CN101514216A - Method for synthesizing crocin glucoside - Google Patents

Abstract

The invention provides a synthetic method of crocin glucoside, which comprises a, synthesizing _C10 compound 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II); b, synthesis of C ₅ compound E-2-methyl-4-bromo-2-butenoic acid methyl ester; c, taking the above two compounds as raw materials to synthesize crocetin dimethyl ester; d, crocetin acid Dimethyl ester hydrolysis reaction to obtain crocetin; e, use crocetin to react with carbonylimidazole to synthesize crocetin imidazole and then synthesize crocetin glucoside. The synthesis process of the invention has the advantages of simplified operation and yield, high synthesis purity, high yield, cost saving and strong industrial applicability.

Description

The synthetic method of saffron glucoside

technical field

The invention relates to a synthesis method of saffron glucoside, which belongs to the field of medicine.

Background technique

Saffron, also known as saffron or saffron (Saffron, Crocus, stativus L), belongs to the Iridaceae plant, mainly referring to the upper part and stigma of the saffron style. Because the aqueous solution of saffron has bright yellow color and fragrance, it is a very expensive spice, which is often used in high-grade food additives and food coloring, and can also be used as high-grade dyes for silk, cotton and wool products. In Chinese Pharmacopoeia, saffron can promote blood circulation and remove blood stasis, cool blood and detoxify, relieve stagnation and soothe the nerves, and is used for the treatment of amenorrhea, postpartum stasis, spotting due to dampness, depression, and palpitations. Modern medical research has found that saffron has many curative effects such as treating cardiovascular diseases and preventing atherosclerosis, treating chronic viral hepatitis and liver cirrhosis, anticancer activity, improving learning and memory disorders induced by alcohol, and improving immune function. The multi-faceted health care and therapeutic functions have more and more attracted people's attention to the medicinal value of saffron.

The main chemical components of saffron, because the pharmacological effects of saffron are mainly reflected in the stigma of saffron, so the research on saffron mainly focuses on the research on the chemical components of the stigma, the main chemical components of the stigma include: (1) Volatile oil, there are more than 30 volatile oil components separated from the stigma of plants, including α-phenylethanol, naphthalene, α-butenolide, higher fatty acids, campesterol, stigmasterol, β-sitosterol , ursolic acid, oleanolic acid, octahydrotomato hydrocarbons, hexahydrotomato hydrocarbons, etc. ^[1] . (2) Conjugated polyenes and their glycosides: there are mainly two types, one is carotenoids and their glycosides, and the other is carotene. These two types of compounds are the main colored active ingredients in saffron. a. Carotene ^[2-6] mainly includes α, β-carotene, lycopene and zeaxanthin, and its structure is:

α-carotene structure:

β-carotene structure:

Lycopene structure:

Zeaxanthin structure:

(2) Carotenoids and their glycosides ^[7-10]

This type of compound is mainly a series of ester (crocins) compounds formed by the carotenoid crocretin and sugar. It is the main medicinal component of saffron, and its main structure is all-trans crocin glucoside. , see the following structure:

in

R ₁ ＝R ₂ ＝H α-crocetin (α-crocetin) MW＝328

R ₁ ＝Me R ₂ ＝H β-crocetin (β-crocetin) MW＝342

R ₁ ＝R ₂ ＝Me γ-crocetin (γ-crocetin) MW＝354

R ₁ =R ₂ =X crocin-1 (crocin-1) MW = 976

R ₁ =y R ₂ =X crocin-2 (crocin-2) MW = 814

R ₁ =R ₂ =Y crocin-3 (crocin-3) MW = 652

R ₁ =X R ₂ =H crocin-3 (crocin-3) MW = 652

R ₁ =X R ₂ =Z crocin-4 (crocin-4) MW = 1138

13-cis saffron glycoside

In the cis structure, R ₁ =R ₂ =y MW=976

(3) Other compounds ^{[11, 12]} , picrocrocin is the substance that causes bitterness in saffron, and it is also one of the active ingredients of saffron. The main components of saffron perianth: saffron perianth mainly contains kaempferol and glycosides, astragalin, quercetin-2-p-suzunoyl glucoside (helichrysoside), Kaempferol-3-o-β-o-glucopyranoside (1-2) 6-acetylglucopyranoside (Kaempferol-3-o-β-glucopyranosyl(1-2)β-o-6-acetylglucopyranoside ) (1), kaempferol-3-o--β-D-glucopyranosyl (1-2) glucopyranosyl (Kaempferol-3-o-β-glucopyranosyl (1-2) β-D- glucopyranoside), Kaempferol-3-β-D-glucopyranosyl (1-2)β-D-glucopyranoside (Kaempferol-3-β-D-glucopyranosyl(1-2)β-D-glucopyranoside) , nonacosane, etc., wherein, Kaempferol-3-o-β-o-glucopyranosyl (1-2) 6-acetyl glucopyranosyl (Kaempferol-3-o-β-glucopyranosyl (1- 2) β-o-6-acetylglucopyranoside) (1) astragalin (2) kaempferol (kaempferol) and glycoside (3) structure is ^[13] :

The preparation method of the active ingredient of saffron adopts the extraction and separation preparation method. Natural saffron mainly has two types of active ingredients, one is volatile components such as trimethyl-cyclohexene derivatives and crocin aldehyde, The other is active ingredients with strong polarity such as crocin glucoside and crocetin acid. Biosynthetic preparation method: the main active ingredient of saffron is saffron glucoside, and the research on saffron glucoside has also become the main direction of research on saffron. Since the content of saffron glucoside in saffron is generally 8-11% ^[14] , the yield of saffron glucosides obtained after separation is low. Therefore, biologists try to increase the content of saffron glucoside and other active ingredients in saffron through biosynthesis, so as to achieve the purpose of controllable growth of saffron active ingredients, and finally solve the shortage of saffron drug resources. Find an effective way.

It is generally believed that crocetin is formed in plants through glycosyl reactions using crocetin as a precursor, and crocetin, like most carotenoids in plants, is synthesized through the isoprene pathway, and Some studies believe that 20-carbon crocetin is degraded from 40-carbon carotenoids (such as phytoene, etc.), rather than condensed into dimers by two molecules of 10-carbon compounds ^{[14 ]} . The current research mainly uses crocetin as the substrate, and the substrate is glycosylated by suspension cultured bacteria or cell-free system extracted from callus ^[15] . Dufresne et al. ^[16] used shoots to induce callus, and the system did not contain carotene. After being freeze-dried, it was extracted with Tris-HCl at pH 7.5, and the obtained cell-free system was used for enzymatic glycosylation reaction, and the substrate concentration of the glycosylation reaction could reach 1750 μM and 2500 μM, respectively. The optimum pH of the reaction was 7.0 and 7.6, and various crocetin glycosyl products were formed after 150 minutes of reaction, among which crocetin monoglucose and crocetin monogentiobiose ester accounted for 80% of the total production.

等^[19]经阴离子交换色谱以及凝胶过滤等多步分离纯化操作后，得到了部分纯化的UDP-葡萄糖-西红花酸8，8’-葡萄糖基转移酶，该酶催化葡萄糖与西红花酸之间酯键的形成，在40℃具有最大的酶活力。Dufresne et al ^[17] added crocetin to the suspension culture system of saffron bud callus, the cultured cells could absorb crocetin and convert it into crocin after glycosylation, and the product was stored in the vacuole . After 4 days of culture, the accumulation of the product reaches the maximum, calculated by dry weight, 9 mg of glycoside can be synthesized per gram of cells. The structures of the products were analyzed, and the most important ones were crocetin bistriose and crocetin monotriose-gentiobioside, which accounted for 60% of the total glycoside production. This result indicated that a variety of glycosyltransferases may be involved in the in vitro glycosylation of crocetin. Yuhongzeng ^[18] et al. used serine, sodium acetate, aminoacetic acid, and PVP as the medium to culture saffron stigmas, and increased the content of saffron glucoside from 2.21% to 6.00%. In the biosynthesis of crocetin glucoside, crocetin-1 is used as a substrate to form crocin-1 enzymatic reaction under in vitro conditions, and two different glycosyltransferases participate in the reaction. Researchers have been working on the separation and purification of these two enzymes.

