An N-methyl amino acid compound and a preparation method thereof
By using a reaction system of formaldehyde, tetrahydropyrrole, and hexafluoroisopropanol, N-methyl amino acids can be synthesized under mild conditions, solving the problems of poor selectivity and high cost in existing technologies, and realizing the efficient and simple synthesis of amino acid compounds.
Patent Information
- Application Number
- CN202311272403.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-28
- Publication Date
- 2026-01-02
- Estimated Expiration
- 2043-09-28
AI Technical Summary
Existing technologies suffer from poor selectivity, high cost, and difficulty in separation when synthesizing N-methyl amino acids, and their application is particularly limited in the later modification of peptides and proteins.
Formaldehyde was used as a methylating agent to form an imine intermediate with the amino group of amino acids. Tetrahydropyrrole was used as a hydrogen donor and hexafluoroisopropanol was used as a proton shuttle. Under mild conditions, the co-transfer of hydrogen and protons between molecules was achieved to synthesize single-selective N-methyl amino acids.
This method enables the efficient and selective synthesis of N-methyl amino acids under mild reaction conditions, with recyclable solvents, simple post-processing, and no need for column chromatography separation and purification. It is applicable to different types of amino acid compounds.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of chemical synthesis of amino acids, and particularly relates to an N-methyl amino acid compound and a preparation method thereof. BACKGROUND
[0002] Lysine (Lys) is an important proteinogenic amino acid (AA) that plays an indispensable role in controlling the functional and physicochemical properties of peptides and proteins (Chem. Soc. Rev. 2015, 44, 5495). Nature has constructed a series of enzyme-catalyzed post-translational modification (PTM) pathways on the epsilon-NH2 side chain of lysine (Cell Chem. Biol. 2020, 27, 953). Among them, the methylation of Nε-lysine is one of the most important PTMs in the field of cellular functional epigenetics control (Chem Rev. 2018, 118, 6656). In addition to PTMs, the lysine side chain in peptides and proteins is also a coveted handle in various bioconjugation applications. Despite the remarkable progress made over the past half century, the exploration of new methods for selectively modifying lysine has never ceased.
[0003] Nature widely uses the backbone N-methylation of various alpha-amino acid units to regulate the physicochemical properties of peptide natural products, especially membrane permeability (Acc. Chem. Res. 2008, 41, 1331). Although the N-methylation structure looks simple, the preparation of secondary methyl alkyl amines is still a problem, mainly due to the presence of a competitive N,N-dimethylation side reaction and the difficulty of separating these homologues (Chem. Rev. 2004, 104, 5823). The current method for the mono-selective N-methylation of primary alkyl amines mainly requires the use of a blocking group to block one of the N-H bonds. This necessity greatly increases the cost of synthesizing N-methylated-amino acid building blocks and limits their application in the late-stage modification of complex molecules such as peptides.
[0004] Therefore, it is necessary to develop a better method for synthesizing N-methyl amino acid compounds. SUMMARY
[0005] In view of the above-mentioned technical defects of the prior art, the purpose of the present application is to provide an N-methyl amino acid compound and a preparation method thereof. The present application uses formaldehyde as a methylation modification reagent, an imine intermediate formed by the amino group of the amino acid as a negative hydrogen acceptor, adds tetrahydro-pyrrole as a negative hydrogen donor, and uses hexafluoroisopropanol solvent as a proton shuttle to transfer negative hydrogen and protons. Under mild conditions, the intermolecular negative hydrogen and protons are cooperatively transferred, and the N-methyl amino acid compound with single selectivity can be efficiently synthesized. The present application requires simple samples, small amount, clean reaction system, and recyclable solvent. After the reaction, only simple purification treatment is required, and column chromatography separation and purification are not required, which can be applied to the methylation modification of amino acids without active side chain amino acids. The formaldehyde / tetrahydro-pyrrole / hexafluoroisopropanol reaction system in the present application provides a convenient and effective post-modification method for introducing a methyl group with single selectivity into the amino group of different α, β, γ-amino acids, and has potential synthetic applications.
