A modified cyclodextrin and its preparation method and application in the identification and separation of nicotine enantiomers

Abstract

The present invention discloses a modified cyclodextrin and its preparation method and application in the identification and separation of nicotine enantiomers. The present invention adopts a one-pot method to covalently bond β-cyclodextrin modified by phenyl isocyanate on the surface of silica gel, which is simple to operate and low in cost. The chiral column filled with the material can achieve the separation of racemic nicotine enantiomers under normal phase conditions, and the separation degree can reach 6.14. The present invention provides a new technical route for the separation and detection of optically pure nicotine.

Description

Technical Field

[0001] The invention belongs to the field of enantiomer separation, and specifically relates to a modified cyclodextrin and a preparation method thereof, and the identification and separation application of nicotine enantiomers. Background Art

[0002] Nicotine is a natural chiral amine bicyclic compound with a pyridine ring and a tetrahydropyrrole ring, which is widely found in tobacco and Solanaceae plants. Clinical studies have shown that nicotine is a nicotinic acetylcholine receptor agonist and is expected to become a drug for the treatment of Alzheimer's disease, schizophrenia and other diseases (Pharmacological chaperoning of nAChRs: a therapeutic target for Parkinson's disease [J]. Pharmacological Research, 2014, 83: 20-29.). In addition, as early as the 1990s, the World Health Organization vigorously promoted "nicotine replacement therapy" for smoking cessation around the world. In agriculture, nicotine and other nicotinic compounds are important active components of insecticides (Yamamoto I and Casida J E. Nicotinoid Insecticides and the Nicotinic Acetylcholine Receptor [J]. Springer-Verlag: Tokyo, 1999: 300pp.).

[0003] Nicotine is optically active and exists as two enantiomers, (R)-nicotine and (S)-nicotine. A large number of studies have been conducted on the synthesis of racemic nicotine, but it is generally recognized that (S)-nicotine is more active than (R)-nicotine. Both the tobacco industry and the pharmaceutical field require (S)-nicotine with high optical purity. Therefore, separation and detection of the optical purity of nicotine optical enantiomers play an important role in biopharmaceuticals, pesticide detection and tobacco economy.

[0004] Cyclodextrin is a class of chiral supramolecular compounds constructed from glucose units. Its abundant chiral recognition sites, hydrophobic inner cavity and chemical modifiability provide an excellent chiral microenvironment for chiral identification and separation of optical enantiomers. Compared with other natural cyclodextrins, β-cyclodextrin has a larger cavity and a low preparation cost, and is widely used in enantiomer identification and resolution. Chemical modification of β-cyclodextrin can further introduce other substituent groups, enrich the chiral recognition effect between cyclodextrin and chiral samples, enhance the chiral recognition ability of cyclodextrin, and expand the resolution range of racemic samples. However, the existing methods for chemical modification of β-cyclodextrin are relatively cumbersome, and there are few reports on the direct synthesis of chemically modified cyclodextrins using a one-pot method, and the separation performance is poor. For example, although the silica gel-filled microcolumn bonded with β-cyclodextrin can achieve the ultimate separation of nicotine with a resolution of 1.7, the analysis time is relatively long (300 min) (Journal of Chromatography A, 1987 (411): 490-493.). Another homemade column bonded with β-cyclodextrin cannot achieve the separation of nicotine enantiomers (Analytical Chemistry, 1988, 60 (19): 2120-2127.). There are almost no cyclodextrin liquid chromatography columns that are easy to prepare and have excellent separation effects on nicotine enantiomers, which is also one of the bottlenecks restricting the separation and detection of nicotine enantiomers. Summary of the invention

[0005] In view of the bottleneck problem in the technical field of separation and detection of nicotine enantiomers, the purpose of the present invention is to provide a modified cyclodextrin and its preparation method and its application in the identification and separation of nicotine enantiomers. The present invention directly synthesizes phenylisocyanate chemically modified cyclodextrin by a one-pot method, which is simple to operate and low in cost; and achieves baseline separation of racemic nicotine enantiomers, providing a new technical route for the separation and detection of optically pure nicotine.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for preparing a modified cyclodextrin comprises the following steps:

[0008] Dissolve β-cyclodextrin and γ-isocyanatepropyltriethoxysilane in anhydrous pyridine, stir and reflux at 75-85°C; then add phenyl isocyanate derivative, stir at 95-110°C; then add acidified silica gel, stir at 95-110°C; after the reaction is completed, filter, wash and dry to obtain a white powdery solid, which is the modified cyclodextrin.

