JP6218366B2 - Radiolabeled ligand for H3 receptor - Google Patents

Description

  The present invention relates to radioisotope-labeled ligands that specifically bind to the histamine H3 receptor. In particular, the present invention relates to a radioisotope-labeled ligand for use in diagnostic imaging such as positron emission tomography (PET).

  The histamine H3 receptor was cloned in 1999 and its gene sequence and amino acid sequence were elucidated. The amino acid sequence homology with the histamine H1 receptor and histamine H2 receptor was 22% and 21.4%, respectively. Met. The histamine H3 receptor is present in the presynaptic membrane and has been shown to function as an autoreceptor that controls the release of histamine. It was also revealed that the histamine H3 receptor controls the release of histamine and other neurotransmitters such as acetylcholine, serotonin, dopamine, and noradrenaline. These test results indicate the possibility of regulating abnormal neurotransmitter release in various central nervous system diseases by controlling the activity of histamine H3 receptor. In fact, histamine H3 receptor antagonists or inverse agonists may be dementia, Alzheimer's disease, attention deficit / hyperactivity disorder, schizophrenia, epilepsy, central convulsions, obesity, diabetes, hyperlipidemia, narcolepsy, Can be used as a treatment for idiopathic hypersomnia, behavior-induced sleep deprivation syndrome, sleep apnea syndrome, circadian rhythm disorders, sleep-related complications, sleep-related movement disorders, insomnia, depression, allergic rhinitis, etc. There is a report showing the possibility (for example, Non-Patent Document 1, Patent Document 1).

  In recent years, the use of non-invasive imaging techniques for medicine and drug discovery has progressed. In clinical practice, it is used to diagnose diseases such as cancer, measure activity in the heart and brain, and evaluate the rate of binding of development candidates to target proteins. In preclinical practice, it is used to analyze pathological model animals and trace the pharmacokinetics of radioisotope-labeled ligands in experimental animals. In particular, PET is widely used in non-invasive imaging techniques because it is excellent in detecting a very small amount of signal with high sensitivity and has quantitative properties. In order to use this technology, a ligand labeled with a positron emitting nuclide is required, and this ligand has the property of reaching the target organ stably after being administered in vivo and being rapidly excreted from the body. It is preferable.

  A radioisotope-labeled ligand that specifically binds to the histamine H3 receptor is used to non-invasively measure changes in the expression level of the histamine H3 receptor or the distribution of the receptor using diagnostic imaging techniques such as PET. Useful. In addition, after administration of unlabeled histamine H3 receptor ligand, administration of a trace amount of radioisotope-labeled ligand and evaluation by PET enables binding of unlabeled histamine H3 receptor ligand to histamine H3 receptor. Indirect quantification is possible, which is useful for setting a human dose. Many radioisotope-labeled ligands for histamine H3 receptors have been synthesized so far, but they are stable without being metabolized after in vivo administration, and are sufficient for target organs (eg, brain). There are few ligands that have favorable characteristics for diagnostic imaging such as PET (see Patent Document 2 and Non-Patent Documents 2 to 3), and that are more useful images. There is a need for the creation of diagnostic ligands.

International Publication No. WO2010 / 090347 Pamphlet International Publication No. WO2006 / 072596 Pamphlet

Biol. Pharm. Bull. 31 (12) 2163-2181 (2008) Synapse 63: 1122-1132, 2009 J. Nucl. Med. 51: 1021-1029, 2010

  An object of the present invention is to provide a novel radioisotope-labeled ligand that specifically binds to the histamine H3 receptor. Furthermore, it is stable without being metabolized after being administered in vivo, and a sufficient amount specifically accumulates in the target organ (eg, brain) and is rapidly excreted from within the body. It is another object of the present invention to provide a radioisotope-labeled ligand having favorable characteristics.

  As a result of diligent search research, the present inventors have found that a radioisotope-labeled compound of the following formula is an excellent radioisotope-labeled ligand capable of solving the above-mentioned problems, and completed the present invention. did.

That is, this invention is the following aspect.
(1) A compound represented by the following general formula (I) or a pharmaceutically acceptable salt thereof (hereinafter sometimes referred to as “the compound of the present invention”).

