1,3,4-Oxadiazole Derivative Compounds as Histone Deacetylase 6 Inhibitors and Uses Thereof

Abstract

The present invention relates to a novel compound having histone deacetylase 6 (HDAC6) inhibitory activity, a method for producing the same, and use thereof. The novel compound according to the present invention, its stereoisomer, or a pharma- ceutically acceptable salt thereof has HDAC6 inhibitory activity and is effective in preventing or treating HDAC6-related diseases, including cancer, inflammatory diseases, autoimmune diseases, and nervous system or neurodegenerative diseases.

Description

[Technical field]

[0001] The present invention relates to a 1,3,4-oxadiazole derivative compound having histone deacetylase 6 (HDAC6) inhibitory activity, a production method thereof, and uses thereof. [Background technology]

[0002] In cells, post-translational modifications such as acetylation are very important regulatory modules at the center of biological processes and are tightly controlled by a large number of enzymes. Histones are the central proteins that make up chromatin, which act as the axis around which DNA wraps and help DNA condense. The balance between acetylation and deacetylation of histones also plays a very important role in gene expression.

[0003] Histone deacetylases (HDACs) are enzymes that remove acetyl groups from lysine residues of histone proteins that constitute chromatin. They are known to be involved in gene silencing and induce cell cycle arrest, angiogenesis inhibition, immune regulation, cell death, etc. (Hassig et al., Curr. Opin. Chem. Biol. 1997, 1, 300-308). It has also been reported that inhibition of HDAC enzyme function reduces the activity of factors related to the survival of cancer cells in vivo and activates factors related to the death of cancer cells, thereby inducing the death of cancer cells themselves (Warrell et al., J. Natl. Cancer Inst. 1998, 90, 1621-1625).

[0004] In humans, 18 HDAC enzymes are known, and they are divided into four classes based on their homology with yeast HDACs. The 11 HDACs that use zinc as a cofactor are divided into three classes: Class I (HDAC1,2,3,8), Class II (IIa:HDAC4,5,7,9; IIb:HDAC6,10), and Class IV (HDAC11). In addition, seven HDACs in Class III (SIRT 1-7) use NAD instead of zinc. + as a cofactor (Bolden et al., Nat. Rev. Drug. Discov. 2006, 5(9), 769-784).

[0005] Although various HDAC inhibitors are in preclinical or clinical development, only nonselective HDAC inhibitors are known as anticancer drugs. Vorinostat (SAHA) and romidepsin (FK228) are approved as treatments for cutaneous T-cell lymphoma, and panobinostat (LBH-589) is approved as a treatment for multiple myeloma. However, nonselective HDACs inhibitors are known to cause side effects such as fatigue and vomiting at high doses (Piekarz et al., Pharmaceuticals 2010,3,2751-2767). These side effects have been reported to be due to inhibition of class I HDACs, and due to these side effects and other factors, non-selective HDACs inhibitors have limited the development of drugs in areas other than anticancer drugs (Witt et al., Cancer Letters 277 (2009) 8.21).

[0006] On the other hand, it has been reported that selective class II HDAC inhibition does not exhibit the toxicity seen with class I HDAC inhibition. Therefore, the development of selective HDAC inhibitors could eliminate the side effects such as toxicity caused by non-selective HDAC inhibition, and selective HDAC inhibitors may be developed as effective therapeutic agents for a variety of diseases (Matthias et al., Mol. Cell. Biol. 2008, 28, 1688-1701).

[0007] HDAC6, one of the Class IIb HDACs, is mainly present in the cytoplasm and is known to be involved in the deacetylation of many non-histone substrates (HSP90, cortactin, etc.) including tubulating proteins (Yao et al., Mol. Cell 2005, 18, 601-607). HDAC6 has two catalytic domains, and the zinc finger domain at the C-terminus can bind to ubiquitinated proteins. HDAC6 has many non-histone proteins as substrates and is therefore known to play important roles in a variety of diseases, including cancer, inflammatory diseases, autoimmune diseases, neurological diseases, and neurodegenerative disorders (Santo et al., Blood 2012 119:2579-258; Vishwakarma et al., International Immunopharmacology 2013, 16, 72-78; Hu et al., J. Neurol. Sci. 2011, 304, 1-8).

[0008] The common structural features of various HDAC inhibitors are the cap group, linker group, and zinc binding group (ZBG), as shown in the following structure of vorinostat. Many researchers have studied the enzyme inhibitory activity and selectivity through the structural modification of the cap group and linker group. Among them, the zinc binding group is known to play a more important role in enzyme inhibitory activity and selectivity (Wiest et al., J. Org. Chem. 2013 78:5051-5065; Methot et al., Bioorg. Med. Chem. Lett. 2008, 18, 973-978). [ka]

[0009] Most of the zinc-binding groups are hydroxamic acids or benzamides, among which hydroxamic acid derivatives show strong HDAC inhibitory effects, but have problems with low bioavailability and serious off-target activity. Benzamides contain aniline, which can generate toxic metabolites in vivo (Woster et al., Med. Chem. Commun. 2015, online publication).

[0010] Therefore, unlike non-selective inhibitors that have side effects, the development of selective HDAC6 inhibitors having a zinc-binding group that are free of side effects and have improved bioavailability is required for the treatment of cancer, inflammatory diseases, autoimmune diseases, neurological diseases, and neurodegenerative disorders. Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a 1,3,4-oxadiazole derivative compound, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof, which has selective histone deacetylase 6 (HDAC6) inhibitory activity. Another object of the present invention is to provide a pharmaceutical composition comprising a 1,3,4-oxadiazole derivative compound, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof having selective HDAC6 inhibitory activity.

[0012] Another object of the present invention is to provide a method for producing these. Another object of the present invention is to provide a pharmaceutical composition comprising said compound for the prevention or treatment of diseases associated with HDAC6 activity, including infectious diseases, neoplasms, endocrine, nutritional and metabolic diseases, mental and behavioral disorders, neurological diseases, eye and eye adnexal diseases, cardiovascular diseases, respiratory diseases, gastrointestinal diseases, diseases of the skin and subcutaneous tissue, diseases of the musculoskeletal system and connective tissue, or congenital malformations, deformities and chromosomal abnormalities. Another object of the present invention is to provide the use of said compounds for the manufacture of a medicament for the prevention or treatment of diseases associated with HDAC6 activity. Another object of the present invention is to provide a method for the treatment of diseases associated with HDAC6 activity comprising the administration of a therapeutically effective amount of a pharmaceutical composition comprising said compound. [Means for solving the problem]

[0013] The present inventors have discovered a 1,3,4-oxadiazole derivative compound having histone deacetylase 6 (HDAC6) inhibitory activity, and have completed the present invention by using the compound for inhibiting or treating diseases associated with HDAC6 activity.

[0014] 1,3,4-Oxadiazole derivative compounds In accordance with the above object, the present invention provides a 1,3,4-oxadiazole derivative compound represented by the following formula I, a stereoisomer thereof, or a pharma- ceutically acceptable salt thereof: [ka] (Formula I) In the above formula I, R1 and R2 are each independently -(C1-C4 alkyl), or R1 and R2 are linked together to form a heterocycloalkyl together with the N atom, wherein one or more H of the heterocycloalkyl ring are each independently optionally replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -halo, or heterocycloalkyl; X is -H or -F; Y1 to Y5 each independently represent N or CR3, and Y1 to Y5 cannot simultaneously represent three or more N's; R3 is -H, -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -halo, aryl, or heteroaryl, where one or more -H in the aryl or heteroaryl ring are each optionally and independently replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -OH, -O(C1-C4 alkyl), or -halo; Z1 to Z4 are each independently N or CR4, where Z1 to Z4 cannot simultaneously be three or more N's; and R4 is -H, -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -halo, aryl, or heteroaryl, where one or more -H on the aryl or heteroaryl ring are each optionally and independently replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -OH, -O(C1-C4 alkyl), or -halo.

[0015] According to an embodiment of the present invention, the compound represented by formula I, its stereoisomer, or a pharma- ceutically acceptable salt thereof may be in the following ranges: R1 and R2 are linked together to form a heterocycloalkyl together with the N atom, wherein one or more H of the heterocycloalkyl ring may each be independently replaced with -(C1-C4 alkyl) or heterocycloalkyl; X is -H or -F; Y1 to Y5 each independently represent CR3; R3 is -H, -halo, or heteroaryl, where one or more -H on the heteroaryl ring are each optionally and independently substituted with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -OH, -O(C1-C4 alkyl), or -halo; Z1 to Z4 are each independently N or CR4, where Z1 to Z4 cannot simultaneously be three or more N's; and R4 is -H or -halo.

[0016] According to an embodiment of the present invention, the compound represented by formula I, its stereoisomer, or a pharma- ceutically acceptable salt thereof may be in the following ranges: R1 and R2 are linked together to form a 4-12 membered heterocycloalkyl together with the N atom, wherein one or more H of the heterocycloalkyl ring are each independently optionally replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), -halo, or a 3-6 membered heterocycloalkyl.

[0017] According to an embodiment of the present invention, the compound represented by formula I, its stereoisomer, or a pharma- ceutically acceptable salt thereof may be in the following ranges: R1 and R2 are linked to each other and together with the N atom [ka] where: [ka] One or more H in the ring may each be independently replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), or -halo; W is NR5, O, S, or S(=O)2; R5 is -(C1-C4 alkyl) or 3-6 membered heterocycloalkyl; and n1, n2, m1 and m2 are each independently 0, 1 or 2.

[0018] According to an embodiment of the present invention, the compound represented by formula I, its stereoisomer, or a pharma- ceutically acceptable salt thereof may be in the following ranges: R1 and R2 are linked to each other and together with the N atom [ka] wherein said [ka] One or more H in the ring may each be independently replaced with -(C1-C4 alkyl), -(C1-C4 aminoalkyl), -(C1-C4 hydroxyalkyl), -(C1-C4 haloalkyl), or -halo; and R5 is -(C1-C4 alkyl) or [ka] It is.

[0019] Furthermore, according to an embodiment of the present invention, specific compounds represented by formula I of the present invention are as shown in Table 1 below: [Table 1] JPEG2025512815000009.jpg199158

[0020] In the present invention, "alkyl" can mean a straight or branched chain, acyclic, cyclic or combined saturated hydrocarbon, unless otherwise specified. For example, "C 1-4 "Alkyl" may mean an alkyl containing 1 to 4 carbon atoms. Non-cyclic alkyl may include, by way of example and not limited to, methyl, ethyl, n-propyl, n-butyl, isopropyl, secondary (sec)-butyl, isobutyl, or tertiary (tert)-butyl, and the like. Cyclic alkyl may be used interchangeably with "cycloalkyl" herein, and by way of example and not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, or cyclooctyl, and the like.

