Method for preparing AST-3424 with high optical purity

Abstract

According to the method for preparing the high-optical-purity AST-3424, an intermediate A2 reacts with 3-hydroxyl-N, N-dimethyl benzamide and cesium carbonate in a protonic solvent: # imgabs0 #, and the protonic solvent is an alcohol solvent capable of dissolving the intermediate A2, the 3-hydroxyl-N, N-dimethyl benzamide and cesium carbonate and does not contain water.

Description

Technical Field

[0001] The invention relates to a preparation and purification process of AST-3424, and belongs to the field of organic chemical industry. Background Art

[0002] AST-3424 is an AKR1C3 enzyme-activated DNA alkylating agent prodrug that has entered Phase II clinical trials in both China and the United States (China's registered clinical trials are CTR20201915, CTR20201908, CTR20191399, and CTR20191371, and the United States' registered clinical trials are NCT04315324 and NCT03592264). It is specifically activated by the AKR1C3 enzyme that is highly expressed in various tumors to release DNA alkylating agents and thus exert anti-tumor effects.

[0003] This type of compound was first disclosed in patent applications WO2016145092 and WO2017087428, in which the following two synthetic routes of TH2870 (racemic form of AST-3424) were disclosed:

[0004]

[0005] The following preparation process is also disclosed in patent application WO2020172506:

[0006]

[0007] In the last step of the above AST-3424 synthesis method, acetone, DMF and other solvents are used to carry out the reaction under alkaline substances (NaH or cesium carbonate). Summary of the invention

[0008] The applicant found in the process improvement research that using aprotic solvents such as acetone, acetonitrile, tetrahydrofuran, DMF as reaction solvents and cesium carbonate as base for the reaction will cause partial racemization of the AST-3424 product, that is, the ee% value of the AST-3424 product obtained from the S-configuration intermediate ASYM-120885 in the synthesis route 3 will decrease after the reaction, and the ee% value will decrease more with the extension of the reaction time.

[0009] To this end, the applicant used protic solvents such as tert-butyl alcohol and tri-amyl alcohol to carry out the reaction and found that the product was almost not racemized, and the ee% value remained unchanged or changed slightly. Therefore, the applicant hereby proposes a method for using a protic solvent to carry out the reaction to obtain AST-3424 with high optical purity.

[0010] The method for preparing high optical purity AST-3424 is to react the intermediate A2 with 3-hydroxy-N,N-dimethylbenzamide and cesium carbonate in a protic solvent:

[0011]

[0012] The protic solvent is an alcohol solvent that can dissolve the intermediate A2, 3-hydroxy-N,N-dimethylbenzamide and cesium carbonate and does not include water.

[0013] Protic solvents, also known as protic solvents, contain -OH, -NH and other groups that can generate hydrogen bonds with nucleophiles, thereby solvating nucleophiles. Typical solvents include methanol, ethanol, tert-butanol, tri-pentanol, formic acid, ethylenediamine, etc.

[0014] As the solvent for the above reaction, it should be able to dissolve the intermediate A2, 3-hydroxy-N,N-dimethylbenzamide, and cesium carbonate, and should try not to react with the reactants A2, 3-hydroxy-N,N-dimethylbenzamide, cesium carbonate, and the product AST-3424. Therefore, the appropriate reaction solvent should be an alcohol solvent, that is, the final appropriate solvent should meet the following conditions:

[0015] 1. Protic solvent;

[0016] 2. It can dissolve intermediate A2, 3-hydroxy-N,N-dimethylbenzamide and cesium carbonate;

[0017] 3. Try not to react with reactant A2, 3-hydroxy-N,N-dimethylbenzamide, cesium carbonate and product AST-3424.

[0018] Since water may affect the stability of reactant A2 and product AST-3424, water should not be used as a reaction solvent.

[0019] Preferably, the protic solvent includes tert-butyl alcohol and tri-amyl alcohol.

[0020] In some embodiments, the reaction temperature is 15-30°C, preferably 20-30°C.

