JPH01235599A - Method for optically resolving racemic alcohol - Google Patents

Abstract

PURPOSE:To simply and selectively improve efficiency of optical resolution, by preferentially and irreversibly subjecting either one of antipode of racemic alcohol to esterification with a carboxylic acid anhydride in an organic solvent in the presence of a hydrolase. CONSTITUTION:(A) Racemic alcohol, e.g., of aliphatic secondary alcohol such as 2-heptanol is blended with (B) >=8C straight-chain or branched chain symmetrical carboxylic acid anhydride in (C) an organic solvent such as n-heptane so that mole ratio of the components A:B is 1:>=0.5 and (D) the resultant substrate reaction system is prepared so that water content of the reaction system (D) is <=2W/V%. Then (E) hadrolase of pancreatic lipase, etc., of swine having 0.1-10W/V% water content is added to the system D and the mixture is subjected to ester exchange reaction to afford (F) reaction product. Then the ingredient F is separated with extraction treatment by two phases of water insoluble organic solvent with water to collect the optically active racemic alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for selectively and efficiently optically resolving racemic alcohols by enzymatic reaction in an organic solvent.

[Prior art]

Conventional optical resolution methods by esterification of racemic alcohol using enzymes include methods that utilize the so-called ester synthesis reaction in which racemic alcohol and carboxylic acid are reacted, and methods that utilize transesterification reaction between racemic alcohol and carboxylic acid ester. It has been known.

In the method using ester synthesis reaction, the hydrolysis reaction of the produced ester takes priority, so it is difficult to carry out in an aqueous system.Reaction examples in organic solvents (J, Am, Chem.
, Soc, 107, 7072 (1985)), but in these examples, as the reaction progresses,
Since water is generated in the system, enzymes that are insoluble in organic solvents dissolve in water and form a gel-like substance. For this reason, there is a drawback that the enzyme cannot be efficiently recovered after the reaction is completed, and the reaction is slow and the yield and purity of the optically active substance obtained are not necessarily sufficient.Therefore, the use of insoluble enzymes in organic solvents The reaction was inappropriate. Another method, a racemic alcohol optical resolution method that utilizes transesterification, is generally shown by the following reaction formula.

Racemic alcohol ester
Optically active alcohol Alcohol Ester of optically active alcohol (In the formula, R1 and R3 are alcohol residues, and R2 is a carboxylic acid residue.) This reaction is an equilibrium reaction, and the starting material (left side of the reaction formula) is completely produced. It has the disadvantage that the reaction time is long because it is extremely difficult to convert it into a compound (on the right side of the reaction formula).

In addition, this tendency is related to the 2nd J1, which has a large steric hindrance as a racemic alcohol! This becomes even more noticeable when alcohol or tertiary alcohol is used.

In order to overcome these drawbacks, triheroethanol (J, Amer, ch.
em, soc, 1077072 (1985), Tetr
ahedron Lett*28, 2091 (198
7)) and diacylglycerin [Tetrahedron
Lett, 27.29 (1986)) has proposed a method using an ester. Although these methods have the advantage of allowing the transesterification reaction to proceed slightly to the right, the reaction time is still long and the reaction may not be completed sufficiently, especially when the racemic alcohol is a secondary or tertiary alcohol. This includes the difficulty that the corresponding optically active substance cannot be efficiently synthesized.

In addition, conventional methods have been known in which alcohols are esterified with acid anhydrides using catalysts such as acids and bases without using enzymes, but in these methods, it is difficult to control the stereoselectivity of the product. This was virtually impossible. (Example using chain carboxylic acid anhydride; VJ, Pr1chard, Or
g, Syn, , Co11. Vol, 3,452 (19
55), Examples using cyclic carboxylic acid anhydrides; A, C.

Cope, ,Org,Syn,,Co11. Vol.
4,304 (1963)).