[0021] In the present invention, "alkoxy" can refer to an alkyl ether group, -(O-alkyl), where alkyl is as defined above. For example, "C 1-4 "Alkoxy" is C 1-4 Alkoxy containing an alkyl group, i.e., -(OC 1-4 Alkyl, by way of example only, alkoxy can include, but is not limited to, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, or tert-butoxy, and the like.

[0022] In the present invention, "halo" may be F, Cl, Br, or I. In the present invention, the term "haloalkyl" can refer to a straight or branched chain alkyl (hydrocarbon) having one or more carbon atoms substituted with halo as defined herein. Examples of said haloalkyl include, but are not limited to, methyl, ethyl, propyl, isopropyl, isobutyl, or n-butyl, each independently substituted with one or more halogens, such as F, Cl, Br, or I.

[0023] In the present invention, "hydroxyalkyl" can refer to a straight or branched chain alkyl (hydrocarbon) having a carbon atom substituted with -OH. Examples of hydroxyalkyl include, but are not limited to, methyl, ethyl, propyl, isopropyl, isobutyl, or n-butyl, each independently substituted with one or more hydroxy groups. As used herein, an "aminoalkyl" can refer to a straight or branched chain alkyl (hydrocarbon) having a carbon atom substituted with amino-(NR'R"), where R' and R" are each independently hydrogen and C 1-4alkyl, wherein each selected R' and R'' may be independently substituted or unsubstituted.

[0024] In the present invention, the term "heterocycloalkyl" refers to a ring containing 1 to 5 heteroatoms selected from N, O, and S, which may be saturated or partially unsaturated. When unsaturated, it may be referred to as a heterocycloalkene. Unless otherwise specified, the heterocycloalkyl may be a single ring or a polycyclic ring such as a spiro ring, a bridged ring, or a fused ring. In addition, the term "heterocycloalkyl having 3 to 12 atoms" refers to a heterocycloalkyl containing 3 to 12 atoms forming a ring. For example, the heterocycloalkyl may be pyrrolidine, piperidine, imidazolidine, pyrazolidine, butyrolactam, valerolactam, imidazolidinone, hydantoin, dioxolane, phthalimide, piperidine, pyrimidine-2,4(1H,3H)-dione, 1,4-dioxane, morpholine, thiomorpholine, thiomorpholine-S-oxide ... These may include, but are not limited to, omorpholine-S,S-oxide, piperazine, pyran, pyridone, 3-pyrroline, thiopyran, pyrone, tetrahydrofuran, tetrahydrothiophene, quinuclidine, tropane, 2-azaspiro[3.3]heptane, (1R,5S)-3-azabicyclo[3.2.1]octane, (1s,4s)-2-azabicyclo[2.2.2]octane, or (1R,4R)-2-oxa-5-azabicyclo[2.2.2]octane, and the like.

[0025] In the present invention, "arene" can mean an aromatic hydrocarbon ring. The allene may be a monocyclic allene or a polycyclic allene. The number of ring carbon atoms of the allene may be 5 to 30, 5 to 20, or 5 to 15. Examples of allene include, but are not limited to, benzene, naphthalene, fluorene, anthracene, phenanthrene, bibenzene, terbenzene, quaterbenzene, quinquebenzene, sexibenzene, triphenylene, pyrene, benzofluoranthene, and chrysene. In this specification, the residue obtained by removing one hydrogen atom from the "allene" is called "aryl".

[0026] The "heteroarene" in the present invention may be a ring containing one or more of O, N, P, Si, and S as heteroelements. The number of ring carbon atoms of the heteroarene may be 2 to 30 or 2 to 20. The heteroarene may be a monocyclic heteroarene or a polycyclic heteroarene. The polycyclic heteroarene may have, for example, a two- or three-ring structure. Examples of heteroarenes include thiophene, purine, pyrrole, pyrazole, imidazole, thiazole, oxazole, isothiazole, oxadiazole, triazole, pyridine, bipyridyl, triazine, acridyl, pyridazine, pyrazine, quinoline, quinazoline, quinoxaline, phenoxazine, phthalazine, pyrimidine, pyridopyrimidine, pyridopyrazine, pyrazinopyrazine, isoquinoline, indole, carbazole, imidazopyridazine, imidazopyridine, imidazopyrimidine, pyrazolopyrimidine, These include, but are not limited to, imidazopyrazine or pyrazolopyridine, N-arylcarbazole, N-heteroarylcarbazole, N-alkylcarbazole, benzoxazole, benzimidazole, benzothiazole, benzocarbazole, benzothiophene, dibenzothiophene, thienothiophene, benzofuran, phenanthroline, isoxazole, oxadiazole, thiadiazole, benzothiazole, tetrazole, phenothiazine, dibenzosilole and dibenzofuran. In one embodiment of the present invention, the heteroarene can also include bicyclic heterocyclo-arenes, including an arene ring fused to a heterocycloalkyl ring or a heteroarene fused to a cycloalkyl ring. In this specification, the residue obtained by removing one of the hydrogen atoms from the "heteroarene" is referred to as "heteroaryl".

[0027] The compounds of formula I of the present invention may contain one or more asymmetric carbons, and thus may exist as racemates, racemic mixtures, single enantiomers, diastereomeric mixtures, and individual diastereomers. Such stereoisomers can be separated by conventional techniques, for example, the compounds of formula I can be separated by resolution, such as column chromatography or HPLC. Alternatively, each stereoisomer of the compounds of formula I can be stereospecifically synthesized using optically pure starting materials and / or reagents of known sequence.

[0028] As used herein, the term "enantiomer" refers to a compound of the present invention or a salt thereof that has the same formula or molecular formula but is sterically different. Each such enantiomer and mixtures thereof are also included within the scope of the present invention. Unless otherwise indicated, a solid bond (-) connected to an asymmetric carbon atom is replaced by a solid wedge bond indicating the absolute configuration of the stereocenter. [ka] or dashed wedge bond [ka] may include.

[0029] The compound of formula I in the present invention can exist in the form of a "pharmaceutical acceptable salt". As the salt, an acid addition salt formed with a pharmaceutical acceptable free acid is useful. In the present invention, the term "pharmaceutical acceptable salt" refers to any organic or inorganic acid addition salt of the compound represented by formula I at a concentration that is relatively non-toxic and harmless to the patient and has an effective effect, and the side effects caused by the salt do not reduce the beneficial efficacy of the compound represented by formula I.

[0030] The acid addition salts are prepared in the usual manner, for example by dissolving the compound in an excess of aqueous acid and precipitating the salt with a water-miscible organic solvent, for example methanol, ethanol, acetone or acetonitrile. Equal molar amounts of the compound and the acid or alcohol in water are heated, and then the mixture is evaporated to dryness or the precipitated salt can be filtered off with suction.

[0031] In this case, the free acid may be an organic acid or an inorganic acid, and the inorganic acid may be hydrochloric acid, phosphoric acid, sulfuric acid, or nitric acid, and the organic acid may be methanesulfonic acid, p-toluenesulfonic acid, acetic acid, trifluoroacetic acid, maleic acid, succinic acid, oxalic acid, benzoic acid, tartaric acid, fumaric acid, mandelic acid, propionic acid, citric acid, lactic acid, glycolic acid, gluconic acid, galacturonic acid, glutamic acid, glutaric acid, glucuronic acid, aspartic acid, ascorbic acid, carboxylic acid, vanillic acid, or hydroiodic acid, but is not limited thereto.

[0032] Pharmaceutically acceptable metal salts can also be prepared using bases. Alkali metal salts or alkaline earth metal salts can be obtained, for example, by dissolving the compound in a solution of excess alkali metal hydroxide or alkaline earth metal hydroxide, filtering the salt of the undissolved compound, and evaporating and drying the filtrate. In this case, as the metal salt, it is particularly suitable to prepare sodium, potassium, or calcium salts, but this is not limited thereto. Corresponding silver salts can also be obtained by reacting alkali metal or alkaline earth metal salts with a suitable silver salt (e.g., silver nitrate).

[0033] The pharma- ceutically acceptable salts of the present invention, unless otherwise specified, include salts of acidic or basic groups that may be present in the compounds of formula I. For example, pharma- ceutically acceptable salts may include sodium, calcium, and potassium salts of hydroxy groups, and other pharma- ceutically acceptable salts of amino groups include hydrobromide, sulfate, hydrogen sulfate, phosphate, hydrogen phosphate, dihydrogen phosphate, acetate, succinate, citrate, tartrate, lactate, mandelate, methanesulfonate (mesylate), and p-toluenesulfonate (tosylate), which may be prepared by methods for preparing salts known in the art.

[0034] Method for producing 1,3,4-oxadiazole derivative compound The present invention provides a method for producing a 1,3,4-oxadiazole derivative compound represented by the following formula I, a stereoisomer thereof, or a pharma- ceutically acceptable salt thereof. [ka] The formula I is as defined above. In the present invention, preferred methods for producing the oxadiazole derivative compound represented by the above formula I, its stereoisomer or its pharma- ceutically acceptable salt are as shown in the following [Reaction Scheme 1] to [Reaction Scheme 4], and include preparation methods modified to a level obvious to those skilled in the art. [ka]

[0035] The above [Reaction Scheme 1] is a method for synthesizing a 1,3,4-oxadiazole derivative compound having a cyclobutenedione structure. First, a compound of formula 1-1 containing an amine group is reacted with a compound of formula 1-2 to produce a compound of formula 1-3 containing an amine substituent. Then, the compound of formula 1-3 is reacted with a compound of formula 1-4 to produce a compound of formula 1-5 having a cyclobutenedione structure containing a diamine substituent. The compound of formula 1-5 is subjected to a substitution reaction with a compound of formula 1-6 to produce a compound of formula 1-7. The compound of formula 1-5 can also be produced by reacting a compound of formula 1-4 with a compound of formula 1-2 to produce a compound of formula 1-8, and then reacting the compound with a compound of formula 1-1. In the present invention, compounds 2, 3, 4, 5, 6, 7, 10, and 24 can be produced through the above Reaction Scheme 1. [ka]

[0036] The above [Reaction Scheme 2] is another method for synthesizing a 1,3,4-oxadiazole derivative compound having a cyclobutenedione structure. First, a compound of formula 2-1 is reacted with a compound of formula 1-2 to produce a compound of formula 2-2 containing an amine substituent. Then, the compound of formula 2-2 is reacted with a compound of formula 1-4 to produce a compound of formula 1-7 having a cyclobutenedione structure containing a diamine substituent. In the present invention, compound 1, etc. can be produced through the above Reaction Scheme 2. [ka]

[0037] The above [Reaction Scheme 3] is another method for synthesizing 1,3,4-oxadiazole derivative compounds having a cyclobutenedione structure. The compound of formula 3-2 is prepared by CC coupling (Suzuki reaction) between the compound of formula 1-7 prepared in [Reaction Scheme 1] and the compound of formula 3-1. In the present invention, compounds 8 and 9 can be prepared through the above Reaction Scheme 3. [ka]

[0038] The above [Reaction Scheme 4] is another method for synthesizing 1,3,4-oxadiazole derivative compounds having a cyclobutenedione structure. The compound of formula 4-1 having a protecting group prepared in [Reaction Scheme 1] is deprotected to prepare a compound of formula 4-2. Then, a compound of formula 4-3 is prepared using an alkylation reaction or a reduction reaction. A compound of formula 4-4 is prepared by CC coupling (Suzuki reaction) between the compound of formula 4-3 and the compound of formula 3-1. In the present invention, compounds of formula 4-3 such as 10, 11, 12, 13, 14, 15, 16, 17, 20, 21, 22 and 23 can be prepared through the above Reaction Scheme 4, and compounds of formula 4-4 such as 18 and 19 can be prepared.

