JP2024072565A - Compound - Google Patents

Abstract

To provide a dye compound which has a photodegradable group to be detached by irradiation with light in a specific wavelength region and has an N-hydroxysuccinimide ester group that is a site binding to a biological substance.SOLUTION: The compound is represented by Formula (1). [In the formula, Ar1 is a C3-20 (hetero)aryl group; Ar2 is H or a C3-20 (hetero)aryl group; Y1 is a phenyloxy group substituted with an aminomethyl group at the 4-position; Z1 is a direct bond or a divalent aromatic linking group; and R1 is a group linking Z1 and the N-hydroxysuccinimide ester group through three or more single bonds.]SELECTED DRAWING: None

Description

The present invention relates to a novel near-infrared light absorbing dye compound that can be easily introduced into biological materials such as nucleic acids, proteins, and polysaccharides.

Dyes that absorb or emit near-infrared light have attracted great interest for applications in novel sensors and in vitro and in vivo imaging. For example, near-infrared fluorescence can be used as a non-destructive method to track or analyze many different molecules that are labeled with fluorescent dyes and whose fluorescence can be detected. Labeling of biological materials such as nucleic acids, proteins, and polysaccharides with dyes is typically achieved by introducing an N-hydroxysuccinimide ester group or the like into the dye molecule and using it as a binding site for the biological material.

Among light in the near-infrared region, examples of dyes that absorb and emit light in the wavelength region of 650 to 1000 nm (near-infrared region), which is called the biological window and is not easily absorbed by substances and water in living bodies, include cyanine dyes (for example, Patent Document 1).
Among the cyanine dyes, indocyanine green (ICG) has been approved for clinical use, but has drawbacks such as low photostability and a long synthetic route.

On the other hand, dye compounds that express functions such as molecular activity by removing photocleavable groups upon irradiation with light, such as caged compounds whose activity is temporarily suppressed by photocleavable protecting groups, can express their functions in any time and space, and are therefore highly useful in elucidating complex biological phenomena that have time and space as their observation axes, and there is also interest in their application in fields such as drug delivery. One example of such a photoactive compound is a compound in which an aryloxy group is substituted for the boron atom of a skeleton (BODIPY) consisting of dipyrromethene and a boron atom. It is known that in this compound, a substitution reaction between the proton solvent molecule and the aryloxy group occurs upon irradiation with visible light of 500 nm, which is the absorption range of the BODIPY skeleton, and the aryloxy group is detached from the BODIPY skeleton (Non-Patent Document 1).

International Publication No. 2007/005222

J. Mater. Chem. B, 2015, 3, 7427-7433

However, in the above-mentioned prior art, there is no absorption in the near-infrared region, so molecular activity does not occur due to the elimination of photodegradable groups when irradiated with light in the wavelength range known as the biological window. In addition, since there is no binding site for biological substances such as antibodies, the compound is not necessarily effective when used in vitro or in vivo, and there was a demand for the development of new dyes.

The present invention provides a dye compound that has a photodegradable group that is eliminated by irradiation with light in a wavelength range known as the biological window, and also has an N-hydroxysuccinimide ester group that serves as a binding site for biological substances.

As a result of intensive research in light of the above problems, the present inventors discovered that a dye compound in which an N-hydroxysuccinimide ester group is connected via a spacer to a skeleton having a structure consisting of an azadipyrromethene and a boron atom (azaBODIPY skeleton), and an aryloxy group having a substituent is bonded to the boron atom, can be easily introduced into biological materials, has an absorption wavelength of 650 nm or more, which corresponds to the wavelength range known as the biological window, and the aryloxy group having a substituent is eliminated by irradiation with light in that absorption wavelength range, thereby completing the present invention.

