Method for rapid recognition of mandelic acid enantiomers by chiral fluorescent molecular cage

Abstract

The application discloses a method for quickly identifying mandelic acid enantiomers by using chiral fluorescent molecular cages, and utilizes the aggregation-induced emission (AIE) characteristics of tetramethoxy tetraphenyl ethylene to study the recognition performance of the molecular cages on the enantiomers of the chiral acid guest. A solvent is prepared by mixing tetrahydrofuran (THF) and water in a certain proportion, tetramethoxy tetraphenyl ethylene molecular cages are added, and then the fluorescence of different kinds of chiral acid guests is determined. The chiral self-adaptive recognition of the tetramethoxy tetraphenyl ethylene fluorescent molecular cages provided by the application to different amino acid molecules can quickly identify mandelic acid enantiomers. By adding the solvent to the mandelic acid, whether the mandelic acid is L type or D type can be quickly distinguished, and a new possibility is provided for the recognition of amino acids based on the chiral fluorescent molecular cages.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic compound synthesis, and particularly relates to a method for quickly identifying mandelic acid enantiomers by using a chiral fluorescent molecular cage. BACKGROUND

[0002] Porous molecular cages can be divided into two types according to the construction mode, namely supramolecular cages and porous organic cages (POCs). Supramolecular cages are formed by coordination of metal ligands or combination of hydrogen bonds, while porous organic cages are formed by covalent bonds of light non-metal elements (such as hydrogen, boron, carbon, nitrogen and oxygen) and pure organic building units. Compared with supramolecular cages, the number of porous organic cages is less because their synthesis is more difficult.

[0003] POCs have attracted great attention in the past few years. In principle, the synthesis of POCs can adopt reversible or irreversible bonding. The synthesis of organic molecular cages usually requires multi-step reactions, such as cross-coupling reactions or amidation reactions, to form irreversible bonds. Reversible bond formation based on dynamic covalent chemistry can more efficiently complete these reactions with higher yields. Cage compounds are important in various applications including molecular sensing, separation and catalysis. By using dynamic covalent chemistry, hydrogen bonds and metal-organic coordination, researchers have synthesized many molecular cages with different sizes and shapes. Because chirality increases the structural complexity and function of the cage itself, as well as their hierarchical combinations, chiral cages have become extremely interesting and have attracted extensive attention from chemists.

[0004] CN 111471049A discloses an organic fluorescent molecular cage compound and a preparation method thereof, which is prepared by reacting a polyaldehyde aromatic compound and a polyamine aromatic compound. The organic fluorescent molecular cage material prepared by rapid preparation can solve the technical problem of on-site separation and identification of nitro aromatic compounds. The preparation process is simple and controllable, and the reaction can be carried out at room temperature without catalyst and sample pretreatment. The prepared organic fluorescent molecular cage has significant specific response to nitro aromatic compounds.

[0005] With the development of dynamic covalent chemistry in recent years, a large number of porous organic cages have been continuously reported. The intrinsic pores generated by the cage cavity and the low-efficiency extrinsic pores caused by molecular filling provide potential applications of molecular cages for gas adsorption and separation, sensing, molecular separation, catalysis, etc. The introduction of chirality in the preparation of molecular cage materials can be used in the fields of chiral resolution and separation, asymmetric catalysis and chiral sensing, etc. SUMMARY

[0006] In view of the problems in the prior art, the present application provides a method for quickly identifying mandelic acid enantiomers by using chiral fluorescent molecular cages, which is simple and easy to implement. The chiral fluorescent molecular cage has an AIE effect, and the fluorescence intensity of the mandelic acid enantiomers is quite different, so it has good distinguishability and good applicability. The present application can quickly distinguish whether the mandelic acid is L-type or D-type by adding a solvent dropwise into the mandelic acid. The present application provides a new possibility for the recognition of amino acids based on chiral fluorescent molecular cages.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] The method for quickly identifying mandelic acid enantiomers by using chiral fluorescent molecular cages, wherein the chiral fluorescent molecular cage is tetramethoxy tetraphenyl ethylene molecular cage, the tetramethoxy tetraphenyl ethylene molecular cage is added into a mixed solvent of tetrahydrofuran and water, and then a chiral acid is added for fluorescence determination.

[0009] As a preferred technical solution of the present application, the synthesis method of the tetramethoxy tetraphenyl ethylene molecular cage is as follows: tetramethoxy tetraaldehyde tetraphenyl ethylene and cyclohexanediamine are added into CHCl3 for heating, stirring, reflux reaction, and then a solid product tetramethoxy tetraphenyl ethylene molecular cage is obtained, the obtained product tetramethoxy tetraphenyl ethylene molecular cage is washed, and then dried in a vacuum oven to obtain yellow crystals, which are TPE skeleton structure molecular cages, and the preparation route is as shown below:

[0010]

[0011] As a preferred technical solution of the present application, the molar ratio of the tetramethoxy tetraaldehyde tetraphenyl ethylene and the cyclohexanediamine is 1:2.4.