^[19] obtained a partially purified UDP-glucose-crocetinic acid 8,8'-glucosyltransferase after multi-step separation and purification operations such as anion exchange chromatography and gel filtration. The formation of ester bonds between flower acids has the maximum enzyme activity at 40°C.

In the biosynthesis of crocetin glucoside, the focus of research is to carry out the biosynthesis method of crocetin glucoside as the substrate with crocetin, but the literature related to the biosynthesis method of crocetin is reported very much. Less, what is the substrate, and under the action of which enzymes, a larger amount of crocetin can be obtained. Chemists are also working on the chemical synthesis of conjugated polyene compounds such as crocetin and crocetin glucoside, because crocetin and crocetin glucoside belong to conjugated polyene compounds. At present, the chemical synthesis methods for conjugated polyene compounds are reported as follows:

1. Chemical synthesis method

1.1 Synthetic method of conjugated polyene compound

1) Witting synthesis method

Crocetin acid and crocetin glucoside are 20-carbon conjugated polyene compounds. In the synthesis of conjugated polyene compounds, the most famous reactions are Witting and Witting-Horner reactions. Most of the synthetic methods reported in the literature use the Witting reaction to synthesize the corresponding target products through different Witting salts and different aldehydes. F. Kienzle ^[20] reviewed the synthesis methods of different carotenoids in his article, in which the mechanism of Witting reaction was discussed, and the synthesis route of polyene compounds was summarized. Such as the industrial route for the synthesis of β-carotene.

2) Other synthetic methods

August RuHimann ^[21] reported the synthesis of conjugated polyene compounds by the condensation reaction of dienol ethers. In this reaction, Lewis acid (BF ₃ -diethyl ether complex, ZnCl ₂ , FeCl ₃ ) was used as a catalyst. Since the synthesis of conjugated polyene compounds by Witting reaction will produce cis-trans isomers, Fangxing Zeng ^[22] et al. proposed to use Zr-catalyst and pd-Zn catalyst to catalyze the synthesis of β-carotene, γ-carotene and retinoids. white. Concrete synthetic steps are as follows:

i) Me ₃ Al(2equiv), CpZrCl ₂ , CH ₂ Cl ₂ , 23°C, 4h;

ii) evaporation at 50℃ and <0.5mmHg;

iii) 2(1.05equiv), ZnCl ₂ (1equiv) in THF, 2.5mol% of Pd ₂ (dba), 10mol% of TFP[=tri(2-fury)phosphinel], DMF, 23°C, 6h;

iv) K ₂ CO ₃ , MeOH, 23°C, 3h;

v) 1(0.5equiv), ZnCl ₂ (1equiv)in THF, 2.5mol% of Pd ₂ (dba), 10mol% of TFP[=tri(2-fury)phosphinel], DMF, 23°C, 8h.

Although this reaction overcomes the phenomenon of cis-trans isomerism in the synthesis of conjugated polyene compounds, this reaction system uses a relatively expensive metal shrinkage agent, which makes the cost of the reaction too high. In addition, in the reaction It is more difficult to remove the metal during the post-processing of the metal.

According to the situation reported in the above article, there are mainly 4 methods for the synthesis of conjugated polyene chain compounds:

(1) Witting synthesis method: This method is easy to produce two kinds of isomers, cis and trans, but the yield of trans isomer is mostly and the yield is higher, so it is the most commonly used synthetic method.

(2) Dienol ether condensation method: This type of reaction produces more by-products, but if the conditions can be controlled, the ratio of by-products can be controlled within 10%, and this method can obtain trans-iso Construct.

(3) Grighard synthesis method: aldehydes and alkynes generate conjugated polyene compounds under the action of Grighard reagents, and this reaction also generates cis and trans isomers.

(4) Synthetic method of Zr catalyst catalyzing the alkenyl-alkenyl coupling reaction and Pd-Zn catalyst catalyzing the reaction of oligo-alkyne alkenyl and alkylaluminum. The conjugated polyene obtained by this method has only the cis-isomer, but the catalyst used in this method is relatively expensive, and the yield of the obtained product is not high according to the data reported in the literature.

The above four methods have their own advantages and disadvantages in the synthesis of conjugated polyene compounds. Different authors have adopted different synthesis methods according to their own needs, but most methods use the Witting synthesis method.

2) Synthesis of active ingredients of saffron

(1) Synthesis of crocetin

In the relevant literature ^[23,24] , the synthesis method of dimethyl crocetin was reported, and the main synthesis method is Witting reaction and dienol ether condensation reaction. Preparation of crocetin by dimethyl crocetin. It is also reported in the literature ^[25] to synthesize saffron dialdehyde and oxidize saffron dialdehyde to obtain crocetin acid.

2) Synthesis of saffron glucoside

According to the searched literature, there are few reports on the synthesis of glycosides. In the earliest synthesis of crocin glucoside ^[88] , acetyl bromoglucoside and α-acetylbromogentiobiose were reacted with crocetin acid to synthesize the acetyl compound of crocin glucoside, but in While the acetyl group was hydrolyzed, the ester bond of crocetin was also hydrolyzed. Therefore, the synthesis of crocetin glucoside was unsuccessful.

After Hanspeter Pfander changed the reaction conditions, he also used α-acetylbromoglucose to react with zeaxanthin to synthesize the acetylglucoside of zeaxanthin, but it had to be reacted for 20 days, and the reaction yield was very low. After obtaining acetyl glucoside, it is hydrolyzed under alkaline conditions to obtain the glucoside compound of zeaxanthin ^[26] . Subsequently, in order to avoid the above problems, Hanspeter Pfander ^[27] used crocetin as a raw material to synthesize crocetin diglucoside through a series of relatively new methods. The reaction is as follows: Hanspeter Pfander; Fritz Wittwer.Helvetica Chimica Acta 1979, 198, 1944-1951 reported the preparation process of saffron glucoside, including two steps:

1, the synthesis of imidazole crocetin

A mixture of 3 g (9 mmol) of crocetin and 5 g (31 mmol) of N,N-carbonyldiimidazole was put into 80 ml of DMF solution, and the temperature was kept at 20°C. A black precipitate was produced after the mixture was dissolved for a few minutes and reacted for 2 h. After 15 minutes without carbon dioxide release, raise the temperature to 50-90°C for several minutes. Evaporate 60-80ml of DMF, cool gradually until imidazole crocetin is precipitated, dissolve the residue in chloroform, wash with water, and dry over anhydrous magnesium sulfate. Obtain 3.55 g of imidazole crocetin, 92%.

2. Synthesis of saffron glucoside

Put 300mg (0.7mmol) of imidazole crocetin (0.7mmol), 500mg (2.75mmol) of glucose and NaH washed with petroleum ether into 40ml of dry pyridine solution, react at room temperature for 1h, a black suspended precipitate is formed, and the solution is dark red After 3 hours, add n-butanol phosphate buffer solution, adjust the pH value to 7, wait for the solution to be separated, wash the n-butanol layer with water, dry with anhydrous sodium sulfate, evaporate to dry n-butanol to obtain a crude product, dissolve in water, and centrifuge . Put the residue into 80% ethanol solution to precipitate crystals, wash the crystals with petroleum ether to remove non-polar by-products. 412 mg was obtained in a yield of 67%.

