JP7663045B2 - Compound - Google Patents

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 generally 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.

In addition, the introduction of heavy atoms into appropriate positions in the skeleton of a fluorescent dye can promote intersystem crossing from the excited singlet state to the excited triplet state. It has been reported that the excited triplet state energy of the fluorescent dye is transferred to an oxygen molecule to generate singlet oxygen. For this reason, in recent years, there has been interest in applying the characteristics of these fluorescent dyes to the field of photodynamic therapy (for example, Non-Patent Document 1).

International Publication No. 2007/005222

Chem. Soc. Rev., 2013, 42, 77-88

However, although the above-mentioned prior art dyes absorb light in the near-infrared region, they do not have binding sites for biological substances such as antibodies, and therefore are not necessarily effective compounds for application in the field of photodynamic therapy, and there was a demand for the development of new dyes.

The present invention provides a near-infrared light absorbing dye compound that has an N-hydroxysuccinimide ester group that serves as a binding site for biological substances, and that generates singlet oxygen by absorbing and exciting light in a wavelength range known as the biological window.

As a result of intensive research conducted in light of the above problems, the present inventors discovered that a dye compound in which an N-hydroxysuccinimide ester group is linked via a spacer to a skeleton having a structure consisting of an azadipyrromethene substituted with a halogen atom and a boron atom (azaBODIPY skeleton) has an absorption wavelength of 650 nm or more, which corresponds to the wavelength range known as the biological window, and can be easily introduced into biological materials, 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), X ¹ represents a halogen atom.
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, a polyalkyl ether group having 4 to 16 carbon atoms, a quaternary ammonium group, a sulfonic acid group, or a salt of sulfonic acid, or a combination thereof.
^Y1 represents a fluorine atom or a trifluoromethyl group.
^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 (2):

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

[3] The compound according to [2], wherein the compound represented by formula (2) 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 Ar ¹ , Ar ² , Y ¹ , Z ¹ and R ¹ in formula (1).]

The present invention provides a dye compound that corresponds to a wavelength range known as the biological window and has an N-hydroxysuccinimide ester group, which is a binding site for biological substances.

2 is a chart showing absorption spectrum measurement of Compound 1, Compound 2, and Intermediate 15.

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 gist of the invention.

In this specification, the terms "(hetero)aryloxy group" and "(hetero)aryl group" refer to an aryloxy group which may contain a heteroatom and an aryl group which may contain a heteroatom, respectively. "May contain a heteroatom" refers to one or more carbon atoms among the carbon atoms forming the main skeleton of the aryl group or aryloxy group being 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, sometimes referred to as "dye of formula (1)").

In formula (1), X ¹ represents a halogen atom.
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, a polyalkyl ether group having 4 to 16 carbon atoms, a quaternary ammonium group, a sulfonic acid group, or a salt of sulfonic acid, or a combination thereof.
^Y1 represents a fluorine atom or a trifluoromethyl group.
^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 consisting of azadipyrromethene and boron atoms (azaBODIPY skeleton), and therefore exhibits absorption in the relatively long wavelengths from red to infrared. Furthermore, when excited by the corresponding light, the dye has the characteristic of being able to transfer its energy to surrounding molecules. 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 it is possible to easily introduce one dye molecule to a primary amine in a biological material while maintaining the excellent optical properties described above.

In addition, one of the characteristics of the dye of formula (1) is that X ¹ (a halogen atom) is bonded to the 4-position of the azaBODIPY skeleton (the β-position of the pyrrole ring). In the azaBODIPY skeleton, the HOMO (highest occupied molecular orbital) is widely distributed at the 4-position, and therefore the direct bonding of a halogen atom to this position results in the strongest interaction between the azaBODIPY skeleton and the halogen atom. Therefore, when light corresponding to the absorption wavelength of the dye of formula (1) is irradiated, it is presumed that the dye of formula (1) excited to the singlet state is likely to undergo intersystem crossing to the excited triplet state due to the heavy atom effect of the halogen atom. Because of such optical properties, when oxygen molecules coexist under light irradiation, singlet oxygen is generated (energy transfer occurs from the dye of formula (1) to the oxygen molecules, and the oxygen molecules are excited to singlet oxygen). Singlet oxygen can inactivate, for example, cancer cells in a living body. Therefore, it is considered that cancer cells can be inactivated more effectively by generating singlet oxygen in a living body by binding the compound of the present invention, which is the dye of formula (1), to, for example, an antibody.

^<X1>
X1 represents a halogen atom.
X ¹ is preferably a bromine atom or an iodine atom from the viewpoint of the heavy atom effect, and more preferably a bromine atom from the viewpoint of the photostability of the compound.

<Y ¹ >
^Y1 represents a fluorine atom or a trifluoromethyl group.
^Y1 is preferably a fluorine atom in terms of ease of production, and is preferably a trifluoromethyl group in terms of photostability.
In addition, the two Y ^{1 s} in the formula (1) may be the same as or different from each other.

