JP2643105B2 - Partially methylated cyclodextrin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a partially methylated cyclodextrin having improved solubility in water.

[0002]

2. Description of the Related Art As methylated cyclodextrin (hereinafter sometimes abbreviated as "CD"), hexakis-
(2,6-di-O-methyl) α-CD, heptakis-
(2,6-di-O-methyl) β-CD, heptakis (2,
3,6-tri-O-methyl) β-CD, and as a method for producing these, CD is converted to an organic compound such as N, N-dimethylformamide (hereinafter referred to as “DMF”) or dimethyl sulfoxide (hereinafter referred to as “DMSO”). Reacting dimethyl sulfate or methyl iodide as a methylating agent in the presence of barium oxide and / or barium hydroxide in a solvent,
15 to 40 molar equivalents of NaO in aqueous solution with respect to CD
A method of reacting 9 to 30 times the molar equivalent of dimethyl sulfate in the presence of H is known (for example, Chemical Abst
ract 98 , 108 (1983); Starch / Staerke 3
2 , Nr, 5, 165-169 (1980)).

[0003]

CD is an oligosaccharide in which glucose units are linked in a cyclic manner by α-1,4 bonds, and is a host molecule that includes various organic compounds.
It is used in the fields of pharmaceuticals, pesticides, foods, flavors, cosmetics and baths.

However, CDs are not only poorly soluble in water but also poorly soluble in organic solvents such as alcohols, which hinders universal application in the above-mentioned fields. Above all, β-CD (seven glucose units), which is widely used for inclusion, has a low water solubility, and has a drawback that the concentration used is limited.

On the other hand, the above-mentioned known methylated CD has been prepared mainly for the purpose of studying its molecular structure, and as described later, its solubility in water has been somewhat improved. As the temperature increases, its solubility decreases, and it cannot be said that the above disadvantages have been solved.

The above-mentioned so-called fully methylated CD,
For example, heptakis- (2,3,6-O-methyl) β-CD
Production of partially methylated CDs is also known in the production of such compounds, but it is not clear what physicochemical properties they exhibit (see, for example, West German Patent Application No. 3).
No. 118218).

[0007]

SUMMARY OF THE INVENTION The present inventor has determined that β-CD is less soluble in various solvents than other linear oligosaccharides composed of the same number of glucose units because of its unique molecular structure. Noting that there is a known methylated β-CD
Various methylated β- to break the symmetry of the molecular structure of
We examined CD.

As a result, when β-CD is reacted with an excessively high concentration of dimethyl sulfate as a methylating agent in an unusually high concentration of sodium hydroxide aqueous solution, complete methylation of the hydroxyl groups at the 2- and 3-positions of glucose constituting the CD may occur. Without adjusting their methylation rate. Further, the thus obtained partially methylated composition having a specific methylation ratio has surprisingly improved water solubility as compared with the above-mentioned fully methylated β-CD and the like, and completed the present invention. In the composition thus obtained, the average methylation rate of the hydroxyl group at each position of unit glucose is 2nd position: about 53 to 64% 3rd position: about 38 to 51% 6th position: about 70 to 100% Is a mixture of activated β-cyclodextrins.

The partially methylated β-CD composition has the following formula:

[0010]

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In the formula, R represents a hydrogen atom or a methyl group, and the average methylation ratio at each position of the partially methylated β-cyclodextrin represented by the above formula is the above value.

The composition is prepared by thin-layer chromatography on silica gel (developing solvent: chloroform / methanol = 9 /
When subjected to 1), the Rf value as a main component is about 0.5
5, 0.42 and 0.30 are obtained as a mixture of components, and each component can be isolated by an appropriate separation means. Note that the Rf value slightly varies depending on the operating conditions as in the case of a general sugar derivative.

[0013] Such partially methylated β-CD is useful as a mixture itself as a solubilizing and clathrating agent for various poorly water-soluble compounds, but considering its use in the technical field where more uniform specifications are required, If necessary, it is preferable to separate and use the individual components exhibiting respective Rf values.

Therefore, according to the present invention, (A) silica gel thin layer chromatography [thin layer: Merck, Art
5744; developing solvent system: chloroform-methanol (9: 1)], the Rf value was 0.55, and (B) the methylation ratio calculated by the gas chromatography method after the pretreatment was as follows: For each hydroxyl group, 55.6% at the 2nd position, 45.7% at the 3rd position,
A partially methylated-β-cyclodextrin is provided, wherein position 6 is 100%.

The “gas chromatography method after pretreatment” referred to in the present invention means a method described later in detail. That is, more specifically, a value calculated by the following method is used.

