Pyrazolo[4,3-c]pyridine compounds or pharmaceutically acceptable salts thereof and uses thereof

Abstract

The present invention relates to pyrazolo[4,3-c]pyridine compounds or pharmaceutically acceptable salts thereof and their uses. The structural formula of the pyrazolo[4,3-c]pyridine compounds is shown below as Formula (I) or (II). The compounds exhibit excellent inhibitory activity against PDE4 and have promising application prospects in the preparation of cyclic nucleotide phosphodiesterase 4 inhibitors and in the preparation of drugs for treating cyclic nucleotide phosphodiesterase 4-related diseases. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the technical field of pharmaceutical chemistry, and more specifically relates to pyrazolo[4,3-c]pyridine compounds or pharmaceutically acceptable salts thereof and applications thereof. Background Art

[0002] Cyclic nucleotide phosphodiesterases (PDEs) specifically target cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). They catalyze the hydrolysis of cAMP and / or cGMP to produce the corresponding inactive AMP and / or GMP, thereby controlling their intracellular concentrations and influencing a variety of physiological processes and metabolic functions. The PDE family comprises 11 subtypes (PDE1–PDE11) and can be divided into three categories based on their substrates: cAMP-specific hydrolases (PDE4, PDE7, and PDE8), cGMP-specific hydrolases (PDE5, PDE6, and PDE9), and dual hydrolases (PDE1, PDE2, PDE3, PDE10, and PDE11). PDE4 and PDE9 regulate numerous physiological processes, such as energy metabolism, memory, immune responses, vision, olfaction, and the growth of various cell types, by regulating cAMP and cGMP and activating the protein kinase A (PKA) and protein kinase G (PKG) pathways.

[0003] PDE4 has four isoforms, PDE4A-D. With the exception of PDE4C, the other three isoforms are highly expressed in the cerebral cortex, olfactory bulb, hippocampus, and brainstem. Furthermore, PDE4B is highly expressed in the striatum, amygdala, hypothalamus, and thalamus. Numerous studies have confirmed that PDE4 is widely involved in various brain neurological activities. PDE4 inhibitors inhibit PDE4 by upregulating cAMP levels, activating the cAMP / PKA / CREB pathway to regulate BDNF levels, promoting synaptic growth, increasing synaptic plasticity, and neuronal survival, thereby improving cognitive function. Furthermore, increased cAMP levels can inhibit the nuclear translocation of NF-κB, thereby downregulating intracellular levels of inflammatory factors (such as TNF-α, IL-1, and IL-6), alleviating neuroinflammation and reducing inflammation-induced neuronal damage and apoptosis. PDE4 inhibitors have been used in research for a variety of diseases, including asthma, chronic obstructive pulmonary disease (COPD), rheumatoid arthritis, atopic dermatitis, psoriasis, Alzheimer's disease, schizophrenia, and depression.

[0004] Currently, there are only three PDE4 inhibitors on the market: roflumilast, apremilast, and crisaborole. In actual clinical use, all three PDE4 inhibitors have adverse reactions to varying degrees. Therefore, the current selection of PDE4 inhibitors is very limited, and further research and development of new PDE4 inhibitors is necessary. Summary of the Invention

[0005] In view of the above-mentioned problems in the prior art, the primary object of the present invention is to provide a pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof, which exhibits good inhibitory activity against cyclic nucleotide phosphodiesterase 4.

[0006] The second object of the present invention is to provide a pharmaceutical composition.

[0007] The third object of the present invention is to provide the use of a pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt or pharmaceutical composition thereof in the preparation of a cyclic nucleotide phosphodiesterase inhibitor.

[0008] The fourth object of the present invention is to provide a use of a pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt or pharmaceutical composition thereof in the preparation of a drug for treating diseases caused by cyclic nucleotide phosphodiesterase.

[0009] The above purpose of the present invention is achieved through the following technical solutions:

[0010] A pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof, wherein the structural formula of the pyrazolo[4,3-c]pyridine compound is shown in the following formula (I) or (II):

[0011]

[0012] Among them, R 1 is selected from an alkyl group containing 1 to 6 carbon atoms;

[0013] R 2 Selected from halogen, cyano;

[0014] R 3 selected from hydrogen;

[0015] R 4 is selected from a heterocyclic group containing 5 to 8 carbon atoms, a hydroxypropyl group, a carboxyethyl group, a carboxypropyl group, an N-hydroxy-alkanoyl group; the heterocyclic group contains 1, 2, 3 or 4 heteroatoms selected from oxygen, sulfur and nitrogen;

[0016] R 5is selected from hydrogen, a substituted alkyl group containing 1 to 6 carbon atoms, or a heterocyclic group containing 5 to 8 carbon atoms; wherein the substituted alkyl group is replaced by one or more halogens, and the heterocyclic group contains 1, 2, 3 or 4 heteroatoms selected from oxygen, sulfur and nitrogen.