Furthermore, in conventional enzyme-catalyzed reaction systems, water-soluble enzymes are used in aqueous solutions, so the acylating agent, carboxylic acid anhydride, undergoes a hydrolysis reaction with the water in the system, resulting in free carboxylic acid. Therefore, it was extremely difficult to carry out the esterification reaction.

〔the purpose〕

The present invention differs from the above-mentioned conventional techniques in that racemic alcohol can be resolved in a high yield and in a short time, and the enzyme used is excellent in recovery and reusability. The purpose is to provide an optical resolution method.

〔composition〕

According to the present invention, one enantiomer of a racemic alcohol is preferentially and irreversibly esterified using a carboxylic acid anhydride in an organic solvent in the presence of a hydrolase,
Next, a method for optical resolution of racemic alcohol is provided, which is characterized by separating optically active substances.

The present invention selects a non-aqueous organic solvent in which the enzyme does not dissolve as a reaction solvent in order to improve recovery and reusability of the enzyme. It is characterized by selecting an esterification reaction.

In the present invention, the reaction when linear butyric anhydride, for example, is used as the carboxylic anhydride is expressed as follows.

Racemic alcohol Chikarakasaininishikata acid Ester of optically active alcohol Butyric acid
Optically active A (in the formula, R1 represents an alcohol residue) and the reaction when cyclic glutaric anhydride is used as the carboxylic anhydride is expressed as follows.

■.

Racemic alcohol Vk glutarium (wherein R1 represents an alcohol residue) In other words, in the process of the present invention, irreversible cleavage of the acid anhydride occurs in both cases in which a linear or cyclic carboxylic acid anhydride is used. Because it uses a reaction, it does not become an equilibrium reaction (reversible reaction) like conventional transesterification reactions, but the reaction proceeds irreversibly to the right, so the reaction is completed in a short time.
It becomes possible to efficiently obtain an optically active substance.

The carboxylic acid anhydride used in the present invention may be linear or cyclic. However, highly reactive carboxylic acid anhydrides that allow the reaction to proceed non-enzymatically are undesirable, so chain anhydrides are linear or branched symmetrical carboxylic acids with 8 or more carbon atoms. Anhydrous is preferred. Further, as the cyclic anhydride, a carboxylic acid anhydride having a 5-membered or 6-membered ring structure is preferable, and examples thereof include succinic anhydride, maleic anhydride, phthalic anhydride, and glutaric anhydride.

In the present invention, there are no particular restrictions on the racemic alcohol used as a reaction substrate, but secondary alcohols are preferable to primary alcohols because they allow a higher degree of asymmetric recognition. Examples of secondary alcohols include (R,5)-3-chloro-1-P-toluenesulfonyloxy-2-propanol, (R,5)-1-phenylethanol, (R,5)
)-1-phenyl-2-chloroethanol, (R,S)
-Aromatic secondary alcohols such as manzolonitrile, aliphatic secondary alcohols such as 2-heptatool, 2-octatool, 2-nonanol, 2-decanol, and multiple hydroxyl groups such as phenylethylene glycol Examples include racemic alcohols with

The organic solvent in the present invention is the alcohol shown above or other non-aqueous organic solvent.

Specific examples of non-aqueous organic solvents include n-heptane,
Linear hydrocarbons such as n-hexane and n-hebutane, branched chain hydrocarbons such as isobutane, isopentane, and 2-methylpentane, alicyclic hydrocarbons such as cyclopentane and cyclohexane, methylene dichloride, and chloroform. , halogen-containing hydrocarbons such as carbon tetrachloride, dichloroethane, trichloroethane, aromatic hydrocarbons such as benzene, toluene, xylene, cumene, cymene, mesitylene, diisopropylbenzene, aliphatic hydrocarbons such as diethyl ether, diisopropyl ether, n-dibutyl ether, etc. Examples include ether, alicyclic ethers such as tetrahydrofuran, and tetrahydropyran, among which n-hexane, toluene, diisopropylbenzene, diethyl ether, diisopropyl ether, dibutyl ether, and carbon tetrachloride are more suitable.

