Boronic acid compounds and methods for producing the same

Abstract

Provided is a method by which a stably radiolabeled tyrosine derivative having a good purity can be produced in a safe manner suitable for the industrial production of pharmaceuticals.　The present invention pertains to a method for producing compound (5) and radiolabeled compound (6). [In the formulae, each symbol is as defined in the description.]

Description

[Technical Field]

[0001] The present invention relates to a novel boronic acid compound which is a production intermediate for a radiolabeled tyrosine derivative useful as an anticancer agent, a method for producing the same, and a method for producing a radiolabeled tyrosine derivative using the compound. [Background technology]

[0002] Radiolabeled tyrosine derivatives, e.g., astato( 211 At)-α-methyl-L-tyrosine ( 211 At-AAMT) is a drug that is taken up into tumor cells via the LAT1 amino acid transporter, which is specifically expressed in tumors, and is expected to be useful as an anticancer agent (Patent Document 1). Patent Document 1 states: 211 Conventionally, At-AAMT is produced by dissolving α-methyl-L-tyrosine (AMT) in sulfuric acid, adding mercury sulfate to introduce mercury onto the benzene ring, and then carrying out an astatine exchange reaction (hereinafter also referred to as the mercury method). This method uses mercury, a harmful substance, and therefore is not suitable for the manufacture of pharmaceuticals from a safety perspective. Furthermore, the synthesis yield of the above method varies relatively widely between production batches, making it unsuitable for industrial production. Furthermore, the by-production of iodine-substituted and halogen-disubstituted compounds poses problems in terms of purity. Furthermore, the produced 211 It has also been reported that At-AAMT is unstable (Non-Patent Document 1). In addition, it is generally known that halogenation of tyrosine derivatives can be easily introduced at the 3-position in the presence of an oxidizing agent, but this method is not effective for astatine (Non-Patent Document 2). On the other hand, the present inventors have reported that a boryl group (-B(OH)2) introduced into an aryl group has excellent astatine substitution ability (Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO2019 / 176505 [Patent Document 2] WO2019 / 027059 [Non-patent literature]

[0004] [Non-Patent Document 1] J Surg Oncol 1988;37:192-7 [Non-patent document 2] Int J Appl Radiat Isotop 1979; 30: 749-52 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a method for producing a radiolabeled tyrosine derivative with high purity and stability, which is safe and suitable for industrial production of pharmaceuticals. [Means for solving the problem]

[0006] The present inventors focused on the production method described in Patent Document 2 as a production method that does not use harmful substances such as mercury, and as a result of extensive research into the production of boronic acids or esters of tyrosine derivatives, which are the raw materials for the method, they were able to complete the present invention.

[0007] That is, the present invention is as follows.

[0008] [1] A method for producing a compound represented by formula (5) or a salt thereof (hereinafter also referred to as compound (5)), comprising the following steps 1 to 4:

[0009] [ka]

[0010] [In the formula, R 1 is a hydrogen atom or C 1-4 represents an alkyl group; P 1 represents an ether-type hydroxy protecting group; P 2 indicates an amino protecting group; P 3 indicates a carboxy protecting group; m represents 0, 1 or 2; X represents a halogen atom; Y represents a boryl group (-B(OH)2) or an ester group thereof. Step 1: A step of halogenating a compound represented by formula (1) or a salt thereof (hereinafter also referred to as compound (1)) to obtain a compound represented by formula (2) or a salt thereof (hereinafter also referred to as compound (2)); Step 2: A step of protecting the amino group and carboxy group of the compound represented by formula (2) or a salt thereof and protecting the hydroxy group with an ether-type protecting group to obtain a compound represented by formula (3) (hereinafter also referred to as compound (3)); Step 3: reacting the compound represented by formula (3) with a boronic acid introducing reagent in the presence of a palladium catalyst and a base to obtain a compound represented by formula (4) (hereinafter also referred to as compound (4)); Step 4: A step of removing the protecting groups of the carboxy group, amino group, and hydroxy group of the compound represented by formula (4) to obtain a compound represented by formula (5) or a salt thereof.

[0011] [2] P 1 is a benzyl group or a p-methoxybenzyl group. [3] P 3 is a benzyl group or C 1-2 The method according to the above [1] or [2], wherein the alkyl group is an alkyl group. [4] P 1 and P 3 and are both benzyl groups. [5] The method according to any one of the above [1] to [4], wherein the bonding position of the hydroxy group on the benzene ring in the formula (5) is the 4-position or the 3-position. [6] The method according to the above [5], wherein the bonding positions of the hydroxy group and Y- on the benzene ring in formula (5) are adjacent to each other. [7] The method according to any one of the above [1] to [4], wherein the bonding position of the hydroxy group on the benzene ring in formula (5) is the 4-position, and the bonding position of Y- on the benzene ring is the 3-position. [8] R 1 is a hydrogen atom or a methyl group.

[0012] [9] The method according to any one of the above [1] to [8], wherein the palladium catalyst in step 3 is [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (PdCl2(dppf)).

[10] The production method according to the above [9], wherein the reaction in step 3 is carried out in a sulfoxide solvent or an amide solvent.

[11] The method according to [9] above, wherein the base in step 3 is an alkali metal acetate.

[12] The method according to any one of the above [1] to

[11] , wherein Y is a boryl group (-B(OH)2) or a 4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl group.

[0013]

[13] A method for producing a compound represented by formula (5) or a salt thereof, comprising the following step 4:

[0014] [ka]

[0015] [In the formula, R 1 is a hydrogen atom or C 1-4 represents an alkyl group; P 1 represents an ether-type hydroxy protecting group; P 2 indicates an amino protecting group; P 3 indicates a carboxy protecting group; m represents 0, 1 or 2; Y represents a boryl group (-B(OH)2) or an ester group thereof. Step 4: A step of removing the protecting groups of the carboxy group, amino group, and hydroxy group of the compound represented by formula (4) to obtain a compound represented by formula (5) or a salt thereof.

[0016]

[14] A method for producing a compound represented by formula (4), comprising the following step 3:

[0017] [ka]

[0018] [In the formula, R 1 is a hydrogen atom or C 1-4 represents an alkyl group; P 1 represents an ether-type hydroxy protecting group; P 2 indicates an amino protecting group; P 3 indicates a carboxy protecting group; m represents 0, 1 or 2; X represents a halogen atom; Y represents a boryl group (-B(OH)2) or an ester group thereof. Step 3: A step of reacting a compound represented by formula (3) with a boronic acid introducing reagent in the presence of a palladium catalyst and a base to obtain a compound represented by formula (4).

[0019]

[15] A compound represented by the following formula (5a) or a salt thereof (hereinafter also referred to as compound (5a)):

[0020] [ka]

[0021] [In the formula, Y represents a boryl group (—B(OH)2) or an ester group thereof.]

[0022]

[16] A compound represented by the following formula (4a) (hereinafter also referred to as compound (4a)):

[0023] [ka]

[0024] [In the formula, P 1a represents a benzyl group or a p-methoxybenzyl group; P 2a indicates a tert-butoxycarbonyl group; P 3a is a benzyl group or C 1-2 represents an alkyl group; Y represents a boryl group (-B(OH)2) or an ester group thereof.

[0025]

[17] A method for producing a radiolabeled compound represented by formula (6) or a salt thereof (hereinafter also referred to as radiolabeled compound (6)), comprising the following step 5:

[0026] [ka]

[0027] [In the formula, R 1 is a hydrogen atom or C 1-4 represents an alkyl group; m represents 0, 1 or 2; Y represents a boryl group (-B(OH)2) or an ester thereof; Z is 211 At, 210 At, 123 I, 124 I, 125 I or 131 Indicates I.] Step 5: A compound represented by formula (5) or a salt thereof is reacted in water in the presence of a reagent selected from an alkali metal iodide, an alkali metal bromide, N-bromosuccinimide, N-chlorosuccinimide, N-iodosuccinimide, and hydrogen peroxide, 211 At, 210 At, 123 I, 124 I, 125 I and 131 I to obtain a radiolabeled compound of formula (6) or a salt thereof.