[0039] Uses of 1,3,4-oxadiazole derivatives The present invention provides use of a compound represented by the following formula I, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof. [ka] The formula I is as defined above.

[0040] According to one embodiment of the present invention, there is provided a pharmaceutical composition for preventing or treating a disease associated with histone deacetylase 6 activity, comprising as an active ingredient a compound represented by formula I, a stereoisomer thereof, or a pharma- ceutical acceptable salt thereof. The pharmaceutical composition of the present invention selectively inhibits histone deacetylase 6, thereby exhibiting a remarkable effect in preventing or treating a disease associated with histone deacetylase 6 activity.

[0041] The diseases associated with histone deacetylase 6 activity include infectious diseases such as prion diseases; neoplasms such as benign tumors (e.g., myelodysplastic syndromes) or malignant tumors (e.g., multiple myeloma, lymphoma, leukemia, lung cancer, colorectal cancer, colon cancer, prostate cancer, urothelial cell cancer, breast cancer, melanoma, skin cancer, liver cancer, brain cancer, stomach cancer, ovarian cancer, pancreatic cancer, head and neck cancer, oral cancer, or glioma); endocrine, nutritional, and metabolic diseases such as Wilson's disease, amyloidosis, or diabetes; mental and behavioral disorders such as depression and Rett's syndrome; central nervous system atrophy (e.g., Huntington's disease, spinal muscular atrophy (SMA), spinocerebellar ataxia (SCA)), neurodegenerative diseases (e.g., Alzheimer's disease), movement disorders (e.g., Parkinson's disease), neurological disorders (e.g., hereditary neuropathy (SCA)). neurological diseases such as Charcot-Marie-Tooth disease, sporadic neuropathy, inflammatory neuropathy, drug-induced neuropathy, motor neuron disease (e.g., amyotrophic lateral sclerosis (ALS)), or central nervous system demyelinating diseases (e.g., multiple sclerosis (MS)); eye and ocular adnexal diseases such as uveitis; cardiovascular diseases such as atrial fibrillation or stroke; respiratory diseases such as asthma; gastrointestinal diseases such as alcoholic liver disease, inflammatory bowel disease, Crohn's disease or ulcerative bowel disease; skin and subcutaneous tissue diseases such as psoriasis; diseases of the musculoskeletal system and connective tissue such as rheumatoid arthritis, osteoarthritis or systemic lupus erythematosus (SLE); or congenital malformations, deformities and chromosomal abnormalities such as autosomal dominant polycystic kidney disease, and further including conditions or diseases associated with abnormal function of histone deacetylase.

[0042] The stereoisomers and pharma- ceutically acceptable salts thereof are as described above in the stereoisomers and pharma- ceutically acceptable salts of the compounds of formula I of the present invention.

[0043] The pharmaceutical composition of the present invention may further comprise one or more pharma- ceutically acceptable carriers in addition to the compound represented by formula I, its stereoisomers or its pharma- ceutically acceptable salts for administration. The pharma- ceutically acceptable carrier may be saline, sterile water, Ringer's solution, buffered saline, dextrose solution, maltodextrin solution, glycerol, ethanol, or a mixture of one or more of these components, and other conventional additives such as antioxidants, buffers, bacteriostatic agents, etc. may be added as necessary. In addition, diluents, dispersants, surfactants, binders and lubricants may be further added to the composition to be formulated into injection forms such as aqueous solutions, suspensions, emulsions, pills, capsules, granules or tablets. Thus, the composition of the present invention may be a patch, liquid, pill, capsule, granule, tablet, suppository, etc. These preparations may be prepared by conventional methods used in the art for formulation or by methods disclosed in Remington's Pharmaceutical Science (latest edition), Mack Publishing Company, Easton PA, and may be formulated into various preparations according to each disease or component.

[0044] The composition of the present invention can be administered orally or parenterally (e.g., intravenously, subcutaneously, intraperitoneally, or topically) depending on the intended method, and the dosage range varies depending on the patient's weight, age, sex, health condition, diet, administration time, administration method, excretion rate, and severity of disease, etc. The daily dosage of the compound represented by formula I of the present invention is about 1 to 1000 mg / kg, preferably 5 to 100 mg / kg, and can be administered once or several times a day. The pharmaceutical composition of the present invention may further contain one or more active ingredients exhibiting the same or similar pharmacological effects in addition to the compound represented by formula I, its stereoisomer or a pharma- ceutically acceptable salt thereof.

[0045] According to a specific embodiment of the present invention, there is provided a method for preventing or treating a disease associated with histone deacetylase 6 activity, comprising administering a therapeutically effective amount of a compound represented by formula I, its stereoisomer or a pharma- ceutically acceptable salt thereof to a subject in need thereof. The subject may be a mammal, including a human.

[0046] The method for preventing or treating a disease associated with histone deacetylase 6 activity of the present invention includes not only treating the disease itself before the onset of symptoms, but also inhibiting or avoiding the symptoms by administering the compound represented by formula I, its stereoisomer or a pharma- ceutically acceptable salt thereof. In addition, the method for preventing or treating a disease associated with histone deacetylase 6 activity of the present invention may further include administering a therapeutically effective amount of an additional active agent useful for treating the disease together with the compound represented by formula I, and the additional active agent may exhibit a synergistic or supplementary effect together with the compound represented by formula I.

[0047] The term "therapeutically effective amount" used in the present invention refers to an amount of the compound represented by formula I that is effective in treating or preventing a disease associated with histone deacetylase 6 activity. Specifically, "therapeutically effective amount" means an amount sufficient to treat a disease with a reasonable benefit / risk ratio applicable to medical treatment, and the effective dose level can be determined by factors including the type and severity of the individual, age, sex, type of disease, drug activity, sensitivity to the drug, administration time, administration route and excretion rate, treatment period, drugs used simultaneously, and other factors well known in the medical field. The pharmaceutical composition of the present invention can be administered as an individual therapeutic agent or in combination with other therapeutic agents, and can be administered sequentially or simultaneously with commercially available therapeutic agents. It can also be administered in a single dose or multiple doses. It is important to administer an amount that can obtain the maximum effect with the minimum amount without side effects, taking all of the above factors into consideration, and this can be easily determined by those skilled in the art. The dosage of the pharmaceutical composition of the present invention can be determined by a specialist depending on various factors such as the patient's condition, age, sex, and complications. The active ingredient of the pharmaceutical composition of the present invention is excellent in safety, so it can be used even at a dose higher than the determined dose.

[0048] According to one embodiment of the present invention, the present invention provides a method for selectively inhibiting histone deacetylase 6 (HDAC6) by administering a compound represented by formula I, a stereoisomer thereof, or a pharma- ceutically acceptable salt thereof to a mammal, including a human.

[0049] According to one embodiment of the present invention, the present invention provides the use of the compound represented by formula I, its stereoisomer or its pharma- ceutically acceptable salt for the preparation of a medicament for treating a disease associated with the activity of histone deacetylase 6. The compound represented by formula I for the preparation of the medicament may be mixed with an acceptable auxiliary agent, diluent, carrier, etc., and may be prepared as a composite preparation together with other active agents, and may have a synergistic effect of the active ingredients. The descriptions of the uses, compositions, and methods of treatment of the present invention apply equally to the same extent unless they contradict each other.

[0050] The embodiments of the present invention can be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Moreover, the embodiments of the present invention are provided to more completely explain the present invention to those having average knowledge in the art. Furthermore, throughout the specification, "including" a certain component does not exclude other components, and means that other components can be further included, unless otherwise specified to the contrary. Effect of the Invention

[0051] The compound represented by formula I of the present invention, its stereoisomer or its pharma- ceutical acceptable salt can selectively inhibit HDAC6, and therefore has a significantly excellent preventive or therapeutic effect on diseases associated with histone deacetylase 6 activity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0052] The present invention will be described in more detail with reference to the following examples and experimental examples. However, these examples are merely illustrative of the present invention and the scope of the present invention is not limited to these examples.

[0053] Preparation of 1,3,4-oxadiazole derivative compounds A specific method for producing the compound represented by formula I is as follows. EXAMPLES

[0054] EXAMPLES

[0055] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 1) [Step 1] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione [ka] N-(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)aniline (0.200 g, 0.626 mmol) and 3,4-dimethoxycyclobut-3-ene-1,2-dione (0.098 g, 0.689 mmol) were dissolved in methanol (5 mL) at room temperature and stirred at 60 °C for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. The reaction mixture was filtered through a glass filter, and the filtrate from which the solids had been removed was subjected to reduced pressure to remove the solvent. The concentrate was purified and concentrated by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 10% to 50%) to obtain the title compound (0.069 g, 25.7%) as a yellow oil.