[0006] To achieve the above purpose, the technical scheme of the present application is as follows:
[0007] One of the purposes of the present application is to provide a method for preparing an N-methyl amino acid compound, comprising the following steps:
[0008] reacting an amino acid compound, formaldehyde, and a negative hydrogen donor in an organic solvent;
[0009] wherein one amino hydrogen in the amino acid compound is replaced by a methyl group with single selectivity to generate the N-methyl amino acid compound;
[0010] The amino acid compound is selected from at least one of an amino acid or an amino acid derivative.
[0011] The preparation equation of the N-methyl amino acid compound is as follows:
[0012]
[0013] In the method for preparing the N-methyl amino acid compound, preferably,
[0014] The amino acid or the amino acid derivative is selected from at least one of an α-amino acid compound, a β-amino acid compound, or a γ-amino acid compound;
[0015] Preferably,
[0016] The α-amino acid compound is selected from at least one of glycine, alanine, leucine, isoleucine, valine, methionine, phenylalanine, tyrosine with a protective group, serine, threonine, glutamic acid, or aspartic acid derivative; and / or,
[0017] The β-amino acid compound is selected from at least one of 3-amino-3-phenylpropionic acid and derivatives thereof; and / or,
[0018] The γ-amino acid compound is selected from at least one of phenibut, pregabalin and derivatives thereof; and / or,
[0019] The lysine compound is selected from at least one of Fmoc-L-lysine and analogues thereof.
[0020] In the method for preparing the N-methyl amino acid compound, preferably,
[0021] The negative hydrogen donor is selected from at least one of tetrahydropyrrole, 2,2,5,5-d4-tetrahydropyrrole or 2-methylpyrrolidine; and / or,
[0022] The formaldehyde is at least one of formaldehyde aqueous solution, solid formaldehyde or deuterated solid formaldehyde; preferably, the formaldehyde is selected from aqueous solution with a concentration of 36-38 wt% formaldehyde; and / or,
[0023] The organic solvent is selected from fluorine-containing organic alcohol; preferably, the organic solvent is selected from at least one of hexafluoroisopropanol and trifluoroethanol.
[0024] In the method for preparing the N-methyl amino acid compound, preferably,
[0025] The reaction temperature is 15-100°C; preferably, room temperature-60°C; and / or,
[0026] The reaction time is 2-8 hours; preferably, 4-6 hours.
[0027] In the method for preparing the N-methyl amino acid compound, preferably,
[0028] The concentration of the amino acid compound in the organic solvent is 0.01-1 mol / L; preferably, 0.2-0.6 mol / L; and / or,
[0029] The molar ratio of the negative hydrogen donor to the amino acid compound is 3-9:1; preferably, 3-4:1; and / or,
[0030] The molar ratio of the formaldehyde to the amino acid compound is 2-4:1; preferably, 2-3:1.
[0031] In the method for preparing the N-methyl amino acid compound, preferably,
[0032] After the reaction is completed, the product is purified by:
[0033] After the reaction is completed, the solvent is recovered and the concentrated crude product is stored at 0-4°C for 30 minutes to 1 hour. Cold diethyl ether is added to the crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated and then centrifuged to collect the solid and supernatant. The supernatant is again dried and stored at 0-4°C for 30 minutes to 1 hour. Cold diethyl ether is added to the crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated and then centrifuged to collect the solid.
[0034] Further preferably, the post-treatment purification of the N-methyl-α-amino acid is as follows: after the reaction is completed, the solvent is recovered and the concentrated crude product is stored at 0-4°C for 30 minutes to 1 hour. Cold diethyl ether is added to the crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated and then centrifuged to collect the solid and supernatant. The supernatant is again dried and stored at 0-4°C for 30 minutes to 1 hour. Cold diethyl ether is added to the crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated and then centrifuged to collect the solid.
[0035] The N-methyl-L-lysine is purified by HPLC.
[0036] The second object of the present application is to provide the N-methyl amino acid compound prepared by the method of the first object of the present application.
[0037] In the N-methyl amino acid compound of the present application, the N-methyl amino acid compound is N-methyl-α-L-amino acid, N-methyl-β-L-amino acid, N-methyl-γ-L-amino acid, or N-methyl-L-lysine.