[0021] In fact, if the optical purity of the raw material A2 used is sufficient, for example, the ee% is greater than or equal to 99%, and the reaction time is appropriate: within 20 hours, 12-20 hours is recommended, then racemization will not occur during the reaction, and the ee% of the final prepared AST-3424 will be greater than or equal to 99%. DETAILED DESCRIPTION

[0022] The present invention is described below with reference to specific examples. It will be appreciated by those skilled in the art that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

[0023] The experimental methods in the following examples are conventional methods unless otherwise specified. The compounds, raw materials, reagents, etc. used are commercially available products unless otherwise specified.

[0024]

[0025] Raw material A2 can be synthesized and prepared with reference to "Pathway 1: GMP Synthesis Method (Clinical) of Compound OBI-3424" disclosed in WO2020172506, as well as WO2016145092 and WO2017087428. After preparation and purification, the HPLC purity is 99%. The HPLC method is a conventional C18 column, acetonitrile / water mobile phase, UV238nm detector, and the HPLC purity value is calculated using the area normalization method; the ee% is 99.90%, and a chiral HPLC column (such as CHIRALPAK) is used to detect the content of the RS configuration, and the ee% value is calculated.

[0026] The AST-3424 chiral HPLC detection uses the same conditions as A2 to detect the RS configuration content and calculate the ee% value.

[0027] 1. Comparative Example - Using aprotic solvents such as acetone, ACN, THF, DMF, etc., the product is partially racemized and the ee% value is reduced

[0028] 1. Synthesis of AST-3424 - Acetone as Solvent

[0029] A2 (1.15 g, 3.65 mmol), 3-hydroxy-N,N-dimethylbenzamide (0.62 g, 3.65 mmol) and 23 ml of acetone were added to a 100 ml two-necked reaction bottle, and cesium carbonate (2.38 g, 7.3 mmol) was added in batches. The reaction was stirred at 20-30°C under nitrogen protection, and samples were taken at different reaction times for detection.

[0030] The sample was added with ice water, sodium chloride and ethyl acetate, shaken and allowed to stand for separation, the upper organic phase was taken out and dried with anhydrous sodium sulfate, and then the sample was diluted and sent for AST-3424 chiral HPLC detection: the reaction was complete in 20 hours, and the ee% was 95.90%; in 31 hours, the ee% was 92.81%

[0031] 2. Synthesis of AST-3424 - Acetone as Solvent

[0032] A2 (1.20 g, 3.80 mmol), 3-hydroxy-N,N-dimethylbenzamide (0.63 g, 3.80 mmol) and 23 ml of acetone were added to a 100 ml two-necked reaction bottle, and cesium carbonate (8.86 g, 7.6 mmol) was added in batches. The reaction was stirred at 5-10 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 20 hours, and the ee% was 98.80%.

[0033] 3. Synthesis of AST-3424 - DMF as solvent

[0034] A2 (1.18 g, 3.7 mmol), 3-hydroxy-N,N-dimethylbenzamide (0.74, 4.5 mmol) and 18 ml DMF were added to a 100 ml two-necked reaction bottle, and cesium carbonate (1.71 g, 5.2 mmol) was added in batches. The reaction was stirred at 15-20 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 16 hours, and the ee% was 95.33%.

[0035] 4. Synthesis of AST-3424 - DMF as solvent

[0036] A2 (7.03 g, 22 mmol), 3-hydroxy-N,N-dimethylbenzamide (7.79 g, 29 mmol) and 60 ml DMF were added to a 100 ml two-necked reaction bottle, and cesium carbonate (10.18 g, 0.031 mol) was added in batches. The reaction was stirred at 0 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: 16 hours, ee% was 98.91%; 28 hours, ee% was 97.68%.

[0037] 5. Synthesis of AST-3424 - Acetonitrile as Solvent

[0038] A2 (2.48 g, 7.9 mmol), 3-hydroxy-N,N-dimethylbenzamide (1.30 g, 7.9 mmol) and 40 ml acetonitrile were added to a 100 ml two-necked reaction bottle, and cesium carbonate (3.85 g, 11.8 mol) was added in batches. The reaction was stirred at 20-30 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 18 hours, and the ee% was 96.33%.

