Crystalline form of obeticholic acid and preparation method therefor

Abstract

The present invention relates to a new crystalline form of obeticholic acid and a preparation method therefor. In particular, the present invention relates to crystal form E of obeticholic acid and a preparation method therefor. The crystalline form is very stable, and the solvent residue is low, and the crystalline form is suitable for industrial production. Obeticholic acid has the following structure: ##STR00001##

Claims

1. Crystal form E of a compound of formula (I), wherein an X-ray powder diffraction spectrum of crystal form E comprises characteristic peaks at diffraction angles 0.2 of about 3.07, 4.86, 5.21, 6.20, 7.15, 7.64, 8.18, 8.84, 9.86, 10.88, 12.31, 14.75, 15.28, 15.77, and 16.37, ##STR00004##

2. A method of preparing the crystal form E of the compound of formula (I) according to claim 1, comprising: 1) adding a crystal form or amorphous form of the compound of formula (I) into an appropriate amount of solvent to obtain a mixture, heating the mixture to obtain a solution, and then cooling the solution to precipitate a crystal, wherein the solvent is one or more selected from the group consisting of ethyl acetate, methyl acetate, propyl acetate, methyl formate, ethyl formate, and propyl formate, or the solvent is a mixed solvent of one or more selected from the group consisting of ethyl acetate, methyl acetate, propyl acetate, methyl formate, ethyl formate, and propyl formate with n-pentane, n-hexane, n-heptane or petroleum ether; and 2) filtering the crystal and drying the crystal.

3. A pharmaceutical composition, comprising the crystal form E according to claim 1, and a pharmaceutically acceptable carrier.

4. A method for purifying obeticholic acid, comprising transforming crude obeticholic acid to the crystal form E according to claim 1.

5. The method according to claim 4, wherein the transforming crude obeticholic acid to the crystal form E comprises recrystallizing the crude obeticholic acid with a solvent, wherein the solvent is one or more selected from the group consisting of ethyl acetate, methyl acetate, propyl acetate, methyl formate, ethyl formate, and propyl formate, or the solvent is a mixed solvent of one or more selected from the group consisting of ethyl acetate, methyl acetate, propyl acetate, methyl formate, ethyl formate, and propyl formate with n-pentane, n-hexane, n-heptane or petroleum ether.

6. The method according to claim 4, further comprising separating the crystal form E.

7. The method according to claim 6, further comprising transforming the crystal form E to an amorphous form or other crystal form.

8. The method according to claim 7, wherein the transforming the crystal form E to an amorphous form comprises dissolving the crystal form E in a base to obtain a solution, and precipitating the solution with an acid.

9. The method according to claim 8, wherein the base is an inorganic base.

10. The method according to claim 8, wherein the acid is an inorganic acid.

11. Crystal form E of a compound of formula (I): ##STR00005## wherein the crystal form E has a characteristic X-ray powder diffraction spectrum as shown in FIG. 1.

12. The crystal form E according to claim 1, wherein a characteristic differential scanning calorimetry (DSC) spectrum comprises an endothermic peak at 94.5° C.

13. The method according to claim 2, wherein the mixed solvent is n-hexane/ethyl acetate.

14. A method of treating primary biliary cirrhosis or nonalcoholic fatty liver disease, comprising administering to a subject the pharmaceutical composition according to claim 3.

15. The method according to claim 5, wherein the mixed solvent is n-hexane/ethyl acetate.

16. The method according to claim 9, wherein the crystal form E is separated by filtration.

17. The method according to claim 10, wherein the base is an aqueous NaOH solution.

18. The method according to claim 10, wherein the acid is hydrochloric acid.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the X-ray powder diffraction spectrum of crystal form E of the compound of formula (I).

(2) FIG. 2 shows the DSC spectrum of crystal form E of the compound of formula (I).

DETAILED DESCRIPTION OF THE INVENTION

(3) The present invention will be illustrated by the following examples in detail. The examples of the present invention are merely intended to describe the technical solution of the present invention, and should not be considered as limiting the scope of the present invention.