[0038] Preferably, the N-methyl amino acid compound has the following general structure:
[0039]
[0040]
[0041] R1 is selected from alkyl, sulfur-substituted alkyl, aryl, hydroxyl, ester, or phenol;
[0042] R2 is selected from aryl;
[0043] R3 is selected from alkyl or aryl;
[0044] R4 is selected from acyl.
[0045] In the N-methyl amino acid compound described in the present application, preferably,
[0046] The N-methyl-alpha-L-amino acid is selected from the following compounds:
[0047]
[0048] The N-methyl-beta-amino acid is selected from the following compounds:
[0049]
[0050] In the N-methyl amino acid compound described in the present application, preferably,
[0051] The N-methyl-gamma-amino acid is selected from the following compounds:
[0052] And / or,
[0053] The N-methyl-L-lysine is selected from the following compounds:
[0054]
[0055] The present application uses formaldehyde as a methylation modification reagent, which forms an imine intermediate with the amino group of the amino acid as a negative hydrogen acceptor, and adds tetrahydro-pyrrole as a negative hydrogen donor, and hexafluoroisopropanol solvent as a proton shuttle to transfer negative hydrogen and proton. Under mild conditions, the intermolecular negative hydrogen and proton are transferred cooperatively, and the N-methyl amino acid compound with single selectivity can be efficiently synthesized. The sample required by the present application is simple, the amount is small, the reaction system is clean, the solvent can be recycled, and after the reaction, only simple purification treatment is needed, without column chromatography separation and purification, which can be applied to the methylation modification of amino acids without active side chain amino acids. The formaldehyde / tetrahydro-pyrrole / hexafluoroisopropanol reaction system in the present application provides a convenient and effective post-modification method for introducing methyl groups with single selectivity into the amino groups of different alpha, beta, and gamma-amino acids, and has potential synthetic applications.
[0056] Compared with the prior art, the present application has at least the following beneficial effects:
[0057] 1. Formaldehyde and tetrahydro-pyrrole are simple and readily available raw materials, which can be purchased commercially;
[0058] 2. The present application has mild conditions, fast reaction speed, high efficiency, excellent selectivity, and can obtain N-methylated amino acid compounds in one step;
[0059] 3. The reaction of the present application uses green and recyclable solvent;
[0060] 4、the reaction of the present application only needs simple purification treatment, without column chromatography separation and purification;
[0061] 5、the reaction of the present application is suitable for different types of different composition and length of amino acid compounds.
[0062] 6、the reaction of the present application is suitable for kilogram preparation.
[0063] In summary, the present application develops a simple and easy method for synthesizing N-methyl amino acid compounds from readily available substrates, uses green and recyclable solvents, and only needs simple purification treatment, which has high application value for efficiently and selectively synthesizing the above N-methylated amino acid compounds with different composition and length. DETAILED DESCRIPTION
[0064] The present application will be further described below in combination with specific embodiments.
[0065] Formaldehyde and tetrahydropyrrole are commercially available. Hexafluoroisopropanol solvent can be recycled by rotary evaporation and reused. The post-treatment purification is carried out by precipitation and washing with cold ether. Amino acid compounds can be directly purchased or directly synthesized according to existing methods.
[0066] An N-methyl-α-amino acid compound and a preparation method thereof are shown in the following formula:
[0067]
[0068] wherein R1 is selected from alkyl, or sulfur-substituted alkyl, aryl or protected hydroxyl, ester group, phenolic group.
[0069] Examples 1-7
[0070]
[0071] Preparation of P2: a-L-alanine P1 (1 mmol, 89 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P2. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was then centrifuged, and the solid and supernatant were collected separately. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was then centrifuged again, and the solid was enriched. P2 was characterized by the following data: white solid (80% yield, 82.4 mg).
[0072] 1 H NMR (400 MHz, CD3OD) δ 3.46 (q, J = 7.1 Hz, 1H), 2.65 (s, 3H), 1.47 (d, J = 7.1 Hz, 3H). 13 CNMR (101 MHz, CD3OD) δ 174.5, 60.3, 31.9, 15.7.
[0073] HRMS (ESI) m / z Calcd for C4H 10 NO2 + [M+H] + : 104.0706, found: 104.0709.