Calculation method of methylation rate [A] Preparation of sample for measuring methylation rate 1) Hydrolysis About 100 mg of methylated β-CD was dissolved in 4.25 ml of water, and 0.75 ml of trifluoroacetic acid was added. Heat at 0 ° C. overnight. The reaction solution is concentrated under reduced pressure to remove trifluoroacetic acid. A small amount of water is added to the residue, and the mixture is concentrated again under reduced pressure.

2) Reduction The concentrated residue is dissolved in 5 ml of water and cooled in an ice water bath. After adding 0.56 g of sodium borohydride little by little,
Stir at 4 ° C. for 4 hours. After the reaction, excess sodium borohydride is decomposed with 30% acetic acid. After stirring at 20 ° C. for 1 hour, Amberlite IR-120B (H ⁺ f
orm) and concentrated under reduced pressure. A small amount of methanol is added to the residue, and the mixture is concentrated again under reduced pressure.

3) Acetylation To the concentrated residue, 10 ml of pyridine and 5 ml of acetic anhydride were added to obtain a residue.
After stirring at ℃ overnight, the reagent is distilled off under reduced pressure. The distillation under reduced pressure is performed at 40 ° C. or less. To the residue is added 60 ml of chloroform, washed with saturated saline, dried over sodium sulfate and concentrated. 1 ml of acetone is added to the residue to prepare a sample for gas chromatography (GC).

[B] GC analysis conditions Column: 3% ECNSS-M (Shimadzu Corporation) 2mx3m
mφ Support: Chromosorb W (AW-DMCS) 100-1
20 mesh Column temp: 180 ° C. Injection temp: 260 ° C. N ₂ flow rate: 22.5 ml / min H ₂ press: 0.6 kg / cm ² [C] Calculation of methylation rate Gas chromatography as shown in FIG. Based on the results of the above, the respective proportions of acetylglucose methylated at each position were determined, for example, the methylation rate at the 6-position was 6-
It was calculated as the sum of the proportions of all acetyl glucose containing O-methyl.

The partially methylated-β-cyclodextrin of the present invention can be produced by isolating a product obtained by the following method by a suitable means.

That is, β-CD and dimethylsulfuric acid are converted from dimethylsulfuric acid to β-CD in an aqueous solution of sodium hydroxide of 10% or more (weight / volume: hereinafter, simply expressed by%). Various partially methylated β-CDs can be obtained by reacting at least 20 times the molar equivalent.

The product thus obtained is generally represented by (i)
It has an Rf value of 0.55, and has an average methylation rate of 55 to 64% at position 2, 43 to 51% at position 3, and 99 to 6 at position 6.
Melting point (capillary method): 142-1
61 ° C., and specific rotation: [α] ²⁵ _D 158 to 162 °
Partial methylated-β-CD mixed composition showing (c = 1, water); (ii) Rf value 0.42, average methylation rate: 2nd position 55-60%, 3rd position 39-45%, 6 86-88%
Melting point (same as above): 159 to 170 ° C., specific rotation: [α] ²⁵
_D A partially methylated-β-CD mixed composition exhibiting 156 to 159 ° (c = 1, water); or (iii) an Rf value of 0.30, an average methylation rate: 53 to 61% at 2nd position, 3 3rd place
8-45%, 6-position 70-77%, melting point (same as above): 167
180, specific rotation: [α] ²⁵ _D 155-159 ° (c
= 1, water), a partially methylated-β-CD mixed composition,
The main thing.

In the above method, the concentration of the aqueous sodium hydroxide solution is not less than 10%, and the upper limit thereof is not limited as long as the concentration can substantially perform the present reaction, but the above three main components ((i) to (iii)) Among them, in order to increase the generation rate of the component (i), 30 to 40% is preferable.

In order to achieve the same object, it is desirable to use dimethyl sulfate at a molar equivalent of 60 to 130 times that of β-CD.

The reaction temperature is not particularly limited as long as β-CD is not substantially decomposed, but it is preferable to carry out the reaction at about 0 to 10 ° C. The reaction time varies depending on the concentration of the aqueous sodium hydroxide used and the reaction temperature,
It is not critical, but should be selected in the range of about 7 to 20 hours.

The method for isolating and purifying the target component from the reaction mixture is generally a method of removing a fat-soluble substance from an aqueous solution such as a hydrocarbon such as chloroform, dichloromethane, and carbon tetrachloride, and an aromatic hydrocarbon such as benzene, toluene and xylene. The extraction can be carried out by an extraction method using an organic solvent used in the extraction, or by column chromatography using silica gel, alumina gel, activated carbon or the like.