[0017] In some embodiments, when the structural formula of the pyrazolo[4,3-c]pyridine compound is formula (I), R 1 Selected from ethyl;

[0018] R 2 Selected from chlorine, cyano;

[0019] R 3 selected from hydrogen;

[0020] R 4 is selected from pyran, carboxyethyl, carboxypropyl, N-hydroxy-acetamido, N-hydroxy-propionamido; R 5 is selected from hydrogen, trifluoromethyl or pyridine;

[0021] When the structural formula of the pyrazolo[4,3-c]pyridine compound is formula (II),

[0022] R 1 Selected from ethyl;

[0023] R 2 selected from chlorine;

[0024] R 3 selected from hydrogen;

[0025] R 4 is selected from pyran, hydroxypropyl, carboxyethyl, N-hydroxy-acetamido, N-hydroxy-propionamido; R 5 Selected from hydrogen.

[0026] In some embodiments, the pyrazolo[4,3-c]pyridine compound is selected from any of the following structures:

[0027]

[0028] In some embodiments, the pyrazolo[4,3-c]pyridine compound is selected from any of the following structures:

[0029]

[0030]

[0031] Furthermore, the present invention also seeks to protect a pharmaceutical composition comprising the above-mentioned pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof; and a pharmaceutically acceptable carrier, diluent and / or excipient.

[0032] Furthermore, the present invention also seeks to protect the use of the above-mentioned pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof or the above-mentioned pharmaceutical composition in the preparation of a cyclic nucleotide phosphodiesterase inhibitor.

[0033] Furthermore, the present invention also seeks to protect the use of the above-mentioned pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof or the above-mentioned pharmaceutical composition in the preparation of a drug for treating diseases caused by cyclic nucleotide phosphodiesterase.

[0034] In some embodiments, the cyclic nucleotide phosphodiesterase is cyclic nucleotide phosphodiesterase 4.

[0035] In some embodiments, the disease is one or more of an allergic disease, an autoimmune disease, a central nervous system disease, or a disease with ischemic reflow caused by heart failure, shock, and cerebrovascular disease.

[0036] In some embodiments, the allergic disease is one or more of asthma, chronic obstructive pulmonary disease, allergic rhinitis, or nephritis.

[0037] In some embodiments, the autoimmune disease is one or more of rheumatoid arthritis, multiple sclerosis, Crohn's disease, or systemic lupus erythematosus.

[0038] In some embodiments, the central nervous system disease is one or more of depression, amnesia, or dementia.

[0039] Furthermore, the present invention also claims protection for a treatment method, which comprises administering a therapeutically effective amount of the above-mentioned pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof, or the above-mentioned pharmaceutical composition to a patient in need thereof.

[0040] Compared with the prior art, the present invention has the following advantages: It provides a pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof. The pyrazolo[4,3-c]pyridine compound exhibits excellent inhibitory activity against PDE4, with the inhibitory activity reaching up to 16.6 nM. Based on the excellent inhibitory activity of the pyrazolo[4,3-c]pyridine compound against PDE4, the present invention has promising application prospects in the treatment of allergic diseases, autoimmune diseases, central nervous system diseases, or ischemic regurgitation caused by heart failure, shock, and cerebrovascular disease. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is the inhibitory activity of compound 19 on PDE4D7.

[0042] Figure 2is the inhibitory activity of compound 22 on PDE4D7. DETAILED DESCRIPTION

[0043] Through extensive research, the inventors, guided by the limited availability of existing PDE4 inhibitors and the varying degrees of adverse reactions, designed, synthesized, and screened a novel pyrazolo[4,3-c]pyridine compound. This compound exhibits excellent inhibitory activity against PDE4 and exhibits no significant toxicity to neural cells. The present invention is further illustrated below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents and methods described in these examples are commonly used in the art.

[0044] In the present invention, unless the context otherwise requires, the words, phrases and symbols used below shall have the following meanings. The following abbreviations and terms shall have the following meanings throughout the text:

[0045] The term "halogen" refers to fluorine, chlorine, bromine and iodine. The term "halo" before a group name means that the group is partially or fully halogenated, ie substituted with F, Cl, Br or I in any combination.

[0046] As used herein, "pharmaceutically acceptable salts" refer to salts of the compounds of the invention, prepared from compounds with specific substituents discovered herein with relatively nontoxic acids, and can be used to form salts for use in the art. When the compound of formula (I) or (II) contains a free base, such salts are prepared in a conventional manner by treating a solution or suspension of the free base of formula (I) or (II) with a molar equivalent of a pharmaceutically acceptable acid. Representative examples of suitable organic and inorganic acids are described below.

[0047] Pharmaceutically acceptable salts in the context of the present invention are intended to indicate non-toxic, ie physiologically acceptable salts. The term pharmaceutically acceptable base addition salt includes sodium, potassium, calcium, ammonium, organic amino or magnesium salts or similar salts.

