Preparation method of chiral 2-((1-(5, 6-diphenylpyrazine-2-yl)-3, 3-dimethylpiperidine-4-yl) oxy) acetic acid compound

Abstract

The invention discloses a preparation method of a chiral 2-((1-(5, 6-diphenyl pyrazine-2-yl)-3, 3-dimethyl piperidine-4-yl) oxy) acetic acid compound, and belongs to the technical field of medicinal chemistry. The novel preparation method developed by the invention has the characteristics of short synthetic route, low cost and easiness in industrial amplification, and in addition, the chiral 2-((1-(5, 6-diphenylpyrazine-2-yl)-3, 3-dimethylpiperidine-4-yl) oxy) acetic acid compound has the characteristic of high activity and can be used as an active ingredient for antithrombotic drugs.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical chemistry technology, specifically relating to a method for preparing a chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound. Background Technology

[0002] Prostaglandin I2 (PGI2) is a member of the arachidic acid family of lipids and an antagonist of thromboxanes; reduced synthesis of PGI2 promotes thrombus formation. Activation of the PGI2 receptor (IP receptor) not only inhibits platelet-mediated aggregation but also has a strong vasodilatory effect. IP receptor agonists can treat diseases including pulmonary hypertension (PAH), arteriosclerosis obliterans, coronary artery disease, myocardial infarction, transient ischemic attack, angina pectoris, stroke, ischemia-reperfusion injury, restenosis, atrial fibrillation, intermittent claudication, Raynaud's phenomenon, varicose veins, thrombosis, diabetes, diabetic nephropathy, hypertension, hyperlipidemia, cerebral infarction, rheumatoid arthritis, and chronic obstructive pulmonary disease (COPD).

[0003] Currently marketed PGI2-type drugs generally suffer from problems such as short half-life, poor chemical stability, and significant side effects, resulting in poor efficacy. Therefore, there is an urgent need to develop a non-endogenous PGI2-type IP receptor agonist with a long half-life, good chemical stability, higher selectivity, and fewer side effects.

[0004] Selexipag is the only FDA-approved IP receptor agonist. According to the latest statistics and forecasts from QYResearch, since its launch in 2015, Selexipag's sales have been steadily increasing, from $247 million in 2016 to $1.45 billion in 2023, and the market is projected to grow from $1.64 billion in 2024 to $3.42 billion in 2030. Selexipag is taken twice daily and is rapidly hydrolyzed after oral absorption to the active metabolite MRE-269 (ACT-333679). MRE-269 exhibits high selectivity for the IP receptor. While existing technologies for modifying the flexible chain of MRE-269 have disclosed the synthesis of a highly active 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound and its chiral resolution preparation method, the chiral resolution preparation method is limited to laboratory testing. Summary of the Invention

[0005] To address the aforementioned shortcomings in the prior art, this invention provides a method for preparing a chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound. This novel preparation method features a short synthetic route, low cost, and ease of industrial scale-up. Furthermore, the chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound exhibits high activity and can be used as an active ingredient in antithrombotic drugs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is as follows: A method for preparing a chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound, comprising the following steps: (1) Add (-)-diisopinepine chloroborane or (+)-diisopinepine chloroborane solution to a 1-Boc-3,3-dimethyl-4-oxoperidine solution and react at 3-5°C for 2-6 days to obtain the compound shown in IIS or IIR; the compound shown in IIS is: The compound shown in the IIR is ; (2) Add acid to the compound solution obtained in step (1) to remove protection, and react at room temperature for 2-24 hours to obtain the compound as shown in ILS or IIIR; the compound shown in ILS is: The compound shown in IIIR is Its absolute configuration was determined by the Mosher ester method. IIS-(S)Mosher ester and IIS-(R)Mosher ester were obtained by reacting IIS with (S)Mosher acid and (R)Mosher acid, respectively. NMR analysis revealed that the chemical shifts of the hydrogens at the 5 and 6 carbon positions in the IIS-(S)Mosher ester were smaller than those in the IIS-(R)Mosher ester, δ... S <δ R The chemical shifts of the hydrogens at carbons 2, 7, and 8 in IIS-(S)Mosher ester are larger than those in IIS-(R)Mosher ester, δ S >δ R The IIS configuration is determined to be S-type.