[0056] [Step 2] Synthesis of compound 1 [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione (0.100 g, 0.233 mmol) and 1-methylpiperazine (0.052 mL, 0.466 mmol) were dissolved in methanol (3 mL) at room temperature and stirred at 60° C. for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. After removing the solvent from the reaction mixture under reduced pressure, the concentrate was purified and concentrated by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) to obtain the title compound (0.016 g, 13.8%) as a pale yellow solid. 1H NMR(400 MHz,CDCl3)δ 7.88(d,J=8.0 Hz,1H), 7.77(d,J=8.7 Hz,1H), 7.63(t,J=7.5 Hz,1H), 7.36(t,J=7.9 Hz,2H), 7.19(t,J=7.4 Hz,1H), 7.04-6.79(m,3H), 5.58(s,2H), 3.28(brs,4H), 2.25(brs,4H), 2.22(s,3H);LRMS(ES)m / z 498.5(M + +1). EXAMPLES

[0057] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-morpholinocyclobut-3-ene-1,2-dione (compound 2) [Step 1] Synthesis of 3-morpholino-4-(phenylamino)cyclobut-3-ene-1,2-dione [ka] A solution of 3-methoxy-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.500 g, 2.461 mmol), morpholine (0.213 mL, 2.461 mmol) and N,N-diisopropylethylamine (0.429 mL, 2.461 mmol) dissolved in methanol (10 mL) at 50° C. was stirred at room temperature for 2 hours. Water was poured into the reaction mixture, and it was extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, then filtered and concentrated under reduced pressure. Diethyl ether was added to the concentrate, and the precipitated solid was filtered by stirring, washed with diethyl ether and dried to obtain the title compound (0.445 g, 70.0%) as a white solid.

[0058] [Step 2] Synthesis of compound 2 [ka] 3-morpholino-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.100 g, 0.387 mmol) prepared in step 1 and sodium hydride (60.00%, 0.017 g, 0.426 mmol) were dissolved in N,N-dimethylformamide (3 mL) at 0° C., to which 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.131 g, 0.426 mmol) was added and stirred at room temperature for 1 hour. The reaction mixture was removed from the solvent under reduced pressure, and a saturated aqueous solution of sodium bicarbonate was poured into the resulting concentrate, followed by extraction with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 20% to 70%) and concentrated to give the title compound (0.019 g, 10.1%) as a white solid. 1 H NMR(400 MHz,CDCl3)δ 7.88(d,J=8.1 Hz,1H), 7.77(d,J=10.1 Hz,1H), 7.64(t,J=7.6 Hz,1H), 7.38(t,J=7.8 Hz,2H), 7.22(t,J=7.4 Hz,1H), 7.05-6.79(m,3H), 5.59(s,2H), 3.52-3.50(m,4H), 3.26(brs,4H);LRMS(ES)m / z 485.4(M + +1). EXAMPLES

[0059] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(1,1-dioxidothiomorpholino)cyclobut-3-ene-1,2-dione (compound 3) [Step 1] Synthesis of 3-(1,1-dioxidethiomorpholino)-4-(phenylamino)cyclobut-3-ene-1,2-dione [ka] A solution of 3-methoxy-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.500 g, 2.461 mmol), thiomorpholine 1,1-dioxide (0.333 g, 2.461 mmol) and N,N-diisopropylethylamine (0.429 mL, 2.461 mmol) dissolved in methanol (10 mL) at 50°C was stirred at room temperature for 4 hours. Water was poured into the reaction mixture, and it was extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, then filtered and concentrated under reduced pressure. The precipitated solid was filtered, washed with methanol and dried to obtain the title compound (0.554 g, 73.5%) as a pale yellow solid.

[0060] [Step 2] Synthesis of compound 3 [ka] 3-(1,1-dioxidethiomorpholino)-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.100 g, 0.326 mmol) and sodium hydride (60.00%, 0.014 g, 0.359 mmol) prepared in step 1 were dissolved in N,N-dimethylformamide (3 mL) at 0° C., to which 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.110 g, 0.359 mmol) was added and stirred at room temperature for 1 hour. The solvent was removed from the reaction mixture under reduced pressure, and a saturated aqueous solution of sodium chloride was poured into the resulting concentrate, which was then extracted with dichloromethane. The organic layer was washed with a saturated aqueous solution of sodium chloride, and the moisture was removed with anhydrous calcium chloride (II), followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 10% to 40%) and concentrated to give the title compound (0.023 g, 13.2%) as a pale yellow solid. 1H NMR(400 MHz,CDCl3)δ 7.89(dd,J=8.0,1.4 Hz,1H), 7.77(dd,J=10.0,1.4Hz,1H), 7.61(t,J=7.6Hz,1H), 7.43(t,J=7.8Hz,2H), 7.31(d,J=7.4Hz,1H ), 7.09(d,J=7.8Hz,2H), 7.05-6.79(m,1H), 5.60(s,2H), 3.68(brs,4H), 2.89-2.87(m,4H);LRMS(ES)m / z 533.5(M + +1). EXAMPLES

[0061] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 4) [Step 1] Synthesis of tert-butyl 4-(2-methoxy-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] A solution of 3,4-dimethoxycyclobut-3-ene-1,2-dione (1.520 g, 10.696 mmol) and tert-butyl piperazine-1-carboxylate (1.992 g, 10.696 mmol) in ethanol (30 mL) was stirred at room temperature for 18 hours at the same temperature. The precipitated solid was filtered, washed with hexane and dried to give the desired title compound (1.860 g, 58.7%) as a white solid.

[0062] [Step 2] Synthesis of tert-butyl 4-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] The solution of tert-butyl 4-(2-methoxy-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (1.860 g, 6.277 mmol), aniline (0.573 mL, 6.277 mmol) and triethylamine (1.750 mL, 12.554 mmol) prepared in step 1 in ethanol (20 mL) was stirred at 78°C for 18 hours at the same temperature, and then the temperature was lowered to room temperature to terminate the reaction. The solvent was removed from the reaction mixture under reduced pressure, and water was poured into the resulting concentrate, which was then extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 0% to 50%) to obtain the title compound (0.300 g, 13.4%) as a yellow solid.

[0063] [Step 3] Synthesis of tert-butyl 4-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] tert-Butyl 4-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)piperazine-1-carboxylate (0.176 g, 0.492 mmol) prepared in step 2 was dissolved in N,N-dimethylformamide (10 mL) at 0° C., to which sodium hydride (60.00%, 0.030 g, 0.739 mmol) was added and stirred at the same temperature for 30 minutes. 2-(4-(bromomethyl)phenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.17 g, 0.59 mmol) was added to the reaction mixture, and the mixture was stirred at room temperature for an additional 3 hours. The solvent was removed from the reaction mixture under reduced pressure, and water was poured into the resulting concentrate, which was then extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (0.135 g, 48.5%) as a white solid.

[0064] [Step 4] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid [ka] Tert-butyl 4-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (0.135 g, 0.239 mmol) prepared in step 3 and trifluoroacetic acid (0.183 mL, 2.387 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. The reaction mixture was subjected to reduced pressure to remove the solvent, and the product was used without further purification (0.150 g, 108.4%, yellow oil).

[0065] [Step 5] Synthesis of compound 4 [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid (0.150 g, 0.259 mmol), N,N-diisopropylethylamine (0.045 mL, 0.259 mmol), formaldehyde (0.016 g, 0.518 mmol) and sodium triacetoxyborohydride (0.110 g, 0.518 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. Water was poured into the reaction mixture and extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 10%) and concentrated to give the title compound (0.066 g, 53.2%) as a white solid. 1H NMR(400 MHz,CDCl3)δ 8.05(d,J=7.5 Hz,2H), 7.47(d,J=8.2 Hz,2H), 7.35(t,J=7.9 Hz,2H), 7.20(t,J=7.4Hz,1H), 7.04(s,0.25H), 6.98(d,J=7.7Hz,2H), 6.92(s,0.5H) , 6.79(s,0.25H), 5.50(s,2H), 3.28(brs,4H), 2.26(s,4H), 2.22(s,3H);LRMS(ES)m / z 480.5(M + +1). EXAMPLES

[0066] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(1,1-dioxidothiomorpholino)cyclobut-3-ene-1,2-dione (compound 5) [ka] 3-(1,1-dioxidethiomorpholino)-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.100 g, 0.326 mmol) and sodium hydride (60.00%, 0.014 g, 0.359 mmol) prepared in step 1 of Example 3 were dissolved in N,N-dimethylformamide (3 mL) at room temperature, to which 2-(4-(bromomethyl)phenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.104 g, 0.359 mmol) was added and stirred at the same temperature for 3 hours. Water was poured into the reaction mixture, which was then extracted with dichloromethane and filtered through a plastic filter to remove the solid residue and aqueous layer, and then concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 10% to 40%). Ethyl acetate and diethyl ether were added to the obtained product and stirred. The precipitated solid was filtered, washed with diethyl ether and dried to obtain the title compound (0.016 g, 9.5%) as a white solid. 1H NMR(400 MHz,DMSO-d6)δ 8.00(d,J=8.2 Hz,2H), 7.60-7.41(m,3H), 7.39(t,J=6.4 Hz,1H), 7.23-7.19(m,3H), 5.52(s,2H), 3.53(brs,4H), 3.14(brs,4H);LRMS(ES)m / z 515.4(M + +1). EXAMPLES

[0067] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)-4-(1,1-dioxidothiomorpholino)cyclobut-3-ene-1,2-dione (compound 6) [ka] 3-(1,1-dioxidethiomorpholino)-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.100 g, 0.326 mmol) and sodium hydride (60.00%, 0.014 g, 0.359 mmol) prepared in step 1 of Example 3 were dissolved in N,N-dimethylformamide (3 mL) at room temperature, to which 2-(6-(bromomethyl)-5-fluoropyridin-3-yl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.111 g, 0.359 mmol) was added and stirred at the same temperature for 3 hours. Water was poured into the reaction mixture, and it was extracted with dichloromethane. After filtering with a plastic filter to remove the solid residue and the aqueous layer, it was concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 10% to 40%). Ethyl acetate and diethyl ether were added to the obtained product, and the product was stirred. The precipitated solid was filtered, washed with diethyl ether and dried to obtain the title compound (0.017 g, 9.8%) as a pale yellow solid. 1H NMR(400 MHz,DMSO-d6)δ 8.99(s,1H), 8.41(dd,J=9.9,1.5 Hz,1H), 7.71-7.45(m,1H), 7.41(t,J=7.8 Hz,2H), 7.21-7.17(m,3H), 5.70(brs,2H), 3.62(brs,4H), 3.17(s,4H);LRMS(ES)m / z 534.4(M + +1). EXAMPLES

[0068] Synthesis of 3-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 7) [Step 1] Synthesis of 3-((3-bromo-5-fluorophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione [ka] A solution of 3,4-dimethoxycyclobut-3-ene-1,2-dione (2.000 g, 14.074 mmol) and 3-bromo-5-fluoroaniline (2.674 g, 14.074 mmol) in methanol (50 mL) was stirred at room temperature for 18 hours. The precipitated solid was filtered, washed with hexane and dried to obtain the title compound (3.500 g, 82.9%) as a white solid.