The enzyme in the present invention refers to a hydrolytic enzyme, and more specific examples include lipases such as swine pancreatic lipase, yeast lipase derived from the genus Candida, bacterial lipase derived from the genus Aspergillus, Mucor, and Pseudomonas, or pigs. Examples include esterase derived from the liver, or proteolytic enzymes such as trypsin, chymotrypsin, and subtilisin.

In addition, these hydrolytic enzymes may be purified products or compositions, and their forms include powdered or granular hydrolytic enzymes or microbial cells that produce hydrolytic enzymes (treated microbial cells, resting or stationary microbial cells). ) can be used.

Furthermore, immobilization carriers such as polymers such as polystyrene, polypropylene, starch, and gluten, and inorganic materials such as activated carbon, porous glass, celite, zeolite, kaolinite, bentonite, alumina, silica gel, hydroxyapatite, calcium phosphate, and metal oxides can be used. It is also possible to use dried immobilized enzymes obtained by supporting and immobilizing the above-mentioned hydrolytic enzymes on materials etc. by a physical adsorption method. In addition, after the reaction is complete, the enzyme filtered and recovered from the reaction solution retains sufficient activity and reaction stereoselectivity, so it can be reused repeatedly, and the enzyme can be used for continuous reactions. It is also possible to use

In the present invention, the water content of the reaction system is extremely low,
Although it is necessary to carry out the reaction in a substantially nonaqueous system, the presence of a small amount of water in the enzyme is necessary, so the water content contained in the liquid phase of carboxylic acid anhydride, alcohol, and organic solvent is is 2% (w/V) or less, and furthermore, 0.
5% (W/V) or less is desirable.

In addition, the water content of powdered or granular enzyme that is a solid phase is 0.1-10% (W/V) and 0.5-5% (W/V).
V) is desirable. The water content of each substance mentioned above is adjusted to vR by various drying methods, for example, using a suitable desiccant for liquids, drying in a vacuum desiccator for solids, etc.

The molar ratio of racemic alcohol and carboxylic anhydride, which are reaction substrates used in the present invention, is not particularly limited as long as racemic alcohol:carboxylic anhydride=1:0.5 or more.

In the present invention, after the transesterification reaction, an optically active substance, that is, an optically active ester or an optically active alcohol, is separated from the reaction product.

In this case, as a specific separation method, for example, an extraction operation using a two-phase system of a poorly water-soluble or water-insoluble organic solvent and water, a separation operation using a column, separation by distillation, etc. are employed.

In particular, when using a cyclic carboxylic acid anhydride, it becomes possible to perform an extraction operation using an aqueous alkaline solution and a water-insoluble organic solvent, or to use an ion exchange resin, etc., in separating the optically active alcohol monoester and the optically active alcohol.

〔effect〕

Since the present invention has the above-mentioned configuration, it produces extremely remarkable technical effects as described below.

(2) In the present invention, racemic alcohol can be optically resolved irreversibly as shown in the above reaction formula, so it is possible to efficiently produce an optically active substance in a short time.

■ Conventional transesterification reactions require a long time, but even when sterically hindered secondary and tertiary alcohols are used as racemic alcohols, these optically active substances can be easily optically resolved. can.

■Since the present invention is carried out in an organic solvent, the enzyme is not dissolved in the reaction system, so the enzyme and the product can be separated and recovered by simple operations such as filtration, and the recovered enzyme remains intact. It is possible to reuse.

Therefore, the method of the present invention is extremely useful as a method for producing optically active intermediates for synthesizing pharmaceuticals such as β-blockers used as arrhythmia and antihypertensive agents, and electronic materials such as ferroelectric liquid crystals. be.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Racemic 1-phenylethanol (1, 26 g, 10.
3 mmol) and glutaric anhydride (0,645 g, 5.7
mmol) was previously dried overnight with molecular sieve 4A and then dissolved in toluene (50i+1). Add Amano P (manufactured by Amano Pharmaceutical) (5 g) to this solution and heat at 25°C for 1 hour.
Shake at 50 rpm. After 16 hours, the reaction solution was collected by filtration,
When the filtrate was measured by IPLC using an optically active column, (S)-1-phenylethanol had an optical purity of 9.
Obtained with a yield of 85% vs. 0% of theory.