[0007] (3) The compound obtained in step (2), 5-chloro-2,3-diphenylpyrazine, and a base are mixed and dissolved, and then reacted at 100-200℃ for 8-48 h to obtain the compound shown in IVS or IVR; the compound shown in IVS is The compound shown in the IVR is ; (4) The compound obtained in step (3), tert-butyl bromoacetate, and the catalyst are co-dissolved in a mixed solution. After stirring for 30-45 minutes, the mixture is naturally heated to room temperature and the reaction continues for 0.5-3 hours to obtain the compound shown in VS or VR; the compound shown in VS is The compound shown in VR is ; (5) Under ice bath conditions, the compound obtained in step (4) is mixed with alkali and dissolved, and reacted for 2 to 10 hours. Then, it is acidified and extracted to obtain the chiral compound, whose structural formula is shown in IS or IR.

[0008] Further, in step (1), the molar ratio of 1-Boc-3,3-dimethyl-4-oxopiperidine to (-)-diisopinepine chloride or (+)-diisopinepine chloride is 1:1 to 1:3.

[0009] Further, in step (1), the molar ratio of 1-Boc-3,3-dimethyl-4-oxopiperidine to (-)-diisopinepine chloride or (+)-diisopinepine chloride is 1:1.1.

[0010] Furthermore, in step (1), (-)-diisopinepine chloroborane or (+)-diisopinepine chloroborane is added at 0°C, and the reaction time is 4 days.

[0011] Furthermore, the organic solvent used in step (1) is tetrahydrofuran, diethyl ether, or N,N-diisopropylmethylamine.

[0012] Furthermore, in step (2), the volume ratio of the organic solvent used to dissolve the compound obtained in step (1) to the deprotected acid solution is 1:2 to 4:1, and the reaction time is 12h.

[0013] Furthermore, in step (2), the volume ratio of the organic solvent used to dissolve the compound obtained in step (1) to the deprotected acid solution is 2:1 or 1:2.

[0014] Furthermore, in step (2), the organic solvent is dichloromethane, trichloromethane, or ethyl acetate. Furthermore, the acid solution used for deprotection in step (2) is trifluoroacetic acid or 2N ethyl acetate hydrochloric acid solution.

[0015] Furthermore, in step (3), the molar ratio of 5-chloro-2,3-diphenylpyrazine, the compound obtained in step (2), and the base is 1:1~3:0~3.

[0016] Furthermore, the organic solvent used in step (3) is N-methylpyrrolidone or N,N-diisopropylmethylamine.

[0017] Furthermore, the base used in step (3) is potassium carbonate, triethylamine, or N,N-diisopropylethylamine.

[0018] Furthermore, in step (4), the molar ratio of the compound obtained in step (3), tert-butyl bromoacetate, and the catalyst is 1:1~3:0.5~2. Furthermore, the catalyst in step (4) is tetrabutylammonium hydrogen sulfate.

[0019] Furthermore, the mixed solution in step (4) is made by mixing equal volumes of toluene and a 40wt% KOH solution.

[0020] The chiral compounds prepared by the above method are used in the preparation of IP receptor agonists.

[0021] The beneficial effects of this invention are: The novel preparation method developed in this invention features a short synthetic route, low cost, high yield, and ease of industrial scale-up. Furthermore, in vitro antiplatelet aggregation activity assays revealed that the prepared chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound exhibits high antiplatelet aggregation activity, enabling it to function as an active ingredient in antithrombotic and vasodilator drugs and exert superior thrombosis prevention and treatment effects. Attached Figure Description

[0022] Figure 1 Two-dimensional NMR HSQC image of IIS-(S)Mosher ester. Detailed Implementation

[0023] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0024] Example 1 (R)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IR), its structural formula is as follows: The preparation method is as follows: (1) Preparation of (R)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester (IIR) 1-Boc-3,3-dimethyl-4-oxopiperidine (908 mg, 4.00 mmol) was dissolved in diethyl ether (4 mL) at 0 °C, and a solution of (+)-diisopinepinechloroborane in n-hexane (60 wt. % in heptane, 2.6 mL, 4.40 mmol) was added dropwise. The reaction was stirred at 5 °C for 4 days. Then, diethanolamine (1.8 g) was added to the reaction, producing a large amount of white precipitate. The mixture was stirred vigorously at room temperature for 3 h, filtered, washed with ethyl acetate, and the filtrate was concentrated and purified by silica gel column chromatography to obtain (R)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester IIR (767 mg, 84% yield, 93.1% ee). The configuration of the enantiomeric IIR was determined by the Mosher ester method. 1 ¹H NMR (600 MHz, CDCl₃) δ 3.81 (d, J = 51.0 Hz, 1H), 3.59–3.43 (m, 1H), 3.38 (dd, J = 9.2, 4.1 Hz, 1H), 3.01 (s, 1H), 2.70 (d, J = 13.3 Hz, 1H), 1.86 (s, 1H), 1.71 (s, 1H), 1.48–1.58 (m, 1H), 1.42 (s, 9H), 0.93 (s, 3H), 0.86 (s, 3H). HPLC analysis (chiral column CHIRALPAK AD-H column (5 μm, 250 mm × 4.6 mm), mobile phase: V 正己烷 V 异丙醇 =90:10, retention time 8.37 min).