[0009] Preferably, the phenyl isocyanate derivative is one of phenyl isocyanate, 3,5-dimethylphenyl isocyanate and 4-chlorophenyl isocyanate.

[0010] Preferably, the stirring and reflux time is 20-26 hours; after adding the phenyl isocyanate derivative, stirring is performed at 95-110° C. for 18-26 hours; then acidified silica gel is added and stirred at 95-110° C. for 10-16 hours.

[0011] Preferably, after the filtration, the solid product is washed with water and methanol respectively, and vacuum dried at 55-60° C. for 10-12 hours.

[0012] Preferably, the molar ratio of the β-cyclodextrin to the γ-isocyanatepropyltriethoxysilane is (3-4):1.

[0013] Preferably, the ratio of the β-cyclodextrin to anhydrous pyridine is (0.03-0.04) g:1 mL.

[0014] Preferably, the molar ratio of the β-cyclodextrin to the phenyl isocyanate derivative is (15-17):1.

[0015] Preferably, the mass ratio of the β-cyclodextrin to the acidified silica gel is (0.25-0.5):1.

[0016] A modified cyclodextrin prepared by any of the preparation methods described above has the following structural formula:

[0017]

[0018] It is acidified silica gel.

[0019] A modified cyclodextrin is used in the identification and separation of nicotine enantiomers, wherein the structural formula of the modified cyclodextrin is as follows:

[0020]

[0021] It is acidified silica gel.

[0022] Preferably, the modified cyclodextrin is prepared by the above method.

[0023] Preferably, the modified cyclodextrin filler is packed into a column, and in normal phase mode, n-hexane and ethanol are used as mobile phases, the flow rate is 1 mL / min, the detection wavelength is 254 nm, and the column temperature is 35°C.

[0024] Preferably, the volume ratio of n-hexane to ethanol is (70:30) to (90:10).

[0025] Preferably, trifluoroacetic acid and diethylamine are dissolved in n-hexane to adjust the peak shape.

[0026] The modified cyclodextrin stationary phase prepared by the present invention uses β-cyclodextrin as a substrate, and chemically modifies the β-cyclodextrin by adding a phenyl isocyanate derivative, and simultaneously adds γ-isocyanate propyl triethoxysilane and silica gel to directly covalently bond the modified cyclodextrin to the silica gel filler in one step.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The modified cyclodextrin prepared by the present invention has a simple synthesis process and low raw material cost.

[0029] (2) The modified cyclodextrin of the present invention can selectively form a host-guest inclusion complex with nicotine enantiomers to achieve enantiomeric separation of nicotine with excellent separation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is the infrared spectrum of the modified cyclodextrin stationary phase and acidified silica gel in Example 1.

[0031] Figure 2 Enantiomer separation of racemic nicotine in normal phase mode on a modified cyclodextrin stationary phase. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with examples and drawings, but the embodiments of the present invention are not limited thereto.

[0033] If no specific conditions are specified in the examples of the present invention, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. All raw materials, reagents, etc., whose manufacturers are not specified, are conventional products that can be purchased commercially.

[0034] Example 1

[0035] Dissolve β-cyclodextrin (1g) and γ-isocyanate propyl triethoxysilane (0.8g) in anhydrous pyridine (35mL) and stir under reflux at 80°C for 24 hours. Add 3,5-dimethylphenyl isocyanate (2g) to the mixed solution and stir at 100°C for 24 hours. Add acidified silica gel (3.5g) and stir at 100°C for 12 hours. After the reaction is completed, filter and wash the solid product with water and methanol respectively, and vacuum dry at 60°C to obtain a white powdery solid, which is the modified β-cyclodextrin chiral stationary phase Sil-MPCD.