(4) Test instruments used in the experiments

(5) 1. DSC Spectrum

(6) Instrument type: MettlerToledo DSC 1 Staree System

(7) Purging gas: Nitrogen

(8) Heating rate: 10.0° C./min

(9) Temperature range: 40-350° C.

(10) 2. X-Ray Diffraction Spectrum

(11) Instrument type: Bruker D8 Focus X-ray powder diffractometer

(12) Ray: monochromatic Cu-Kα ray (λ=1.5406)

(13) Scanning mode: θ/20, Scanning range: 2-40°

(14) Voltage: 40 KV, Electric current: 40 mA

EXAMPLE 1

(15) 1.0 g of the compound of formula (I) (crystal form C, prepared by the method disclosed in CN201380043964.8) was added to a 10 ml conical flask, followed by addition of 2 ml of n-hexane and 2 ml of ethyl acetate. The mixture was heated to 60° C. to make the solution clear, and then naturally cooled to room temperature and stirred for 20 hours. The mixture was filtered, and then blast dried at 30° C. for 2 hours to obtain a solid (0.8 g, yield: 80%). The X-ray powder diffraction spectrum of the crystal sample is shown in FIG. 1. There are characteristic peaks at about 3.07, 4.86, 5.21, 6.20, 7.15, 7.64, 8.18, 8.84, 9.86, 10.88, 12.31, 14.75, 15.28, 15.77, and 16.37. The DSC spectrum is shown in FIG. 2, having a sharp melting endothermic peak at 94.5° C. The crystal form was defined as crystal form E.

EXAMPLE 2

(16) 1.0 g of the compound of formula (I) (amorphous form) was added to a 10 ml conical flask, followed by addition of 2 ml of ethyl acetate. The mixture was heated to 65° C. to make the solution clear, and then naturally cooled to room temperature and stirred for 20 hours. The mixture was filtered, and then blast dried at 40° C. for 1 hour to obtain a solid (0.5 g, yield: 50%). The product was identified as crystal form E after studying and comparing the X-ray diffraction and DSC spectra.

EXAMPLE 3

(17) 1.0 g of the compound of formula (I) (amorphous form) was added to a 10 ml conical flask, followed by addition of 3 ml of ethyl formate. The mixture was heated to 50° C. to make the solution clear, and then naturally cooled to room temperature and stirred for 20 hours. The mixture was filtered, and then dried in a vacuum at 30° C. for 4 hours to obtain a solid (0.6 g, yield: 60%). The product was identified as crystal form E after studying and comparing the X-ray diffraction and DSC spectra.

EXAMPLE 4

(18) 1.0 g of the compound of formula (I) (amorphous form) was added to a 10 ml conical flask, followed by addition of 2 ml of ethyl acetate and 3 ml of n-heptane. The mixture was heated to 60° C. to make the solution clear, and then naturally cooled to room temperature and stirred for 20 hours. The mixture was filtered, and then dried in a vacuum at 30° C. for 4 hours to obtain a solid (0.85 g, yield: 85%). The product was identified as crystal form E after studying and comparing the X-ray diffraction and DSC spectra.

EXAMPLE 5

(19) The sample of crystal form E prepared in Example 1 was spread flat in the air to test its stability under conditions of lighting (4500 Lux), heating (40° C., 60° C.), and high humidity (RH 75%, RH 90%), respectively. Samplings were carried out on Day 5 and Day 10. The purity as detected by HPLC is shown in Table 1.

(20) TABLE-US-00001 TABLE 1 Stability comparison of the sample of crystal form E of the compound of formula (I) Batch Time number (day) Lighting 40° C. 60° C. RH 75% RH 90% Crystal 0 99.7% 99.7% 99.7% 99.7% 99.7% form E 5 99.6% 99.6% 99.4% 99.7% 99.6% 10 99.6% 99.5% 99.1% 99.7% 99.5%

(21) The results of the stability study showed that the sample of crystal form E of the compound of formula (I) had good stability when it was spread flat in the air under conditions of lighting/high humidity, while the sample was slightly degraded under a condition of high temperature.