<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 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, a polyalkyl ether group having 4 to 16 carbon atoms, a quaternary ammonium group, a sulfonic acid group, or a salt of sulfonic acid, or a combination thereof. Of 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 polyalkyl ether group having 4 to 10 carbon atoms, a quaternary ammonium group, a sulfonic acid group, or a salt of sulfonic acid, 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>
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)aryl groups include phenyl, naphthyl, biphenyl, terphenyl, and pyridyl 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 n 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.

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 Ar ¹ or Ar ^2. ]

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 sulfonic acid salts include sodium salts, potassium salts, and cesium salts.

^<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, it is preferably 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 10 carbon atoms, a quaternary ammonium group, a sulfonic acid group, and a salt of sulfonic acid, or a combination thereof.

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

^<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 m represents an integer of 2 to 30. The m 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 (2) described below. From the viewpoint of ease of production, it is preferable that Z1 be bonded to the position in formula (2).

<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 (2), and particularly preferably a compound represented by the following formula (3) in which ^X1 is a bromine atom.

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

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

<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 to these.

<Synthesis Method>
As shown in the reaction formula below, the compound of the present invention can be synthesized by synthesizing an intermediate in which a halogen atom and a protected carboxylic acid are substituted on a structure consisting of an azadipyrromethene and a boron atom, deprotecting the protecting group of the carboxylic acid to convert it into a carboxylic acid intermediate or a carboxylate intermediate, and then converting the carboxylic acid intermediate or the carboxylate intermediate 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 defined 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 (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 and stirred at room temperature for 3 hours. Water (200 mL) and ethyl acetate (500 mL) were then added for separation and washing. The oil phase was collected and concentrated under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (neutral silica gel, dichloromethane/hexane = 1/2), yielding 1.87 g of intermediate 2 as a black-green solid.

Intermediate 2 (1.86 g) and dichloromethane (115 mL) were placed in a 500 mL recovery flask, and while stirring at room temperature, N-bromosuccinimide (0.44 g) was added and stirred at room temperature for 2 hours. The solvent was concentrated under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (neutral silica gel, dichloromethane/hexane = 35/65), yielding 2.05 g of intermediate 3 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 4 as a colorless, transparent oil.

Intermediate 4 (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 5 as a pale yellow oil.

Under a nitrogen atmosphere, intermediate 3 (1.0 g), intermediate 5 (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 the mixture was 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 6 as a dark green solid.

Intermediate 6 (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 7 as a dark green solid.

Intermediate 7 (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 8 as a dark blue solid.

Intermediate 8 (120 mg) and 4 M hydrogen chloride/1,4-dioxane solution (40 mL) were placed in a 200 mL flask, stirred at room temperature for 2.5 hours, and then concentrated under reduced pressure to obtain a crude product of Intermediate 9. This product was used in the next reaction without purification.
The crude intermediate 9 was placed in a 200 mL flask, water (30 mL) and sodium carbonate (60 mg) were added, and the mixture was stirred at room temperature for 10 minutes. The mixture was concentrated under reduced pressure, and the resulting residue was purified by reversed-phase silica gel column chromatography (acetonitrile/water=5/5) to obtain 109 mg of intermediate 10 as a dark blue solid.

Intermediate 10 (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. It was purified by reverse phase silica gel column chromatography (acetonitrile/water = 5/5) to obtain 45 mg of compound 1 as a black-blue solid.

<Synthesis Example of Compound 2>

Intermediate 1 (1.20 g) and N,N-dimethylformamide (35 mL) were placed in a 300 mL flask and stirred at 50°C under a nitrogen atmosphere. 2-(tert-butoxycarbonylamino)ethyl bromide (total 44.2 g) and potassium carbonate (total 28.3 g) were gradually added to the solution while stirring at 50°C for 15.5 hours. After cooling to room temperature, water (250 mL) and a mixed solvent of hexane/ethyl acetate (1/3) (400 mL) were added for separation and washing. The oil phase was recovered and concentrated under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (neutral silica gel, dichloromethane/ethyl acetate = 97/3 → 9/1), yielding 1.58 g of intermediate 11 as a dark green solid.

Intermediate 11 (2.20 g) and dichloromethane (270 mL) were placed in a 500 mL recovery flask, and N-bromosuccinimide (0.48 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/ethyl acetate = 95/5 → 9/1), yielding 2.40 g of intermediate 12 as a dark green solid.

4-(4-bromophenyl)butyric acid (10.6 g) and methanol (200 mL) were placed in a 500 mL recovery flask, and concentrated sulfuric acid (2.5 mL) was added dropwise while stirring, followed by stirring at 90°C for 3 hours. After cooling to room temperature, water (200 mL) and dichloromethane (150 mL) were added for liquid separation and washing. The oil phase was dried over magnesium sulfate, filtered and concentrated under reduced pressure to obtain 11.2 g of intermediate 13 as a colorless oil.

