JPH10248592A - Production of optically active 2-benzylsuccinic acid and its derivative - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently obtain the subject compounds utilized for medicines, agrochemicals, etc., by treating a specific (R,S)-2-benzylsuccinic acid (diester) with a specified optically selectively ester-decomposing enzyme and subsequently separating the products. SOLUTION: This optically active 2-benzylsuccinic acid and its esters are efficiently obtained by allowing an esterase originated from a microorganism belonging to the genus Serratia or Pseudomonas or originated from porcine pancreas and capable of optically selectively hydrolyzing (R,S)-2-benzylsuccinic acid or diester of its derivative to act on an (R,S)-2-benzylsuccinic acid or the diester of the derivative of the formula [R1 , R2 are each a halogen, hydroxyl group, a (substituted) 1-20C linear branched saturated or unsaturated hydrocarbon; R3 is H, a halogen, a (substituted) 1-20C linear, branched or cyclic saturated or unsaturated hydrocarbon] and subsequently separating the produced optically active 2-benzylsuccinic acid (diester) and the optically active 2-benzylsuccinic acid (monoester).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optically active (R) -2-benzylsuccinic acid or a derivative thereof, which is useful as an intermediate for synthesizing an optically active physiological activity and a derivative thereof used in medicines and agricultural chemicals, and (S) ) -2-Benzylsuccinic acid or a derivative thereof. More specifically, the present invention relates to an optically active (R) -2-benzylsuccinic acid, which is obtained by enzymatically hydrolyzing a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof using an enzyme. Or a method for producing a derivative thereof and (S) -2-benzylsuccinic acid or a derivative thereof.

[0002]

2. Description of the Related Art At present, many physiologically active compounds are used as a mixture of their optical isomers. However, the desired activity is often present in only one optical isomer. Further, it is known that the other optical isomer may have toxicity to a living body without having a desired activity. Therefore, in order to provide an effective and safe drug or biologically active compound, there is a strong demand to develop a method for producing a compound having high optical purity.

[0003] (S) -2-benzylsuccinic acid is a compound useful as a synthetic intermediate of a therapeutic agent for diabetes having a hypoglycemic effect and an insulin secreting effect (JP-A-5-3).
No. 10693). An efficient and industrial production method for producing this compound is desired, and several attempts have been made to date. For example, a method of producing (S) -2-benzylsuccinic acid by optically resolving racemic 2-benzylsuccinic acid with optically active 1-phenylethylamine (Arkiv Kemi Mineral God, 26B, No. 11 (1948) )
Asymmetric synthesis from 2-benzylidene succinic acid (Tetrahe
dron Letters, 32, 3671-3672 (1991)).

As a method using an enzyme, a method of producing (S) -2-benzylsuccinic acid by asymmetric hydrolysis of α-chymotrypsin on racemic diethyl 2-benzylsuccinate ( Journal of the Ameri
can Chemical Society, 3495-3502 (1968)).

[0005] However, these methods have problems such as difficulty in mass production due to low optical purity or complicated synthesis steps.

[0006] From such a viewpoint, there is a strong demand for a method for efficiently producing optically active 2-benzylsuccinic acid with extremely high optical purity.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to utilize an ester hydrolase having a high optical selectivity and to provide an optical activity (S) having a high optical purity. ) And (R) -2-benzylsuccinic acid or a derivative thereof are to be efficiently and industrially produced.

[0008]

SUMMARY OF THE INVENTION The present invention provides an optically active 2-
A process for producing benzylsuccinic acid or a derivative thereof, comprising the following general formula:

[0009]

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(Wherein R ₁ and R ₂ are each independently a halogen atom, a hydroxyl group or an alkoxyl group, which is substituted or unsubstituted with 1 to 20 carbon atoms.
And R ₃ is a hydrogen atom or a halogen atom, or is substituted with a halogen atom, a hydroxyl group, or an alkoxyl group; or It is an unsubstituted, linear, branched, or cyclic, saturated or unsaturated hydrocarbon group having 1 to 20 carbon atoms. ) (R,
Derived from microorganisms belonging to the genus Serratia or Pseudomonas capable of optically selectively hydrolyzing diesters of (S) -2-benzylsuccinic acid or a derivative thereof and diesters of (R, S) -2-benzylsuccinic acid or a derivative thereof. Or reacting with an esterase derived from porcine pancreas; and separating the formed diester of optically active 2-benzylsuccinic acid or a derivative thereof from the monoester of the optically active 2-benzylsuccinic acid or a derivative thereof Performing the method.