[0039] 6. Synthesis of AST-3424 - Tetrahydrofuran as solvent

[0040] A2 (3.80 g, 12.06 mmol), 3-hydroxy-N,N-dimethylbenzamide (2.19 g, 13.27 mmol) and xxml tetrahydrofuran were added to a 100 ml two-necked reaction bottle, and cesium carbonate (6.29 g, 19.30 mmol) was added in batches. The reaction was stirred at 20-30 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 20 hours, and the ee% was 96.03%.

[0041] Comprehensive comparison shows that when using aprotic solvents such as acetone, ACN, THF, DMF as reaction solvents, obvious racemization occurred and the final ee% was significantly reduced.

[0042] However, when the reaction temperature is controlled at a relatively low temperature (0°C or 5-10°C), racemization may be controlled by using DMF or acetone as the reaction solvent, but racemization will still occur; and the lower reaction temperature will prolong the reaction time on the one hand, and increase the additional cooling cost on the other.

[0043] Example 2: Using protic solvents such as tert-butyl alcohol and tri-pentyl alcohol as reaction solvents, the product is not racemized and the ee% value remains almost unchanged

[0044] 7. Synthesis of AST-3424 - tert-butyl alcohol as solvent

[0045] A2 (1.69 g, 5.4 mmol), 3-hydroxy-N,N-dimethylbenzamide (1.06 g, 6.4 mmol) and 23 ml of tert-butyl alcohol were added to a 100 ml two-necked reaction bottle, and cesium carbonate (3.15 g, 9.7 mol) was added in batches. The reaction was stirred at 20-30 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 16 hours, and the ee% was 99.63%; after 21 hours, the ee% was 99.51%.

[0046] 8. Synthesis of AST-3424 - tri-amyl alcohol as solvent

[0047] A2 (1.30 g, 4.1 mmol), 3-hydroxy-N,N-dimethylbenzamide (1.09 g, 6.6 mmol) and 23 ml of tri-amyl alcohol were added to a 100 ml two-necked reaction bottle, and cesium carbonate (2.09 g, 6.4 mmol) was added in batches. The reaction was stirred at 20-30 ° C under nitrogen protection, and samples were taken for detection at different reaction times. After the above-mentioned acetone post-treatment operation, the sample was sent for chiral HPLC detection: the reaction was complete in 16 hours, and the ee% was 99.70%; after 21 hours, the ee% was 99.61%.

[0048] When the reaction is carried out at a temperature close to room temperature using protic solvents such as tert-butyl alcohol and tri-amyl alcohol as reaction solvents, racemization hardly occurs and the final ee% value is almost maintained, obtaining AST-3424 with an ee% value of more than 99%. Moreover, even if the reaction is extended after the reaction is complete at 16 hours, the ee% value only decreases slightly, but still remains above 99%.

[0049] In addition, the reaction time of room temperature reaction is shorter than that of low temperature (0°C or 5-10°C). Therefore, using protonic solvents such as tert-butyl alcohol and tri-amyl alcohol as reaction solvents and conducting the reaction at a reaction temperature close to room temperature can not only reduce costs but also obtain higher quality AST-3424 compounds.

Claims

1. A method for preparing high optical purity AST-3424, wherein the intermediate A2 reacts with 3-hydroxy-N,N-dimethylbenzamide and cesium carbonate in a protic solvent: in, The protic solvent is an alcohol solvent that can dissolve the intermediate A2, 3-hydroxy-N,N-dimethylbenzamide, and cesium carbonate and does not include water.

2. The method according to claim 1, wherein the protic solvent comprises tert-butyl alcohol or tri-amyl alcohol.

3. The method according to claim 1, wherein the reaction temperature is 15-30°C and the reaction time is within 20 hours, preferably 12-20 hours.

4. The method according to claim 1, wherein the ee% of the prepared AST-3424 is greater than or equal to 99%.

5. The method according to claim 1, wherein the concentration of the purified product A2 in the protic solvent solution of 3-hydroxy-N,N-dimethylbenzamide is not more than 0.07 g / ml, the concentration of 3-hydroxy-N,N-dimethylbenzamide is not more than 0.04 g / ml, and the molar ratio of the purified product A2, 3-hydroxy-N,N-dimethylbenzamide and cesium carbonate is 1:1.18-1.61:1.50-1.57.

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