[18F]-LABELED IMIDAZOPYRIDINE DERIVATIVES AS PET RADIOTRACER

Abstract

The present disclosure relates to [.sup.18F]-labeled imidazopyridine derivatives or salts thereof as positron emission tomography (PET) radiotracers suitable for imaging the stress-signaling non-receptor tyrosine kinase c-abl, and their use in in vivo diagnosis, preclinical and clinical imaging, patient stratification on the basis of mutational status of c-abl and assessing response to therapeutic treatments. The present disclosure furtherrelates to the use of [.sup.18F]-labeled imidazopyridine derivatives as PET radiotracers. Thedis-closure also provides a process for the radiosynthesis of [.sup.18F]-labeled imidazopyridinederivatives.

Claims

1. A compound of Formula (I), or pharmaceutically acceptable salt thereof: ##STR00009## wherein R.sub.1 is —CH.sub.2CH.sub.2.sup.18F or —OCH.sub.2CH.sub.2.sup.18F when R.sub.2 is —H, or R.sub.1 is —CH.sub.2CH.sub.2.sup.18F or —OCH.sub.2CH.sub.2.sup.18F when R.sub.2 is —F.

2. The compound of claim 1, which is the compound of Formula (IIA) or a pharmaceutically acceptable salt thereof: ##STR00010## wherein R.sub.2 is —H or —F.

3. The compound of claim 1, which is the compound of formula (IIB) or a pharmaceutically acceptable salt thereof: ##STR00011## wherein R.sub.2 is —H or —F.

4. The compound of claim 1 or a pharmaceutically acceptable salt thereof, which is selected from the group consisting of: (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-(fluoro-.sup.18F)ethoxy)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide; (1S,2S)-2-fluoro-N-(6-(2-(2-(fluoro-.sup.18F)ethoxy)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide; (1S,2S)-2-fluoro-N-(6-(2-(2-(fluoro-.sup.18F)ethyl)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide; and (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-(fluoro-.sup.18F)ethyl)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide.

5. A pharmaceutical composition comprising a therapeutically effective amount of the compound of claim 1 or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

6. A method for treating a neurodegenerative disease comprising: administering to a subject in need thereof a therapeutically effective amount of the compound of claim 1 or a pharmaceutically acceptable salt thereof.

7. The method of claim 6, wherein the neurodegenerative disease is selected from the group consisting of α-synucleinopathy, Parkinson’s disease, dementia with Lewy body, multiple system atrophy (MSA), Alzheimer’s disease, and amyotrophic lateral sclerosis (ALS).

8. A method of determining an enzyme inhibitory activity, the method comprising: applying the compound of claim 1 to a biological sample; and imaging the compound to determine the enzyme inhibitory activity.

9. The method of claim 8, wherein the compound is used as a positron emission tomography (PET) tracer.

10. The method of claim 8, which is a PET imaging method.

11. The method of claim 8, wherein the method is used in an AD-induced mouse AD model or an alpha-synuclein PFF-induced mouse PD model.

12. The method of claim 8, wherein the method is used to determine c-abl upregulation or activation in a brain.

13. The method of claim 8, wherein the method is for companion diagnosis for c-abl therapy or other disease-modifying agents as a predictive biomarker.

14. The method of claim 8, wherein the method is used for a patient with a neurodegenerative disease.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is HPLC chromatogram of Example 1 (RT=9.504 min), UV at 254 nm using HPLC method 1.

[0016] FIG. 2 is HPLC chromatogram of the precursor, Compound 5 (RT=29.876 min), UV at 254 nm using HPLC method 1.

[0017] FIG. 3 is HPLC chromatogram of the diastereomer A of Example 1 (RT=11.690 min), UV at 254 nm using HPLC method 1.

[0018] FIG. 4 is HPLC chromatogram of the diastereomer B of Example 1 (RT=11.684 min), UV at 254 nm using HPLC method 1.

[0019] FIG. 5 is HPLC chromatogram of formulated [.sup.18F] Example 1 (RT=9.633 min), using HPLC method 1.

[0020] FIG. 6 is HPLC chromatogram of Example 3 (RT=8.987 min), UV at 254 nm using HPLC method 1.

[0021] FIG. 7 is HPLC chromatogram of the precursor, Compound 8 (RT=27.502 min), UV at 254 nm using HPLC method 1.