In other words, the gist of the present invention is as follows:

[1] A compound represented by the following formula (1):

In formula (1), Ar ¹ represents a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
^Ar2 represents a hydrogen atom or a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
However, Ar ¹ or Ar ² may be bonded to Z ¹ , or a substituent possessed by Ar ¹ or Ar ² may be bonded to Z ¹ .
The substituents which Ar ¹ and Ar ² may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, an alkylamide group having 2 to 20 carbon atoms, a (hetero)aryl group having 3 to 20 carbon atoms, and a polyalkyl ether group having 4 to 16 carbon atoms, or a combination thereof.
^Y1 represents the following formula (2).

In formula (2), * represents a bond to a boron atom.
^R2 and ^R3 each independently represent a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms.
The substituents which ^R2 and ^R3 may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
However, R ² and R ³ cannot be hydrogen atoms at the same time.
^Z1 represents a direct bond or a divalent aromatic linking group.
^R1 represents a group connecting ^Z1 and the N-hydroxysuccinimide ester group via three or more single bonds.

[2] The compound according to [1], wherein the compound represented by formula (1) is a compound represented by the following formula (3):

[ ^{In formula (3), Ar 1 , Ar 2 , Y 1 , Z 1 and R 1 have the same meanings as those} in formula (1).]

[3] The compound according to [2], wherein in the compound represented by formula (3), Y ¹ is a compound represented by the following formula (4):

In formula (4), * represents a bond to a boron atom.
^R4 is any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
n represents an integer of 1 or more and 5 or less.

The present invention provides a dye compound that has a photodegradable group that is eliminated by irradiation with light in a wavelength range known as the biological window, and also has an N-hydroxysuccinimide ester group that serves as a binding site for biological substances.

1 is an absorption spectrum measurement chart of Compound 1.

The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be modified in various ways within the scope of the invention.
In this specification, the terms "(hetero)aryloxy group" and "(hetero)aryl group" respectively refer to an aryloxy group which may contain a heteroatom and an aryl group which may contain a heteroatom. The term "may contain a heteroatom" means that one or more of the carbon atoms forming the main skeleton of the aryl group or aryloxy group are substituted with a heteroatom, and examples of the heteroatom include a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and a silicon atom. Among these, a nitrogen atom is preferred from the viewpoint of durability.

The compound of the present invention is a compound represented by the following formula (1) (hereinafter, may be referred to as "dye of formula (1)").

In formula (1), Ar ¹ represents a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
^Ar2 represents a hydrogen atom or a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
However, Ar ¹ or Ar ² may be bonded to Z ¹ , or a substituent possessed by Ar ¹ or Ar ² may be bonded to Z ¹ .
The substituents which Ar ¹ and Ar ² may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, an alkylamide group having 2 to 20 carbon atoms, a (hetero)aryl group having 3 to 20 carbon atoms, and a polyalkyl ether group having 4 to 16 carbon atoms, or a combination thereof.
^Y1 represents the following formula (2).

In formula (2), * represents a bond to a boron atom.
^R2 and ^R3 each independently represent a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms.
The substituents which ^R2 and ^R3 may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
However, R ² and R ³ cannot be hydrogen atoms at the same time.
^Z1 represents a direct bond or a divalent aromatic linking group.
^R1 represents a group connecting ^Z1 and the N-hydroxysuccinimide ester group via three or more single bonds.

The dye of formula (1) has a structure (azaBODIPY skeleton) consisting of azadipyrromethene and boron atoms, and therefore exhibits absorption in the longer wavelength region than visible light from red to near-infrared, and further has the characteristic that the aryloxy group moiety having the substituent represented by formula (2) is eliminated by irradiation with light of the corresponding wavelength. In addition, the dye of formula (1) has one N-hydroxysuccinimide ester group at a position away from the π-conjugated structure of the dye skeleton, so that one dye molecule can be easily introduced to a primary amine in a biological material while maintaining the excellent optical properties described above.