In the process of preparing imidazole crocetin, multi-step treatment of heating, extraction and distillation is carried out in the later stage, and DMF (dimethylformamide) is a colorless liquid with a light amine smell. Molecular formula C3-H7-N-O. Molecular weight 73.10. The relative density is 0.9445 (25°C). Melting point -61°C. The boiling point is 152.8°C. Vapor density 2.51. It can be miscible with water and organic solvents, and can cause combustion and explosion when exposed to open fire or high heat. It can react violently with concentrated sulfuric acid and fuming nitric acid and even explode. In mass production, the requirements for equipment are higher. The operation is troublesome, the reaction time is long (2h), the distillation reaction time is short, and it is difficult to control the reaction progress in large-scale production.

Richard R ^[28] etc. proposed a new method for the synthesis of glucoside of unstable phospholipids and glucoside of nucleic acids, and the reaction is as follows:

Although this method is used for the synthesis of glucoside of phospholipid glucoside nucleic acid, it provides a better idea, which can be used for the synthesis of saffron glucoside for reference.

In addition, the price of saffron glucoside is expensive, and the current price of commercially available saffron plants is: 5000-12000 yuan/kg (RMB), and the content of saffron glucoside in saffron plants is 3/10,000 To four, synthetic saffron glucoside has higher economic value, in large-scale production, every 1% yield of saffron glucoside increases, all can obtain significant progress commercially, therefore, more need a kind of operation The method is simple, easy to control, improves the yield and reduces the cost, and satisfies the demand of mass production.

Contents of the invention

The technical solution of the present invention is to provide a new synthetic method of saffron glucoside.

The invention provides the synthetic method of crocin glucoside, it comprises the steps:

a, synthesis C ₁₀ compound 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II);

B, synthesis C Compound E- _2- methyl-4-bromo-2-butenoic acid methyl ester;

C, take above-mentioned two kinds of compounds as raw material synthetic dimethyl crocetin;

d, hydrolyzing dimethyl crocetin to obtain crocetin;

e, using crocetin to react with carbonylimidazole to synthesize crocetin imidazole and then to synthesize crocetin glucoside.

Wherein, described 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II) synthetic method is:

a. Using E-1,4-di-bromo-2-butene and triethyl phosphite as starting reactants, apply Wittig-Horner reaction to synthesize E-2-butene-1,4-diphosphonic acid Diethyl ester (compound I), wherein the reaction conditions are nitrogen filling, the initial temperature is 110-130°C, and the final temperature is 170-190°C;

b, with compound I and acetone dialdehyde as starting material, nitrogen, in ice bath, add the THF solution of NaH, be 1: (3-4) with the material ratio of compound I and NaH; Compound I and acetone The material ratio of dimethylformal is 1:(2-5) for the reaction, the reaction temperature is controlled at 40-50° C., and the reaction is carried out for 1-1.5 hours to obtain compound II.

Further preferably, the material ratio of compound I to acetone dimethyl acetal is 1:5; the material ratio of compound II to alkali is 1:3.

Wherein, the synthetic method of described E-2-methyl-4-bromo-2-butenoic acid methyl ester:

a, with E-2-methyl-2-butenoic acid and NBS reagent as starting material, through free radical substitution reaction, synthesized E-2-methyl-4-bromo-2-butenoic acid, wherein E -The reaction mass ratio of 2-methyl-2-butenoic acid and NBS is 1:1, and the light is 1-1.5 hours;

b. In an ice bath, add thionyl dichloride dropwise to the methanol solution of E-2-methyl-4-bromo-2-butenoic acid to dissolve E-2-methyl-4-bromo-2-butene The reaction material ratio of acid to thionyl chloride is 1:1-2 for reaction, the temperature is controlled at 50-60°C, and 89-95% of E-2-methyl-2-butenoic acid is obtained after reflux reaction for 16 hours methyl ester.

Further preferably, in step b, the reaction material ratio of E-2-methyl-4-bromo-2-butenoic acid to thionyl chloride is 1:1.

Wherein, the synthetic method of described dimethyl crocetin:

According to the Wittig-horner reaction principle, E-2-methyl-4-bromo-2-butenoic acid methyl ester, triethyl phosphite and 2,7-dimethyl-2,4,6-octatriene -1,8-dialdehyde is the starting material, and after two-step reaction, E-2-methyl-2-butenoic acid methyl ester-4-phosphonic acid diethyl ester (compound III) is first synthesized, and then saffron is synthesized Dimethyl flowerate;

The reaction conditions of compound III are: filling with nitrogen, the initial temperature is 100-110°C, the end temperature is 160-180°C, and the temperature is maintained for 1.0-1.5 hours;

The condition of synthesizing dimethyl crocetin is: logical nitrogen, take NaH as alkali, THF as reaction solvent, 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde ( The reaction mass ratio of compound II), sodium hydride and E-2-methyl-2-butenoic acid methyl ester-4-phosphonic acid diethyl ester (compound III) is 1: 3: 2.5, and reacts in ice bath for 0.5 -1.0 hours.

Wherein, the synthetic method of described crocetin is:

The synthesis experiment of crocetin was carried out by the method of alkaline hydrolysis: with DMF as solvent and potassium hydroxide aqueous solution as alkali, the potassium salt of crocetin can be obtained after heating dimethyl crocetin to reflux for 1 hour After acidification, crocetin is obtained.

Wherein, the synthetic method of described saffron glucoside is:

Crocetin imidazole was synthesized by reacting crocetin with carbonylimidazole and then crocetin glucoside was synthesized. Under the protection of stirring nitrogen, crocetin and N,N-carbonyldiimidazole, the material ratio is: 1:2-12, react in DMSO solvent for 1-2 hours, filter the reaction solution, wash with ether or petroleum ether Filter cake removes DMSO, 35 ℃ vacuum drying obtains compound imidazole crocetin;

Under the protection of nitrogen, imidazole crocetin and glucose, material ratio: 1:3-7, dissolved in pyridine, then added NaH, stirred and reacted for 1-3 hours, filtered the reaction solution to remove generated NaOH and excess NaH , extracted three times with n-butanol, combined the n-butanol layers, washed the n-butanol layer with water three times, evaporated the n-butanol to dryness, and purified the saffron glucoside by reverse-phase _C18 column chromatography.

Further preferably, the material ratio of said crocetin to N,N-carbonyldiimidazole is 1:10; the theoretical material ratio of said crocetin imidazole to glucose is 1:5; The material ratio of imidazole to NaH is 1:8.

Through the measurement and analysis of ¹ HNMR spectrum, ¹³ CNMR spectrum, UV spectrum and FT-IR spectrum, 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde, E- Structures of methyl 2-methyl-2-butenoate, dimethyl crocetin, crocetin, imidazole crocetin, and crocetin glucoside, thus demonstrating the feasibility of the designed synthetic route .

Detailed ways

Embodiment 1 2,7-dimethyl-2,4,6-octatriene-1, the synthesis of 8-dialdehyde (compound II)

2,7-Dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II) has a very important position in the synthesis of conjugated polyene compounds. Through this compound, many Carotenoids (such as vitamin A, etc.) compounds ^[29-31] . In the synthesis of conjugated polyene compounds, the Wittig synthesis method is a very important synthetic method, and many conjugated polyene compounds are synthesized using this method ^[32-35] .