(In the above general formula (I),
X represents CH or N;
R ¹ is a C ₁ -C ₆ alkyl group which may be substituted with ¹ to 3 halogen atoms,
Here, R ¹ is labeled with one radioisotope selected from the group consisting of ³ H, ¹¹ C, ¹⁸ F, ¹²³ I, ¹²⁵ I, ¹³¹ I, ⁷⁵ Br, ⁷⁶ Br, and ⁸² Br. )
(2) The compound according to (1) or a pharmaceutically acceptable salt thereof, wherein R ¹ is a methyl group labeled with ¹¹ C.
(3) A histamine H3 receptor labeled ligand containing the compound according to (1) or (2) or a pharmaceutically acceptable salt thereof,
(4) A histamine H3 receptor-labeled ligand for positron tomography containing the compound according to (1) or (2) or a pharmaceutically acceptable salt thereof, or (5) (1) or (2 ) Or a pharmaceutically acceptable salt thereof, or a diagnostic agent for a disease associated with histamine H3 receptor.

  The compound of the present invention was stable without being metabolized after being administered in vivo, and a sufficient amount of transfer to the brain as the target organ was observed. In addition, as a result of diagnostic imaging using PET, it was revealed that the compound of the present invention specifically accumulates in the frontal cortex, striatum, etc., which are sites where histamine H3 receptors are highly expressed in the brain. It was.

The 90-minute addition average PET image (horizontal sectional view) superimposed on the nuclear magnetic resonance image is shown. (a) Rat labeled with radiolabeled compound A, (b) Rat subjected to blocking test with cold compound A, (c) Rat administered with radiolabeled compound C, (d) Rat subjected to blocking test with cold compound C

In the present invention, the “C ₁ -C ₆ alkyl group” means a linear or branched alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group. A group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group or n-hexyl group;

  In the present invention, the “halogen atom” is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom.

Since the compound of the present invention can specifically bind to the histamine H3 receptor, various diagnostic methods described below are used as ligands for labeling the histamine H3 receptor ("histamine H3 receptor labeled ligand"). Etc. can be used.
In one embodiment of the present invention, a compound represented by the general formula (I) or a pharmaceutically acceptable salt thereof is used for diagnostic imaging using a histamine H3 receptor, particularly a histamine H3 receptor in the brain. Can be done. Specifically, an effective amount of the compound of the present invention is administered to animals by intravenous injection or inhalation.
In another embodiment of the present invention, a compound represented by the general formula (I) or a pharmaceutically acceptable salt thereof is used to detect or quantify the function of a histamine H3 receptor in an animal. it can. This method is useful for diagnosing various diseases caused by changes in the function of the histamine H3 receptor.
In another embodiment of the present invention, the compound represented by the general formula (I) or a pharmaceutically acceptable salt thereof is useful for diagnostic imaging using tissues in which histamine H3 receptor is expressed in animals. Can be used. Here, the tissue in which the histamine H3 receptor is expressed includes, for example, a brain slice section. This method is useful for pre-clinical analysis of pathological model animals and tracing of pharmacokinetics of radioisotope-labeled ligands in experimental animals.
Furthermore, the compound of the present invention can evaluate the action of histamine H3 receptor modulators (H3 receptor agonists, antagonists, inverse agonists, etc.) in diseases related to histamine H3 receptors. Specifically, as a tracer compound (histamine H3 receptor labeling agent) for evaluating the degree of histamine H3 receptor occupancy in the brain in clinical evaluation of histamine H3 receptor modulator candidate drugs Is available. It is also useful for estimating the effective amount of a histamine H3 receptor antagonist or inverse agonist when used as a therapeutic agent for various diseases.
Specifically, after an unlabeled histamine H3 receptor modulator or candidate drug is administered to an animal, an effective amount of the compound of the present invention is administered and evaluated using an imaging technique such as PET, The binding of an unlabeled histamine H3 receptor modulator or candidate drug to the histamine H3 receptor can be indirectly quantified.

In the present invention, the “animal” is preferably a human unless otherwise specified.
The radionuclide used in the compound of the present invention is ³ H, ¹¹ C, ¹⁸ F, ¹²³ I, ¹²⁵ I, ¹³¹ I, ⁷⁵ Br, ⁷⁶ Br or ⁸² Br. Preferred nuclides for use in histamine H3 receptor labeling in vitro include ³ H, ¹²⁵ I and the like. Preferred nuclides for use in diagnostic imaging are ¹¹ C, ¹⁸ F, ¹²³ I, ⁷⁶ Br, and the like. As a method for image diagnosis, positron emission tomography (PET), single photon emission tomography (SPECT), or the like can be used, but PET is preferable in terms of sensitivity.