[0069] [Step 2] Synthesis of tert-butyl 4-(2-((3-bromo-5-fluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] 3-((3-bromo-5-fluorophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione (2.000 g, 6.665 mmol) prepared in step 1, tert-butyl piperazine-1-carboxylate (1.862 g, 9.997 mmol) and N,N-diisopropylethylamine (2.322 mL, 13.330 mmol) were dissolved in methanol (30 mL) at room temperature and stirred at the same temperature for 18 hours. The reaction mixture was subjected to reduced pressure to remove the solvent. The concentrate was purified by column chromatography (SiO2, 40 g cartridge; ethyl acetate / hexane = 0% to 30%) and concentrated to obtain the title compound (2.900 g, 95.8%) as a black foamy solid.

[0070] [Step 3] Synthesis of tert-butyl 4-(2-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] tert-Butyl 4-(2-((3-bromo-5-fluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (2.900 g, 6.383 mmol) prepared in step 2 was dissolved in N,N-dimethylformamide (30 mL) at 0° C., to which sodium hydride (60.00%, 0.383 g, 9.575 mmol) was added and stirred at the same temperature for 30 minutes. 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (2.548 g, 8.298 mmol) was added to the reaction mixture, and the mixture was stirred at room temperature for an additional 3 hours. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 40 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (2.000 g, 46.0%) as a yellow foamy solid.

[0071] [Step 4] Synthesis of 3-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid [ka] A solution of tert-butyl 4-(2-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (2.000 g, 2.939 mmol) prepared in step 3 and trifluoroacetic acid (2.251 mL, 29.392 mmol) in dichloromethane (20 mL) at room temperature was stirred at the same temperature for 18 hours. Water was poured into the reaction mixture, and the mixture was extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The product was used without further purification (2.000 g, 98.0%, brown oil).

[0072] [Step 5] Synthesis of compound 7 [ka] 3-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid (2.000 g, 2.880 mmol), N,N-diisopropylethylamine (0.502 mL, 2.880 mmol), formaldehyde (0.173 g, 5.761 mmol) and sodium triacetoxyborohydride (1.221 g, 5.761 mmol) were dissolved in dichloromethane (20 mL) at room temperature and stirred at the same temperature for 18 hours. Water was poured into the reaction mixture and extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 40 g cartridge; methanol / dichloromethane = 0% to 10%) and concentrated to give the title compound (1.500 g, 87.6%) as a yellow solid. 1 H NMR(400 MHz,CDCl3)δ 7.92(dd,J=8.0,1.5 Hz,1H), 7.85(dd,J=10.2,1.5Hz,1H), 7.59(t,J=7.7Hz,1H), 7.06-7.02(m,1H), 7.04(s,0.25H), 6.93(s,0.5H), 6.8 5(s,1H), 6.80(s,0.25H), 6.71-6.67(m,1H), 5.49(s,2H), 3.45(brs,4H), 2.39(brs,4H), 2.30(s,3H);LRMS(ES)m / z 595.4(M + +1). EXAMPLES

[0073] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3-fluoro-5-(pyridin-3-yl)phenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 8) [ka] 3-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (0.200 g, 0.336 mmol) prepared in Example 7, pyridin-3-ylboronic acid (0.054 g, 0.437 mmol) [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium(II) dichloride (Pd(dtbpf)Cl2, 0.022 g, 0.034 mmol) and cesium carbonate (0.219 g, 0.673 mmol) were mixed in 1,4-dioxane (9 mL) / water (3 mL), and the mixture was irradiated with microwaves and heated at 100°C for 20 minutes, after which the temperature was lowered to room temperature to terminate the reaction. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 20%) to obtain the title compound (0.080 g, 40.1%) as a brown oil. 1 HNMR(400MHz,CDCl3)δ8.78(d,J=1.9Hz,1H), 8.67(dd,J=4.7,1.1Hz,1H), 7.91(dd,J= 8.0,1.4Hz,1H), 7.85-7.80(m,2H), 7.65(t,J=7.7Hz,1H), 7.43(dd,J=7.9,4.9Hz,1H) , 7.11-7.08(m,1H), 7.05(s,0.25H), 6.96(s,1H), 6.92(s,0.5H), 6.79(s,0.25H), 6.7 8-6.74(m,1H), 5.58(s,2H), 3.49(brs,4H), 2.28(brs,4H), 2.19(s,3H);LRMS(ES)m / z 593.5(M + +1). EXAMPLES

[0074] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(6-(oxetan-3-yl)-2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 9) [ka] 3-((3-bromo-5-fluorophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (0.200 g, 0.336 mmol) prepared in Example 7, pyridin-4-ylboronic acid (0.054 g, 0.437 mmol) [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium(II) dichloride (Pd(dtbpf)Cl2, 0.022 g, 0.034 mmol) and cesium carbonate (0.219 g, 0.673 mmol) were mixed in 1,4-dioxane (9 mL) / water (3 mL), and the mixture was irradiated with microwaves and heated at 100°C for 20 minutes, after which the temperature was lowered to room temperature to terminate the reaction. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 20%) to obtain the title compound (0.070 g, 35.1%) as a brown oil. 1HNMR(400MHz, CDCl3) δ8.73(d,J=5.6Hz,1H), 7.92-7.90(m,1H), 7.86-7.8 3(m,1H), 7.66(t,J=7.7Hz,1H), 7.43(d,J=5.9Hz,2H), 7.15-7.13(m,1H), 7 .05(s,0.25H), 7.00(s,1H), 6.92(s,0.5H), 6.81(s,0.25H), 6.80-6.78(m, 1H), 5.58(s,2H), 3.30(brs,4H), 2.27(brs,4H), 2.19(s,3H);LRMS(ES)m / z 593.4(M + +1). EXAMPLES

[0075] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(6-(oxetan-3-yl)-2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 10) [Step 1] Synthesis of tert-butyl 6-(2-methoxy-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate [ka] A solution of 3,4-dimethoxycyclobut-3-ene-1,2-dione (1.710 g, 12.033 mmol) and tert-butyl 2,6-diazaspiro[3.3]heptane-2-carboxylate (2.386 g, 12.033 mmol) in ethanol (30 mL) was stirred at room temperature for 18 hours. The precipitated solid was filtered, washed with hexane and dried to obtain the title compound (0.700 g, 18.9%) as a white solid.

[0076] [Step 2] Synthesis of tert-butyl 6-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate [ka] The solution of tert-butyl 6-(2-methoxy-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate (0.700 g, 2.270 mmol), aniline (0.207 mL, 2.270 mmol) and triethylamine (0.633 mL, 4.541 mmol) prepared in step 1 in ethanol (20 mL) was stirred at the same temperature for 18 hours, and then the temperature was lowered to room temperature to terminate the reaction. The reaction mixture was removed from the solvent under reduced pressure, and water was poured into the resulting concentrate, which was then extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (0.600 g, 71.5%) as a white solid.

[0077] [Step 3] Synthesis of tert-butyl 6-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate [ka] Tert-butyl 6-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate (0.687 g, 1.860 mmol) prepared in step 2 was dissolved in N,N-dimethylformamide (5 mL) at 0° C., to which sodium hydride (60.00%, 0.112 g, 2.790 mmol) was added and stirred at the same temperature for 30 minutes. 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.685 g, 2.232 mmol) was added to the reaction mixture, and the mixture was stirred at room temperature for an additional 3 hours. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (0.700 g, 63.2%) as a white solid.

[0078] [Step 4] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione [ka] Tert-butyl 6-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate (0.700 g, 1.175 mmol) prepared in step 3 and trifluoroacetic acid (0.900 mL, 11.753 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate solution was poured into the reaction mixture and extracted with dichloromethane. The organic layer was washed with saturated aqueous sodium chloride solution, removed with anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The product was used without further purification (0.400 g, 68.7%, white solid).

[0079] [Step 5] Synthesis of compound 10 [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-(2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione (0.100 g, 0.202 mmol), 3-oxetanone (0.029 g, 0.404 mmol) and sodium triacetoxyborohydride (0.086 g, 0.404 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. Water was poured into the reaction mixture, and it was extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, and then it was filtered and concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 20%) and concentrated to give the title compound (0.080 g, 71.9%) as a colorless oil. 1 H NMR(400 MHz,CDCl3)δ 7.84(dd,J=8.0,1.4 Hz,1H), 7.69(dd,J=9.8,1.4Hz,1H), 7.61(t,J=7.6Hz,1H), 7.39-7.33(m,3H), 7.06-7.04(m,2H), 7.06(s,0.25H), 6.91(s,0.5H) , 6.78(s,0.25H), 5.44(s,2H), 4.62-4.58(m,2H), 4.34-4.31(m,2H), 3.80(brs,4H), 3.60-3.58(m,1H), 3.23(s,4H);LRMS(ES)m / z 552.5(M + +1). EXAMPLES

[0080] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(6-methyl-2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 11) [Step 1] Synthesis of tert-butyl 6-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate [ka] tert-Butyl 6-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate (0.177 g, 0.479 mmol) prepared in step 2 of Example 10 was dissolved in N,N-dimethylformamide (10 mL) at 0° C., to which sodium hydride (60.00%, 0.029 g, 0.719 mmol) was added and stirred at the same temperature for 30 minutes. 2-(4-(bromomethyl)phenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.166 g, 0.575 mmol) was added to the reaction mixture and stirred at room temperature for an additional 3 hours. Water was poured into the reaction mixture, and it was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and water was removed with anhydrous sodium sulfate, and then it was filtered and concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (0.150 g, 54.2%) as a white solid.

[0081] [Step 2] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid [ka] Tert-butyl 6-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,6-diazaspiro[3.3]heptane-2-carboxylate (0.180g, 0.312mmol) prepared in step 1 and trifluoroacetic acid (0.239mL, 3.116mmol) were dissolved in dichloromethane (10mL) at room temperature and stirred at the same temperature for 18 hours. The reaction mixture was removed under reduced pressure to remove the solvent, and the product was used without further purification (0.180g, 97.6%, yellow oil).

