JPH066562B2 - Amino acid derivative - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel amino acid derivative suitable for use in a liquid crystal material and a method for producing the same.

[Conventional technology]

Cholesteric liquid crystals are known as liquid crystal compounds. Cholesteric liquid crystals have various optical properties such as optical property based on helical structure, selective light scattering, and circular dichroism. Various applications have been developed utilizing this phenomenon, and they all utilize the color change due to voltage application, temperature change, and gas adsorption of cholesteric liquid crystals. Specific examples of application of the cholesteric liquid crystal include a liquid crystal thermometer, a pressure sensor, applied measurement of infrared light, and a detector for microwave measurement. Cholesteric liquid crystals are often found in cholesterol compounds, but they can also be obtained by dissolving a nematic liquid crystal with an optically active substance having optical activity or by introducing an asymmetric carbon atom into the molecular structure. These liquid crystals are called chiral nematic liquid crystals and are not essentially different from the cholesteric liquid crystals found in cholesterol compounds, but because they have excellent chemical and optical stability, they are being used in place of cholesterol compounds.

Examples of such chiral nematic liquid crystals include N-
(4-ethoxybenzylidene) -4- (2-methylbutyl) aniline, 4- (2-methylbutyl) benzoic acid-4'-n-hexyloxyphenyl ester and the like.

[Problems to be Solved by the Invention]

The substance used as a chiral nematic liquid crystal has excellent stability against the effects of moisture, air, light, heat, etc., and can retain a cholesteric phase in a wide temperature range where the display device is placed under natural conditions. is necessary.

Further, the compound conventionally used as a chiral nematic liquid crystal uses an optically active alcohol, specifically, 2-methylbutanol, 3-methylpentanol, etc., as a raw material for an optically active site. However, these alcohols are expensive and have a problem in terms of production cost.

Therefore, there is an example of a liquid crystal using an amino acid as a cheaper and more easily available optically active source (Japanese Patent Laid-Open No. 62-8964).
8). However, the substance is a smectic liquid crystal,
Moreover, it is only reported that it shows a smectic A phase at high temperature, and it cannot be put to practical use.

The present invention provides a novel compound showing a cholesteric phase in a wide temperature range at a temperature close to room temperature in a chiral nematic liquid crystal using an inexpensive and easily available amino acid as a raw material for an optically active site, and a method for producing the same. To aim.

[Means for Solving the Problems]

The compounds provided by the present invention have the general formula (1) [Wherein R represents a linear alkyl group having 6 to 14 carbon atoms,
X represents a linear alkyl group having 1 to 14 carbon atoms, and Y represents CH.
₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Of C, CH ₃ or H, and C ^* represents an asymmetric carbon atom.] Is a novel optically active amino acid derivative.

The structure of the amino acid derivative of the present invention has an amino acid moiety as an optically active source. And cinnamic acid derivative part as core part , And these two are linked by a peptide bond.

First, the amino acid part is hydrogen, Y, -COO on the asymmetric carbon C ^*
X is attached and the amine moiety forms a peptide bond. X represents a linear alkyl group having 1 to 14 carbon atoms, particularly preferably 1 to 3 carbon atoms. When the carbon number is 15 or more, it is difficult to obtain the raw material and the synthesis is difficult.

Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the above. The amino acid used as a raw material for forming the amino acid moiety may be any optically active amino acid, and specific examples thereof include L-alanine, leucine, valine, isoleucine, and phenylalanine. However, methionine is excluded. Optically active amino acids are D-form, L-form
It may be on or off your body.

Next, the cinnamic acid derivative part is cinnamic acid At the α-position carbon of the unsaturated hydrocarbon group of
And the carboxylic acid forms a peptide bond with the amine in the amino acid portion. Z represents one of CH, CH ₃ and H. The benzene ring of cinnamic acid is bound to the para position of the benzene ring via an ester bond, and the para position of the benzene ring is bound to R via an ether bond. R represents a linear alkyl group having 6 to 14 carbon atoms, particularly preferably 7 to 12 carbon atoms. When the carbon number is less than 6, the temperature range in which the liquid crystal phase is exhibited becomes narrow. When the carbon number is 16 or more, similarly, the temperature range in which the liquid crystal phase is exhibited becomes narrow, and the liquid crystal phase becomes unstable.