[0022] FIG. 8 is HPLC chromatogram of the diastereomer A of Example 3 (RT=10.988 min), UV at 254 nm using HPLC method 1.

[0023] FIG. 9 is HPLC chromatogram of the diastereomer B of Example 3 (RT=10.993 min), UV at 254 nm using HPLC method 1.

[0024] FIG. 10 is HPLC chromatogram of formulated [.sup.18F] Example 3 (RT=9.199 min), using HPLC method 1.

[0025] FIG. 11 is HPLC chromatogram of Example 1 (RT=10.710 min), UV at 254 nm using HPLC method 2.

[0026] FIG. 12 is HPLC chromatogram of the precursor, Compound 5 (RT=12.392 min), UV at 254 nm using HPLC method 2.

[0027] FIG. 13 is HPLC chromatogram of diastereomer A of Example 1 (RT=11.114 min), UV at 254 nm using HPLC method 2.

[0028] FIG. 14 is HPLC chromatogram of diastereomer B of Example 1 (RT= 11.116 min), UV at 254 nm using HPLC method 2.

[0029] FIG. 15 is HPLC chromatogram of Example 3 (RT=10.637 min), UV at 254 nm using HPLC method 2.

[0030] FIG. 16 is HPLC chromatogram of the precursor, Compound 8 (RT=12.331 min), UV at 254 nm using HPLC method 2.

[0031] FIG. 17 is HPLC chromatogram of the diastereomer A of Example 3 (RT=11.019 min), UV at 254 nm using HPLC method 2.

[0032] FIG. 18 is HPLC chromatogram of the diastereomer B of Example 3 (RT=11.011 min), UV at 254 nm using HPLC method 2.

DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

Definitions

[0034] As used herein, the term “pharmaceutically acceptable” means suitable for use in pharmaceutical preparations, generally considered as safe for such use, officially approved by a regulatory agency of a national or state government for such use, or being listed in the U.S. Pharmacopoeia or other generally recognized pharmacopoeia for use in animals, and more particularly in humans.

[0035] As used herein, the term “pharmaceutically acceptable carrier” refers to a diluent, adjuvant, excipient, or carrier, or other ingredient which is pharmaceutically acceptable and with which a compound of the invention is administered.

[0036] As used herein, the term “pharmaceutically acceptable salt” refers to a salt which may enhance desired pharmacological activity. Examples of pharmaceutically acceptable salts include acid addition salts formed with inorganic or organic acids, metal salts and amine salts. Examples of acid addition salts formed with inorganic acids include salts with hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid and phosphoric acid. Examples of acid addition salts formed with organic acids such as acetic acid, propionic acid, hexanoic acid, heptanoic acid, cyclopentanepropionic acid, glycolic acid, pyruvic acid, lactic acid, malonic acid, succinic acid, malic acid, maleic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, o-(4-hydroxy-benzoyl)-benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, 1,2-ethanedisulfonic acid, 2-hydroxyethane-sulfonic acid, benzenesulfonic acid, p-chlorobenzenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, camphorsulfonic acid, 4-methyl-bicyclo[2.2.2]oct-2-ene1-carboxylic acid, gluco-heptonic acid, 4,4′-methylenebis(3-hydroxy-2-naphthoic) acid, 3-phenylpropionic acid, trimethyl-acetic acid, tertiary butylacetic acid, lauryl sulfuric acid, gluconic acid, glutamic acid, hydroxy-naphthoic acids, salicylic acid, stearic acid and muconic acid. Examples of metal salts include salts with sodium, potassium, calcium, magnesium, aluminum, iron, and zinc ions. Examples of amine salts include salts with ammonia and organic nitrogenous bases strong enough to form salts with carboxylic acids.

[0037] As used herein, the term “therapeutically effective amount” means when applied to a compound of the invention is intended to denote an amount of the compound that is sufficient to ameliorate, palliate, stabilize, reverse, slow or delay the progression of a disorder or disease state, or of a symptom of the disorder or disease. In an embodiment, the method of the present invention provides for administration of combinations of compounds. In such instances, the “therapeutically effective amount” is the amount of a compound of the present invention in the combination sufficient to cause the intended biological effect.

