JPH02142495A - Production of optically active alcohol - Google Patents

Abstract

PURPOSE:To efficiently and readily obtain an optically active alcohol at a low cost by mixing a specific racemic alcohol and anhydride of an organic acid with an organic solvent, reacting a specified enzyme therewith and then treating the reaction product with an aqueous solution of a weak basic inorganic salt. CONSTITUTION:A racemic alcohol, expressed by the formula (R1, R2 and R3 are H, halogen or 1-20C aliphatic hydrocarbon, aromatic hydrocarbon group which may have halogen or amine as a substituent group) and having asymmetric carbon atom in the molecule and anhydride of an organic acid mixed with a water-immiscible organic solvent and an enzyme having stereoselective esterifying action is then reacted with the resultant mixture to simultaneously carry out eserification and introduction of carboxyl group. The mixture is subsequently treated with an aqueous solution of a weak basic inorganic salt to convert the carboxyl group into an inorganic salt, which is then passed into an aqueous layer to afford the objective alcohol.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention utilizes the stereoselectivity of enzymatic reactions to obtain compounds of the general formula % formula % (wherein R', R'' and R'' are each hydrogen.

It represents either a halogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group, and the hydrocarbon group may have a halogen or amine as a substituent. ) and an anhydride of an organic acid, one of the optical isomers in the racemic alcohol is esterified by the action of lipase, and the carboxyl group is removed. The present invention relates to a method for producing an optically active alcohol by introducing the alcohol, separating it from the other optical isomer alcohol as an inorganic salt by treatment with an aqueous solution of a weakly basic inorganic salt, and recovering it as an alcohol or epoxide by alkaline decomposition.

The optically active alcohol and epoxide obtained by the present invention are extremely versatile compounds that can be used as starting materials for the synthesis of optically active compounds such as medicines, agricultural chemicals, physiologically active substances, and liquid crystalline compounds.

[Conventional technology]

Generally, the method of separating optical isomers from racemic alcohols by chemical resolution requires expensive reagents and complicated steps, and the optical purity of the obtained product is also not very good. Therefore, in recent years, biochemical optical resolution methods using enzymes derived from microorganisms and utilizing their stereoselectivity have been actively researched, and many reports have been made. These methods include: ■Asymmetric hydrolysis of racemic esters by lipase or esterase; ■Asymmetric ester synthesis between racemic alcohol and fatty acid; and ■Asymmetric ester synthesis between racemic alcohol and fatty acid ester. Both methods use reactions such as rearrangement to produce optically active alcohols and their fatty acid esters from racemic alcohols.

Special Publication 57-29 as a report on the asymmetric hydrolysis of
No. 152, Japanese Unexamined Patent Publication No. 62-29993, No. 62
-65688 publication, 63-63398 publication,
S. Hamaguchi et al. (Agric, Bi
ol, Chem, 48.2055 (1984), D
, Breit5+('f--- et al., (J, Chem
, Soc., 1523 (1986)), etc., but as a report on the asymmetric ester synthesis of ①, Koshiro et al.
nol.

2, 47 (1985)), Cambou et al.
Am, Chem.

Soc, 106.2687 (1984))
The method described in JP-A-62-166898, C.
ambou et al. (Biotechnol, Bioeng
, 26.1449 (1984)). All of these reactions have their own advantages depending on the purpose, but they have one thing in common: column chromatography must be performed to separate and purify the optically active alcohol and optically active ester obtained from racemic alcohol. It has major drawbacks. Including a column chromatography step in the manufacturing process not only makes large-scale manufacturing difficult, but also requires large equipment and operating costs, which is not preferable for industrial scale manufacturing.

It has been desired to develop a method that solves these problems and efficiently resolves racemic alcohols on an industrial scale and easily and inexpensively separates and purifies them.

[Problem to be solved by the invention]

As mentioned above, the chemical method for optical resolution of racemic alcohols has problems such as the need for expensive reagents and complicated steps. Furthermore, in the conventional biochemical resolution of racemic alcohol using an enzymatic method using lipase, the optically active alcohol and ester produced during the production process are separated and purified, so it is not suitable for large-scale processing. This method also has problems such as requiring costly column chromatography operations.

However, the optical resolution of pacific alcohol using lipase reaction is a much more efficient method than chemical methods, so it can be used more easily and in large quantities instead of column chromatography during the above separation and purification process. If a suitable method can be used, the production of optically active alcohols from racemic alcohols using enzymes will become a reality, and the present invention attempts to realize this.

