JPH06319589A - Production of optically active delta-lactone - Google Patents

Abstract

PURPOSE:To provide inexpensive optically active lactones having excellent flavor as perfumery raw material and applicable as a preparation raw material for perfumery. CONSTITUTION:A racemic lactone available at any time at a low cost is used as an industrial raw material and treated with a lipase originated from microorganism to effect the optical resolution of the racemic lactone. The obtained hydroxycarboxylic acid is cyclized to industrially produce R and S optically active lactones useful as preparation raw materials arbitrarily miscible at the natural existing ratio.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for optically resolving racemic lactones by lipase produced by microorganisms. More specifically, the present invention relates to a method for producing an optically active δ-lactone which is excellent in aroma and is useful as a compounding material which can be arbitrarily compounded in a natural abundance ratio.

[0002]

2. Description of the Related Art Conventionally, lactones as raw materials for compounding have been used in various fields for foods and cosmetics due to their characteristic aroma, but they are racemic lactones. Met. Due to recent advances in analytical technology, R / of lactones found in natural products
The S ratio has become clear ("12th Intern
national Congress of Flavo
urs Fragrances and Essent
ial Oils ", Vienna, Oct. 4-8, 1
992) At the same time, consumer needs have come to demand a more natural scent. Since the R-form and the S-form have different aroma characteristics, it is desired to mix them in the most suitable R / S ratio according to the purpose in order to create a more natural scent.

Some of the optically active lactones have long been known as insect pheromones, and many organic chemical synthetic methods have been tried (J. Org. Che.
m. , 44, 2169, 1979). However, the reaction steps are long, and it is difficult to prepare a chiral compound as a precursor in each case, or it is expensive even if it is commercially available, which is not suitable for providing an inexpensive preparation material.

Recently, many methods for preparing a hydroxycarboxylic acid from a keto acid by an asymmetric reduction method using baker's yeast have been introduced, and there is an example applied to a lactone synthesis method (organic synthesis). Chemistry, 49 , 37, 199
1) The product contains a large amount of yeast-derived aroma components, and there is a drawback that a further purification step is required in order to use it as a preparation material. Further, there is a problem that only (R)-(+) can be made.

The method of cyclizing a racemic hydroxycarboxylic acid with a lipase to obtain an optically active lactone is the most general method among the methods utilizing an enzyme. There is a problem such as a large amount of enzyme used for Tetrahedron
Lett. , 28, 3861, 1987).

A method for resolving racemic lactone with an enzyme of animal origin has been introduced, but only the S-form can be prepared, and the R-form cannot be prepared (Tetrahedron).
Lett. , 29, 1915, 1988).

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing an inexpensive optically active lactone which is excellent in aroma as a perfume material and can be applied as a compounding material. It is in.

[0008]

[Means for Solving the Problems] As a result of earnest research to achieve the above object, a racemic mixture was prepared by using a racemic lactone, which is always available and inexpensive, as an industrial raw material and allowed to act on lipase of microbial origin. Optical division,
The present invention has been found out that both R-form and S-form optically active lactones can be industrially produced as a useful compounding material which can be arbitrarily compounded in a natural abundance ratio.

That is, the present invention has the general formula (I)

[0010]

[Chemical 3]

Hydroxy obtained by reacting a racemic lactone represented by the formula (wherein R is a saturated linear alkyl group having 3 to 7 carbon atoms) with a lipase having an asymmetric hydrolysis ability of microbial origin. General formula (II) characterized by cyclodehydrating a carboxylic acid

[0012]

[Chemical 4]

A method for producing an optically active δ-lactone represented by the formula (wherein R is a saturated linear alkyl group having 3 to 7 carbon atoms, and a carbon atom with * is an optically active carbon atom). Is.

Any racemic lactone used in the present invention can be used as long as it is represented by the general formula (I). In the present invention, a lipase of microbial origin is allowed to act on these racemic lactones to preferentially asymmetrically hydrolyze either the R form or the S form. Then, the unreacted lactone and the produced hydroxycarboxylic acid can be separated and collected from the reaction solution for optical resolution. Then, the hydroxycarboxylic acid is subjected to a dehydration cyclization reaction according to a conventional method to obtain the objective optically active lactone of the formula (II).