[0074] The reaction conditions for Examples 1-7 are shown in Table 1.
[0075] Table 1
[0076]
[0077] Example 8
[0078]
[0079] Preparation of P3: a-L-leucine (1 mmol, 131 mg) was added to a 50 mL reaction flask, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P3. After the reaction was completed, the reaction was concentrated on a rotary evaporator with the water bath temperature set at 60 °C, and more co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed as much as possible under continuous suction, and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, and the solid was allowed to slowly precipitate after standing for 10 minutes, and the solid and supernatant were collected by centrifugation. The supernatant was further dried and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, and the solid was allowed to slowly precipitate after standing for 10 minutes, and the solid was enriched by centrifugation. The detection data of P3 are as follows: white solid (84% yield, 121.8 mg).
[0080] 1 H NMR (400 MHz, D20) δ 3.56 (t, J = 6.3 Hz, 1H), 2.68 (s, 3H), 1.75-1.63 (m, 3H), 0.94 (d, J = 3.8 Hz, 6H). 13 C NMR (101 MHz, D20) δ 174.3, 62.7, 39.0, 31.8, 24.3, 21.9, 21.3.
[0081] HRMS (ESI) m / z Calcd for C7H 16 NO2[M+H + ]: 146.1176; found: 146.1177.
[0082] Example 9
[0083]
[0084] Preparation of P4: a-L-methionine (1 mmol, 149 mg) was added to a 50 mL reaction flask, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P4. After the reaction was completed, the reaction was concentrated on a rotary evaporator with the water bath temperature set at 60 °C, and more co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed as much as possible under continuous nitrogen purge and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was centrifuged to collect the solid and supernatant separately. The supernatant was further concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was centrifuged again to enrich the solid. The detection data of P4 are as follows: white solid (94% yield, 153.2 mg).
[0085] 1 H NMR (400 MHz, D20) δ 3.66 (t, J = 6.0 Hz, 1H), 2.69 (s, 3H), 2.62-2.55 (m, 2H), 2.17-2.11 (m, 2H), 2.10 (s, 3H). 13 C NMR (101 MHz, D20) δ 173.2, 62.7, 31.9, 28.8, 28.6, 14.0.
[0086] HRMS (ESI) m / z Calcd for C6H 14 NO2S[M+H + ]: 164.0740; found: 164.0736.
[0087] Example 10
[0088]
[0089] Preparation of P5: a-L-phenylalanine (1 mmol, 165 mg) was added to a 50 mL reaction flask, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at 60 °C for 4 h to give compound P5. After the reaction was completed, the reaction was concentrated on a rotary evaporator with the water bath temperature maintained at 60 °C, and more co-crystal of hexafluoroisopropanol / tetrahydro pyrrole was removed as much as possible under continuous nitrogen purge and the solvent was recovered. Subsequently, the concentrated crude product was kept at 0-4 °C for 30 min, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 min, and the solid was allowed to slowly precipitate, which was centrifuged to collect the solid and the supernatant separately. The supernatant was further concentrated and kept at 0-4 °C for 30 min, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 min, and the solid was allowed to slowly precipitate, which was centrifuged again to enrich the solid. The detection data of P5 are as follows: white solid (87% yield, 155.7 mg).
[0090] Preparation of P5 on a gram scale: a-L-phenylalanine (10 mmol, 1.65 g) was added to a 100 mL reaction flask, followed by hexafluoroisopropanol (20 mL), tetrahydro pyrrole (3 eq, 30 mmol, 2.13 g), formaldehyde 37% in water (20 mmol, 1.56 mL), and the reaction was allowed to proceed at 60 °C for 4 h to give compound P5. After the reaction was completed, the reaction was concentrated on a rotary evaporator with the water bath temperature maintained at 60 °C, and more co-crystal of hexafluoroisopropanol / tetrahydro pyrrole was removed as much as possible under continuous nitrogen purge and the solvent was recovered. Subsequently, the concentrated crude product was kept at 0-4 °C for 30 min, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 min, and the solid was allowed to slowly precipitate, which was centrifuged to collect the solid and the supernatant separately. The supernatant was further concentrated and kept at 0-4 °C for 30 min, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 min, and the solid was allowed to slowly precipitate, which was centrifuged again to enrich the solid. The detection data of P5 are as follows: white solid (75% yield, 1.35 g). 1 H NMR (400 MHz, D20) δ 7.34 - 7.33 (m, 3H), 7.30 (d, J = 6.6 Hz, 2H), 3.85 (t, J = 6.2 Hz, 1H), 3.22 (d, J = 6.2 Hz, 2H), 2.68 (s, 3H). 13 C NMR (101 MHz, D20) δ 172.8, 134.5, 129.3, 129.0, 127.7, 64.6, 35.6, 32.0.