Table 1 below shows the production ratio of each partially methylated β-CD under various reaction conditions.

Table 1 NaOH concentration (CH ₃ ) ₂ SO ₄ amount Reaction temperature Product composition (%) * (%, w / v) (Equivalent: β-CD) (° C.) 0.55 0.42 0.30 10 20 0 5 7.3 20.7 34.9 20 20 -10 to 0 3.1 14.1 34.9 30 200 to 10 17.5 33.1 31.8 40 200 to 0 36.5 33.5 22.2 10 30 0 to 5 16.7 23.1 28.1 30 300 to 100 47.2 36.8 13.5 40 30 to 0 66.6 26.9 5.5 40 40 to 10 85.0 13.4 1.4 40 60 to 10 92.4 7.0 0.6 40 100 to 10 98.5 1.5-10 130 0 to 5 29.6 40.0 22.3 20 130 to 10 76.2 20.6 3.0 30 130 0 to 105.5 5.5 0.4 40 130 to 10 98.7 1.3- * The sample was extracted with CHCl ₃ from the reaction solution, developed by silica gel TLC (developing system: CHCl ₃ -MeOH = 9: 1), and sulfuric acid was colored. Relative value measured by chromatoscanner.

[0029]

The present invention will be described in more detail with reference to the following examples.

Reference Example 1 β-CD (RINGDEX-B, manufactured by Mercian Corporation) 75.0
g (6.61 × 10 ^-2 mol) in 40% (wt / v) N
The solution was dissolved in 400.0 ml (4.00 mol, 60-fold molar equivalent of β-CD) of an aqueous aOH solution, and 375.5 ml (3.97 mol, β-CD
(Double molar equivalent) was gradually added dropwise, and the reaction was continued under stirring for further 15 hours. After the reaction, 110 ml of concentrated aqueous ammonia (1.63
Mol) is added to decompose unreacted dimethyl sulfuric acid.
Stirred for hours. The reaction solution was neutralized with dilute hydrochloric acid to adjust the pH to about 6. 1 l of chloroform was added, and the partially methylated β
-CD was extracted and the chloroform layer was washed several times with water.
After the chloroform layer was dried over sodium sulfate, chloroform was distilled off, and the residue was dissolved in 200 ml of ethanol, and the solvent was distilled off. Further, 200 ml of water was added to obtain an aqueous solution, which was concentrated to dryness to obtain 71.1 g of partially methylated β-CD.

The specific rotation [α] ²⁵ _D of the obtained partially methylated β-CD is + 161.3 ° (c = 1.0, water), melting point 1
44.5 to 152.0 ° C., and the solubility was as shown in FIG.

As a result of analyzing the methylation rate by gas chromatography, the methylation rate of the hydroxyl group at each position in the unit glucose of the total glucose was as follows.

Second place 56.8% Third place 46.4% Sixth place 98.9% Average 67.4% Example β-CD (RINGDEX-B, Mercian Co., Ltd.) 80.0
g (7.05 × 10 ^-2 mol) in 40% (wt / v) N
Dissolved in 282.0 ml (2.12 mol, 30-fold molar equivalent of β-CD) of an aOH aqueous solution, and at a reaction temperature of 0 to 10 ° C., 20.2 ml (2.11 mol, β-CD 30
(Double molar equivalent) was gradually added dropwise, and the reaction was continued under stirring for further 15 hours. After the reaction, 60 ml (0.89 mol) of concentrated aqueous ammonia was added to decompose unreacted dimethyl sulfate, and the mixture was further stirred for 6 hours. The reaction solution was neutralized with dilute hydrochloric acid to adjust the pH to about 6. Partially methylated β-C with 800 ml of chloroform
D was extracted and the chloroform layer was washed several times with water. After the chloroform layer was dried over sodium sulfate, chloroform was distilled off, the residue was dissolved in 200 ml of ethanol, and the solvent was distilled off.
Further, 200 ml of water was added to obtain an aqueous solution, which was then concentrated to dryness to obtain 80.4 g of partially methylated β-CD.

The specific rotation [α] ²⁵ _D of the obtained partially methylated β-CD is + 159.7 ° (c = 1.0, water), melting point 1
As a result of analysis of the methylation rate by gas chromatography at 49.4 to 158.3 ° C., the methylation rate of the hydroxyl group at each position in the unit glucose of the total glucose was as follows.

24.1% 54.1% 3rd 43.5% 6th 88.6% Average 62.1% Take 420 mg of the resulting mixture of partially methylated β-CD, dissolve in a small amount of chloroform-methanol, Silica gel thin layer chromatography (Merck, Art 574)
(4, 20 × 20 cm × 15) and purified and separated in a chloroform-methanol developing system to obtain three main components. The yield and physical properties of the three components obtained were as shown below. The methylation analysis of each component was performed by gas chromatography.