[0038] As used herein, the term “treatment” or “treating” as used herein means ameliorating or reversing the progress or severity of a disease or disorder, or ameliorating or reversing one or more symptoms or side effects of such disease or disorder. “Treatment” or “treating”, as used herein, also means to inhibit or block, as in retard, arrest, restrain, impede or obstruct, the progress of a system, condition or state of a disease or disorder. For purposes of this invention, “treatment” or “treating” further means an approach for obtaining beneficial or desired clinical results, where “beneficial or desired clinical results” include, without limitation, alleviation of a symptom, diminishment of the extent of a disorder or disease, stabilized (i.e., not worsening) disease or disorder state, delay or slowing of a disease or disorder state, amelioration or palliation of a disease or disorder state, and remission of a disease or disorder, whether partial or total.

[0039] In another embodiment, the compounds of Formula (I) are used for modulating the activity of a protein kinase c-abl.

[0040] As used herein, the term “modulating” or “modulation” refers to the alteration of the catalytic activity of a protein kinase. In particular, modulating refers to the activation or inhibition of the catalytic activity of a protein kinase, depending on the concentration of the compound or salt to which the protein kinase is exposed or, more preferably, the inhibition of the catalytic activity of a protein kinase. The term “catalytic activity” as used herein refers to the rate of phosphorylation of tyrosine, serine or threonine under the influence, direct or indirect, of a protein kinase.

[0041] The three main classes that pharmacological inhibitors of kinase activity are categorized by are (1) Type I, or “DFG-in” ATP competitive inhibitors, which directly compete with ATP in the ATP binding site (i.e., dual SRrc ABL inhibitor dasatinib, (2) Type II, or “DFG-out” ATP competitive inhibitors, which, in addition to binding the ATP binding site also engage an adjacent hydrophobic binding site that is only accessible when the kinase is in an inactivated configuration (i.e., the activation loop is oriented in a conformation that would block substrate binding) (i.e., imatinib, nilotinib), and (3) non-ATP competitive inhibitors that bind at sites outside the ATP binding site that affect the activity of the kinase (i.e., GNF-2).

[0042] As used herein, the phrase “compound(s) of this/the disclosure” includes any compound(s) of Formula (I), as well as clathrates, hydrates, solvates, or polymorphs thereof. And, even if the term “compound(s) of the disclosure” does not mention its pharmaceutically acceptable salts, the term includes salts thereof. In one embodiment, the compounds of this disclosure include stereochemically pure compounds, e.g., those substantially free (e.g., greater than 85% ee, greater than 90% ee, greater than 95% ee, greater than 97% ee, or greater than 99% ee) of other stereoisomers. That is, if the compounds of Formula (I) according to the present disclosure or salts thereof are tautomeric isomers and/or stereoisomers (e.g., geometrical isomers and conformational isomers), such isolated isomers and their mixtures also are included in the scope of this disclosure. If the compounds of the present disclosure or salts thereof have an asymmetric carbon in their structures, their active optical isomers and their racemic mixtures also are included in the scope of this disclosure.

[0043] As used herein, the term “polymorph” refers to solid crystalline forms of a compound of this disclosure or complex thereof. Different polymorphs of the same compound can exhibit different physical, chemical and/or spectroscopic properties. Different physical properties include, but are not limited to stability (e.g., to heat or light), compressibility and density (important in formulation and product manufacturing), and dissolution rates (which can affect bioavailability). Differences in stability can result from changes in chemical reactivity (e.g., differential oxidation, such that a dosage form discolors more rapidly when comprised of one polymorph than when comprised of another polymorph) or mechanical characteristics (e.g., tablets crumble on storage as a kinetically favored polymorph converts to thermodynamically more stable polymorph) or both (e.g., tablets of one polymorph are more susceptible to breakdown at high humidity). Different physical properties of polymorphs can affect their processing. For example, one polymorph might be more likely to form solvates or might be more difficult to filter or wash free of impurities than another due to, for example, the shape or size distribution of particles of it.

[0044] As used herein, the term “solvate” means a compound or its salt according to this disclosure that further includes a stoichiometric or non-stoichiometric amount of a solvent bound by non-covalent intermolecular forces. Preferred solvents are volatile, nontoxic, and/or acceptable for administration to humans in trace amounts.

[0045] As used herein, the term “hydrate” means a compound or its salt according to this disclosure that further includes a stoichiometric or non-stoichiometric amount of water bound by non-covalent intermolecular forces.

[0046] As used herein, the term “clathrate” means a compound or its salt in the form of a crystal lattice that contains spaces (e.g., channels) that have a guest molecule (e.g., a solvent or water) trapped within.