In existing literature, 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II is synthesized with 1,4-butadiene or furan as starting However, the product obtained by the Wittig synthesis method is not easy to purify and the overall yield is not high ^[36-38] . The product obtained by the Wittig-Horner synthesis method is easily soluble In water, it is easy to purify the main product. Therefore, on the basis of the synthetic method provided in the above documents, with E-1,4-bis-bromo-2-butene and triethyl phosphite as starting reactants, by Wittig-Horner reaction, synthetic compound II, synthetic route is:

1. Experimental part

1.1 Instruments and reagents

1.1.1 Instruments

Nicolt 560 Fourier transform infrared spectrometer;

Spectrum Analysis TU-1901 UV-Visible Spectrophotometer;

VG7070E mass spectrometer;

Varian ANOVA-400 nuclear magnetic resonance instrument;

Carlo Erba 1106 elemental analyzer;

YRT-3 melting point apparatus (Tianjin University Precision Instrument Factory);

TLC silica gel GF ₂₅₄ thin-layer plate 3×10cm (Qingdao Meijing Chemical Co., Ltd.);

Silica gel chromatography column (self-made)

1.1.2 Reagents

All reagents were analytically or chemically pure and were not further processed unless otherwise noted.

Anhydrous benzene: Add sodium metal and reflux until the benzophenone turns blue, then seal and collect. Anhydrous THF: Add sodium metal and reflux until the benzophenone turns blue, then seal and collect. Triethyl phosphite: Distill under reduced pressure, collect the fraction at 76-80°C in a dry container, and store at low temperature. Anhydrous DMF: Re-distill, collect the fraction at 152-154°C in a dry container equipped with 4# molecular sieve, and store in the dark. E-1,4-dibromo-2-butene: American ACROS company. Anhydrous Magnesium Sulfate: Calcined at 480°C for 4 hours in a horse-radiated furnace, cooled, and stored in a dry place. NaH 60%, preserved in mineral oil

Synthesis experiment of 1.2E-2-butene-1,4-diethyl diphosphonate (compound I)

The equation of this step reaction is as follows:

In a three-necked flask equipped with a dropping funnel, a vacuum distillation device and a thermometer, under nitrogen flow, heat excess triethyl phosphite to 110°C, stir, and dissolve 0.1molE with a certain amount of anhydrous benzene -1,4-di-bromo-2-butene was dissolved and added dropwise to a three-necked flask. After bromoethane is distilled off, the temperature is raised to 170-190°C and maintained for 1.0-1.5 hours. During the reaction process, the change of E-1,4-dibromo-2-butene was monitored with a silica gel thin-layer plate. After the reaction was complete, the heating was stopped, and the low boiling point substances were distilled out, and the remaining compounds were cooled to room temperature to obtain 2- Butene-1,4-diethyl phosphonate (compound I), this compound is viscous light brown liquid.

When 8.578 g of E-1,4-dibromo-2-butene was fed, 13.046 g of crude compound I was obtained under the above reaction conditions, with a yield of 99.18%. When 21.39 g of E-1,4-dibromo-2-butene was fed, 31.782 g of crude compound I was obtained, and the yield was 96.9%.

Therefore, the yield of this step reaction compound I is more than 95%.

1.3 Synthesis experiment of 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde (compound II)

The equation of this step reaction is as follows:

Place the three-necked flask in an ice bath, ventilate with nitrogen, add 0.3 mol of 60% sodium hydride, then add a certain amount of anhydrous THF, stir, and dropwise add 0.5 mol of acetone dimethyl acetal and 0.1 mol of compound I. After the dropwise addition is completed, keep the reaction at 50-60°C for 1-1.5 hours. Monitor compound I with a thin-layer silica gel plate. After the reaction is completed, acidify and add water. After a few minutes, a large number of yellow solids are precipitated from the orange-brown liquid. Get crude products. The aqueous phase of the reaction system was extracted with ether, and the ether phases were combined. The ether layer was washed with saturated brine, dried over anhydrous magnesium sulfate, ether was removed, and the solids were combined in the crude product. The crude product was recrystallized in diethyl ether to obtain a light yellow long needle-like solid. The recrystallized mother liquor was separated on a silica gel chromatography column, the light yellow color band was collected, and the eluent was removed by rotary evaporation, and the obtained light yellow solid was combined with the recrystallized solid to obtain compound II. The yield is 95.31%.

2. Results and discussion

2.1 Selection of compound I synthesis conditions

2.1.1.1 Selection of material ratio of reactants

According to the synthesis method of reference ^[36] , the method of the present invention carried out the synthesis experiment of compound I. Since triethyl phosphite is liquid, it can be used as both a reactant and a solvent in the reaction, so in the experiment, excessive triethyl phosphite will make E-1,4-dibromo-2 -Butene reacts completely.

2.1.1.2 Selection of reaction temperature

According to previous work ^[36] , the temperature of this step should be controlled above 110°C. After the bromoethane is distilled off, the reaction temperature should be 170-190°C. If it is lower than this temperature range, the reaction cannot be carried out completely, and there will be more reaction points on the TLC plate. If the reaction temperature exceeds 200°C, the reactant will easily gelatinize.

2.1.1.3 Selection of purification conditions for compound I

After monitoring the complete reaction of E-1,4-dibromo-2-butene, distill under reduced pressure to remove excess triethyl phosphite and other low-boiling impurities. According to literature ^[36] , the purified compound I was obtained by rectification at 162-168°C in high vacuum (1mm). However, since there is no high vacuum pump in this laboratory, the high vacuum degree of 1 mm cannot be achieved, and compound I cannot be purified. We considered separating Compound I by column chromatography to achieve the purpose of purification. However, due to the strong polarity of compound I, severe tailing occurs on the silica gel column. Although different eluents were used, the tailing could not be resolved, resulting in a low yield of compound I. Therefore, after the reaction is finished, the impurities with low boiling point are distilled off under reduced pressure as much as possible.

2.2 Selection of synthetic conditions for compound II

2.2.1 Selection of material ratio of reactants

Theoretically, the reaction material ratio of compound I to acetone dimethyl acetal is 1:2. In the experiment, the reaction material ratio of compound I and acetone dimethyl acetal was designed to be 1:2; 1:3; 1:4; 1:5. According to the results of the TLC thin-layer plate experiment, when the material ratio of the reactants is 1:5, the compound I reacts completely. Therefore, the material ratio of this step reaction is 1:5.

2.2.2 Alkali selection

Since the synthesis principle of compound II is the Wittig-Horner reaction, the reaction process is shown in the figure below.

From the perspective of the reaction process, the hydrogen on the α position of the compound I is taken away under strong basic conditions to become a carbanion, which then reacts with the aldehyde to form a polyene bond. According to the reference, sodium methoxide was used as the base for the reaction in the experiment, but the yield of compound II obtained was very low. Analyzing the reason, it is considered that the basicity is not strong enough to completely remove the hydrogen on the α position of compound I to form a carbanion well. In the experiment, the yield of compound II was increased by increasing the concentration of sodium methoxide, but the experimental results were not ideal, and the yield of compound II obtained was only 32.8%. After sodium methoxide was changed into sodium hydride, good results were obtained. At the same time, different material ratios of sodium hydride and compound I were selected for experiments. The experimental results are shown in Table 1.

Table 1 The influence of alkali on the yield of compound II

As can be seen from the results in the table, as the strength of the base increases, the yield of compound II is increasing. At the same time, sodium hydride is more alkaline than sodium methoxide, leading to an increase in the yield of the product. Along with the material ratio of sodium hydride and compound I increases, the yield of compound II improves greatly. But when the material ratio of sodium hydride to compound I reaches 3:1, the yield of compound II does not change much. Therefore, select sodium hydride to be the base of this step reaction, and the material ratio of sodium hydride and compound I is 3:1.