[0048] The term "therapeutically effective amount" of a compound means an amount sufficient to alleviate, block, partially block, eliminate or delay the clinical manifestations of a given disease and its complications in a therapeutic intervention comprising the administration of the compound. Pharmaceutical compositions comprising the compounds of the present invention can be specifically formulated for administration by any suitable route, such as oral, rectal, nasal, buccal, sublingual, transdermal and parenteral (e.g., subcutaneous, intramuscular and intravenous) routes.

[0049] The term "excipient" or "pharmaceutically acceptable excipient" refers to pharmaceutical excipients, including but not limited to fillers, anti-adhesives, binders, coatings, colorants, disintegrants, flavorings, glidants, lubricants, preservatives, sorbents, sweeteners, solvents, vehicles, and adjuvants. For example, microcrystalline cellulose, corn starch, lactose, mannitol, povidone, croscarmellose sodium, sucrose, talc, gelatin, pectin, magnesium stearate, stearic acid, lower alkyl ethers of cellulose, ethanol, propylene glycol, glycerol, polyethylene glycol, poloxamer, sorbitol, polysorbate, monoglycerides and diglycerides, cyclodextrins, coconut oil, palm oil, and water, etc.

[0050] In the present invention, the dosage of the compound can be considered to be in the range of 0.01 mg / kg body weight to about 50 mg / kg body weight per day. The exact dosage will depend on the frequency and mode of administration, the sex, age, weight and general condition of the subject to be treated, the condition to be treated, the nature and severity of any concomitant disease to be treated, the desired therapeutic effect and other factors known to those of ordinary skill in the art.

[0051] The present invention will be further described in detail below with reference to specific examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0052] Example 1 Synthesis of Compound 1 and Compound 2

[0053] The synthesis of compound 1 (6-chloro-4-ethoxy-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridine) and compound 2 (6-chloro-4-ethoxy-2-(tetrahydro-2H-pyran-4-yl)-2H-pyrazolo[4,3-c]pyridine) is as follows:

[0054]

[0055] The specific steps of preparation include:

[0056] (1) Synthesis of intermediates 1-1 and 1-2:

[0057] A 25 mL round-bottom flask was charged with 4,6-dichloro-1H-pyrazolo[4,3-c]pyridine (1 mmol, 1.0 equiv.), tetrahydro-2H-pyran-4-ol (1.5 mmol, 1.5 equiv.), triphenylphosphine (1.5 mmol, 1.5 equiv.), and 10 mL of tetrahydrofuran. A 0.5 M solution of di-tert-butyl azodicarboxylate (1.5 mmol, 1.5 equiv.) in tetrahydrofuran (3 mL) was added dropwise under argon at 0°C. The mixture was allowed to warm to room temperature and stirred for 24 hours. After dilution with ethyl acetate, the organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:10 (v / v) as the eluent to obtain N 1 The substituted intermediate 1-1 (white solid, yield 45%) was further eluted with ethyl acetate / petroleum ether = 1:5 (V / V) to obtain N 2 Substituted intermediate 1-2 (white solid, 35% yield);

[0058] (2) Synthesis of Compound 1 and Compound 2:

[0059] Intermediate 1-1 was dissolved in ethanol, sodium ethoxide (1 mmol) was added, and the mixture was heated to 60°C for 30 minutes. The reaction was monitored by TLC. After concentration, water was added, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain the title compound 1 (white solid, 95% yield). Similarly, compound 2 (white solid, 93% yield) was obtained from Intermediate 1-2.

[0060] Example 2 Synthesis of Compound 3

[0061] The synthesis of compound 3 (6-chloro-4-isopropoxy-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridine) comprises the following steps:

[0062] Intermediate 1-1 (1 mmol, 1.0 equiv.) from Step 1 of Example 1 was dissolved in 1.5 mL of tetrahydrofuran, and potassium tert-butoxide (1 mmol, 1.0 equiv.) and isopropanol (0.5 mL) were added. The mixture was heated to 80°C and reacted for 2 hours. The reaction was monitored by TLC. After concentration, water was added and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain compound 3 (white solid, 85% yield).

[0063] Example 3 Synthesis of Compound 4

[0064] Synthesis of compound 4 (6-chloro-4-propoxy-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridine): According to the preparation method of Example 2, the isopropanol in Example 2 was replaced with n-propanol to prepare compound 4.

[0065] Example 4 Synthesis of Compound 5

[0066] Synthesis of compound 5 (6-chloro-4-ethoxy-1-((3-oxetanyl)-3-methyl)-1H-pyrazolo[4,3-c]pyridine): According to the preparation method of Example 1, the raw material tetrahydro-2H-pyran-4-ol in step (1) of Example 1 was replaced with (3-methyloxetanyl)methanol to obtain the corresponding intermediate 4-1, and then step (2) was performed to prepare compound 5.