[0091] HRMS (ESI) m / z Calcd for C 10 H 14NO2[M+H + ]:180.1019; found:180.1020.
[0092] Example 11
[0093]
[0094] Preparation of P6: α-L-phenylalanine (0.1 mmol, 16.5 mg) was added to a 50 mL reaction flask, followed by hexafluoroisopropanol (0.5 mL), 2,2,5,5-d4-tetrahydropyrrole (0.3 equivalent, 0.3 mmol, 21.3 mg), and a 37% aqueous solution of formaldehyde (0.2 mmol, 15.6 μL). The reaction was carried out at 60 °C for 4 hours to obtain compound P1. After the reaction was complete, the product was concentrated using a rotary evaporator while maintaining the water bath temperature at 60 °C. Under continuous vacuum, as much of the hexafluoroisopropanol / tetrahydropyrrole eutectic compound as possible was removed, and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0–4 °C for 30 minutes. Cold diethyl ether was added to the crude product, and after standing for 10 minutes, the solid slowly precipitated. The solid and supernatant were collected separately by centrifugation. After the supernatant was evaporated to dryness, it was stored at 0–4°C for 30 minutes. Cold diethyl ether was then added to the crude product, and the mixture was allowed to stand for 10 minutes to allow the solid to precipitate slowly. The product was then centrifuged again to enrich the solid. The detection data for P6 are as follows: white solid (72% yield, 13.0 mg, 98% D).
[0095] 1 H NMR (400MHz, D2O) δ7.45-7.36(m,3H),7.31(d,J=7.3Hz,2H),3.86(t,J=6.3Hz,1H),3.23(d,J=6.3Hz,2H),2.67(s,2H).
[0096] HRMS(ESI)m / z Calcd for C 10 H 13 DNO2[M+H + ]:181.1082; found:181.1082.
[0097] Example 12
[0098]
[0099] Preparation of P7: O-tert-butyl-L-serine (1 mmol, 164 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P7. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was then centrifuged, and the solid and supernatant were collected separately. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was then centrifuged again, and the solid was enriched. P7 was obtained as a white solid (85% yield, 148.8 mg).
[0100] 1 H NMR (400 MHz, D20) δ 3.86 (dd, J = 10.8, 3.6 Hz, 1H), 3.79 (dd, J = 10.8, 5.1 Hz, 1H), 3.72 - 3.67 (m, 1H), 2.73 (s, 3H), 1.20 (s, 9H). 13 C NMR (101 MHz, D20) δ 171.7, 74.7, 63.3, 58.7, 31.4, 26.3.
[0101] HRMS (ESI) m / z Calcd for C8H 18 NO3[M+H + ]: 176.1281 ; found: 176.1280.
[0102] Example 13
[0103]
[0104] Preparation of P8: L-glutamic acid-5-tert-butyl ester (1 mmol, 203 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P8. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was centrifuged, and the solid and supernatant were collected separately. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was again centrifuged, and the solid was enriched. P8 was obtained as a white solid (75% yield, 163.5 mg). 1 H NMR (400 MHz, CD3OD) δ 3.45 (dd, J = 7.0, 5.1 Hz, 1H), 2.68 (s, 3H), 2.45 (t, J = 7.7 Hz, 2H), 2.16 - 2.08 (m, 1H), 2.06 - 1.98 (m, 1H), 1.45 (s, 9H). 13 C NMR (101 MHz, CD3OD) δ 173.7, 172.7, 82.1, 64.3, 32.6, 32.0, 28.3, 26.2.
[0105] HRMS (ESI) m / z Calcd for C 10 H 20 NO4[M+H + ]: 218.1387; found: 218.1388.