In a preferred embodiment, the separated diester of optically active 2-benzylsuccinic acid or a derivative thereof is further hydrolyzed to produce optically active 2-benzylsuccinic acid or a derivative thereof.

In a preferred embodiment, the isolated monoester of optically active 2-benzylsuccinic acid or a derivative thereof is further hydrolyzed to produce optically active 2-benzylsuccinic acid or a derivative thereof.

[0013] In a preferred embodiment, the method further comprises the step of separating the isolated diester of optically active 2-benzylsuccinic acid or a derivative thereof or the monoester of optically active 2-benzylsuccinic acid or a derivative thereof (R,
S) converting to a diester of 2-benzylsuccinic acid or a derivative thereof and reusing the diester for producing optically active 2-benzylsuccinic acid or a derivative thereof.

In a preferred embodiment, the enzyme hydrolyzes a diester of (R) -2-benzylsuccinic acid or a derivative thereof in a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof. To produce monoesters of (R) -2-benzylsuccinic acid or its derivatives and diesters of (S) -2-benzylsuccinic acid or its derivatives.

[0015] In a preferred embodiment, the method comprises separating the isolated monoester of optically active (R) -2-benzylsuccinic acid or a derivative thereof into a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof. Conversion and reuse in the production of optically active (S) -2-benzylsuccinic acid or a derivative thereof.

[0016] In a preferred embodiment, the enzyme is selected from the group consisting of a purified enzyme, a microbial cell, a microbial cell culture, and a processed product of the microbial cell.

In a preferred embodiment, the enzyme is immobilized on a carrier for immobilization.

In a preferred embodiment, the enzyme is Serratia marcescens.
It is an ester-decomposing enzyme derived from a microorganism belonging to.

In a preferred embodiment, R ₁ , R ₂ and R _{3 in} the above general formula each independently have 1 to 9 carbon atoms.
It is.

In a preferred embodiment, R ₁ , R ₂ and R _{3 in} the above general formula each independently have 1 to 4 carbon atoms.
It is.

In a preferred embodiment, R ₁ and R ₂ in the above general formula are each independently selected from the group consisting of an alkyl group and an alkoxyalkyl group.

In a preferred embodiment, R _{3 in the} above general formula is hydrogen or a trifluoromethyl group.

In a preferred embodiment, (R,
The diester of (S) -2-benzylsuccinic acid is (R, S)
Selected from the group consisting of dimethyl-2-benzylsuccinate, diethyl (R, S) -2-benzylsuccinate, and dimethoxyethyl (R, S) -2-benzylsuccinate.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the present specification, “2-benzylsuccinic acid or a derivative thereof” has the general formula:

[0026]

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Means a compound represented by Here, R ₃ is a hydrogen atom or a halogen atom, or a carbon atom having 1 to 2 carbon atoms which is substituted or unsubstituted with a halogen atom, a hydroxyl group, or an alkoxyl group.
0, a linear, branched, or cyclic saturated or unsaturated hydrocarbon group. R ₃ is preferably, but not limited to, a hydrogen atom or a trifluoromethyl group.

As used herein, “(R, S) -2-benzylsuccinic acid or a diester of a derivative thereof” is defined as
It means a racemic mixture of a diester of (R) -2-benzylsuccinic acid or a derivative thereof and a diester of (S) -benzylsuccinic acid or a derivative thereof. In the racemic mixture, the mixing ratio of the (R) form and the (S) form does not necessarily have to be 1: 1.

The method of the present invention comprises reacting a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof with an enzyme having an ester hydrolyzing activity derived from a microorganism or pig to produce (R) or (S). ) -Dibenzyl ester of (R, S) -2-benzyl succinic acid or a derivative thereof can be converted to 2-benzyl succinic acid or It is based on converting to a mixture of a diester of the derivative and a monoester of 2-benzylsuccinic acid or a derivative thereof and fractionating each using the difference in the chemical or physical properties of these compounds.