2.2.3 Selection of reaction temperature and time

Because NaH is a very strong base, therefore, before the completion of the NaH reaction, the reaction was carried out in an ice bath. After the completion of the NaH reaction, at different temperatures, TLC was followed to monitor the reaction of Compound I. The results showed that when the temperature was at 40-50° C., the compound I reacted completely for 1-1.5 hours. Below this temperature range, compound I does not react completely. Therefore, in the experiment, when the reaction temperature is 40-50° C. and the reaction time is 1-1.5 hours, the reaction conditions are selected.

2.2.4 Selection of reaction solvent

In the experiment, DMF was used as the solvent for the reaction. But the yield of compound II is not ideal. In order to further increase the yield of compound II and facilitate the post-treatment of the reaction, anhydrous THF was selected as the solvent for the reaction by analyzing the properties of various solvents. As a result, anhydrous THF increased the yield of compound II to 95.31%. The experimental results are shown in Table 2.

Table 2 The influence of solvent on the yield of compound II

Embodiment 2 The synthesis of E-2-methyl-4-bromo-2-butenoic acid methyl ester

In the existing synthetic method ^[39] , the synthesis of E-2-methyl-4-halo-2-butenoic acid ester is based on α-vinyl propionate as raw material, through the addition of halogen to form 3, 4-dihalopropionate, and then remove a molecule of hydrogen halide to form E-2-methyl-4-halo-2-butenoate. Its reaction process is:

There is no report on the synthesis of E-2-methyl-4-bromo-2-butenoic acid methyl ester from E-2-methyl-2-butenoic acid in the existing literature. Since E-2-methyl-2-butenoic acid is a C5-type compound, which meets the design requirements, this compound is used as a raw material to first synthesize E-2-methyl-4-bromo-2-butenoic acid, and then synthesize E - Methyl 2-methyl-4-bromo-2-butenoate. The synthetic route is:

1. Experimental part

1.1 Instruments and reagents

1.1.1 Instruments

Varian ANOVA-400 nuclear magnetic resonance instrument;

TLC silica gel GF254 thin layer plate 3 × 10cm (Qingdao Meijing Chemical Co., Ltd.).

1.1.2 Reagents

Anhydrous thionyl chloride: redistill thionyl chloride under atmospheric pressure, and collect the fraction with a b.p. of 76°C. E-2-methyl-2-butenoic acid: American ACROS company. NBS Chengdu Kelong Chemical Company. Anhydrous methanol: redistill, collect the fraction at 68°C in a dry 4# molecular sieve container, and store in the dark.

All reagents were analytically or chemically pure and were not further processed unless otherwise noted.

2.2 Synthesis experiment of 2E-2-methyl-4-bromo-2-butenoic acid

In a round bottom flask equipped with a reflux condensing device, place 10.349g of E-2-methyl-2-butenoic acid and 18.434g of NBS reagent, a small amount of benzoyl peroxide and a certain amount of carbon tetrachloride solution, Stir and react with light for 1-1.5 hours, and track the reaction progress with a silica gel plate. After the reaction of E-2-methyl-2-butenoic acid is complete, cool, filter, and remove carbon tetrachloride by rotary evaporation of the filtrate. The residue precipitated as a white solid in the refrigerator. Filtrate, add petroleum ether to the mother liquor, continue to precipitate white solids, repeat this process until no white solids precipitate. The products were combined and dried in vacuo to obtain 10.35 g of solid product E-2-methyl-4-bromo-2-butenoic acid. The remaining mother liquor was rotary evaporated to remove petroleum ether into light yellow viscous oil, impurities were removed, and the viscous oil was vacuum-dried and weighed 8.129g.

The yield of E-2-methyl-4-bromo-2-butenoic acid white solid obtained in the experiment was 55.89%. The viscous oil was monitored by a silica gel plate as E-2-methyl-4-bromo-2-butenoic acid, and the yield of this part was 43.89%. Therefore, the yield of this step reaction is 99.78%.

2.3 Synthesis experiment of 2-methyl-4-bromo-2-butenoic acid methyl ester

Put 3.611g of E-2-methyl-4-bromo-2-butenoic acid in a round-bottomed flask equipped with a dropping funnel, add excess anhydrous methanol, stir at low temperature, and drop dichloro Sulfoxide 3ml. After the dropwise addition, heat to reflux to react for 16 hours, and track the reaction process with a silica gel plate. When the reaction of E-2-methyl-4-bromo-2-butenoic acid is complete, add aqueous sodium bicarbonate until the solution is alkaline. The aqueous phase was extracted with dichloromethane, the dichloromethane extracts were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, the dichloromethane was removed by rotary evaporation, and the product E-2-methyl-4-bromo- Methyl 2-butenoate 3.476 g.

In the experiment, react with different amounts of E-2-methyl-4-bromo-2-butenoic acid to calculate the synthesis yield of E-2-methyl-4-bromo-2-butenoic acid methyl ester . From the experimental results, the yield of E-2-methyl-4-bromo-2-butenoic acid methyl ester is 89-95%.

2. Results and discussion

2.2.1 Selection of synthetic conditions for E-2-methyl-4-bromo-2-butenoic acid

2.2.1.1 Material ratio selection of reactants

The synthesis of E-2-methyl-4-bromo-2-butenoic acid is based on the principle of free radical substitution reaction ^[5] . Under the reaction conditions of peroxide and light, NBS first homogeneously splits to generate free radicals, triggers free radical substitution reactions, and continuously provides a source of bromine. Its reaction course is:

This step reaction has not been reported in any literature and is the key step reaction of the experiment. Since there are two allylic methyl hydrogens in the molecule of E-2-methyl-2-butenoic acid, according to the above-mentioned reaction principle, there are two reaction points in the reaction. The desired product for the experiment was E-2-methyl-4-bromo-2-butenoic acid, not E-2-bromomethyl-2-butenoic acid. As follows:

From the molecular structure analysis, the propylene hydrogen on the 3-position methyl carbon is easier to lose than the 2-position carbon, and the formed free radical is more stable. Therefore, the radical substitution reaction occurs first at the 3-position carbon. However, if NBS is excessive, a reaction in which the hydrogen on the 2-methyl carbon is replaced may occur. In order to avoid the production of E-2-bromomethyl-2-butenoic acid, with reference to related work ^[40-42] , the material ratio of E-2-methyl-2-butenoic acid and NBS is selected at 1: 1. Obtained better experimental result thus, there is no E-2-bromomethyl-2-butenoic acid in the reaction product.

2.2.1.2 Selection of other reaction conditions

The substitution reaction due to free radicals needs light or heating and can be carried out in the presence of free radical initiators. Through experimental comparison, the reaction can be completed in 1-1.5 hours under the condition of light, using benzoyl peroxide as the initiator. Therefore, the selected reaction condition is light, and the time is 1-1.5 hours.

2.2.2 Selection of synthetic conditions for E-2-methyl-4-bromo-2-butenoic acid methyl ester

2.2.2.1 Selection of reactant material ratio

The method of the present invention uses the reaction process of acid and alcohol to generate ester under the action of thionyl chloride to carry out the synthesis experiment of E-2-methyl-4-bromo-2-butenoic acid methyl ester. Its course is:

This type of esterification overcomes the disadvantage of using acid or base as catalyst, and the yield is higher. Methanol is in a liquid state, and it can be used as both a reactant and a solvent in the reaction, so in the experiment, excess methanol is used to complete the reaction of E-2-methyl-4-bromo-2-butenoic acid. From the monitoring situation of the silica gel plate, the reaction was carried out very completely.