Constituent component 1 Yield: 220 mg, Rf value: 0.55 (provided solvent: chloroform-methanol (9: 1)), [α] ²⁵ _D :
+ 160.1 ° (c = 1.0, water), melting point 152.5-1
60.0 ° C., solubility 133 g / 100 ml water (25
° C), methylation rate (position is hydroxyl group of constituent glucose unit) 2nd position 55.6% 3rd position 45.7% 6th position 100% average 67.1% Constituent 2 97 mg, Rf value 0.42 (however, , Developing solvent system chloroform-methanol (9: 1)), [α] ²⁵ _D : +
158.2 ° (c = 1.0, water), melting point 161.5-16
7.0 ° C, methylation rate (position is hydroxyl group of constituent glucose unit) 2nd position 55.6% 3rd position 42.7% 6th position 87.5% Average 61.9% Component 3 Yield 28 mg, Rf value 0 .30 (however, developing solvent system chloroform-methanol (9: 1)), [α] ²⁵ _D : +
158.2 ° (c = 1.0, water), melting point 167.0-17
3.5 ° C., methylation rate (position is hydroxyl group of constituent glucose unit) 2nd position 52.8% 3rd position 40.6% 6th position 77.4% average 56.9% Reference Example 2 β-CD (RINGDEX-B , Manufactured by Mercian Corporation) 250.
0 g (2.20 × 10 ^-1 mol) is converted to 40% (wt / v)
2860 ml of an aqueous NaOH solution (28.6 mol, β-CD
At a reaction temperature of 0 to 15 ° C. and 2700 ml of dimethyl sulfate (28.6 mol, 1 part of β-CD).
(30 molar equivalents) was added dropwise over about 10 hours.
The reaction was continued under stirring for hours. After the reaction, concentrated aqueous ammonia 794
ml (11.8 mol) was added to decompose unreacted dimethyl sulfate, and the mixture was left overnight. The reaction solution was neutralized with dilute hydrochloric acid to adjust the pH to about 6. The methylated β-CD was extracted with 8.7 l of chloroform. The chloroform layer was washed with water, dried over sodium sulfate and the chloroform was distilled off. After the residue was dissolved in 1.5 l of ethanol, the solvent was distilled off. Further, 2 l of water was added to make an aqueous solution, followed by filtration through a 5 μm Millipore filter and freeze-drying to obtain 261.4 g of methylated β-CD.

The specific rotation [α] ²⁵ _D of the obtained methylated β-CD is + 160.1 ° (c = 1.0, water), melting point 1
43.0 to 152.0 ° C, and the solubility was as shown in the figure.

As a result of analyzing the methylation rate by gas chromatography, the methylation rate of the hydroxyl group at each position in the unit glucose of the total glucose was as follows.

2nd place 61.4% 3rd place 49.3% 6th place 100% Average 70.2%

[0040]

According to the present invention, the solubility of water is several times higher than that of CD itself or its known methylated CD, and it is particularly characteristic that the known methylated CD has an increased temperature. As a result, a partially methylated CD having the property of decreasing its solubility while improving it is provided.

[Brief description of the drawings]

FIG. 1. Rf value by thin layer chromatography is 0.5
5 shows a gas chromatograph derived from the methylated β-CD composition of No. 5.

FIG. 2: Rf value of 0.5 by thin layer chromatography
5, a methylated-β-CD composition and a raw material β-CD, and a known methylated CD, heptakis- (2,6-di-
FIG. 4 shows the solubility of O-methyl) β-CD and heptakis- (2,3,6-tri-O-methyl) β-CD in water at various temperatures. In the figure, Δ: β-CD: heptakis- (2.6-di-O-methyl) β-CD ▲: heptakis- (2,3,6-tri-O-methyl) β-
CD ●: represents the partially methylated β-CD composition (i) of the present invention.

Continuation of the front page (72) Inventor Yoshiaki Yagi 5437-38, Fujisawa, Kanagawa Prefecture

Claims (1)

(57) [Claims] (A) A silica gel thin-layer chromatography (thin layer: Art 5744, manufactured by Merck; developing solvent system: chloroform-methanol (9: 1)) has an Rf value of 0.55; (B) The methylation rate calculated by the gas chromatography method after the pretreatment was 55.6% at the 2nd position, 45.7% at the 3rd position, and 100% at the 6th position for each hydroxyl group of the constituent glucose unit. A partially methylated-β-cyclodextrin.