CN111072745A

CN111072745A - Preparation method of 6-methylene-7-ketocholic acid

Info

Publication number: CN111072745A
Application number: CN201911362118.8A
Authority: CN
Inventors: 欧松; 张和平; 郭然; 梁待亮
Original assignee: Zhongshan Belling Biotechnology Co ltd
Current assignee: Zhongshan Belling Biotechnology Co ltd
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2020-04-28

Abstract

The invention discloses a preparation method of 6-methylene-7-ketocholic acid, belonging to the technical field of synthetic chemical application and biological medicine. The preparation method comprises the following steps: adding alkali into the mixture of 7-ketocholic acid and formaldehyde or paraformaldehyde, reacting in a solvent, and obtaining 6-methylene-7-ketocholic acid after the reaction is finished. The method has the advantages of simple operation, high yield, low production cost and less side reaction, completely avoids complex and troublesome operations of protecting group application and protecting group removal, avoids the use of severe production conditions of anhydrous reaction, and is very convenient for scale-up production.

Description

Preparation method of 6-methylene-7-ketocholic acid

Technical Field

The invention belongs to the technical field of synthetic chemistry application and biological medicine, and particularly relates to a preparation method of 6-methylene-7-ketocholic acid.

Background

Obeticholic acid (6- α -ethyl chenodeoxycholic acid) is a farnesol receptor agonist, can indirectly inhibit expression of cytochrome genes, so that synthesis of cholic acid is inhibited, bile secretion is promoted, and portal hypertension is reduced.

6-methylene-7-ketocholic acid is a cholic acid drug intermediate with great development potential, can be used as a substrate to perform various organic synthesis reactions, conveniently introduces various complex groups on and outside a steroid ring of cholic acid by means of common methods in organic synthesis such as Heck reaction, Michael addition reaction, Henry reaction, B-H reaction and the like, so as to prepare various cholic acid active drugs, and particularly can conveniently prepare obeticholic acid and analogues thereof from him.

The Chinese patent application 201910657027.0 discloses a method for synthesizing obeticholic acid by using 6-methylene-7-ketocholic acid, which takes 1, 4-nucleophilic addition of a sulfur nucleophilic reagent to 6-ethylene-7-ketocholic acid and a subsequent Raney Ni reduction reaction as core steps to realize safe and reliable reduction, can reduce ethylene chenodeoxycholic acid into ethyl chenodeoxycholic acid (intermediate 2A) in a high selectivity under mild conditions, and obtains obeticholic acid through conventional configuration transformation and chemical reduction, thereby avoiding using dangerous catalytic hydrogenation conditions.

Another possible method is the Mukiyama-aldol reaction, the activation of the 7-keto group with a silyl enol ether being followed by reaction with formaldehyde. Although the method is feasible, a complex and harsh chemical reaction is needed to introduce a protecting group, the reaction result is extremely sensitive to the process condition, a large amount of fluorine-containing and boron-containing waste liquid which is difficult to treat is used in the production, and the method is extremely unfavorable for large-scale production.

In view of the above, the invention provides a simple, convenient and effective novel method for synthesizing 6-methylene-7-ketocholic acid from 7-ketocholic acid, which adopts cheap and easily available raw materials with relatively small toxicity hazard to prepare 6-methylene-7-ketocholic acid through reaction under mild conditions, and has the advantages of simple and convenient operation method, high yield, low production cost and few side reactions. Completely avoids complex and troublesome operations of protecting group application and protecting group removal, also avoids the use of severe production conditions of anhydrous reaction, and is very convenient for large-scale production.

Disclosure of Invention

In order to solve the technical problems, the invention provides a preparation method of 6-methylene-7-ketocholic acid, which is characterized in that a mixture of 7-ketocholic acid and formaldehyde or paraformaldehyde is treated by strong and electrodeless alkali in a polar aprotic solvent to directly obtain the 6-methylene-7-ketocholic acid. The method does not need to protect any functional group, does not need special reaction conditions, is simple and convenient to operate, has the advantages of simple and easily obtained raw materials and low cost, and is very easy for large-scale production.

In order to achieve the above purpose, the invention provides the following technical scheme:

a preparation method of 6-methylene-7-ketocholic acid comprises the following steps:

adding alkali into the mixture of 7-ketocholic acid and formaldehyde or paraformaldehyde, reacting in solvent to obtain 6-methylene-7-ketocholic acid,

the alkali is a strong inorganic alkali, preferably one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium oxide and potassium oxide, and more preferably one or more of potassium hydroxide and cesium hydroxide.