[0067] Example 5 Synthesis of Compound 6 and Compound 7

[0068] The synthesis of compound 6 (6-chloro-4-ethoxy-1-(3-methoxyphenyl)-1H-pyrazolo[4,3-c]pyridine) and compound 7 (6-chloro-4-ethoxy-2-(3-methoxyphenyl)-2H-pyrazolo[4,3-c]pyridine) is as follows:

[0069]

[0070] The specific steps of preparation include:

[0071] (1) Synthesis of Intermediate 5-1 (4,6-dichloro-1-(3-methoxyphenyl)-1H-pyrazolo[4,3-c]pyridine) and Intermediate 5-2 (4,6-dichloro-1-(3-methoxyphenyl)-2H-pyrazolo[4,3-c]pyridine):

[0072] A 25 mL round-bottom flask was charged with 4,6-dichloro-1H-pyrazolo[4,3-c]pyridine (1 mmol, 1.0 equiv.), 3-methoxyphenylboronic acid (1.5 mmol, 1.5 equiv.), copper acetate (0.25 mmol, 0.25 equiv.), diisopropylethylamine (1.5 mmol, 1.5 equiv.), and 10 mL of dichloromethane. After stirring at room temperature for 24 hours, the insoluble matter was removed with celite, and the filter cake was washed with dichloromethane, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:10 (v / v) as the eluent to obtain N 1The substituted intermediate 5-1 (white solid, yield 45%) was further eluted with ethyl acetate / petroleum ether = 1:5 (V / V) to obtain N 2 Substituted intermediate 5-2 (white solid, 25% yield);

[0073] (2) Synthesis of Compound 6: Compound 6 was synthesized from Intermediate 5-1 by referring to the preparation method of step (2) of Example 1. Similarly, Compound 7 was obtained from Intermediate 5-2.

[0074] Example 6 Synthesis of Compound 8

[0075] The synthesis of compound 8 (4-ethoxy-6-phenyl-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridine) is as follows:

[0076]

[0077] Compound 8 was prepared by adding compound 1 (0.1 mmol, 1.0 equiv.), phenylboronic acid (0.15 mmol, 1.5 equiv.), tetrakistriphenylphosphine palladium (0.005 mmol, 0.05 equiv.), potassium carbonate (0.15 mmol, 1.5 equiv.), 1,4-dioxane, and water (volume ratio 5:1, 2 mL) to a 10 mL screw-capped vial. After stirring at 80°C under argon for 10 hours, the insoluble matter was removed with celite and then rinsed with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was then evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:3 (v / v) as the eluent to obtain compound 8 as a white solid, with a yield of 45%.

[0078] Example 7 Synthesis of Compound 9

[0079] Synthesis of compound 9 (4-ethoxy-1-(tetrahydro-2H-pyran-4-yl)-6-(thiophen-2-yl)-1H-pyrazolo[4,3-c]pyridine): According to the preparation method of Example 6 above, the raw material phenylboronic acid in Example 6 was replaced with 2-thiopheneboronic acid to prepare compound 9.

[0080] Example 8 Synthesis of Compound 10

[0081] The synthesis of compound 10 (4-ethoxy-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridine-6-carbonitrile) is as follows:

[0082]

[0083] Compound 10 was prepared by adding compound 1 (0.1 mmol, 1.0 equiv.), zinc cyanide (0.15 mmol, 1.5 equiv.), tetrakistriphenylphosphine palladium (0.005 mmol, 0.05 equiv.), and 2 mL of N-methylpyrrolidone to a 10 mL screw-capped vial. After stirring at 150°C under argon for 5 hours, the insoluble matter was removed with celite and then rinsed with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was then evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:2 (v / v) as the eluent to obtain compound 10 as a white solid, in an 85% yield.

[0084] Example 9 Synthesis of Compound 11

[0085] The synthesis of compound 11 (1-(4-ethoxy-1-(tetrahydro-2H-pyran-4-yl)-1H-pyrazolo[4,3-c]pyridin-6-yl)ethan-1-one) is as follows:

[0086]

[0087] Compound 11 was prepared by adding compound 10 (0.1 mmol, 1.0 equiv.) and 2 mL of anhydrous tetrahydrofuran to a 10 mL screw-cap vial. Methylmagnesium bromide (0.15 mmol, 1.0 M solution in tetrahydrofuran, 0.15 mL, 1.5 equiv.) was added dropwise at 0°C under argon. After stirring at room temperature for 12 hours, the mixture was quenched by addition of saturated ammonium chloride solution. The mixture was diluted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 3:1 (v / v) as the eluent to obtain compound 11 as a white solid, with a yield of 75%.