  “Disease related to histamine H3 receptor” includes dementia, Alzheimer's disease, attention deficit / hyperactivity disorder, schizophrenia, epilepsy, central convulsions, obesity, diabetes, hyperlipidemia, narcolepsy, idiopathic Examples include hypersomnia, behavior-induced sleep deprivation syndrome, sleep apnea syndrome, circadian rhythm disorder, sleep-related comorbidities, sleep-related movement disorders, insomnia, depression, and allergic rhinitis. Inverse or selective antagonism of the histamine H3 receptor increases the concentration of histamine and other monoamines in the brain, inhibiting activities such as food consumption and minimizing nonspecific peripheral results To do. Through this mechanism, reverse activation or selective antagonism of the histamine H3 receptor results in prolonged arousal, improved cognitive function, decreased food intake, and normalization of the vestibular reflex. Therefore, the inverse agonist or selective antagonist of the histamine H3 receptor is effective for the treatment of the diseases related to the histamine H3 receptor.

This invention compound (I) and its pharmaceutically acceptable salt can be manufactured by the method shown by following Reaction Formula, using the compound manufactured similarly to the method of patent document 1. FIG.
[Production method]
Compound (I) of the present invention can be produced by a known organic chemical method, for example, according to the method according to the following schemes 1 and 2. In the following schemes ¹ and 2, R ¹ and X are as defined above. R ² represents a hydrogen atom or a group generally used as a hydroxyl group or a protecting group for phenol (for example, acetyl, benzoyl, methyl, tert-butyl, benzyl, benzyloxycarbonyl, tert-butoxycarbonyl, methoxymethyl). Y ¹ , Y ² , Y ³ and Y ⁴ are the same or different and are a halogen atom such as a chlorine atom, a bromine atom or an iodine atom or a methanesulfonyl group, such as tetrahydropyranyl or tert-butyldimethylsilyl. A leaving group such as an organic sulfonyloxy group such as an oxy group, a phenylsulfonyloxy group, a p-toluenesulfonyloxy group, and a trifluoromethanesulfonyloxy group.
Scheme 1

Step 1: Step 1 is a step for obtaining compound (3) by condensing known compound (1) and compound (2) by a cross-coupling reaction. Compound (2) is a known compound or a compound that can be easily synthesized from a known compound. The cross-coupling reaction can be performed by a general method in which a reaction is performed in a solvent in the presence of a catalyst and its ligand. For example, as described in (Kunz et al., Synlett, 2003, Vol. 15, pages 2428-2439). It can implement according to the method or the method according to it. In addition, this reaction is preferably performed in the presence of a base. Examples of the catalyst used in this reaction include transition metal catalysts generally used for cross-coupling reactions such as copper, nickel and palladium, and more specifically, copper (0), copper (I) iodide. , Copper (I) chloride, copper (I) oxide, copper (I) tristriphenylphosphine complex, copper (I) trifluoromethanesulfonate, benzene complex, palladium (II) acetate, tetrakis (triphenylphosphine) palladium ( 0), bis (triphenylphosphine) palladium (II) chloride, [1,1′-bis (diphenylphosphino) ferrocene] palladium (II) dichloride, tris (dibenzylideneacetone) dipalladium (0), bis (acetyl Acetonato) nickel (II) and the like. Examples of the ligand used in this reaction include ligands commonly used in condensation reactions using metal catalysts, such as N, N′-dimethylethylenediamine, N, N′-dimethylcyclohexane-1,2-diamine, and 2-amino. Examples include pyridine, 1,10-phenanthroline, 2-hydroxybenzaldehyde oxime, ethylene glycol, triphenylphosphine, and tri-tert-butylphosphine. Examples of the base used in this reaction include potassium carbonate, potassium phosphate, potassium hydroxide, tert-butoxy potassium, tert-butoxy sodium, cesium carbonate, sodium carbonate, sodium hydrogen carbonate, sodium acetate, sodium methoxide, tetra Examples include butylammonium hydroxide. Examples of the solvent used in this reaction include alcohols such as methanol, ethanol and isopropanol; ethers such as tetrahydrofuran, 1,2-dimethoxyethane and 1,4-dioxane; hydrocarbons such as toluene and benzene; chloroform Halogenated hydrocarbons such as dichloromethane, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone; ketones such as acetone and 2-butanone; dimethyl sulfoxide; acetonitrile Water or a mixed solvent thereof may be mentioned.