In the experiment, the material ratio of E-2-methyl-4-bromo-2-butenoic acid and thionyl chloride was investigated. From the above reaction history, the theoretical reaction material ratio of the two is 1:1. According to this, the reaction mass ratio of the two is 1: 1 and 1: 2 to carry out experiments. From the monitoring situation of the silica gel plate, when thionyl chloride is excessive, E-2-methyl-4-bromo-2- The reaction of crotonic acid is complete, therefore, the material ratio of E-2-methyl-4-bromo-2-butenoic acid and thionyl chloride is selected as 1:2.

2.2.2.2 Control of reaction temperature and reaction time

Since the heat release during the dropwise addition of thionyl chloride is very violent, the temperature during the dropwise addition of thionyl chloride is controlled at a low temperature. After the dropwise addition of thionyl chloride is complete, the temperature rises to 25°C. Monitor the progress of the reaction with a silica gel plate. After 40 hours, the reaction is complete, but the time consumed is too long. In order to shorten the reaction time, heating is carried out. When the temperature is 50-60 ° C, the reaction is 16 hours, E-2-formazan The 4-bromo-2-butenoic acid was completely reacted.

2.2.3 Selection of synthetic routes of E-2-methyl-4-bromo-2-butenoic acid methyl ester

In the experiment, the two-step reaction of the above synthetic route was reversed, hoping to obtain a better yield. That is to do the esterification reaction first, and then the bromination reaction. The synthetic route is:

The experimental results show that the yield of the esterification reaction is 69.04%, and the yield of the bromination reaction is 61.59%. Find out from experimental result, the yield of latter synthetic route is low with former one, especially the yield of the esterification reaction of latter synthetic route is much lower than former synthetic method. Analyzing the reason, it may be because the bromination first, after the formation of bromoacid, the polarity of the molecule is increased, the proton of the acid is easier to leave, it is easy to form a transition state in the esterification reaction process, and then it is easy to generate acid chloride, lead to the smooth progress of the esterification reaction. Therefore, the synthesis route of bromination first and esterification later was chosen in the experiment.

Embodiment 3 The synthesis of dimethyl crocetin (compound IV)

Dimethyl crocetin has a _C20 skeleton structure, and since dimethyl crocetin contains 7 double bonds, it belongs to polyene compounds. On the basis of referring to other literature ^[43-45] , this synthesis experiment intends to use 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde as the C ₁₀ compound, E-2 -Methyl-4-bromo-2-butenoic acid methyl ester is a C ₅ compound. Using the Wittig-Horner reaction principle, the synthesis of dimethyl crocetin was carried out. The experimental design scheme is:

1. Experimental part

1.1 Instruments and reagents

All instruments are the same as in the second part.

1.2E-2-methyl-2-butenoic acid methyl ester-4-phosphonic acid diethyl ester (compound III) synthesis experiment

The equation of this step reaction is as follows

In a three-necked flask equipped with a dropping funnel, a vacuum distillation device and a thermometer. Under nitrogen flow, heat excess triethyl phosphite to 100-110°C, stir, add dropwise a small amount of benzene solution of 0.1mol E-2-methyl-4-bromo-2-butenoic acid methyl ester to tri In the neck flask, after the ethyl bromide evaporates, raise the temperature to 160-170°C and keep it for 1-1.5 hours. During the reaction process, monitor the change of E-2-methyl-4-bromo-2-butenoic acid methyl ester with a silica gel thin-layer plate. After the reaction is complete, stop heating, and distill the low-boiling point substances under reduced pressure, and the remaining compounds are cooled to At room temperature, E-2-methyl-2-butenoic acid methyl ester-4-phosphonic acid diethyl ester (compound III) was obtained as a viscous light brown liquid.

When 2.81 g of E-2-methyl-4-bromo-2-butenoic acid methyl ester was fed, under the above reaction conditions, 3.633 g of crude compound III was obtained, with a yield of 95.53%.

1.3 Synthesis of dimethyl crocetin (compound IV)

The equation of this step reaction is as follows:

Place the three-necked flask in an ice bath, blow nitrogen, add 0.3mol 60% sodium hydride, then add a certain amount of anhydrous tetrahydrofuran solvent, and add dropwise 0.1mol of compound II in anhydrous tetrahydrofuran solution and 0.25mol of compound A solution of III in anhydrous tetrahydrofuran. Maintain the reaction for 0.5-1.0 hours. After the reaction is completed, acidify and add a large amount of water. After a few minutes, a large amount of dark red solid is precipitated from the black red liquid, and the crude product is obtained by filtration. The aqueous phase of the reaction system was extracted with dichloromethane, and the dichloromethane phases were combined. The dichloromethane layer was washed with saturated brine, dried over anhydrous magnesium sulfate, dichloromethane was removed, and the solid was combined into the crude product. The crude product was recrystallized in dichloromethane to obtain a dark red flaky solid. The recrystallized mother liquor was separated on a silica gel chromatography column, the first dark yellow color band was collected, and the eluent was removed by rotary evaporation, and the obtained dark red solid was combined with the recrystallized solid to obtain dimethyl crocetin.

2. Results and discussion

2.1 Selection of compound III synthesis conditions

2.1.1 Selection of material ratio of reactants

According to the synthesis method of reference ^[46] , the method of the present invention carried out the synthesis experiment of compound III. Since triethyl phosphite is liquid, it can be used as a reactant and as a solvent in the reaction, so in the experiment, excessive triethyl phosphite will make E-2-methyl-4-bromo -Methyl 2-butenoate reacted completely.

2.1.2 Reaction temperature

According to previous work ^[46] , the temperature of this step should be controlled above 100°C. After bromoethane is distilled off, the temperature is maintained at 160-180°C. If it is lower than this temperature range, the reaction cannot be carried out completely, and there are many reaction spots on the TLC plate.

2.1.3 Selection of purification conditions for compound III

After monitoring the complete reaction of E-2-methyl-4-bromo-2-butenoic acid methyl ester, distill under reduced pressure to remove excess triethyl phosphite and other low-boiling impurities. As in the case of compound I, compound III has strong polarity, which causes serious tailing phenomenon on the silica gel column. Although different eluents were used, the tailing could not be resolved, resulting in a very low yield of compound III after column separation and purification. And because there is no high vacuum pump, compound III cannot be purified by distillation. Therefore, after the reaction is finished, the impurities with low boiling point are distilled off under reduced pressure as much as possible.

2.2 Selection of synthesis conditions for dimethyl crocetin

2.2.1 Selection of base and solvent

Referring to the synthesis method of 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde, in the experiment, sodium methoxide and sodium hydride were selected as bases, and DMF and THF were used as solvents for the reaction . The experimental results are shown in Table 3.

Table 3 The influence of solvent and alkali on the yield of dimethyl crocetin (compound IV)

It can be seen from the above table that using THF as the solvent and NaH as the base for the reaction can achieve better results. This is similar to the synthesis conditions of 2,7-dimethyl-2,4,6-octatriene-1,8-dialdehyde.

Therefore, in the experiment, THF was selected as the solvent and NaH was used as the base for the reaction.