[0028]

[18] The method according to the above

[17] , wherein the compound represented by formula (5) or a salt thereof is produced by the method according to the above [1] to

[12] .

[19] The method according to

[17] or

[18] above, wherein the reaction is carried out in a system that does not contain an organic solvent.

[20] The method according to any one of the above

[17] to

[19] , wherein the reaction is carried out in the range of room temperature to 100°C.

[21] Radionuclides 211 At or 131 The method according to any one of the above

[17] to

[20] , wherein I is the compound I and the reagent is selected from potassium iodide and N-bromosuccinimide.

[0029]

[22] The production method according to any one of the above

[17] to

[21] , further comprising a step of purifying the radiolabeled compound represented by formula (6) or a salt thereof.

[23] The method according to any one of the above

[17] to

[22] , further comprising the step of stabilizing the radiolabeled compound represented by formula (6) or a salt thereof by adding ascorbic acid. [Effects of the Invention]

[0030] According to the present invention, a tyrosine derivative having a boryl group (-B(OH)2) or its ester group introduced therein can be obtained. Using this compound, a highly pure and stable radiolabeled tyrosine derivative can be produced by a safe method suitable for the industrial production of pharmaceuticals without using hazardous substances. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 shows an HPLC chart of 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride (5) obtained in Example 1. [Figure 2] FIG. 2 shows an HPLC chart of 3-borono-α-methyl-L-tyrosine hydrochloride (5) obtained in Example 2. [Figure 3] FIG. 3 shows the results of thin layer chromatography (TLC) analysis of the reaction mixture of Example 3. [Figure 4] FIG. 4 shows the results of thin layer chromatography (TLC) analysis of the reaction mixture of Example 4. [Figure 5] FIG. 5 shows the results of thin layer chromatography (TLC) analysis of the reaction mixture of Example 5. [Figure 6] Figure 6a shows the amount of 211At-AAMT taken up into cancer cells (synthesized by the method of the present invention), and Figure 6b shows the amount of 211At-AAMT taken up into cancer cells (synthesized by the mercury method). [Figure 7] FIG. 7 shows the cell viability of 211At-AAMT. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention will be described in detail below. In the present specification, examples of the "halogen atom" include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. In this specification, "C 1-4Examples of the "alkyl group" include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl. In this specification, "C 1-6 Examples of the "alkyl group" include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, 1-ethylpropyl, hexyl, isohexyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, and 2-ethylbutyl.

[0033] In the present specification, examples of the "ether-type hydroxy-protecting group" include a benzyl group, a p-methoxybenzyl group, a methoxymethyl group, a trimethylsilyl group, a triethylsilyl group, a trityl group, a tert-butyldimethylsilyl group, a tetrahydropyranyl group, etc. Among these, benzyl ether-type hydroxy-protecting groups such as a benzyl group and a p-methoxybenzyl group are preferred. As used herein, the term "amino protecting group" includes, for example, tert-butoxycarbonyl aryl group , benzyloxycarbonyl group, 9-fluorenylmethyloxycarbonyl group, etc. As used herein, examples of the "carboxy protecting group" include a benzyl group, C 1-2 Examples include alkyl groups (methyl groups, ethyl groups) and tert-butyl groups. As used herein, the term "boryl group (-B(OH)2)" is also referred to as a dihydroxyboryl group. In the present specification, examples of the "ester group of a boryl group" include the groups shown below.

[0034] [ka]

[0035] [In the formula, R 2 is C 1-6 represents an alkyl group.]

[0036] R 1is preferably a hydrogen atom or a methyl group, more preferably a methyl group. P 1 is preferably a benzyl ether type hydroxy protecting group, more preferably a benzyl group or a p-methoxybenzyl group, and particularly preferably a benzyl group. P 2 is preferably tert-butoxycarbonyl aryl group or a benzyloxycarbonyl group, more preferably a tert-butoxycarbonyl group. aryl group is. P 3 is preferably a benzyl group or C 1-2 It is an alkyl group (methyl group, ethyl group), and more preferably a benzyl group. m is preferably 1. X is preferably an iodine atom or a bromine atom, and particularly preferably an iodine atom. Y is preferably a boryl group (-B(OH)2) or a 4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl group.

[0037] In the present specification, when Compound (1), Compound (2), Compound (5), and radiolabeled Compound (6) are each in the form of a salt, examples of such salts include metal salts (e.g., alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as calcium salt, magnesium salt, and barium salt), ammonium salt, salts with organic bases (e.g., trimethylamine, triethylamine, pyridine, picoline, 2,6-lutidine), salts with inorganic acids (e.g., hydrochloric acid, hydrobromic acid, nitric acid, sulfuric acid), and salts with organic acids (e.g., formic acid, acetic acid, trifluoroacetic acid, phthalic acid, fumaric acid, oxalic acid, tartaric acid, maleic acid, citric acid, succinic acid, malic acid).

[0038] In the present invention, the method for producing compound (5) comprises the following steps 1 to 4.

[0039] [ka]

[0040] Step 1 is a step of halogenating compound (1) to obtain compound (2). The halogenation can be carried out by reacting compound (1) with a halogenating agent.

[0041] Examples of compound (1) include tyrosine, α-methyltyrosine, m-tyrosine, α-methyl-m-tyrosine, etc., which may be in the L-, D-, or DL-form. Among these, tyrosine and α-methyltyrosine are preferably used, and α-methyltyrosine is particularly preferably used. As compound (1), commercially available products can be used.

[0042] As the halogenating agent, an iodinating agent or a brominating agent is preferably used, and an iodinating agent is particularly preferably used. Examples of the iodinating agent include iodine and N-iodosuccinimide. Brominating agents include bromine, N-bromosuccinimide, and the like. The amount of the halogenating agent used is usually 1 to 5 moles, preferably 1 to 2 moles, per mole of Compound (1). When the halogenating agent is iodine, the reaction is carried out in the presence of potassium iodide and concentrated ammonia (28%). The amount of potassium iodide used is usually 0.5 to 5 mol, preferably 1 to 2 mol, per mol of iodine, and the amount of concentrated ammonia used is usually 5 to 200 mol, preferably 20 to 50 mol, per mol of iodine.

[0043] The reaction is usually carried out in a solvent. The solvent used in the present invention is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include water; alcoholic solvents such as ethanol, methanol, and isopropanol; and halogenated solvents such as carbon tetrachloride, and two or more of these may be mixed and used. Of these, water is preferably used. The amount of the solvent used is usually 0.1 to 100 times by volume relative to compound (1). For example, when the halogenating agent is iodine, the reaction is preferably carried out by adding (preferably dropwise) a mixture of compound (1) and concentrated ammonia (and the solvent, if necessary) to a mixture of iodine, potassium iodide, and a solvent. The reaction is usually carried out at −100 to 20° C., preferably −20 to 10° C. The reaction time varies depending on the reaction temperature, but is usually about 30 minutes to about 24 hours, preferably about 1 to about 12 hours. The completion of the reaction can be confirmed by thin layer chromatography, liquid chromatography, or the like. After completion of the reaction, compound (2) can be isolated and / or purified from the reaction mixture by conventional separation means such as concentration, crystallization, recrystallization, distillation, solvent extraction, fractional distillation, chromatography, etc.

[0044] By this reaction, a halogen is introduced into the 3-position of the benzene ring in the case of tyrosine and α-methyltyrosine (in both cases, the hydroxy group is at the 4-position of the benzene ring), and into the 4- or 6-position of the benzene ring in the case of m-tyrosine and α-methyl-m-tyrosine (in both cases, the hydroxy group is at the 3-position of the benzene ring).

