CN104860980B - It is a kind of to be used to synthesize intermediate of Ezetimibe and its preparation method and application - Google Patents

Abstract

The invention discloses an intermediate for synthesizing ezetimibe and a preparation method thereof. The intermediate has a structure as shown in formula III, and its synthesis adopts an enzyme-chemical method. The raw material compound undergoes an asymmetric reduction reaction under the catalysis of aldehyde and ketone reductase to generate a chiral hydroxyl compound, and then undergoes a ring closure reaction to obtain a product. The intermediate is used to prepare ezetimibe, the process is simple, the obtained product has a high concentration, and has the advantages of high optical purity of the product, mild reaction conditions, environmental friendliness, simple operation, and easy industrial scale-up, and has a good industrial application prospect .

Description

A kind of intermediate for synthesizing ezetimibe and its preparation method and application

technical field

The invention belongs to the field of organic chemistry, and in particular relates to an intermediate for synthesizing ezetimibe, a preparation method and application thereof.

Background technique

Ezetimibe is a breakthrough in the research of blood lipid-lowering drugs. It was approved by the US FDA in 2002 and became the first lipid-lowering drug with a completely innovative mechanism of action since statins. The drug inhibits the absorption of cholesterol and phytosterols in food and bile at the brush border of the small intestine, reduces the transport of cholesterol from the intestine to the liver, reduces the storage of cholesterol in the liver, and increases the clearance of cholesterol in the blood, thereby reducing plasma cholesterol Level. As of 2011, ezetimibe's original single tablet and compound tablet have been approved by SFDA and launched in China. The structural formula of ezetimibe is shown below:

The synthesis of ezetimibe has been reported in the literature. According to the different starting materials, synthesis steps or intermediates, there are mainly four synthesis methods, including:

Route 1:

Patent US5767115 provides a synthetic method: use glutaric anhydride to open the ring under the action of CH ₃ OH to obtain a monomethyl ester compound, then undergo acyl chloride to obtain an acid chloride compound, and then recrystallize to obtain a compound after amidation, in DIPEA, TiCl ₄ conditions and imine ring closure, and then through hydrolysis, acid chloride, and bromine 4-fluorophenyl magnesium under the action of ZnCl ₂ , Pd(PPh ₃ ) ₄ to obtain (3S,4R)-lactam ring, and finally use ( R)-MeCBS/BH ₃ reduction, palladium carbon plus hydrogen debenzylation protection to obtain ezetimibe. The specific route is as follows:

This method uses Grignard reaction with harsh conditions to synthesize key intermediates. The yield is low, and column chromatography purification is required, and the synthetic route is relatively cumbersome, requiring the use of expensive tetrakistriphenylphosphopalladium catalyst.

Relevant literature and patent US5919672 also adopted a similar method, the difference is that after the synthesis of the acid chloride compound, it is allowed to react with the imine compound to obtain an optically active isomer mixture, and the (3R,4S)-lactam ring is obtained by chiral resolution. The route is as follows:

Although this method reduces steps, it needs to use chiral resolution to obtain intermediates with optical purity, which is obviously not suitable for industrial production.

Route two:

In the patent US5856473, 5-(4-fluorophenyl)-4-pentenoic acid was used as raw material and key intermediate to construct a compound with two chiral centers through a four-step reaction, and then an S structure was introduced at the benzylic position. The ezetimibe is obtained from the hydroxyl group of the type, and the whole synthetic route has seven steps, and the total yield is about 16%. The route is as follows:

Patent WO2010012775 also adopts a similar route, the difference is that the Wittig reagent is prepared from triphenylphosphine and ethyl 4-bromobutyrate to react with 4-fluorobenzoic acid to mainly generate (Z)-5-(4-fluorophenyl) Pent-4-enoic acid.

Patent WO9716424 also adopts a similar route, except that when synthesizing the (3R,4S)-lactam ring, it is condensed under the action of LDA/THF to obtain a mixture of enantiomers. The (3R,4S)-lactam ring was obtained by column separation, and then the ezetimibe was obtained by the same method as above. The disadvantage of this method is the need for chiral resolution, and the reaction needs to be carried out at -76°C to -78°C when preparing the (3R,4S)-lactam ring.

The raw materials of this route are expensive, the route is long, the process is complex and the operation is relatively difficult, and the chirality is difficult to control.