As described above, the present invention uses an amino acid as an optically active source of a chiral nematic liquid crystal and uses G
It is characterized by the introduction of a cinnamic acid derivative (US4613209, see JP-A-52-89643) which has been studied by Oodby et al. and is generally known as a liquid crystal raw material.

That is, when an amino acid was used as an optically active source, the resulting peptide bond had a strong intermolecular force and it was difficult to express liquid crystallinity, but by introducing a cinnamic acid derivative, at a temperature close to room temperature, It became possible to show a cholesteric phase in a wide temperature range. The present invention is the first chiral nematic liquid crystal using an amino acid.

The compound according to the present invention can be produced according to the following production method.

General formula [Wherein Z represents one of CN, CH ₃ or H] and a compound represented by the general formula [Wherein X represents a linear alkyl group having 1 to 14 carbon atoms,
Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or In which C ^* represents an asymmetric carbon atom] is reacted with a reaction derivative of the compound represented by the general formula [Wherein X represents a linear alkyl group having 1 to 14 carbon atoms,
Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the following, Z is CN, CH ₃ , or 1 of H
Represents a species, and C ^* represents an asymmetric carbon atom]. [Wherein R represents a straight-chain alkyl group having 6 to 14 carbon atoms], and a compound represented by the formula: [Wherein R represents a linear alkyl group having 6 to 14 carbon atoms,
X represents a linear alkyl group having 1 to 14 carbon atoms, and Y represents CH.
₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the following, Z is CN, CH ₃ , or 1 of H
Represents a seed, and C ^* represents an asymmetric carbon atom].

The method for producing the compound according to the present invention can be considered in two stages. That is, first, the compound represented by the general formula (II) is reacted with the compound represented by the general formula (III) to reach the compound represented by the general formula (IV) (hereinafter referred to as reaction A), and It comprises two steps of a route (hereinafter referred to as reaction B) in which a compound represented by the formula (V) is reacted with a compound represented by the general formula (V) to obtain a compound represented by the general formula (I).

Reaction A General formula [In the formula, Z represents one of CN, CH _{3 and} H. ] When Z is CN or H, commercially available compounds can be used. When Z is CH ₃ , it is synthesized by a conventionally known method shown below. That is, it can be obtained by reacting 4-hydroxybenzaldehyde and propionic anhydride with potassium propionate.

General formula [Wherein X represents a linear alkyl group having 1 to 14 carbon atoms,
Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Of the formula (C ^* represents an asymmetric carbon atom), and the reactive derivative of the compound of formula (III) refers to the hydrochloride of the compound of formula (III). As the production method, a commercially available one can be used when the carbon number of X is 2 or less, and a synthetic method can be used when X is 3 or more. As a synthetic method, for example, a necessary amino acid alkyl ester hydrochloride can be obtained by reacting a commercially available amino acid and an alcohol having a carbon chain of a desired length with thionyl chloride.

The reaction of the compound represented by the general formula (II) with the compound represented by the general formula (III) is appropriately carried out in a solvent (for example, dichloromethane, carbon tetrachloride, benzene, etc.) as a binder, N, N′-dicyclohexylcarbodiimide (hereinafter referred to as DCC). Omitted (hereinafter referred to as DCC method). By this reaction, the general formula The compound of

The conventional method is to use P- of the compound represented by the general formula (II).
After attaching a protecting group to the hydroxyl group of hydroxycinnamic acid, it was necessary to deprotect by esterification by the acid chloride method. However, in the conventional method, the double bond of cinnamic acid was also reduced at the deprotection stage, and the target compound could not be obtained. Then, esterification by the DCC method did not require a protecting group, and the target compound could be obtained by a one-step reaction at room temperature. In addition, the yield was as high as 80%.

The reaction formulas of the conventional method and the DCC method are shown below.