[0088] Example 10 Synthesis of Compound 12 and Compound 13

[0089] The synthesis of compound 12 (2-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)ethane-1-ol) and compound 13 (2-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)ethane-1-ol) is as follows:

[0090]

[0091] The specific steps of preparation include:

[0092] (1) Synthesis of Intermediates 10-1 and 10-2: 4,6-dichloro-1H-pyrazolo[4,3-c]pyridine (2 mmol, 1.0 equiv.), (2-bromoethoxy)(tert-butyl)dimethylsilane (3 mmol, 1.5 equiv.), potassium carbonate (3 mmol, 1.5 equiv.) and 10 mL of dimethyl sulfoxide were added to a 25 mL round-bottom flask. After stirring at room temperature for 24 hours, the mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:10 (V / V) as the eluent to obtain N 1 The substituted intermediate 10-1 (colorless liquid, yield 55%) was further eluted with ethyl acetate / petroleum ether = 1:5 (V / V) to obtain N 2 Substituted intermediate 10-2 (colorless liquid, yield 35%);

[0093] (2) Synthesis of Compound 12: In a 25 mL round-bottom flask, intermediate 10-1 (1 mmol, 1.0 equiv.), sodium ethoxide (2 mmol, 2 equiv.), and 5 mL of ethanol were added. After stirring at 80°C for 1 hour, the solvent was evaporated under reduced pressure, the mixture was diluted with water, and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The mixture was dissolved in 5 mL of tetrahydrofuran, and tetrabutylammonium fluoride (2 mmol, 2.0 equiv.) was added. After stirring at 55°C for 4 hours, the solvent was evaporated under reduced pressure. After dilution with ethyl acetate, the organic layer was washed with dilute hydrochloric acid (3.0 M) and saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:10 (v / v) as the eluent to obtain compound 12 (white solid, yield 85%). Similarly, compound 13 (white solid, yield 73%) was obtained from intermediate 10-2.

[0094] Example 11 Synthesis of Compound 14

[0095] The synthesis of compound 14 (2-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)acetic acid) is as follows:

[0096]

[0097] Compound 14 was prepared by adding compound 12 (0.1 mmol, 1.0 equiv.), ferric nitrate nonahydrate (0.01 mmol, 0.1 equiv.), potassium chloride (0.01 mmol, 0.1 equiv.), tetramethylpiperidinium oxide (0.01 mmol, 0.1 equiv.), and 3 mL of 1,2-dichloroethane to a 10 mL screw-cap vial. After stirring at room temperature for 24 hours under an oxygen atmosphere, the mixture was diluted with dilute hydrochloric acid (4.0 M) and extracted with dichloromethane. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether / acetic acid = 1:1:0.05 (v / v / v) as the eluent to obtain compound 14 as a white solid, in an 85% yield.

[0098] Example 12 Synthesis of Compound 15

[0099] Synthesis of Compound 15 (2-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)acetic acid): Compound 15 was synthesized using Compound 13 as a raw material and referring to the preparation method of Compound 14 in Example 11.

[0100] Example 13 Synthesis of Compound 16 and Compound 17

[0101] Compound 16 (3-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)propanol) and Compound 17 (3-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)propanol) were synthesized by the following preparation methods: referring to the method of step (1) in Example 10, (2-bromoethoxy)(tert-butyl)dimethylsilane was replaced with (3-bromopropoxy)(tert-butyl)dimethylsilane to obtain N 1 and N 2 Substituted intermediates 13-1 and 13-2. Intermediates 13-1 and 13-2 were subjected to step (2) of Example 10 to give compounds 16 and 17, respectively.

[0102] Example 14 Synthesis of Compound 18

[0103] The synthesis of compound 18 (2-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)propionic acid) is as follows: Compound 18 is synthesized using compound 16 as a raw material, and compound 18 is synthesized by referring to the preparation method of compound 14 in Example 11.

[0104] Example 15 Synthesis of Compound 19

[0105] The synthesis of compound 19 (2-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)propionic acid) was carried out by using compound 17 as a raw material and synthesizing compound 19 by referring to the preparation method of compound 14 in Example 11.

[0106] Example 16 Synthesis of Compound 20 and Compound 21

[0107] Compound 20 (3-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)butanol) and Compound 21 (3-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)butanol) were synthesized by the following preparation methods: referring to the method of step (1) in Example 10, (2-bromoethoxy)(tert-butyl)dimethylsilane was replaced with (3-bromobutoxy)(tert-butyl)dimethylsilane to obtain N 1 and N 2 Substituted intermediates 16-1 and 16-2. Intermediates 16-1 and 16-2 were subjected to step (2) of Example 10 to give compounds 20 and 21, respectively.

[0108] Example 17 Synthesis of Compound 22

[0109] The synthesis of compound 22 (2-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid) is as follows: Compound 20 is used as a raw material, and compound 22 is synthesized by referring to the preparation method of compound 14 in Example 11.

[0110] Example 18 Synthesis of Compound 23

[0111] The synthesis of compound 23 (2-(6-chloro-4-ethoxy-2H-pyrazolo[4,3-c]pyridin-2-yl)butanoic acid) is as follows: Compound 21 is used as a raw material, and compound 23 is synthesized by referring to the preparation method of compound 14 in Example 11.