By reacting the unreacted lactone obtained in the above reaction with a lipase different in optical substrate selectivity from the lipase used in the above reaction, hydroxycarboxylic acids having different optical activities can be obtained. By repeating this operation, the R-form and S-form can be collected more effectively from the racemic lactone at the same time.

The lipase used in the present invention may be any one having asymmetric hydrolyzing ability of microbial origin, and generally commercially available Pseudomonas, Candida, Penicillium, Aspergillus, Mucor, Rhizopus, The lipase produced by a microorganism of the genus Pseudomonas or Aspergillus, which has a high optical substrate selectivity for δ-lactone, can be appropriately selected from lipases derived from microorganisms such as the genus Geotricam.

Examples of commercially available lipases preferably used in the present invention are as follows.

[0018]

[Table 1]

These ribases may be used by themselves or may be immobilized.

The asymmetric hydrolysis of the present invention can be carried out according to general enzymatic reaction conditions. The reaction conditions will be described below as an example.

First, the selected enzyme is dissolved in a commonly used phosphate buffer (0.1 M, PH 7.0). The reaction is carried out by mixing racemic lactone with this enzyme solution. The ratio of substrate to buffer is 1:10 to 1:30
(Weight ratio), particularly 1:20 (weight ratio) is preferable. Regarding the ratio between the substrate and the enzyme amount, the yield and resolution are improved when the enzyme amount is large, but since the enzyme is relatively expensive, it is 1: 2 to 10 :.
It is preferably about 1 (weight ratio), particularly about 1: 1 to 3: 1. At this time, Ca salt for the purpose of precipitating the generated hydroxycarboxylic acid and BSA for the purpose of promoting the enzymatic reaction.
Etc. may be added.

Considering the optical resolution, the reaction temperature is preferably lower than a general optimum temperature, particularly preferably 0 to 10 ° C. The reaction rate is usually set to 5 to 50%, but 5 to 20% is desirable in order to increase the optical resolution. The reaction time is 5 to 100 hours, but the reaction temperature, the type of enzyme,
It can also be shortened by changing the enzyme concentration, substrate concentration, and reaction rate.

In this way, after the optical resolution by the hydrolysis reaction of the racemic lactone, the enzymatic reaction is stopped by an appropriate means to separate the hydrolysis product and the unreacted lactone.
An example of a method of stopping the enzymatic reaction is a method of adding a filter aid such as Celite or Radiolite. The pH of this filtrate is 7.5-11.0, preferably 8.0-8.
After adjusting to 5, unreacted lactone is extracted from this filtrate with an organic solvent. As the organic solvent used at this time, a solvent having a relatively low polarity such as pentane, hexane or heptane is preferable.

The separated organic solvent fraction can be washed with water, dried and concentrated by a conventional method to recover unreacted lactone. This unreacted lactone can be used in the next enzymatic reaction. The pH of the filtrate containing hydroxycarboxylic acid is usually 0.0 to 4.0, more preferably 2.0.
Adjust to ~ 3.0 and extract with a relatively high-quality organic solvent such as diethyl ether or toluene. The separated organic layer is similarly washed with water, dried and concentrated to obtain a hydroxycarboxylic acid concentrate.

For the conversion of hydroxycarboxylic acid to lactone, a generally used dehydration cyclization reaction can be applied. For example, by heating in an organic solvent in the presence of an ordinary acid catalyst, a dehydration reaction easily occurs and cyclization occurs. As an example, 0.5% of paratoluenesulfonic acid (PTS) is added to hydroxycarboxylic acid, and azeotropic dehydration operation is performed in toluene to perform cyclization reaction of hydroxycarboxylic acid. After the layer is washed with 5% aqueous sodium hydrogen carbonate, toluene is removed by conventional washing, drying and concentrating operations to obtain the desired optically active lactone. Further, if necessary, it is also preferable to carry out purification by a simple purification operation such as a rectification method or a column chromatography method.

[0026]

EXAMPLES The present invention will be described in detail below with reference to Examples, but it goes without saying that the present invention is not limited thereto.