Step 2: Step 2 is a step for obtaining compound (4) by deprotection when R ² of compound (3) is a group generally used as a hydroxyl group or a protecting group for phenol. The deprotection reaction is a general deprotection reaction according to the type of protecting group, for example, (Protective Groups in Organic Synthesis by TW Greene and PGM Wuts, 3rd edition, John Wiley and Sons. The method described in the above) or a method analogous thereto.

Process 3: Process 3 is a process for obtaining the compound (I) of this invention by coupling reaction of a compound (4) and a compound (5). The coupling reaction can be carried out by a general method in which O-alkylation of phenol or pyridone is performed in the presence of a base or in the absence of a solvent. Moreover, additives, such as potassium iodide and sodium bromide, can be added as needed. Examples of the base used in this reaction include pyridine, triethylamine, diisopropylethylamine, tert-butoxypotassium, potassium carbonate, cesium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium hydroxide, sodium hydride and the like. Examples of the solvent used in this reaction include alcohols such as methanol, ethanol and isopropanol; ethers such as tetrahydrofuran, 1,2-dimethoxyethane and 1,4-dioxane; hydrocarbons such as toluene and benzene; chloroform Halogenated hydrocarbons such as dichloromethane, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone; ketones such as acetone and 2-butanone; dimethyl sulfoxide; acetonitrile Water or a mixed solvent thereof may be mentioned. Compound (5) is a labeling reagent used for the synthesis of labeled radiopharmaceuticals, and can be produced in a general facility capable of synthesizing radiopharmaceuticals. "

Scheme 2

Step 4: Step 4 is a step for obtaining compound (7) by condensing known compound (1) and compound (6) by a cross-coupling reaction as in step 1. Compound (6) is a known compound or a compound that can be easily synthesized from a known compound. The cross coupling reaction can be carried out by the same method as in Step 4.

Step 5: Step 5 is a step for condensing compound (7) and compound (8) by a coupling reaction to obtain compound (I-2) of the present invention. The coupling reaction can be performed by a general method in which an alkoxy group is added to the 2-position of 2-halopyridine in the presence or absence of a base in a solvent or without a solvent. Moreover, additives, such as potassium iodide and sodium bromide, can be added as needed. Examples of the base used in this reaction include organic bases such as pyridine, triethylamine, diisopropylethylamine, sodium methoxide; tert-butoxy potassium, potassium carbonate, cesium carbonate, sodium hydrogen carbonate, sodium hydroxide, potassium hydroxide, And inorganic bases such as sodium hydride. Examples of the solvent used in this reaction include alcohols such as methanol, ethanol and isopropanol; ethers such as tetrahydrofuran, 1,2-dimethoxyethane and 1,4-dioxane; hydrocarbons such as toluene and benzene; chloroform Halogenated hydrocarbons such as dichloromethane, amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone; ketones such as acetone and 2-butanone; dimethyl sulfoxide; acetonitrile Water or a mixed solvent thereof may be mentioned. Compound (8) is a labeling reagent used for the synthesis of labeled radiopharmaceuticals, and can be produced in a general facility capable of synthesizing radiopharmaceuticals. "

  Hereinafter, the present invention will be described in more detail with reference to Examples and Test Examples.

  The present invention will be described in more detail with reference to the following examples and test examples. However, these examples and test examples do not limit the present invention, and may be changed without departing from the scope of the present invention. Good.

Each instrument data described in the examples was measured with the following measuring instruments.
MS spectrum: Agilent 6150 / Agilent 1290 Infinity
NMR spectrum: [ ¹ H-NMR] JNM-ECA600 (JEOL)

Abbreviations used in the examples are shown below.
MS (mass spectrometry), APCI (atmospheric pressure chemical ionization), ESI (electrospray ionization).

