Synthesis method of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidyl) propionic acid

Abstract

The invention discloses a synthesis method of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidyl) propionic acid, and relates to the technical field of synthesis of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidyl) propionic acid, in particular to a synthesis method of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidyl) propionic acid. The invention aims to solve the problem that (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidyl) propionic acid is not easy to produce in batches. The method comprises the following steps: S1, N-Boc-4-piperidine methanol and paratoluensulfonyl chloride are subjected to a reaction at room temperature to obtain 1-N-BOC-4-(4-methylbenzenesulfonyloxymethyl) piperidine; the defects of complex process, low safety, high cost and the like caused by the use of platinum oxide for high-pressure catalytic hydrogenation, flammable and explosive n-butyllithium, expensive chiral reagents and the like in the traditional method are avoided, and large-scale production is successfully realized.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of (2S)-N-Fmoc-3-(1-Boc-4-piperidyl)propionic acid, and specifically to a synthesis method of (2S)-N-Fmoc-3-(1-Boc-4-piperidyl)propionic acid. Background Art

[0002] Farnesoid X receptor (FXR), as a key nuclear receptor for bile acids, plays a core regulatory role in maintaining bile acid and lipid homeostasis. This receptor dynamically regulates physiological balance by controlling the expression network of key genes involved in bile acid synthesis, metabolism, and transport in the liver. In the research and development of farnesoid X receptor antagonists, the structural modification of the piperidine nitrogen atom has been proven to significantly affect its antagonistic activity, which makes the efficient synthesis of related drug intermediates the focus of research. Among them, (2S)-N-Fmoc-3-(1-Boc-4-piperidyl)propionic acid, as a key chiral intermediate, has become an important research object in the field of pharmaceutical intermediates due to its core position in drug synthesis.

[0003] Currently, chiral catalytic synthesis technology is commonly used at home and abroad to directly construct such amino acid skeletons. In patent WO2022 / 192562, a usp30 inhibitor and its uses are disclosed. Referring to paragraph 0535 of the specification, to prepare (2R,5R)-2-(((Chloromethyl)dimethylsilyl)methyl)-5-isopropyl-3,6-dimetho-xy-2,5-dihydropyrazine, (R)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine chiral catalyst is required and paired with strong base n-butyllithium. Since the reaction temperature must be strictly controlled between -65°C and -70°C, the conditions are extremely harsh. In addition, the price of this chiral catalyst is high, and there is a lack of large-scale supply in the market. Its cost even exceeds the target product itself, which makes this synthesis method face great obstacles in kilogram-scale production and large-scale industrial synthesis and is difficult to be popularized and applied. The synthesis route is as follows: .

[0004] The synthesis route in ACS Medicinal Chemistry Letters 2018, 9(2), 78 - 83 is as follows: .

[0005] However, this process has significant drawbacks: the cost of platinum oxide catalyst is high, and the recovery rate of precious metals after the reaction is less than 60%, resulting in an increase in the production cost per batch by about 40%; the reaction needs to be carried out in a high-pressure hydrogen environment of 5-10 MPa, which requires strict requirements for the pressure resistance level and explosion-proof performance of the equipment; the catalyst residue causes the metal impurity content in the final product to be >200 ppm, and an additional chelating chromatography purification step needs to be introduced, resulting in a yield loss of 15%-20%.

[0006] The above defects seriously restrict the large-scale production of this intermediate. Especially when it needs to comply with the ICH Q3D elemental impurity control guideline (platinum limit ≤ 10 ppm) in the declaration of bulk drugs, the existing process needs to carry out multiple rounds of purification treatment, significantly reducing the production efficiency. Therefore, developing a new synthetic process with low cost, atmospheric pressure operation and meeting the requirements of Good Manufacturing Practice (GMP) has become an urgent technical problem in this field. Summary of the Invention

[0007] To solve the above problems, that is, to solve the problems proposed in the above background technology, the present invention proposes a method for synthesizing (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid, which includes the following steps: S1. React N-Boc-4-piperidinemethanol with p-toluenesulfonyl chloride at room temperature to obtain 1-N-BOC-4-(4-methylbenzenesulfonyloxymethyl)piperidine; S2. Condense the product obtained in S1 with diethyl N-acetylaminomalonate to obtain diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate; S3. Hydrolyze the product obtained in S2 with sodium hydroxide and acidify with hydrochloric acid to obtain 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propionic acid; S4. Carry out an enzymatic resolution reaction on the product obtained in S3 with L-acetylase to obtain (2S)-3-(1-tert-butoxycarbonyl-4-piperidyl)propionic acid; S5. Dissolve the product obtained in S4 in a mixed solvent of acetone, water and sodium bicarbonate, add and react with Fmoc-OSu, and after acidifying with hydrochloric acid, obtain (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propionic acid. The synthesis route is as follows: .

