JP6004433B2 - Method for producing gel-forming compound and molecular assembly thereof - Google Patents

Description

  The present invention relates to a novel compound capable of changing the fluorescence wavelength by dispersing molecules depending on the type of solvent and forming a molecular assembly (sol / gel transition), and changing the dispersion state of the compound. This relates to a method for changing the fluorescence wavelength.

Organic low-molecular gelling agents that form organic aggregates by forming non-covalent bonds such as hydrogen bonds and van der Waals interactions to form molecular aggregates and take in the solvent to gel, are described above depending on the environment and specific stimuli. Non-covalent bonds can be reversibly cleaved / recombined, resulting in a sol / gel phase transition phenomenon. If the organization of the gelling agent is accompanied by the expression of the function, it is possible to reversibly turn on / off the function by controlling the organization of the gelling agent. Is expected to be used as a sensor that responds to the environment and stimuli.
As such a molecular system whose function is reversibly changed by organization, a “molecular system capable of reversibly changing fluorescence behavior (wavelength and intensity)” by organization is known in recent years. So far, stilbene derivatives (Non-Patent Document 1), carbazole derivatives (Non-Patent Document 2), phenanthroline derivatives (Non-Patent Document 3), triphenylbenzene derivatives (Non-Patent Document 4), etc., in organic solvents. It has been reported that the fluorescence intensity intensifies as compared to the case where the formed tissue is a molecule alone.
However, these molecular systems are applicable only in organic solvent systems and cannot be adapted to aqueous solvents. The reason is that the molecules used are insoluble in aqueous solvents. Considering from an industrial point of view in the application of functional materials, molecular systems that exhibit such functions in aqueous solutions that do not impact the environment are desirable, but until now, molecular dispersion (sol) / molecular assembly in aqueous solutions There are no reports of molecular systems in which fluorescence behavior changes due to transition of body formation (gel).

Toru Nakamura et al., Patent No. 4579111 (Registration date: 2010.9.3)

B-K.An, et al., J.Am.Chem.Soc., 2004, 126, 10232-10233. X. Yang, et al., Chem. Commun., 2008, 453-455. K. Sugiyasu, et al., Org. Biomol. Chem., 2003, 1, 895-899. C. Bao, et al., Chem. Eur. J., 2006, 12, 3287-3294. Y. Matsuzawa, et al., Adv. Funct. Mater., 2007, 17, 1507-1514. Y. Hayashi, et al., J. Photochem. Photobiol., A, 2002, 149, 199-206.

  In view of industrial operability, the present invention provides a hydrogel material whose fluorescence behavior changes due to the transition of molecular dispersion (sol) / molecular aggregate formation (gel) in an aqueous solution system, and a method for controlling the fluorescence behavior. The issue is to provide.

The present inventors are able to develop even in aqueous solvents based on the knowledge about the molecular assembly so far (Non-Patent Document 5 and Patent Document 1), and also control the site and organization that control the fluorescence behavior. A molecular system was established in which the sites were clearly distinguished and the fluorescence wavelength changed with organization.
Specifically, as shown in FIG. 1, the molecular assembly of the present invention is composed of molecules in which a site responsible for organization and a site related to fluorescence behavior are clearly separated in the molecule. The part related to the fluorescence behavior can be appropriately changed according to the purpose (for example, emission wavelength). The site responsible for organization is constituted by oligopeptides, which are organized by forming intermolecular hydrogen bonds. For organization, water, a hydrophilic organic solvent (such as dimethyl sulfoxide or dimethylformamide), or a mixture thereof is used.
The inventors of the present invention designed the molecule of Compound 1 shown in FIG. 2 by paying particular attention to the cyanobiphenyl group. The cyanobiphenyl group is known to emit long wavelength-shifted fluorescence by forming an aggregate (Non-patent Document 6), but the cyanobiphenyl group itself does not have the property of spontaneously forming an aggregate. . The inventors of the present invention have previously found (Non-patent Documents 5 and 1), and the unit (oligopeptide group) to be organized is bonded to a cyanobiphenyl group to form an aggregate. Urged.