[0012] As a preferred technical solution of the present application, the stirring temperature of the tetramethoxy tetraphenyl ethylene molecular cage during synthesis is 55℃, and the reflux reaction time is 12 hours.

[0013] As a preferred technical solution of the present application, the solid product tetramethoxy tetraphenyl ethylene molecular cage is washed with ethyl acetate for 3 times, and then washed with methanol for 5 times.

[0014] As a preferred technical solution of the present application, the drying temperature is room temperature, and the drying time is 24 hours.

[0015] As a preferred technical solution of the present application, the molar ratio of the tetramethoxy tetraphenyl ethylene molecular cage and the chiral acid is 1:1.

[0016] As a preferred technical solution of the present application, the volume ratio of tetrahydrofuran to water in the mixed solvent is 1:0 to 1:19, preferably 1:4.

[0017] As a preferred technical solution of the present application, the chiral acid is chiral mandelic acid.

[0018] The application has the advantages that the application uses different spatial matching degrees of chiral molecular cages and amino acid enantiomers to generate different forces, exhibits different characteristics of fluorescence emission intensity, and quickly identifies enantiomers. The application does not need expensive chiral separation, nuclear magnetic judgment and other means, effectively shortens the detection time, greatly reduces the economic cost, and is a very practical scheme in conventional enantiomer detection and identification. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage in different proportions of water / THF solvent.

[0020] Figure 2 It is a CD graph of tetramethoxy tetraphenyl ethene molecular cage.

[0021] Figure 3 It is a CPL graph of tetramethoxy tetraphenyl ethene molecular cage.

[0022] Figure 4 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage mixed with chiral mandelic acid.

[0023] Figure 5 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage mixed with chiral glutamic acid.

[0024] Figure 6 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage mixed with chiral pyroglutamic acid.

[0025] Figure 7 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage mixed with chiral arginine.

[0026] Figure 8 It is a fluorescence spectrum of tetramethoxy tetraphenyl ethene molecular cage mixed with chiral tyrosine. DETAILED DESCRIPTION

[0027] The application will be further described below in combination with specific examples. It should be understood that the following examples are only used to illustrate the application and not used to limit the scope of the application, and those skilled in the art can make some non-essential improvements and adjustments according to the content of the above application.

[0028] Example 1 Preparation of tetramethoxy tetraphenyl ethene molecular cage

[0029] The preparation route of tetramethoxy tetraphenyl ethene molecular cage in the application is shown as follows

[0030]

[0031] The preparation method of the tetramethoxytetraphenyl ethene molecular cage in this embodiment is as follows:

[0032] Tetramethoxytetraformyltetraphenyl ethene (3.6 g, 6.38 mmol) and cyclohexanediamine (1.75 g, 15.31 mmol) were added to a CHCl3 solution, which was stirred vigorously under reflux at 55°C, and the reaction was carried out for 12 hours to obtain a solid product. The solid product was washed with ethyl acetate for 3 times, then washed with methanol for 5 times, and then dried in a vacuum oven at room temperature for 24 hours to obtain yellow crystals, which were tetramethoxytetraphenyl ethene molecular cages.

[0033] Figure 2 and Figure 3 respectively, are the CD and CPL diagrams of the tetramethoxytetraphenyl ethene molecular cage, which proves that the tetramethoxytetraphenyl ethene molecular cage with certain chirality and helicity has been successfully synthesized.

[0034] The tetramethoxytetraphenyl ethene molecular cage was added to mixed solvents of tetrahydrofuran and water in different volume ratios (1:0, 9:1, 4:1, 7:3, 3:2, 1:1, 2:3, 3:7, 1:4, 1:9, 1:19), and then fluorescence determination was performed, Figure 1 is the fluorescence spectrum of the tetramethoxytetraphenyl ethene molecular cage in different proportions of water / THF+water solvents (the volume fraction of water in the mixed solvents is 0, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, respectively). Figure 1 It can be seen from the above table that the fluorescence intensity of the tetramethoxytetraphenyl ethene molecular cage in pure THF solvent is very weak, and with the increase of the poor solvent water, the tetramethoxytetraphenyl ethene molecular cage forms aggregated particles, and the fluorescence intensity gradually increases. The fluorescence intensity of the tetramethoxytetraphenyl ethene molecular cage is the strongest when the ratio of water to solvent is 80%, and when the ratio of water to solvent is higher than 80%, the tetramethoxytetraphenyl ethene molecular cage forms aggregates, precipitates at the bottom of the solution instead of being uniformly suspended in the solution, and the fluorescence intensity decreases. The maximum absorption wavelength of the fluorescence emission spectrum of the tetramethoxytetraphenyl ethene molecular cage in the water / THF solvent with different proportions is about 520 nm.