[0045] Step 2 is a step in which the amino group and carboxy group of compound (2) are protected and the hydroxy group is protected with an ether-type protecting group to obtain compound (3).

[0046] The present inventors initially attempted to introduce a boryl group or its ester group into compound (2) using the well-known reaction of a halogen atom with a boronic acid-introducing reagent, but unexpectedly found that the reaction hardly proceeded. Suspecting that this was due to the hydroxyl group on the benzene ring, they attempted to introduce the boryl group or its ester group after protecting the hydroxyl group with various protecting groups. As a result, they found that the introduction reaction of the boryl group or its ester group hardly proceeded, depending on the type of protecting group. The present inventors have conducted extensive research into hydroxy-protecting groups to address the previously unknown problems inherent to tyrosine derivatives, i.e., the benzene ring containing a hydroxy group. As a result, they have discovered for the first time that the use of a specific protecting group (an ether-type protecting group, particularly a benzyl ether-type protecting group) enables the introduction of a boryl group or its ester group. Thus, in the present invention, the selection of the hydroxy-protecting group in compound (2) is an important key to the introduction of a boryl group or its ester group. In the present invention, the hydroxy protecting group is an ether-type protecting group (P 1 ) Ether-type protecting group (P 1 ), a boryl group or its ester group can be introduced. On the other hand, in the case of ester-type protecting groups such as acetyl, benzoyl, and pivaloyl groups, the introduction reaction of a boryl group or its ester group hardly proceeds. Since the boryl group or its ester group can be introduced in good yield, an ether-type protecting group (P 1 ) is a benzyl ether type protecting group, more preferably a benzyl group or a p-methoxybenzyl group, and particularly preferably a benzyl group. The benzyl group or p-methoxybenzyl group does not have a significant steric hindrance, so that a boryl group or its ester group can be introduced in high yield.

[0047] Furthermore, the present inventors unexpectedly found that in the deprotection step after introduction, the introduced boryl group or its ester group can be eliminated under strong acid conditions such as those using highly concentrated hydrochloric acid, nitric acid, or sulfuric acid, as well as boron tribromide or boron trifluoride. Such elimination is generally unlikely to occur in benzene rings that do not have hydroxy groups, but is a particular issue in benzene rings that have hydroxy groups. The present inventors have conducted extensive research into the previously unknown issues specific to tyrosine derivatives, i.e., the benzene ring containing a hydroxyl group. As a result, they have found that the use of a benzyl ether-type protecting group (particularly a benzyl group or a p-methoxybenzyl group) allows the subsequent deprotection step to be carried out under milder conditions (e.g., catalytic hydrogenation). The p-methoxybenzyl group can also be deprotected using an oxidizing agent such as 2,3-dichloro-5,6-dicyano-p-benzoquinone, trifluoroacetic acid, or a relatively low concentration of hydrochloric acid. They have also found that the use of these deprotection methods makes it difficult for the boryl group or its ester group to be removed. Thus, in the present invention, the selection of the hydroxy-protecting group of compound (2) is an important key for the removal of the boryl group or its ester group.

[0048] In addition, protecting groups for amino and carboxy groups (P 2 , P 3 ) is also selected so that the boryl group or its ester group is unlikely to be removed in the removal step in step 4. A suitable amino protecting group (P 2 ) is tert-butoxycarbonyl aryl group is. A suitable carboxy protecting group (P 3 ) is a benzyl group or C 1-2 The alkyl group is preferably a methyl group or an ethyl group, and the benzyl group is particularly preferred. A suitable combination is: Ether-type protecting group for hydroxy group (P 1 ) is a benzyl group, and the amino protecting group (P 2 ) is tert-butoxycarbonyl aryl group and a carboxy protecting group (P 3 ) is a benzyl group, Ether-type protecting group for hydroxy group (P 1 ) is a p-methoxybenzyl group, and the amino protecting group (P 2 ) is tert-butoxycarbonyl aryl group and a carboxy protecting group (P 3 ) but C 1-2Combination of alkyl groups (methyl and ethyl groups) Examples include: All of the above protecting groups can be removed under mild conditions, and the boryl group or its ester group is unlikely to be eliminated. The introduction of each protecting group can be carried out according to a method known per se, and the order of introduction of each protecting group is also determined appropriately depending on the protecting group. After completion of the reaction, compound (3) can be isolated and / or purified from the reaction mixture by a conventional separation method such as concentration, crystallization, recrystallization, distillation, solvent extraction, fractional distillation, or chromatography.

[0049] Step 3 is a step in which compound (3) is reacted with a boronic acid introducing reagent in the presence of a palladium catalyst and a base to obtain compound (4).

[0050] Examples of the boronic acid introducing reagent include 4,4,4',4',5,5,5',5'-octamethyl-2,2'-bi-1,3,2-dioxaborolane (also known as bis-pinacolatodiboron), 4,4,5,5-trimethyl-1,3,2-dioxaborolane, and tetrahydroxydiborane. Of these, bis-pinacolatodiboron is preferred. Commercially available boronic acid introducing reagents can be used. The amount of the boronic acid introducing reagent used is usually 1 to 10 moles, preferably 1 to 3 moles, per mole of compound (3).

[0051] Examples of palladium catalysts include [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (PdCl(dppf)) or its dichloromethane adduct, palladium acetate, and tetrakis(triphenylphosphine)palladium(0) (Pd(PPh)). Of these, PdCl(dppf) is preferably used. The amount of the palladium catalyst used is usually 0.001 to 1 mol, preferably 0.01 to 0.2 mol, per 1 mol of compound (3). Examples of the base include alkali metal acetates such as potassium acetate and sodium acetate, and among these, alkali metal acetates are preferably used, with potassium acetate being particularly preferred. The amount of the base used is usually 0.5 to 10 mol, preferably 1 to 5 mol, per 1 mol of compound (3).

[0052] The reaction is usually carried out in a solvent. The solvent used in the present invention is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include sulfoxide solvents such as dimethyl sulfoxide; amide solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidinone; and ether solvents such as tetrahydrofuran and 1,4-dioxane, and two or more of these may be used in combination. Among these, sulfoxide solvents and amide solvents are preferably used, and dimethyl sulfoxide is particularly preferably used. The amount of the solvent used is usually 0.1 to 100 times by volume relative to compound (3). The reaction is preferably carried out, for example, by adding (preferably dropwise) a boronic acid introducing reagent to a mixture of compound (3), a palladium catalyst, a base and a solvent. The reaction is usually carried out at 0 to 200° C., preferably room temperature to 120° C. The reaction time varies depending on the reaction temperature, but is usually about 10 minutes to about 48 hours, preferably about 1 to about 12 hours. The completion of the reaction can be confirmed by thin layer chromatography, liquid chromatography, or the like. After completion of the reaction, compound (4) can be isolated and / or purified from the reaction mixture by a conventional separation method such as concentration, crystallization, recrystallization, distillation, solvent extraction, fractional distillation, or chromatography.

[0053] Among the compounds (4), the compound represented by the following formula (4a) is a novel compound.

[0054] [ka]

[0055] [In the formula, P 1a represents a benzyl group or a p-methoxybenzyl group; P 2aindicates a tert-butoxycarbonyl group; P 3a is a benzyl group or C 1-2 represents an alkyl group; Y has the same meaning as defined above.]