2.2.2 Selection of material ratio of reactants

Theoretically, E-2-methyl-2-butenoic acid methyl ester-4-diethyl phosphonate (compound III), sodium hydride and 2,7-dimethyl-2,4,6-octatriene -1,8-dialdehyde (compound II) has a reaction mass ratio of 2:2:1. In the experiment, the reaction material ratio of compound III and compound II was designed to be 2:1; 2.5:1; 3:1. According to the results of TLC thin-layer plate experiments, when the material ratio of compound III and compound II is 2.5:1, the reaction between the two is complete. At the same time, the reaction material ratio of compound II and sodium hydride designed in the experiment is 1:2; 1:3; 1:4. When the ratio is 1:3, the reaction of compound III and compound II is complete.

Finally, it is determined that the reaction material ratio of compound II, sodium hydride and compound III is 1:3:2.5.

2.2.3 Selection of reaction temperature and time

Since NaH is a very strong base, the reaction was carried out in an ice bath to generate a product, and the reaction was monitored on a silica gel plate. After 1-1.5 hours, compound III and compound II reacted completely. Therefore, in the experiment, the conditions of reaction in ice bath for 1-1.5 hours were selected to carry out the synthesis experiment of saffron dimethyl ester.

3. The yield of dimethyl crocetin

The yield of dimethyl crocetin in this step reaction is 70.2%. Judging from the dot plate situation of the reaction, there are other yellow compounds appearing. According to relevant literature reports ^[47,48] , this step reaction is prone to cis-trans isomerism, and the ratio of anti-cis isomerization (E/Z) is 5:1-7:1. Therefore, the additional yellow spot may be the cis isomer of dimethyl crocetin. In future experiments, how to reduce the ratio of cis-trans isomerization and increase the yield of trans-isomerization still needs to be further explored.

Embodiment 4 The synthesis of crocetin

In the synthesis of this step, the reaction in this step is carried out according to the principle that ester compounds can be hydrolyzed into acids under the action of acid or base ^[49-51] . The synthetic route is

1. Experimental part

1.1 Instruments and reagents

Finnigen LCQ-DECA mass spectrometer, other instruments are the same as the second part.

All reagents were of analytical grade and were not further processed unless otherwise noted.

1.2 Synthesis experiment of crocetin

In a three-necked flask, add a certain amount of dimethyl crocetin, dissolve the dimethyl crocetin with DMF, add KOH aqueous solution, and heat to reflux for 1 hour. Spot the plate, all dimethyl crocetin is hydrolyzed, acidified, and filtered to obtain the product.

2. Results and discussion

2.1 The choice of acid-base hydrolysis

In the experiment, acid hydrolysis and alkali hydrolysis were carried out with hydrochloric acid and sodium hydroxide. When hydrolyzing with acid, the dimethyl crocetin was not hydrolyzed after 48 hours of reaction. When alkali is used, dimethyl crocetin can be hydrolyzed in 1 hour. Therefore, the hydrolysis reaction with alkali was chosen in the experiment.

2.2 Alkali selection

In the experiment, two alkalis, sodium hydroxide and potassium hydroxide, were designed to carry out the hydrolysis reaction. From the experimental results, when sodium hydroxide was used for hydrolysis, the reaction required time was 16 hours; when potassium hydroxide was used for hydrolysis, the reaction required time was 1 hour. Therefore, potassium hydroxide was chosen as the base for the hydrolysis reaction.

2.3 Selection of solvent

In the experiment, since dimethyl crocetin is only soluble in less polar organic solvents or DMF, it has very poor solubility in more polar solvents, and the hydrolysis reaction needs to be carried out in aqueous solution. In order to carry out the homogeneous reaction, DMF and a small amount of dichloromethane+methanol were designed for the reaction. Experiments show that when a small amount of dichloromethane+methanol is used as a solvent, after adding potassium hydroxide aqueous solution, it is very easy to separate layers so that the hydrolysis reaction still has dimethyl crocetin that has not been hydrolyzed after 48 hours. However, when DMF is used as a solvent, the reaction proceeds very quickly. After one hour, the spot plate dimethyl crocetin reacts completely, and the hydrolysis reaction proceeds very completely. Therefore, the experiment confirmed that DMF was used as the solvent for the reaction.

Embodiment 5 The synthesis of saffron glucoside

In the experimental design, referring to previous work ^[52-54] , we designed to react crocetin with N,N-carbonyldiimidazole to generate imidazole crocetin, which was further reacted with glucose to form Synthetic route of saffron glucoside. Its reaction process is:

1. Experimental part

1. Instruments and reagents

1.1 Instrument

Varian ANOVA-400 nuclear magnetic resonance instrument;

TLC silica gel GF254 thin layer plate 3 × 10cm (Qingdao Meijing Chemical Co., Ltd.).

1.2 Reagents

All reagents were analytically or chemically pure and were not further processed unless otherwise noted.

Dimethyl sulfoxide: Anhydrous magnesium sulfate drying N, N-carbonyldiimidazole: Chengdu Kelong Chemicals Company. Ether Chengdu Kelong Chemicals Company. Pyridine: Anhydrous magnesium sulfate drying Butanol Chengdu Kelong Chemicals Company. Methanol Chengdu Kelong Chemicals Company.

2. Synthetic experiment of imidazole crocetin

References ^[55-57] 240 mg of crocetin and 1200 mg of N, N-carbonyldiimidazole were dissolved in 5 mL of DMSO under nitrogen protection, and the reaction progress was monitored by TLC. After 1.5 hours, the reaction was complete, and a large amount of brown-black solid was formed. The reaction solution was filtered, and the filter cake was washed with diethyl ether or petroleum ether to remove DMSO. Vacuum drying at 35°C for 6 hours gave 300 mg of crocetin carbonylimidazole with a yield of 95.8%.

3. Synthesis experiment of saffron glucoside

References ^{[52, 54, 56] Dissolve} 90 mg of imidazole crocetin and 180 mg of glucose in 15 mL of pyridine under nitrogen protection, then add 40 mg of NaH and stir the reaction at room temperature, and monitor the progress of the reaction by TLC. After 2 hours, the reaction was basically complete, the reaction was stopped, and the reaction solution was filtered to remove the generated NaOH and excess NaH. Concentrate the filtrate and add 20mL of water. After the product is completely dissolved, extract it three times with 10mL of n-butanol, combine the n-butanol layer, wash the n-butanol layer with 8mL of water for three times, evaporate the n-butanol to dryness, and purify by reverse-phase C18 chromatography. [V(H ₂ O):V(MeOH)=1:1]. 97 mg of saffron glucoside was obtained with a yield of 70.8%.

4. Results and discussion

4.1 Selection of synthesis conditions of imidazole crocetin

4.1.1 Material ratio selection of reactants

Since the theoretical material ratio of crocetin and N, N-carbonyldiimidazole is 1: 2, it is 1: 2 to start to select the material ratio in the synthesis process, but there is a large amount of crocetin unreacted from monitoring on TLC completely. The material ratio of crocetin and N, N-carbonyldiimidazole is designed to be 1: 2; 1: 4; 1: 6; 1: 8; 1: 7; 1: 10; reaction. When the material ratio is 1:10, the reaction of crocetin is complete and the yield is relatively high, and finally the reaction material ratio is determined to be 1:10. The experimental results are shown in Table 4.

Table 4 The effect of material ratio on the yield of crocetin dicarbonylimidazole

4.1.2 Selection of other reaction conditions

The reaction process must be under the protection of nitrogen, and the reaction time should not exceed 2 hours; after the reaction uses DMSO suction filtration, there is still residue that is not easy to dry, so the filter cake should be fully washed with ether during suction filtration.