[Means to solve the problem]

As mentioned above, the methods for producing optically active alcohols by optical resolution of racemic alcohols by chemical methods and conventional enzymatic methods using lipase both have drawbacks, and it is currently difficult to perform them on an industrial scale. However, the enzymatic method using lipase has advantages over the chemical method, such as not using expensive reagents and the resulting product having high optical purity, so it does not require the column chromatography procedure described above. We thought that it would be an extremely practical method if two types of optical isomers could be easily separated and purified. Therefore, the present inventors have conducted intensive research on a method that can separate and purify the optical isomers in racemic alcohol without using column chromatography. An enzyme such as lipase is applied to the mixture under specific conditions to esterify one of the optical isomers, and the inorganic salt is separated from the other optical isomer alcohol, and then the inorganic salt is decomposed with alkaline to form alcohol or epoxide. The present invention was completed by discovering a method to replace the above.

That is, the present invention relates to the general formula % (wherein R1, R1 and R3 each represent hydrogen, halogen, or an aliphatic hydrocarbon group having 1 to 20 carbon atoms or an aromatic hydrocarbon group, and The hydrogen group may have a halogen or amine as a substituent.) A racemic alcohol having an asymmetric carbon atom in the molecule and an anhydride of an organic acid are mixed with a non-water miscible organic solvent. Then, without substantially adding water, an enzyme having a stereoselective ester action is allowed to act on the mixture to esterify one optical isomer in the racemic form of the alcohol and introduce a carboxyl group. After that, it is transferred to the aqueous layer as an inorganic salt by treatment with an aqueous solution of a weakly basic inorganic salt, separated from the other optical isomer alcohol remaining in the organic solvent layer, and the alcohol is collected and the inorganic salt is treated with an alkali. The present invention provides a method for producing an optically active alcohol, which is characterized in that an alcohol or an epoxide is produced by decomposition and collected.

The racemic alcohol used in the present invention is represented by the general formula % (in the formula, R1, R1 and R3 are the same as above) and has an asymmetric carbon in the molecule, specifically, (R,5)-1-phenylethanol.

(R,5)-2-chloro-1-phenylethanol,
(R,5)-2-octatool and the like.

Next, the organic acid anhydride used in the present invention is not particularly limited, and specific examples include succinic anhydride, glutaric anhydride, and phthalic anhydride.

In the present invention, there is no particular restriction on the water-immiscible organic solvent in which the racemic alcohol and organic acid anhydride are mixed, such as diethyl ether.

Hexane, cyclohexane, benzene, toluene.

Examples include chloroform, carbon tetrachloride, dichloromethane, and the like.

Further, as the enzyme used in the present invention, any enzyme may be used as long as it can selectively esterify one of the optical isomers in the racemic alcohol by a transesterification reaction with the anhydride of the above-mentioned organic acid. Specifically, the genus Pseudomonas.

Examples include lipases derived from microorganisms belonging to the genus Chromobacteria or Candida. For more information, see Pseudomonas fluorescens
as fluor-escens) + Pseudomonas 0 fragi (Pseudomonas red u
nas n1troreduecens), Chromobacterium 6 viscosum (Chromobacterium 6
m viscosum).

Candida cylindracea (CandidaΩli)
Examples include lipases derived from N. dracea) and the like.

Commercial products of these lipases include Lipase P (manufactured by Amano Pharmaceutical Co., Ltd.), Lipase B (manufactured by Sarapolo Beer Co., Ltd.), Lipase LP (manufactured by Toyo Jozo Co., Ltd.), and Lipase OF.

Examples include Lipase MY (manufactured by Awa-Nori Sangyo Co., Ltd.). Such lipase may be used as it is, but the lipase may be used as a photocrosslinkable prepolymer having a main chain of polyethylene glycol, polypropylene glycol, etc., such as ENT-1000, ENT-2000゜ENT-3 manufactured by Kansai Paint Co., Ltd.
000,ENTP-1000,ENTP-2000,E
Those that have been comprehensively immobilized using NTP-3000°ENTP-4000, etc., those that have been comprehensively immobilized using urethane prepolymer manufactured by Toyo Rubber Industries, Ltd., and various ion exchange resins, celite, bentonite, and alumina.

It is also possible to use one immobilized using an immobilization carrier such as zeolite glass beads or an inorganic material such as silica gel.

