A diphenylphosphinyloxy-X-phenol compound, preparation method and application thereof in the preparation of aspartame

Abstract

The present invention relates to a diphenylphosphinyloxy-X-phenol compound, a preparation method thereof, and an application thereof in the preparation of aspartame, belonging to the technical field of organic synthesis. The general structural formula of the diphenylphosphinyloxy-X-phenol compound DPXP is as shown in formula (I). The present invention also provides a preparation method of aspartame assisted by the diphenylphosphinyloxy-X-phenol compound. The present invention uses the diphenylphosphinyloxy-X-phenol compound DPXP as a carrier to assist the liquid-phase synthesis method of aspartame. By utilizing the auxiliary precipitation effect of the DPXP carrier, through the strategy of coupling with an equivalent amount of amino acid and deprotecting Boc in a liquid-phase reaction, the preparation method of aspartame is optimized and simplified, and the recyclability and reusability of the DPXP carrier are verified.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a diphenylphosphinyloxy-X-phenol compound, a preparation method thereof, and an application thereof in the preparation of aspartame. Background Art

[0002] Aspartame (APM) is a newly synthesized artificial sweetener, with the chemical name of N-α-L-aspartyl-L-phenylalanine methyl ester. In 1965, James M. Schlatter accidentally discovered its sweet taste when synthesizing gastrin. It is a dipeptide composed of asparagine and phenylalanine methyl ester (phenylalanine is an essential amino acid for the human body), which is helpful for the digestion and absorption of the human body. Compared with traditional sweeteners, as a new type of sweetener, aspartame has the advantages of low calorie, high sweetness, and high safety. Its sweetness is 200 times that of sucrose, but the calorie is less than 1 / 200 of sucrose, and it is widely used in low-calorie foods, medicine and other fields. The digestion and absorption process of APM in the human body does not involve insulin and will not cause changes in human blood sugar, so it is favored by diabetic patients. So far, aspartame has been approved for use in more than 100 countries and regions in the world and has developed into a powerful sweetener dominating the international market and is used as an artificial sweetener in more than 6,000 kinds of foods. At present, the main methods for producing aspartame at home and abroad are biosynthesis method and chemical synthesis method.

[0003] For chemical synthesis methods, the acid anhydride method, thioanhydride method, lactone method, and resin method are mainly used. In the initial acid anhydride method, the amino group of aspartic acid (Asp) was first protected, then an acid anhydride was formed and reacted with phenylalanine methyl ester, and the protecting group of the α-amino group was removed, and the by-product β-isomer was purified and removed; or it was first reacted with aspartic acid and then methyl esterified. Common amino-terminal protecting groups include benzyloxycarbonyl (Cbz), formyl, acetoacetyl, trifluoroacetyl (Tfa), etc. The Cbz group is easy to introduce as a protecting group and has good stability, but it is difficult to remove, has a high cost, requires the use of expensive Pd / C, and phosgene, a highly toxic substance, needs to be used in the production process of Cbz-Cl, which does not conform to the concept of environmental protection; the formyl group is easy to remove but prone to generate β-APM (bitter taste), and the product yield is low; the raw material price of acetoacetyl is high and it is toxic; trifluoroacetyl can be easily removed using 0.1 - 0.2 M NaOH aqueous or ethanol aqueous solution, but it has poor selectivity and is prone to racemization. In summary, the acid anhydride method has certain defects. The thioanhydride method is to use a sulfurylating agent as a protecting agent at low temperature to make L-aspartic acid into its acyl compound. After adding a cyclizing reagent to carry out a cyclization reaction and obtaining a cyclic compound, it is condensed with L-phenylalanine methyl ester hydrochloride under alkaline conditions to obtain crude aspartame. This method has good selectivity, but the yield is low, and the product often has an unpleasant smell due to the presence of sulfur compounds. The pH requirement is strict during the reaction process, otherwise it is easy to generate by-products, so it is not widely used. The lactone method for synthesizing aspartame is to protect the amino group of aspartic acid with Cbz, form a lactone by reacting with paraformaldehyde at the α-amino group under acidic conditions, then condense with L-phenylalanine methyl ester, and finally catalytically hydrogenolyze with Pd / C to form aspartame. Its advantages are high selectivity, no need to separately protect the carboxyl group, no generation of bitter β-APM, and high yield, but the synthesis raw materials are toxic, and the removal of the Cbz group requires the use of Pb / C, which is expensive and harmful to the human body, so industrial production is hindered. The resin method uses the SPPS method to use the resin as a protecting group for the α-carboxyl group of aspartic acid, and then carry out condensation and deprotection reactions to obtain aspartame. The SPPS resin is insoluble, expensive and non-degradable, so it is not suitable for large-scale industrial production.

[0004] It can be seen that the current chemical production methods of aspartame mainly adopt traditional solution synthesis and solid-phase synthesis methods, which have problems such as cumbersome separation and purification steps, large waste of raw materials and solvents, and serious environmental pollution caused by a large amount of resin solid waste that is difficult to degrade. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the present invention provides a diphenylphosphinyloxy-X-phenol compound (DPXP), a preparation method thereof, and an application thereof in the preparation of aspartame. The method mainly uses the DPXP as a carrier-assisted liquid-phase synthesis method for aspartame. By utilizing the auxiliary precipitation effect of the DPXP carrier, through the strategy of coupling with an equivalent amount of amino acid and deprotecting Boc in a liquid-phase reaction, the preparation method of aspartame is optimized and simplified, and the recyclability and reusability of the DPXP carrier are verified. It mainly solves the problems of the current chemical synthesis method of aspartame, such as more steps in the liquid-phase reaction, long time-consuming cycle, high content of by-product β-type isomers, difficult separation and impurity removal, low product purity, small purification scale, high production cost, small production scale in solid-phase reaction, expensive raw materials, large waste, a large amount of resin waste, and serious environmental pollution.

[0006] The diphenylphosphinyloxy-X-phenol compound provided by the present invention has a general structural formula as shown in formula (I):

[0007]

[0008] (Ⅰ)

[0009] In the formula, X is O, or 。

[0010] The preparation method of the diphenylphosphinyloxy-X-phenol compound provided by the present invention includes the following steps:

[0011] React p-substituted phenol of diphenylphosphinyl chloride under alkaline conditions, and obtain the diphenylphosphinyloxy-X-phenol compound through separation and purification;

[0012] Wherein, X is O, or ;

[0013] The p-substituted phenol includes hydroquinone, 4,4'-dihydroxybenzophenone or bisphenol A.

[0014] The present invention provides an application of the diphenylphosphinyloxy-X-phenol compound in the preparation of aspartame.

[0015] The present invention provides a preparation method of aspartame based on the assistance of the diphenylphosphinyloxy-X-phenol compound, including the following steps:

[0016] Using the compound of formula (I) as a carrier, reacting with an N-terminal protected amino acid under the action of a coupling agent to obtain product A; subjecting product A to purification treatment to obtain purified product A; wherein, the N-terminal protected amino acid is phenylalanine protected by a protecting group of fluorenylmethoxycarbonyl or tert-butoxycarbonyl;

[0017] The purified product A is treated with a fluorenylmethyloxycarbonyl removing reagent or a tert-butoxycarbonyl removing reagent to obtain product B; the obtained product B is purified to obtain purified product B;

[0018] Using the purified product B as a raw material, it is coupled with aspartic acid whose N-terminus and side-chain carboxyl group are both protected to obtain compound C;

[0019] Using a methanol or tetrahydrofuran solution containing sodium methoxide as a shearing agent, compound C is sheared to remove the compound of formula (I) to obtain compound D; then, using a cocktail solution of trifluoroacetic acid as a side-chain deprotecting agent for compound D, the protecting groups on the side chain are removed to obtain the trifluoroacetate E of aspartame;

[0020] The trifluoroacetate E of aspartame is neutralized with sodium bicarbonate, extracted with ethyl acetate, precipitated, filtered, washed with ethyl acetate, and dried to obtain pure aspartame F;

[0021] Among them, formula (I) is , X is O, or .

[0022] Preferably, the purification process of product A includes:

[0023] An alkane or ether solvent is added to product A to separate product A from other impurities;

[0024] The separated product A is filtered, washed, or recrystallized to obtain purified product A.

[0025] Preferably, the purification process of product B includes:

[0026] An alkane or ether solvent is added to product B to separate product B from other impurities;

[0027] The separated product B is filtered, washed, or recrystallized to obtain purified product B.

[0028] Preferably, the general structural formula of product A is:

[0029] ;

[0030] Among them, PG is 9-fluorenylmethyloxycarbonyl, tert-butoxycarbonyl or H.

[0031] Preferably, the general structural formula of compound C is:

[0032] ;

[0033] The general structural formula of compound D is:

[0034] ;

[0035] PG1 is tert-butoxycarbonyl, benzyloxycarbonyl, fluorenylmethyloxycarbonyl or H;

[0036] PG2 is Fm, Bz or tBu.