[0025] (2) Preparation of (R)-3,3-dimethyl-4-hydroxypiperidine (IIIR) (R)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester IIR (458 mg, 2.00 mmol) was dissolved in dichloromethane (2 mL), and trifluoroacetic acid (1.0 mL) was added. The reaction mixture was stirred at room temperature for 12 h, followed by the addition of ice water (5 mL). The mixture was extracted with ethyl acetate (3 × 5 mL), and the organic layers were combined and washed successively with water (5 mL) and saturated brine (5 mL). The solution was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure to obtain 260 mg of (R)-3,3-dimethyl-4-hydroxypiperidine IIIR compound, which was used directly in the next step without purification. MS (ESI) + , m / z): 130.2 [M+H] + . (3) Preparation of (R)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (IVR) Under nitrogen protection, 5-chloro-2,3-diphenylpyrazine (502 mg, 1.88 mmol), potassium carbonate (519 mg, 3.76 mmol), and (R)-3,3-dimethyl-4-hydroxypiperidine (292 mg, 2.26 mmol) were added to 5 mL of N-methylpyrrolidone (NMP). The mixture was heated to 140 °C and reacted for 24 h. The reaction was monitored by LC-MS until the reactants were completely reacted. The reaction mixture was cooled and ice water was added. The mixture was extracted with ethyl acetate, and the organic mixed phase was washed with water and saturated brine, dried over Na2SO4, filtered, solvent removed under reduced pressure, and purified by silica gel column chromatography. The purified phase was collected under reduced pressure and dried under vacuum to give (R)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidine-4-ol (640 mg, 94%). ESI-MS: m / z = 360.2 (M+H) + . 1 H NMR (600MHz, CDCl3) δ 8.14 (s, 1H), 7.45 – 7.41 (m, 2H), 7.35 – 7.32 (m, 2H), 7.29 –7.26 (m, 1H), 7.26 – 7.18 (m, 5H), 4.26 – 4.18 (m, 1H), 3.84 (dd, J = 13.2,1.7 Hz, 1H), 3.52 (dd, J = 9.2, 4.1 Hz, 1H), 3.34 – 3.27 (m, 1H), 3.00 (d, J= 13.2 Hz, 1H), 1.93 – 1.87 (m, 1H), 1.72 (td, J = 9.4, 4.2 Hz, 2H), 1.05 (s,3H), 0.97 (s, 3H). (4) Preparation of (R)-2-((1-(5,6-diphenylpyrazin-2-yl)3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate (VR) Under ice bath conditions, (R)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (154 mg, 0.43 mmol), tetrabutylammonium bisulfate (75 mg, 0.22 mmol), and tert-butyl bromoacetate (125 mg, 0.64 mmol) were added sequentially to a mixture of 4 mL toluene and 2 mL 40% KOH. The mixture was stirred vigorously for 30 min, allowed to warm naturally to room temperature, and reacted for 2 h. Ice water was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic mixed phase was washed with water and saturated brine, dried over MgSO4, filtered, solvent removed under reduced pressure, purified by silica gel column chromatography, collected under reduced pressure, and dried under vacuum to give 180 mg of (R)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate, yield: 88%. ESI-MS: m / z = 474.2 (M+H) + .