One of the characteristics of the dye of formula (1) is that an aryloxy group moiety having a substituent represented by formula (2) is bonded to the boron atom of the azaBODIPY skeleton. By irradiating with light corresponding to the absorption wavelength, the aryloxy group moiety is removed from the azaBODIPY skeleton moiety. This is presumably because light irradiation causes photoinduced electron transfer from the aryloxy group moiety to the excited azaBODIPY skeleton moiety, resulting in a charge separation state, which is then subjected to solvolysis, causing the cleavage of the boron-oxygen bond. By utilizing this phenomenon, for example, by binding the compound of the present invention, which is the dye of formula (1) having an aryloxy group substituted with a water-soluble group, to an antibody, it is possible to efficiently deliver the dye of formula (1) to cancer cells in a living body, and further, by irradiating with light corresponding to the absorption wavelength, the aryloxy group moiety substituted with the water-soluble group is detached. As a result, the water solubility of the dye is significantly reduced, causing it to aggregate in the cell membrane of the cancer cell, which is believed to be able to physically destroy the cell membrane (this is called photoimmunotherapy, and is applicable to cancer treatment).

<Ar ¹ >
Ar ¹ represents a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
From the viewpoint of absorption wavelength, Ar ¹ is preferably a phenyl group which may have a substituent.

The substituents that Ar ¹ may have are any of an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, an alkylamide group having 2 to 20 carbon atoms, a (hetero)aryl group having 3 to 20 carbon atoms, and a polyalkyl ether group having 4 to 16 carbon atoms, or a combination thereof. Among these substituents, from the viewpoint of solubility, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, a polyalkyl ether group having 4 to 10 carbon atoms, or a combination thereof is preferable.

Ar ¹ may be bonded to Z ¹ , or a substituent carried by Ar ¹ may be bonded to Z ¹ .
In the formula (1), the two Ar ¹ s may be the same or different.

<Substituents of Ar ¹ and Ar ² >
Specific examples of the substituent that may be substituted by Ar ¹ and Ar ² described below are as follows.

Specific examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, n-hexyl, 1-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, n-heptyl, 1-methylhexyl, n-octyl, and tert-octyl.

Specific examples of alkoxy groups include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, heptyloxy, and octyloxy groups.

Specific examples of (hetero)aryloxy groups include phenyloxy groups, naphthyloxy groups, biphenyloxy groups, terphenyloxy groups, and pyridyloxy groups.

The polyalkyl ether group can be a group represented by the following formula (5):

[In formula (5), U represents a hydrogen atom, a methyl group, or an ethyl group, and m represents an integer of 2 to 7. * represents the bonding position with Ar ¹ or Ar ^2. ]

From the viewpoint of solubility, it is preferable that U is a methyl group and n is 4 or more.

^<Ar2>
Ar2 represents a hydrogen atom or a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.

From the viewpoint of absorption wavelength, ^Ar2 is preferably a phenyl group which may have a substituent.

The substituent that Ar ² may have is the same as the substituent that Ar ¹ may have. From the viewpoint of solubility, the substituent that Ar ² may have is preferably an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, a polyalkyl ether group having 4 to 10 carbon atoms, or a combination thereof.

^Ar2 may be bonded to ^Z1 , or a substituent possessed by ^Ar2 may be bonded to ^Z1 .
In the formula (1), the two Ar ² s may be the same or different.

<Y ¹ >
^Y1 represents the following formula (2).

In formula (2), * represents a bond with a boron atom.

<R ² , R ³ >
^R2 and ^R3 each independently represent a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms, provided that ^R2 and ^R3 are not simultaneously hydrogen atoms.
From the viewpoint of the ability to be eliminated by irradiation with light, R ² and R ³ are preferably each independently an arylcarbonyl group having 7 to 20 carbon atoms which may have a substituent.

The substituents which ^R2 and ^R3 may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof. Among these, from the viewpoint of solubility in water, any one of a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof, is preferred.

<Substituents of ^R2 and ^R3 >
Preferred examples of the substituents that ^R2 and ^R3 may have are as follows.

The polyalkyl ether group can be a group represented by the following formula (5):

[In formula (5), U represents a hydrogen atom, a methyl group, or an ethyl group, and m represents an integer of 2 to 7. * represents the bonding position with ^R2 or ^R3 .]