[0082] [Step 3] Synthesis of compound 11 [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)benzyl)(phenyl)amino)-4-(2,6-diazaspiro[3.3]heptan-2-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid (0.180 g, 0.304 mmol), N,N-diisopropylethylamine (0.053 mL, 0.304 mmol), formaldehyde (0.018 g, 0.609 mmol) and sodium triacetoxyborohydride (0.129 g, 0.609 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. Water was poured into the reaction mixture and extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 20%) and concentrated to give the title compound (0.056 g, 37.4%) as a white solid. 1 H NMR(400 MHz,CDCl3)δ 8.02(d,J=8.2 Hz,2H), 7.40-7.35(m,5H), 7.04(s,0.25H), 7.03-7.01(m,2H), 6.91(s,0.5H), 6 .78(s,0.25H), 5.33(s,2H), 3.68(s,4H), 2.45(s,3H), 1.45(s,4H);LRMS(ES)m / z 492.4(M + +1). EXAMPLES

[0083] Synthesis of 3-((3-bromophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 12) [Step 1] Synthesis of 3-((3-bromophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione [ka] A solution of 3,4-dimethoxycyclobut-3-ene-1,2-dione (2.000 g, 14.074 mmol) and 3-bromoaniline (2.421 g, 14.074 mmol) in methanol (50 mL) was stirred at room temperature for 18 hours. The precipitated solid was filtered, washed with hexane and dried to obtain the title compound (3.500 g, 88.2%) as a white solid.

[0084] [Step 2] Synthesis of tert-butyl 4-(2-((3-bromophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] 3-((3-bromophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione (1.250 g, 4.431 mmol) prepared in step 1, tert-butyl piperazine-1-carboxylate (1.238 g, 6.647 mmol) and N,N-diisopropylethylamine (1.544 mL, 8.862 mmol) were dissolved in ethanol (20 mL) at 78° C. and stirred at the same temperature for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. The precipitated solid was filtered, washed with hexane and dried to obtain the title compound (1.200 g, 62.1%) as a white solid.

[0085] [Step 3] Synthesis of tert-butyl 4-(2-((3-bromophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] tert-Butyl 4-(2-((3-bromophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (1.200 g, 2.750 mmol) prepared in step 2 was dissolved in N,N-dimethylformamide (30 mL) at 0° C., to which sodium hydride (60.00%, 0.143 g, 3.575 mmol) was added and stirred at the same temperature for 30 minutes. 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (1.013 g, 3.300 mmol) was added to the reaction mixture, and the mixture was stirred at room temperature for an additional 3 hours. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 40 g cartridge; ethyl acetate / hexane = 0% to 50%) and concentrated to give the title compound (1.400 g, 76.8%) as a colorless oil.

[0086] [Step 4] Synthesis of 3-((3-bromophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid [ka] The solution of tert-butyl 4-(2-((3-bromophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (1.400 g, 2.113 mmol) prepared in step 3 and trifluoroacetic acid (1.618 mL, 21.133 mmol) in dichloromethane (20 mL) at room temperature was stirred at the same temperature for 18 hours. The reaction mixture was removed under reduced pressure to remove the solvent, and the product was used without further purification (1.400 g, 97.9%, brown oil).

[0087] [Step 5] Synthesis of compound 12 [ka] 3-((3-bromophenyl)(4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione 2,2,2-trifluoroacetic acid (1.400 g, 2.070 mmol), formaldehyde (0.124 g, 4.140 mmol), N,N-diisopropylethylamine (0.361 mL, 2.070 mmol) and sodium triacetoxyborohydride (0.877 g, 4.140 mmol) were dissolved in dichloromethane (10 mL) at room temperature and stirred at the same temperature for 18 hours. Water was poured into the reaction mixture and extracted with dichloromethane. The organic layer was washed with a saturated aqueous sodium chloride solution, and the moisture was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 10%) and concentrated to give the title compound (0.900 g, 75.4%) as a white solid. 1 H NMR(400 MHz,CDCl3)δ 7.89(dd,J=8.0,1.5 Hz,1H), 7.80(dd,J=10.1,1.5Hz,1H), 7.60(t,J=7.6 Hz,1H), 7.30-7.28(m,1H), 7.23(t,J=8.0 Hz,1H), 7.08(t,J=1.9Hz,1H), 7.05(s,0.25H), 6.98(dd,J=8.0,1.5Hz,1H), 6.92(s,0.5H), 6 .79(s,0.25H), 5.53(s,2H), 3.36(brs,4H), 2.45(brs,4H), 2.25(s,3H);LRMS(ES)m / z577.4(M + +1). EXAMPLES

[0088] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-((1S,4S)-5-(oxetan-3-yl)-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 13) [Step 1] Synthesis of tert-butyl (1S,4S)-5-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate [ka] A solution of 3-methoxy-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.500 g, 2.461 mmol), tert-butyl (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.537 g, 2.707 mmol) and N,N-diisopropylethylamine (0.85 mL, 4.921 mmol) dissolved in methanol (10 mL) at room temperature was stirred at the same temperature for 18 hours. After removing the solvent from the reaction mixture under reduced pressure, the concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 20% to 40%) to obtain the title compound (0.871 g, 95.8%) as a pale yellow solid.

[0089] [Step 2] Synthesis of tert-butyl (1S,4S)-5-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate [ka] tert-Butyl (1S,4S)-5-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.300 g, 0.812 mmol), 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.274 g, 0.893 mmol), potassium carbonate (0.224 g, 1.624 mmol) and potassium iodide (0.013 g, 0.081 mmol) were dissolved in N,N-dimethylformamide (4 mL) at room temperature and stirred at 60° C. for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. The solvent was removed from the reaction mixture under reduced pressure, and a saturated aqueous solution of sodium bicarbonate was poured into the resulting concentrate and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 30% to 60%) to obtain the title compound (0.315 g, 65.1%) as a yellow solid.

[0090] [Step 3] Synthesis of 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)cyclobut-3-ene-1,2-dione [ka] Tert-butyl (1S,4S)-5-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.315 g, 0.529 mmol) prepared in step 2 and trifluoroacetic acid (0.284 mL, 3.702 mmol) were dissolved in dichloromethane (4 mL) at room temperature and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The product was used without further purification (0.221 g, 84.3%, pale yellow solid).

[0091] [Step 4] Synthesis of compound 13 [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.100 g, 0.202 mmol) and formaldehyde (0.018 mL, 0.303 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.086 g, 0.404 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate solution was poured into the reaction mixture and extracted with dichloromethane. After filtering through a plastic filter to remove the solid residue and the aqueous layer, the mixture was concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 2.5%) and concentrated to give the title compound (0.075 g, 67.4%) as a yellow solid. 1 H NMR(400 MHz,CDCl3)δ 7.87(dd,J=8.0,1.4 Hz,1H), 7.72-7.66(m,2H), 7.35(t,J=7.6Hz,2H), 7.29-7.25(m,1H), 7.07(d,J=7.6Hz,2H) ), 7.05-6.79(m,1H), 5.56(d,J=15.4Hz,1H), 5.47(d,J=15.4Hz,1H), 4.63-4.57(m,2H), 4. 40(t,J=5.9Hz,2H), 3.74-3.71(m,1H), 3.13(brs,1H), 2.78(brs,1H), 2.67(brs,1H), 1.9 5(brs,1H), 1.76(d,J=9.8Hz,1H), 1.54(d,J=10.1Hz,1H), 1.30-1.28(m,1H);LRMS(ES)m / z 552.8(M + +1). EXAMPLES

[0092] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)-4-((1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 14) [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.100 g, 0.202 mmol) and formaldehyde (38.00% solution, 0.022 mL, 0.303 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.086 g, 0.404 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate solution was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) and concentrated to give the title compound (0.049 g, 47.7%) as a yellow solid. 1 H NMR(400 MHz,CDCl3)δ 7.88(dd,J=8.0,1.5 Hz,1H), 7.74-7.67(m,2H), 7.35(t,J=7.6 Hz,2H), 7.28-7.25(m,1H), 7.07-6.79(m,3H), 5.58-5.47(m,2H), 3.13(brs,1H) , 2.71(brs,1H), 2.63(brs,1H), 2.28(s,3H), 1.99-1.83(m,3H), 1.52(d,J=10.1 Hz,1H), 1.31-1.29(m,1H);LRMS(ES)m / z 510.8(M+ +1). EXAMPLES

[0093] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)-4-((1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 15) [Step 1] Synthesis of tert-butyl (1S,4S)-5-(2-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate [ka] tert-Butyl (1S,4S)-5-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.500 g, 1.353 mmol) prepared in step 1 of Example 13, 2-(6-(bromomethyl)pyridin-3-yl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.432 g, 1.489 mmol), potassium carbonate (0.281 g, 2.030 mmol) and potassium iodide (0.022 g, 0.135 mmol) were dissolved in N,N-dimethylformamide (4 mL) at room temperature and stirred at 60 ° C. for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. The reaction mixture was removed from the solvent under reduced pressure, and saturated aqueous sodium bicarbonate was poured into the resulting concentrate, which was then extracted with dichloromethane. The concentrate was filtered through a plastic filter to remove the solid residue and aqueous layer, and then concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 30% to 65%) to obtain the title compound (0.440 g, 56.2%) as a light brown solid.

[0094] [Step 2] Synthesis of 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione [ka] Tert-butyl (1S,4S)-5-(2-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.440 g, 0.760 mmol) prepared in step 1 and trifluoroacetic acid (0.291 mL, 3.802 mmol) were dissolved in dichloromethane (4 mL) at room temperature and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. After filtering through a plastic filter to remove the solid residue and the aqueous layer, the mixture was concentrated under reduced pressure. The product was used without further purification (0.277 g, 76.1%, brown solid).