The molar ratio of the alkali to the 7-ketocholic acid is 2-15: 1, preferably 2.5 to 5: 1.

the lower the water content of the base, the better, it is preferably an inorganic base without crystal water to avoid side reactions such as disproportionation.

The formaldehyde or paraformaldehyde is preferably paraformaldehyde.

The form of the formaldehyde is selected from one or more of formaldehyde gas, aqueous solution of formaldehyde with 30-50% of formaldehyde content, methanol solution of formaldehyde with 30-50% of formaldehyde content and ethanol solution of formaldehyde with 30-50% of formaldehyde content.

The amount of the substance of formaldehyde or paraformaldehyde is 1 to 20 times, preferably 3 to 20 times that of 7-ketocholic acid, because the reaction is facilitated by the large amount of formaldehyde in view of side reactions such as volatilization and evolution of formaldehyde, disproportionation and oxidation, and the acceleration of the reaction rate.

The solvent is a polar aprotic solvent, and the polar aprotic solvent is preferably one or more of dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, hexamethylphosphoramide, acetonitrile, benzonitrile, N-dimethylacetamide, 1, 3-dimethyl-2-imidazolidinone and acetone; further preferred are dimethylformamide and dimethylsulfoxide.

The reaction temperature is 0-150 ℃, the optimal reaction temperature is slightly different according to different alkali types, and the invention proves that the optimal reaction effect can be achieved when the alkali is potassium hydroxide or cesium hydroxide and the reaction temperature is 20-70 ℃ or more preferably 40-45 ℃.

The reaction process can be followed by High Performance Liquid Chromatography (HPLC) or Thin Layer Chromatography (TLC), and the reaction can be terminated when the consumption of 7-ketocholic acid as a raw material is detected to be complete.

After the reaction is finished, the method also comprises the following steps: dissolving the reaction system in water, adjusting the pH value of the system to be acidic, separating out the target product in a solid form, filtering and drying to obtain the 6-methylene-7-ketocholic acid.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation method has high yield and less side reaction;

(2) the method adopts the raw materials which are cheap and easy to obtain and have relatively small toxicity hazard to prepare the 6-methylene-7-ketocholic acid by reaction under mild conditions, has low production cost and simple and convenient operation method, and is convenient for large-scale production.

Detailed Description

The present invention will be further explained with reference to specific embodiments in order to make the technical means, the original characteristics, the achieved objects and the effects of the present invention easy to understand, but the following embodiments are only preferred embodiments of the present invention, and not all embodiments are possible. Based on the embodiments in the implementation, other embodiments obtained by those skilled in the art without any creative efforts belong to the protection scope of the present invention.

In the following examples, the methods used are all conventional methods unless otherwise specified.

Example 1

Adding 1mol of 7-ketocholic acid into a 5L three-necked bottle, adding 3.5L of dimethyl sulfoxide solvent and 2.5mol of paraformaldehyde solvent, starting mechanical stirring, stirring vigorously to dissolve all materials, adding 3mol of anhydrous potassium hydroxide while stirring, and stirring vigorously. Gradually dissolving potassium hydroxide, slowly starting the reaction, keeping the temperature at 40 ℃ after the temperature is stable, performing HPLC tracking, and stopping the reaction until the content of 7-ketocholic acid is lower than 2%. Cooling the reaction system to room temperature, adding the reaction system into 20 liters of cold water, then adding phosphoric acid, adjusting the pH value of the system to be acidic, separating out white solid, stirring, pulverizing, filtering, washing with 5L of purified water, and drying to obtain 6-methylene-7-ketocholic acid with the yield of about 95%.

Example 2

In example 1 except that the reaction solvent was dimethylformamide in the same volume, the rest were the same, 6-methylene-7-ketocholic acid was obtained in a yield of about 90%.

Example 3

In contrast to example 2, 5mol of anhydrous cesium hydroxide was used in place of potassium hydroxide, and the rest was the same, to obtain 6-methylene-7-ketocholic acid in a yield of about 98%.