In a 500 mL flask, intermediate 13 (11.2 g), bis(pinacolato)diboron (12.7 g), potassium acetate (12.8 g), dichloro(1,1'-bis(diphenylphosphino)ferrocene)palladium dichloromethane adduct (1.1 g), and dimethyl sulfoxide (100 mL) were placed and stirred at 85°C for 5 hours. After cooling to room temperature, water (300 mL) and dichloromethane (150 mL) were added for separation and washing, and further extraction was performed with dichloromethane (100 mL). 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 = 1/4), yielding 11.9 g of intermediate 14 as a colorless oil.

Under a nitrogen atmosphere, intermediate 12 (2.21 g), intermediate 14 (1.02 g), toluene (80 mL), tetrahydrofuran (27 mL), and 2 mol/L tripotassium phosphate aqueous solution (7.4 mL) were placed in a 300 mL flask and stirred. A catalyst solution prepared by stirring palladium acetate (55.5 mg), 2-dicyclohexylphosphino-2',6'-dimethoxy-1,1'-biphenyl (202 mg), and tetrahydrofuran (5 mL) at room temperature for 10 minutes in a 30 mL Schlenk flask was added to the solution, and the mixture was stirred at 80°C for 7.5 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 = 95/5 → 9/1), and 1.65 g of intermediate 15 was obtained as a dark green solid.

Intermediate 15 (1.60 g) and dichloromethane (150 mL) were placed in a 500 mL recovery flask, and N-bromosuccinimide (0.28 g) was added while stirring at room temperature, and the mixture was stirred at room temperature for 1.5 hours. The solvent was concentrated under reduced pressure, and the resulting residue was purified by silica gel column chromatography (neutral silica gel, dichloromethane/ethyl acetate = 9/1 → 85/15), yielding 1.66 g of compound 2 as a dark green solid.
Although compound 2 does not have an N-hydroxysuccinimide ester group, the N-hydroxysuccinimide ester group is a group necessary for binding to a biomolecule, and it is considered that the presence or absence of an N-hydroxysuccinimide ester group has little effect on the confirmation of absorption wavelength and singlet oxygen generation ability.

<Evaluation of Absorption Spectrum>
A 10 ⁻⁵ mol/L dichloromethane solution of each of the compounds shown below was prepared and the absorption spectrum was measured using a spectrophotometer U-3900H manufactured by Hitachi, Ltd. The measurement wavelength range was 400 nm to 900 nm.

Example 1
The absorption spectrum of the obtained compound 1 was measured using an acetonitrile-water (7/3) mixed solution. The measurement results are shown in Figure 1. The maximum absorption wavelength of compound 1 was 673 nm.

(Reference Example 1)
The absorption spectrum of compound 2 was measured using a toluene solution. The measurement results are shown in Figure 1. The maximum absorption wavelength of compound 2 was 685 nm.

(Reference Example 2)
The absorption spectrum of Intermediate 15 was measured using a toluene solution. The measurement results are shown in Figure 1. The maximum absorption wavelength of Intermediate 15 was 691 nm.

<Evaluation of singlet oxygen generation ability>
The singlet oxygen generating ability was evaluated by detecting the emission of singlet oxygen. The measurement solvent was toluene, and the concentration of each compound was adjusted so that the absorbance at the excitation wavelength in a 1 cm square cell was 2. A spectrometer (Actes, CSM-330) was used, and a photomultiplier tube (Hamamatsu Photonics, R5509-43) was used as a detector. Measurement was performed at an excitation wavelength of 660 nm.

(Reference Example 3)
Singlet oxygen generation was measured for the obtained Compound 2. Light emission due to singlet oxygen was clearly observed at 1270 nm from the toluene solution of Compound 2.
From the measurement results for Compound 2, it is presumed that Compound 1 also has the ability to generate singlet oxygen.

(Reference Comparative Example 1)
Singlet oxygen generation was measured for intermediate 15. No light emission due to singlet oxygen was observed at 1270 nm from the toluene solution of intermediate 15.

Claims (2)

A compound represented by the following formula ( 2 ):

In formula ( 2 ), X ¹ represents a halogen atom.
Ar ¹ represents a phenyl group 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, a polyalkyl ether group having 4 to 16 carbon atoms, a quaternary ammonium group, a sulfonic acid group, or a salt of sulfonic acid, or a combination thereof.
^Y1 represents a fluorine atom or a trifluoromethyl group.
^Z1 represents a phenylene 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 (2) 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 Ar ¹ , Ar ² , Y ¹ , Z ¹ and R ¹ in formula ( 2 ).]

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