Example 1
6 - [(l-cyclobutyl-yl) oxy] -1- (6- ¹¹ C- methoxypyridin-3-yl) -3,4-dihydro-quinolin -2 (IH) - one (Compound A) Synthesis of

Step 1-1:
Synthesis of 6-[(1-cyclobutylpiperidin-4-yl) oxy] -1- (6-hydroxypyridin-3-yl) -3,4-dihydroquinolin-2 (1H) -one (Precursor B)

6-[(1-Cyclobutylpiperidin-4-yl) oxy] -1- (6-methoxypyridin-3-yl) -3,4-dihydroquinolin-2 (1H) -one (0.8 g) (WO2010) 2N Hydrochloric acid ethanol solution (5 mL) is added to an ethanol (2 mL) solution of the Example Compound (Compound No. 67) of / 090347 International Publication, which can be synthesized according to the method described in the same publication, and 100 ° C. in a sealed tube For 16 hours. The reaction mixture was concentrated under reduced pressure, and the residue was purified by NH silica gel column chromatography (developing solvent: chloroform / methanol = 9/1) and recrystallized from methanol-water to give the title compound (0. 58 g) was obtained.
¹ H NMR (600 MHz, CHLOROFORM-d) δ ppm ppm 1.46-2.22 (m, 12 H) 2.60 (br. S., 2 H) 2.68-2.80 (m, 3 H) 2.92-3.05 (m, 2 H ) 4.23 (br. S., 1 H) 6.48 (d, J = 9.08 Hz, 1 H) 6.62-6.69 (m, 2 H) 6.76 (d, J = 2.89 Hz, 1 H) 7.29 (dd, J = 9.50, 2.89 Hz, 1 H) 7.36 (d, J = 2.48 Hz, 1 H)
MS (ESI / APCI Dual) (Positive) m / z; 394 (M + H) ⁺

Step 1-2-1
6 - [(l-cyclobutyl-yl) oxy] -1- (6- ¹¹ C- methoxypyridin-3-yl) -3,4-dihydro-quinolin -2 (IH) - one (Compound A) Synthesis (Method 1)

Compound A was synthesized by alkylating the oxygen atom of the 2-pyridone moiety of precursor B with [ ¹¹ C] methyl iodide produced by a cyclotron apparatus.
Carbon-11 was produced by irradiating with nitrogen at 20 μA for 15 minutes according to the ¹⁴ N (P, α) ¹¹ C reaction using 18.0 MeV protons. Carbon-11 was converted to [ ¹¹ C] carbon dioxide by the presence of a small amount of oxygen (5 ppm) in the target gas. The obtained [ ¹¹ C] carbon dioxide was reduced using lithium aluminum hydride, and subsequently reacted with hydroiodic acid to synthesize [ ¹¹ C] methyl iodide.
Ultrasonic was applied to a mixture of Precursor B (1.0 mg), cesium carbonate (ca. 8 mg) and anhydrous N, N-dimethylformamide (300 uL) for dispersion for 1 minute. The reaction mixture was cooled to −20 ° C., blown with [ ¹¹ C] methyl iodide and then heated at 100 ° C. for 3 minutes. Acetonitrile / 50 mM phosphoric acid (23/77) solution (1 mL) is added to the reaction mixture, which is injected into a preparative HPLC column (SunFire ^™ C-18 250 × 10 mm) and acetonitrile / 50 mM phosphoric acid at a flow rate of 4 mL / min. Elution with (23/77) solution. The radioactive fraction containing Compound A eluted after 7-8 minutes and collected in a round bottom flask was evaporated to dryness by heating to 100 ° C. with an air heater under reduced pressure. The residue was dissolved in 3.5% aqueous sodium dihydrogen phosphate (3 mL) and collected in a sterile vial. Quality control was performed using analytical HPLC (SunFire ^™ C-18 250 × 4.6 mm) at a flow rate of 1 mL / min with acetonitrile / 50 mM phosphoric acid (21/79) solution as the mobile phase.
By this production, a compound A having a quantity of 280 MBq to 400 MBq, a radiochemical purity of 98.5% or more and a specific activity of 85 to 110 GBq / μmol was obtained. The average total synthesis time including HPLC purification and formulation was about 32 minutes from the end of irradiation.