Example 1 200 ml of 0.1 M phosphate buffer was cooled to 0 ° C., and Pseudomonas lipase, Lipase P (Nagase Seikagaku Corporation)
After suspending 5.0 g, racemic δ-decalactone 1
0 g was added, and the reaction was carried out for 48 hours while shaking at 100 rpm. After the reaction, add Radiolight # 2000,
The filtrate was obtained by suction filtration. The pH of this filtrate was adjusted to 8.0 and then extracted with hexane. 5% of this hexane
The solution was washed with aqueous sodium hydrogen carbonate, and the washing solution was mixed with the filtrate portion and subjected to the next treatment. The organic layer was washed with water and dried, and then hexane was distilled off under reduced pressure to recover 7.98 g of unreacted δ-lactone. GC equipped with a chiral column (Chiraldex G-TA,
It was R: S = 45: 55 from the measurement of 0.25 mm × 10 m. The pH of the filtrate portion mixed with the above washing solution was adjusted to 2.0.
After that, the reaction product hydroxycarboxylic acid was extracted with diethyl ether. As a result of performing a recovery operation from this ether layer in a usual manner, δ-hydroxydecanoic acid 0.7
0 g was obtained. 0.5% (3.5 mg) of PTS catalyst was added, and azeotropic dehydration operation was performed using toluene as a solvent to carry out the cyclization reaction of the hydroxycarboxylic acid. The toluene layer was washed with water and dried, and then toluene was distilled off under reduced pressure to obtain the δ-
0.67 g of decalactone was obtained. Result of GC measurement R: S
= 89.7: 10.3, the optical purity was 79.4%.

Example 2 The unreacted δ-decalactone obtained in Example 1 (R: S =
45:55) 7.98 g was used to perform a reaction with 4.0 g of Aspergillus lipase and lipase AP4 (Amano Pharmaceutical Co., Ltd.) in 160 ml of 0.1 M phosphate buffer at 0 ° C.
As a result of the same operation, 5.25 g of unreacted lactone (R: S
= 55:45) and 0.95 g of the δ-decalactone.
(R: S = 8.5: 91.5, optical purity 83.0% e
e) was obtained.

As a result of using Aspergillus genus lipase with racemic δ-decalactone (8 g) as a substrate instead of the unreacted recovered lactone (R: S = 45: 55) used in Example 2, the yield was The yield with respect to the substrate was 0.72 g, which was low. Therefore, the reaction proceeds more efficiently when a raw material having a high optical purity is used as a substrate.

Example 3 The same operation was carried out by substituting the racemic δ-decalactone as the substrate used in Example 1 for the racemic δ-dodecalactone. Optical purity R: S = 90.0: 10.0, R: S =
It was possible to obtain 8.8: 91.2 of δ-dodecalactone, respectively.

Example 4 Substantially similar results were obtained by replacing the racemic δ-decalactone, which is the substrate used in Example 1, with the racemic δ-octalactone.

Comparative Example 1 0.70 g of a reaction product was prepared in the same manner as in Example 1, except that the Pseudomonas lipase used in Example 1 was replaced with a Mucor lipase.
However, optical resolution was not performed at all.

[0033]

EFFECTS OF THE INVENTION Both R-form and S-form optically active δ-lactone can be produced by using a riboase having different optical substrate selectivity with respect to δ-lactone. There is an effect that can be used as a material.

Further, in the present invention, two kinds of revertases having different optical substrate selectivity are sequentially and repeatedly acted on the recovered unreacted lactone having an optically active form to efficiently
Both R-form and S-form δ-optically active lactone can be produced.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C12R 1:66)

Claims (3)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R is a saturated straight chain alkyl group having 3 to 7 carbon atoms) A racemic lactone represented by the formula (3) is caused to act on a lipase having asymmetric hydrolyzing ability of microbial origin to give the resulting hydroxycarboxylic acid. General formula (II) characterized by dehydration cyclization (In the formula, R is a saturated linear alkyl group having 3 to 7 carbon atoms, and the carbon atom with * is an optically active carbon atom.)
A method for producing an optically active δ-lactone represented by: 2. The method for producing an optically active δ-lactone according to claim 1, wherein the lipase of microbial origin used is a lipase of Pseudomonas genus and Aspergillus genus. 3. A racemic lactone is reacted with a lipase having an optical substrate selectivity of one of a lipase of Pseudomonas origin and a lipase of Aspergillus origin, which have different optical substrate selectivity, and either R-form or S-form. The one reaction product is obtained, and the unreacted lactone recovered by this operation is further subjected to sequential optical resolution by a lipase having an optical substrate selectivity different from that of the lipase used in the previous reaction. A method for producing the optically active lactone described.