[0056] Step 4 is a step in which the protecting groups of the carboxyl group, amino group, and hydroxyl group of compound (4) are removed to obtain compound (5). Removal of each protecting group is carried out by a method known per se. For example, Hydroxy protecting group (P 1 ) / carboxy protecting group (P 3 When ) is a benzyl group, this is carried out by catalytic hydrogenation. Hydroxy protecting group (P 1 When ) is a p-methoxybenzyl group, the reaction is carried out by catalytic hydrogenation or treatment with an acid such as trifluoroacetic acid or hydrogen chloride. Carboxy protecting group (P 3 ) is C 1-2 In the case of alkyl groups (methyl and ethyl groups), the reaction is carried out by treating with a base such as lithium hydroxide or sodium hydroxide. Amino protecting group (P 2 When ) is a tert-butoxycarbonyl group, the reaction is carried out by treating with an acid such as trifluoroacetic acid or hydrogen chloride. The above protecting groups can be removed under mild conditions, and the boryl group (-B(OH)2) or its ester group is unlikely to be removed. After completion of the reaction, compound (5) can be isolated and / or purified from the reaction mixture by a conventional separation method such as concentration, crystallization, recrystallization, distillation, solvent extraction, fractional distillation, or chromatography.

[0057] Among the compounds (5), the compound represented by the following formula (5a) or a salt thereof is a novel compound.

[0058] [ka]

[0059] [In the formula, Y has the same meaning as defined above.]

[0060] The compound (5) thus produced can be converted into a radiolabeled compound (6) useful as an anticancer agent by a method comprising the following step 5.

[0061] [ka]

[0062] [Wherein Z is 211 At, 210 At, 123 I, 124 I, 125 I or 131 I, and other symbols have the same meanings as above.]

[0063] Step 5 comprises treating compound (5) in water in the presence of a reagent selected from an alkali metal iodide, an alkali metal bromide, N-bromosuccinimide, N-chlorosuccinimide, N-iodosuccinimide, and hydrogen peroxide, 211 At, 210 At, 123 I, 124 I, 125 I and 131 and reacting the compound (6) with a radionuclide selected from I to obtain a radiolabeled compound (6).

[0064] Since the reaction in this step is carried out in water, compound (5) may be in the free form or in the form of a salt, for example, hydrochloride, as long as it is soluble in water.

[0065] Examples of alkali metal iodides include potassium iodide and sodium iodide, and among these, potassium iodide is preferably used. Examples of the alkali metal bromides include sodium bromide and potassium bromide.

[0066] Suitable combinations of radionuclides and the above reagents include: (1) Radioactive nuclides211 At or 210 At and the reagent is selected from potassium iodide, sodium bromide, N-bromosuccinimide, N-chlorosuccinimide, N-iodosuccinimide, and hydrogen peroxide; (2) Radionuclides 123 I, 124 I, 125 I or 131 I and the reagent is selected from N-bromosuccinimide and N-chlorosuccinimide; The above reagents may be used alone or in combination of two or more. The above reagents are usually used in the form of an aqueous solution. In a preferred embodiment, the radionuclide is 211 At or 131 I and the reagent is selected from potassium iodide and N-bromosuccinimide. In a more preferred embodiment, Radionuclides 211 At and the reagent is potassium iodide, and the radionuclide is 131 I and the reagent is N-bromosuccinimide Examples include:

[0067] The reagents may be used in an amount sufficient to oxidize or reduce the radionuclide, and are usually used in large excess relative to the radionuclide. From the standpoints of reaction efficiency and economic efficiency, the reagents are preferably used at a concentration of 0.0001 to 0.2 mol / L, more preferably 0.001 to 0.1 mol / L.

[0068] The radionuclide is usually used in the reaction in the form of an aqueous solution. If necessary, an alkaline aqueous solution such as sodium hydroxide or a buffer solution may be added to the aqueous solution for the purpose of stabilizing the radionuclide. Radionuclides 211 In the case of At, bismuth is irradiated with helium particles accelerated to 28 MeV in a cyclotron, 209 Bi(α,2n) 211 By the nuclear reaction of At 211 After At is produced, the target material209 Bi is heated and melted, 211 At was evaporated and collected in a liquid nitrogen trap, and then dissolved in water. 211 Prepare At stock solution. If necessary, 211 For the purpose of stabilizing At, an alkaline aqueous solution such as sodium hydroxide or a buffer solution may be added. Radionuclides 210 In the case of At, bismuth is irradiated with helium particles accelerated to over 29 MeV in a cyclotron, 209 Bi(α,3n) 210 By the nuclear reaction of At 210 After producing At, by performing the same operation as above, 210 Prepare an At aqueous solution. Radionuclides 123 In the case of I, Na 123 It is available as an aqueous solution. Radionuclides 124 In the case of I, tellurium is irradiated with proton particles accelerated by a cyclotron, 124 Te(p,n) 124 by the nuclear reaction of I 124 After producing I, the target material 124 Dissolve Te 124 Prepare a sodium hydroxide solution of I. Radionuclides 125 In the case of I, Na 125 It is available as an aqueous solution. Radionuclides 131 In the case of I, Na 131 It is available as an aqueous solution. 211 At has a half-life of 7.2 hours. 210 At has a half-life of 8.3 hours. 123 Since I has a short half-life of 13.2 hours, the radionuclide must be used in the reaction immediately after preparation. 124 I has a half-life of 4.2 days, 125 I has a half-life of 59.4 days, 131 Although I has a relatively long half-life of 8.04 days, it is preferable to use these radionuclides in reactions as soon as possible after their preparation.

[0069] Compound (5) is usually used in large excess relative to the radionuclide, but from the standpoint of reaction efficiency and economic efficiency, it is used at a concentration of preferably 0.0001 mol / l to 0.5 mol / l, more preferably 0.001 mol / l to 0.2 mol / l relative to 1 Bq to 1,000 GBq of the radionuclide.

[0070] The reaction is carried out by mixing compound (5), the reagent, and the radionuclide, and the order of mixing is not particularly limited. Preferably, an aqueous solution of the radionuclide and then an aqueous solution of the reagent are added to an aqueous solution of compound (5), or an aqueous solution of the reagent and then an aqueous solution of the radionuclide are added to an aqueous solution of compound (5), and more preferably, an aqueous solution of the radionuclide and then an aqueous solution of the reagent are added to an aqueous solution of compound (5).

[0071] The reaction is carried out in water, i.e., in an organic solvent-free system. The reaction is carried out at room temperature, specifically at 0° C. to 40° C., and preferably at 10° C. to 35° C. In the production method of the present invention, the reaction proceeds rapidly even at room temperature and is completed in a short time, for example, 1 minute to 3 hours, and particularly 1 minute to 30 minutes. The completion of the reaction is confirmed by the disappearance of free radionuclides by thin layer chromatography (TLC) analysis.

[0072] According to the production method of the present invention, radiolabeled compound (6) can be obtained in a high radiochemical yield of 60% or more, particularly 80% or more, and especially 90% or more. After the reaction is complete, the reaction solution does not contain any organic solvents or toxic reagents, and therefore the radiolabeled compound (6) can be immediately formulated into an injection or other preparation without isolation.

[0073] Compound (6) may be purified, if necessary, to remove by-products. This purification is preferably carried out using a solid-phase extraction column. A solid-phase extraction column commonly used in the art can be used.

[0074] Furthermore, after the above purification, ascorbic acid or an ascorbate may be added to a final concentration of 0.01% to 10%, preferably 0.1% to 5%, which prevents the decomposition of compound (6) and allows it to be stored for a long period of time.