Step 1-2-2:
6 - [(l-cyclobutyl-yl) oxy] -1- (6- ¹¹ C- methoxypyridin-3-yl) -3,4-dihydro-quinolin -2 (IH) - one (Compound A) (Method 2)

Compound A was synthesized by alkylating the oxygen atom of the 2-pyridone moiety of precursor B using [ ¹¹ C] methyl triflate produced by a cyclotron apparatus.
Carbon-11 was produced by irradiating nitrogen with a beam current of 20 μA for 10 minutes according to the ¹⁴ N (P, α) ¹¹ C reaction using 18.0 MeV protons. Carbon-11 was converted to [ ¹¹ C] carbon dioxide by the presence of a small amount of oxygen (5 ppm) in the target gas. The obtained [ ¹¹ C] carbon dioxide was reduced using lithium aluminum hydride, and subsequently reacted with hydroiodic acid to synthesize [ ¹¹ C] methyl iodide. The obtained [ ¹¹ C] methyl iodide vapor was passed through a column packed with graphitized carbon infiltrated with trifluoromethanesulfonate heated to 150 to 200 ° C. to synthesize [ ¹¹ C] methyl triflate.
A mixture of Precursor B (0.8 mg), cesium carbonate (ca. 8 mg) and anhydrous N, N-dimethylformamide (300 uL) was heated to 100 ° C. and blown with [ ¹¹ C] methyl triflate, then kept at 100 ° C. 3 Heated for minutes. Acetonitrile / 50 mM phosphoric acid (23/77) solution (1 mL) is added to the reaction mixture, which is injected into a preparative HPLC column (SunFire ^™ C-18 250 × 10 mm) and acetonitrile / 50 mM phosphoric acid at a flow rate of 4 mL / min. Elution with (23/77) solution. The radioactive fraction containing Compound A eluted after 7-8 minutes and collected in a round bottom flask was evaporated to dryness by heating to 100 ° C. with an air heater under reduced pressure. The residue was dissolved in 3.5% aqueous sodium dihydrogen phosphate (10 mL) and collected in a sterile vial. Quality control was performed using analytical HPLC (SunFire ^™ C-18 250 × 4.6 mm) at a flow rate of 1 mL / min with acetonitrile / 50 mM phosphoric acid (21/79) solution as the mobile phase.
By this production, Compound A having a quantity of 444 MBq to 960 MBq, a radiochemical purity of 98.5% or more and a specific activity of 98 to 105 GBq / μmol was obtained. The average total synthesis time including HPLC purification and formulation was about 35 minutes from the end of irradiation.

(Example 2)
6 - [(1-cyclobutyl piperidin-4-yl) oxy] -1- (4- ¹¹ C- methoxyphenyl) -3,4-dihydro-quinolin -2 (IH) - one Synthesis of (Compound C)

Step 2-1
Synthesis of 1- {4-[(tert-butyldimethylsilyl) oxy] phenyl} -6-[(1-cyclobutylpiperidin-4-yl) oxy] -3,4-dihydroquinolin-2 (1H) -one

6- (1-cyclobutylpiperidin-4-yloxy) -3,4-dihydroquinolin-2 (1H) -one (synthesized according to the method described in WO2010 / 090347 International Publication) (1 g), (4-bromo Phenoxy) (tert-butyl) dimethylsilane (1.05 g), N, N′-dimethylethylenediamine (0.235 g), copper iodide (0.127 g) and potassium carbonate (0.92 g) in toluene (5 mL) The turbid solution was stirred in a sealed tube at 110 ° C. for 4 hours. The reaction mixture was allowed to cool to room temperature, saturated aqueous ammonium chloride solution was added, and the mixture was extracted with chloroform. The organic layer was concentrated under reduced pressure, and the resulting residue was purified by NH-type silica gel column chromatography (developing solvent: hexane / ethyl acetate = 88/12 to 0/100) to give a pale yellow amorphous title compound ( 0.94 g) was obtained.
¹ H NMR (600 MHz, CHLOROFORM-d) δppm 0.23 (s, 6 H) 0.91-1.06 (m, 9 H) 1.60-2.21 (m, 12 H) 2.48-2.65 (m, 2 H) 2.67-2.82 ( m, 3 H) 2.93-3.02 (m, 2 H) 4.15-4.25 (m, 1 H) 6.26 (d, J = 9.08 Hz, 1 H) 6.56 (dd, J = 8.88, 2.68 Hz, 1 H) 6.74 (d, J = 2.48 Hz, 1 H) 6.84-6.94 (m, 2 H) 7.03-7.11 (m, 2 H)
MS (ESI / APCI Dual) (Positive) m / z; 507 (M + H) ⁺