Compounds of the Present Disclosure

[0047] The present disclosure provides compounds according to Formula (I):

##STR00002##

[0048] or a pharmaceutically acceptable salt thereof, wherein R.sub.1 is —CH.sub.2CH.sub.2.sup.18F or —OCH.sub.2CH.sub.2.sup.18F when R.sub.2 is -H, or R.sub.1 is —CH.sub.2CH.sub.2.sup.18F or —OCH.sub.2CH.sub.2.sup.18F when R.sub.2 is -F.

[0049] In one embodiment, the compound of Formula (I) is selected from the compound according to Formula (IIA) and pharmaceutically acceptable salts thereof:

##STR00003##

wherein R.sub.2 is -H or -F.

[0050] In one embodiment, the compound of Formula (I) is selected from the compound according to Formula (IIB) and pharmaceutically acceptable salts thereof:

##STR00004##

wherein R.sub.2 is -H or -F.

[0051] In yet another embodiment, there is provided a pharmaceutical composition comprising a therapeutically effective amount of a compound of Formula (I) or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

[0052] In another embodiment, there is provided a method for treating a neurodegenerative disease or disorder comprising administering to a subject in need thereof a therapeutically effective amount of a compound of Formula (I) or pharmaceutically acceptable salt thereof. That is, there is provided a medical use of the compound of Formula (I) or pharmaceutically acceptable salt thereof, wherein Formula (I) or pharmaceutically acceptable salt thereof is used as an active agent. In some embodiments, the neurodegenerative disease is selected from the group consisting of a-synucleinopathy, Parkinson’s disease, dementia with Lewy body, multiple system atrophy (MSA), Alzheimer’s disease, and amyotrophic lateral sclerosis (ALS)..

[0053] In one embodiment, the present disclosure relates to fluorine-18 labeled imidazopyridine compounds as positron emission tomography (PET) tracers for imaging enzyme inhibitory activity comprising the compound and methods of using the compounds for diagnosis and imaging. In an embodiment, there is provided a method for treating a neurodegenerative disease comprising: administering to a subject in need thereof a therapeutically effective amount of the compound above or a pharmaceutically acceptable salt thereof.

[0054] In another embodiment, there is provided a method of determining an enzyme inhibitory activity, the method comprising: applying the compound above to a biological sample; and imaging the compound to determine the enzyme inhibitory activity. In various embodiments, the compound is used as a positron emission tomography (PET) tracer. The method can be a PET imaging method. Also, the method can be used in an AD-induced mouse AD model or an alpha-synuclein PFF-induced mouse PD model. The method can be used to determine c-abl upregulation or activation in a brain. In some embodiments, the method is for companion diagnosis for c-abl therapy or other disease-modifying agents as a predictive biomarker. The method can be used for a patient with a neurodegenerative disease.

EXAMPLES

[0055] Hereinafter, the present disclosure is described in considerable detail with examples to help those skilled in the art understand the present disclosure. However, the following examples are offered by way of illustration and are not intended to limit the scope of the invention. It is apparent that various changes may be made without departing from the spirit and scope of the invention or sacrificing all of its material advantages.

Synthesis of Formula (IIA) Compound

[0056] Example compound of the present disclosure is described in Scheme1.

##STR00005##

Example 1. (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-(fluoro-.SUP.18.F)ethoxy) phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-Carboxamide

Step1) 2-(2-bromo-6-fluorophenoxy)ethan-1-ol

[0057] To a solution of Compound 1 (5 g, 26.18 mmol, 1 eq), 2-bromoethanol (6.54 g, 52.36 mmol, 3.72 mL, 2 eq) in MeCN (50 mL) was added K.sub.2CO.sub.3 (7.60 g, 54.97 mmol, 2.1 eq). The mixture was stirred at 80° C. for 12 hr. The reaction mixture was filtered and concentrated under reduced pressure to give a residue. The residue was purified by silica gel chromatography (SiO.sub.2, petroleum ether-ethyl acetate=1:0 to 10:1). Compound 2 (6.0 g, 25.53 mmol, 97.51% yield) was obtained as a yellow oil.

[0058] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 7.46 (td, J = 1.5, 8.1 Hz, 1H), 7.33 (ddd, J = 1.4, 8.4, 11.0 Hz, 1H), 7.10 (dt, J = 5.5, 8.3 Hz, 1H), 4.83 - 4.60 (m, 2H), 4.39 - 4.24 (m, 2H); LCMS (electrospray) m/z 236.05 (M+H)+.