[0095] [Step 3] Synthesis of compound 15 [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.090 g, 0.188 mmol) and formaldehyde (38.00% solution in water, 0.021 mL, 0.282 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.080 g, 0.376 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate solution was poured into the reaction mixture and extracted with dichloromethane. After filtering through a plastic filter to remove the solid residue and the aqueous layer, it was concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) and concentrated to give the title compound (0.054 g, 58.3%) as an orange solid. 1HNMR(400MHz, CDCl3) δ9.25(d,J=2.0Hz,1H), 8.37(dd,J=8.2,2.2Hz,1H), 7.64(d,J=8.2 Hz,1H), 7.36(t,J=7.8Hz,2H), 7.24(t,J=7.4Hz,1H), 7.19(d,J=7.6Hz,2H), 7.08-6.82(m ,1H), 5.63-5.50(m,2H), 3.18(brs,1H), 2.76(brs,1H), 2.63(brs,1H), 2.31(s,3H), 2.1 6-2.14(m,2H), 1.87(d,J=9.9Hz,1H), 1.57-1.53(m,1H), 1.32-1.28(m,1H);LRMS(ES)m / z 493.8(M + +1). EXAMPLES

[0096] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)-4-((1S,4S)-5-isopropyl-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 16) [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.090 g, 0.188 mmol) prepared in step 2 of Example 15 and acetone (0.021 mL, 0.282 mmol) were dissolved in dichloromethane (4 mL) at room temperature, to which sodium triacetoxyborohydride (0.080 g, 0.376 mmol) was added and stirred at the same temperature for 18 hours. A saturated aqueous solution of sodium bicarbonate was poured into the reaction mixture, which was then extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) and concentrated to give the title compound (0.056 g, 57.2%) as an orange solid. 1 HNMR(400MHz, CDCl3) δ9.25(d,J=2.0Hz,1H), 8.38(dd,J=8.2,2.1Hz,1H), 7.65 (d,J=8.1Hz,1H), 7.37(t,J=7.8Hz,2H), 7.24(t,J=7.4Hz,1H), 7.19(d,J=7.7H z,2H), 7.08-6.82(m,1H), 5.62-5.52(m,2H), 3.49(brs,1H), 3.03(s,1H), 2.46 (s,2H), 1.88-1.57(m,4H), 1.04-1.03(m,3H), 0.99-0.95(m,4H);LRMS(ES)m / z 521.8(M + +1). EXAMPLES

[0097] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)-4-((1S,4S)-5-(oxetan-3-yl)-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 17) [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.100 g, 0.209 mmol) and 3-oxetanone (0.018 mL, 0.314 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.089 g, 0.418 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 2.5%) and concentrated to give the title compound (0.036 g, 32.2%) as an orange solid. 1 HNMR(400MHz,CDCl3)δ9.27(s,1H), 8.39(dd,J=8.1,1.8Hz,1H), 7.64(d,J=8 .2Hz,1H), 7.38(t,J=7.7Hz,2H), 7.26-7.24(m,1H), 7.21(d,J=8.0Hz,2H), 7 .08-6.82(m,1H), 5.62-5.51(m,2H), 4.65-4.59(m,2H), 4.44(brs,2H), 3.77 (brs,2H), 3.20(brs,2H), 2.80-2.72(m,2H), 1.82-1.52(m,4H);LRMS(ES)m / z 535.8(M + +1). EXAMPLES

[0098] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(3-(pyridin-3-yl)phenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 18) [ka] 3-((3-bromophenyl)((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (0.250 g, 0.447 mmol), pyridin-3-ylboronic acid (0.071 g, 0.581 mmol), [1,1'-biphenyl] [(di-tert-butylphosphino)ferrocene]palladium(II) dichloride (Pd(dtbpf)Cl2, 0.029 g, 0.045 mmol) and cesium carbonate (0.364 g, 1.117 mmol) were mixed in 1,4-dioxane (9 mL) / water (3 mL), and the mixture was heated at 100°C for 20 hours under microwave irradiation, and then the temperature was lowered to room temperature to terminate the reaction. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous solution of sodium chloride, and water was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 10%) to obtain the title compound (0.100 g, 40.1%) as a brown oil. 1HNMR(400MHz,CDCl3)δ8.78(d,J=1.6Hz,1H), 8.64(d,J=3.8Hz,1H), 7.88-7.7 6(m,3H), 7.66(t,J=7.6Hz,1H), 7.47(t,J=7.8Hz,1H), 7.42-7.39(m,2H), 7.18 (s,1H), 7.07(dd,J=7.9,1.3Hz,1H), 7.04(s,0.25H), 6.91(s,0.5H), 6.78(s, 0.25H), 5.61(s,2H), 3.32(brs,4H), 2.23(brs,4H), 2.16(s,3H);LRMS(ES)m / z 558.4(M + +1). EXAMPLES

[0099] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)(3-(pyridin-4-yl)phenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 19) [ka] 3-((3-bromophenyl)((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridin-2-yl)methyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (0.200 g, 0.358 mmol), pyridin-4-ylboronic acid (0.057 g, 0.465 mmol), [1,1'-bis(di-tert-butylphosphino)ferrocene]palladium(II) dichloride (Pd(dtbpf)Cl2, 0.023 g, 0.036 mmol) and cesium carbonate (0.291 g, 0.894 mmol) were mixed in 1,4-dioxane (9 mL) / water (3 mL), and the mixture was irradiated with microwaves and heated at 100 ° C for 15 minutes, after which the temperature was lowered to room temperature to complete the reaction. Water was poured into the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, and then water was removed with anhydrous sodium sulfate, followed by filtration and concentration under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; methanol / dichloromethane = 0% to 10%) to obtain the title compound (0.060 g, 30.1%) as a black oil. 1 HNMR(400MHz,CDCl3)δ8.71(d,J=4.4Hz,2H), 7.89(d,J=8.1Hz,1H), 7.80(dd,J=10.1,1.1Hz,1H), 7.67(t,J=7.6Hz,1H), 7.50-7.43(m,4H), 7.23 (s,1H), 7.11-7.09(m,1H), 7.04(s,0.25), 6.91(s,0.5H), 6.78(s,0.25H) ), 5.62(s,2H), 3.31(brs,4H), 2.22(brs,4H), 3.16(s,3H);LRMS(ES)m / z 558.4(M + +1). EXAMPLES

[0100] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)-4-((1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 20) [Step 1] Synthesis of tert-butyl (1S,4S)-5-(2-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate [ka] tert-Butyl (1S,4S)-5-(3,4-dioxo-2-(phenylamino)cyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.500 g, 1.353 mmol) prepared in step 1 of Example 13, 2-(bromomethyl)-3-fluoro-5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)pyridine (0.459 g, 1.489 mmol), potassium carbonate (0.281 g, 2.030 mmol) and potassium iodide (0.022 g, 0.135 mmol) were dissolved in N,N-dimethylformamide (4 mL) at room temperature and stirred at 60 ° C. for 18 hours, then the temperature was lowered to room temperature to terminate the reaction. The reaction mixture was removed from the solvent under reduced pressure, and saturated aqueous sodium bicarbonate was poured into the resulting concentrate, which was then extracted with dichloromethane. The concentrate was filtered through a plastic filter to remove the solid residue and aqueous layer, and then concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 30% to 70%) to obtain the title compound (0.285 g, 35.3%) as a brown solid.

[0101] [Step 2] Synthesis of 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione [ka] Tert-butyl (1S,4S)-5-(2-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)-2,5-diazabicyclo[2.2.1]heptane-2-carboxylate (0.285 g, 0.478 mmol) prepared in step 1 and trifluoroacetic acid (0.256 mL, 3.344 mmol) were dissolved in dichloromethane (4 mL) at room temperature and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; ethyl acetate / hexane = 0% to 30%) and concentrated to give the title compound (0.206 g, 86.9%) as a light brown solid.

[0102] [Step 3] Synthesis of compound 20 [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.100 g, 0.201 mmol) and formaldehyde (0.009 g, 0.302 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.085 g, 0.403 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) and concentrated to give the title compound (0.067 g, 65.2%) as a yellow solid. 1 HNMR(400MHz,CDCl3)δ9.05(s,1H), 8.06(d,J=9.3Hz,1H), 7.34(t,J=7.1Hz,2H), 7.22(t,J=7.4Hz,1H), 7.14(d,J=8.0Hz,2H), 7.08-6.82(m,1H) , 5.71-5.66(m,2H), 3.18(brs,1H), 2.77(brs,3H), 2.61-2.59(m,1H), 2.30(brs,3H), 1.86(d,J=9.8Hz,1H), 1.57(d,J=10.1Hz,1H);LRMS(ES)m / z 511.8(M + +1). EXAMPLES

[0103] Synthesis of 3-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)-4-((1S,4S)-5-(oxetan-3-yl)-2,5-diazabicyclo[2.2.1]heptan-2-yl)cyclobut-3-ene-1,2-dione (compound 21) [ka] 3-((1S,4S)-2,5-diazabicyclo[2.2.1]heptan-2-yl)-4-(((5-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-3-fluoropyridin-2-yl)methyl)(phenyl)amino)cyclobut-3-ene-1,2-dione (0.100 g, 0.201 mmol) and 3-oxetanone (0.019 mL, 0.302 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.085 g, 0.403 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate was poured into the reaction mixture and extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 2.5%) and concentrated to give the title compound (0.019 g, 17.1%) as a yellow solid. 1 HNMR(400MHz,CDCl3)δ9.09(s,1H), 8.10(dd,J=29.3,20.0Hz,1H), 7.37(t,J=7 .7Hz,2H), 7.26-7.24(m,1H), 7.18(d,J=7.6Hz,2H), 7.08-6.82(m,1H), 5.68(s, 2H), 4.68-4.63(m,2H), 4.50-4.45(m,2H), 3.81-3.80(m,1H), 3.22(brs,1H), 2. 82(brs,1H), 2.75(brs,1H), 1.83-1.59(m,4H), 1.31-1.30(m,1H);LRMS(ES)m / z 553.7(M + +1). EXAMPLES

[0104] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-4-(4-methylpiperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 22) [Step 1] Synthesis of 3-((3,4-difluorophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione [ka] A solution of 3,4-difluoroaniline (1.000 g, 7.745 mmol) and 3,4-dimethoxycyclobut-3-ene-1,2-dione (1.101 g, 7.745 mmol) in methanol (30 mL) was stirred at room temperature for 18 hours. The precipitated solid was filtered, washed with methanol and dried to obtain the title compound (1.610 g, 86.9%) as a pale yellow solid.

[0105] [Step 2] Synthesis of tert-butyl 4-(2-((3,4-difluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] 3-((3,4-difluorophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione (1.500 g, 6.271 mmol) prepared in step 2, tert-butyl piperazine-1-carboxylate (1.168 g, 6.271 mmol) and N,N-diisopropylethylamine (1.092 mL, 6.271 mmol) were dissolved in methanol (30 mL) at room temperature and stirred at the same temperature for 18 hours. Methanol was added to the reaction mixture, and the precipitated solid was filtered, washed with methanol and dried to obtain the title compound (1.770 g, 71.7%) as a pale green solid.

[0106] [Step 3] Synthesis of tert-butyl 4-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate [ka] 2-(4-(bromomethyl)-3-fluorophenyl)-5-(difluoromethyl)-1,3,4-oxadiazole (0.429 g, 1.398 mmol) was added to a solution of tert-butyl 4-(2-((3,4-difluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (0.500 g, 1.271 mmol) and sodium hydride (60.00%, 0.056 g, 1.398 mmol) prepared in step 2 in N,N-dimethylformamide (20 mL) at 0° C., and the mixture was stirred at room temperature for 18 hours. After removing the solvent from the reaction mixture under reduced pressure, the concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 5% to 40%) to obtain the title compound (0.516 g, 65.5%) as a pale yellow solid.