Route three:

The patent US6207822 mainly uses fluorobenzene and glutaric anhydride as raw materials, and performs Friedel-Crafts reaction under the action of Lewis acid to obtain compound 4, which is amidated to obtain compound 17, and compound 17 is prepared in (R)-methyl-CBS-oxazolidine In the presence of a chiral reduction reaction, the preparation of compound 18, the protected compound 18 and the protected imine compound, through the Mannich coupling reaction to generate compound 19, compound 19 and tetrabutylammonium fluoride and N, O-bistrimethyl The reaction of silaneacetamide to generate ezetimibe is as follows:

4US6207822, WO2007120824, WO2010071358, etc. have also adopted similar routes, the difference is that different ketal protection and hydroxyl reagents are introduced, and the order of chiral reduction is slightly different.

Route 4:

Patents US5886171 and WO9745406 use (4S)-hydroxytetrahydrofuran-2-one and N-(4-fluorophenyl)-4-benzyloxybenzylidene amine as starting materials, and obtain it by LDA ring closure under low temperature conditions (3R,4S)-Lactone amides. There are seven steps in the whole synthesis process, and the total yield is 20%. The synthetic route is as follows:

The disadvantage of this route is that the synthesis process involves the use of air-sensitive metal compounds Li, LDA, TiCl ₄ , etc., and the low-temperature reaction at -78°C, and the use of Pd/C under high pressure to catalyze the hydrogenation of olefinic bonds. The process is complex and the reaction conditions are harsh.

It can be seen from the existing routes for the synthesis of ezetimibe that the construction of chiral hydroxyl and lactam structures is a key step in the synthesis of ezetimibe, and these routes generally have complex processes, high costs, and poor selectivity , low industrial application prospects and other defects. In order to solve the problems existing in the existing technology and overcome the technical barriers of foreign pharmaceutical companies, it is urgent to find a synthetic route with simple process, low cost, good selectivity, easy and efficient separation, and suitable for large-scale industrial production.

Contents of the invention

The present invention aims to provide an intermediate for the synthesis of ezetimibe, which has the structure shown in formula III, that is, (S)-1-(4-fluorophenyl)-4-(4-substituted benzene base)-azetidin-2-one. The intermediate is synthesized by an enzymatic-chemical method. The raw material compound undergoes an asymmetric reduction reaction under the catalysis of aldehyde and ketone reductase to generate a chiral hydroxyl compound, and then undergoes a ring closure reaction to obtain a product. The intermediate can be prepared into ezetimibe through a two-step process, with few steps, simple process and high yield.

Specifically, the purpose of the present invention is achieved through the following aspects.

The first aspect of the present invention is to provide an intermediate for the synthesis of ezetimibe, which has a chemical structure as shown in formula III:

Wherein, R is a hydroxyl protecting group, preferably a silicon ether protecting group (such as TMS, TBDPS, TBDMS, TIPS, etc.), acetyl, benzoyl, benzyl, MOM, C ₁ -C ₄ alkyl, THP, etc.

The second aspect of the present invention provides the preparation method of the intermediate shown in the above formula III, comprising the following steps:

a) Under the catalysis of aldehyde and ketone reductase, the compound of formula V undergoes an asymmetric reduction reaction to generate the compound of formula IV;

b) The compound of formula IV undergoes a bromination reaction with a brominating reagent in an organic solvent, and then reacts with p-fluoroaniline under the action of a weak base to obtain a compound of formula III;

The reaction formula is as follows:

Wherein, R is a hydroxyl protecting group, preferably a silicon ether protecting group (such as TMS, TBDPS, TBDMS, TIPS, etc.), acetyl, benzoyl, benzyl, MOM, C ₁ -C ₄ alkyl, THP, etc.; R ' is an ester residue, such as an alkyl group, preferably a C ₁ -C ₄ alkyl group.

The reaction of step a) is carried out in an aqueous solution with a pH value of 5.0-8.0. Wherein, the preferred concentration of the compound of formula V in the reaction system is 10-1000 g/L. The amount of aldehyde and ketone reductase is a catalytically effective amount, preferably 1-20 g/L.

Preferably, the reaction system also contains isopropanol, or a combination of NADP+, glucose and glucose dehydrogenase. The amount of isopropanol is 2%-10% of the volume of the reaction system. The dosage of glucose is preferably 1-20g/L, the dosage of glucose dehydrogenase is preferably 100-1000U/L, and the dosage of NADP+ is a catalytic amount, preferably 0.02-0.1mmol/L.

The said aldehyde and ketone reductase is the aldehyde and ketone reductase disclosed in the Chinese patent application No. 201410706195.1 (abbreviated as "cited application", hereinafter the same), and the full text of this application is hereby incorporated as a supplement and reference. The amino acid sequence of the aldehyde and ketone reductase is shown in SEQ ID NO: 1 of the present application (ie, SEQ ID NO: 4 in the cited application).