[0026] (5) Preparation of (R)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IR) Under ice bath conditions, tert-butyl (R)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (152 mg, 0.32 mmol) and LiOH (31.0 mg, 1.30 mmol) were added sequentially to 10 mL of MeOH solution. The reaction was allowed to proceed overnight. Methanol was removed under reduced pressure. 5 mL of ice water and 5 mL of ethyl acetate were added to the reaction solution, and the pH was adjusted to 5-6 with 2N HCl. The mixture was extracted with ethyl acetate, washed with water and saturated brine, dried over MgSO4, filtered, solvent removed under reduced pressure, and purified by silica gel column chromatography. The purified solution was collected under reduced pressure and dried under vacuum to give (R)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (121 mg, 91% yield, 90.9% ee). ESI-MS: m / z = 418.2 (M+H) + ; 1¹H NMR (400 MHz, DMSO-d6) δ 8.27 (s, 1H), 7.38 – 7.16 (m, 10H), 4.09 (d, J = 13.1 Hz, 2H), 3.71 (dd, J = 22.7, 7.8 Hz, 2H), 3.21 (dd, J = 27.0, 9.3 Hz, 2H), 3.01 (d, J = 13.1 Hz, 1H), 1.90 (d, J = 8.6 Hz, 1H), 1.56 (d, J = 9.0 Hz, 1H), 0.97 (s, 3H), 0.87 (s, 3H). HPLC analysis (chiral column OJ-RH (5 μm, 250 mm × 4.6 mm), mobile phase: V 甲醇 V 0.5%甲酸水 =85:15, retention time 42.78 min) Example 2 (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IS), its structural formula is as follows: The preparation method is as follows: (1) Preparation of (S)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester (IIS) At 0 °C, 1-Boc-3,3-dimethyl-4-oxopiperidine (908 mg, 4.00 mmol) was dissolved in tetrahydrofuran (4 mL), and a solution of (-)-diisopinepinechloroborane in n-hexane (60 wt. % in heptane, 2.6 mL, 4.40 mmol) was added dropwise. The reaction was stirred at 5 °C for 4 days. Then, diethanolamine (1.8 g) was added to the reaction mixture, resulting in a large amount of white precipitate. The mixture was stirred vigorously at room temperature for 3 h, filtered, and washed with ethyl acetate. The filtrate was concentrated and purified by silica gel column chromatography to obtain (S)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester IIS (720 mg, 80% yield, 93.2% ee). The configuration of the enantiomeric IIS was determined by the Mosher ester method. 1¹H NMR (600 MHz, CDCl₃) δ 3.81 (d, J = 51.0 Hz, 1H), 3.59 – 3.43 (m, 1H), 3.38 (dd, J = 9.2, 4.1 Hz, 1H), 3.01 (s, 1H), 2.70 (d, J = 13.3 Hz, 1H), 1.86 (s, 1H), 1.71 (s, 1H), 1.48 – 1.58 (m, 1H), 1.42 (s, 9H), 0.93 (s, 3H), 0.86 (s, 3H). HPLC analysis (chiral column CHIRALPAK AD-H column (5 μm, 250 mm × 4.6 mm), mobile phase: V 正己烷 V 异丙醇 =90:10, retention time 9.48 min) (2) Preparation of (S)-3,3-dimethyl-4-hydroxypiperidine (IIIS) (S)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester IIs (458 mg, 2.00 mmol) was dissolved in ethyl acetate (2 mL). After adding 2N ethyl acetate-hydrochloric acid solution (4.0 mL), the reaction mixture was stirred at room temperature for 4 h. The solid was filtered, washed with ethyl acetate, and then subjected to ice water (5 mL) and ethyl acetate (5 mL). The pH was adjusted to 8 with saturated sodium bicarbonate, and the mixture was extracted with ethyl acetate (3 × 5 mL). The organic layers were combined and washed successively with water (5 mL) and saturated brine (5 mL). The mixture was dried over anhydrous sodium sulfate, filtered, and the solvent was removed under reduced pressure to obtain 265 mg of (S)-3,3-dimethyl-4-hydroxypiperidine IIIs, which was used directly in the next reaction without purification. MS (ESI) + , m / z): 130.2 [M+H] + . (3) Preparation of (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (IVS) Under nitrogen protection, 5-chloro-2,3-diphenylpyrazine (502 mg, 1.88 mmol), potassium carbonate (519 mg, 3.76 mmol), and (S)-3,3-dimethyl-4-hydroxypiperidine (292 mg, 2.26 mmol) were added to 5 mL of N,N-diisopropylmethylamine. The mixture was heated to 120 °C and reacted for 24 h. The reaction was monitored by LC-MS until the reactants were completely reacted. The reaction mixture was cooled and ice water was added. The mixture was extracted with ethyl acetate, and the organic mixed phase was washed with water and saturated brine, dried over Na₂SO₄, filtered, solvent removed under reduced pressure, and purified by silica gel column chromatography. The purified phase was collected under reduced pressure and dried under vacuum to give (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidine-4-ol (620 mg, 92%). ESI-MS: m / z = 360.2 (M+H) + . 1 H NMR (600 MHz, CDCl3) δ 8.14 (s, 1H), 7.45 – 7.41 (m, 2H), 7.35 – 7.32 (m, 2H), 7.29 – 7.26 (m, 1H), 7.26 – 7.18 (m, 5H), 4.26 – 4.18 (m, 1H), 3.84 (dd, J = 13.2, 1.7Hz, 1H), 3.52 (dd, J = 9.2, 4.1 Hz, 1H), 3.34 – 3.27 (m, 1H), 3.00 (d, J =13.2 Hz, 1H), 1.93 – 1.87 (m, 1H), 1.72 (td, J = 9.4, 4.2 Hz, 2H), 1.05 (s, 3H), 0.97 (s, 3H). (4) Preparation of (S)-2-((1-(5,6-diphenylpyrazin-2-yl)3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate (VS) Under ice bath conditions, (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (154 mg, 0.43 mmol), tetrabutylammonium bisulfate (75 mg, 0.22 mmol), and tert-butyl bromoacetate (125 mg, 0.64 mmol) were added sequentially to a mixture of 4 mL toluene and 2 mL 40% KOH. The mixture was stirred vigorously for 45 min, allowed to warm naturally to room temperature, and reacted for 3 h. Ice water was added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic mixed phase was washed with water and saturated brine, dried over Na2SO4, filtered, solvent removed under reduced pressure, purified by silica gel column chromatography, collected under reduced pressure, and dried under vacuum to give 190 mg of (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate, yield: 94%. ESI-MS: m / z = 474.2 (M+H) + .