In the present invention, the racemic alcohol and anhydride of an organic acid are placed in an organic solvent, and the enzyme is allowed to act without substantially adding water. In the present invention, "without substantially adding water" does not mean that no water is present in the reaction system, but rather that some water is contained in the organic solvent and the enzyme agent. , refers to a slightly aqueous state in which water necessary for the stability of the enzyme is secured in the reaction system without adding new water to the reaction system.

In the present invention, the blending ratio of the racemic alcohol and the organic acid anhydride is the former: the latter = 1:0.5-2 (molar ratio), preferably 1:o, s-l (molar ratio). , and the concentration of these substrates in the organic solvent is 0.5 to 5 molar concentration, preferably 1 to 2 molar concentration, and the above enzyme is added in an amount of 1 to 100 g, preferably 5 to 50 g per mole of racemic alcohol. Add and react. Reaction is from 0 to 50°
C1 Usually carried out at 10 to 30°C, and heated for 1 to 24 hours while shaking or stirring to properly disperse the enzyme in the reaction system.
It is desirable to carry out the treatment for a period of time, preferably 3 to 10 hours. After the reaction is completed, the enzyme can be easily separated from the reaction solution and reused by filtering it through a filter paper such as Toyo Roshi No. 2.

Since the optically active ester produced by the reaction contains a carboxyl group, it is neutralized with an aqueous solution of a weakly basic inorganic salt and transferred to the aqueous layer as a metal salt, and the optically active alcohol remaining in the reaction water-immiscible organic solvent is removed. can be easily separated.

The weakly basic inorganic salt used in the present invention is not particularly limited, but includes sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and the like.

The obtained metal salt of carboxylic acid can be obtained as an optically active alcohol or epoxide by alkali decomposition and solvent extraction using ether, etc., and purified by washing with water, dehydration, and concentration.

〔Example〕

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Optical resolution of (R,5)-1-phenylethanol<17,5)-1-phenylethanol 1 mol (1
22g) and succinic anhydride 1 monoden 100) 1! The predetermined amounts of lipase shown in Table 1 were added to the mixture of diethyl ether and the mixture was stirred with a stirrer at 25°C for 4 to 9 hours until the alcohol conversion rate reached about 50%. went. 1- produced by the reaction
The half ester of phenylethanol and succinic anhydride and the remaining 1-phenylethanol were analyzed by HPLC.
was quantified and the exchange rate was calculated. HPLC conditions are described below.

Column; Asahipak 0DP-50,4,6X
150 mm (manufactured by Asahi Kasei Co., Ltd.) Mobile solvent; methanol: water-7,3 (, H3,0) detector; ultraviolet detector (manufactured by Ohyo Bunko Co., Ltd., UVILOG-7)
Measurement wavelength: 215 nm Column temperature: 25"C After the conversion rate of alcohol to half ester reached approximately 50%, the enzyme agent was removed from the reaction solution for 1'4 minutes, and the reaction solution was transferred to Toyo Roshi No. , 2.Next, 1! of a 1 molar sodium carbonate aqueous solution was added to the filtrate, thoroughly stirred, and left to separate into an aqueous layer and an ether layer.By this operation, unreacted alcohol was converted into ether. The monoester formed in the layer became a sodium salt and transferred to the aqueous layer. Next, the ether layer was washed with water, dehydrated with magnesium sulfate, and concentrated using an evaporator, and almost all optically active (S)-1-phenylethanol was removed. Obtained in pure form.

On the other hand, the aqueous layer was washed with diethyl ether, and then 1r of 2N sodium hydroxide was added and stirred to break the ester bond of the ester and generate alcohol again. The produced alcohol was extracted with diethyl ether, washed with water, dehydrated with magnesium sulfate, and concentrated using an evaporator to obtain optically active (R)-1-phenylethanol in a substantially pure form. Note that no diester was produced by this reaction.

The weight of each optically active l-phenylethanol obtained was measured to determine the yield.

Further, the optical purity (%ee) was determined by HPLC using a column for separating optical isomers. HPLC conditions are shown below.

Column: CHIRALCEL OB (manufactured by Daicel Chemical Co., Ltd.) Mobile phase solvent: Hexane:isopropyl alcohol = 9:1 Detector: Ultraviolet detector (manufactured by Oyo Bunko Co., Ltd., UVILOG-
7) Measurement wavelength: 260 nm Column temperature: 25°C The obtained results are shown in Table 1.