[0008] The further setting of the present invention is that in S1, the molar ratio of N-Boc-4-piperidinemethanol to p-toluenesulfonyl chloride is 1:1.05.

[0009] A further setting of the present invention is that in the step S2, the molar ratio of 1-N-BOC-4-(4-methylbenzenesulfonyloxymethyl)piperidine to diethyl N-acetylaminomalonate is 1:1.2, the reaction temperature range is 50-70 °C, and the reaction time is 12-24 h.

[0010] A further setting of the present invention is that in the step S3, the molar ratio of diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate to sodium hydroxide is 1:2.5.

[0011] A further setting of the present invention is that in the step S4, the mass ratio of L-acetylase to 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid is 0.1:1.

[0012] A further setting of the present invention is that in the step S5, the molar ratio of (2S)-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid, sodium bicarbonate and Fmoc-OSu is 1:2.5:1, the purity of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid is ≥98.5%, and the enantiomeric excess value is ≥99.0%.

[0013] The beneficial technical effects of the present invention are as follows: By optimizing the existing synthesis route, the present invention synthesizes a racemic intermediate by a conventional method and combines an enzymatic resolution reaction to prepare an optically pure chiral intermediate. This route avoids harsh conditions such as the use of n-butyllithium and high-pressure catalytic hydrogenation in the traditional method, does not require expensive chiral catalysts and hydrogenation catalysts, and reduces the production cost. At the same time, large-scale production of the product is realized, the purification process is simplified, column chromatography purification is not required, and the reagents used are inexpensive. In addition, this synthesis method conforms to the concept of green chemistry, is environmentally friendly, and provides an effective solution for the synthesis of similar compounds. Description of the Drawings

[0014] Figure 1 Shows the nuclear magnetic resonance hydrogen spectrum of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid in Example 1. Detailed Embodiments

[0015] The following refers to the attached Figure 1 to describe the preferred embodiments of the present invention. Those skilled in the art should understand that these embodiments are only used to explain the technical principle of the present invention and are not intended to limit the protection scope of the present invention.

[0016] Example 1

[0017] S1. Add N-Boc-4-piperidinemethanol (5.0 kg, 23.23 mol) and N,N-dimethylformamide (20 L) into a three-necked flask. Add triethylamine (3.52 kg, 34.85 mol) in an ice bath, and add p-toluenesulfonyl chloride (4.65 kg, 24.39 mol) in batches. Stir the reaction solution at room temperature for 12 h. When the reaction is detected to be complete by TLC, add water (10 L), and extract with ethyl acetate three times (6.0 L each time). Combine the organic phases and rotary evaporate to obtain a colorless liquid, 1-N-BOC-4-(4-methylphenylsulfonyloxymethyl)piperidine (7.0 kg, yield 81.5%), which is directly used for the next step of the reaction; S2. Add 1-N-BOC-4-(4-methylphenylsulfonyloxymethyl)piperidine (7.0 kg, 18.94 mol) and N,N-dimethylformamide (20 L) into a three-necked flask. Cool down to 10 °C, add diethyl N-acetylaminomalonate (4.91 kg, 22.72 mol) and potassium tert-butoxide (2.22 kg, 19.80 mol), and heat to 50 °C for reaction for 16 h. When the reaction is detected to be complete, add water (10 L), and extract with ethyl acetate three times (6.0 L each time). Combine the organic phases and rotary evaporate to obtain a white solid, diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate (5.85 kg, yield 74.6%), which is directly used for the next step of the reaction; S3. Add diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate (5.85 kg, 14.13 mol) into a three-necked flask, add water (10 L) and ethanol (10 L), add sodium hydroxide (1.41 kg, 35.25 mol), and heat to 65 °C and stir for 3 h. Cool down to 25 °C, add hydrochloric acid to adjust the pH to 2 - 3, and extract with ethyl acetate three times (6.0 L each time). Combine the organic phases and rotary evaporate to obtain a white solid, 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid (3.10 kg, yield 69.8%), which is directly used for the next step of the reaction; S4. Add 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid (3.10 kg, 9.87 mol) and distilled water (50 L) into a three-necked flask. Add sodium hydroxide to adjust the pH to about 7.5, stir until clear, heat to 37 °C, add L-acetylase (120 g), and maintain the pH for resolution for 24 h to precipitate a solid. Adjust the pH to 6 - 7 with 2N hydrochloric acid, cool in an ice-water bath, filter, and dry to obtain (2S)-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid (966 g, yield 72%); S5. Add (2S)-3-(1-tert-butyloxycarbonyl-4-piperidinyl)propionic acid (966 g, 3.55 mol), acetone (6 L) and water (6 L) to a three-necked flask, and then add sodium bicarbonate (745 g, 8.87 mol) and Fmoc-OSu (1.12 kg, 3.55 mol); control the pH of the reaction solution to 9.5 with 4N sodium hydroxide, and stir the reaction solution at room temperature for 12 h; extract three times with petroleum ether (3 L each time); acidify the aqueous phase with 1N hydrochloric acid to pH = 3, and extract three times with ethyl acetate (6 L each time); combine the organic phases, wash with saturated brine (5 L), dry with sodium sulfate, filter, and the filtrate is dried to obtain a white solid (2S)-N-fluorenylmethyloxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidinyl)propionic acid (1.47 kg, 2.98 mol, yield 83.9%, Pu: 98.5%, ee: 99.0%).