[0027] (5) Preparation of (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IS) Under ice bath conditions, tert-butyl (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (152 mg, 0.32 mmol) and 2N NaOH (5 mL, 10 mmol) were added sequentially to 5 mL of MeOH solution. The reaction was allowed to proceed overnight. Methanol was removed under reduced pressure. 5 mL of ice water and 5 mL of ethyl acetate were added to the reaction solution, and the pH was adjusted to 5-6 with 2N HCl. The mixture was extracted with ethyl acetate, washed with water and saturated brine, dried over Na2SO4, filtered, solvent removed under reduced pressure, and purified by silica gel column chromatography. The purified solution was collected under reduced pressure and dried under vacuum to give (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (125 mg, 94% yield, 93.3% ee). ESI-MS: m / z = 418.2 (M+H) + ; 1¹H NMR (400 MHz, DMSO-d6) δ 8.27 (s, 1H), 7.38 – 7.16 (m, 10H), 4.09 (d, J = 13.1 Hz, 2H), 3.71 (dd, J = 22.7, 7.8 Hz, 2H), 3.21 (dd, J = 27.0, 9.3 Hz, 2H), 3.01 (d, J = 13.1 Hz, 1H), 1.90 (d, J = 8.6 Hz, 1H), 1.56 (d, J = 9.0 Hz, 1H), 0.97 (s, 3H), 0.87 (s, 3H). HPLC analysis (chiral column OJ-RH (5 μm, 250 mm × 4.6 mm), mobile phase: V 甲醇 V 0.5%甲酸水 =85:15, retention time 36.16 min) Example 3 (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IS), its structural formula is as follows: The preparation method is as follows: (1) Scale-up preparation of (S)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester (IIS) At 0 °C, 1-Boc-3,3-dimethyl-4-oxoperpiperidine (90.8 g, 400 mmol) was dissolved in tetrahydrofuran (400 mL), and a solution of (-)-diisopinepinechloroborane in n-hexane (60 wt. % in heptane, 260 mL, 440 mmol) was added dropwise. The reaction was stirred at 5 °C for 6 days. Then, diethanolamine (180 g) was added to the reaction, producing a large amount of white precipitate. The mixture was stirred vigorously at room temperature for 3 h, filtered, and washed with ethyl acetate. The filtrate was concentrated, and the unpurified filtrate was used directly in the next reaction. HPLC analysis (93.0% ee, chiral column CHIRALPAK AD-H column (5 μm, 250 mm × 4.6 mm), mobile phase: V 正己烷 V 异丙醇 =90:10, retention time 9.48 min) (2) Scale-up preparation of (S)-3,3-dimethyl-4-hydroxypiperidine (IIIS) (S)-4-hydroxy-3,3-dimethylpiperidine-1-carboxylic acid tert-butyl ester II (45.8 g, 200 mmol) was dissolved in ethyl acetate (100 mL). After adding 2N ethyl acetate-hydrochloric acid solution (200 mL), the reaction mixture was stirred at room temperature for 4 h. The solid was filtered, washed with ethyl acetate, and then the solid was added to ice water and ethyl acetate. The pH was adjusted to 8 with saturated sodium bicarbonate, and the mixture was extracted with ethyl acetate (3 × 200 mL). The organic layers were combined, washed with water, dried over anhydrous sodium sulfate, and the solvent was removed under reduced pressure. The solid was dissolved in 95% ethanol, and then 1.05 equivalents of tartaric acid were added to form a salt. After recrystallization, the solid was filtered, and the solid was freed with 3M NaOH solution. Extraction with EA and solvent removal under reduced pressure yielded (S)-3,3-dimethyl-4-hydroxypiperidine IIIS compound (24 g, 93% overall yield). MS (ESI) + ,m / z): 130.2 [M+H] + . (3) Scale-up preparation of (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (IVS) Under nitrogen protection, 5-chloro-2,3-diphenylpyrazine (25.1 g, 94 mmol), potassium carbonate (26 g, 188 mmol), and (S)-3,3-dimethyl-4-hydroxypiperidine (29.2 g, 113 mmol) were added to 200 mL of N,N-diisopropylmethylamine. The mixture was heated to 120 °C and reacted for 24 h. The reaction was monitored by LC-MS until the reactants were completely reacted. The reaction mixture was cooled and ice water was added. The mixture was extracted with ethyl acetate. The organic mixed phase was washed with water and saturated brine, dried over Na₂SO₄, filtered, and the solvent was removed under reduced pressure. The mixture was collected under reduced pressure and recrystallized from a mixture of ethyl acetate and petroleum ether. After filtration and vacuum drying, (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidine-4-ol (30 g, 89%) was obtained. ESI-MS: m / z = 360.2 (M+H) + .