[0112] Example 19 Synthesis of Compound 24

[0113] The synthesis of compound 24 (ethyl 4-(6-chloro-4-ethoxy-3-(3-methoxyphenyl)-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoate) is as follows:

[0114]

[0115] The preparation method of compound 28 is:

[0116] Step 1: Synthesis of Intermediate 19-1 (4,6-dichloro-3-iodo-1H-pyrazolo[4,3-c]pyridine): A 25 mL round-bottom flask was charged with 4,6-dichloro-1H-pyrazolo[4,3-c]pyridine (2 mmol, 1.0 equiv.), potassium hydroxide (3 mmol, 1.5 equiv.), elemental iodine (6 mmol, 3.0 equiv.), and 10 mL of anhydrous 1,4-dioxane. The mixture was stirred at 80°C for 4 hours, then cooled to room temperature. Saturated sodium thiosulfate solution was added and stirring continued for 15 minutes. After dilution with water, the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, decolorized with activated carbon, filtered through a short silica gel column, and rinsed with ethyl acetate. After concentration, a small amount of n-hexane was added and stirred to precipitate a large amount of white solid. After filtration, Intermediate 19-1 was obtained (white solid, 95% yield).

[0117] Step 2: Synthesis of Intermediate 19-2: Refer to the synthesis of Intermediate 10-1 in Example 10.

[0118] Step 3: Synthesis of Intermediate 19-3: Refer to the synthesis of Intermediate 10-2 in Example 10.

[0119] Step 4: Synthesis of Intermediate 19-4: To a 10 mL screw-cap vial were added Intermediate 19-3 (1 mmol, 1.0 equiv.), ferric nitrate nonahydrate (0.1 mmol, 0.1 equiv.), potassium chloride (0.1 mmol, 0.1 equiv.), tetramethylpiperidinium oxide (0.1 mmol, 0.1 equiv.), and 3 mL of 1,2-dichloroethane. After stirring at room temperature for 24 hours under an oxygen atmosphere, the mixture was diluted with dilute hydrochloric acid (4.0 M) and extracted with dichloromethane. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether / acetic acid = 1:1:0.05 (v / v / v) as the eluent to obtain Intermediate 19-4 as a white solid, 95% yield.

[0120] Step 5: Synthesis of Intermediate 19-5: To a 10 mL screw-cap vial were added Intermediate 19-4 (1 mmol, 1.0 equiv.), iodoethane (1.5 mmol, 1.5 equiv.), potassium carbonate (1.5 mmol, 1.5 equiv.), and 3 mL of dimethyl sulfoxide. After stirring at room temperature for 24 hours, the mixture was diluted with water and extracted with ethyl acetate. The organic layer was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:1 (v / v) as the eluent to obtain Intermediate 19-5 (white solid, 75% yield).

[0121] Step 6: Synthesis of Intermediate 19-6: To a 10 mL screw-cap vial were added compound 19-5 (0.1 mmol, 1.0 equiv.), phenylboronic acid (0.15 mmol, 1.5 equiv.), tetrakistriphenylphosphine palladium (0.005 mmol, 0.05 equiv.), potassium carbonate (0.15 mmol, 1.5 equiv.), and 1,4-dioxane / toluene / water (5:5:1, volume ratio, 2 mL). After stirring at 80°C under argon for 10 hours, the insoluble matter was removed by celite and rinsed with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain the crude product, which was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:3 (v / v) as the eluent to obtain Intermediate 19-6 as a white solid, in 85% yield.

[0122] Step 7: Synthesis of Compound 24: A 10 mL round-bottom flask was charged with Intermediate 21-6 (0.05 mmol, 1.0 equiv.), lithium hydroxide monohydrate (0.15 mmol, 3 equiv.), and ethanol / water (5:1 volume ratio, 2 mL). After stirring at room temperature for 24 hours, the mixture was concentrated, added with dilute hydrochloric acid (4.0 M), extracted with ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 2:1 (v / v) as the eluent to obtain Compound 24 (white solid, 90% yield).

[0123] Example 20 Synthesis of Compound 25

[0124] Synthesis of compound 25 (4-(6-chloro-4-ethoxy-3-(pyridin-4-yl)-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid): According to the preparation method of Example 19 above, the phenylboronic acid in Step 6 of Example 19 was replaced with 4-pyridineboronic acid, and the corresponding intermediate 20-6 and compound 25 were prepared in sequence.

[0125] Example 21 Synthesis of Compound 26

[0126] The synthesis of compound 26 (4-(6-chloro-4-ethoxy-3-(phenylamino)-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid) is as follows:

[0127]

[0128] The preparation method of compound 26 is:

[0129] Step 1, Synthesis of Intermediate 21-6: To a 10 mL screw-capped vial were added Intermediate 19-5 (0.1 mmol, 1.0 equiv.), aniline (0.15 mmol, 1.5 equiv.), BrettPhos Pd G3 (0.005 mmol, 0.05 equiv.), cesium carbonate (0.15 mmol, 1.5 equiv.), and toluene. After stirring at 80°C under argon for 1 hour, the insoluble matter was removed with celite and then rinsed with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain Intermediate 21-6 (white solid, 55% yield).