EXAMPLE 6

(22) Crystal form E of the compound of formula (I) prepared according to the method of Example 1 was ground, heated or tableted. The results showed that the crystal form was stable. The detailed experimental data are shown in Table 2 below.

(23) TABLE-US-00002 TABLE 2 Special stability study of crystal form E of the compound of formula (I) Batch Treatment Crystal number Process Experimental procedure form DSC peak Crystal Grinding 1 g of the sample of Crystal 94.3° C. form E treatment crystal form E of the form E for 10 compound of formula minutes (I) was ground for 10 minutes in a mortar under nitrogen atmosphere. Heating 1 g of the sample of Crystal 94.5° C. treatment crystal form E of the form E for 3 hours compound of formula at 80° C. (I) was spread flat and heated at 80° C. for 3 hours. Tableting The sample of crystal Crystal 94.6° C. treatment form E of the compound form E of formula (I) was tableted.

EXAMPLE 7

(24) The stability of crystal form E of the compound of formula (I) prepared according to the method of Example 1 was tested under a placement condition (30° C., RH 65%). Samplings were carried out on Day 5, Day 10, and Day 30. The results showed that the crystal form E was stable under the placement condition. The experimental data are shown in Table 3.

(25) TABLE-US-00003 TABLE 3 Stability study of crystal form E of the compound of formula (I) Purity Crystal form determined (X-ray powder Batch number Time by HPLC diffraction) Crystal form E Day 0 99.75% Crystal form E S051407170104 Day 5 99.72% Crystal form E Day 10 99.73% Crystal form E Day 30 99.70% Crystal form E

EXAMPLE 8

(26) 80 ml of tetrahydrofuran, 8 ml of hydrochloric acid, and 15 ml of purified water were added to 5.0 g of 6α-ethyl-3α-(methoxymethoxy)-7α-hydroxy-5β-cholane-24-acid (which can be prepared according to the method disclosed in WO2016045480), and the reaction was carried out at room temperature for 12 hours. The reaction solution was concentrated under reduced pressure, 30 ml of ethyl acetate and 10 ml of purified water were added to the residue, and then two phases were separated. The organic phase was washed with water, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. Then, 10 ml of n-hexane and 5 ml of ethyl acetate were added to the residue, and the mixture was heated to 60° C. and stirred for 30 minutes, and then cooled to precipitate a crystal. The mixture was filtered to obtain 3.1 g of crude obeticholic acid (the purity is 99.29% determined by HPLC, wherein the content of impurity A is 0.42%). Then, 6 ml of n-hexane and 6 ml of ethyl acetate were added to the crude product, and the mixture was heated to 60° C. to make the solution clear, and then naturally cooled to room temperature and stirred for 20 hours. The mixture was filtered, and then blast dried at 50° C. for 2 hours to obtain 2.1 g of crystal form E solid (the purity is 99.75% determined by HPLC, wherein the content of impurity A is 0.21%).

(27) 2.1 g of crystal form E solid was dissolved in a sodium hydroxide solution (prepared by dissolving 0.6 g of sodium hydroxide in 15 ml of purified water). The resulting solution was added dropwise to a hydrochloric acid solution (prepared by dissolving 0.15 ml of hydrochloric acid in 15 ml of purified water), and the mixture was stirred for 1 hour and filtered. The filter cake was washed for 4 times and dried under reduced pressure to obtain 1.7 g of amorphous solid (the purity is 99.70% determined by HPLC, wherein the content of impurity A is 0.22%).

(28) The result showed that the recrystallization with n-hexane/ethyl acetate can effectively improve the purity of the sample. There is no significant change in purity when the crystal form E is transformed to an amorphous form.