Example 2 Optical resolution of (R,5)-2-chlorophenylethanol 1 mol (156 g) of (R,5)-2-chloro-1-phenylethanol and 1 mol (100 g) of succinic anhydride
A predetermined amount of lipase shown in Table 2 was added to the diethyl ether mixture in Step 1, and the reaction was continued at 25°C for 8 to 10 hours while stirring with a stirrer until the alcohol conversion rate reached approximately 50%. went. The half ester of 2-chloro-1-phenylethanol and succinic anhydride produced by the reaction and the remaining 2-chloro-1
-Phenylethanol was quantified by +1PLc and the conversion rate was calculated. Note that the conditions for HPL (/-) were the same as in Example 1.

After the conversion rate of alcohol to half ester reached about 50%, the half ester produced and the remaining alcohol were separated by the same operation as in Example 1.

When the remaining alcohol was purified, optically active (S)-
2-chloro-1-phenylethanol was obtained in almost pure form. The optically active (S)-2-chloro-■
- Optical purity (%ee) of phenylethanol was determined in the same manner as in Example 1.

On the other hand, when the half ester produced was subjected to alkaline decomposition and then ether extraction, optically active epoxide (styrene oxide) was obtained in a substantially pure form. The optical rotation of the obtained optically active styrene oxide was measured, and the specific rotation ([α].) was determined from the measured value, and this was calculated as the specific rotation R-( +
) body ([α), = +34.1°, ethanol), 5
The optical purity (%ee) was determined by comparison with the -(-) form ([α)M = 34.1°, ethanol).

The results obtained are shown in Table 2. It should be noted that no diester was produced at all in this reaction.

Example 3 Optical resolution of (R,5)-2-octatool (R
, 5) A predetermined amount of lipase shown in Table 3 was added to a mixture of 1 mol (130 g) of -2-octatool and 291 mol (100 g) of anhydrous comb in diethyl ether of 11, and the mixture was heated at 25°C. The reaction was carried out for 1.5 to 50 minutes while stirring with a Starcy until the conversion of alcohol reached about 50%.
I went for 7 hours. The half ester of 2-octatool and succinic anhydride produced by the reaction and the remaining 2-
Octatool was quantified by II PLC and the conversion rate was calculated. Note that the conditions for IIPLc were the same as in Example 1.

The conversion rate of alcohol to half ester is approximately s.

%, the half ester produced and the residual alcohol were separated by the same operation as in Example 1.

When the remaining alcohol was purified, optically active (S)=
2-octatool was obtained in almost pure form.

On the other hand, when the generated half ester was subjected to alkaline decomposition and ether extraction, optically active (R)-2 octatool was obtained in a substantially pure form. The optically active (S
)-2-octatool and (R)-2-octatool, and from that value the specific optical rotation ([α]
. ) and calculate the specific optical rotation of the chemically and optically pure commercially available standard product R-(-) form ([α].-10°, ethanol) and S-(+) form ([α] Optical purity (%ee) was determined by comparing with .=+10°, ethanol). The results obtained are shown in Table 3. It should be noted that no diester was entirely produced by this reaction.

According to the present invention, by utilizing the stereoselectivity of the enzymatic reaction, it is possible to efficiently perform optical resolution of various racemic alcohols through the stereoselective ester formation reaction. Also,
The present invention does not require column chromatography to separate optical isomers, and uses inexpensive industrial raw materials as acyl donors and enzyme agents. This is a realistic method for producing active alcohols and epoxides, and is unprecedented and revolutionary.

Patent applicant: Sapporo Beer Co., Ltd.

Claims (1)

[Claims] (1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R^1, R^2 and R^3 are hydrogen,
It represents either a halogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, or an aromatic hydrocarbon group, and the hydrocarbon group may have a halogen or amine as a substituent. ) A racemic alcohol having an asymmetric carbon atom in the molecule and an anhydride of an organic acid are mixed with a non-water miscible organic solvent, and the mixture is subjected to stereoselectivity without substantially adding water. One of the optical isomers in the racemic form of the alcohol mentioned above is esterified by the action of an enzyme having a chemical ester action, and after introducing a carboxyl group, it is converted into an inorganic salt by treatment with an aqueous solution of a weakly basic inorganic salt. The alcohol is transferred to an aqueous layer, separated from the other optical isomer alcohol remaining in the organic solvent layer, and the alcohol is collected, and the inorganic salt is alkali decomposed to generate and collect alcohol or epoxide. Method for producing optically active alcohol.