4.2 Selection of Synthetic Conditions for Crocin Glucoside

4.2.1 Selection of reactant material ratio

In the reaction process, the theoretical material ratio of imidazole crocetin and glucose is 1: 2, and the material ratio of imidazole crocetin and glucose is designed to be 1: 3 under other conditions; 1: 4; 1: 5; 1: 6 ; 1:7 for the reaction. When the material ratio is 1:5, the reaction of crocetin is complete and the yield is relatively high, and the final determination of the reaction material ratio is 1:5. The reaction process must be reacted under the protection of nitrogen, and the material ratio of imidazole crocetin to NaH is about 1:8 and the reaction is complete. The experimental results are shown in Table 5.

Table 5 The influence of material ratio on the yield of crocetin glucoside

4.2.2 Control of reaction temperature and reaction time

The reaction temperature is controlled at 20°C to 30°C; the reaction time is about two hours, and the reaction time should not be too long in order to avoid excessive side reactions because it is in a strong alkali environment.

5. Summary

In reference ^[52] , H.Pfander and F.Wittwer et al. have synthesized crocin glucoside by using imidazole crocetin as an intermediate, and the method of the present invention is improved and innovated on the basis of it, so that the process is simplified and easy to control. For example, when synthesizing imidazole crocetin, the synthetic method of the present invention does not carry out post-stage heating, extraction, and distillation treatment, but only through filtration and washing treatment, which eliminates the distillation dimethyl sulfoxide (DMSO) process, simplifies operation , and dimethyl sulfoxide Sulfoxide is a transparent, colorless, odorless, slightly bitter liquid with extremely low toxicity and stable properties, and is easy to operate in large-scale industrial production. The yield of 95.8% is higher than 92% of literature.

When synthesizing saffron glucoside, the post-treatment uses filtration to remove the NaOH and excess NaH generated by the reaction. Concentrate the filtrate and add 20mL of water. After the product is completely dissolved, extract it three times with 10mL of n-butanol, combine the n-butanol layer, wash the n-butanol layer with 8mL of water for three times, evaporate the n-butanol to dryness, and purify by reverse-phase C18 chromatography. , the yield was 70.8%, slightly higher than the 67% in literature ^[52] . The total yield of the two-step reaction method of the present invention is 67.8%, and the total yield of the literature ^[52] is 61.64%. The yield of the method of the present invention is higher than that reported in the literature.

In summary, the synthesis process of the present invention has advantages in terms of simplification of operation and yield, and the synthesized saffron glucoside has high purity and high yield; while increasing the yield, the cost is reduced, and significant progress has been made commercially , has strong industrial applicability.

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Claims (6)

1, the synthetic method of crocin glucoside, it comprises the steps:

A, synthetic C ₁₀Compound 2,7-dimethyl-2,4,6-sarohornene-1,8-dialdehyde (Compound I I):

1) with E-1,4-two-bromo-2-butylene and triethyl-phosphite are initial reactant, use the Wittig-Horner reaction, synthetic E-2-butene-1,4-di 2 ethylhexyl phosphonic acid diethyl ester (Compound I), wherein, reaction conditions is an inflated with nitrogen, and starting temperature 110-130 ℃, outlet temperature is 170-190 ℃;

2) be initiator with Compound I and the acetone dialdehyde that contracts, logical nitrogen in ice bath, adds the THF solution of NaH, is 1 with the material ratio of Compound I and NaH: (3-4); The contract material ratio of dicarbaldehyde of Compound I and acetone is 1: (2-5) react, temperature of reaction is controlled at 40-50 ℃, reacts 1-1.5 hour, obtains Compound I I;

B, synthetic C ₅Compd E-2-methyl-4-bromo-2-butylene acid methyl esters:

1) be initiator with acid of E-2-methyl-2-butene and NBS reagent, by the free radical substitution reaction, synthesized E-2-methyl-4-bromo-2-butylene acid, wherein the reacting material ratio of acid of E-2-methyl-2-butene and NBS is 1: 1, illumination 1-1.5 hour;

2) in ice bath, methanol solution to E-2-methyl-4-bromo-2-butylene acid drips thionyl chloride, is 1 with E-2-methyl-4-bromo-2-butylene acid with the reacting material ratio of thionyl chloride: (1-2) react, temperature is controlled at 50-60 ℃, and back flow reaction obtains the E-2-methyl-2-butene acid methyl esters of 89-95% after 16 hours;

C, be the synthetic crocetin dimethyl ester of raw material with above-mentioned two kinds of compounds:

According to the Wittig-Horner reaction principle, with E-2-methyl-4-bromo-2-butylene acid methyl esters, triethyl-phosphite and 2,7-dimethyl-2,4,6-sarohornene-1, the 8-dialdehyde is an initiator, through two-step reaction, and synthetic E-2-methyl-2-butene acid methyl esters-4-diethyl phosphonate (compound III), the reaction conditions of compound III is: inflated with nitrogen, starting temperature is 100-110 ℃, final temperature 160-180 ℃, keeps 1.0-1.5 hour; Resynthesis crocetin dimethyl ester, the condition of synthetic crocetin dimethyl ester is: logical nitrogen, with NaH is alkali, THF is a reaction solvent, 2, and 7-dimethyl-2,4,6-sarohornene-1, the reacting material ratio of 8-dialdehyde (Compound I I), sodium hydride and E-2-methyl-2-butene acid methyl esters-4-diethyl phosphonate (compound III) is 1: 3: 2.5, reaction is 0.5-1.0 hour in ice bath;

D, crocetin dimethyl ester hydrolysis reaction is obtained crocetin:

Get the crocetin dimethyl ester, behind DMF dissolving crocetin dimethyl ester, add the KOH aqueous solution, reflux 1h, the some plate, the crocetin dimethyl ester all is hydrolyzed, and after the acidifying, filtration can get crocetin;

E, usefulness crocetin and synthetic crocetin imidazoles of carbonylic imidazole reaction and then synthetic crocin glucoside;

Under nitrogen protection, crocetin and N, N-carbonyl dimidazoles, material ratio is: 1: (2-12), and reaction reaction in 1-2 hour in the DMSO solvent, filtering reacting liquid, remove DMSO with ether or petroleum ether filter cake, 35 ℃ of vacuum-dryings obtain compound crocetin imidazoles;

Crocetin imidazoles and glucose under nitrogen protection; material ratio is: 1: (3-7); be dissolved in the pyridine, add NaH again, after stirring reaction 1-3 hour; filtering reacting liquid is removed the NaOH and the excessive N aH of generation; with n-butanol extraction three times, merge n-butanol layer, wash n-butanol layer with water three times; with the propyl carbinol evaporate to dryness, anti-phase C ₁₈Chromatogram is crossed column purification and is got crocin glucoside.

2, the synthetic method of crocin glucoside according to claim 1 is characterized in that: the contract material ratio of dicarbaldehyde of Compound I and acetone is 1: 5 in a step; The material ratio of Compound I and NaH is 1: 3.

3, the synthetic method of crocin glucoside according to claim 1 is characterized in that: E-2-methyl in the b step-4-bromo-2-butylene acid is 1: 1 with the reacting material ratio of thionyl chloride.

4, the synthetic method of crocin glucoside according to claim 1 is characterized in that: described crocetin of e step and N, the material ratio of N-carbonyl dimidazoles are 1: (8-10); The theoretical material ratio of described crocetin imidazoles and glucose is 1: 5; The material ratio of crocetin imidazoles and NaH was at 1: 8.

5, the synthetic method of crocin glucoside according to claim 4 is characterized in that: described crocetin of e step and N, the material ratio of N-carbonyl dimidazoles are 1: 10.

6, the synthetic method of crocin glucoside according to claim 1 is characterized in that: the described anti-phase C18 chromatogram of e step is crossed the column purification condition and is: V (H ₂O): V (MeOH)=1: 1.