The enzyme reaction substrate used in the present invention has a general formula:

[0031]

Embedded image

Is a diester of 2-benzylsuccinic acid or a derivative thereof. Where R ₁ , R ₂ ,
Are each independently a straight-chain, branched or cyclic saturated or unsaturated hydrocarbon group which is substituted or unsubstituted with a halogen atom, a hydroxyl group or an alkoxyl group, and R ₃ is a hydrogen atom Or a halogen atom, or a linear, branched, or cyclic saturated or unsaturated hydrocarbon group substituted or unsubstituted with a halogen atom, a hydroxyl group, or an alkoxyl group. The carbon number of R ₁ to R ₃ is 1 to 20, preferably 1 to 9, and more preferably 1 to 4. R ₃ is preferably, but not limited to, a hydrogen atom or a trifluoromethyl group.

(R, S)-which is an enzyme reaction substrate of the present invention.
The diester of 2-benzylsuccinic acid or a derivative thereof is appropriately selected based on the substrate specificity of the enzyme to be used, solubility in an enzyme reaction solvent, ease of separation after the enzyme reaction, and the like. Particularly preferred are dimethyl 2-benzylsuccinate, diethyl 2-benzylsuccinate and dimethoxyethyl 2-benzylsuccinate, which can be easily synthesized from 2-benzylsuccinic acid by a known esterification method. For example, it can be obtained by reacting (R, S) -2-benzylsuccinic acid with methanol, ethanol, methoxyethanol or the like in the presence of an acid such as sulfuric acid. (R, S) -2-benzylsuccinic acid can be produced by a method known in the art, for example, a method of synthesizing by saponifying diethyl 2-benzyl-2-ethoxycarbonylsuccinate and decarboxylating ( Liebigs Anna
hlen, 256, 95 (1890)). Other (R,
The diester of S) -2-benzylsuccinic acid or a derivative thereof can also be produced in the same manner as described above.

The microorganism used in the present invention or the enzyme derived from porcine pancreas optically selectively hydrolyzes the diester of (R, S) -2-benzylsuccinic acid or a derivative thereof to obtain optically active 2-benzylsuccinic acid. Alternatively, any compound capable of producing a diester of a derivative thereof and an optically active 2-benzylsuccinic acid or a monoester of a derivative thereof can be used. Preferably,
An enzyme that hydrolyzes a diester of (R) -2-benzylsuccinic acid or a derivative thereof optically and selectively to a monoester of (R) -2-benzylsuccinic acid or a derivative thereof is used, but is not limited thereto.

Further, a purified enzyme having the activity of the above enzyme, a microbial cell, a microbial cell culture solution, and a processed product of the microbial cell may be used.

The enzyme used in the present invention is preferably
They are esterases derived from microorganisms belonging to the genera Serratia and Pseudomonas and esterases derived from pig pancreas. Specific examples of these enzymes include SM esterase (derived from Serratia marcescens, manufactured by Nagase Seikagaku Corporation), lipase 2G (derived from Pseudomonas SP, manufactured by Nagase Seikagaku Corporation), Lipase Type II (derived from porcine pancreas, Sigma). Company).

The microbial cells can be obtained by culturing by a method well known to those skilled in the art. The enzyme can be induced using 2-benzylsuccinic acid diester as a substrate. Microbial cells obtained by this culture, a culture solution thereof, a processed product obtained by subjecting the cells to crushing or the like, and an enzyme roughly purified from the processed product by a method known to those skilled in the art can also be used.

Further, the purified enzyme, the microbial cell, the microbial cell culture obtained from the microbial cell culture, and the crude enzyme obtained from the processed microbial cell are immobilized on a carrier for immobilization. Synthetase can also be used. As a method for immobilization, a method known to those skilled in the art such as a carrier bonding method (for example, a covalent bonding method, an ion bonding method, or a physical adsorption method), a crosslinking method, or an entrapping method (lattice type or microcapsule type). Can be used. The immobilization carrier is easily selected by those skilled in the art in view of the ability to immobilize the enzyme used in the present invention, reusability, ease of handling, and the like, and a commercially available product can be suitably used. For example, Chitopearl (Fujibo Co., Ltd.)
Etc. can be used.