From the viewpoint of solubility, it is preferable that U is a methyl group and m is 4 or more.

The quaternary ammonium group may be a group represented by the following formula (6):

[In formula (6), R ¹¹ to R ¹³ each independently represent an alkyl group having 1 to 4 carbon atoms, and T represents a counter ion. * represents the bonding position with R ² or R ^3. ]

From the viewpoint of solubility, R ¹¹ to R ¹³ are preferably a methyl group or an ethyl group.
Specific examples of T include a chlorine atom, a bromine atom, an iodine atom, tetrafluoroboric acid (BF ₄ ), and hexafluorophosphoric acid (PF ₆ ). Among these, from the viewpoint of the stability of the compound, a chlorine atom, a bromine atom, and an iodine atom are preferred.

Examples of salts of sulfonic acid include sodium salts, potassium salts, and cesium salts. From the viewpoint of solubility, sodium salts are particularly preferred.

^<Z1>
Z1 represents a direct bond or a divalent aromatic linking group.
Z ¹ is preferably a direct bond in terms of ease of production. Z ¹ is preferably a divalent aromatic linking group in terms of being able to distance the N-hydroxysuccinimide ester group from the dye skeleton, and is preferably any one of a phenylene group, a biphenylene group, a terphenylene group, and a fluorenediyl group in terms of preventing the absorption wavelength from becoming shorter.

<R ¹ >
R ¹ represents a group connecting Z ¹ and the N-hydroxysuccinimide ester group via three or more single bonds. R ¹ is preferably represented by the following formula (7).

[In the formula, Q represents any group selected from the group consisting of -CH ₂ -, -O-, -CO-, -NH-, and -S-, and p represents an integer of 2 to 30. The p number of Q's may be the same or different.]

Among these, Q preferably contains -CH ₂ - or -O- in terms of excellent chemical durability.

<Binding Site of ^Z1 >
^Z1 may be bonded to any position of the azadipyrromethene structure. ^Z1 may be bonded via ^Ar2 or ^Ar1 , or may be bonded to the 4-position of the azadipyrromethene structure (β-position of the pyrrole ring) as in formula (3) described below. From the viewpoint of ease of production, it is preferable that Z1 be bonded to the position in formula (3).

<Suitable dyes>
The dye of formula (1) is preferably such that the substitution position of ^Z1 in formula (1) is the 4-position of the azadipyrromethene structure (the β-position of the pyrrole ring). That is, it is preferably a compound represented by the following formula (3), and particularly preferably a compound represented by the following formula (3) in which ^Y1 is the following formula (4).

[ ^{In formula (3), Ar 1 , Ar 2 , Y 1 , Z 1 and R 1 have the same meanings as those} in formula (1).]

In formula (4), * represents a bond to a boron atom.
^R4 is any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
n represents an integer of 1 or more and 5 or less.

^<R4>
R4 is any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof. Among these, from the viewpoint of solubility in water, any one of a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof, is preferred.
Suitable examples of the polyalkyl ether group having 4 to 20 carbon atoms, the quaternary ammonium group, the sulfonic acid group, and the salts of sulfonic acid are the same as the substituents that may be possessed by ^R2 and ^R3 described above.

<Specific examples>
Preferred specific examples of the dye of formula (1), which is the compound of the present invention, are shown below, but the present invention is not limited thereto. In the following, Me represents a methyl group.

<Synthesis Method>
As shown in the following reaction scheme, the compound of the present invention can be synthesized by synthesizing an intermediate in which a carboxylic acid is substituted on a structure consisting of an azadipyrromethene and a boron atom, then binding an aryloxy group to the boron atom using a Lewis acid, and then converting the carboxylic acid group into an N-hydroxysuccinimide ester group.
A specific synthesis method is as shown in the synthesis example of compound 1 described in the Examples section below.

[In the above reaction formula, X ¹ , Ar ¹ , Ar ² , Y ¹ , Z ¹ and R ¹ are the same as X ¹ , Ar ¹ , Ar ² , Y ¹ , Z ¹ and R ¹ in the above formula (1).]