[0130] Step 2, synthesis of compound 26: refer to step 7 of Example 19 for the synthesis of compound 24.

[0131] Example 22 Synthesis of Compound 27

[0132] Synthesis of compound 27 (4-(3-(benzylamino)-6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid): According to the preparation method of Example 21 above, the aniline in Step 1 of Example 21 was replaced with benzylamine, and the corresponding intermediate 22-6 and compound 27 were prepared in sequence.

[0133] Example 23 Synthesis of Compound 28

[0134] The synthesis of compound 28 (4-(6-chloro-4-ethoxy-3-(trifluoromethyl)-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid) is as follows:

[0135]

[0136] The preparation method of compound 28 is:

[0137] Step 1, Synthesis of Intermediate 23-4: To a 10 mL screw-cap vial were added Intermediate 19-3 (1 mmol, 1.0 equiv.), Chen Qingyun's reagent, methyl 2,2-difluoro-2-(fluorosulfonyl)acetate (1.5 mmol, 1.5 equiv.), cuprous iodide (1 mmol, 1 equiv.), and 4 mL of anhydrous N-dimethylformamide. After stirring at 80°C under argon for 2 hours, the mixture was diluted with water and extracted with ethyl acetate. The mixture was washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain a crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain Intermediate 23-4 (white solid, 95% yield).

[0138] Step 2, synthesis of compound 28: Compound 28 was prepared by referring to the synthesis method of compound 19-4 in step 4 of Example 19.

[0139] Example 24 Synthesis of Compound 29

[0140] The synthesis of compound 29 (4-(6-chloro-3-cyclopropyl-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)butanoic acid) is as follows:

[0141]

[0142] Step 1, Synthesis of Intermediate 24-1: A 25 mL Schlenk flask was charged with 2,4,6-trichloronicotinaldehyde (10 mmol, 1.0 equiv.) and 5 mL of anhydrous tetrahydrofuran. A solution of cyclopropylmagnesium bromide in tetrahydrofuran (12 mmol, 1.0 M, 12 mL, 1.2 equiv.) was slowly added dropwise under argon at 0°C. After stirring at room temperature for 1 hour, saturated ammonium chloride solution was added dropwise. The mixture was diluted with water and extracted with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain Intermediate 26-1 (colorless liquid, 75% yield).

[0143] Step 2, Synthesis of Intermediate 24-2: To a 25 mL round-bottom flask, intermediate 24-1 (8 mmol, 1.0 equiv.) and 15 mL of anhydrous dichloromethane were added portionwise. Dess-Martin reagent (8.8 mmol, 1.1 equiv.) was added at room temperature. After stirring at room temperature for 1 hour, saturated sodium thiosulfate solution was added dropwise. The mixture was diluted with water and extracted with dichloromethane. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain intermediate 24-2 (colorless liquid, 95% yield).

[0144] Step 3, Synthesis of Intermediate 24-3: To a 25 mL round-bottom flask were added Intermediate 24-2 (6 mmol, 1.0 equiv.), 80% hydrazine hydrate (18 mmol, 3.0 equiv.), and 15 mL of 1,4-dioxane. After stirring at 80°C for 1 hour, the mixture was diluted with water and extracted with ethyl acetate. The mixture was washed with saturated brine and dried over anhydrous sodium sulfate. The solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using ethyl acetate / petroleum ether = 1:5 (v / v) as the eluent to obtain Intermediate 24-3 (white solid, 35% yield).

[0145] Step 4, synthesis of intermediates 24-4 and 24-5: refer to Step 1 and Step 2 of Example 10, respectively.

[0146] Step 5, synthesis of compound 29: Compound 33 was prepared by referring to the preparation method of compound 14 in Example 11.

[0147] Example 25 Synthesis of Compound 30

[0148] Compound 30: Synthesis of 2-(6-chloro-4-ethoxy-1H-pyrazolo[4,3-c]pyridin-1-yl)-N-hydroxyacetamide. The reaction formula is shown below:

[0149]

[0150] Step 1, Synthesis of Intermediate 25-1: Compound 14 (1 mmol, 1.0 equiv.), EDCI (1.5 mmol, 1.5 equiv.), HOBt (1.5 mmol, 1.5 equiv.), and 2 mL of anhydrous NN-dimethylformamide were added to a 10 mL round-bottom flask. O-(Tetrahydropyran-2-yl)hydroxylamine (1.5 mmol, 1.5 equiv.) and NN-diisopropylethylamine (3.0 mmol, 3.0 equiv.) were slowly added dropwise at room temperature. After stirring at room temperature for 24 hours, saturated ammonium chloride solution was added dropwise. The mixture was diluted with water and extracted with ethyl acetate. The mixture was washed with saturated sodium bicarbonate solution and saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure to obtain the crude product 25-1, which could be directly used in subsequent reactions without purification.