[0037] Preferably, the coupling agent includes a carbodiimide condensing agent, a carbonium salt condensing agent or a phosphonium salt condensing agent.

[0038] Preferably, the fluorenylmethyloxycarbonyl removing reagent includes a solution of piperidine, a methanol solution of diethylamine, an acetonitrile solution, a tetrahydrofuran (THF) solution or an N,N-dimethylformamide (DMF) solution;

[0039] The tert-butoxycarbonyl removing reagent includes trifluoroacetic acid, hydrochloric acid, a dichloromethane, chloroform or N,N-dimethylformamide (DMF) solution of phosphoric acid.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] The present invention provides a diphenylphosphinyloxy-X-phenol compound, a preparation method and an application thereof in the preparation of aspartame. The diphenylphosphinyloxy-X-phenol compound (DPXP) provided by the present invention has rich and easily available raw materials for synthesizing the DPXP carrier, mild reaction conditions, short time consumption, good yield, easy separation and high purity. Replacing the polymer resin in solid-phase peptide synthesis with the DPXP carrier, the homogeneous reaction efficiency is high, and the raw material consumption is saved. After shearing, the DPXP fragment is easily separated from aspartame, and the DPXP fragment can be recycled, reducing waste discharge, saving costs, being environmentally friendly, and having good social and economic benefits. Due to the protection and auxiliary precipitation effects of the DPXP carrier, the generation of the β-isomer of aspartame is avoided, and the product quality is good without the bitter taste of the β-isomer.

[0042] The present invention mainly relates to a liquid-phase synthesis method of aspartame assisted by DPXP as a carrier. By utilizing the auxiliary precipitation effect of the DPXP carrier, through the strategy of coupling with an equivalent amount of amino acid and removing the Boc protection in a liquid-phase reaction, the preparation method of aspartame is optimized and simplified, and the recyclability and reusability of the DPXP carrier are verified. In addition, the present invention designs and develops two new simplified synthesis schemes for aspartame. Solving the problems of low yield, many by-products and complex production process existing in current biological synthesis and chemical synthesis, enhancing the greening and scale-up of the aspartame synthesis process, being beneficial to emission reduction, consumption reduction, cost saving, environmental protection and sustainable development. Description of the Drawings

[0043] Figure 1 HPLC analysis of the synthesis of aspartame based on the DPOP-assisted method provided in Example 5;

[0044] Figure 2 HPLC analysis of the aspartame product provided in Example 6, where (A) represents the crude product before purification; (B) represents the purified product after refining;

[0045] Figure 3 HPLC analysis of the aspartame provided in Example 7. Detailed implementation manners

[0046] The present invention will be further described below in conjunction with specific embodiments. It should be understood that the listed embodiments are only for facilitating the understanding of the core methods and application fields of the present invention, but the scope of the present invention is not limited thereto.

[0047] In the following various embodiments, the experimental methods and detection methods are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0048] A diphenylphosphoryloxy-X-phenol compound (DPXP) provided by the present invention has a general structural formula as shown in formula (I):

[0049]

[0050] (I)

[0051] In the formula, X is O, or .

[0052] In this embodiment, when X is O, the diphenylphosphoryloxy-X-phenol compound is diphenylphosphoryloxyphenol (DPOP);

[0053] When X is , the diphenylphosphoryloxy-X-phenol compound is diphenylphosphoryloxybenzoylphenol (DPBP);

[0054] When X is , the diphenylphosphoryloxy-X-phenol compound is diphenylphosphoryloxybisphenol A (DPBPA).

[0055] The present invention provides a preparation method of a diphenylphosphoryloxy-X-phenol compound, comprising the following steps:

[0056] React diphenylphosphoryl chloride with p-substituted phenol under alkaline conditions, and obtain the diphenylphosphoryloxy-X-phenol compound through separation and purification;

[0057] Wherein, X is O, or ;

[0058] The para-substituted phenols include hydroquinone, 4,4'-dihydroxybenzophenone or bisphenol A.

[0059] The present invention provides an application of a diphenylphosphinyloxy-X-phenol compound in the preparation of aspartame.

[0060] The present invention relates to a method for the liquid-phase synthesis of aspartame assisted by a diphenylphosphinyloxy-X-phenol compound (DPXP). By utilizing the auxiliary precipitation effect of the DPXP carrier, through the strategy of coupling with an equivalent amount of amino acid and deprotecting Boc in a liquid-phase reaction, the preparation method of aspartame is optimized and simplified, and the recyclability and reusability of the DPXP carrier are verified. This solves the problems existing in current biological synthesis and chemical synthesis, such as low yield, many by-products, and complex production processes, enhances the green and large-scale production of aspartame, and is conducive to reducing emissions, saving costs, protecting the environment and sustainable development.

[0061] The present invention provides a method for preparing aspartame assisted by a diphenylphosphinyloxy-X-phenol compound, comprising the following steps:

[0062] Using the compound of formula (I) (DPXP) as a carrier, reacting with an N-terminal protected amino acid under the action of a coupling agent to obtain product A; purifying product A to obtain purified product A;

[0063] Wherein, the N-terminal protected amino acid (PG-Phe-OH) is phenylalanine protected by a protecting group (PG) of fluorenylmethoxycarbonyl (Fmoc) or tert-butoxycarbonyl (Boc); the C-terminal of the protected phenylalanine (PG-Phe-OH) is connected to the DPXP auxiliary group to obtain product A (PG-Phe-DPXP); the compound of formula (I) (DPXP) is an auxiliary group; PG is fluorenylmethoxycarbonyl (Fmoc), tert-butoxycarbonyl (Boc) or H;

[0064] Tert-butoxycarbonyl (Boc)-protected phenylalanine is denoted as Boc-Phe-OH; fluorenylmethoxycarbonyl (Fmoc)-protected phenylalanine is denoted as Fmoc-Phe-OH;

[0065] The purification process of product A includes:

[0066] Adding an alkane or ether solvent to product A to separate product A from other impurities; filtering, washing or recrystallizing the separated product A to obtain purified product A (PG-Phe-DPXP).

[0067] In this embodiment, under the action of a coupling agent, it is stirred and reacted with an N-terminal protected amino acid at 0 to 50 °C for 1 to 3 hours to obtain product A; the molar ratio of the amino acid to the DPXP auxiliary group is 1-1.2:1; the coupling agent is a dehydration coupling activator and a basic substance with a molar ratio of 1-1.2︰1; the activator refers to the commonly used 1-hydroxybenzotriazole HOBt, and the basic substance is the catalyst 4-(dimethylamino)pyridine DMAP.

[0068] The coupling agent includes carbodiimide condensing agents such as dicyclohexylcarbodiimide DCC, diisopropylcarbodiimide DIC, and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide EDCI, which are usually used in combination with the catalyst 4-(dimethylamino)pyridine DMAP and the activator 1-hydroxybenzotriazole HOBt to promote the coupling reaction; or carbonium salt condensing agents such as the commonly used 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate HATU, O-benzotriazol-1-yl-N,N,N',N'-tetramethyluronium hexafluorophosphate HBTU, 6-chlorobenzotriazol-1-yl-1,1,3,3-tetramethyluronium hexafluorophosphate HCTU, O-benzotriazol-N,N,N',N'-tetramethyluronium tetrafluoroborate TBTU, 2-(5-norbornene-2,3-dicarboximido)-1,1,3,3-tetramethyluronium tetrafluoroborate quaternary ammonium salt TNTU, 2-succinimido-1,1,3,3-tetramethyluronium tetrafluoroborate TSTU, O-(7-azabenzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate HAPyU, O-(benzotriazol-1-yl)-bis(tetrahydropyrrolyl)carbonium hexafluorophosphate HBPyU, etc.; or phosphonium salt condensing agents such as benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate PyBOP; carbonyldiimidazole CDI, etc.

[0069] Among them, the alkane or ether solvent in the purification process is a low-polarity alkane or ether solvent. Mainly relying on the characteristic that the DPXP auxiliary group is easily crystallized and precipitated in the solvent system, product A is separated from other impurities.

[0070] The general structural formula of product A is:

[0071] ;

[0072] Among them, PG is 9-fluorenylmethoxycarbonyl (Fmoc), tert-butoxycarbonyl (Boc), or H.

[0073] The purified product A is treated with a de-fluorenylmethoxycarbonyl reagent and then treated with a de-tert-butoxycarbonyl reagent to obtain product B; product B is purified to obtain purified product B;

[0074] It should be noted that when PG is Fmoc, the product A is treated with a Fmoc-deprotecting reagent; when PG is Boc, the product A is treated with a Boc-deprotecting reagent.

[0075] Among them, the purification process of the product B includes:

[0076] An alkane or ether solvent is added to the product B to separate the product B from other impurities; the separated product B is filtered, washed or recrystallized to obtain the purified product B (H-Phe-DPXP).