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples, and the present invention can be modified as desired without departing from the gist of the invention.

<Synthesis of Compound 1>

Intermediate 1 (9.44 g, synthesized according to the method described in J. Am. Chem. Soc. 2004, 126, 34, 10619-10631) and dichloromethane (500 mL) were placed in a 1 L eggplant flask, and N-bromosuccinimide (3.10 g) was added while stirring at room temperature, and the mixture was stirred at room temperature for 2.5 hours. Water (200 mL) was added for liquid separation and washing. The oil phase was further washed twice with water (200 mL). The oil phase was collected and concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/hexane = 60/40 → 100/0), yielding 10.49 g of intermediate 2 as a dark green solid with metallic luster.

1-(tosyloxy)-3,6,9,12-tetraoxapentadecan-15-oic acid tert-butyl (4.99 g), 4-bromophenol (2.17 g), potassium carbonate (2.17 g), and N,N-dimethylformamide (20 mL) were placed in a 100 mL recovery flask and stirred at 70°C for 5 hours under a nitrogen atmosphere. After cooling to room temperature, the solvent was concentrated under reduced pressure and the resulting residue was purified by silica gel column chromatography (neutral silica gel, ethyl acetate/hexane = 5/5), yielding 4.32 g of intermediate 3 as a colorless, transparent oil.

Intermediate 3 (4.32 g), bis(pinacolato)diboron (2.76 g), potassium acetate (4.44 g), dichloro(1,1'-bis(diphenylphosphino)ferrocene)palladium-dichloromethane adduct (0.37 g) and 1,4-dioxane (70 mL) were placed in a 200 mL flask and stirred at 100°C for 8 hours under a nitrogen atmosphere. After cooling to room temperature, water (200 mL) and dichloromethane (300 mL) were added for separation and washing. The oil phase was recovered and concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, ethyl acetate/hexane = 5/5), yielding 4.57 g of intermediate 4 as a pale yellow oil.

Under a nitrogen atmosphere, intermediate 2 (3.12 g), intermediate 4 (3.38 g), toluene (167 mL), tetrahydrofuran (50 mL), and 2 mol/L tripotassium phosphate aqueous solution (15.6 mL) were placed in a 300 mL flask and stirred. A catalyst solution prepared by stirring palladium acetate (117 mg), 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (428 mg), and tetrahydrofuran (16 mL) at room temperature for 10 minutes in a 30 mL Schlenk flask under a nitrogen atmosphere was added to the solution, and the mixture was stirred at 80°C for 4 hours. After cooling to room temperature, the aqueous layer was removed, and the remaining organic layer was concentrated under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (neutral silica gel, dichloromethane/ethyl acetate = 10/0 → 9/1), to obtain 4.04 g of intermediate 5 as a dark green solid.

Under a nitrogen atmosphere, intermediate 5 (2.43 g), acidic silica gel (13.2 g), and toluene (240 mL) were placed in a 300 mL flask and stirred at 110°C for 4 hours. After cooling to room temperature, suction filtration was performed and the filtered material (silica gel) was washed with acetone (400 mL). The obtained filtrate was subjected to solvent distillation under reduced pressure to obtain 2.37 g of intermediate 6 as a dark green solid.

Under a nitrogen atmosphere, methyl gallate (5.50 g), triethylene glycol 2-bromoethyl methyl ether (26.5 g), potassium carbonate (16.5 g), and N,N-dimethylformamide (50 mL) were placed in a 200 mL flask and stirred at 70°C for 21 hours. After cooling to room temperature, water (150 mL) and ethyl acetate (300 mL) were added for liquid separation and washing. The oil phase was recovered and concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 3/1 → 2/1), yielding 16.3 g of intermediate 7 as a colorless, transparent oil.