It is easy to understand that when using the recombinant aldehyde and ketone reductase or the catalyst in the cited application to replace the aldehyde and ketone reductase, the intermediate of formula III can also be obtained through the above method. Here it is included in the understanding category of aldehyde and ketone reductase.

In step b), the organic solvents are those solvents that can dissolve the compound of formula IV and p-fluoroaniline but do not participate in chemical reactions, such as xylene, toluene, dichloromethane, tetrahydrofuran, etc. The bromination reaction can adopt bromination reaction conditions commonly used in the art, wherein the bromination reagent is preferably phosphorus tribromide, phosphorus pentabromide, carbon tetrabromide, etc. The weak base may be selected from ethylenediamine, diisopropylethylamine, N-methylmorpholine, p-dimethylaminopyridine, triethylamine and the like.

Preferably, the mol ratio of formula IV compound and brominating reagent is 1:1-3; the mol ratio of formula IV compound and p-fluoroaniline is 1:1-3; the mol ratio of weak base and p-fluoroaniline is 1: 2-6.

A third aspect of the present invention is to provide a method for preparing ezetimibe using the above-mentioned compound of formula III, comprising the following steps:

A) the compound of formula III reacts with the compound of formula VI under the action of alkali to generate the compound of formula II;

b) the compound of formula II removes the hydroxyl protecting group to generate ezetimibe;

The reaction formula is as follows:

Wherein, both R and R" are hydroxyl protecting groups, which can be independently selected from silicon ether protecting groups (such as TMS, TBDPS, TBDMS, TIPS, etc.), acetyl, benzoyl, benzyl, MOM, C ₁ -C ₄ Alkyl, THP, etc.

In step a), the compound represented by formula III is dissolved in an organic solvent, and reacted with the compound of formula VI under the action of a base at 60-180° C. to form the compound of formula II. The organic solvent is a solvent that can dissolve the compounds of formulas III and VI and does not participate in the reaction, such as DMSO, toluene, tetrahydrofuran, etc. The base is preferably selected from NaH, LDA, n-BuLi and the like.

In the reaction system of step a), the molar ratio of the compound of formula III to the compound of formula VI is preferably 1:1-3; the molar ratio of the compound of formula III to the base is preferably 1:1-3.

In step b), the removal of the hydroxyl protecting group of the compound of formula II is preferably carried out under acidic conditions, such as hydrolysis under Lewis acid or protic acid conditions, such as trifluoroacetic acid, hydrochloric acid, sulfuric acid and the like.

The raw materials and reagents used in the present invention are commercially available, or can be conveniently prepared by existing known synthetic methods.

The positive progress effect of the present invention is: for the deficiencies in the existing ezetimibe synthesis process (especially the defect that cannot be industrialized), the present invention provides a new intermediate for synthesizing ezetimibe and its Preparation. Utilizing the new intermediate to synthesize ezetimibe, the resulting product has high concentration, high optical purity, mild reaction conditions, environmental friendliness, simple operation, and easy industrial scale-up, so it has good industrial application prospects.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but the present invention is not limited thereto. The experimental steps without specific conditions indicated in the following examples are usually carried out according to conventional conditions or according to the conditions suggested by the manufacturer.

The aldehyde and ketone reductase lyophilized powder and the crude enzyme solution (the protein concentration of the aldehyde and ketone reductase in the crude enzyme solution is 10-15 mg/mL) used in the examples were prepared by referring to the method described in Example 3 of the specification in the cited application , the amino acid sequence of the aldehyde and ketone reductase is shown in SEQ ID NO: 1 of the present application.

TLC conditions: EA:PE=1:3, iodine jar for color development.

Determination conditions of e.e. value: use Agilent 1100 liquid chromatography equipped with Chiralpak IA column (4.6×150mm: ethyl/heptane 90:10, flow rate 1.5mL/min; column temperature 40°C) to determine the product configuration.

Determination conditions of d.e. value: Agilent 1100 liquid chromatography equipped with Chiralpak IA column (4.6×150mm: ethyl/heptane 90:10, flow rate 1.5mL/min; column temperature 40°C) was used to determine the product configuration.

Synthesis of Formula IV Compounds

Example 1

With stirring, 20 g of the substrate Add to the reaction solution containing the following components: 700mL water, 2g of aldehyde and ketone reductase lyophilized powder, 7g of glucose and 500U of glucose dehydrogenase (purchased from sigma), and 0.1mM NADP+, and stirred at 30°C for 16 hours During the period, the pH value of the system was controlled between 6.5-7.5 by using 1M NaOH aqueous solution, and the reaction progress was detected by TLC.