The enzymatic reaction of the present invention is carried out by adding the above-mentioned enzymatic agent or the ester-degrading enzyme collected from a microorganism and a culture to water or a buffer containing a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof. Addition and stirring are performed. Alternatively, the enzymatic reaction of the present invention is carried out by reacting a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof on an esterase adsorbed on a carrier for immobilization.

The enzymatic reaction can be performed by adjusting the pH. A buffer such as, for example, a phosphate buffer may be used to maintain an optimal pH for the enzymatic reaction. PH of reaction solution
Is 5 to 9, preferably 6 to 8.

Although the amount of the enzyme used is not particularly limited,
A preferred range is about 0.1 to 10 g / mol of substrate relative to the diester of (R, S) -2-benzylsuccinic acid or a derivative thereof.

The reaction temperature is from 10 ° C. to 50 ° C., preferably from 20 ° C. to 40 ° C. The reaction time depends on the amount of enzyme used,
It varies depending on the reaction temperature, reaction pH and the like, but is usually about 1 to 24 hours.

After the completion of the reaction, the resulting monoester of optically active 2-benzylsuccinic acid or a derivative thereof and the diester of optically active 2-benzylsuccinic acid or a derivative thereof are usually used in a solvent extraction method, a column chromatography method or the like. Separate by separating operation. In the solvent extraction method, when n-hexane, heptane, ethyl acetate, cyclohexane, isooctane, isopropyl ether or t-butyl methyl ether is used, 98% or more of a diester of optically active 2-benzylsuccinic acid or a derivative thereof is obtained from the reaction solution. It is possible to recover in a recovery rate.

The fractionated optically active 2-benzylsuccinic acid diester is hydrolyzed by a chemical hydrolysis method using an acid, a base or the like, a transesterification reaction in excess methanol, or an enzymatic method using an optional hydrolase. Decompose, crystallize under acidic conditions, and
By recrystallization from water (水 35 vol%), optically active 2-benzylsuccinic acid can be easily obtained.

On the other hand, the monoester of optically active 2-benzylsuccinic acid or a derivative thereof produced by the hydrolysis reaction is obtained by removing the diester of optically active 2-benzylsuccinic acid or a derivative thereof from the enzyme reaction solution by a solvent extraction method. By setting the aqueous layer under acidic conditions, it can be recovered at a recovery rate of 98% or more using a solvent such as n-hexane, heptane, ethyl acetate, or isopropyl ether. The recovered monoester of optically active 2-benzylsuccinic acid or a derivative thereof is esterified again by an ordinary method, and the optically active 2-benzylsuccinic acid or its derivative is esterified.
After conversion to the diester of benzyl succinic acid or its derivative, it is racemized by heating under alkaline conditions, or hydrolyzes the monoester of optically active 2-benzyl succinic acid or its derivative and heats it under alkaline conditions. Then, it can be racemized and reused as a substrate.

Further, the enzymatic reaction is stopped at a reaction rate of 20 to 40%, and the monoester of optically active 2-benzylsuccinic acid or a derivative thereof is subjected to solvent extraction by the above-mentioned method, and then hydrolyzed by the above-mentioned hydrolysis method. Decomposes and crystallizes under acidic conditions, then isopropyl alcohol (25-35V
(%), recrystallization from water makes it possible to easily obtain optically active (R) -2-benzylsuccinic acid.

[0047]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

In the examples, the quantification of 2-benzylsuccinic acid diester, 2-benzylsuccinic acid monoester or 2-benzylsuccinic acid and the measurement of optical purity in the reaction solution were carried out under the following analytical conditions. Performed by high performance liquid chromatography (HPLC).

(HPLC analysis conditions) Column: Chiral cell OD 0.46 cmφ × 25 cm (Waters) Mobile phase: hexane / isopropanol / trifluoroacetic acid (95: 5: 0.1) Flow rate 1 mL / min Detection UV 220 nm (Example) 1) To 2,000 g of distilled water was added 236 g (1 mol) of dimethyl 2-benzylsuccinate, and 1N-K
After adjusting the pH of the reaction solution to 7 with OH, 2 g of SM esterase (derived from Serratia marcescens, manufactured by Nagase Seikagaku Corporation) was added, and the pH of the reaction solution was adjusted to 7 with 10N-KOH.
While stirring at 30 ° C. for 24 hours.