Step 2) (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-hydroxyethoxy)phenyl) imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0059] To a solution of Compound 2 (1 g, 4.25 mmol, 1 eq) and Compound 3 (1.76 g, 5.11 mmol, 1.2 eq) in dioxane (0.4 mL) and H.sub.2O (0.1 mL) was added Na.sub.2CO.sub.3 (901.84 mg, 8.51 mmol, 2 eq) and Pd(dppf)Cl.sub.2 (155.65 mg, 212.72 .Math.mol, 0.05 eq) under N.sub.2 atmosphere. The mixture was stirred at 80° C. for 12 hr under N.sub.2 atmosphere. The reaction mixture was diluted with water 200 mL and extracted with ethyl acetate (200 mL * 2). The combined organic layers were washed with brine 100 mL, dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by silica gel chromatography (SiO.sub.2, petroleum ether-ethyl acetate=1:0 to 0:1). Compound 4 (770 mg, 2.06 mmol, 48.48% yield) was obtained as a yellow solid.

[0060] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.03 (s, 1H), 883 (s, 1H), 8.09 (s, 1H), 7.51 - 7.41 (m, 2H), 7.35 - 7.26 (m, 2H), 7.25 - 7.16 (m, 1H), 5.06 - 4.84 (m, 1H), 4.82 -4.73 (m, 1H), 3.93 (t, J = 4.9 Hz, 2H), 3.55 (q, J = 4.4 Hz, 2H), 2.21 - 2.08 (m, 1H), 1.74 - 1.58 (m, 1H), 1.21 - 1.07 (m, 1H); LCMS (electrospray) m/z 374.35 (M+H)+.

Step 3) 2-(2-fluoro-6-(2-((1S,2S)-2-fluorocyclopropane-1-carboxamido) imidazo[1,2-a]pyridin-6-yl)phenoxy)ethyl 4-methylbenzenesulfonate

[0061] To a solution of Compound 4 (690 mg, 1.85 mmol, 1 eq) in THF (20 mL) was added TEA (467.52 mg, 4.62 mmol, 643.09 .Math.L, 2.5 eq), DMAP (22.58 mg, 184.81 .Math.mol, 0.1 eq) and TsCI (704.68 mg, 3.70 mmol, 2 eq). The mixture was stirred at 25° C. for 12 hr under N.sub.2 atmosphere. The reaction mixture was concentrated under reduced pressure, diluted with water 200 mL and extracted with ethyl acetate (200 mL * 2). The combined organic layers were washed with brine 100 mL, dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by silica gel chromatography (SiO.sub.2, petroleum ether-ethyl acetate=1:0 to 85:15). Compound 5 (470 mg, 890.93 .Math.mol, 48.21 % yield) was obtained as a yellow solid.

[0062] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.06 (s, 1H), 8.65 (d, J = 0.6 Hz, 1H), 8.11 (s, 1H), 7.59 (d, J = 8.3 Hz, 2H), 7.43 - 7.38 (m, 1H), 7.36 - 7.28 (m, 4H), 7.28 - 7.19 (m, 2H), 5.06 - 4.82 (m, 1H), 4.16 - 4.05 (m, 4H), 2.37 (s, 3H), 2.21 - 2.12 (m, 1H), 1.74 - 1.62 (m, 1H), 1.22 - 1.13 (m, 1H); LCMS (electrospray) m/z 528.54 (M+H)+.