[0075] The reaction conditions such as solvents and reaction temperatures in each step of the production method of the present invention described above will be described in detail as representative examples in the Examples below, but are not necessarily limited thereto, and can be appropriately selected by a person skilled in the art based on general knowledge in organic synthesis. [Example]

[0076] The present invention will be further explained in detail by the following examples, but these are merely examples and do not limit the present invention, and can be modified within the scope of the present invention. In the following examples, the radiochemical yield was calculated according to the following formula: Radiochemical yield (%) = (radioactivity of target compound in thin-layer plate / total radioactivity in thin-layer plate) x 100

[0077] Example 1 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride ( 5 ) synthesis

[0078] [ka]

[0079] a) 3-iodo-α-methyl-L-tyrosine ( 2 ) A mixture of 10.2 g (61.4 mmol) of potassium iodide and 27 mL of water was added with 13.6 g (53.6 mmol) of iodine and stirred for 2 hours. The mixture was added to α-methyl-L-tyrosine ( 1) (10 g, 51.2 mmol), concentrated aqueous ammonia (28%, 120 mL), and water (15 mL) were added at -5°C or below, and the mixture was stirred at -7 to -5°C for 2 hours. 15% aqueous sodium sulfite solution (25 mL) was added to the reaction mixture, which was then warmed to room temperature and concentrated under reduced pressure. 6M hydrochloric acid was added to the residue under ice cooling to adjust the pH to 6.5-7, and the mixture was stirred under ice cooling for 1 hour, after which the precipitated solid was collected by filtration. After washing with cold water and acetone, the solid was dried under reduced pressure to give 3-iodo-α-methyl-L-tyrosine ( 2 ) was obtained (14.2 g, yield 86%). 1 H-NMR (300MHz, DMSO-d6+TFA, TMS): 8.25(3H, br), 7.51 (1H, d, J=2.1 Hz), 7.03 (1H, dd, J=2.1, 8.1 Hz), 6.84 (1H, d, J=8.1 Hz), 3.03 (1H, d, J=14.1 Hz), 2.87 (1H, d, J=14.1 Hz), 1.44 (3H, s)

[0080] b) N-Boc-3-iodo-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 3 ) 3-Iodo-α-methyl-L-tyrosine ( 2To a mixture of 2,4-dimethyl-3,4-dioxane (3.0 g, 9.3 mmol), 1M aqueous sodium hydroxide (9.3 mL), and 1,4-dioxane (15 mL), di-t-butyl dicarbonate (4.06 g, 18.6 mmol) was added and the mixture was stirred at 50°C for 24 hours. Di-t-butyl dicarbonate (2.0 g, 9.2 mmol) was added, and the mixture was further stirred at 60°C for 20 hours. After cooling to room temperature, the reaction mixture was concentrated under reduced pressure. Water (30 mL) and methyl t-butyl ether-heptane (1:2, 45 mL) were added to the residue, and the mixture was subjected to separation and extraction. The organic layer was washed with 5% aqueous sodium bicarbonate (20 mL) and water (20 mL). The combined washed aqueous layer was adjusted to pH 1-2 with 0.5M aqueous sodium hydrogen sulfate, and extracted with methyl t-butyl ether-ethyl acetate (1:1, 60 mL). The extract was washed with water and saturated brine. The solvent was evaporated under reduced pressure to give a white solid (2.88 g). The resulting white solid (2.88 g) was dissolved in N,N-dimethylformamide (20 mL), and potassium carbonate (2.08 g, 15 mmol) and benzyl bromide (1.8 mL, 15 mmol) were added, followed by stirring at 50°C for 3 hours. After cooling to room temperature, ethyl acetate (50 mL) was added, and the mixture was washed with water and saturated brine, after which the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography to give N-Boc-3-iodo-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 3 ) was obtained as a white solid (3.39 g, 61% yield). 1 H-NMR (300MHz, CDCl3, TMS): 7.6-7.3 (11H, m), 6.88 (1H, dd, J=2.1, 8.4 Hz), 6.67 (1H, d, J=8.4 Hz), 5.20 (1H, d, J=12.6 Hz), 5.14 (1H, d, J=12.6 Hz), 5.10 (2H, s), 3.30 (1H, d, J=13.5 Hz), 3.15 (1H, d, J=13.5 Hz), 1.55 (3H, s), 1.48 (9H, s)

[0081] c) N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 4 ) Under a nitrogen atmosphere, N-Boc-3-iodo-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 3 To a mixture of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) dichloromethane adduct (0.31 g, 0.38 mmol), potassium acetate (1.96 g, 20 mmol), and dimethyl sulfoxide (20 mL), bis-pinacolatodiboron (2.54 g, 10 mmol) was added and stirred at room temperature for 1 hour, then at 55°C for 2 hours. The reaction mixture was allowed to cool to room temperature, and methyl t-butyl ether (45 mL) and water (45 mL) were added. The mixture was then filtered through Celite. After separation, the aqueous layer was extracted with methyl t-butyl ether (30 mL). The combined organic layer was washed with water, half-saturated brine, and saturated brine, and the solvent was removed under reduced pressure. The residue was purified by silica gel column chromatography to give N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 4 ) was obtained as a white amorphous solid (2.22 g, 74% yield). 1 H-NMR (300MHz, CDCl3, TMS): 7.7-7.0 (12H, m), 6.79 (1H, d, J=8.4 Hz), 5.3-5.0 (3H, m), 5.08 (2H, s), 3.31 (1H, d, J=13.8 Hz), 3.18 (1H, d, J=13.8 Hz), 1.46 (9H, s), 1.33 (12H, s), 1.26 (3H, s)

[0082] d) 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride ( 5 ) N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-benzyl-α-methyl-L-tyrosine benzyl ester ( 4 A mixture of ) (2.2 g, 3.6 mmol), 10% palladium-carbon (55% aqueous, 0.55 g) and 22 mL of tetrahydrofuran was stirred under a hydrogen gas atmosphere for 3 hours. The reaction mixture was filtered through Celite, and the solvent was evaporated under reduced pressure to give a white amorphous substance (1.69 g). A mixture of the obtained amorphous substance (0.56 g, 1.2 mmol) and ethyl acetate (1.5 mL) was added with 4M hydrochloric acid-ethyl acetate solution (1.5 mL) and stirred at room temperature for 1 hour. The precipitated solid was collected by filtration, washed with ethyl acetate, and used as 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride ( 5 ) was obtained as a white powder (0.30 g, 70% yield). 1 H-NMR (300MHz, DMSO-d6, TMS): 8.87 (1H, s), 8.35 (3H, br), 7.33 (1H, d, J=2.4 Hz), 7.15 (1H, dd, J=2.4, 8.4 Hz), 6.79 (1H, d, J=8.4 Hz), 3.04 (1H, d, J=14.1 Hz), 2.95 (1H, d, J=14.1 Hz), 1.45 (3H, s), 1.26 (12H, s)

[0083] HPLC analysis conditions Sample solution: 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride ( 5 ) was dissolved in 1 mL of 67% acetonitrile water to prepare the sample solution. Detector: UV 275 nm Column: YMC-Pack Pro C18 RS (4.6 mmφ×25 cm, 5 μm, YMC) Column temperature: 30℃ Mobile phase: HO (0.1% TFA) / MeCN (0.1% TFA) Mode: Gradient 0 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 95 / 5 5 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 95 / 5 35 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 5 / 95 40 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 5 / 95 Flow rate: 1 mL / min Injection volume: 5 μL Analysis time: 40 minutes Retention time: 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride ( 5 ): 12.3 minutes The HPLC chart is shown in FIG.