Intermediate 7 (16.3 g), ethanol (400 mL), distilled water (100 mL), and potassium hydroxide (9.81 g) were placed in a 1 L flask and stirred at 100°C for 7 hours. After cooling to room temperature, dilute hydrochloric acid was added to neutralize (pH = 6). After concentrating under reduced pressure, dichloromethane (300 mL) and water (100 mL) were added for separation and washing. The organic layer was dried over magnesium sulfate and filtered, and the filtrate was distilled under reduced pressure to obtain 14.6 g of intermediate 8 as a colorless, transparent oil.

Under a nitrogen atmosphere, intermediate 8 (14.6 g), N-hydroxysuccinimide (2.52 g), and dichloromethane (300 mL) were placed in a 500 mL flask and stirred at 0°C. N,N'-diisopropylcarbodiimide (3.4 mL) was added thereto, and the mixture was stirred at room temperature for 2.5 hours. After removing the white precipitate by filtration, the filtrate was concentrated under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 1/0 → 2/1 → 1/1 → 3/7) to obtain 15.4 g of intermediate 9 as a colorless, transparent oil.

Under a nitrogen atmosphere, 4-(aminomethyl)phenol (3.35 g), intermediate 9 (15.4 g), triethylamine (3.9 mL), and tetrahydrofuran (250 mL) were placed in a 500 mL flask and stirred at room temperature for 2 hours. The reaction solution was concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 3/2 → 1/1 → 2/3), yielding 8.29 g of intermediate 10 as a colorless, transparent oil.

Under a nitrogen atmosphere, intermediate 6 (610 mg) and dichloromethane (100 mL) were placed in a 200 mL flask and stirred at room temperature. Aluminum chloride (182 mg) was added and stirred at room temperature for 15 minutes. Intermediate 10 (575 mg) was added and stirred at room temperature for 5 minutes. After filtration, the solution was concentrated under reduced pressure and purified by silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 1/1 → dichloromethane/methanol = 8/2) and reverse phase silica gel column chromatography (acetonitrile only). The above reaction and purification were carried out a total of three times, and 191 mg of intermediate 11 was obtained as a dark green solid.

Under a nitrogen atmosphere, intermediate 11 (191 mg), N-hydroxysuccinimide (15.2 mg), and dichloromethane (18 mL) were placed in a 100 mL flask and stirred at room temperature. N,N'-diisopropylcarbodiimide (17.1 mg) was added thereto, and the mixture was stirred at room temperature for 1 hour. The solution was concentrated under reduced pressure and purified by silica gel column chromatography (neutral silica gel, ethyl acetate → dichloromethane → acetone), then reverse-phase silica gel column chromatography (acetonitrile only), and finally silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 1:1 → 1:2), to obtain 40.7 mg of compound 1 as a dark green solid.

<Synthesis of Comparative Compound 1>

Intermediate 12 (1.69 g, synthesized according to the method described in Org. Lett. 2009, 11, 23, 5386-5389) and N,N-dimethylformamide (75 mL) were placed in a 200 mL recovery flask and cooled in an ice bath under a nitrogen atmosphere. Imidazole (1.76 g) and tert-butyldimethylsilyl chloride (1.93 g) were added thereto and stirred at room temperature for 3 hours. Water (200 mL) and ethyl acetate (500 mL) were further added for separation and washing. The oil phase was collected and concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/hexane = 1/2), yielding 1.87 g of intermediate 13 as a black-green solid.

Intermediate 13 (1.86 g) and dichloromethane (115 mL) were placed in a 500 mL recovery flask, and N-bromosuccinimide (0.44 g) was added while stirring at room temperature, and the mixture was stirred at room temperature for 2 hours. The solvent was concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/hexane = 35/65), yielding 2.05 g of intermediate 14 as a dark green solid with metallic luster.