[0151] Step 2: Dissolve the crude product 25-1 obtained in step 1 in 2 mL of dichloromethane, and slowly add 0.2 mL of a 4.0 M dioxane hydrochloride solution dropwise at room temperature. After vigorous stirring for 2 hours, the solvent was evaporated under reduced pressure to obtain the crude product. The crude product was purified by flash silica gel chromatography using methanol / dichloromethane = 1:10 (v / v) as the eluent to obtain compound 30 (white solid, 85% yield).

[0152] Example 28 Synthesis of Compounds 31-33

[0153] Synthesis of compounds 31-33: According to the preparation method of Example 27 above, the raw material compound 14 in step 1 of Example 27 was replaced by compounds 15, 18, and 19, respectively, and the corresponding compounds 31-33 were prepared in sequence.

[0154] Table 1 below shows the H NMR spectrum data and yields of the compounds synthesized in the above examples.

[0155] Table 1

[0156]

[0157]

[0158]

[0159]

[0160]

[0161] The following Table 2 shows the structural formulas of compounds 1-33 synthesized in the above examples.

[0162] Table 2

[0163]

[0164]

[0165]

[0166]

[0167] Test Example 1 Phosphodiesterase IV (PDE4D7) Enzyme Inhibition Activity Test

[0168] (1) Establish an in vitro screening method and model for PDE4D7 enzyme activity inhibition. The inhibitory activity of PDE4D7 kinase was detected using time-resolved fluorescence resonance energy transfer. Apremilast was used as a control drug to determine its half-maximal inhibition rate (IC) in this model. 50 The results are consistent with the IC values ​​reported in many literatures. 50 The values ​​are similar, indicating that the screening model was successfully constructed.

[0169] (2) Compounds 1 to 33 prepared in the above examples were dissolved in DMSO to prepare a 10 mM stock solution, which was then diluted with DMSO in a gradient manner and added to the final reaction system, ensuring that the DMSO concentration was less than 1%. The PDE4D7 enzyme reaction system consists of PDE4D7 enzyme, BSA (bovine serum albumin), PDE4D7-specific fluorescent substrate FAM-cAMP, reaction buffer, etc. After all components are mixed together, the reaction is carried out at room temperature for 60 minutes. After the reaction is completed, a specific phosphate-binding antibody is added and the reaction is incubated at room temperature for another 60 minutes. The fluorescence polarization signal is then detected on a SpectraMax M5 multifunctional microplate reader from MD Corporation, with an excitation wavelength of 485 nm and an emission wavelength of 528 nm. The values ​​are substituted into the following formula to calculate the percentage of activity: % activity = {(FP drug - FP background) / (FP enzyme - FP background)} × 100%.

[0170] IC analysis of compounds 1 to 3350 The inhibitory activity (IC) of compounds 1 to 33 on PDE4D7 was tested by Prism GraphPad software using nonlinear regression and normalization to fit the dose-effect curve. 50 , nM), among which, the IC values ​​of compound 19 and compound 22 50 Value Figure 1 and Figure 2 shown.

[0171] Table 3

[0172] Compound Test Number <![CDATA[PDE4IC 50 (nM)]]> Compound Test Number <![CDATA[PDE4IC 50 (nM)]]> 1 Z21049 90 18 Z21088 315.2 2 Z21057 167.9 19 Z21089 26.0 3 Z21050 >1000 20 Z21084 >1000 4 Z21051 >1000 21 Z21085 >1000 5 Z21083 >1000 22 Z21090 37.6 6 Z21063 >1000 23 Z21091 >1000 7 Z21064 >1000 24 Z21167 >1000 8 Z21069 >1000 25 Z21166 287.9 9 Z21071 >1000 26 Z21171 >1000 10 Z21072 198.5 27 Z21172 >1000 11 Z20174 >1000 28 Z21161 76.3 12 Z21079 >1000 29 Z21163 >1000 13 Z21080 >1000 30 Z21092 16.6 14 Z21086 >1000 31 Z21093 20.2 15 Z21087 >1000 32 Z21094 208.5 16 Z21081 >1000 33 Z21095 38.7 17 Z21082 60.6 34 Apremilast 10±1

[0173] All data are the average of three experiments.

[0174] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof, characterized in that: The pyrazolo[4,3-c]pyridine compound is selected from any of the following structures:

2. The pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof according to claim 1, characterized in that: The pyrazolo[4,3-c]pyridine compound is selected from any of the following structures:

3. A pharmaceutical composition, characterized in that The invention comprises the pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 2; and a pharmaceutically acceptable carrier and / or excipient.

4. Use of the pyrazolo[4,3-c]pyridine compound or a pharmaceutically acceptable salt thereof according to any one of claims 1 to 2 or the pharmaceutical composition according to claim 3 in the preparation of a cyclic nucleotide phosphodiesterase inhibitor, characterized in that: The cyclic nucleotide phosphodiesterase is cyclic nucleotide phosphodiesterase 4.

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