[0077] In this example, the purified product A is treated with a fluorenylmethyloxycarbonyl (Fmoc)-deprotecting reagent and stirred at 10 - 50 °C for 0.5 - 2 hours, or treated with a tert-butoxycarbonyl (Boc)-deprotecting reagent and stirred at 10 - 50 °C for 0.5 - 2 hours to obtain the product B (H-Phe-DPXP).

[0078] Among them, an alkane or ether solvent with low polarity is added to the product B, and the product B is separated from other impurities by virtue of the property that the DPXP auxiliary group is easily crystallized and precipitated in the solvent system.

[0079] The fluorenylmethyloxycarbonyl (Fmoc)-deprotecting reagent includes a 25% piperidine or diethylamine methanol or acetonitrile or tetrahydrofuran THF or N,N-dimethylformamide DMF solution.

[0080] The tert-butoxycarbonyl (Boc)-deprotecting reagent includes a 20 - 25% trifluoroacetic acid or hydrochloric acid or phosphoric acid dichloromethane or chloroform or N,N-dimethylformamide DMF solution.

[0081] Using the purified product B as a raw material, it is coupled with aspartic acid with both the N-terminal and side-chain carboxyl groups protected to obtain compound C;

[0082] In this example, using the purified product B containing the auxiliary group DPXP as a raw material, it is further coupled with aspartic acid with both the N-terminal and side-chain carboxyl groups protected (PG1-Asp(OPG2)-OH); steps 1 to 2 are repeated to obtain compound C (PG1-Asp(OPG2)-Phe-DPXP); it should be noted that repeating steps 1 to 2 means repeating the operation process of the above coupling reaction and deprotection reaction.

[0083] Among them, the structural general formula of compound C (PG1-Asp(OPG2)-Phe-DPXP) is:

[0084] ;

[0085] PG1 is tert-butoxycarbonyl (Boc), benzyloxycarbonyl (Cbz), fluorenylmethoxycarbonyl (Fmoc) or H;

[0086] PG2 is 9-fluorenylmethyl (Fm), benzyl (Bz) or tert-butyl (tBu).

[0087] Using a methanol or tetrahydrofuran solution containing sodium methoxide as a shearing agent, compound C is sheared to remove the compound of formula (I) to obtain compound D; then, using a cocktail solution of trifluoroacetic acid as a side-chain deprotecting agent for compound D, the protecting groups on the side chain are removed to obtain the trifluoroacetate E of aspartame;

[0088] In this example, a methanol or tetrahydrofuran solution containing 10-15% sodium methoxide is used as the shearing agent. First, the DPXP auxiliary group is removed by shearing and separated by the assisted precipitation method. The filter cake is the crude DPXP. The filtrate is concentrated by rotary evaporation to remove the solvent to obtain compound D (PG1-Asp(OPG2)-Phe-OMe). Then, using a cocktail solution of trifluoroacetic acid as the side-chain deprotecting agent, the reaction conditions are stirring at 5-30 °C for 1-3 hours to remove the protecting groups such as tBu and Boc on the side chain. After separation and purification, the trifluoroacetate E of aspartame (TFA*H-Asp-Phe-OH) is obtained; the component ratio in the cocktail solution of trifluoroacetic acid is: TFA / TIPS / H2O = 95:2.5:2.5.

[0089] Among them, the structural general formula of compound D (PG1-Asp(OPG2)-Phe-OMe) is:

[0090] ;

[0091] PG1 is tert-butoxycarbonyl (Boc), benzyloxycarbonyl (Cbz), fluorenylmethoxycarbonyl (Fmoc) or H;

[0092] PG2 is Fm, Bz or tBu.

[0093] It should be noted that the obtained crude DPXP is dissolved in an appropriate amount of ethyl acetate, and a paraffin or ether solvent with low polarity is added. By virtue of the characteristic that DPXP is easily crystallized and precipitated in different solvent systems, DPXP can be separated from other impurities; the separated DPXP is filtered, washed or recrystallized to obtain purified DPXP, which can be reused directly or after regeneration as an auxiliary group.

[0094] The trifluoroacetate E of aspartame is neutralized with sodium bicarbonate, the pH is adjusted to 8-9, extracted with ethyl acetate, precipitated, filtered, washed with ethyl acetate and dried to obtain the pure product F of aspartame (H-Asp-Phe-OMe);

[0095] Among them, formula (I) is , X is O, or .

[0096] A method for preparing aspartame assisted by diphenylphosphinyloxy-X-phenol compounds provided by the present invention, compared with the existing synthesis methods, combines the advantages of liquid-phase and solid-phase synthesis methods, can synthesize and prepare aspartame more simply, quickly, economically and efficiently, and the DPXP carrier can be recycled and directly reused, reducing waste of raw materials, reducing waste pollution, saving costs and being environmentally friendly.

[0097] The present invention is applicable to the synthesis, preparation, shearing and removal of aspartame-DPXP, and the reaction principle and technical route are as follows:

[0098] First, the synthesized DPXP is used to assist the synthesis of aspartame. By coupling DPXP with N-terminal protected phenylalanine (PG-Phe-OH) and N-terminal and side-chain protected aspartic acid (PG1-Asp(OtBu)-OH) in sequence, an aspartame derivative is synthesized. Then, through the shearing, methylation and removal of side-chain groups of the carrier, a suitable route is explored, and finally aspartame is obtained to verify the application and recyclability of DPXP in peptide synthesis.

[0099] The specific synthesis route of the scheme is as follows:

[0100]

[0101] Or

[0102]

[0103] X is O, or ; PG1 is tert-butoxycarbonyl (Boc), benzyloxycarbonyl (Cbz), fluorenylmethoxycarbonyl (Fmoc) or H; PG2 is Fm, Bz or tBu.

[0104] In the present invention, the easily removable Boc group is selected to make Boc-Asp-OH into a protected succinic anhydride, and then it reacts with phenylalanine methyl ester to generate an aspartame precursor. Finally, the Boc group is removed in a 25% TFA / DCM system to obtain the final product. The synthesis route is as follows:

[0105]

[0106] Finally, the present invention designs a two-step method for synthesizing aspartame. Using phenylalanine methyl ester, it couples with Boc-Asp(OtBu)-OH in a DIC / TEA system, and finally the protecting group is removed to obtain aspartame. The synthesis route is as follows:

[0107]

[0108] Among them, Boc-Asp-OH represents aspartic acid protected as N-tert-butoxycarbonyl-aspartic acid, and then treated with acetic anhydride as a dehydrating agent. Boc-Asp(OtBu)-OH represents N-tert-butoxycarbonyl-O-tert-butyl aspartic acid.

[0109] The abbreviations involved in the present invention have the following meanings:

[0110] APM: Aspartame; Boc: tert-butoxycarbonyl; Cbz: Benzyloxycarbonyl; DCM: Dichloromethane CH2Cl2; DEA: Diethylamine; DMAP: 4-Dimethylaminopyridine; DMF: N,N-Dimethylformamide; DPBP: 4-Diphenylphosphinoxylbenzoylphenol; DPBPA: 4-Diphenylphosphinoxyl Bisphenol A; DPOP: 4-Diphenylphosphinoxyl phenol; DPXP: 4-Diphenylphosphino-X-phenol; EDC-HCl: 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; Fmoc: 9-Fluorenylmethoxycarbonyl; HATU: 2-(7-Azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate; HOBT: 1-Hydroxybenzotriazole; HBTU: O-Benzotriazol-1-yl-N,N,N',N'-tetramethyluronium hexafluorophosphate; NMM: N-Methylmorpholine; NMP: N-Methylpyrrolidone; PyBop: Benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate; TEA: Triethylamine; TFA: Trifluoroacetic acid; THF: Tetrahydrofuran; TIPS: Triisopropylsilane.

[0111] The following examples provide specific synthesis methods for preparing the above compounds and the corresponding intermediate compounds.

[0112] Example 1

[0113] The preparation method of 4-(Diphenylphosphinoxyl)phenol (DPOP, 1) includes:

[0114] Accurately weigh 3.30 g (30 mmol, 1 eq) of hydroquinone and place it in a 150 mL round-bottom flask. Add tetrahydrofuran solution to dissolve it. Seal the flask and place it in an ice bath, stir with a magnetic stirrer for 10 min to lower the temperature of the system to the lowest. Slowly add 5 mL (36 mmol, 1.2 eq) of triethylamine, continue stirring for 20 min, and the solution turns orange-red. Add the diluted diphenylphosphinous chloride dropwise in 4 batches, a total of about 5.7 mL (30 mmol, 1 eq) is added dropwise. During the addition process, precipitation gradually occurs and white smoke emerges from the bottle mouth. At the same time, perform TLC monitoring (developing agent: DCM:MeOH = 15:1). Stop the reaction after about 1.5 h, and the solution turns purple. Filter to remove the salt formed by triethylamine and most of the by-products, concentrate the filtrate under reduced pressure to remove the solvent, add 80 mL of dichloromethane to dissolve the reaction product, wash it 3 times with saturated NaHCO3 solution, and dry it with anhydrous Na2SO4. After concentration under reduced pressure, recrystallize with ethyl acetate to separate and obtain 8.28 g of the product DPOP, which is a white powder with a yield of 89%.