[0028] (4) Scale-up preparation of (S)-2-((1-(5,6-diphenylpyrazin-2-yl)3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate (VS) Under ice bath conditions, (S)-1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-ol (15.4 g, 43 mmol) and tetrabutylammonium hydrogen sulfate (7.5 g, 22 mmol) were added sequentially to a mixture of 200 mL toluene and 200 mL 40% KOH. Then, tert-butyl bromoacetate (12.5 g, 64 mmol) was slowly added dropwise. The mixture was stirred vigorously for 45 min, allowed to warm naturally to room temperature, and reacted for 3 h. If the reaction was incomplete, one equivalent of tert-butyl bromoacetate could be added dropwise. After the reaction was complete, ice water was added to the reaction solution, and the mixture was extracted with ethyl acetate. The organic mixed phase was washed with water and saturated brine, dried over Na2SO4, filtered, collected under reduced pressure, recrystallized from a mixture of ethyl acetate and petroleum ether, filtered, and dried under vacuum to obtain (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)tert-butyl acetate (18 g, 18 mmol). g, 90%). ESI-MS: m / z = 474.2 (M+H) + .

[0029] (5) Scale-up preparation of (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (IS) Under ice bath conditions, tert-butyl (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (15.2 g, 32 mmol) and 2N NaOH (100 mL, 200 mmol) were added sequentially to 100 mL of MeOH solution. The reaction was allowed to proceed overnight. Methanol was removed under reduced pressure. 100 mL of ice water and 200 mL of ethyl acetate were added to the reaction solution, and the pH was adjusted to 5-6 with 2N HCl. The mixture was extracted with ethyl acetate, washed with water and saturated brine, dried over Na₂SO₄, and collected under reduced pressure. The mixture was recrystallized from a mixture of ethyl acetate and petroleum ether, filtered, and dried under vacuum to obtain (S)-2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid (12 g, 90% yield). ESI-MS: m / z = 418.2 (M+H) + HPLC analysis (chiral column OJ-RH (5 μm, 250 mm × 4.6 mm), mobile phase: V 甲醇 V 0.5%甲酸水 =85:15, retention time 36.16 min) Preparation Example 1 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butoxy}acetic acid (MRE-269) has the following structural formula: The preparation was carried out according to the method disclosed in Example 42 of patent CN1516690A, yielding a yellow oily 2-{4-[N-(5,6-diphenylpyrazin-2-yl)-N-isopropylamino]butoxy}acetic acid (MRE-269), ESI-MS: m / z = 420.2 (M+H). + ; 1 H NMR (400 MHz, d6-DMSO) δ 12.59 (s, 1H), 8.14 (s, 1H), 7.38 –7.21 (m, 10H), 4.82 – 4.74 (m, 1H), 4.00 (s, 2H), 3.53 – 3.33 (m, 4H), 1.69 –1.61 (m, 4H), 1.22 (d, J = 6.8 Hz, 6H).