(1) Conventional method Hydroxyl protection Esterification / acid chloride method Deprotection (2) DCC method Reaction B Next, the reaction for obtaining the target amino acid derivative from the intermediate (IV) obtained by the reaction A will be described.

General formula A commercially available compound can be used as the compound represented by the formula [wherein R represents a linear alkyl group having 6 to 14 carbon atoms]. Reaction A
The reaction of the compound of the general formula (IV) and the compound of the general formula (V) obtained by the above is carried out by first heating the compound of the general formula (V) with thionyl chloride under reflux to effect acid chloride formation, By heating the compound (IV) and pyridine in a solvent (benzene, ether, etc.) and heating under reflux, the final product of the general formula [Wherein R represents a linear alkyl group having 6 to 14 carbon atoms,
X represents a linear alkyl group having 1 to 14 carbon atoms, and Y represents CH.
₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the following, Z is CN, CH ₃ , or 1 of H
Represents a species, and C ^* represents an asymmetric carbon atom].

The compound represented by the general formula (I) is an optically active amino acid derivative, but an optically inactive amino acid derivative of the same structural formula obtained when a racemic body is used as the starting amino acid is also used as a liquid crystal material. You can

[Action]

The compound of general (I) in the present invention is a novel amino acid derivative which is useful as a liquid crystal compound using a gay cinnamic acid derivative as a core part and an amino acid as an optically active source.

The peptide bond that occurs when an amino acid is introduced as an optically active group has a strong intermolecular force, which promotes an increase in melting point and is unsuitable as a liquid crystal compound, but the cinnamic acid derivative was used as the core part. It is considered that, due to the balance of carbon chains, the action of ester bond, etc., polarization was promoted and the liquid crystal alignment was facilitated. When a cyano group is introduced near the asymmetric carbon (Z in the general formula (I))
= CN) is considered to contribute similarly by inhibiting intermolecular hydrogen bonding.

The compound of the present invention is a novel amino acid derivative having applicability to a liquid crystal display device having excellent responsiveness and memory property for the above reasons.

Further, the compound of the present invention, by blending with the already known strong fusible liquid crystal, to widen the temperature range showing strong fusible property up and down,
Responsiveness can be improved, and it can be compounded with a liquid crystal which is not optically active so as to have a strong melting point.

〔Example〕

Hereinafter, the compounds of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Hereinafter, _{Cry, Ch, I SO, S} A, S C phase, respectively crystal, cholesteric phase, an isotropic phase, Sumesuchikku A phase, the Sumesuchikku C phase.

The compound of the present invention was purified by silica gel chromatography and recrystallization with alcohol and hexane. The measured values of the phase transition points shown below may be slightly affected by the purity of the substance.

In the following Examples, only optically active amino acids as raw materials are used, but only the D-amino acids having the same phase transition temperature are used. What can be obtained is also clear from theory.

Example 1 Synthesis of N- {4- (4'-n-heptyloxybenzoyloxy) -α-cyanocinnamoyl} -L-alanine ethyl ester (1-1) N- (4-hydroxy-α- Cyanocinnamoyl) -L
-Synthesis of alanine ethyl ester 1.04 g of commercially available α-cyano-4-hydroxycinnamic acid
(5.5 mmole) was stirred in 10 ml of cold dichloromethane and the reaction was brought to 0-5 ° C. DCC 1.134
g (5.5 mmole) was added. After 20 minutes, the commercial L-
Alanine ethyl ester hydrochloride 0.768 g (5 mmol
e), add 0.7 ml (5 mmole) of triethylamine,
The mixture was stirred at 0 ° C for 2 hours and at room temperature overnight. The solvent was distilled off, and the residue was dissolved in 30 ml of ethyl acetate, insoluble NN'-dicyclohexylurea was removed by filtration, and the filtrate was filtered with 10% citric acid (30 ml), water (30 ml), 4% sodium hydrogen carbonate (30 ml) and water. It was washed successively with (30 ml). The organic layer was dried over magnesium sulfate and evaporated to dryness to give the crude ester.

The yield was 79%. The crude product was used in the next reaction as it was.