[0115] The synthesis route is as follows:

[0116]

[0117] Structural characterization data of p-diphenylphosphoryloxyphenol (DPP, 1): 1 H NMR (400 MHz, DMSO- d 6) δ9.32 (s, 1H), 7.88 (dd, J = 12.1, 7.2 Hz, 4H), 7.64 – 7.50 (m, 6H), 7.05 (d, J =8.5 Hz, 2H), 6.65 (d, J = 8.8 Hz, 2H); 13 C NMR (101 MHz, DMSO- d 6) δ 154.60,143.24, 133.05, 133.02, 131.94, 130.81, 129.35, 129.22, 121.99, 121.84,116.23; 31 P NMR (162 MHz, DMSO- d 6) δ 28.77; HRMS (ESI) m / z calcd for C 18 H 16 O3P + (M+H) +311.08316, found 311.08282.

[0118] Example 2

[0119] The preparation method of 4-(4'-diphenylphosphinyloxy)benzoyl phenol (DPBP, 2) includes:

[0120] Accurately weigh 2.14 g (10 mmol, 1 eq) of 4,4-dihydroxybenzophenone and put it into a 150 mL round-bottom flask, add 80 mL of tetrahydrofuran to dissolve. Seal and place it in an ice bath and stir for 10 min to lower the system temperature to the lowest. Slowly add dropwise 1.7 mL (12 mmol, 1.2 eq) of triethylamine, continue to stir for 20 min, add dropwise the diluted diphenylphosphinous chloride 0.5 mL in 4 batches, a total of 1.9 mL (10 mmol, 1 eq) is added dropwise, and TLC monitoring is carried out (developing agent: DCM:MeOH = 15:1). A large amount of white smoke is generated at the bottle mouth during the dropping process. Stop the reaction after about 3 h (part of the raw materials are not reacted). Filter to remove the salt formed by triethylamine, concentrate under reduced pressure to remove the solvent in the filtrate, add 50 mL of ethyl acetate to dissolve the reaction product and wash it 3 times with 30 mL of saturated NaHCO3 solution, dry it with anhydrous Na2SO4, and concentrate under reduced pressure again to remove the solvent. The product DPBP 3.31 g is obtained by recrystallization purification with methanol. The product is a pale yellow foamy solid with a yield of 80%.

[0121] The synthetic route is as follows:

[0122]

[0123] The structure characterization data of 4-(4'-diphenylphosphinyloxy)benzoyl phenol (DPBP, 2): 1 H NMR (400MHz, DMSO- d 6) δ 10.42 (s, 1H), 7.95 (dd, J = 11.9, 7.6 Hz, 4H), 7.72 – 7.55 (m,10H), 7.44 (d, J = 8.3 Hz, 2H), 6.88 (d, J = 8.6 Hz, 2H); 13 C NMR (101 MHz, DMSO- d 6) δ 193.47, 162.42, 153.87, 134.83, 133.41 (d, J= 2.6 Hz), 132.87, 132.25 –131.36 (m), 130.28, 129.49 (d, J = 13.2 Hz), 128.23, 121.11 – 120.33 (m),115.72; 31 P NMR (202 MHz, DMSO- d 6) δ 7.58; HRMS (ESI) m / z calcd for C 25 H 20 O4P + (M+H) + 415.10937, found 415.10959.

[0124] Example 3

[0125] A preparation method of bisphenol A bis(diphenylphosphate) (DPBPA, 3) includes:

[0126] Accurately weigh 6.85 g (30 mmol, 1 eq) of bisphenol A and place it into a 150 mL round-bottom flask, then add 80 mL of tetrahydrofuran to dissolve. Seal it and stir in an ice bath for 10 min to lower the system temperature to the lowest. Slowly add 5.1 mL (36 mmol, 1.2 eq) of triethylamine dropwise to the solution, and continue stirring for 20 min. Dilute 5.7 mL (30 mmol, 1 eq) of diphenylphosphinous chloride 4 times with tetrahydrofuran, and slowly add it dropwise to the reaction system in four batches, controlling the formation of disubstituted products as much as possible, and monitor the reaction process by TLC throughout. Stop the reaction after about 1.5 h (part of the raw materials are unreacted). Filter the mixture, concentrate it under reduced pressure to remove the solvent in the filtrate, then add 80 mL of dichloromethane to dissolve the reaction product and wash it 3 times with 40 mL of saturated NaHCO3 solution to remove the salts formed during the reaction, dry it with anhydrous Na2SO4, and concentrate it under reduced pressure again to remove the solvent. Finally, purify it by recrystallization with ethyl acetate and dry it under vacuum to obtain 11.56 g of product DPBPA as white crystals, with a yield of 90%. Developing agent: DCM:MeOH = 15:1.

[0127] The synthesis route is as follows:

[0128]

[0129] Structure characterization data of bisphenol A bis(diphenylphosphate) (DPBPA, 3): 11H NMR (400 MHz, DMSO-d6) δ 9.18 (s, 1H), 7.97 – 7.84 (m, 4H), 7.66 – 7.51 (m, 6H), 7.13 (s, 4H), 6.94 (d, J J = 8.6 Hz, 2H), 6.64 (d, J J = 8.6 Hz, 2H), 1.52 (s, 6H); 13 13C NMR (101 MHz, DMSO- d d6) δ 155.51, 148.66, 147.58, 140.67, 133.15, 132.16, 131.96, 130.80, 129.45, 128.23, 127.74, 120.32, 115.11, 31.04; 31 31P NMR (162 MHz, DMSO- d d6) δ 30.05; HRMS (ESI) m / z calcd for C 27 24 26 H + 17 + O3P (M+H)+ 429.16141, found 429.16174.

[0130] Example 4

[0131] Using the method for preparing aspartame assisted by p-(diphenylphosphoryloxy)phenol (DPOP) carrier provided in Example 1, which includes:

[0132] (1) Synthesis of tert-butoxycarbonyl-phenylalanyl-p-(diphenylphosphoryloxy)phenyl ester (Boc-Phe-DPOP)

[0133] Accurately weigh 2.72 g (14.20 mmol, 1.2 eq) of EDCI, 0.17 g (1.42 mmol, 0.12 eq) of DMAP, and 3.68 g (14.20 mmol, 1.2 eq) of Boc-Phe-OH and put them into a 100 mL round-bottom flask. Add 30 mL of DCM to completely dissolve them. Immerse the reaction system in an ice-water bath for activation for 0.5 h. Add 3.67 g (11.83 mmol, 1 eq) of p-diphenylphosphoryloxyphenol (DPOP) to the system. Then remove the ice-water bath and react at room temperature. Monitor the whole process by TLC. The carrier reaction is complete in about 1.5 h. After the reaction is completed, concentrate under reduced pressure to remove DCM. Then add 50 mL of ethyl acetate to completely dissolve the reaction mixture. Wash it successively with 30 mL of saturated NH4Cl solution, water, saturated NaHCO3 solution, and water three times. Dry it with anhydrous Na2SO4, concentrate under reduced pressure to remove ethyl acetate, and dry it under vacuum to obtain 6.46 g of white solid Boc-Phe-DPOP with a yield of 98%. Developing agent: PE:EA = 1:1.

[0134] Structure characterization data of Boc-Phe-DPOP: 1 H NMR (400 MHz, DMSO- d 6) δ 7.95 – 7.88 (m,4H), 7.66 – 7.53 (m, 7H), 7.34 – 7.29 (m, 6H), 7.24 (q, J = 4.6 Hz, 1H), 6.97 –6.90 (m, 2H), 4.40 – 4.30 (m, 1H), 3.14 – 2.98 (m, 2H), 1.35 (s, 9H); 13 C NMR(101 MHz, DMSO- d 6) δ 171.47, 155.96, 148.58, 147.23, 137.68, 133.32, 131.92,131.72, 130.37, 129.71, 129.36, 128.75, 127.06, 123.20, 122.01, 79.01, 55.93,36.67, 28.56; 31 P NMR (162 MHz, DMSO- d 6) δ 29.79.