[0030] Preparation of Mosher esters: (S)-4-hydroxy-3,3-dimethylpiperidin-1-carboxylic acid tert-butyl ester (IIS) (50 mg, 0.22 mmol) was added to a test tube, followed by 2 mL of dichloromethane and stirring until completely dissolved. Then, (S)-MTPA (61 mg, 0.26 mmol), DCC (68 mg, 0.33 mmol), and DMAP (5 mg) were added. The mixture was stirred at room temperature for 12 h, and the reaction progress was monitored by TLC. After the reaction was complete, the mixture was filtered, and the residue was washed with ethyl acetate. The filtrate was dried over anhydrous sodium sulfate, concentrated under reduced pressure to remove most of the solvent, and the residue was purified by plate separation to obtain 17 mg of IIS-(S)Mosher ester.

[0031] IIS-(S)Mosher ester 1 H NMR (600 MHz, CDCl3) δ 7.51 – 7.49 (m, 2H), 7.42 – 7.39 (m, 3H), 4.82 (dd, J = 7.9, 3.7 Hz, 1H), 3.51 (s, 3H), 3.48 – 3.46 (m, 1H), 3.30 –3.27 (m, 2H), 3.00 (d, J = 13.4 Hz, 1H), 1.94 – 1.90 (m, 1H), 1.71 – 1.64 (m,1H), 1.43 (s, 9H), 0.95 (s, 3H), 0.87 (s, 3H). 13C NMR (151 MHz, CDCl3) δ165.09, 153.80, 131.04, 128.64, 127.43, 126.39, 123.33, 121.42, 98.97, 83.82,83.63, 78.69, 78.65, 54.33, 51.67, 38.96, 33.96, 28.68, 27.36, 23.09, 19.24. (S)-4-hydroxy-3,3-dimethylpiperidin-1-carboxylic acid tert-butyl ester (IIS) (50 mg, 0.22 mmol) was added to a test tube, followed by 2 mL of dichloromethane and stirring until completely dissolved. Then, (R)-MTPA (61 mg, 0.26 mmol), DCC (68 mg, 0.33 mmol), and DMAP (5 mg) were added. The mixture was stirred at room temperature for 12 h, and the reaction progress was monitored by TLC. After the reaction was complete, the mixture was filtered, and the residue was washed with ethyl acetate. The filtrate was dried over anhydrous sodium sulfate, concentrated under reduced pressure to remove most of the solvent, and the residue was purified by plate separation to obtain 28 mg of IIS-(R)Mosher ester.

[0032] IIS-(R)Mosher ester 1 H NMR (600 MHz, CDCl3) δ 7.53 – 7.49 (m, 2H), 7.42 – 7.39 (m, 3H), 4.87 (dd, J = 8.5, 3.9 Hz, 1H), 3.74 – 3.61 (m, 1H), 3.54 (s, 3H), 3.41 –3.35 (m, 1H), 3.26 – 3.20 (m, 1H), 2.92 (d, J = 13.5 Hz, 1H), 1.94 – 1.90 (m,1H), 1.74 – 1.67 (m, 1H), 1.43 (s, 9H), 0.89 (s, 3H), 0.84 (s, 3H). Experimental Example 1: In vitro platelet aggregation test 1. Experimental Objective The antiplatelet aggregation activity of the compounds in this invention was evaluated by studying their inhibitory effect on ADP-induced platelet aggregation in vitro.

[0033] 2. Test materials 2.1 Test Materials Fully automated platelet aggregation analyzer (Talitaikang AG800); ADP (Sigma); DMSO, 0.9% sodium chloride injection, sodium hydroxide, blood collection tubes, etc.

[0034] 2.2 Laboratory Animals Domestic rabbit, male, 2.1±0.2kg.

[0035] 2.3 Test Drug The compounds of Examples 1 and 2, and the compound of Preparation Example 1.

[0036] 3. Test methods 3.1 Preparation of the test solution Weigh each of the above test drugs and prepare a stock solution with a concentration of 200mM using DMSO. After fully dissolving and mixing, take the stock solution and add 0.9% sodium chloride injection to prepare a series of test solutions of different concentrations (0.15μM-50μM). 3.2 Preparation of PRP and PPP Rabbit blood was collected in plastic centrifuge tubes and anticoagulated with 3.2% sodium citrate (the ratio of anticoagulant to whole blood was 1:9). The blood was centrifuged at 140g for 10 minutes, and the supernatant was carefully aspirated to obtain PRP. The remaining plasma was centrifuged at 2000g for 10 minutes, and the supernatant was obtained to obtain PPP.