［上記一般式中、Ｒ¹は炭素数４以下のアルキル基、Ｒ²は水素原子又は炭素数４以下のアルキル基、ｍは０又は１〜１０の自然数、ｎは２〜１０の自然数、＊はその炭素がＲもしくはＳ体(該炭素がアミノ酸残基に属する場合にはＬもしくはＤ体)に対応する光学活性エナンチオマーを示す］
〈２〉〈１〉に記載のゲル生成化合物又はその塩から選ばれた少なくとも１種の化合物又はその塩を有効成分とする、ゾル−ゲル相互間の相転移性機能材。
〈３〉〈１〉に記載のゲル生成化合物分子から形成され、それぞれの分子の組織化をつかさどる部位であるペプチド基同士が相互に並列し、それにより、それぞれの分子の蛍光挙動にかかる部位であるシアノビフェニル基同士も相互に並列した構造を備える分子集合体。
〈４〉数十nmの繊維状組織体であることを特徴とする、〈３〉に記載の分子集合体。
〈５〉〈１〉に記載のゲル生成化合物又はその塩を親水性溶媒中に分散させて、可視光域で蛍光を発生するゾル分散液を作成し、当該分散液に水を加えることにより、可視光域で、より長波長側にシフトした蛍光を発生する当該化合物の分子集合体ゲルを形成させることを特徴とする、〈３〉に記載のゲル生成化合物の分子集合体の製造方法。
〈６〉親水性溶媒が、ジメチルスルホキシド、ジメチルホルムアミド、ジメチルアセトアミド、１,４-ジオキサン、テトラヒドロフラン、メタノールおよびエタノールのいずれかであることを特徴とする、〈５〉に記載の分子集合体の製造方法。 That is, according to this application, the following invention is provided.
<1> A gel-forming compound represented by the following general formula, or a salt thereof, formed by chemically bonding an organized unit consisting of a cyanobiphenyl group and a peptide group.

[In the above general formula, R ¹ is an alkyl group having 4 or less carbon atoms, R ² is a hydrogen atom or an alkyl group having 4 or less carbon atoms, m is a natural number of 0 or 1 to 10, n is a natural number of 2 to 10, * Is an optically active enantiomer whose carbon corresponds to R or S form (or L or D form when the carbon belongs to an amino acid residue)]
<2> A sol-gel phase-transition functional material containing at least one compound selected from the gel-forming compound or salt thereof according to <1> or a salt thereof as an active ingredient.
<3> Peptide groups, which are formed from the gel-forming compound molecules described in <1> and are responsible for the organization of each molecule, are arranged in parallel with each other. A molecular assembly with a structure in which some cyanobiphenyl groups are parallel to each other.
<4> The molecular assembly according to <3>, which is a fibrous organization of several tens of nm.
<5> Dispersing the gel-forming compound or salt thereof according to <1> in a hydrophilic solvent, creating a sol dispersion that generates fluorescence in the visible light region, and adding water to the dispersion, The method for producing a molecular aggregate of a gel-forming compound according to <3>, wherein a molecular aggregate gel of the compound that generates fluorescence shifted to a longer wavelength side in the visible light region is formed.
<6> Production of molecular assembly according to <5>, wherein the hydrophilic solvent is any one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, 1,4-dioxane, tetrahydrofuran, methanol and ethanol Method.

The compound of the present invention changes the dispersion state of molecules in a solvent from a sol state in which molecules are dispersed in a solvent to a gel state in which molecular aggregates are formed by changing the type of solvent in an aqueous solvent. In addition, as the dispersion state changes, the wavelength of fluorescence emitted by the molecule can be shifted to the longer wavelength side.
According to the present invention, the dispersion state of molecules in an aqueous solvent, that is, the behavior of dispersion (sol) and molecular aggregate formation (gel), which has been captured only by macroscopic phenomena such as changes in viscosity until now, has been visually observed. Therefore, local disruption and formation of organization can be observed. (Image: Fig. 1)
The gel-like molecular assembly of the present invention reversibly changes to a sol-like dispersion upon application of external stimulus, for example, heat, and the fluorescence wavelength is also shifted to the short wavelength side. Utilizing this property, the compound of the present invention can be used as a dispersion in an aqueous solvent, for example, for a heat sensor.

An image of a molecular system in which fluorescence emission changes due to organization. Synthesis scheme of Compound 1. A photograph showing the gelation of Compound 1 (Compound 1 (1 mg) is gelled with 200 μl of dimethyl sulfoxide and 800 μl of water). Infrared absorption spectrum of stretching vibration region of amide in gel (a) and sol (b) of Compound 1. The SEM photograph figure of the molecular aggregate (xerogel) of compound 1. Fluorescence spectrum of Compound 1 (dimethyl sulfoxide solution of Compound 1 (solid line), dimethyl sulfoxide of Compound 1 200 μl / 800 μl of water gel (dotted line), excitation wavelength 320 nm). Photograph showing the state of fluorescence emission of Compound 1 (Right: Gel of 200 μl of dimethyl sulfoxide of Compound 1/800 μl of water, Left: Solution of dimethyl sulfoxide of Compound 1. Excitation wavelength: 320 nm).