[0135] (2) Synthesis of phenylalanyl-(p-diphenylphosphoryloxy)phenyl ester (H-Phe-DPOP)

[0136] Take 3.61 g of Boc-Phe-DPOP and place it in a 100 mL round-bottom flask. Add 15 mL of DCM to dissolve it completely. Place the system in an ice-water bath and stir for 10 min to lower the system temperature to the lowest. Slowly add dropwise 5 mL of trifluoroacetic acid (V DCM :V TFA = 3:1). After the addition is complete, remove the ice-water bath and react at room temperature. Monitor by TLC (developing solvent: PE:EA = 1:1). The deprotection is complete in about 1 h. After the reaction is completed, concentrate under reduced pressure at room temperature to remove DCM and TFA, and add DCM multiple times for concentration under reduced pressure to remove TFA to the greatest extent. It should be noted that since the product after de-Boc is unstable, it should be immediately put into the next reaction without further purification. After concentration under reduced pressure, 2.90 g of white solid is obtained, and the yield is 98%.

[0137] Structure characterization data of H-Phe-DPOP: 1 H NMR (400 MHz, DMSO- d 6) δ 8.89 (s, 2H),7.93 (dd, J = 12.2, 7.3 Hz, 4H), 7.65 – 7.51 (m, 6H), 7.39 – 7.28 (m, 7H), 6.96(d, J = 8.9 Hz, 2H), 4.58 (t, J = 6.5 Hz, 1H), 3.36 (dd, J = 13.9, 5.9 Hz, 1H),3.22 (dd, J = 13.8, 8.2 Hz, 1H); 13 C NMR (101 MHz, DMSO- d 6) δ 168.33, 148.91,146.41, 135.00, 133.29, 131.99, 130.30, 129.98, 129.31, 129.14, 127.86,122.99, 122.19, 117.87, 114.96, 53.91, 36.62; 31 P NMR (162 MHz, DMSO- d 6) δ30.11.

[0138] (3)Synthesis of 9-fluorenylmethoxycarbonyl-(O-tert-butyl)aspartyl-phenylalanyl-(p-diphenylphosphinyloxy)phenyl ester (Fmoc-Asp(OtBu)-Phe-DPOP)

[0139] Accurately weigh 1.22 g (6.35 mmol, 1.2 eq) of EDCI, 0.86 g (6.35 mmol, 1.2 eq) of HOBt, and 2.61 g (6.35 mmol, 1.2 eq) of Fmoc-Asp(OtBu)-OH and add them successively to a 100 mL round-bottom flask. Add 30 mL of DCM to completely dissolve them, seal and stir in an ice bath for activation for 0.5 h. Add 2.42 g (5.29 mmol, 1.0 eq) of H-Phe-DPP and 435 μL (2.65 mmol, 0.5 eq) of DIEA to the activation solution, and place it at room temperature for reaction for 2 h. Monitor the reaction process by TLC. After the reaction is completed, concentrate under reduced pressure to remove dichloromethane, then add 50 mL of ethyl acetate to dissolve the reaction mixture, and wash it successively with 30 mL of saturated NH4Cl solution, distilled water, saturated NaHCO3 solution, and distilled water 3 times, and dry it with anhydrous Na2SO4. Precipitate with dichloromethane and methyl tert-butyl ether (V DCM / V MTBE = 1:8), and separate and purify to obtain 3.37 g of white solid, with a yield of 75%.

[0140] Structural characterization data of Fmoc-Asp(OtBu)-Phe-DPOP: 1 H NMR (400 MHz, DMSO-d6) δ8.62 (d, J = 6.6 Hz, 1H), 7.94 (dq, J = 8.4, 5.0, 3.2 Hz, 6H), 7.75 (dd, J =7.4, 2.7 Hz, 2H), 7.71 – 7.64 (m, 3H), 7.62 – 7.56 (m, 4H), 7.46 (t, J = 7.5Hz, 2H), 7.38 – 7.23 (m, 9H), 7.00 – 6.91 (m, 2H), 4.66 – 4.23 (m, 5H), 3.15(d, J = 8.0 Hz, 2H), 2.64 (dd, J = 16.1, 4.6 Hz, 1H), 2.48 (dd, J = 16.2, 9.7Hz, 1H), 1.38 (s, 9H); 13 C NMR (101 MHz, DMSO- d6) δ 171.65, 170.56, 169.57, 156.21, 148.58, 148.51, 147.16, 144.26, 144.18, 141.17, 137.22, 133.31, 133.28, 132.02, 131.91, 131.69, 130.33, 129.71, 129.48, 129.35, 128.79, 128.12, 127.17, 125.73, 123.21, 121.93, 120.58, 80.66, 66.22, 55.38, 54.63, 47.04, 37.85, 36.58, 28.12; 31 1P NMR (162 MHz, DMSO- d 6) δ 29.77.

[0141] (4) Synthesis of 9-Fluorenylmethoxycarbonyl-O-tert-butyl-aspartyl-phenylalanine (Fmoc-Asp(OtBu)-Phe-OH)

[0142] Accurately weigh 2.43 g (2.86 mmol, 1.0 eq) of Fmoc-Asp(OtBu)-Phe-DPP and place it in a 100 mL round-bottom flask. Add 20 ml of tetrahydrofuran to dissolve it completely. Take 0.21 g of LiOH (8.56 mmol, 3.0 eq) and dissolve it in 2 mL of distilled water (V THF :V H2O =10:1). Dropwise add the LiOH solution at room temperature and monitor by TLC. After about 10 min, the raw materials are completely consumed and the solution gradually changes from colorless to dark brown. Concentrate the mixture under reduced pressure to remove tetrahydrofuran, add 5 mL of distilled water to dissolve it, and centrifuge with ethyl acetate 3 times. Concentrate the organic phase to obtain 718 mg of the carrier DPP with a yield of 81%. Adjust the pH of the aqueous phase to 6 by dropwise adding 0.01 mol / L HCl, the solution gradually becomes turbid, and extract with ethyl acetate to obtain the product. Concentrate under reduced pressure to remove the solvent and dry in vacuo to obtain 748 mg of a pale yellow solid with a yield of 60%. Developing agent: PE:EA = 1:1.

[0143] Monitoring situation by TLC during the reaction: On the TLC plate, the left is the spot of the DPP carrier, the middle is the reaction system, and the right is the spot of the raw material. Among them, spot 1 is fluorenylene, spot 2 is the raw material, spot 3 is the carrier, and there are also two relatively faint spots between spot 1 and spot 2. Since some fluorenylene is produced during the reaction, it proves that some raw materials have removed the Fmoc group or removed the Fmoc group and the carrier simultaneously, thus reducing the yield.

[0144] Structural characterization data of Fmoc-Asp(OtBu)-Phe-OH: 1 H NMR (400 MHz, DMSO- d 6) δ 7.89(dd, J J = 7.3, 3.7 Hz, 2H), 7.78 (d, J J = 8.6 Hz, 1H), 7.70 (t, J J = 9.2 Hz, 2H), 7.42(t, J J = 6.7 Hz, 2H), 7.36 – 7.29 (m, 2H), 7.21 – 7.08 (m, 4H), 4.35 (dq, J J =27.4, 9.9, 9.3 Hz, 4H), 4.26 – 4.18 (m, 2H), 3.18 – 3.07 (m, 1H), 2.97 (dq, J J =19.4, 7.6, 7.1 Hz, 1H), 2.69 (dd, J J = 16.0, 4.5 Hz, 1H), 2.40 (ddd, J J = 32.6,15.9, 9.7 Hz, 1H), 1.36 (s, 9H); 13 C NMR (101 MHz, DMSO- d 6) δ 170.32, 169.91,156.27, 144.16, 138.53, 129.94, 128.25, 127.54, 125.74, 120.54, 80.52, 66.36,54.94, 52.12, 47.05, 39.32, 28.13; HRMS (ESI) m / z calcd for C 32 H 34 N2O7Na + (M+Na) + 581.22582, found 581.22577.

[0145] (5)Synthesis of N-9-fluorenylmethoxycarbonyl-O-tert-butyl-aspartyl-phenylalanine methyl ester (Fmoc-Asp(OtBu)-Phe-OCH3)

[0146] Take 422 mg (0.72 mmol, 1 eq) of Fmoc-Asp(OtBu)-Phe-OH, 275 mg (1.44 mmol, 2 eq) of EDCI, and 18 mg (0.14 mmol, 0.2 eq) of DMAP. Add dichloromethane to dissolve them completely, place the solution in an ice-water bath for activation for 0.5 h, and then add a large excess of anhydrous methanol to the activated solution. React at room temperature for 2 h. After the reaction is complete, concentrate the solution under reduced pressure to remove the solvent, add 20 mL of ethyl acetate to dissolve the residue, wash it successively with saturated NH4Cl solution and distilled water three times, and dry it with anhydrous Na2SO4. Concentrate the solution again under reduced pressure to remove the solvent, and dry it in vacuo to obtain 369 mg of a white solid with a yield of 90%. The eluent is PE:EA = 2:1.