[0106] Example 14
[0107]
[0108] Preparation of P9: L-Glutamic acid-5-tert-butyl ester (1 mmol, 237 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P9. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was centrifuged to collect the solid and supernatant separately. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand for 10 minutes, and the solid was allowed to slowly precipitate, which was again centrifuged to enrich the solid. P9 was obtained as a white solid (77% yield, 193.3 mg).
[0109] 1 H NMR (400 MHz, CD3COOD) δ 7.20 (d, J = 8.4 Hz, 2H), 6.95 (d, J = 8.5 Hz, 2H), 4.24 (t, J = 6.1 Hz, 1H), 3.31-3.19 (m, 2H), 2.78 (s, 3H), 1.34 (s, 9H). 13 C NMR (101 MHz, CD3COOD) δ 173.6, 155.7, 131.3, 130.3, 125.5, 79.8, 65.5, 36.2, 33.5, 29.1.
[0110] HRMS (ESI) m / z Calcd for C 14 H 22 NO3[M+H + ]: 252.1594; found: 252.1606.
[0111] An N-methyl-β-amino acid compound and a method for preparing the same are shown by the following formula:
[0112]
[0113] wherein R2 is selected from aryl.
[0114] Example 15
[0115]
[0116] Preparation of P10: 3-amino-3-phenylpropionic acid (1 mmol, 165 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P10. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 2 hours to allow the solid to slowly precipitate. The solid and supernatant were collected by centrifugation. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 2 hours to allow the solid to slowly precipitate. The solid was again collected by centrifugation to yield P10. The analytical data for P10 is as follows: white solid (74% yield, 132.5 mg).
[0117] 1 H NMR (400 MHz, CD3OD) δ 7.51 - 7.43 (m, 5H), 4.43 (dd, J = 9.2, 4.9 Hz, 1H), 2.90 (dd, J = 16.8, 9.3 Hz, 1H), 2.74 (dd, J = 16.9, 4.9 Hz, 1H), 2.55 (s, 3H). 13 C NMR (101 MHz, CD3OD) δ 176.6, 135.9, 130.7, 130.5, 129.2, 62.6, 40.0, 31.2.
[0118] HRMS (ESI) m / z Calcd for C 10 H 14 NO2[M+H + ]: 180.1019; found: 180.1020.
[0119] An N-methyl-gamma-amino acid compound and a method of making the same are shown by the following formula:
[0120]
[0121] wherein R3 is selected from an alkyl or aryl group.
[0122] Example 16
[0123]
[0124] Preparation of Pll: Phenibut (1 mmol, 179 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound Pll. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 12 hours to allow the solid to slowly precipitate. The solid and supernatant were collected by centrifugation. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 12 hours to allow the solid to slowly precipitate. The solid was again collected by centrifugation to yield Pll. Pll was characterized by the following data: white solid (82% yield, 158.3 mg).
[0125] 1 H NMR (400 MHz, CD3OD) δ 7.39 - 7.32 (m, 2H), 7.31 - 7.24 (m, 3H), 3.34 (d, J = 8.6 Hz, 2H), 3.23 - 3.16 (m, 1H), 2.75 - 2.69 (m, 1H), 2.66 (s, 3H), 2.60 - 2.54 (m, 1H). 13 C NMR (101 MHz, CD3OD) δ 179.7, 143.3, 130.2, 128.4, 128.3, 56.2, 45.3, 41.4, 33.8.
[0126] HRMS (ESI) m / z Calcd for C 11 H 16 NO2[M+H + ]: 194.1176; found: 194.1178.