[0084] Example 2 3-Borono-α-methyl-L-tyrosine hydrochloride ( 5 ) synthesis

[0085] [ka]

[0086] a) 3-iodo-α-methyl-L-tyrosine ( 2 ) Iodine (13.6 g, 53.6 mmol) was added to a mixture of potassium iodide (10.2 g, 61.4 mmol) and water (27 mL) and stirred for 2 hours. The mixture was added to α-methyl-L-tyrosine ( 1) 10 g (51.2 mmol), concentrated aqueous ammonia (28%, 120 mL) and water (15 mL) were added at -5°C or below, and the mixture was stirred at -7 to -5°C for 2 hours. 15% aqueous sodium sulfite solution (25 mL) was added to the reaction mixture, which was then warmed to room temperature and concentrated under reduced pressure. 6 M hydrochloric acid was added to the residue under ice-cooling to adjust the pH to 6.5-7, and the mixture was stirred under ice-cooling for 1 hour. The precipitated solid was collected by filtration. After washing with cold water and acetone, it was dried under reduced pressure to obtain 3-iodo-α-methyl-L-tyrosine ( 2 ) was obtained (14.2 g, yield 86%). 1 H-NMR (300MHz, DMSO-d6+TFA, TMS): 8.25(3H, br), 7.51 (1H, d, J=2.1 Hz), 7.03 (1H, dd, J=2.1, 8.1 Hz), 6.84 (1H, d, J=8.1 Hz), 3.03 (1H, d, J=14.1 Hz), 2.87 (1H, d, J=14.1 Hz), 1.44 (3H, s)

[0087] b) N-Boc-3-iodo-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 3 ) 3-Iodo-α-methyl-L-tyrosine ( 2To a mixture of 3.0 g (9.3 mmol) and 75 mL of ethanol, concentrated sulfuric acid (1.0 mL, 18.6 mmol) was added and the mixture was stirred under reflux for 48 hours. The mixture was allowed to cool to room temperature and concentrated. 30 mL of ice water and sodium bicarbonate (3.9 g) were added to the residue, which was then extracted with ethyl acetate (50 mL). The extract was washed with 5% aqueous sodium bicarbonate, water, and saturated brine, and the solvent was evaporated under reduced pressure to give a pale yellow syrup (1.7 g). The resulting residue was dissolved in ethyl acetate (17 mL), and di-t-butyl dicarbonate (1.1 g, 5 mmol) was added under ice cooling. The mixture was stirred at room temperature for 2 hours. Further di-t-butyl dicarbonate (1.1 g, 5 mmol) was added under ice cooling, and the mixture was stirred at room temperature for 20 hours. The solvent in the reaction mixture was evaporated under reduced pressure, and the residue was purified by silica gel column chromatography to give N-Boc-3-iodo-α-methyl-L-tyrosine ethyl ester (Intermediate A) as a white solid (2.0 g). The resulting white solid (1.85 g, 4.1 mmol) was dissolved in N,N-dimethylformamide (10 mL), and potassium carbonate (0.68 g, 4.9 mmol) and p-methoxybenzyl chloride (0.6 mL, 4.4 mmol) were added, followed by stirring at 50°C for 2 hours. The mixture was allowed to cool to room temperature, and ethyl acetate (50 mL) was added. The mixture was washed with water and saturated brine, and the solvent was evaporated under reduced pressure. The residue was purified by silica gel column chromatography to give N-Boc-3-iodo-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 3 ) was obtained as a white solid (2.24 g, 46% yield, 3 steps). N-Boc-3-iodo-α-methyl-L-tyrosine ethyl ester (Intermediate A) 1H-NMR (300MHz, CDCl3, TMS): 7.39 (1H, d, J=2.1 Hz), 6.95 (1H, dd, J=2.1, 8.4 Hz), 6.87 (1H, d, J=8.4 Hz), 5.28 (1H, br), 5.19(1H, br), 4.23 (2H, q, J=7.2 Hz), 3.33 (1H, d, J=13.5 Hz), 3.12 (1H, d, J=13.5 Hz), 1.61 (3H, s), 1.49 (9H, s), 1.31 (3H, t, J=7.2Hz) N-Boc-3-iodo-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 3 ) 1 H-NMR (300MHz, CDCl3, TMS): 7.52 (1H, d, J=2.4 Hz), 7.40 (2H, d, J=8.7 Hz), 6.98 (1H, dd, J=2.4, 8.4 Hz), 6.90 (2H, d, J=8.7 Hz), 6.75 (1H, d, J=8.4 Hz), 5.18 (1H, br), 5.04 (2H, s), 4.21 (2H, m), 3.82 (3H, s), 3.32 (1H, d, J=13.5 Hz), 3.11 (1H, d, J=13.5 Hz), 1.58 (3H, s), 1.49 (9H, s), 1.31 (3H, t, J=6.9 Hz)

[0088] c) N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 4 ) Under a nitrogen atmosphere, N-Boc-3-iodo-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 3To a mixture of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) dichloromethane adduct (0.22 g, 0.27 mmol), potassium acetate (1.8 g, 18.3 mmol), and dimethyl sulfoxide (20 mL), bis-pinacolatodiboron (2.32 g, 9.14 mmol) was added and stirred at room temperature for 1 hour, followed by stirring at 55°C for 4 hours. The reaction mixture was allowed to cool to room temperature, and methyl t-butyl ether (60 mL) and half-saturated brine (60 mL) were added. The mixture was filtered through Celite, and the filtrate was separated. The organic layer was further washed with half-saturated brine, 5% aqueous sodium bicarbonate solution, and saturated brine, and evaporated under reduced pressure. The residue was purified by silica gel column chromatography to give N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 4 ) was obtained as a white solid (1.66 g, 64% yield). 1 H-NMR (300MHz, CDCl3, TMS): 7.50 (2H, d, J=8.7 Hz), 7.40 (1H, d, J=2.7 Hz), 7.11(1H, dd, J=2.7, 8.4 Hz), 6.89 (2H, d, J=8.7 Hz), 6.83 (1H, d, J=8.4 Hz), 5.18 (1H, br), 5.02 (2H, s), 4.20 (2H, q, J=7.5 Hz), 3.82 (3H, s), 3.32 (1H, d, J=13.2 Hz), 3.13 (1H, d, J=13.2 Hz), 1.60 (3H, s), 1.48 (9H, s), 1.33 (12H, s), 1.29 (3H, t, J=7.5 Hz)

[0089] d) 3-Borono-α-methyl-L-tyrosine hydrochloride ( 5 ) N-Boc-3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-O-(p-methoxybenzyl)-α-methyl-L-tyrosine ethyl ester ( 4 To a mixture of 3-borono-α-methyl-L-tyrosine hydrochloride (1.3 g, 2.28 mmol), tetrahydrofuran (19.5 mL), and water (6.5 mL), lithium hydroxide monohydrate (0.43 g, 10.2 mmol) was added and stirred at room temperature. The reaction mixture was concentrated under reduced pressure, diluted with water (25 mL), and 0.5 M aqueous sodium hydrogen sulfate solution (30 mL) was added (pH 2-3), followed by extraction with MTBE (30 mL). The extract was washed with water and saturated brine, and the solvent was evaporated under reduced pressure to give a white solid (1.02 g). 4 M hydrochloric acid-ethyl acetate solution was added to the resulting solid, and the mixture was stirred at room temperature for 30 minutes. The solvent was evaporated under reduced pressure, and the residue was washed with ethyl acetate and dried to give crude 3-borono-α-methyl-L-tyrosine hydrochloride ( 5 ) was obtained (0.42 g). This powder (0.40 g) was dissolved in a small amount of H2O and purified using an ODS separation column with a mobile phase gradient of 0.1% HCl aq. / acetonitrile 100 / 0 to 95 / 5. The target fractions were collected and the solvent was distilled off. After dissolving again in 0.1% HCl aq., the product was filtered through a cotton plug. After distilling off the solvent under reduced pressure, the residue was dried under reduced pressure using a vacuum pump to obtain 3-borono-α-methyl-L-tyrosine hydrochloride ( 5 ) was obtained (283 mg, yield 45%). 1 H-NMR (300MHz, DMSO-d6+5% D2O, TMS): 8.42 (1H, s), 7.46 (1H, m, J=2.4 Hz), 7. 00-7.17 (1H, m), 6.72-6.82 (1H, m), 3.06 (1H, d, J=14.1 Hz), 2.95 (1H, d, J=14.1 Hz), 1.47 (3H, s)

[0090] HPLC analysis conditions Sample solution: 3-borono-α-methyl-L-tyrosine hydrochloride ( 5 ) 1 mg was dissolved in 1 mL of 0.1% aqueous HCl to prepare the sample solution. Detector: UV 275 nm Column: YMC-Pack Pro C18 RS (4.6 mmφ×25 cm, 5 μm, YMC) Column temperature: 30℃ Mobile phase: HO (0.1% TFA) / MeCN (0.1% TFA) Mode: Gradient 0 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 95 / 5 5 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 95 / 5 35 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 5 / 95 40 min H2O (0.1%TFA) / MeCN (0.1%TFA) = 5 / 95 Flow rate: 1 mL / min Injection volume: 5 μL Analysis time: 40 minutes Retention time: 3-Borono-α-methyl-L-tyrosine hydrochloride ( 5 ): 11.7 min, 12.2 min (detected as a mixture of boroxine (aggregate) and monomer) The HPLC chart is shown in FIG.