Step 4) (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-(fluoro-.SUP.18.F)ethoxy)phenyl) imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0063] [.sup.18F]Fluoride was produced by the .sup.18O(p,n).sup.18F nuclear reaction in an IBA Cyclone® 18/9 cyclotron using a [.sup.18O]H.sub.2O liquid target. After irradiation, the target water was passed through a Chromafix 45 mg PS-HCO.sub.3- .sup.18F separation cartridge. The trapped [.sup.18F]fluoride was eluted with an aq. K.sub.2SO.sub.4 solution (500 .Math.L, 0.1 M) into a vial containing DMF (850 .Math.L). A solution of N,N-bis(trifluoromethylsulfonyl)aniline (150 .Math.L, 0.1 M) in DMF was added and the temperature was set to 40° C. The formed [.sup.18F]triflyl fluoride was distilled over a drying column (P.sub.2O.sub.5) into a vial containing DCB (850 .Math.L) and a K.sub.222/K.sub.2CO.sub.3 solution (12 .Math.mol K.sub.222 and 12 .Math.mol K.sub.2CO.sub.3 in 100 .Math.L MeCN) to obtain free [.sup.18F]fluoride. The distillate receiving vial was cooled to -5° C. to efficiently trap the [.sup.18F]triflyl fluoride during the distillation. The distillation was finished after approximately 5 min. Afterward, the precursor, Compound 5 (0.5 mg) in DCB (50 .Math.L) was added. The mixture was heated at 120° C. for 10 min and then cooled before it was diluted with pentane (1.5ml). The diluted mixture was rinsed through a silica cartridge (Sep-Pak silica light cartridge, Waters) to remove the DCB and trap unreacted [.sup.18F]F.sup.-. The product was eluted with MeCN (1 ml) and diluted with water (1 ml) prior to purification by semi-preparative HPLC on an Altima C18 5 .Math.m column using isocratic 40% MeCN in water with 0.1 % TFA and flow rate 4 ml/min for 30 min. With these conditions, [.sup.18F] Example 1 was isolated in a RCY (d.c.) of 3.4%±1.0% (n=3) and a A.sub.m of 99±35 GBq/.Math.mol (n=3). The isolated fraction of Example 1 was diluted with water (50 ml) and the product was trapped on a tC18 cartridge (Sep-Pak tC18 plus short cartridge, Waters). The EtOH was removed by a stream of He (15 ml/min) under vacuum at 80° C. for 10 min. The residual was cooled before it was reformulated in an appropriate volume of EtOH/saline for animal studies. Total synthesis time including radiolabeling, purification, isolation and reformulation was 59-65 min.

[0064] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.04 (s, 1H), 8.73 (s, 1H), 8.10 (s, 1H), 7.53 - 7.20 (m, 5H), 5.13 - 4.77 (m, 1H), 4.60 - 4.44 (m, 2H), 4.20 - 4.07 (m, 2H), 2.21 -2.10 (m, 1H), 1.75 - 1.57 (m, 1H), 1.16 (tdd, J = 6.0, 9.1, 12.2 Hz, 1H).; LCMS (electrospray) m/z 375.35 (M+H)+.

Example 2. (1S,2S)-2-fluoro-N-(6-(2-(2-(fluoro-.SUP.18.F)ethoxy)phenyl) imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0065] Synthetic method is same as Example 1.

##STR00006##

[0066] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.02 (s, 1H), 8.67 (t, J = 1.4 Hz, 1H), 8.07 (s, 1H), 7.44-7.35 (m, 4H), 7.16 (d, J = 8.0 Hz, 1H), 7.10-7.06 (m, 1H), 5.01-4.82 (m, 1H), 4.72 (dt, J = 47.8, 3.8 Hz, 2H), 4.29 (dt, J = 29.7, 3.8 Hz, 2H), 2.15-2.12 (m, 1H), 1.68-1.62 (m, 1H), 1.18-1.13 (m, 1H).;LCMS (electrospray) m/z 357.36 (M+H)+.

Synthesis of Formula (IIB) Compound

[0067] Example compound of the present disclosure is described in Scheme2.

##STR00007##

Example 3. (1S,2S)-2-fluoro-N-(6-(2-(2-(fluoro-.SUP.18.F)ethyl)phenyl) imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

Step1) (1S,2S)-2-fluoro-N-(6-(2-(2-hydroxyethyl)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0068] To a solution of Compound 6 (2.54 g, 7.36 mmol, 1 eq) and Compound 3 (1.48 g, 7.36 mmol, 1 eq) in dioxane (4 mL) and H.sub.2O (16 mL) was added Na.sub.2CO.sub.3 (1.56 g, 14.7 mmol, 2 eq) and Pd(dppf)Cl.sub.2 (538 mg, 0.74 mmol, 0.1 eq) under N.sub.2 atmosphere. The mixture was stirred at 80° C. for 12 hr under N.sub.2 atmosphere. The reaction mixture was filtered and diluted with water (20 mL), and then extracted by ethyl acetate (40 mL * 3), the combined organic layers were dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by silica gel chromatography (SiO.sub.2, petroleum ether-ethyl acetate=1:4) to give Compound 7 (990 mg, 2.92 mmol, 39.6% yield) as a brown solid.