[0147] Structure characterization data of Fmoc-Asp(OtBu)-Phe-OCH3: 1 H NMR (400 MHz, DMSO-d6) δ 8.31(dd, J J = 24.8, 7.6 Hz, 1H), 7.89 (d, J J = 7.5 Hz, 2H), 7.72 (d, J J = 6.3 Hz, 2H),7.63 – 7.55 (m, 1H), 7.42 (t, J J = 7.3 Hz, 2H), 7.32 (t, J J = 7.3 Hz, 2H), 7.26 –7.17 (m, 5H), 4.51 – 4.22 (m, 5H), 3.60 (d, J J = 11.4 Hz, 3H), 3.01 (ddq, J J =35.1, 18.3, 9.5, 7.3 Hz, 2H), 2.61 (dd, J J = 16.0, 4.3 Hz, 1H), 2.43 (dd, J J =15.9, 7.0 Hz, 1H), 2.30 (dd, J J = 15.7, 10.0 Hz, 1H), 1.38 (d, J J = 18.8 Hz, 9H); 13 C NMR (101 MHz, DMSO- d6) δ 172.16, 171.31, 171.07, 169.60, 156.17, 144.27, 144.20, 141.17, 137.49, 137.42, 129.59, 129.50, 128.63, 128.11, 127.52, 127.01, 125.73, 120.57, 80.56, 66.24, 55.37, 54.16, 53.93, 52.38, 51.73, 51.62, 47.06, 38.07, 37.91, 37.21, 36.94, 28.14; HRMS (ESI) m / z calcd for C 33 H 36 N2O7Na + (M+Na) + 595.24147, found 595.24078.

[0148] (6) Synthesis of Aspartame

[0149] Take the methyl esterified product and remove the Fmoc and OtBu groups by one-pot method. First, add 6 mL of MeCN to dissolve it completely, stir at room temperature, and dropwise add 2 mL of diethylamine (V DEA :V MeCN =3:1). Monitor by TLC for about 15 min until the raw materials are completely consumed. Concentrate under reduced pressure to remove acetonitrile and diethylamine. Then add 9.5 mL of TFA to dissolve it, stir at room temperature, and slowly dropwise add 0.5 mL of H2O. Monitor by TLC (developing solvent: DCM:MeOH = 10:1). The raw materials are completely consumed in 1 h. Concentrate under reduced pressure to remove the solvent, and add DCM several times and concentrate under reduced pressure to remove TFA. Add 1 mL of methanol to dissolve the reaction mixture, transfer it to a centrifuge tube, and dropwise add cold ether while ultrasonically irradiating. When about 6 mL is added, a white solid is produced. Centrifuge to obtain a white powder, wash it 3 times with cold ether to obtain the product.

[0150] Structure characterization data of APM: HRMS (ESI) m / z calcd for C 14 H 19 N2O5 + (M+H) + 295.12885, found 295.12897.

[0151] Due to the selection of N-(9-fluorenylmethoxycarbonyl)-O-tert-butyl aspartic acid (Fmoc-Asp(OtBu)-OH) for the reaction, when the carrier is cleaved later, since the Fmoc group is sensitive to base, partial removal will occur, resulting in a reduction in yield. Therefore, N-tert-butoxycarbonyl-O-tert-butyl aspartic acid (Boc-Asp(OtBu)-OH), which is stable to base, is used to improve the experimental protocol. While increasing the yield, the Boc group and the OtBu group can be removed simultaneously in a 95% TFA system, further simplifying the experimental procedure.

[0152] Example 5

[0153] Same as Example 4, except that:

[0154] Synthesis of N-tert-butoxycarbonyl-O-tert-butyl-aspartyl-phenylalanyl-(p-diphenylphosphoryloxy)phenyl ester (Boc-Asp(OtBu)-Phe-DPOP) in step (3)

[0155] Precisely weigh 1.43 g (7.48 mmol, 1.2 eq) of EDCI, 1.01 g (7.48 mmol, 1.2 eq) of HOBt, and 2.16 g (7.48 mmol, 1.2 eq) of Boc-Asp(OtBu)-OH and add them to a 100 mL round-bottom flask in sequence. Add 30 mL of DCM to completely dissolve them, seal and stir for activation in an ice bath for 0.5 h. Add 2.85 g (6.23 mmol, 1.0 eq) of H-Phe-DPP and 513 μL (3.12 mmol, 0.5 eq) of DIEA to the activated solution, and place it at room temperature for reaction for 2 h. Monitor the reaction process by TLC. After the reaction is completed, concentrate under reduced pressure to remove dichloromethane, then add 50 mL of ethyl acetate to dissolve the reaction mixture, and wash it 3 times with 30 mL of saturated NH4Cl solution, distilled water, saturated NaHCO3 solution, and distilled water in sequence, and dry it with anhydrous Na2SO4. Concentrate under reduced pressure and precipitate with dichloromethane and methyl tert-butyl ether (V DCM / V MTBE = 1:10) to obtain 3.90 g of white solid Boc-Asp(OtBu)-Phe-DPOP, with a yield of 86%.

[0156] Structure characterization data of Boc-Asp(OtBu)-Phe-DPOP: 1 H NMR (400 MHz, DMSO- d 6) δ 8.45(d, J= 6.7 Hz, 1H), 7.95 – 7.88 (m, 4H), 7.65 – 7.60 (m, 2H), 7.56 (td, J = 7.4, 3.7 Hz, 4H), 7.28 (dt, J = 8.9, 4.6 Hz, 7H), 7.07 (d, J = 8.5 Hz, 1H), 6.93 (dd, J = 25.2, 8.9 Hz, 2H), 4.62 – 4.53 (m, 1H), 4.35 (td, J = 9.0, 4.6 Hz, 1H), 3.11(d, J = 7.2 Hz, 2H), 2.41 – 2.32 (m, 2H), 1.35 (d, J = 2.0 Hz, 18H); 13 C NMR (101MHz, DMSO- d 6) δ 171.78, 170.53, 169.65, 155.48, 148.51, 147.17, 137.28, 133.31, 132.03, 131.93, 131.71, 129.75, 129.48, 129.35, 128.79, 127.16, 123.29, 121.92, 121.88, 80.53, 78.66, 51.22, 37.98, 36.60, 28.61, 28.11.

[0157] Step (4) Synthesis of Boc-Asp(OtBu)-Phe-OH

[0158] Accurately weigh 1.05 g (1.44 mmol, 1.0 eq) of Boc-Asp(OtBu)-Phe-DPOP and place it in a 100 mL round-bottom flask. Add 20 mL of tetrahydrofuran to dissolve it completely. Take 0.11 g of LiOH (4.30 mmol, 3.0 eq) and dissolve it in 2 mL of distilled water (V THF :V H2O= 10:1), LiOH solution was added dropwise at room temperature, and monitored by TLC (developing solvent: PE:EA = 1:1). After about 10 minutes, the reaction was complete, and the solution gradually changed from colorless to dark brown. The mixture was concentrated under reduced pressure to remove THF, 5 mL of distilled water was added to dissolve it, and centrifuged with ethyl acetate 3 times. The organic phase was concentrated to obtain 362 mg of the carrier DPP, with a yield of 81%. 0.1 mol / L HCl was added dropwise to the aqueous phase to adjust the pH to 2, the solution gradually became turbid, and the product was obtained by extraction with ethyl acetate, concentrated under reduced pressure, and dried in vacuo to obtain 503 mg of a pale yellow solid, with a yield of 80%.

[0159] Structural characterization data of Boc-Asp(OtBu)-Phe-OH: 1 H NMR (400 MHz, DMSO-d6) δ 7.44 –7.59 (m,2H), 7.32 – 7.07 (m, 6H), 4.27 (ddd, J = 17.5, 8.8, 5.0 Hz, 2H), 3.07(dd, J = 13.3, 4.6 Hz, 1H), 2.96 – 2.88 (m, 1H), 2.59 (dd, J = 15.8, 4.7 Hz, 1H),2.37 – 2.26 (m, 1H), 1.41 – 1.32 (m, 18H); 13 C NMR (101 MHz, DMSO- d 6) δ 174.12,175.76, 170.00, 155.50, 138.65 (d, J = 5.3 Hz), 130.35, 129.47 128.57, 128.25,126.37, 80.41, 78.72, 54.92, 51.86, 38.16, 37.44, 28.63, 28.13.

[0160] Step (5) Synthesis of N-tert-butoxycarbonyl-O-tert-butyl aspartyl-phenylalanine methyl ester Boc-Asp(OtBu)-Phe-OCH3

[0161] Take 496 mg (1.14 mmol, 1 eq) of Boc-Asp(OtBu)-Phe-OH, 436 mg (2.28 mmol, 2 eq) of EDCI, and 28 mg (0.23 mmol, 0.2 eq) of DMAP. Add dichloromethane to dissolve them thoroughly, place the solution in an ice-water bath for activation for 0.5 h, and then add an excess of anhydrous methanol to the activated solution. React at room temperature for 2 h. After the reaction is complete, concentrate the solution under reduced pressure to remove the solvent, add 20 mL of ethyl acetate to dissolve, wash successively with saturated NH4Cl solution and distilled water three times, and dry with anhydrous Na2SO4. Concentrate under reduced pressure to remove the solvent to obtain 486 mg of a colorless viscous solid with a yield of 95%.