[0037] 3.3 Preparation of ADP solution Weigh out ADP and dissolve it in 0.9% sodium chloride injection to prepare ADP stock solution. Aliquot the stock solution into centrifuge tubes and store at -20°C. Reconstitute before use and dilute to 300 μM with 0.9% sodium chloride injection.

[0038] 3.4 Maximum Aggregation Rate Detection

[0039] After powering on the platelet aggregation analyzer, preheat for 30 minutes until the temperature reaches 37°C before starting the test. Place 270 μL of PRP and 30 μL of the test solution into the PRP cup of the double-cup system, and place 300 μL of PPP into the PPP cup of the double-cup system. The instrument will then begin the test. Calculate the maximum platelet aggregation rate induced by ADP at a concentration of 100 μM. Based on the platelet aggregation rate, calculate the IC50 of the compound for platelet aggregation. 50 4. Experimental Data Results Table 1. Inhibitory effect of compounds from the examples and preparation examples on platelet aggregation. The experimental results above show that the compound prepared in Example 1 exhibits an in vitro inhibitory effect on platelet aggregation (ICP-C). 50 The concentration was 6.2 μM, while the IC50 of the compounds in Examples 1 and 2 of this invention for inhibiting platelet aggregation in vitro was 6.2 μM.50 The concentrations were 1.25 μM and 0.15 μM, respectively. It can be seen that the compounds of Example 1 and Example 2 had a better inhibitory effect on platelet aggregation than those of Preparation Example 1, with the compound of Example 2 showing the greatest inhibitory effect on platelet aggregation. Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a chiral 2-((1-(5,6-diphenylpyrazin-2-yl)-3,3-dimethylpiperidin-4-yl)oxy)acetic acid compound, characterized in that, Includes the following steps: (1) Add (-)-diisopinepine chloroborane or (+)-diisopinepine chloroborane solution to a 1-Boc-3,3-dimethyl-4-oxoperidine solution and react at 3-5°C for 2-6 days to obtain compounds as shown in IIS or IIR, respectively; the compound shown in IIS is: The compound shown in the IIR is ; (2) Add acid to the compound solution obtained in step (1) to remove protection, and react at room temperature for 2-24 hours to obtain a compound as shown in ILS or IIIR; the compound shown in ILS is: ; The compound shown in IIIR is ; (3) The compound obtained in step (2), 5-chloro-2,3-diphenylpyrazine, and a base are mixed and dissolved, and then reacted at 100-200°C for 8-48 hours to obtain a compound as shown in IVS or IVR; the compound shown in IVS is The compound shown in the IVR is ; (4) The compound obtained in step (3), tert-butyl bromoacetate, and the catalyst are co-dissolved in a mixed solution. After stirring for 30-45 minutes, the mixture is naturally heated to room temperature and the reaction continues for 0.5-3 hours to obtain a compound as shown in VS or VR; the compound shown in VS is The compound shown in VR is ; (5) Under ice bath conditions, the compound obtained in step (4) is mixed with alkali and dissolved, reacted for 2-10 hours, and then acidified and extracted to obtain the chiral compound.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of 1-Boc-3,3-dimethyl-4-oxopiperidine to (-)-diisopinepine chloride or (+)-diisopinepine chloride is 1:1 to 1:

3.

3. The preparation method according to claim 1, characterized in that, The acid solution used for deprotection in step (2) is trifluoroacetic acid or 2N ethyl acetate hydrochloric acid solution.

4. The preparation method according to claim 1, characterized in that, In step (2), the volume ratio of the organic solvent used to dissolve the compound obtained in step (1) to the deprotected acid solution is 1:2 to 4:

1.

5. The preparation method according to claim 1, characterized in that, In step (3), the molar ratio of 5-chloro-2,3-diphenylpyrazine, the compound obtained in step (2), and the base is 1:1~3:0~3.

6. The preparation method according to claim 1 or 5, characterized in that, The base used in step (3) is potassium carbonate, triethylamine, or N,N-diisopropylethylamine.

7. The preparation method according to claim 1, characterized in that, In step (4), the molar ratio of the compound obtained in step (3), tert-butyl bromoacetate and catalyst is 1:1~3:0.5~2.

8. The preparation method according to claim 1 or 7, characterized in that, The catalyst in step (4) is tetrabutylammonium hydrogen sulfate.

9. The preparation method according to claim 1, characterized in that, The mixed solution in step (4) is made by mixing equal volumes of toluene and a 40wt% KOH solution.

10. Use of the chiral compound prepared by the method according to any one of claims 1 to 9 in the preparation of IP receptor agonists.

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