(1) Synthesis of Compound 1 Compound 1 was synthesized according to the scheme shown in FIG.
4-Cyano-4'-hydroxybiphenyl (5.06 g), K ₂ CO ₃ (7.25 g), ethyl bromoacetate (4.17 g) are dissolved in dehydrated dimethylformamide (5 mL) (using a three-necked flask) Heat to 120 ° C. with stirring. After heating at 120 ° C. for 3 hours, the dimethylformamide solution was poured into ion-exchanged water (100 mL) and stirred for about 30 minutes. The precipitated white precipitate was separated by suction filtration. The collected white solid was again added to ion-exchanged water (100 mL) for the purpose of purification, stirred, and filtered by suction filtration. The obtained white solid was dissolved in chloroform (150 mL), transferred to a separatory funnel, and washed twice with ultrapure water (200 mL). Thereafter, an appropriate amount of anhydrous sodium sulfate was added to the chloroform solution and stirred to remove residual water. Subsequently, chloroform was removed under reduced pressure, and hexane (100 mL) was added to the resulting oily residue and stirred. A white solid produced in the hexane solution was collected by suction filtration. 4 g of intermediate 1 was obtained.
Acetic acid (80 mL) and a small amount of tosylic acid were added to Intermediate 1 (4.00 g) and heated at 130 ° C. for 12 hours. Thereafter, after standing at room temperature, ultrapure water was added little by little to form a white precipitate. The white precipitate (3.29 g) collected by suction filtration was purified by dispersing in hexane (50 mL) and dichloromethane (2.5 mL) and stirring. The collected white solid was dried under reduced pressure to obtain 2.6 g of Intermediate 2.
t-Butyloxycarbonyl- (L-valine) ₃ -benzyl ester (1.7 g) was dissolved in ethyl acetate (50 mL), 4N-hydrogen chloride / ethyl acetate (60 mL) was added, and the mixture was stirred for 4 hours. The solvent was completely distilled off under reduced pressure, diethyl ether was added to the resulting white precipitate and washed well to obtain a white solid intermediate 3 (1.2 g).
Intermediate 2 (0.3 g) and 1-hydroxybenzotriazole (HOBt) are dissolved in dry DMF (10 mL) and stirred at -5 ° C. while stirring with 1-ethyl 3- (3-dimethylaminopropyl) carbodiimide hydrochloride (WSC). ) Containing dichloromethane solution was added. After 1 hour, a dichloromethane solution containing intermediate 3 (0.57 g) and triethylamine were added, and the mixture was stirred overnight while gradually returning to room temperature.
The reaction solution was washed twice with 10% aqueous citric acid solution, water, 4% aqueous sodium hydrogen carbonate solution and water, and the organic layer was dried over anhydrous sodium sulfate. The solvent was completely distilled off under reduced pressure to obtain a crude product. It was isolated and purified by silica gel column chromatography (developing solvent chloroform) to obtain Intermediate 4 (0.46 g).
Intermediate 4 (1.5 g) was dissolved in DMF (100 mL), 0.24 g of 5% palladium / carbon was added as a catalyst, and catalytic hydrogen reduction was performed. After 6 hours, filtration was performed using Celite as a catalyst, and then the solvent was distilled off under reduced pressure to obtain a white solid. The obtained white solid was purified by silica gel column chromatography (developing solvent chloroform: ethanol = 4: 1), and then the obtained solid was stirred in ether to isolate and purify Compound 1 (1.0 g).
White powder.
1H NMR (DMSO-d6) d: 0.70-1.05 (m, 18H, CH (CH3) 2), 1.90-2.09 (m, 3H, CH (CH3) 2), 4.00-4.10 (m, 1H, N-CH -CO), 4.20-4.29 (m, 1H, N-CH-CO), 4.31-4.35 (m, 1H, N-CH-CO), 4.59-4.70 (m, 2H, O-CH2-CO), 7.05 (d, 2H, Ar-H), 7.72-7.99 (m, 6H, Ar-H).
Anal. Calcd for C30H38N4O6: C, 65.44; H, 6.96; N, 10.17%.
Found: C, 65.75; H, 7.04; N, 9.91%.