[0035] Example 2

[0036] The tetramethoxytetraphenyl ethene molecular cage was added to a mixed solvent composed of tetrahydrofuran and water in a volume ratio of 1:4, and then fluorescence determination was performed by adding chiral mandelic acid, and the molar ratio of the tetramethoxytetraphenyl ethene molecular cage to the chiral mandelic acid was 1:1.

[0037] Example 3

[0038] The tetramethoxytetraphenyl ethene molecular cage was added to a mixed solvent of THF and water in a volume ratio of 1:4, and then fluorescence determination was carried out by adding chiral glutamic acid, and the molar ratio of the tetramethoxytetraphenyl ethene molecular cage and the chiral glutamic acid was 1:1.

[0039] Example 4

[0040] The tetramethoxytetraphenyl ethene molecular cage was added to a mixed solvent of THF and water in a volume ratio of 1:4, and then fluorescence determination was carried out by adding chiral glutamic acid, and the molar ratio of the tetramethoxytetraphenyl ethene molecular cage and the chiral glutamic acid was 1:1.

[0041] Example 5

[0042] The tetramethoxytetraphenyl ethene molecular cage was added to a mixed solvent of THF and water in a volume ratio of 1:4, and then fluorescence determination was carried out by adding chiral glutamic acid, and the molar ratio of the tetramethoxytetraphenyl ethene molecular cage and the chiral glutamic acid was 1:1.

[0043] Example 6

[0044] The tetramethoxytetraphenyl ethene molecular cage was added to a mixed solvent of THF and water in a volume ratio of 1:4, and then fluorescence determination was carried out by adding chiral glutamic acid, and the molar ratio of the tetramethoxytetraphenyl ethene molecular cage and the chiral glutamic acid was 1:1.

[0045] Figure 4 The fluorescence spectrum of the mixture of tetramethoxytetraphenyl ethene molecular cage and chiral mandelic acid. Figure 5 The fluorescence spectrum of the mixture of tetramethoxytetraphenyl ethene molecular cage and chiral glutamic acid. Figure 6 The fluorescence spectrum of the mixture of tetramethoxytetraphenyl ethene molecular cage and chiral glutamic acid. Figure 7 The fluorescence spectrum of the mixture of tetramethoxytetraphenyl ethene molecular cage and chiral glutamic acid. Figure 8 The fluorescence spectrum of the mixture of tetramethoxytetraphenyl ethene molecular cage and chiral glutamic acid. Figures 4-8 It can be found that the mixed solvent of tetramethoxytetraphenyl ethene molecular cage and THF and water can recognize L type and D type of various chiral acids. Through experiments, it is found that the fluorescence intensity of mandelic acid enantiomers is quite different, which has good distinguishability and good applicability. By adding the prepared solvent to the amino acid, it is known whether the mandelic acid is L type or D type, and the type of amino acid is identified through simple fluorescence recognition.

[0046] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for rapid recognition of mandelic acid enantiomers by chiral fluorescent molecular cages, characterized by: The chiral fluorescent molecular cage is a tetramethoxy tetraphenyl ethylene molecular cage, the tetramethoxy tetraphenyl ethylene molecular cage is added into a mixed solvent of tetrahydrofuran and water, then fluorescence determination is carried out by adding chiral mandelic acid; The molar ratio of the tetramethoxy tetraphenyl ethylene molecular cage and the chiral mandelic acid is 1:1; The volume ratio of tetrahydrofuran to water in the mixed solvent is 1:4-1:19; The synthesis method of the tetramethoxy tetraphenyl ethylene molecular cage is as follows: tetramethoxy tetraaldehyde tetraphenyl ethylene and (R,R)-cyclohexane diamine are added into CHCl3, heated, stirred, refluxed and reacted to obtain a solid product, the obtained solid product is washed, then dried in a vacuum oven to obtain yellow crystals, which are the tetramethoxy tetraphenyl ethylene molecular cage; The structural formula of the tetramethoxy tetraaldehyde tetraphenyl ethylene is as follows: ； The structural formula of the (R,R)-cyclohexane diamine is as follows: ； The molar ratio of the tetramethoxy tetraaldehyde tetraphenyl ethylene and the (R,R)-cyclohexane diamine is 1:2.4; The stirring temperature during the synthesis of the tetramethoxy tetraphenyl ethylene molecular cage is 55°C, and the reflux reaction time is 12 hours.

2. The method for rapid recognition of mandelic acid enantiomers by chiral fluorescent molecular cages according to claim 1, characterized in that, The solid product is washed with ethyl acetate for 3 times, and then washed with methanol for 5 times.

3. The method for rapid recognition of mandelic acid enantiomers by chiral fluorescent molecular cages according to claim 1, characterized in that, The drying temperature is room temperature, and the drying time is 24 hours.

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