[0069] .sup.1H NMR (400 MHz, DMSO-d.sub.6) & 11.02 (s, 1H), 8.53 (s, 1H), 8.10 (s, 1H), 7.46 (d, J = 9.17 Hz, 1H), 7.39 - 7.33 (m, 2H), 7.31 - 7.24 (m, 2H), 7.21 - 7.19 (m, 2H), 5.01 - 4.93 (m, 1H), 4.61 (t, J = 5.3 Hz, 1H), 3.52 - 3.47 (m, 2H), 2.74 (t, J = 7.27 Hz, 2H), 2.17 - 2.13 (m, 1H), 1.70 - 1.62 (m, 1H), 1.19 - 1.13 (m, 1H); LCMS (electrospray) m/z 340.10 (M+H)+.

Step 2) 2-(2-((1S,2S)-2-fluorocyclopropane-1-carboxamido)imidazo[1,2-a]pyridin-6-yl)phenethyl 4-methylbenzenesulfonate

[0070] To a mixture of Compound 7 (940.00 mg, 2.77 mmol, 1 eq) in DCM (80 mL) was added TsCI (3.17 g, 16.62 mmol, 6 eq) and TEA (1.96 g, 19.39 mmol, 2.70 mL, 7 eq) and DMAP (101.52 mg, 830.97 .Math.mol, 0.3 eq) in one portion at 0° C. under N.sub.2, then the mixture was stirred at 0° C. for 10 min, then heated to 20° C. and stirred for 4 hours. The reaction mixture was quenched by addition H.sub.2O 20 mL at 0° C., and then washed with NaHCO.sub.3 (40 mL * 2). The organic layers were washed with saturated NaCl solution 40 mL, dried over Na.sub.2SO.sub.4, filtered and concentrated under reduced pressure to give a residue. The residue was purified by column chromatography (SiO.sub.2, petroleum ether/ethyl acetate=4/1 to ⅓). Compound 8 (860 mg, 1.74 mmol, 62.91 % yield) was obtained as a white solid.

[0071] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.08 (s, 1H), 8.42 (s, 1H), 8.08 (s, 1H), 7.53 (d, J = 8.3 Hz, 2H), 7.42 (d, J = 9.2 Hz, 1H), 7.34 - 7.32 (m, 3H), 7.27 - 7.24 (m, 3H), 7.04 (dd, J = 1.5, 9.2 Hz, 1H), 5.03 - 4.85 (m, 1H), 4.09 (t, J = 6.8 Hz, 2H), 2.91 (t, J = 6.8 Hz, 2H), 2.37 (s, 3H), 2.19 - 2.16 (m, 1H), 1.72 - 1.65 (m, 1H), 1.20 - 1.15 (m, 1H); LCMS (electrospray) m/z 494.10 (M+H)+.

Step 3) (1S,2S)-2-fluoro-N-(6-(2-(2-(fluoro-.SUP.18.F)ethyl)phenyl)imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0072] [.sup.18F]Fluoride was produced by the .sup.18O(p,n).sup.18F nuclear reaction in an IBA Cyclone® 18/9 cyclotron using a [.sup.18O]H.sub.2O liquid target. After irradiation, the target water was passed through a Chromafix 45 mg PS-HCO.sub.3- .sup.18F separation cartridge. The trapped [.sup.18F]fluoride was eluted with an aq. K.sub.2SO.sub.4 solution (500 .Math.L, 0.1 M) into a vial containing DMF (850 .Math.L). A solution of N,N-bis(trifluoromethylsulfonyl)aniline (150 .Math.L, 0.1 M) in DMF was added and the temperature was set to 40° C. The formed [.sup.18F]triflyl fluoride was distilled over a drying column (P.sub.2O.sub.5) into a vial containing MeCN (900 .Math.L) with K.sub.222/K.sub.2CO.sub.3 solution (12 .Math.mol K.sub.222 and 12 .Math.mol K.sub.2CO.sub.3 in 100 .Math.L MeCN) to obtain free [.sup.18F]fluoride. The distillate receiving vial had a temperature of 20° C. The distillation was finished after approximately 5 min. Afterward, the precursor Compound 8 (1 mg) in MeCN (100 .Math.L) was added. The mixture was heated at 80° C. for 10 min and then cooled before water (1 mL) was added for dilution prior to purification. The diluted mixture was purified by semi-preparative HPLC on a Luna C18 5 .Math.m using 45% MeCN in 20 mM NH.sub.4OAc (pH 4). With these conditions, [.sup.18F] Example 3 was isolated in a RCY(d.c.) of 6.7%±3.5% (n=4) and a A.sub.m of 132±60 GBq/.Math.mol (n=4). The isolated fraction was diluted with water (60 mL) and the product was trapped on a tC18 cartridge (Sep-Pak tC18 plus short cartridge, Waters). The cartridge was washed with water (25 mL) and [.sup.18F] Example 3 was eluted with EtOH (1 mL). The EtOH was removed by a stream of He (15 mL/min) under vacuum at 80° C. for 10 min. The residual was cooled before it was reformulated in an appropriate volume of EtOH/saline for animal studies. Total synthesis time including radiolabeling, purification, isolation and reformulation was 62-68 min.