[0018] H NMR spectrum of (2S)-N-Fluorenylmethyloxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidinyl)propionic acid ( 1 H-NMR) data: 1 H-NMR (400MHz, DMSO-d6) δ1.00-1.04 (m, 2H), 1.38 (m, 9H), 1.55-1.58 (m, 5H), 2.63-2.67 (m, 2H), 3.89-3. 99 (m, 3H), 4.22-4.31 (m, 3H), 7.31-7.44 (m, 4H), 7.65-7.73 (m, 3H), 7.89-7.90 (m, 2H), 12.58 (s, 1H) ppm.

[0019] Key points for structure verification: Compatibility of the Boc and Fmoc groups: The integration of the tert-butyl group (9H) and the aromatic protons of the fluorene ring (9H) is consistent with expectations.

[0020] The distribution of methylene groups on the piperidine ring: total 7H (δ 1.0-1.6) is consistent with the number of remaining protons in the tetrasubstituted piperidine ring.

[0021] Confirmation of the chiral center: The CH of the propionic acid chain (δ 4.2-4.3) was consistent with the optical purity of the 2S configuration (ee>99.8%).

[0022] in conclusion: Should 1 The H-NMR spectrum highly matched the structure of the target compound (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butyloxycarbonyl-4-piperidinyl)propionic acid, and the identification of each signal was clear, further supporting the accuracy of the synthetic route and the high purity of the final product.

[0023] Example 2

[0024] Differently from Example 1: In S1, the reaction solution was stirred at room temperature for 20 h; In S2, it was heated to 70 °C and reacted for 16 h; The rest was the same as in Example 1.

[0025] Although the present invention has been described with reference to the preferred embodiments, various improvements can be made to it and components therein can be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present invention is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

[0026] In the description of the present invention, the terms indicating directions or positional relationships such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] In addition, it should be noted that in the description of the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] The term "comprising" or any other similar term is intended to cover non-exclusive inclusion, so that a process, article or device / equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes the elements inherent in these processes, articles or devices / equipment.

[0029] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or replacements to the relevant technical features, and the technical solutions after these changes or replacements will fall within the protection scope of the present invention.

Claims

1. A method for synthesizing (2S)-N-Fmoc-3-(1-Boc-piperidin-4-yl) propanoic acid, characterized in that: It includes the following steps: S1. N-Boc-4-piperidinemethanol and p-toluenesulfonyl chloride react at room temperature to obtain 1-N-BOC-4-(4-methylphenylsulfonyloxymethyl)piperidine; S2. The product obtained in S1 is condensed with diethyl N-acetylaminomalonate to obtain diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate; S3. The product obtained in S2 is hydrolyzed with sodium hydroxide and acidified with hydrochloric acid to obtain 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid; S4. The product obtained in S3 is subjected to enzymatic resolution reaction with L-acetylase to obtain (2S)-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid; S5. The product obtained in S4 is dissolved in a mixed solvent of acetone, water and sodium bicarbonate, reacted with Fmoc-OSu, and acidified with hydrochloric acid to obtain (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid. The synthesis route is as follows: 。 2. The synthesis method of a (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid according to claim 1, characterized in that: In S1, the molar ratio of N-Boc-4-piperidinemethanol to p-toluenesulfonyl chloride is 1:1.

05.

3. The synthetic method of a (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid according to claim 1, wherein: In S2, the molar ratio of 1-N-BOC-4-(4-methylphenylsulfonyloxymethyl)piperidine to diethyl N-acetylaminomalonate is 1:1.2, the reaction temperature range is 50-70 °C, and the reaction time is 12-24 h.

4. The synthetic method of a (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid according to claim 1, characterized in that: In S3, the molar ratio of diethyl 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)malonate to sodium hydroxide is 1:2.

5.

5. The synthesis method of a (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid according to claim 1, characterized in that: In S4, the mass ratio of L-acetylase to 2-N-acetyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid is 0.1:

1.

6. The synthetic method of a (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl) propionic acid according to claim 1, characterized in that: In S5, the molar ratio of (2S)-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid, sodium bicarbonate and Fmoc-OSu is 1:2.5:1, the purity of (2S)-N-fluorenylmethoxycarbonyl-3-(1-tert-butoxycarbonyl-4-piperidyl)propanoic acid ≥ 98.5%, and the enantiomeric excess value ≥ 99.0%.

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