[0162] Structural characterization data of Boc-Asp(OtBu)-Phe-OCH3: 1 1H NMR (400 MHz, DMSO- d 6) δ 8.19(s, 1H), 7.31 – 7.16 (m, 5H), 7.02 (dd, J J = 14.2, 8.6 Hz, 1H), 4.47 (dt, J J =14.8, 7.7 Hz, 1H), 4.31 (dt, J J = 8.4, 4.1 Hz, 1H), 3.60 (d, J J = 14.1 Hz, 3H),2.98 (dtd, J J = 34.6, 13.6, 7.3 Hz, 2H), 2.47 – 2.20 (m, 2H), 1.38 (d, J J = 5.1 Hz,18H); 13 13C NMR (101 MHz, DMSO- d 6) δ 172.14, 171.43, 171.25, 169.67, 129.58,128.67, 127.04, 80.50, 80.43, 78.69, 78.67, 53.87, 52.39, 52.33, 51.30,40.18, 39.97, 39.76, 38.10, 37.18, 28.62, 28.11.

[0163] Step (6) Synthesis of aspartame

[0164] Dissolve Boc-Asp(OtBu)-Phe-OCH3 in 9.5 mL of trifluoroacetic acid, stir at room temperature, slowly add dropwise 0.5 mL of H2O, monitor by TLC, the raw materials react completely in about 1 h, concentrate under reduced pressure to remove the solvent, and add dichloromethane multiple times and concentrate under reduced pressure to remove trifluoroacetic acid. Add 1 mL of methanol to dissolve the reaction mixture, transfer it to a centrifuge tube, add cold ether dropwise while ultrasonicating, and a white solid is produced when about 6 mL is added. Centrifuge to obtain a white powder, wash it 3 times with cold ether and centrifuge to obtain aspartame with a yield of 93%.

[0165] Structural characterization data of APM: 1 H NMR (400 MHz, DMSO- d 6) δ 8.95 (dd, J = 16.4, 7.8Hz, 1H), 7.34 – 7.19 (m, 5H), 4.64 – 4.50 (m, 1H), 4.05 (d, J = 6.1 Hz, 1H),3.63 (d, J = 11.2 Hz, 3H), 3.09 (dt, J = 11.7, 5.6 Hz, 1H), 2.98 – 2.82 (m, 1H),2.80 – 2.66 (m, 1H), 2.51 (s, 1H); 13 C NMR (101 MHz, DMSO- d 6) δ 171.75, 171.42,168.66, 168.25, 137.28, 129.57, 128.84, 128.75, 127.19, 54.50, 53.96, 52.58,49.24, 37.24, 36.75, 35.92, 35.87; HRMS (ESI) m / z calcd for C 14 H 19 N2O5 + (M+H) + 295.12885, found 295.12858.

[0166] The analytical conditions for reverse-phase high-performance liquid chromatography (RP-HPLC) were as follows: The sample used a water-acetonitrile gradient elution mobile phase, was dissolved in methanol, and prepared into a 2 mg / mL solution. Mobile phase A was an aqueous solution of 0.1% TFA, mobile phase B was an acetonitrile solution of 0.1% TFA, the flow rate was 1 mL / min, the ultraviolet detection wavelength (λ) was 215 nm, and the elution gradient was 10 - 90% solvent B. The HPLC analysis results of the aspartame product are shown in Figure 1 , with a purity of 97.3%, few impurities, easy to purify, no presence of the β-isomer of aspartame was observed, and the product had high quality.

[0167] Example 6

[0168] A preparation method of aspartame, comprising:

[0169] (1) Synthesis of Boc-aspartic anhydride

[0170] Acetic anhydride (3.0 mL) was added to Boc-Asp-OH (15 mmol), and the mixture was stirred at 50 °C for 3 h. The remaining acetic anhydride was removed by concentration under reduced pressure at 80 °C. After vacuum drying, the target product was obtained as a white solid with a yield of 91%.

[0171] Structure characterization data of Boc-aspartic anhydride: 1 H NMR (400 MHz, DMSO- d 6) δ 7.75 (d, J = 7.7 Hz, 1H), 4.67 – 4.54 (m, 1H), 3.27 – 3.19 (m, 1H), 2.84 (dd, J = 18.4, 6.2 Hz,1H), 1.38 (s, 9H); 13 C NMR (101 MHz, DMSO- d 6) δ 172.85, 170.48, 155.69, 80.05,35.33, 28.46; HRMS (ESI) m / z calcd for C9H 13 NO5Na + (M+Na) + 238.06859, found238.06834.

[0172] (2) Synthesis of Boc-Asp-Phe-OCH3

[0173] 1 g (4.6 mmol, 1 eq) of Boc-aspartic anhydride was dissolved in 10 mL of dichloromethane, 0.78 mL (5.52 mmol, 1.2 eq) of triethylamine was added dropwise, and 0.834 g (4.6 mmol, 1 eq) of phenylalanine methyl ester hydrochloride was quickly added. The mixture was stirred at room temperature and monitored by TLC (developing solvent: DCM:MeOH = 20:1). The reaction was completed in about 6 h. The solvent was rotary evaporated in vacuo, 20 mL of ethyl acetate was added, and the mixture was washed three times with water and dried over anhydrous Na2SO4. The product (0.88 g) was obtained by column chromatography with a yield of 51%.

[0174] Structural characterization data of Boc-Asp-Phe-OCH3: 1 1H NMR (400 MHz, DMSO- d 6) δ 12.32 (s,1H), 8.11 (dd, J J = 15.7, 7.8 Hz, 1H), 7.30 – 7.17 (m, 5H), 7.01 (dd, J J = 11.6,8.3 Hz, 1H), 4.48 (dt, J J = 13.9, 6.5 Hz, 1H), 4.28 (dq, J J = 8.6, 4.4 Hz, 1H),3.60 (d, J J = 13.8 Hz, 3H), 3.08 – 2.85 (m, 2H), 2.48 – 2.29 (m, 1H), 1.37 (s,9H); 13 13C NMR (101 MHz, DMSO- d 6) δ 172.15, 155.59, 137.39, 129.51, 128.70,127.03, 78.70, 55.36, 54.02, 52.32, 37.21, 37.03, 36.61, 28.62; HRMS (ESI) m / z calcd for C 19 18H 26 N2O7Na + (M+Na) + 417.16322, found 417.16367.

[0175] (3) Synthesis of aspartame

[0176] Take Boc-Asp-Phe-OCH3, dissolve it in 9 mL of dichloromethane, stir in an ice bath to lower the system temperature to the lowest, then add dropwise 3 mL of trifluoroacetic acid (V DCM / V TFA = 3:1), remove the ice-water bath and stir at room temperature. Monitor by TLC (developing solvent: DCM:MeOH = 10:1). The reaction is completed in about 1.5 h. Add dichloromethane multiple times at room temperature and concentrate under reduced pressure to remove trifluoroacetic acid. Dry in vacuo at 40 °C to obtain aspartame with a yield of 96%. The purities of the crude and refined aspartame were analyzed by HPLC, and the results are as Figure 2 shown. There are many impurities in the crude product, and the β-isomer of aspartame exists, making it difficult to remove impurities.

[0177] Structure characterization data of APM: 1 H NMR (400 MHz, DMSO- d 6) δ 8.97 (dd, J = 16.3, 7.8Hz, 1H), 8.23 (s, 2H), 7.26 (dp, J = 19.8, 7.3, 6.9 Hz, 5H), 4.54 (d, J = 7.4 Hz,1H), 4.08 (t, J = 4.7 Hz, 1H), 3.66 – 3.58 (m, 3H), 3.15 – 2.67 (m, 4H); 13 C NMR(101 MHz, DMSO- d 6) δ 171.73, 171.32, 168.52, 137.27, 129.50, 128.82, 127.18,54.51, 52.51, 49.14, 36.73, 35.79; HRMS (ESI) m / z calcd for C 14 H 19 N2O5 + (M+H) + 295.12885, found 295.12915.

[0178] Example 7

[0179] A method for preparing aspartame, comprising:

[0180] (1) Synthesis of phenylalanine methyl ester

[0181] 8.26 g (50 mmol, 1 eq) of phenylalanine was refluxed in a solution of 5.45 mL (75 mmol, 1.5 eq) of thionyl chloride in 75 mL of methanol at 80 °C for 3 - 4 h. Monitored by TLC (developing solvent: PE:EA = 1:1), until the raw materials reacted completely, concentrated under reduced pressure to remove the remaining methanol to obtain the crude product, and finally purified by recrystallization from methanol to obtain the product as a white solid with a yield of 92%.