Step 2-2:
Synthesis of 6-[(1-cyclobutylpiperidin-4-yl) oxy] -1- (4-hydroxyphenyl) -3,4-dihydroquinolin-2 (1H) -one (Precursor D)

1- {4-[(tert-Butyldimethylsilyl) oxy] phenyl} -6-[(1-cyclobutylpiperidin-4-yl) oxy] -3,4-dihydroquinoline-2 synthesized in Step 2-1. To a solution of (1H) -one (0.94 g) in tetrahydrofuran (4 mL) was added 1N tetrabutylammonium fluoride tetrahydrofuran solution (2.78 mL) in an ice bath, and the mixture was stirred for 16 hours while warming to room temperature. The reaction mixture is concentrated under reduced pressure, and the residue is purified by NH-type silica gel column chromatography (developing solvent: hexane / ethyl acetate = 88 / 12-0 / 100) and recrystallized from ethanol to give the title compound as a colorless powder. (0.28 g) was obtained.
¹ H NMR (600 MHz, CHLOROFORM-d) δppm 1.51-2.12 (m, 12 H) 2.44-2.57 (m, 2 H) 2.60-2.75 (m, 3 H) 2.86-2.98 (m, 2 H) 4.07- 4.19 (m, 1 H) 6.22 (d, J = 8.67 Hz, 1 H) 6.49 (dd, J = 8.88, 2.68 Hz, 1 H) 6.67 (d, J = 2.89 Hz, 1 H) 6.73-6.79 (m , 2 H) 6.89-6.97 (m, 2 H)
MS (ESI / APCI Dual) (Positive) m / z; 393 (M + H) ⁺

Step 2-3:
6 - [(1-cyclobutyl piperidin-4-yl) oxy] -1- (4- ¹¹ C- methoxyphenyl) -3,4-dihydro-quinolin -2 (IH) - one Synthesis of (Compound C)

Compound C was synthesized by alkylating the hydroxy group of precursor D with [ ¹¹ C] methyl iodide produced by a cyclotron apparatus. At the time of manufacture, irradiation was performed for 15 minutes using a beam current of 20 μA.
A mixture of Precursor D (0.7 mg) and anhydrous N, N-dimethylformamide (300 uL) was placed in a 3 mL glass vial to make a solution, and 1 mol / L aqueous sodium hydroxide solution (10 μL) was added. The reaction mixture was cooled to −20 ° C., blown with [ ¹¹ C] methyl iodide and then heated at 100 ° C. for 3 minutes. Acetonitrile / 50 mM phosphoric acid (23/77) solution (1 mL) is added to the reaction mixture, which is injected into a preparative HPLC column (SunFire ^™ C-18 250 × 10 mm) and acetonitrile / 50 mM phosphoric acid at a flow rate of 4 mL / min. Elution with (23/77) solution. The radioactive fraction containing Compound C eluted after 10-13 minutes and collected in a round bottom flask was evaporated to dryness by heating to 100 ° C. with an air heater under reduced pressure. The residue was dissolved in 3.5% aqueous sodium dihydrogen phosphate (3 mL) and collected in a sterile vial. Quality control was performed using analytical HPLC (SunFire ^™ C-18 250 × 4.6 mm) at a flow rate of 1 mL / min with acetonitrile / 50 mM phosphoric acid (23/77) solution as the mobile phase.
By this production, a compound C having a quantity of 603 MBq to 1440 MBq, a radiochemical purity of 98.9% or more and a specific activity of 98 to 110 GBq / μmol was obtained. The average total synthesis time, including HPLC purification and formulation, was about 34 minutes from the end of irradiation.