After the completion of the reaction, the reaction solution was concentrated to 300 ml with a rotary evaporator, and 500 ml of ethyl acetate was added.
Was added, and dimethyl 2-benzylsuccinate was extracted. When the extract was analyzed by HPLC, the optical purity was 98% ee
106 g of the above dimethyl (S) -2-benzylsuccinate
Obtained (yield 45%).

After the extract was washed with weakly basic water, ethyl acetate was distilled off with a rotary evaporator to obtain (S) -2.
-Dimethyl benzylsuccinate was obtained. 1N-NaOH is added, hydrolyzed at 60 ° C., crystallized under acidic conditions, and then isopropyl alcohol (25-35 Vol.
%) By recrystallization with water, an optical purity of 99%
83 g of (S) -2-benzylsuccinic acid of ee was obtained (40% yield).

(Example 2) After monomethyl 2-benzylsuccinate produced in Example 1 was extracted with ethyl acetate under acidic conditions, the ethyl acetate in the organic layer was distilled off with a rotary evaporator to obtain (R) -2. -Monomethyl benzylsuccinate was obtained. Next, by reacting with methanol at 60 ° C. in the presence of an acid catalyst, 122 g of dimethyl (R) -2-benzylsuccinate was obtained. This was reacted in methanol at 60 ° C. in the presence of sodium methylate and racemized to obtain racemic 2-dimethyl benzyl 2-benzylsuccinate in a yield of 98%.

Example 3 An enzyme reaction was carried out in the same manner as in Example 1, and the reaction was stopped at a reaction rate of 40% for a reaction time of 15 hours. The resulting monomethyl (R) -2-benzylsuccinate was extracted with ethyl acetate under acidic conditions after extracting and removing dimethyl (S) -2-benzylsuccinate. The extract was analyzed by HPLC.
80 g of dimethyl (R) -2-benzylsuccinate having a% ee or more was obtained (36% yield). Next, ethyl acetate was distilled off by a rotary evaporator, and 1N-NaOH was added to the obtained monomethyl (R) -2-benzylsuccinate, and
Hydrolysis was carried out at 0 ° C., crystallization was carried out under acidic conditions, and further recrystallization was carried out with isopropyl alcohol (25-35% by volume) water to obtain 71 g of optically active (R) -2-benzylsuccinic acid ( Yield 32%).

Example 4 Various (R, S) -2-benzylsuccinic acid diesters were prepared from various (R, S) -2-benzylsuccinic acid diesters by various esterases shown in Table 1 by a method similar to Examples 1 and 3. 2-benzylsuccinic acid and (R) -2-benzylsuccinic acid were obtained. The result is (S)-
Table 1 shows 2-benzylsuccinic acid, and Table 2 shows (R) -2-benzylsuccinic acid.

[0055]

[Table 1]

[0056]

[Table 2]

Example 5 100 ml of a 25 mg / ml SM esterase enzyme solution and 300 ml of water were added to 100 g of the immobilizing carrier Chitopearl (manufactured by Fuji Boseki Co., Ltd.).
After shaking at 30 ° C for 2 hours, suction filtration was performed. After the carrier for immobilization was sufficiently washed with water, the enzyme activity of the filtrate was measured. As a result, the immobilized SM esterase was obtained with an adsorption rate of 60%.

(Example 6) 23.6 g (1 mol) of dimethyl 2-benzylsuccinate was added to 100 ml of distilled water, and the pH of the reaction solution was adjusted to 7 with 1N-KOH. 20 g of the immobilized SM esterase was added, and the enzymatic reaction and product extraction were performed in the same manner as in Example 1. As a result, the optical purity was 9 with the same yield as in Example 1.
9% ee of (S) -2-benzylsuccinic acid was obtained. Further, an enzymatic reaction and a product obtained by the enzymatic reaction were extracted in the same manner as in Example 3 using the immobilized SM esterase. As a result, (R) -2-benzylsuccinic acid having an optical purity of 99% ee was obtained in the same yield as in Example 3.