Under a nitrogen atmosphere, intermediate 14 (1.0 g), intermediate 4 (0.88 g), toluene (35 mL), tetrahydrofuran (8 mL), and 2 mol/L tripotassium phosphate aqueous solution (3.6 mL) were placed in a 300 mL flask and stirred. A catalyst solution prepared by stirring palladium acetate (27 mg), 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (99 mg), and tetrahydrofuran (7 mL) at room temperature for 10 minutes in a 30 mL Schlenk flask was added to the solution and stirred at 80°C for 1.5 hours. After cooling to room temperature, the residue obtained by concentrating under reduced pressure was purified by silica gel column chromatography (neutral silica gel, dichloromethane/ethyl acetate/methanol = 5/5/0 → 2/2/1). The obtained crude product was placed in a 300 mL flask, and tetrahydrofuran (50 mL), acetic acid (32 mg), and 1M tetra-n-butylammonium fluoride/tetrahydrofuran solution (0.54 mL) were added and stirred at room temperature for 30 minutes. The residue obtained by concentrating under reduced pressure was purified by silica gel column chromatography (neutral silica gel, ethyl acetate/dichloromethane = 4/6), yielding 1.02 g of intermediate 15 as a dark green solid.

Intermediate 15 (1.00 g), dichloromethane (50 mL) and tetrahydrofuran (30 mL) were placed in a 300 mL recovery flask, and N-bromosuccinimide (0.19 g) was added while stirring at room temperature, and the mixture was stirred at room temperature for 40 minutes. Water (100 mL) and ethyl acetate (200 mL) were added to the mixture for liquid separation and washing. The oil phase was collected and concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/ethyl acetate/methanol = 5/5/0 → 25/25/2), yielding 1.04 g of intermediate 16 as a dark green solid.

Intermediate 16 (0.25 g), 1,3-propane sultone (0.15 g), cesium carbonate (0.41 g) and tetrahydrofuran (40 mL) were placed in a 200 mL flask and stirred at 80°C under a nitrogen atmosphere for 2.5 hours. After cooling to room temperature, the mixture was concentrated under reduced pressure, and acetone (20 mL) and diethyl ether (120 mL) were added and filtered with suction. The resulting filtered product was purified by reversed-phase silica gel column chromatography (acetonitrile/water = 5/5), yielding 0.14 g of intermediate 17 as a dark blue solid.

Intermediate 17 (120 mg) and 4M hydrogen chloride/1,4-dioxane solution (40 mL) were placed in a 200 mL flask and stirred at room temperature for 2.5 hours, after which the solvent was removed under reduced pressure. Water (30 mL) and sodium carbonate (60 mg) were added and stirred at room temperature for 10 minutes. After concentrating under reduced pressure, the resulting residue was purified by reverse-phase silica gel column chromatography (acetonitrile/water = 5/5), yielding 109 mg of intermediate 18 as a dark blue solid.

Intermediate 18 (43 mg), N,N'-disuccinimidyl carbonate (28 mg), pyridine (0.2 mL) and dimethyl sulfoxide (7 mL) were placed in a 200 mL flask and stirred at 55°C for 3 hours under a nitrogen atmosphere. After cooling to room temperature, diethyl ether (80 mL) was added and the supernatant was removed. Methanol was added to the residue and concentrated under reduced pressure. Purification by reverse phase silica gel column chromatography (acetonitrile/water = 5/5) yielded 45 mg of comparative compound 1 as a dark blue solid.

<Synthesis of comparative compound 2>

Under a nitrogen atmosphere, intermediate 19 (0.70 g, purchased from Tokyo Kasei), phenylboronic acid (0.20 g), toluene (20 mL), ethanol (10 mL), and 2 mol/L tripotassium phosphate aqueous solution (2.0 mL) were placed in a 200 mL flask and stirred. Tetrakis(triphenylphosphine)palladium (38 mg) was added to the solution and stirred at 100°C for 3 hours. After cooling to room temperature, the aqueous phase was removed and the solution was concentrated under reduced pressure. The resulting residue was dissolved in dichloromethane (40 mL), activated clay (3.0 g) was added, and the mixture was stirred at room temperature for 10 minutes. The mixture was filtered under suction, and the filtered product (activated clay) was washed with dichloromethane, and the filtrate was concentrated under reduced pressure. The resulting residue was dissolved in dichloromethane (10 mL), and methanol (50 mL) was added little by little. The precipitate was collected by suction filtration and dried under reduced pressure to obtain 0.40 g of intermediate 20 as an orange solid.