[0091] Reference example 1 211 Preparation of At aqueous solution According to the method described in Reference Example 1 of Patent Document 2, 211 An aqueous solution of At was prepared. 211 At was produced by irradiating bismuth with helium particles (28 MeV) accelerated by a cyclotron. 209 Bi(α,2n) 211 After irradiation, the target material was 209 Bi is heated and melted, 211 At was evaporated and collected in a cold trap, and then dissolved in a small amount of water.

[0092] Example 3 3-Astato( 211Synthesis of (At)-α-methyl-L-tyrosine

[0093] [ka]

[0094] 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride (Bpin-AMT) was dissolved in water to prepare a 0.8 w / v% aqueous solution. This aqueous solution (0.1 mL) was placed in a microtube, and then the same solution prepared in Reference Example 1 was added. 211 At solution (0.02 mL, 5 MBq) and 0.1M KI solution (0.05 mL) were added and reacted at 50°C for 1 hour to give 3-astatin( 211 At)-α-methyl-L-tyrosine ( 211 A crude product solution of At-AAMT was obtained. This crude product solution (1 μL) was analyzed by thin layer chromatography (TLC). The sample was applied to a thin layer plate (silica gel G60), and a mixture of acetonitrile and water (2 / 1) was used as the developing solvent. The thin layer plate was exposed to an imaging plate for approximately 15 minutes and then analyzed using a bioimage analyzer (Typhoon FLT7000, GE Healthcare, Chicago). Figure 3 shows the results of the TLC analysis. 3-Astato( 211 At)-α-Methyl-L-tyrosine was detected at Rf 0.78 with a radiochemical yield (RCY) of 74.9%. The crude product solution was loaded onto an Oasis HLB cartridge (Waters). The target product was captured on the cartridge, and 1 mL of water was passed through to elute impurities. Next, 1 mL of 30% ethanol solution was passed through the cartridge to elute the target product, yielding a purified product. The radiochemical yield of the purified product was 74%, and the radiochemical purity was 94.8%.

[0095] Example 4 3-Astato( 211 Synthesis of (At)-α-methyl-L-tyrosine

[0096] [ka]

[0097] 3-Borono-α-methyl-L-tyrosine hydrochloride (Borono-AMT) was dissolved in water to prepare a 1 w / v% aqueous solution. This aqueous solution (0.1 mL) was placed in a microtube, and then the same solution prepared in Reference Example 1 was added. 211 An aqueous solution of At (0.02 mL, 5 MBq) and a 0.1 M aqueous solution of KI (0.02 mL) were added, and the mixture was reacted at 50°C for 1 hour to obtain 3-astatin ( 211 At)-α-methyl-L-tyrosine ( 211 A crude product solution of At-AAMT was obtained. This crude product solution (1 μL) was analyzed by thin layer chromatography (TLC). The sample was applied to a thin layer plate (silica gel G60) and a mixture of acetonitrile and water (2:1) was used as the developing solvent. The thin layer plate was exposed to an imaging plate for approximately 15 minutes and then analyzed using a bioimage analyzer (Typhoon FLT7000, GE Healthcare, Chicago). Figure 4 shows the results of the TLC analysis. 3-Astato( 211 At)-α-methyl-L-tyrosine was detected at Rf 0.78 with a radiochemical yield (RCY) of 68.2%. The crude product solution was loaded onto an Oasis HLB cartridge, and the target product was captured on the cartridge. 1 mL of water was then passed through the cartridge to elute impurities. Next, 1 mL of 30% ethanol solution was passed through the cartridge to elute the target product, yielding a purified product. The radiochemical yield of the purified product was 58.3%, and the radiochemical purity was 90.9%.

[0098] Example 5 3-Iodine( 131 I) Synthesis of α-methyl-L-tyrosine

[0099] [ka]

[0100] 3-(4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl)-α-methyl-L-tyrosine hydrochloride (Bpin-AMT) was dissolved in water to prepare a 1 w / v% aqueous solution. This solution (0.1 mL) was placed in a microtube and then [ 131 I] Aqueous sodium iodide solution (0.03 mL, 1 MBq, Institute of Isotopes Co., Ltd.) and 0.4 w / v% N-bromosuccinimide (NBS) solution (0.03 mL) were added and the mixture was allowed to react at room temperature for 30 minutes. Next, 3 w / v% ascorbic acid solution (0.03 mL) was added to the reaction mixture to terminate the reaction, and 3-iodo( 131 I)-α-methyl-L-tyrosine ( 131 A crude product solution of I-IAMT) was obtained. This crude product solution (1 μL) was analyzed by thin layer chromatography (TLC). The sample was applied to a thin layer plate (silica gel G60) and a mixture of acetonitrile and water (2:1) was used as the developing solvent. The thin layer plate was exposed to an imaging plate for approximately 15 minutes and then analyzed using a bioimage analyzer (Typhoon FLT7000, GE Healthcare, Chicago). Figure 5 shows the results of the TLC analysis. 3-Iodo( 131 I)-α-Methyl-L-tyrosine was detected at Rf 0.72 with a radiochemical yield (RCY) of 86.1%. This compound was stable for up to 7 days after labeling.

[0101] Reference example 2 3-Astato( 211 Synthesis of (At)-α-methyl-L-tyrosine

[0102] [ka]

[0103] α-Methyl-L-tyrosine (AMT) (22 μmol) and HgSO (20 μmol) were added to an aqueous HSO solution (0.2 M, 0.5 mL) and stirred at room temperature for 2 hours. NaCl (45 μmol) was added to the reaction solution and stirred for 5 minutes. The reaction solution was diluted with the HCl solution prepared in Reference Example 1. 211 An aqueous solution of At (approximately 5 MBq / mL, 100 μL) and 1M KI (5 μL) were added and stirred for 30 minutes. Then, an appropriate amount (100 μL or more) of 1M KI solution was added until the suspension became transparent, and the reaction was terminated. The resulting reaction solution was desalted through a cation column (Dowex™ 50Wx8 100-200 mesh, 0.2M NH3 aqueous solution) and then an anion column (Dowex™ 1x8 50-100 mesh, 2% AcOH aqueous solution) to obtain 3-astatin ( 211 At)-α-methyl-L-tyrosine ( 211 For further stabilization, sodium ascorbate was added to a final concentration of 1 w / v%. The yield was 60-80%.

[0104] Example 6 In this example, 211 We demonstrated that At-AAMT is taken up by cancer cells via the amino acid transporter (LAT1) specifically expressed in cancer cells, and that this ability is superior to that of At-AAMT synthesized by the conventional mercury method. 211 Prove that it is equivalent to At-AAMT. Human pancreatic cancer cells MIA PaCa-2 at 1x10 5 The cells were seeded into a 24-well culture plate at a concentration of 1000 cells / mL. After 2 days, the medium was removed, washed with PBS(-), and replaced with HEPES buffer (amino acid-free). Each well was filled with the cells synthesized by the method of the present invention or the conventional mercury method. 211 At-AAMT was added. Furthermore, BCH (LAT1 inhibitor) or unlabeled AMT was added in excess (1 mM). After culturing the cells for 30 minutes, the cells were washed with PBS(-), lysed with 0.1N NaOH, and the radioactivity of the lysate was measured. The radioactivity was corrected per protein amount to determine the amount of radioactivity in the cells.211 The amount of At-AAMT uptake (radioactivity counts / protein amount) was calculated. The results are shown in Figure 6 (Figure 6a: the method of the present invention, Figure 6b: the conventional mercury method). In Figure 6, CTL is the control, BCH is 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid, and AMT is α-methyltyrosine. 211 At-AAMT was strongly taken up by pancreatic cancer cells (CTL), and uptake was significantly inhibited in the presence of BCH and AMT. 211 The results were consistent with those of At-AAMT. 211 It was confirmed that At-AAMT is specifically taken up by pancreatic cancer cells via LAT1.