After the reaction, adjust the pH value to about 9.0, extract 3 times with an equal volume of ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, spin down the solvent under reduced pressure to obtain 18.5 g of the product, the yield is 91.8%, and the purity is 97.0 %.

The structure of the product was confirmed by 1H NMR, electrospray ionization mass spectrometry and e.e. value determination.

¹ H NMR (300MHz, CDCl3): δ6.66-7.02 (4H, m, Ar-H), 5.14 (1H, t, -CHOH), 3.67 (3H, s, -OCH ₃ ), 2.61-2.86 (2H ,d,-CH ₂ CO ₂ CH ₃ ),2.0(1H,s,-OH),0.08(9H,s,-Si(CH ₃ ) ₃ ).

MS (ESI) m/z: (M+H) = 269.1.

Product retention time: R-type, 5.3min, S-type, 7.2min, e.e. value>99%.

Example 2-4

Referring to the method of Example 1, using the substrates listed in Table 1, Examples 2-4 were carried out.

The results are shown in Table 1.

Table 1

Example 5

With stirring, 20 g of the substrate Add to the reaction solution containing the following components: 700mL water, 200mL crude enzyme solution and 20mL isopropanol, stir and react at 30°C for 16 hours, during which the pH value of the system is controlled between 6.5-7.5 with 1M NaOH aqueous solution, TLC detects the progress of the reaction.

After the reaction, adjust the pH value to 9.0, extract 3 times with an equal volume of ethyl acetate, combine the organic phases, dry over anhydrous sodium sulfate, spin down the solvent under reduced pressure to obtain 18.3 g of the product, the yield is 90.8%, and the purity is 96.9% .

The structure of the product was confirmed by 1H NMR, electrospray ionization mass spectrometry and e.e. value determination.

¹ H NMR (300MHz, CDCl3): δ6.66-7.02 (4H, m, Ar-H), 5.14 (1H, t, -CHOH), 3.67 (3H, s, -OCH ₃ ), 2.61-2.86 (2H ,d,-CH ₂ CO ₂ CH ₃ ),2.0(1H,s,-OH),0.08(9H,s,-Si(CH ₃ ) ₃ ).

MS (ESI) m/z: (M+H) = 269.1.

The detection of chiral purity is the same as in Example 1, e.e. value>99%.

Example 6-8

Referring to the method of Example 5, using the substrates listed in Table 2, Examples 6-8 were carried out.

The results are shown in Table 2.

Table 2

Synthesis of compounds of formula III

Example 9

Dissolve the compound of formula 4 (2.68g) in 20mL of xylene, add phosphorus tribromide (1.1mL), reflux for 5h, then wash with 20mL of saturated aqueous sodium bicarbonate solution and water successively, and dry the filtrate with anhydrous sodium sulfate. filter.

Triethylamine (2.1mL) and p-fluoroaniline (1.1g) were added to the filtrate, stirred at room temperature for 6h, then heated to 90°C for distillation under atmospheric pressure, and the reaction progress was monitored by TLC.

After the reaction, the reaction solution was washed once with water, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to remove the solvent to obtain 2.84 g of the compound of formula 3 with a yield of 86.5%.

The structure of the product was confirmed by 1H NMR, electrospray ionization mass spectrometry and e.e. value determination.

¹ H NMR (300MHz, CDCl3): δ7.02-7.08 (4H, s, Ar-H), 6.68-6.95 (4H, s, Ar-H), 4.85 (1H, t, ArCHN-), 3.24-3.49 (2H,d,-CH ₂ CO-),0.08(9H,s,-Si(CH ₃ ) ₃ ).

MS (ESI) m/z: (M+H) = 330.1.

Product retention time: R-type, 6.4min, S-type, 7.9min, e.e. value>95%.

Examples 10-12

Referring to the method of Example 9, using the substrates listed in Table 3, Examples 10-12 were carried out.

The results are shown in Table 3.

table 3

Synthesis of Example 13 Ezetimibe

Step a)

Dissolve the compound of formula 3 (6.58g) in 40mL DMSO, add the compound of formula 6 (5.72g) and LDA (3.3g), stir and heat to 120°C for reflux reaction for 48h, filter to remove solid salt after cooling, and concentrate the filtrate under reduced pressure 8.82 g of the compound of formula 2 was obtained with a yield of 79.8%.