Under a nitrogen atmosphere, intermediate 20 (100 mg) and dichloromethane (15 mL) were placed in a 30 mL flask and stirred at room temperature. Aluminum chloride (66.9 mg) was added thereto and stirred at room temperature for 15 minutes. Intermediate 10 (206 mg) was added thereto and stirred at room temperature for 10 minutes. After filtration, the solution was concentrated under reduced pressure and purified by reverse phase silica gel column chromatography (acetonitrile only) and then silica gel column chromatography (neutral silica gel, dichloromethane/acetone = 2/1 → 1/1), obtaining 13.1 mg of comparative compound 2 as an orange solid.

<Evaluation of Absorption Spectrum>
A 10 ⁻⁵ mol/L dichloromethane solution of Compound 1 was prepared and the absorption spectrum was measured using a spectrophotometer "U-3900H" manufactured by Hitachi, Ltd. The measurement wavelength range was 300 nm to 900 nm.
The measurement results are shown in Figure 1. The maximum absorption wavelength of Compound 1 was 688 nm.

<Evaluation of aryloxy group elimination by near-infrared light irradiation>
A 30% by weight aqueous solution of acetonitrile containing each of the compounds shown below at a concentration of 25 μM was prepared, and each was irradiated with light (LED-41VIS700, Optocord Corporation) (maximum wavelength 700 nm) in a dark place for 40 minutes.

As a result, for compound 1, precipitation of a dark green solid was observed after irradiation with near-infrared light. This is because the aryloxy group bonded to the boron atom of the aza-BODIPY moiety was detached by irradiation with near-infrared light as shown below, and the pigment moiety, which had reduced water solubility, aggregated.

On the other hand, for Comparative Compound 1 and Comparative Compound 2, no precipitation was observed after irradiation with near infrared light.

Claims (3)

A compound represented by the following formula (1):

In formula (1), Ar ¹ represents a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
^Ar2 represents a hydrogen atom or a (hetero)aryl group having 3 to 20 carbon atoms which may have a substituent.
However, Ar ¹ or Ar ² may be bonded to Z ¹ , or a substituent possessed by Ar ¹ or Ar ² may be bonded to Z ¹ .
The substituents which Ar ¹ and Ar ² may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a (hetero)aryloxy group having 3 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, an alkylamino group having 2 to 20 carbon atoms, an arylamino group having 6 to 20 carbon atoms, an alkylamide group having 2 to 20 carbon atoms, a (hetero)aryl group having 3 to 20 carbon atoms, and a polyalkyl ether group having 4 to 16 carbon atoms, or a combination thereof.
^Y1 represents the following formula (2).

In formula (2), * represents a bond to a boron atom.
^R2 and ^R3 each independently represent a hydrogen atom, or an optionally substituted alkyl group having 1 to 20 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, an arylcarbonyl group having 7 to 20 carbon atoms, or a (hetero)aryl group having 3 to 20 carbon atoms.
The substituents which ^R2 and ^R3 may have are any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
However, R ² and R ³ cannot be hydrogen atoms at the same time.
^Z1 represents a direct bond or a divalent aromatic linking group.
^R1 represents a group connecting ^Z1 and the N-hydroxysuccinimide ester group via three or more single bonds. The compound according to claim 1, wherein the compound represented by formula (1) is a compound represented by the following formula (3):

[ ^{In formula (3), Ar 1 , Ar 2 , Y 1 , Z 1 and R 1 have the same meanings as those} in formula (1).] The compound according to claim 2, wherein in the compound represented by formula (3), Y ¹ is a compound represented by the following formula (4):

In formula (4), * represents a bond to a boron atom.
^R4 is any one of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, a polyalkyl ether group having 4 to 20 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.
n represents an integer of 1 or more and 5 or less.

Images