<Test example>
PET imaging
Method
Rats (Sprague-Dawley, male) were used for PET imaging. Rats were anesthetized with isoflurane (1 to 1.5% v / v), and an indwelling needle for administration of radiolabeled compound and drug solution was placed in the tail vein. For PET imaging, microPET Focus 220 (Siemens) was used, and a rat under isoflurane anesthesia was fixed to the same device in a measuring posture. The animals maintained their body temperature on a 37 ° C. heat retention mat.
Radiolabeled compound A of Example 1 (129 MBq, specific activity 111 GBq / mmol) was administered from the tail vein, and PET imaging was performed for 90 minutes immediately after administration. Imaging was performed in list mode, and image reconstruction was performed using a 0.5 mm Hanning filter. The obtained PET image data was constructed using a PMOD software (PMOD Technology) to construct a three-dimensional map of the distribution of radiolabeled compounds and the region of interest (ROI) set in the frontal cortex, striatum, and cerebellum. It was used to analyze the time change of radioactivity concentration. The radioactive concentration at each ROI was corrected for attenuation based on the time of administration of the radiolabeled compound, and was also corrected with the dose of radiolabeled compound to the animal (notation unit:% injected dose (ID) / ml) ).
In order to confirm the binding specificity of the radiolabeled compound to the H3 receptor, cold body compound A is pre-administered (1 mg / kg, administered from the tail vein), and radiolabeled compound A is administered immediately thereafter. PET imaging was performed for 90 minutes immediately after administration (Blocking test)
Further, the test was performed using the radiolabeled compound C of Example 2 (191 MBq, specific activity 110 GBq / mmol) under the same conditions as described above. The Blocking test was performed in the same manner as described above with pre-administration of cold body compound C (1 mg / kg, administered from the tail vein).

Test results An increase in radioactivity concentration was confirmed in the frontal cortex, striatum, and cerebellum immediately after administration of radiolabeled compound A. The uptake of the radiolabeled compound into the frontal cortex reached a peak 9 minutes after administration, and the peak value of the uptake amount was 0.56% ID / ml. In the cerebellum where H3 receptor expression was very low, the radioactivity concentration decreased rapidly, but in the frontal cortex and striatum where H3 receptor was expressed, the decrease in radioactivity concentration was slower than in the cerebellum.
In the blocking test using cold body compound A, there was no difference in the time course of radiolabeled compound uptake in the frontal cortex, striatum, and cerebellum. For this reason, it was confirmed that radiolabeled compound A specifically binds to the H3 receptor in the frontal cortex and striatum.
The result of radiolabeled compound C was the same as that of compound A, and the uptake of the radiolabeled compound into the frontal cortex reached a peak 11 minutes after administration, and the peak value of the uptake was 0.50% ID / ml. In the blocking test using cold compound C, the same results as in compound A were confirmed.
FIG. 1 shows a 90-minute addition average PET image (horizontal sectional view) superimposed on a nuclear magnetic resonance image. ((A) Rat labeled with radiolabeled compound A, (b) Rat tested with cold compound A, (c) Rat administered with radiolabeled compound C, (d) Rat tested with cold compound C)

  The present invention is useful for diagnosing various diseases caused by functional changes of the histamine H3 receptor using image diagnostic techniques such as PET. In addition, when using a histamine H3 receptor antagonist or inverse agonist as a therapeutic agent for various diseases, it is also useful for estimating the effective amount using an imaging technique such as PET.

Claims (5)

A compound represented by the following general formula (I) or a pharmaceutically acceptable salt thereof.
(In the above general formula (I),
X represents CH or N;
R ¹ is a methyl group labeled with ¹¹ C. ) 6 - [(1-cyclobutyl piperidin-4-yl) oxy] -1- (6- ¹¹ C- methoxypyridin-3-yl) -3,4-dihydro-quinolin -2 (IH) - one,
6 - [(l-cyclobutyl-yl) oxy] -1- (4- ¹¹ C- methoxyphenyl) -3,4-dihydro-quinolin -2 (IH) - one, or their pharmaceutically Acceptable salt . A histamine H3 receptor labeled ligand comprising the compound according to claim 1 or 2 or a pharmaceutically acceptable salt thereof. A histamine H3 receptor labeled ligand for positron tomography, comprising the compound according to claim 1 or 2 or a pharmaceutically acceptable salt thereof. A diagnostic agent for a disease associated with the histamine H3 receptor, comprising the compound according to claim 1 or 2 or a pharmaceutically acceptable salt thereof.