JPS60130544A - Preparation of optically active 2,3-dichloroisobutyric acid - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an intermediate for plant growth regulator in high yield and in high asymmetric yield, by including methacrylic acid in cyclodextrin, bringing it into contact with a chlorine gas while it is in a solid state. CONSTITUTION:Methacrylic acid is added to a saturated aqueous solution of cyclodextrin, the solution is stirred for 30min-10hr, preferably for 1-4hr, and an inclusion compound is prepared as precipitate. The prepared inclusion compound is sufficiently dried under reduced pressure, light rays are shielded, a dried chlorine gas is introduced to the inclusion compound in a powder state, the reaction is carried out at room temperature for 1-50hr, preferably for 10-20hr, so that optically active 2,3-dichloroisobutyric acid is prepared from the inclusion compound.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing optically active 2,3-dichloroisobutyric acid.

2.3-Dichloroisobutyric acid has been used as a plant growth and control agent component (Get, Earth 1
45°247, 3 Dec, 1980) It is also useful as an intermediate in the synthesis of L,α-methyl-1-serine. In particular, as the latter intermediate, a synthesis method that selectively obtains D-unit and L-unit, ie, the synthesis of optically active 2,3-dichloroisobutyric acid, has been desired.

The addition of chlorine to unsaturated compounds with carbon-carbon double bonds is usually carried out by a gas-liquid reaction (Chemical Society of Japan, Experimental Chemistry Course 20. p190), and ethylene chloride is obtained from ethylene. However, optically active chlorine compounds cannot be obtained by such reactions.

Furthermore, it has already been proposed to synthesize optically active halides from compounds with carbon-carbon double bonds (K-Penzient G-M, Schmidt
;Angew, Chem, Int, E4. En
GL, 8608 (1969)), this method requires an optically active starting material and cannot obtain the desired product unless a large single crystal is used. It has the disadvantage that it cannot be applied at all to unsaturated compounds or unsaturated compounds that do not exhibit optical activity.

The present inventors have conducted various studies in order to obtain optically active 2,3-dichloroisobutyric acid in a high asymmetric yield.
The present invention has been accomplished.

That is, in the present invention, the optically active 2,3- The object of the present invention is to provide a method for obtaining dichloroisobutyric acid with a high yield and a highly irregular yield.

The cyclodextrin used in the present invention is a cyclic dextrin obtained by treating starch or dextrin with special microorganisms or enzymes.
It has a cavity of 10X. Cyclodextrins have different numbers of d-glucose constituent units,
Three types of cyclodextrin, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin, are currently isolated, and among these, α-cyclodextrin and β-cyclodextrin can be used in the present invention.

A solution method is suitable for inclusion. In other words, methacrylic acid is added to a saturated aqueous solution of cyclodextrin, stirred for 30 minutes to 10 hours, preferably 1 to 4 hours,
The clathrate is obtained as a precipitate.

The clathrate compound was vacuum-dried, and the odor characteristic of methacrylic acid had disappeared from the resulting powder, but when the powder was dissolved in dimethyl sulfoxide-d6 and H nuclear magnetic resonance was measured, a signal derived from methacrylic acid was detected. It is clear that crotonic acid is included in the powder because it is observed and when the powder is treated with diethyl ether, the odor of methacrylic acid is again emitted.

After thoroughly drying the methacrylic acid clathrate compound thus obtained under reduced pressure, the light is cut off and chlorine gas is blown into the powdered state at room temperature for 1 to 50 hours, preferably 10 hours.
Allow to react for ~20 hours. In this case, what is particularly necessary is to sufficiently dry the clathrate compound and to use dry chlorine gas. If either or both of them are concentrated, a double reaction will occur and not only the chemical yield but also the optical yield will decrease.

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

Example 1 100 g of d-cyclodextrin was added to purified water Bo.

Add 10 g of methacrylic acid to the resulting solution and heat at 40'C for about 2 hours while stirring.
After stirring while heating, the mixture is allowed to cool and the resulting precipitate is filtered to obtain the clathrate compound. The obtained clathrate compound was heated at 20°C for 24 hours.
Vacuum dried for hours. Place this clathrate compound in a sealed container,
After exposure to chlorine gas for 20 hours at room temperature without light, unreacted chlorine gas was removed under vacuum. The reacted chloride was extracted with diethyl ether to obtain 2,3-dichloroisobutyric acid. Yield 17.496, concentration in methanol 0
．． 29 (g/100g). [:α125 is -15,0te, sentence 111a (C, D.

Glassick, W., E., Adcock; I
nd, Eng, Chem, Prod, Res.

Dev, (1964), 3.14], the optical yield was almost 100%.

Calculated elemental analysis value C = 30.5996 H = 3.8296 C no = Pa 1Q4ir analysis value C = 30.7496 H = 3.7896 (ffl = 45.1596 The values of the NMR spectrum measured in CDJ are as follows. That's right.

δ = 1.90 (3H, singlet), 3.77 (
IH, doublet), 4.13 (1H, doublet)
, 9.37 (COOHIH, singlet) Example 2 150 g of β-cyclodextrin was added to 150 ml of purified water.
Heat to about 70°C while stirring. Add 15g of methacrylic acid to the resulting solution and heat at 40° for about 1 hour and 30 minutes.
After stirring while heating to C, the mixture was allowed to cool. The resulting precipitate was filtered to obtain the clathrate compound. The clathrate was vacuum dried at 20"C for 30 hours, then placed in a sealed container and exposed to chlorine gas at air temperature for 20 hours without exposure to light. Unreacted chlorine gas was then removed under vacuum. The chlorinated product was extracted with ethyl ether to obtain 2.3-dichloroisobutyric acid.

Yield: 5396, concentration in methanol: 1.20 (g/
[α]; 5 measured with 100d) was +13.2, and compared with the literature value (same as Example 1), the optical yield was approximately 8.
It was 896.

Elemental analysis value calculation value C= 30. '59% H=3.82% C7=45.19% Analysis value C=30.50% H:=:3.89% C4=45.29% The NMR spectrum in CDJ is the same as in Example 1. Ta.

Patent applicant: Director of the Agency of Industrial Science and Technology River 1) Yube

Claims (1)

[Claims] (1) Optically active compound 2 characterized in that methacrylic acid is included in cyclodextrin and then brought into contact with chlorine.
, 3-dichloroisobutyric acid manufacturing method.