[0059]

Industrial Applicability By using the method of the present invention, an optically active 2-benzylsuccinic acid or a derivative thereof having a high optical purity can be efficiently obtained, and an optically active synthetic compound for producing a therapeutic agent for diabetes or the like can be obtained. An intermediate could be provided.

Claims (14)

[Claims] 1. A method for producing optically active 2-benzylsuccinic acid or a derivative thereof, which comprises the following general formula: (Wherein R ₁ and R ₂ are each independently a straight-chain, branched, or cyclic C 1-20 carbon atom which is substituted or unsubstituted with a halogen atom, a hydroxyl group, or an alkoxyl group. A saturated or unsaturated hydrocarbon group, and R ₃ is a hydrogen atom or a halogen atom, or a C 1-20 carbon atom substituted or unsubstituted with a halogen atom, a hydroxyl group, or an alkoxyl group; (R, S) -2-benzylsuccinic acid or a diester of a derivative thereof represented by a straight-chain, branched, or cyclic saturated or unsaturated hydrocarbon group; and (R, S) -2 -Derived from a microorganism belonging to the genus Serratia or Pseudomonas which is capable of optically selectively hydrolyzing diesters of benzylsuccinic acid or a derivative thereof, or from porcine pancreas. Reacting with a telomerase; and separating the formed diester of the optically active 2-benzylsuccinic acid or a derivative thereof from the monoester of the optically active 2-benzylsuccinic acid or a derivative thereof. Method. 2. The method according to claim 1, further comprising hydrolyzing the separated diester of optically active 2-benzylsuccinic acid or a derivative thereof to produce optically active 2-benzylsuccinic acid or a derivative thereof. 3. The method according to claim 1, further comprising hydrolyzing the isolated monoester of optically active 2-benzylsuccinic acid or a derivative thereof to produce optically active 2-benzylsuccinic acid or a derivative thereof. 4. An isolated optically active dibenzyl succinic acid or derivative thereof diester, or a monoester of optically active 2-benzyl succinic acid or derivative thereof is converted to (R, S) -2-benzyl succinic acid or a derivative thereof. Converting to a diester of the derivative and reusing it for the production of optically active 2-benzylsuccinic acid or a derivative thereof.
A method according to any of claims 1 to 3. 5. The enzyme hydrolyzes a diester of (R) -2-benzylsuccinic acid or a derivative thereof in a diester of (R, S) -2-benzylsuccinic acid or a derivative thereof to form (R) 5. A monoester of 2-benzylsuccinic acid or a derivative thereof and a diester of (S) -2-benzylsuccinic acid or a derivative thereof are produced.
The method according to any of the above. 6. The isolated monoester of optically active (R) -2-benzylsuccinic acid or its derivative is converted to (R, S)-
2. The method according to claim 1, further comprising a step of converting the compound into a diester of 2-benzylsuccinic acid or a derivative thereof and reusing the diester to produce optically active (S) -2-benzylsuccinic acid or a derivative thereof.
6. The method according to any one of claims 1 to 5. 7. The method according to claim 1, wherein the enzyme is selected from the group consisting of a purified enzyme, a microbial cell, a microbial cell culture, and a processed product of the microbial cell. 8. The method according to claim 1, wherein the enzyme is immobilized on a carrier for immobilization. 9. The method according to claim 8, wherein the enzyme is Serratia marcescens.
The method according to any one of claims 1 to 8, which is an esterase derived from (Serratia marcescens). 10. The method according to claim 1, wherein each of R ₁ , R ₂ , and R _{3 in} the general formula has 1 to 9 carbon atoms independently. 11. The method according to claim 1, wherein R ₁ , R ₂ , and R _{3 in} the general formula each independently have 1 to 4 carbon atoms. 12. The method according to claim 1, wherein R ₁ and R _{2 in the} general formula are each independently selected from the group consisting of an alkyl group and an alkoxyalkyl group. 13. The method according to claim 1, wherein R _{3 in the} general formula is a hydrogen atom or a trifluoromethyl group. 14. The diester of (R, S) -2-benzylsuccinic acid is dimethyl (R, S) -2-benzylsuccinate, diethyl (R, S) -2-benzylsuccinate, and (R) 14. The method according to any one of claims 1 to 9 or 13, wherein the method is selected from the group consisting of: dimethoxyethyl ,, S) -2-benzylsuccinate.