[0073] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.03 (s, 1H), 8.52 (s, 1H), 8.10 (s, 1H), 7.49 - 7.42 (m, 2H), 7.39 (dt, J = 1.7, 7.3 Hz, 1H), 7.36 - 7.28 (m, 2H), 7.19 (dd, J = 1.7, 9.1 Hz, 1H), 5.04 - 4.80 (m, 1H), 4.63 - 4.46 (m, 2H), 3.06 - 2.91 (m, 2H), 2.21 - 2.08 (m, 1H), 1.74 - 1.59 (m, 1H), 1.16 (tdd, J = 6.2, 9.2, 12.3 Hz, 1H).;LCMS (electrospray) m/z 341.10 (M+H)+.

Example 4. (1S,2S)-2-fluoro-N-(6-(3-fluoro-2-(2-(fluoro-.SUP.18.F)ethyl)phenyl) imidazo[1,2-a]pyridin-2-yl)cyclopropane-1-carboxamide

[0074] Synthetic method is same as Example 3.

##STR00008##

[0075] .sup.1H NMR (400 MHz, DMSO-d.sub.6) δ 11.05 (s, 1H), 8.56 (s, 1H), 8.11 (s, 1H), 7.48 (t, J = 9.1 Hz, 1H), 7.43-7.24 (m, 2H), 7.22-7.14 (m, 2H), 5.03-4.82 (m, 1H), 4.50 (dt, J = 46.9, 6.5 Hz, 2H), 3.02 (dt, J = 22.0, 6.3 Hz, 2H), 2.18-2.11 (m, 1H), 1.71-1.60 (m, 1H), 1.20-1.12 (m, 1H).;LCMS (electrospray) m/z 359.35 (M+H)+.

Analytical HPLC Chromatograms

[0076] Two analytical HPLC methods were established; one isocratic (HPLC method 1) and one gradient (HPLC method 2). HPLC method 1 was used to determine the A.sub.m of the tracer examples. The table 1 is conditions for HPLC method 1 and retention times for Example 1, Example 3 and isomers. The HPLC chromatograms (UV and radioactivity detection) were shown in FIGS. 1-10.

TABLE-US-00001 HPLC isocratic conditions and retention times for analytes Column Altima C18 5 .Math.m (250 × 4.6 mm) Eluent Isocratic; 40% MeCN in H.sub.2O with (0.1%) Flow rate 1 ml/min UV detection 254 nm Analytes Retention time (min) Example 1 9.504 Precursor, Compound 5 29.876 Diastereomer A of Example 1 11.690 Diastereomer B of Example 1 11.684 Example 3 8.987 Precursor, Compound 8 27.502 Diastereomer A of Example 3 10.988 Diastereomer B of Example 3 10.993

[0077] The Table 2 is conditions for HPLC method 2 and retention times for Example 1, Example 3 and isomers. The HPLC chromatograms (UV and radioactivity detection) were shown in FIGS. 11-18.

TABLE-US-00002 HPLC gradient conditions and retention times for analytes Column Luna C18 5 .Math.m (250 × 4.6 mm) Eluent Gradient; 20-80% MeCN (0.1% TFA) in H.sub.2O (0.1% TFA) Flow rate 1 ml/min UV detection 254 nm Example 1 10.710 Precursor, Compound 5 12.392 Diastereomer A of Example 1 11.114 Diastereomer B of Example 1 11.116 Example 3 10.637 Precursor, Compound 8 12.331 Diastereomer A of Example 3 11.019 Diastereomer B of Example 3 11.011