[0107] [Step 4] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione [ka] Tert-butyl 4-(2-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-3,4-dioxocyclobut-1-en-1-yl)piperazine-1-carboxylate (0.516 g, 0.833 mmol) prepared in step 3 and trifluoroacetic acid (0.510 mL, 6.663 mmol) were dissolved in dichloromethane (5 mL) at room temperature and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate and dichloromethane were added to the reaction mixture, and the precipitated solid was filtered. It was washed with dichloromethane and dried to obtain the title compound (0.361 g, 83.4%) as a yellow solid.

[0108] [Step 5] Synthesis of compound 22 [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione (0.100 g, 0.193 mmol) and formaldehyde (38.00% solution, 0.021 mL, 0.289 mmol) were dissolved in dichloromethane (4 mL) at room temperature, and sodium triacetoxyborohydride (0.082 g, 0.385 mmol) was added to the solution and stirred at the same temperature for 18 hours. Saturated aqueous sodium bicarbonate solution was poured into the reaction mixture, and it was extracted with dichloromethane. It was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 5%) and concentrated to give the title compound (0.044 g, 42.8%) as a white solid. 1 HNMR(400MHz, CDCl3) δ7.90(d,J=8.0Hz,1H), 7.81(d,J=10.2Hz,1H), 7.63(t,J=7.7Hz,1H), 7.17(q,J=9.0Hz ,1H), 7.06-6.85(m,2H), 6.77-6.75(m,1H), 5.52(s,1H), 3.37(s,4H), 2.35(s,4H), 2.28(s,3H);LRMS(ES)m / z 534.7(M + +1) EXAMPLES

[0109] Synthesis of 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-4-(4-(oxetan-3-yl)piperazin-1-yl)cyclobut-3-ene-1,2-dione (compound 23) [ka] 3-((4-(5-(difluoromethyl)-1,3,4-oxadiazol-2-yl)-2-fluorobenzyl)(3,4-difluorophenyl)amino)-4-(piperazin-1-yl)cyclobut-3-ene-1,2-dione (0.065 g, 0.125 mmol) prepared in step 4 of Example 23 and oxetan-3-one (0.012 mL, 0.188 mmol) were dissolved in dichloromethane (4 mL) at room temperature, to which sodium triacetoxyborohydride (0.053 g, 0.250 mmol) was added and stirred at the same temperature for 18 hours. A saturated aqueous solution of sodium bicarbonate was poured into the reaction mixture, which was then extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified by column chromatography (SiO2, 4 g cartridge; methanol / dichloromethane = 0% to 2.5%) and concentrated to give the title compound (0.016 g, 22.2%) as a white solid. 1 H NMR(400 MHz,CDCl3)δ 7.90(dd,J=8.0,1.2 Hz,1H), 7.80(dd,J=10.1,1.2Hz,1H), 7.62(t,J=7.7Hz,1H), 7.17(q,J=9.0Hz,1H), 7.06-6.85(m,2H), 6.77-6.75 (m,1H), 5.52(s,2H), 4.64(t,J=6.5Hz,2H), 4.52(t,J=6.1Hz,2H), 3.50-3.39(m,5H), 2.25(brs,4H);LRMS(ES)m / z 576.3(M + +1). EXAMPLES

[0110] Synthesis of 3-morpholino-4-[N-[[4-[5-(trifluoromethyl)-1,3,4-oxadiazol-2-yl]phenyl]methyl]anilino]cyclobut-3-ene-1,2-dione (compound 24) [ka] 3-morpholino-4-(phenylamino)cyclobut-3-ene-1,2-dione (0.500 g, 1.936 mmol) and sodium hydride (60.00%, 0.085 g, 2.125 mmol) prepared in step 1 of Example 2 were dissolved in N,N-dimethylformamide (10 mL) at 0°C, to which 2-[4-(bromomethyl)phenyl]-5-(trifluoromethyl)-1,3,4-oxadiazole (0.624 g, 2.032 mmol) was added and stirred at room temperature for 18 hours. The solvent was removed from the reaction mixture under reduced pressure, and a saturated aqueous solution of sodium bicarbonate was poured into the resulting concentrate, which was then extracted with dichloromethane. The mixture was filtered through a plastic filter to remove the solid residue and the aqueous layer, and then concentrated under reduced pressure. The concentrate was purified and concentrated by column chromatography (SiO2, 12 g cartridge; ethyl acetate / hexane = 10% to 60%). Dichloromethane and diethyl ether were added to the obtained product, and the precipitated solid was filtered, washed with diethyl ether, and dried to obtain the title compound (0.196 g, 20.90%, white solid). 1 H NMR(400 MHz,DMSO-d6)δ 8.06(d,J=8.4 Hz,2H), 7.60(d,J=8.4 Hz,2H), 7.41(t,J=7.8 Hz,2H), 7.26-7.21(m,3H), 5.57(s,2H), 3.51(t,J=4.8 Hz,4H), 3.27(brs,4H);LRMS(ES)m / z 485.7(M + +1).

[0111] Activity measurement and analysis protocol of the compound of the present invention <Experimental Example 1> Confirmation of HDAC enzyme activity inhibition (in vitro) Selective HDAC6 inhibitors are important for the selectivity of HDAC1 inhibition, which causes side effects. To confirm this, we examined HDAC1 / 6 enzyme selectivity and cell selectivity (HDAC1: histone acetylation / HDAC6: tubulin acetylation).

[0112] 1. Experimental Method The HDAC enzyme inhibitory activity of the test substances was measured using HDAC1 Fluorimetric Drug Discovery Assay Kit (Enzo life sciences: BML-AK511) and HDAC6 human recombinant (Calbiochem: 382180). For HDAC1 assay, the substances were treated at 100, 1000, and 10000nM concentrations, and for HDAC6 assay, the substances were treated at 0.1, 1, 10, 100, and 1000nM concentrations. After sample treatment, the reaction was carried out at 37°C for 60 minutes, developer was treated, and the reaction was continued at 37°C for 30 minutes, after which the fluorescence intensity (Ex390, Em460) was measured using FlexStatin3 (Molecular device).

[0113] 2. Experimental Results The results of the search for inhibition of HDAC enzyme activity obtained according to the above experimental method are shown in Table 2. [Table 2]

Claims

1. A 1,3,4-oxadiazole derivative compound represented by the following formula I, a stereoisomer thereof, or a pharma- ceutically acceptable salt thereof: [Chemical formula I] In the above formula I, R １ and R ２ Each independently represents -(C １ -C ４ alkyl), or R １ and R ２ are linked together to form a heterocycloalkyl together with the N atom, wherein one or more H in the heterocycloalkyl ring are each independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -halo, or heterocycloalkyl; X is -H or -F; Y １ ~Y ５ each independently represents N or CR ３ where Y １ ~Y ５ cannot be more than two Ns at the same time; R ３ is -H, -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -halo, aryl, or heteroaryl, where one or more -H in the aryl or heteroaryl ring are each independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -OH, -O(C １ -C ４ alkyl), or -halo; Z １ ~Z ４ each independently represents N or CR ４ where Z １ ~Z ４ cannot simultaneously be more than two Ns; and R ４ is -H, -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -halo, aryl, or heteroaryl, where one or more -H in the aryl or heteroaryl ring is each independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -OH, -O(C １ -C ４ It may be substituted with -alkyl), or -halo.

2. In the above formula I, R １ and R ２ are linked together to form a heterocycloalkyl together with the N atom, wherein one or more H in the heterocycloalkyl ring are each independently -(C １ -C ４ alkyl) or heterocycloalkyl; X is -H or -F; Y １ ~Y ５ are each independently CR ３ and R ３ is —H, -halo, or heteroaryl, where one or more —H in the heteroaryl ring are each independently —(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -OH, -O(C １ -C ４ alkyl), or -halo; Z １ ~Z ４ each independently represents N or CR ４ where Z １ ~Z ４ cannot simultaneously be more than two Ns; and R ４ is -H or -halo; The 1,3,4-oxadiazole derivative compound according to claim 1, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof.

3. In the above formula I, R １ and R ２ are linked together to form a 4- to 12-membered heterocycloalkyl together with the N atom, where one or more H in the heterocycloalkyl ring are each independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), -halo, or 3-6 membered heterocycloalkyl; The 1,3,4-oxadiazole derivative compound according to claim 1, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof.

4. In the above formula I, R １ and R ２ are linked together and together with the N atom 【Chemistry 2】 wherein said 【Chemistry 3】 One or more H in the ring is independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), or -halo; W is NR ５ , O, S, or S(=O) ２ and R ５ is -(C １ -C ４ alkyl) or 3-6 membered heterocycloalkyl; and n1, n2, m1 and m2 are each independently 0, 1 or 2; The 1,3,4-oxadiazole derivative compound, its stereoisomer or a pharma- ceutically acceptable salt thereof according to claim 3.

5. In the above formula I, R １ and R ２ are linked together and together with the N atom 【Chemistry 4】 wherein said 【Chemistry 5】 One or more H in the ring is independently -(C １ -C ４ alkyl), -(C １ -C ４ aminoalkyl), -(C １ -C ４ Hydroxyalkyl), -(C １ -C ４ haloalkyl), or -halo; and R ５ is -(C １ -C ４ alkyl) or 【Chemistry 6】 is; The 1,3,4-oxadiazole derivative compound, its stereoisomer or a pharma- ceutically acceptable salt thereof according to claim 4.

6. The 1,3,4-oxadiazole derivative compound according to claim 1, which is any one of the compounds listed in the following table, its stereoisomer or a pharma- ceutically acceptable salt thereof: 【Table 1】

7. A pharmaceutical composition for preventing or treating a histone deacetylase 6-mediated disease, comprising as an active ingredient a compound represented by formula I according to any one of claims 1 to 6, a stereoisomer thereof or a pharma- ceutically acceptable salt thereof.

8. The histone deacetylase 6 mediated disease is an infectious disease; a neoplasm; an endocrine, nutritional and metabolic disease; a mental and behavioral disorder; a neurological disease; an eye and eye adnexal disease; a cardiovascular disease; a respiratory disease; a gastrointestinal disease; a disease of the skin and subcutaneous tissue; a disease of the musculoskeletal system and connective tissue; or a congenital malformation, deformity or chromosomal abnormality. The pharmaceutical composition for preventing or treating a histone deacetylase 6-mediated disease according to claim 7.

9. A method for preventing or treating a histone deacetylase 6-mediated disease, comprising administering, as an active ingredient, a therapeutically effective amount of a compound represented by formula I according to any one of claims 1 to 6, an optical isomer thereof, or a pharma- ceutical acceptable salt thereof.

10. Use of a compound of formula I according to any one of claims 1 to 6, an optical isomer thereof or a pharma- ceutically acceptable salt thereof for the manufacture of a medicament for the prophylaxis or treatment of a histone deacetylase 6-mediated disease.

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