nm; and the injection volume was 20 μL.

[0079] like Figure 13 As shown, the HPLC purity of the rotundine products obtained in the three examples was not less than 99.8%, which is far higher than the pharmaceutical standard (usually requiring ≥98.5%).

[0080] Chiral high-performance liquid chromatography (Chiral HPLC) was used with a Daicel Chiralcel OD chiral column, methanol [0.2% ammonia (7M, soluble in methanol)] as the mobile phase, isogradient elution, and the detection wavelength was 214 nm.

[0081] like Figure 14 As shown, the enantiomeric excess value (ee value) of the Rotondin product prepared by the present invention was all > 99.5%, indicating that the product is almost a single optical enantiomeric product with excellent chiral separation effect.

[0082] According to the embodiments of this application, a method for preparing rhotonidine using the resolution of corydaline is proposed. Corydaline is used as raw material. After being dissolved in a solvent, under the action of a chiral resolving agent tartaric acid compound, the carboxyl group of tartaric acid reacts with the tertiary amine group of corydaline to generate diastereomer salts through an acid-base neutralization reaction. The difference in crystallization rate and solubility between the levorotatory and dextrorotatory isomer salts is then used to achieve separation, obtaining the levorotatory diastereomer salt. Subsequently, a base is added to remove H from the salt, causing the protonated alkaloid cation to dissociate from the tartrate anion, obtaining crude rhotonidine. Finally, optically pure rhotonidine is obtained by recrystallization purification with a significant increase in yield. Meanwhile, the chiral resolving agent tartaric acid and its derivatives are derived from renewable natural products (extracted from wine by-products), which are inexpensive and have high resolving efficiency. The raw material, corydaline, is widely available and easily obtained (either through plant extraction or chemical synthesis), significantly reducing production costs. The synthetic route is short and simple, requiring only three steps: resolving, alkalizing, and purifying to obtain rotundine. This avoids the complex multi-step transformations of traditional semi-synthetic methods starting from berberine hydrochloride or berberine, reducing cumulative reaction losses and the risk of impurity introduction. In summary, this process effectively solves the problems of numerous steps, low yield, difficult separation, and high production costs associated with the original rotundine preparation process.

[0083] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0084] The present application and its embodiments have been described above. This description is not restrictive, and the actual application is not limited thereto. In conclusion, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the spirit of this application, such design should fall within the protection scope of this application.

Claims

1. A method for the preparation of a racemic mixture of rotundine by resolution with fumaracyl, characterized in that, The method comprises the following steps: S1, resolving fumarile by chiral resolving agent in solvent to obtain left non- enantiomeric salt; S2, alkalizing the left non-enantiomeric salt to obtain rotundine crude product; S3, recrystallizing the rotundine crude product to obtain rotundine.

2. The method for preparing a racemic rotundine by using a resolving agent of tetrahydropalmatine according to claim 1, characterized in that, The specific method of S1 is that the molar ratio of fumarile to chiral resolving agent is 0.5-3, the reaction temperature is 30-110 DEG C, the reaction time is 1-5 h, the left non- enantiomeric salt is obtained, the crystallization temperature is-20 DEG C to room temperature, and the crystallization time is 6-24 h.

3. The method for preparing a racemic rotundine by using a resolving agent of tetrahydropalmatine according to claim 2, characterized in that, The chiral resolving agent is D-tartaric acid, D-dibenzoyl tartaric acid, L-dibenzoyl tartaric acid, D-p-methoxydibenzoyl tartaric acid, L-p-methoxydibenzoyl tartaric acid, di-p-toluoyl-L-tartaric acid or L-diacetyl tartaric acid.

4. The method for preparing a racemic rotundine by using a resolving agent of tetrahydropalmatine according to claim 1, characterized in that, The amount of solvent is 100-500 mL.

5. The method for preparing the rotundine by using the racemization of the tetrahydropalmatine according to claim 1, characterized in that, The solvent is any one single solvent or two or more mixed solvents selected from the group consisting of methanol, ethanol, isopropanol, dichloromethane, acetone, ethyl acetate, acetonitrile, n-propanol and tetrahydrofuran.

6. The method for preparing a racemic rotundine by using a resolving agent of tetrahydropalmatine according to claim 1, characterized in that, The specific method of S2 is that the left non-enantiomeric salt is dissolved in deionized water, after complete dissolution, an alkali solution is added to adjust the pH value to 10-14, and the reaction is carried out at room temperature for 0.5-3 h, then filtration is carried out to collect the solid to obtain rotundine crude product. The alkali solution is sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, sodium carbonate or sodium bicarbonate.

7. The method for preparing a racemic rotundine by using a resolving agent of tetrahydropiperonyl alcohol according to claim 6, characterized in that, The specific method of S3 is that the rotundine crude product is added into ethanol, heated and stirred at 70-90 DEG C until completely dissolved, refluxed, then purified water with a temperature of 70-100 DEG C is added, cooled at room temperature and placed for 2-24 h, filtered and dried to obtain rotundine product.

8. The method for preparing a racemic rotundine by using a cleistanine according to claim 1, characterized in that, The mass-volume ratio of rotundine crude product, ethanol and purified water in S3 is 1:(6-15):(6-15).

9. The method for preparing a racemic rotundine by using a cleistanine according to claim 1, characterized in that, The prepared rotundine is used for preparing analgesic and sedative hypnotic drugs.

10. The application of the preparation of rotundine using the resolution of corydaline according to any one of claims 1 to 9, characterized in that, ​

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