(1-2) Synthesis of N- {4- (4'-n-heptyloxybenzoyloxy) -α-cyanocinnamoyl} -L-alanine ethyl ester heptyloxybenzoic acid 0.94 g, thionyl chloride 2.
89 ml and 1 drop of DMF are heated under reflux for about 2 hours to form an acid chloride. 1.15 g of the compound synthesized in (1-1) by removing thionyl chloride by distillation, 3.21 ml of pyridine, and 5 of benzene.
ml and 1 drop of DMF were added and the mixture was heated under reflux for about 5 hours to complete the esterification.

After the post-treatment, n-hexane: ethyl acetate = 5: 1 mixture was used as a melt and purified by silica gel column chromatography to obtain 1.8 g of a crude crystal compound. Further purification by recrystallization gave the target compound.

The structure of the obtained product was confirmed by infrared absorption spectrum, elemental analysis, 'H-NMR, and mass spectrum measurement as instructed below.

The infrared absorption spectrum data is shown in FIG. 2220
The presence of CN is recognized from the absorption at cm ^-1 .

Elemental analysis [%] 'H-NMR [ppm] 0.90, 1.32, 1.58, 1.85, 4.05,
4.28, 4.68, 6.87, 6.95, 7.32,
8.00, 8.12, 8.32 Mass spectrum [M / Z] 506: M ⁺ 461: (OC ₂ H ₅ ) ⁺ 433: (M-COOC ₂ H ₅ ) ⁺ 390: 291: 219: 171: 121: Examples 2 to 4 Compounds of Examples 2 to 4 in which R, X, Y and Z in the general formula (I) are groups shown in Table 1 were synthesized in the same manner as in Example 1.

Further, the fact that the obtained compound is a compound having a desired structure means that the infrared absorption spectrum and '
Confirmed by 1 H-NMR.

Table 1 also shows an example of the phase transition temperatures of Examples 1 to 4.

[Comparative Example] Hereinafter, an example of a liquid crystal containing an amino acid known to date in a skeleton will be taken up for comparison.

[Comparative Example 1] Cry-S _A 176.8, S _A -I _SO 179.1, S _A -S _C 154.7 [° C] [Comparative Example 2] General formula Wherein R, X, Y, and Z have the structures shown in Table 1.

Methionine was introduced as an optically active amino acid, but it showed no phase transition at a melting point of 83.6 ° C.

〔The invention's effect〕

As exemplified above, the compound of the present invention exhibits a cholesteric phase in a very wide temperature range at a temperature close to room temperature. Therefore, a novel compound useful as a material for a liquid crystal display device that applies an electro-optical effect in a practical temperature range alone or appropriately mixed with another nematic, smectic or ferroelectric liquid crystal can be easily and inexpensively prepared. Can be provided.

[Brief description of drawings]

FIG. 1 is an infrared absorption spectrum diagram of the compound shown in Example 1 of the present invention.

Claims (2)

[Claims] 1. A general formula [Wherein R represents a linear alkyl group having 6 to 14 carbon atoms,
X represents a linear alkyl group having 1 to 14 carbon atoms, and Y represents CH.
₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Of the above, Z represents one of CN, CH ₃ or H, and C ^* represents an asymmetric carbon atom]. 2. General formula [Wherein Z represents one of CN, CH ₃ or H] and a compound represented by the general formula [Wherein X represents a linear alkyl group having 1 to 14 carbon atoms,
Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or In which C ^* represents an asymmetric carbon atom] is reacted with a reaction derivative of the compound represented by the general formula [Wherein X represents a linear alkyl group having 1 to 14 carbon atoms,
Y is CH ₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the following, Z is CN, CH ₃ , or 1 of H
Represents a species, and C ^* represents an asymmetric carbon atom]. [Wherein R represents a straight-chain alkyl group having 6 to 14 carbon atoms]. [Wherein R represents a linear alkyl group having 6 to 14 carbon atoms,
X represents a linear alkyl group having 1 to 14 carbon atoms, and Y represents CH.
₃ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , or Represents one of the following, Z is CN, CH ₃ , or 1 of H
Represents a species, and C ^* represents an asymmetric carbon atom].