Example 2 Racemic 3-chloro-1-p-toluenesulfonyloxy-2-propanol (Ig, 3.78 mmol) and succinic anhydride (0.21 g, 2.07 ml aol) were preliminarily dried overnight with molecular sieve 4A. Dissolve in reserved carbon tetrachloride (10 ml). Add Amano CBS to this solution.
(Manufactured by Amano Pharmaceutical) (Ig) was added at 25℃, 150rpi+
Shake with After 16 hours, the reaction solution was collected by filtration, and the filtrate was measured by HLPC using an optically active column.
)-3-chloro-1-p-toluenesulfonyloxy-
2-Propatool has optical purity of 95%.

It was obtained with a theoretical yield of 80%.

Example 3 Racemic 1-phenyl-2-chloroethanol (0,6
26g, 4.0mmol) Phthalic anhydride (0.33
,,2,22 mmol) in advance with molecular sieve 4A.
Dissolve in diethyl ether (5-), which has been dried overnight. Amano P (manufactured by Amano Pharmaceutical Co., Ltd.) (Ig) is added to this solution and shaken at 25° C. and 150 rpm. After 16 hours, the reaction solution was collected by filtration, and the filtrate was subjected to HPLC using an optically active column.
When measured, the optical purity of (R)-1-phenyl-2-chloroethanol was 92%.

The theoretical yield is 70%, and the (S)-ester has an optical purity of 96.
%, with a theoretical yield of 80%.

Example 4 Racemic mande oil (1.07g, 8.0m)
s+ol) Glutaric anhydride (0.5g, 4.4++
mol) was dissolved in carbon tetrachloride (10 ml) which had been previously dried overnight with molecular sieve 4A. Add Amano P (manufactured by Amano Pharmaceutical) (2 g) to this solution and heat at 25°C for 15 minutes.
Shake at 0 rpm. After 16 hours, the reaction solution was collected by filtration, and the filtrate was measured by HPLC using an optically active column. Manzolonitrile with an optical purity of 90% was obtained in a theoretical yield of 78%.
Obtained with.

Example 5 Racemic 3-chloro-t-p-toluenesulfonyloxy-2-propatol (Ig, 3.78 mmol) and hexanoic anhydride (0,446 g, 2.08 mmol) were preliminarily dried overnight with molecular sieve 4A. Dissolve in reserved carbon tetrachloride (10 ml). Add Amano P (
Add Tenshu Pharmaceutical M) (Ig), 25℃, 150rps+
Shake with After 8 hours, the reaction solution was collected by filtration, and the filtrate was measured by HPLC using an optically active column. (R)-3
-chloro-1-p-)-luenesulfonyloxy-2-
Proper tool was obtained with an optical purity of 95% and a theoretical yield of 80%.

Example 6 Racemic 2-octatool (2.6g, 20.0m+5
ol) and glutaric anhydride (1,254g, 11.0ml
tol) was dissolved in carbon tetrachloride (50 ml) that had been previously dried overnight with Molecu and Rashive 4A. Add porcine pancreatic lipase (manufactured by Sigma) (5 g) to this solution.
Shake at 150 rpm at 5°C.

After 16 hours, the reaction solution was collected by filtration, and the filtrate was measured by HPLC using an optically active column, and the same results as in Example 1 were obtained.

Claims (1)

[Claims] (1) It is characterized by preferentially and irreversibly esterifying one enantiomer of racemic alcohol using a carboxylic acid anhydride in an organic solvent in the presence of a hydrolase, and then separating the optically active form. Optical resolution method of racemic alcohol.