[0036] Example 2

[0037] β-cyclodextrin (1.2 g) and γ-isocyanate propyl triethoxysilane (0.8 g) were dissolved in anhydrous pyridine (30 mL) and stirred at 85 ° C for 20 hours. Phenyl isocyanate (2.2 g) was added to the mixed solution and stirred at 100 ° C for 22 hours. Acidified silica gel (2.5 g) was added and stirred at 110 ° C for 16 hours. After the reaction was completed, the solid product was filtered and washed with water and methanol respectively, and vacuum dried at 60 ° C to obtain a white powder solid, which was the modified β-cyclodextrin chiral stationary phase Sil-PCD.

[0038] Example 3

[0039] Dissolve β-cyclodextrin (0.8 g) and γ-isocyanate propyltriethoxysilane (0.9 g) in anhydrous pyridine (25 mL) and stir under reflux at 80 ° C for 24 hours. Add 4-chlorophenyl isocyanate (2 g) to the mixed solution and stir at 95 ° C for 26 hours. Add acidified silica gel (3 g) and stir at 100 ° C for 12 hours. After the reaction is completed, filter, wash the solid product with water and methanol respectively, and vacuum dry at 60 ° C to obtain a white powdery solid, which is the modified β-cyclodextrin chiral stationary phase Sil-CPCD.

[0040] Material structure characterization and performance determination

[0041] Table 1

[0042]

[0043] (Note: S BET is the BET specific surface area; V t is the total pore volume)

[0044] Table 1 shows the specific surface area and pore structure characterization parameters of different modified cyclodextrins and acidified silica gel (Sil). The results show that the specific surface area of ​​the modified cyclodextrin prepared by the present invention is about 240-250 m 2 / g, and the total pore volume range is 0.65~0.75cm 3 / g. This indicates that the stationary phase prepared by the present invention has a well-developed pore structure.

[0045] Figure 1 This is the infrared spectrum of the phenyl isocyanate derivative modified cyclodextrin stationary phase and acidified silica gel prepared in Example 1. Among them, 1096 and 803 cm -1 Compared with acidified silica gel, Sil-MPCD has the absorption peaks of 2958, 1716, 1556, and 1457 cm -1 New vibration absorption peaks appeared at 2958cm -1 is the vibration absorption peak of methyl group, 1716cm -1The vibration absorption peaks of the carbonyl group on the amide bond are 1556 and 1457 cm -1 It is the absorption peak of the skeleton vibration of the benzene ring, which indicates that 3,5-dimethylphenyl isocyanate is successfully bonded to the hydroxyl site of β-cyclodextrin, and the present invention achieves successful modification of β-cyclodextrin.

[0046] Figure 2 The enantiomer separation of racemic nicotine in the normal phase mode of the modified cyclodextrin stationary phase of Example 1. The mobile phase conditions are n-hexane (containing 0.05 vol% trifluoroacetic acid and 0.02 vol% diethylamine): anhydrous ethanol = 80:20, the detection wavelength is 254 nm, the flow rate is 1 mL / min, and the column temperature is 35°C. The nicotine enantiomers achieve baseline separation, and the separation degree Rs = 6.14, indicating that the chiral column loaded with the modified β-cyclodextrin prepared by the present invention can achieve the separation of racemic nicotine enantiomers.

[0047] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Application of a modified cyclodextrin in the identification and separation of nicotine enantiomers, characterized in that: The modified cyclodextrin is used as the chiral column stationary phase, and the structural formula of the modified cyclodextrin is as follows: , or , It is acidified silica gel.

2. The use of a modified cyclodextrin according to claim 1 in the identification and separation of nicotine enantiomers, characterized in that: The modified cyclodextrin filler was packed into a column, and in normal phase mode, n-hexane and ethanol were used as mobile phases, the flow rate was 1 mL / min, the detection wavelength was 254 nm, and the column temperature was 35°C.

3. The use of a modified cyclodextrin according to claim 2 in the identification and separation of nicotine enantiomers, characterized in that: The volume ratio of n-hexane to ethanol is (70:30) to (90:10).

4. The use of a modified cyclodextrin in the identification and separation of nicotine enantiomers according to claim 3, characterized in that: Peak shape was adjusted by dissolving trifluoroacetic acid and diethylamine in n-hexane.

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