Example 4

Unlike example 1, 200ml of 37% aqueous formaldehyde was used instead of paraformaldehyde, and the reaction was followed by TLC, which was the same as above, to obtain 6-methylene-7-ketocholic acid in a yield of about 80%.

Example 5

Unlike example 1, 200ml of 50% formaldehyde in methanol was used instead of paraformaldehyde, which was the same, to give 6-methylene-7-ketocholic acid in about 56% yield.

Example 6

Unlike example 1, 200ml of 30% formaldehyde in ethanol was used instead of paraformaldehyde, which was the same, to give 6-methylene-7-ketocholic acid in about 60% yield.

Example 7

In contrast to example 1, 5mol of formaldehyde gas was introduced in place of paraformaldehyde, and the same operation was repeated, whereby 6-methylene-7-ketocholic acid was obtained with a yield of about 85%.

Example 8

Different from example 3, paraformaldehyde was used in an amount of 3mol, and the same procedure was repeated to obtain 6-methylene-7-ketocholic acid with a yield of about 98.5%.

Example 9

Unlike example 3, paraformaldehyde was used in an amount of 1mol, and the same procedure was repeated except that 6-methylene-7-ketocholic acid was obtained in a yield of about 95%.

Example 10

In a difference from example 1, 2.5mol of sodium hydroxide was used instead of potassium hydroxide, and the reaction solvent was N-methylpyrrolidone having the same volume, and the remainder was the same, to obtain 6-methylene-7-ketocholic acid in a yield of about 90%.

Example 11

In a departure from example 1, potassium hydroxide was replaced with 15mol of sodium hydroxide and the reaction solvent was the same volume of N-methylpyrrolidone, the remainder being the same, to give 6-methylene-7-ketocholic acid in a yield of about 85%.

Example 12

The difference from example 1 is that the reaction was carried out at 70 ℃ after the temperature was stabilized, and the reaction was carried out in the same manner as in example 1, whereby 6-methylene-7-ketocholic acid was obtained with a yield of about 90%.

Example 13

Unlike example 1, the same amount of sodium oxide was used instead of potassium hydroxide, and the reaction was maintained at 20 ℃ after the temperature was stabilized, and the rest was the same, to obtain 6-methylene-7-ketocholic acid with a yield of about 90%.

Example 14

Unlike example 1, potassium hydroxide was replaced with potassium oxide in the same amount, and the reaction was maintained at 70 ℃ after the temperature was stabilized, and the rest was the same, to obtain 6-methylene-7-ketocholic acid in a yield of about 93%.

Comparative example 1

In contrast to example 3, paraformaldehyde was used in an amount of 0.5mol, which was the same as above, to obtain 6-methylene-7-ketocholic acid in a yield of about 20%.

Comparative example 2

Different from example 3, the amount of the base used was 16mol, and the rest was the same, 6-methylene-7-ketocholic acid was obtained with a yield of about 82%.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A preparation method of 6-methylene-7-ketocholic acid is characterized by comprising the following steps:

2. the process according to claim 1, wherein the base is a strong inorganic base.

3. The process of claim 2, wherein the strong inorganic base is one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium oxide, potassium oxide.

4. The method of claim 1, wherein the molar ratio of base to 7-ketocholic acid is from 2 to 15: 1.

5. the method according to claim 1, wherein the formaldehyde is in a form selected from one or more of a formaldehyde gas, an aqueous solution of formaldehyde containing 30 to 50% of formaldehyde, a methanol solution of formaldehyde containing 30 to 50% of formaldehyde, and an ethanol solution of formaldehyde containing 30 to 50% of formaldehyde.

6. The method according to claim 1, wherein the amount of the substance of formaldehyde or paraformaldehyde is 1 to 20 times that of 7-ketocholic acid.

7. The method of claim 1, wherein the solvent is a polar aprotic solvent.

8. The method according to claim 7, wherein the polar aprotic solvent is one or more selected from the group consisting of dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethylphosphoramide, acetonitrile, benzonitrile, N-dimethylacetamide, 1, 3-dimethyl-2-imidazolidinone, and acetone.

9. The method of claim 1, wherein the reaction temperature is from 0 ℃ to 150 ℃.

10. The method according to claim 1, further comprising the steps of, after the reaction is completed: dissolving the reaction system in water, adjusting the pH value of the system to be acidic, separating out the target product in a solid form, filtering and drying to obtain the 6-methylene-7-ketocholic acid.