(2) Preparation of molecular assembly A molecular assembly can be prepared by forming a hydrogen bond at a site that controls the organization of compound 1 (see FIG. 1). That is, it is created using solvent conditions that facilitate hydrogen bonding.
1 mg of the compound 1 obtained in (1) was weighed, heated and dissolved in 200 μl of dimethyl sulfoxide, and further 800 μl of water was added. In particular, a good molecular assembly was formed without the need for heating, and this molecular assembly incorporated a solvent to form a gel (FIG. 3).
Similar experiments were performed using various solvents and mixed solvents. The results are shown in Table 1.

以上の結果から、このようにして化合物１のゲルを形成させることができる溶媒としては、ジメチルスルホキシド/水の他に、ジメチルホルムアミド/水、ジメチルアセトアミド/水、１,４-ジオキサン/水、テトラヒドロフラン/水、メタノール/水、エタノール/水を挙げることができる。

From the above results, the solvent capable of forming the gel of Compound 1 in this way is not only dimethyl sulfoxide / water but also dimethylformamide / water, dimethylacetamide / water, 1,4-dioxane / water, tetrahydrofuran / Water, methanol / water, ethanol / water.

(3) Analysis of molecular assembly
The formation of molecular aggregates in the gel obtained in (2) was identified by measuring infrared absorption spectra. The compound 1 obtained in (1) was dissolved in 1 mg, 200 μl of dimethylsulfoxide-d6, and further gelled with 800 μl of heavy water. The infrared absorption spectrum of this gelled product is shown in FIG. Moreover, the compound 1 obtained in (1) was dissolved in 1 mg and 1 ml of dimethyl sulfoxide-d6, and the result of measuring the infrared absorption spectrum of the obtained sol solution is shown in FIG. In the gel, the peak of the amide region was shifted to the lower wavenumber side, which suggested that complementary hydrogen bonds were formed between the oligopeptides of Compound 1. Furthermore, when FE-SEM observation of the xerogel produced from the gelled product was performed, it was found that a fibrous structure having a width of several tens of nanometers was formed. (Figure 5).

(4) Fluorescence behavior of molecular dispersion and molecular assembly of Compound 1
The fluorescence spectrum of the compound 1 obtained in (1) (sol, dimethyl sulfoxide solution) and molecular assembly (gel, dimethyl sulfoxide / water = 1/9 mixed solution system) were measured (excitation wavelength was 320nm). It turned out that the fluorescence shifts to the visible region more and the visibility of the compound 1 increases by gelling. The measurement result of the fluorescence spectrum is shown in FIG. FIG. 7 shows a state in which the molecular dispersion and molecular assembly of Compound 1 emit fluorescence.

  The present invention is applicable to technical fields such as optical materials, viscous materials, microcapsules, sensors, medical technologies, electrical products, and measuring instruments.

Claims (6)

A gel-forming compound represented by the following general formula, or a salt thereof, formed by chemically bonding an organized unit consisting of a cyanobiphenyl group and a peptide group.

[In the above general formula, R ¹ is an alkyl group having 4 or less carbon atoms, R ² is a hydrogen atom or an alkyl group having 4 or less carbon atoms, m is a natural number of 0 or 1 to 10, n is a natural number of 2 to 10, * Is an optically active enantiomer whose carbon corresponds to R or S form (or L or D form when the carbon belongs to an amino acid residue)] A phase-transition functional material between sol-gel, comprising at least one compound selected from the gel-forming compound or salt thereof according to claim 1 or a salt thereof as an active ingredient. Peptide groups which are formed from the gel-forming compound molecules according to claim 1 and which are sites responsible for the organization of each molecule are arranged in parallel with each other, whereby cyanobiphenyl which is a site related to the fluorescence behavior of each molecule A molecular assembly with structures in which groups are parallel to each other. The molecular assembly according to claim 3, wherein the molecular assembly is a fibrous organization of several tens of nm. The gel-forming compound according to claim 1 or a salt thereof is dispersed in a hydrophilic solvent to prepare a sol dispersion that emits fluorescence in the visible light region, and water is added to the dispersion to obtain a visible light region. The method for producing a molecular aggregate of a gel-forming compound according to claim 3, wherein a molecular aggregate gel of the compound that generates fluorescence shifted to a longer wavelength side is formed. 6. The method for producing a molecular assembly according to claim 5, wherein the hydrophilic solvent is any one of dimethyl sulfoxide, dimethylformamide, dimethylacetamide, 1,4-dioxane, tetrahydrofuran, methanol and ethanol.

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