[0105] Example 7 In this example, 211 The results demonstrated that At-AAMT has cytotoxicity against cancer cells, and that this ability is comparable to that of the conventional mercury method. 211 Prove that it is equivalent to At-AAMT. 1x10 HEK293 cells 5 The cells were seeded into a 24-well culture plate at a concentration of 1000 cells / mL. After 2 days, the medium was removed, washed with PBS(-), and replaced with HEPES buffer (amino acid-free). Each well was filled with the cells synthesized by the method of the present invention or the conventional mercury method. 211 0.00 to 5.00 kBq of At-AAMT was added. After culturing the cells for 24 hours, the cell viability was examined. The results are shown in Figure 7. 211 The At-AAMT group showed a dose-dependent decrease in cell viability. 211 The results were consistent with those of the At-AAMT group. 211 At-AAMT was shown to have the same cytotoxicity as conventional mercury treatment. [Industrial Applicability]

[0106] According to the present invention, a tyrosine derivative having a boryl group (-B(OH)2) or its ester group introduced therein can be obtained. Using this compound, a highly pure and stable radiolabeled tyrosine derivative can be produced by a safe method suitable for the industrial production of pharmaceuticals without using hazardous substances.

[0107] This application is based on patent application No. 2021-052352 filed in Japan on March 25, 2021, the contents of which are incorporated in full herein.

Claims

1. A method for producing a compound represented by formula (5) or a salt thereof, comprising the following steps 1 to 4: 【Chemistry 1】 [In the formula, R １ represents a methyl group; P １ represents an ether-type hydroxy protecting group; P ２ indicates an amino protecting group; P ３ represents a carboxy protecting group; m represents 0, 1 or 2; X represents a halogen atom; Y is a boryl group (-B(OH) ２ ) or an ester group thereof. Step 1: halogenating a compound represented by formula (1) or a salt thereof to obtain a compound represented by formula (2) or a salt thereof; Step 2: protecting the amino group and carboxy group of the compound represented by formula (2) or a salt thereof and protecting the hydroxy group with an ether-type protecting group to obtain a compound represented by formula (3); Step 3: reacting the compound represented by formula (3) with a boronic acid introducing reagent in the presence of a palladium catalyst and a base to obtain a compound represented by formula (4); Step 4: A step of removing the protecting groups of the carboxy group, amino group, and hydroxy group of the compound represented by formula (4) to obtain a compound represented by formula (5) or a salt thereof.

2. P １ The method according to claim 1, wherein is a benzyl group or a p-methoxybenzyl group.

3. P ３ is a benzyl group or C １－２ The method according to claim 1 or 2, wherein the alkyl group is an alkyl group.

4. P １ and P ３ The method according to claim 1, wherein both are benzyl groups.

5. The method according to any one of claims 1 to 4, wherein the bonding position of the hydroxy group on the benzene ring in formula (5) is the 4-position or the 3-position.

6. The method according to claim 5, wherein the bonding positions of the hydroxy group and Y- on the benzene ring in formula (5) are adjacent to each other.

7. The method according to any one of claims 1 to 4, wherein the hydroxy group in formula (5) is bonded to the 4-position on the benzene ring, and Y- is bonded to the 3-position on the benzene ring.

8. The palladium catalyst in step 3 is [1,1′-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (PdCl ２ (dppf)) according to any one of claims 1 to 7.

9. The method according to claim 8, wherein the reaction in step 3 is carried out in a sulfoxide solvent or an amide solvent.

10. The method according to claim 8, wherein the base in step 3 is an alkali metal acetate.

11. Y is a boryl group (-B(OH) ２ 11. The method according to claim 1, wherein the aryl group is a 4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl group or a 4,4,5,5-tetramethyl-1,3,2-dioxaboran-2-yl group.

12. A method for producing a compound represented by formula (5) or a salt thereof, comprising the following step 4: 【Chemistry 2】 [In the formula, R １ represents a methyl group; P １ represents an ether-type hydroxy protecting group; P ２ indicates an amino protecting group; P ３ represents a carboxy protecting group; m represents 0, 1 or 2; Y is a boryl group (-B(OH) ２ ) or an ester group thereof. Step 4: A step of removing the protecting groups of the carboxy group, amino group, and hydroxy group of the compound represented by formula (4) to obtain a compound represented by formula (5) or a salt thereof.

13. A method for producing a compound represented by formula (4), comprising the following step 3: 【Transformation 3】 [In the formula, R １ represents a methyl group; P １ represents an ether-type hydroxy protecting group; P ２ indicates an amino protecting group; P ３ represents a carboxy protecting group; m represents 0, 1 or 2; X represents a halogen atom; Y is a boryl group (-B(OH) ２ ) or an ester group thereof. Step 3: A step of reacting a compound represented by formula (3) with a boronic acid introducing reagent in the presence of a palladium catalyst and a base to obtain a compound represented by formula (4).

14. A compound represented by the following formula (5a) or a salt thereof: 【Chemistry 4】 [wherein Y is a boryl group (—B(OH) ２ ) or an ester group thereof, and the ester group is 【Transformation 5】 [In the formula, R 2 represents a C 1-6 alkyl group.] is selected from.

15. A compound represented by the following formula (4a): 【Transformation 6】 [In the formula, P １ａ represents a benzyl group or a p-methoxybenzyl group; P ２ａ represents a tert-butoxycarbonyl group; P ３ａ is a benzyl group or C １－２ represents an alkyl group; Y is a boryl group (-B(OH) ２ ) or an ester group thereof, and the ester group is 【Transformation 7】 [In the formula, R 2 represents a C 1-6 alkyl group.] is selected from.

16. A method for producing a radiolabeled compound represented by formula (6) or a salt thereof, comprising the following step 5: 【Transformation 8】 [In the formula, R １ represents a methyl group; m represents 0, 1 or 2; Y is a boryl group (-B(OH) ２ ) or an ester group thereof; Z is ２１１ At, ２１０ At, １２３ I, １２４ I, １２５ I or １３１ I is shown.] Step 5: The compound represented by formula (5) or a salt thereof is reacted in water in the presence of a reagent selected from an alkali metal iodide, an alkali metal bromide, N-bromosuccinimide, N-chlorosuccinimide, N-iodosuccinimide, and hydrogen peroxide, ２１１ At, ２１０ At, １２３ I, １２４ I, １２５ I and １３１ I to obtain a radiolabeled compound of formula (6) or a salt thereof.

17. The method according to claim 16, wherein the compound represented by formula (5) or a salt thereof is produced by the method according to any one of claims 1 to 11.

18. The method according to claim 16 or 17, wherein the reaction is carried out in an organic solvent-free system.

19. The method according to any one of claims 16 to 18, wherein the reaction is carried out in the range of room temperature to 100°C.

20. Radionuclides ２１１ At or １３１ 20. The method according to claim 16, wherein the compound is I and the reagent is selected from potassium iodide and N-bromosuccinimide.

21. The method according to any one of claims 16 to 20, further comprising a step of purifying the radiolabeled compound represented by formula (6) or a salt thereof.

22. The method according to any one of claims 16 to 21, further comprising the step of stabilizing the radiolabeled compound represented by formula (6) or a salt thereof by adding ascorbic acid.

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