[0127] Example 17
[0128]
[0129] Preparation of P12: Pregabalin (1 mmol, 159 mg) was added to a 50 mL reaction vial, followed by hexafluoroisopropanol (5 mL), tetrahydro pyrrole (3 eq, 3 mmol, 213 mg), formaldehyde 37% in water (2 mmol, 156 μί), and the reaction was allowed to proceed at room temperature for 4 hours to yield compound P12. After the reaction was complete, the reaction was concentrated on a rotary evaporator with the water bath temperature set to 60 °C, and more of the co-crystal compound of hexafluoroisopropanol / tetrahydro pyrrole was removed under continuous suction and the solvent was recovered. Subsequently, the concentrated crude product was stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 12 hours to allow the solid to slowly precipitate. The solid and supernatant were collected by centrifugation. The supernatant was again concentrated and stored at 0-4 °C for 30 minutes, and cold diethyl ether was added to the crude product, which was allowed to stand at 0-4 °C for 12 hours to allow the solid to slowly precipitate. The solid was again collected by centrifugation to yield P12. P12 was characterized by the following data: white solid (74% yield, 124.6 mg).
[0130] 1 H NMR (400 MHz, CD3OD) δ 2.99 (dd, J = 12.6, 3.1 Hz, 1H), 2.88 (dd, J = 12.6, 8.3 Hz, 1H), 2.66 (s, 3H), 2.50 - 2.43 (m, 1H), 2.28 (dd, J = 16.1, 9.1 Hz, 1H), 2.15 - 2.04 (m, 1H), 1.76 - 1.64 (m, 1H), 1.28 - 1.14 (m, 2H), 0.93 (t, J = 6.6 Hz, 6H). 13 C NMR (101 MHz, CD3OD) δ 180.7, 56.2, 43.6, 43.4, 33.6, 32.3, 26.2, 23.2, 22.6.
[0131] HRMS (ESI) m / z Calcd for C9H 20 NO2[M+H + ]: 174.1489; found: 174.1490.
[0132] Example 18
[0133] One method of lysine ε-NH2 side chain N-methylation and its preparation is shown by the following formula:
[0134]
[0135] Preparation of P13: Fmoc-L-lysine (0.2 mmol, 73.6 mg) was added to a 10 mL reaction vial, followed by hexafluoroisopropanol (1 mL), tetrahydro pyrrole (3 eq, 0.6 mmol, 42.6 mg), formaldehyde 37% in water (0.4 mmol, 31.3 μί), and allowed to react at room temperature for 4 hours to yield compound P13. After the reaction was complete, it was concentrated on a rotary evaporator and purified by HPLC. P13 was characterized as follows: white solid (55% yield, 46.4 mg).
[0136] 1 H NMR (400 MHz, CD3COOD) δ 7.81 (d, J = 7.6 Hz, 2H), 7.76 (d, J = 7.5 Hz, 2H), 7.41 (t, J = 7.4 Hz, 2H), 7.34 (t, J = 7.4 Hz, 2H), 6.17 (s, 2H), 4.09 (t, J = 6.2 Hz, 1H), 3.39 (d, J = 6.8 Hz, 1H), 3.16 (t, J = 7.6 Hz, 2H), 2.82 (s, 3H), 2.09 (d, J = 2.4 Hz, 2H), 1.87 - 1.78 (m, 2H), 1.69 - 1.58 (m, 2H). 13 C NMR (101 MHz, CD3COOD) δ 144.6, 141.1, 139.0, 129.7, 128.0, 121.9, 120.6, 108.3, 55.3, 49.9, 46.7, 33.8, 30.6, 26.0, 24.8, 22.5.
[0137] HRMS (ESI) m / z Calcd for C 22 H 27 N2O4[M+H + ]: 383.1965; found: 383.1964.
[0138] Example 19
[0139]
[0140] Preparation of P14: Fmoc-L-lysine (0.2 mmol, 73.6 mg) was added to a 10 mL reaction vial, followed by hexafluoroisopropanol (1 mL), tetrahydro pyrrole (3 eq, 0.6 mmol, 42.6 mg), deuterated solid formaldehyde (0.4 mmol, 12.4 mg), and allowed to react at room temperature for 4 hours to yield compound P13. After the reaction was complete, it was concentrated on a rotary evaporator and purified by HPLC. P14 was characterized as follows: white solid (51% yield, 43.4 mg).
[0141] 1 H NMR (400 MHz, CD3COOD) δ 7.81 (d, J = 7.6 Hz, 2H), 7.70-7.61 (m, 2H), 7.41 (t, J = 7.5 Hz, 2H), 7.33 (t, J = 7.4 Hz, 2H), 4.63-4.36 (m, 3H), 4.26 (t, J = 6.9 Hz, 1H), 3.10 (t, J = 7.9 Hz, 2H), 2.75 (s, 1H), 2.01-1.87 (s, 1H), 1.84-1.67 (m, 3H), 1.52 (t, J = 7.8 Hz, 1H), 1.45-1.28 (m, 1H).