The structure of the compound of formula 2 was confirmed by proton nuclear magnetic resonance spectrum, electrospray ionization mass spectrometry and d.e. value determination, and the characterization results are shown below.

¹ H NMR (300MHz, CDCl3): δ6.90-7.17 (4H, s, Ar-H), 7.02-7.08 (4H, s, Ar-H), 6.68-6.95 (4H, s, Ar-H), 4.84(1H,d,ArCHN-),4.50(1H,t,-CHOSiMe ₃ ),3.45(1H,d,-COCH-),1.77(2H,t,Me ₃ SiOCHCH ₂ -),1.63(2H,t ,-COCHCH ₂ -),0.08(18H,s,OSi(CH ₃ ) ₃ ).

MS (ESI) m/z: (M+H) = 554.2.

Chiral HPLC retention time of the product: R-type, 9.6min, S-type, 10.9min, d.e. value>90%. Step b)

Compound 2 (5.53 g) was dissolved in 50 mL of dichloromethane, trifluoroacetic acid (0.07 mL) was added, the reaction was stirred at room temperature for 5 h, and the reaction progress was monitored by TLC. After the reaction was complete, the solvent was concentrated under reduced pressure to remove the solvent, and recrystallized from ethanol to obtain 3.58 g of the compound of formula 1, namely ezetimibe, with a yield of 87.5%.

The structure of ezetimibe was confirmed by proton nuclear magnetic resonance, electrospray ionization mass spectrometry and d.e. value determination, and the characterization results are shown below.

¹ H NMR (300MHz, CDCl3): δ6.90-7.17 (4H, m, Ar-H), 7.02-7.08 (4H, m, Ar-H), 6.68-6.95 (4H, m, Ar-H), 5.0(1H,s,Ar-OH),4.84(1H,d,-CH-),4.50(1H,t,-CHOH),3.45(1H,dt,-CH-),1.77(2H,dt,- CH ₂ -),1.63(2H,dt,-CH ₂ -).

MS (ESI) m/z: (M+H) = 410.2.

Chiral HPLC retention time of the product: R-type, 9.6min, S-type, 10.9min, d.e. value>95%.

Claims (11)

1. the preparation method of Ezetimibe intermediate, includes the following steps shown in a kind of formula III：

A) in the case where aldehyde ketone restores enzyme catalysis, asymmetric reduction reaction, production IV compounds occur for Formula V compound；

B) formula IV compound in organic solvent with bromide reagent occur bromo-reaction, then weak base effect under with para-fluoroaniline Formula III compound is obtained by the reaction；

Reaction equation is as follows：

Wherein, R is hydroxyl protection base, and R ' is ester residue；

Wherein, aldehyde ketone reductase has SEQ ID NO：Amino acid sequence shown in 1.

2. preparation method according to claim 1, it is characterised in that：R be selected from silicon ether protecting group, acetyl group, benzoyl, Benzyl, MOM, C₁-C₄Alkyl, THP.

3. preparation method according to claim 1, it is characterised in that：R ' is C₁-C₄Alkyl.

4. preparation method according to claim 1, it is characterised in that：The reaction of step a) is the water in pH value 5.0-8.0 It is carried out in solution.

5. according to the preparation method described in any one of claim 1-4, it is characterised in that：In step a), the Formula V chemical combination A concentration of 10-1000g/L of object in the reaction system, aldehyde ketone reduction enzyme dosage is 1-20g/L.

6. preparation method according to claim 1, it is characterised in that：Also contain isopropanol in the reaction system of step a), Or the combination containing NADP+, glucose and glucose dehydrogenase.

7. preparation method according to claim 6, it is characterised in that：The dosage of isopropanol is the 2%- of reaction system volume 10%.

8. preparation method according to claim 6, it is characterised in that：Glucose dosage be 1-20g/L, glucose dehydrogenase Dosage for 100-1000U/L, the dosage of NADP+ is 0.02-0.1mmol/L.

9. preparation method according to claim 1, it is characterised in that：The bromide reagent is selected from phosphorus tribromide, pentabromo- Change phosphorus, carbon tetrabromide.

10. preparation method according to claim 1, it is characterised in that：The weak base is selected from ethylenediamine, diisopropyl second Base amine, N-methylmorpholine, to dimethylaminopyridine, triethylamine.

11. preparation method according to claim 1, it is characterised in that：In step b), formula IV compound and bromide reagent Molar ratio is 1:The molar ratio of 1-3, formula IV compound and para-fluoroaniline is 1:The molar ratio of 1-3, weak base and para-fluoroaniline is 1:2-6。