[0182] Structural characterization data of L-Phe-OCH3: 1 H NMR (400 MHz, DMSO- d 6) δ 8.88 (s, 2H), 7.36 – 7.23 (m, 5H), 4.21 (s, 1H), 3.64 (s, 3H), 3.26 (dd, J J = 13.9, 5.4 Hz, 1H), 3.18 – 3.08 (m, 1H); 13 C NMR (101 MHz, DMSO- d 6) δ 169.76, 135.25, 129.85, 129.02, 127.68, 53.74, 52.95, 40.18, 39.97, 39.76, 36.25.

[0183] (2) Synthesis of Boc-Asp(OtBu)-Phe-OCH3

[0184] Precisely weigh 1.67 mL (11 mmol, 1.5 eq) of DIC, 3.18 g (11 mmol, 1.5 eq) of Boc-Asp(OtBu)-OH, and 0.03 mL (11 mmol, 1.5 eq) of TEA and place them in a 100 mL flask. Add 50 mL of dichloromethane to dissolve and stir in an ice bath for 0.5 h. Add 1.55 g (7.2 mmol, 1 eq) of phenylalanine methyl ester to the system, remove the ice-water bath, and continue the reaction. During the reaction, the phenylalanine methyl ester gradually dissolves, and then a white precipitate gradually appears in the system. The reaction is complete after about 4 h. Concentrate under reduced pressure to remove the solvent, then add 30 mL of ethyl acetate to dissolve, wash successively with saturated NH4Cl solution, water, saturated NaHCO3 solution, and water, dry with anhydrous Na2SO4, and concentrate under reduced pressure to obtain 3.24 g of a white powder with a yield of 95%.

[0185] Structural characterization data of Boc-Asp(OtBu)-Phe-OCH3: 1 H NMR (400 MHz, DMSO- d6) δ 8.10 (d, J = 7.5 Hz, 1H), 7.24 (dt, J = 26.6, 7.2 Hz, 5H), 7.02 (d, J = 8.5 Hz, 1H), 4.54 – 4.46 (m, 1H), 4.35 (s, 1H), 3.59 (s, 3H), 3.07 – 2.88 (m, 2H), 2.63 – 2.49 (m, 1H), 2.36 (dd, J = 15.8, 9.4 Hz, 1H), 1.38 (d, J = 4.2 Hz, 18H); 13 C NMR (101 MHz, DMSO- d 6) δ 172.10, 171.38, 169.67, 155.43, 137.35, 129.53, 128.68, 127.00, 78.68, 53.99, 52.28, 51.39, 40.17, 39.96, 38.06, 37.06, 28.59, 28.09.

[0186] (3) Synthesis of Aspartame

[0187] Take the product of the previous step reaction, add 9.5 mL of TFA to dissolve it, stir at room temperature, slowly add dropwise 0.5 mL of H2O, monitor by TLC, the reaction is complete in about 1 h, concentrate under reduced pressure to remove the solvent, and add DCM multiple times and concentrate under reduced pressure to remove TFA. Add 3 mL of methanol to dissolve the reaction mixture, transfer it to a centrifuge tube, add cold ether dropwise while ultrasonicating, a white solid is produced when about 17 mL is added. Centrifuge to obtain a white powder, wash it 3 times with cold ether to obtain the product aspartame.

[0188] Structure characterization data of APM: 1 H NMR (400 MHz, DMSO- d 6) δ 8.91 (d, J = 7.4 Hz, 1H), 7.96 (d, J = 84.6 Hz, 1H), 7.27 (dd, J = 22.8, 6.8 Hz, 5H), 4.53 (q, J = 7.8 Hz, 1H), 4.15 – 4.04 (m, 1H), 3.62 (s, 3H), 3.09 (dd, J= 13.9, 5.2 Hz, 1H), 2.98 –2.66 (m, 3H); 13 C NMR (101 MHz, DMSO-d6) δ 171.73, 171.32, 137.27, 129.50, 128.84, 127.19, 54.51, 52.54, 49.16, 36.75, 35.83; HRMS (ESI) m / z Calcd for C 14 H 19 N2O5 + (M+H) + 295.12885, found 295.12858.

[0189] The method provided in this example finally obtained aspartame with a yield of 82% and a purity of 92.3%. The HPLC results are shown in Figure 3 , with few impurities, easy to purify, and no presence of the β-form isomer of aspartame. The analytical conditions for reverse-phase high-performance liquid chromatography (RP-HPLC) were as follows: The sample was eluted with a gradient of water-acetonitrile as the mobile phase, dissolved in methanol to prepare a 2 mg / mL solution. Mobile phase A was an aqueous solution of 0.1% TFA, mobile phase B was an acetonitrile solution of 0.1% TFA, the flow rate was 1 mL / min, the ultraviolet detection wavelength (λ) was 220 nm, and the elution gradient was 10 - 90% solvent B.

[0190] The raw materials for synthesizing the DPXP carrier in the present invention are rich and easily available, the reaction conditions are mild, the time consumption is short, the yield is good, it is easy to separate, and the purity is high. Using the DPXP carrier to replace the high-molecular resin in solid-phase peptide synthesis has a high homogeneous reaction efficiency and saves raw material consumption. The DPXP fragments are easily separated from aspartame after cleavage, and the DPXP fragments can be recycled, reducing waste discharge, saving costs, being environmentally friendly, and having good social and economic benefits. Due to the protection and auxiliary precipitation effects of the DPXP carrier, the formation of the β-form isomer of aspartame is avoided, and the product quality is good, without the bitter taste of the β-form isomer.

[0191] The above examples are only some examples listed for facilitating the understanding of the synthesis and application methods of the materials of the present invention, and do not limit the present invention. It can be understood that relevant practitioners can easily make appropriate modifications to this structure. Therefore, any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Use of a diphenylphosphinyloxy-X-phenol compound in the preparation of aspartame, characterized in that, The general structural formula of diphenylphosphinyloxy-X-phenol compounds is shown in formula (I): （Ⅰ） In the formula, X is O.

2. A preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds, characterized in that, It includes the following steps: Using the compound of formula (I) as a carrier, reacting with an N-terminal protected amino acid under the action of a coupling agent to obtain product A; purifying product A to obtain purified product A; wherein, the N-terminal protected amino acid is phenylalanine protected by a protecting group of fluorenylmethyloxycarbonyl or tert-butoxycarbonyl; Treating the purified product A with a fluorenylmethyloxycarbonyl removing reagent or a tert-butoxycarbonyl removing reagent to obtain product B; purifying product B to obtain purified product B; Using the purified product B as a raw material, performing a coupling reaction with aspartic acid whose N-terminal and side-chain carboxyl groups are both protected to obtain compound C; Using a methanol or tetrahydrofuran solution containing sodium methoxide as a shearing agent, shearing compound C to remove the compound of formula (I) to obtain compound D; using a cocktail solution of trifluoroacetic acid as a side-chain deprotecting agent for compound D to remove the protecting groups on the side chain to obtain trifluoroacetate E of aspartame; Neutralizing trifluoroacetate E of aspartame with sodium bicarbonate, extracting with ethyl acetate, precipitating, filtering, washing with ethyl acetate, and drying to obtain pure product F of aspartame; Among them, formula (I) is , and X is O.

3. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, characterized in that, The purification process of product A includes: Adding an alkane or ether solvent to product A to separate product A from other impurities; Performing filtration, washing or recrystallization operations on the separated product A to obtain purified product A.

4. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, wherein, The purification process of product B includes: Adding an alkane or ether solvent to product B to separate product B from other impurities; Performing filtration, washing or recrystallization operations on the separated product B to obtain purified product B.

5. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, characterized in that The general structural formula of product A is: ； Wherein, PG is 9-fluorenylmethyloxycarbonyl, tert-butoxycarbonyl or H.

6. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, characterized in that The general structural formula of compound C is: ； The general structural formula of compound D is: ； PG1 is tert-butoxycarbonyl, benzyloxycarbonyl, fluorenylmethyloxycarbonyl or H; PG2 is Fm, Bz or tBu.

7. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, characterized in that, The coupling agent includes a carbodiimide condensing agent, a carbonium salt condensing agent or a phosphonium salt condensing agent.

8. The preparation method of aspartame assisted by diphenylphosphinyloxy-X-phenol compounds according to claim 2, characterized in that, The fluorenylmethyloxycarbonyl removing reagent includes a solution of piperidine, a methanol solution of diethylamine, an acetonitrile solution, a tetrahydrofuran THF solution or an N,N-dimethylformamide DMF solution; the tert-butoxycarbonyl removing reagent includes trifluoroacetic acid, hydrochloric acid, a dichloromethane, chloroform or N,N-dimethylformamide DMF solution of phosphoric acid.

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