[0142] HRMS (ESI) m / z Calcd for C 22 H 25 D2N2O4[M+H + ]: 385.2091; found: 385.2088.
[0143] The above examples are merely illustrative of the principles of the application, and are not intended to limit the application. Any person skilled in the art can make modifications or changes to the above examples without departing from the spirit and scope of the application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought disclosed in the present application should be covered by the claims of the present application.
Claims
1. A process for the preparation of N-methyl amino acid-based compounds, characterized by, The method comprises the following steps: reacting an amino acid compound, formaldehyde and a negative hydrogen donor in an organic solvent; wherein one amino hydrogen in the amino acid compound is selectively replaced by a methyl group to form the N-methyl amino acid compound; the amino acid compound is selected from at least one of an amino acid or an amino acid derivative; the amino acid or the amino acid derivative is selected from at least one of an α-amino acid compound, a β-amino acid compound, a γ-amino acid compound or a lysine compound; wherein the α-amino acid compound is selected from at least one of glycine, alanine, leucine, isoleucine, valine, methionine, phenylalanine, tyrosine with a protective group, serine, threonine or glutamic acid; the β-amino acid compound is selected from 3-amino-3-phenylpropionic acid; the γ-amino acid compound is selected from at least one of phenibut and pregabalin; the lysine compound is selected from at least one of Fmoc-L-lysine and 2D-Fmoc-L-lysine; the negative hydrogen donor is selected from at least one of tetrahydropyrrole, 2,2,5,5-d4-tetrahydropyrrole and 2-methylpyrrolidine; and the organic solvent is selected from a fluorine-containing organic alcohol.
2. The method according to claim 1, wherein the formaldehyde is at least one of an aqueous formaldehyde solution, solid formaldehyde and deuterated solid formaldehyde.
3. The method according to claim 2, wherein the formaldehyde is at least one of an aqueous solution with a concentration of 36-38 wt% formaldehyde; and / or the organic solvent is at least one of hexafluoroisopropanol and trifluoroethanol.
4. The method according to claim 1, wherein the reaction temperature is 15-100°C; and / or the reaction time is 2-8 hours.
5. The method according to claim 4, wherein the reaction temperature is room temperature-60°C; and / or the reaction time is 4-6 hours.
6. The method according to claim 1, wherein the concentration of the amino acid compound in the organic solvent is 0.01-1 mol / L; and / or the molar ratio of the negative hydrogen donor to the amino acid compound is 3-9:1; and / or the molar ratio of the formaldehyde to the amino acid compound is 2-4:
1.
7. The method according to claim 6, wherein the concentration of the amino acid compound in the organic solvent is 0.2-0.6 mol / L; and / or the molar ratio of the negative hydrogen donor to the amino acid compound is 3-4:1; and / or the molar ratio of the formaldehyde to the amino acid compound is 2-3:
1.
8. The method according to claim 1, wherein the purification method for the product after the reaction is completed is: after the reaction is completed, the solvent is recovered by evaporation and concentration, and the concentrated crude product is stored at 0-4°C for 30 minutes to 1 hour. The cold diethyl ether is added to the above-mentioned crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated, and then centrifuged to collect the solid and supernatant, respectively; the supernatant is spin-dried and then stored at 0-4°C for 30 minutes to 1 hour, The cold diethyl ether is added to the above-mentioned crude product, and after standing for 10 minutes to 24 hours, the solid is slowly precipitated, and then centrifuged to collect the solid and supernatant, respectively; the supernatant is spin-dried and then stored at 0-4°C for 30 minutes to 1 hour, 9. The N-methyl amino acid compound prepared according to the method of any one of claims 1-8, wherein the N-methyl amino acid compound is N-methyl-a-L-amino acid, N-methyl-L-lysine; wherein the N-methyl-a-L-amino acid is selected from the following compounds: the N-methyl-L-lysine is selected from the following compounds: