EP4662215A1 - Process for preparing trilaciclib or a salt thereof - Google Patents

Abstract

Process for the preparation of trilaciclib having formula ( I ) : (I) or a salt thereof, wherein the use of the intermediate of formula (VIII) is envisaged: (VIII) wherein PG is a protecting group, which mainly has the function of avoiding the formation of the impurities of formula (XII) and (XIII). Furthermore, the presence of this protecting group makes the compound (VIII) more reactive, due to the electron-withdrawing effect of the amide carbonyl.

Description

Translation (Rule 12.3) 01 February 2024

PROCESS FOR PREPARING TRILACICLIB OR A SALT THEREOF

Technical field.

The present invention concerns a process for preparing the active ingredient trilaciclib or a salt thereof . The present invention also concerns an intermediate for the synthesis of trilaciclib. State of the art.

Trilaciclib is an active ingredient having formula

(I) •

This active ingredient is able to temporarily arrest normal cells to prevent chemotherapy-induced myelosuppression and therefore improve anti-tumor efficacy. It can be used, for example, in patients with small cell lung cancer (SCLC) receiving t opotecan-based chemotherapy .

International patent application WO 2016/040858 reports a synthesis route of trilaciclib (in particular, see page 96, scheme 9) wherein isolation of the key intermediates occurs using chromatographic techniques (on silica gel) , which make the process not applicable on an industrial scale.

The synthesis process according to WO ' 858 is shown in the following scheme 1: Scheme 1

In the final step, the aforementioned process involves the reaction of the compound corresponding to intermediate VIII but having the free amide nitrogen (Villa) with the compound (IX) , wherein in the compound (Villa) the amide nitrogen is free.

However, the Applicant has found that the free amide nitrogen can act as a nucleophile and cause side reactions between the free nitrogen of the trilaciclib that is formed and the chlorine of the intermediate (Villa) above.

These side reactions lead in particular to the formation of the following impurities:

(XIII) .

International application WO 2018/005865 describes a further synthesis route of trilaciclib, summarized by the following scheme 2:

Scheme 2

The yield of the final step leading to the formation of trilaciclib is approximately 64% (see the example on page 88 of WO' 865, preparation of compound 19) , while the overall process yield for the synthesis of trilaciclib is only 15.7%.

Furthermore, the free amide of intermediate 11 is quantitatively deprotonated in the presence of a strong base, such as lithium bis ( trimethylsilyl ) amide (LiHMDS) used in step 1. The Applicant believes that the use of a strong base in this step of the process is the reason why the previously reported low yield is obtained, which is far from a standard suitable for an industrializable process, in addition to the consequent formation of undesired by-products . A further disadvantage of the above process is the use of a large excess of compound (IX) , equal to 3 equivalents, which also makes the process disadvantageous from an economic point of view.

Therefore, the need is felt to find a process for the synthesis of trilaciclib which is more easily industrialized and which allows an advantageous control of the profile of the impurities that can form, avoiding in particular the formation of impurities of formula (XII) and (XIII) .

Summary of the invention.

The Applicant has now found that it is possible to achieve the aforementioned objectives and others which will be better illustrated below through a process for preparing trilaciclib, or a salt thereof, wherein the presence of a protecting group on the nitrogen atom of the -NH- group in the intermediate of formula (Villa) is provided, which allows avoiding the formation of the impurities of formula (XII) and (XIII) . Furthermore, the presence of this protecting group makes the compound (VIII) more reactive, due to the electron-withdrawing effect of the amide carbonyl. This allows the coupling reaction with compound (IX) to be conducted at lower temperatures than WO' 858, with a consequent further reduction in the formation of impurities and an increase in the trilaciclib yield.

Furthermore, the process according to the present invention preferably provides for isolating reaction intermediates by crystallization: this makes the process advantageously industrializable, unlike the chromatographic techniques used in the prior art.

Therefore, in accordance with a first aspect, the present invention concerns a process for preparing trilaciclib having formula (I) : or a salt thereof; which comprises: a) reacting a compound of formula (II) : or a salt thereof, with a compound of formula (III) : or salt thereof, wherein PG is a protective group, to obtain the compound of formula (IV) : (IV) ; b) isolating the compound of formula (IV) ; c) reacting the compound of formula (IV) with the compound of formula (V) : in a molar ratio comprised between 1:1 and 1:1.50 and in the presence of a catalyst, to obtain a compound of formula (VII) : d) isolating the compound of formula (VII) ; e) reacting the compound of formula (VII) with an acid, subsequently with an oxidizing agent and subsequently with a nucleophilic base, to obtain a

(VIII) ; f) reacting the compound of formula (VIII) with a compound of formula (IX) : in the presence of a phosphine ligand, a metal catalyst and a base, in an organic solvent, to obtain a compound of formula (X) : g) isolating the compound of formula (X) ; h) converting the compound of formula (X) into trilaciclib of formula (I) , or a salt thereof .

In a preferred embodiment, the protecting group PG is a protecting group labile under acidic conditions, preferably a tert-butyloxycarbonyl-derived group, more preferably BOG (tert-butyloxycarbonyl) .

In another preferred embodiment, the PG protecting group is a hydrogenation labile protecting group, preferably a carbobenzyloxy-derived group, more preferably CBZ (carbobenzyloxy) .

In a preferred embodiment, step e) is carried out in a single reaction environment, without separation of the intermediates (one-pot reaction) .

In accordance with another aspect, the present invention concerns a compound of formula (X) : wherein PG is a protective group, preferably a protective group as defined above.

Further aspects, characteristics and advantages of the invention will be evident from the following detailed description .

Brief description of the figures

Figure 1 shows an NMR spectrum relating to the compound of formula (Xi) .

Figure 2 shows an IR spectrum relating to the compound of formula (Xi) .

Figure 3 shows an NMR spectrum relating to the compound of formula (Vile) .

Figure 4 shows an NMR spectrum relating to the compound of formula (Vlld) .

Figure 5 shows a diagram of the process according to the invention.

Detailed description of the invention

For the purposes of the present invention, in the description and claims that follow, the definitions of the numerical intervals include the individual values within the interval and its endpoints, unless otherwise specified .

For the purposes of the present invention, in the description and claims that follow, the term "comprising" also includes the terms "essentially consisting of" or "consisting of".

According to a preferred aspect, the compound of formula (III) , or a salt thereof, which reacts in step a) with the compound of formula (II) , is an acetate salt.

Preferably, step a) is carried out in a solvent selected from:

(a) aprotic polar solvents, preferably ethers, esters, ketones, carbonates, acetonitrile;

(b) water;

(c) apolar solvents selected from toluene and di chloromethane ; or mixtures thereof .

According to a preferred aspect, the solvent used in step a) is a mixture of water and an aprotic polar solvent, preferably an ether, more preferably methyltetrahydrof uran (Me-THF) .

According to a preferred aspect, in step b) the compound of formula (IV) is isolated by crystallization, preferably by adding a mixture comprising water and a water-soluble solvent selected from C1-C4 alcohols and acetonitrile. Preferably the C1-C4 alcohol is selected from: ethanol (EtOH) , isopropanol (IPA) , butanol (BuOH) , and mixtures thereof, more preferably tert-butanol (t- BuOH) .

After the isolation of step b) , the compound of formula (IV) generally has a purity > 95%.

With reference to step c) , the catalyst used is preferably a catalyst based on copper II or copper I, more preferably it is CuC12.

According to a preferred aspect, step c) is carried out in an anhydrous environment, preferably with a water content not exceeding 2% by weight, determined according to the Karl-Fisher method.

The use of an anhydrous environment allows operating with reduced quantities of compound (V) (with reference to the specific molar ratio as reported) , making the subsequent step d) of isolation of compound (VII) more easily achievable on an industrial level.

According to a further preferred aspect, step c) is carried out in a high boiling solvent, preferably a high boiling aprotic polar solvent, more preferably dimethyl sulfoxide (DMSO) or a mixture of DMSO with another solvent, more preferably a mixture of DMSO with toluene. "High boiling solvent" means a solvent that has a boiling point above 100 °C.

Preferably, step d) occurs via extraction from the reaction mixture, preferably with a total volume of less than 40 volumes with respect to the loaded compound of formula (IV) , and subsequent crystallization.

Preferably, as regards the extraction of compound (VII) , this takes place starting from an organic solvent selected from ethers or esters, more preferably Me-THF, and treatment with an aqueous solution comprising water and a salt. Said salt is preferably selected from inorganic salts, more preferably NH4CI .

According to a preferred aspect, step e) includes the following steps, which are preferably carried out in a single reactor, without separation of the intermediates (one-pot reaction) : i) reacting the compound of formula (VII) with an acid, preferably with acetic acid, to obtain the compounds of formula (Vila) , (Vllb) or mixtures thereof; ii) converting the compounds of formula (Vila) , (Vllb) or mixtures thereof, into the compound of formula (Vile) by adding an oxidizing agent, preferably a hydroperoxidic oxidizing agent, more preferably tertbutylhydroperoxide, and subjecting the mixture to distillation, preferably to sequential distillations; iii) converting the compound of formula (Vile) into the compound of formula (VIII) by treatment with a nucleophilic base, preferably selected from DMAP (4- dimethylaminopyr idine ) , DBN ( 1 , 5-diazabicyclo [ 4.3.0 ] non-5-ene ) , TBD ( triazabicyclodecene ) , DBU (1, 5- diazabicyclo ( 5.4.0 ) undec-7-ene ) , preferably DBN and DBU, more preferably DBU, and to isolate the compound of formula (VIII) , preferably by crystallization.

According to an alternative embodiment, step ii) can be carried out using peracetic acid as an oxidizing agent to obtain the compound of formula (VIII) . In the latter case, without being bound to any theory, it is believed that the compound (VIII) is formed by spontaneous rearrangement of the intermediate of formula (Vile) :

In step f) (coupling reaction) the phosphinic ligand is preferably a bidentate phosphinic ligand. Preferably the bidentate phosphinic ligand is selected from: BINAP ( 1 , 1 ' -bi snaphthalene-2 , 2 ' -diyl- bis (diphenylphosphine) ) , DPEPhos (bis [ (2- diphenylphosphino ) phenyl ] ether ) and DPPF (1, 1 '- ferrocenediyl-bis (diphenylphosphine) ) .

As regards the metal compound used in step f ) , said metal compound is preferably a palladium containing compound, more preferably palladium acetate. The metal compound is used as a catalyst.

In step f) the catalyst is preferably a palladium (Pd) compound, more preferably palladium acetate. Preferably, the catalyst has a Pd content not exceeding 0.05 molar eq. Reactions that operate using such a low palladium amounts are not reported in the prior art.

In step f) the base is preferably selected from amines and inorganic carbonates, more preferably it is an inorganic carbonate, in particular cesium carbonate.

In step f) the organic solvent is preferably selected from: amides, esters, ethers, ureas, and mixtures thereof . More preferably the organic solvent is selected from: dioxane, dimethylisosorbate, dimethylcarbonate, N-butyl-pyrrolidone, N-methyl- pyrrolidone (NMP) , DMPU ( 1 , 3-dimethyl-3 , 4 , 5 , 6 - tetrahydro-2 ( 1H ) -pyr imidinone ) , DMI ( 1 , 3-dimethyl-2- imidazolidinone ) , tetramethylurea. Particularly preferred is dimethylcarbonate.

In step g) the isolation of compound (X) preferably takes place by crystallization. Preferably, the crystallization is carried out in a solvent which can be selected from: esters, ethers, ureas, alcohols, optionally mixed with water. In particular, the isolation of the compound of formula (X) carried out with alcohols or a mixture of alcohols and water allows the product (X) to be obtained with a reduced Pd content .

Preferably, the compound (X) has a Pd content less than or equal to 30 ppm, more preferably less than or equal to 20 ppm, even more preferably less than or equal to 10 ppm, even more preferably less than or equal to 5 ppm. Preferably, the Pd content is in the range of from 0.01 ppm to 6 ppm, more preferably from 0.01 ppm to 5 ppm .

In step h) the compound of formula (X) is converted into trilaciclib or a salt thereof, preferably into trilaciclib bis-trif luoroacetate . In this preferred aspect the conversion takes place through acid hydrolysis by trif luoacetic acid. It is subsequently possible to convert the trilaciclib salt thus obtained into another salt, in particular into triaciclib bis hydrochloride, or into trilaciclib base, according to known techniques.

In a preferred embodiment, the process of the invention is carried out according to the scheme shown in Figure 5. In particular, in said scheme step e) is a one-pot type reaction.

Examples

The following working examples are provided for the sole purpose of illustrating the present invention and must not be understood as limiting the scope of protection defined by the attached claims.

Example 1. Preparation of the intermediate (IV) . 100 g of the compound of formula (II) , 120 g of the compound of formula (III) wherein the PG protecting group is Boc (tert-butyloxycarbonyl) , 90 g of K2CO3, 350 mL of demineralized water and 200 mL of Me-THF (methyltetrahydrofuran) were loaded at room temperature. The reaction mixture was heated to 60-65 °C and the reaction was left to continue until complete. When the reaction was complete, the reaction mixture was cooled to room temperature and 800 mL of Me-THF was subsequently added .

The organic phase was recovered, 500 mL of water was added to the latter and the mixture was brought to pH 4.8 with acetic acid.

The organic phase was recovered, to which a K2CO3 aqueous solution was added until a pH of 7.5. The organic phase was recovered and 500 mL of water was added to the same. The organic phase was recovered again and the solvent was changed to tert-butanol. The product was then crystallized by adding water, which acts as an antisolvent .

A product of formula (IV) was obtained with a purity of about 95% and a molar yield of about 75%.

Example 2. Preparation of the intermediate (VII) .

100 g of the compound of formula (IV) , 35 g of sodium iodide, 6.52 g of 6-methylpicolinic acid, 98.6 g of potassium carbonate, 700 mL of DMSO (dimethyl sulfoxide) were loaded at room temperature. From the mass, 200 mL were distilled under vacuum, then the system was inertized with nitrogen.

The reaction mixture was heated to 110-115 °C, to which 3.2 g of CuC12 and 33.5 g of propargylaldehyde diethylacetal were then added, the mixture was then washed at the end with 100 mL of DMSO. The reaction was left to continue until complete. Once the reaction was complete, the reaction mixture was cooled to room temperature and 1 L of Me-THF and 1.3 L of 20% by weight aqueous ammonium chloride solution were then added.

The organic phase was recovered, to which 500 mL of a 10% aqueous solution of sodium sulfite were added. The organic phase was recovered and 500 mL of water were added to the same. The organic phase was recovered again and 100 mL of MeTHF and 500 mL of water were added. The organic phase was then recovered and a solvent change with iso-propanol was carried out. The product was then crystallized by adding water, which acts as an antisolvent .

The compound of formula (VII) was obtained with a purity greater than 90% and a molar yield of approximately 75%. Example 3. Preparation of the intermediate (VIII) .

40 g of the compound of formula (VII) , 400 mL of ACN (acetonitrile) and 6.5 mL of TFA (trifluoroacetic acid) were loaded at room temperature, the mixture was left to react for one hour. 13.2 g of a 70% aqueous solution of tert-butylhydroperoxide were then added to the same.

Subsequently, the water was eliminated by subsequent distillations under vacuum, obtaining a solution with a volume of approximately 200 mL .

The solution thus obtained was added to a solution of 40 mL of ACN and 25.5 mL of DBU at 10°-15°C. When the addition was completed, the reaction was left to reach 15-20 °C until complete; the precipitated product was recovered by filtration. The compound of formula (VIII) was obtained with a purity greater than 97% and a molar yield of approximately 75%.

Example 4. Preparation of the intermediate (X) .

25 g of the compound of formula (VIII) , 15.4 g of the compound of formula (IX) , 31.25 g of cesium carbonate, 140 mg of palladium acetate, 895 mg of DPPF ( 1 , 1 ' -f errocenediyl-bis ( diphenylphosphine ) ) were loaded in a nitrogen-inerted system. Subsequently, 240 mL of degassed dimethylcarbonate were added and the reaction mass was heated to 80°C and left to react for 30 min. Next, 358 mg of DPPF were added and the reaction was left to react until complete. The product precipitated as it formed.

When the reaction was complete, the reaction mixture was concentrated under vacuum to a volume of 125 mL, then 162 mL of methanol and 162 mL of water were added by dripping. The product was recovered by filtration .

A product of formula (X) was obtained with a purity greater than 97% and a molar yield of approximately 85% and a palladium content lower than 20 ppm.

Example 5. Preparation of trilaciclib bis- trifluoroace tat e.

23 g of compound of formula (X) , 115 mL of acetic acid and 9.7 mL of TFA were loaded at room temperature. The reaction mixture was heated to 65°C and left to react until complete. When the reaction was complete, the mixture was cooled to 40°C, then 70 mL of isopropanol and 230 mL of toluene were added by dripping. Precipitation of the product was then observed. The mixture was then cooled to room temperature and stirred for about one hour. The product was recovered by filtration. Trilaciclib bis-trif luoroacetate was obtained with a purity greater than 99% and a molar yield of approximately 90%.

Example 6. Preparation of trilaciclib bishydrochloride.

10 g of trilaciclib bis-trif luoroacetate, 80 mL of methanol and 20 mL of water were loaded. The mass was heated to 50°C and subsequently 3.6 mL of a 37% aqueous HC1 solution were added by dripping, then the mixture was cooled to room temperature. Precipitation of the product was observed. After about one hour, 80 mL of acetone were added by dripping. The product was recovered by filtration. Trilaciclib dishydrochloride was obtained with a purity greater than 99% and a molar yield of approximately 95%.

It is important to note that, on the basis of the data reported above, the process according to the present invention is more efficient in terms of yield compared to that described in WO 2018/005865 both as regards the coupling step of the intermediate (VIII) (85% yield versus 63.7%) , and for the entire process. In fact, the process according to the present invention allows increasing the trilaciclib overall yield by at least 10 percentage points compared to WO ' 865.

Claims

1. Process for preparing Trilaciclib having formula ( I ) : or a salt thereof; which comprises: a) reacting a compound of formula (II) : or a salt thereof, with a compound of formula (III) : or salt thereof, wherein PG is a protective group, to obtain the compound of formula (IV) : b) isolating the compound of formula (IV) ; c) reacting the compound of formula (IV) with the compound of formula (V) : in a molar ratio comprised between 1:1 and 1:1.50 and in the presence of a catalyst, to obtain a compound of f (VII) ; d) isolating the compound of formula (VII) ; e) reacting the compound of formula (VII) with an acid, subsequently with an oxidizing agent and subsequently with a nucleophilic base, to obtain a compound of formula (VIII) :

(VIII) ; f) reacting the compound of formula (VIII) with a compound of formula (IX) : in the presence of a phosphine ligand, a metal catalyst and a base, in an organic solvent, to obtain a compound of formula (X) :

(X) ; g) isolating the compound of formula (X) ; h) converting the compound of formula (X) into Trilaciclib of formula (I) , or a salt thereof .

2. Process according to claim 1, wherein the protecting group PG is a protecting group labile under acidic conditions, preferably a tert-butyloxycarbonyl- derived group, more preferably BOG (tert- butyloxycarbonyl ) .

3. Process according to claim 1, wherein the PG protecting group is a hydrogenation labile protecting group, preferably a carbobenzyloxy-derived group, more preferably CBZ (carbobenzyloxy) .

4. Process according to any one of the preceding claims, wherein step e) is carried out in a single reaction environment, without separation of the intermediates (one-pot reaction) .

5. Process according to any one of the preceding claims, wherein the compound of formula (III) is in the form of an acetate salt.

6 . Process according to any one of the preceding claims, wherein step a) is carried out in a solvent selected from:

(a) aprotic polar solvents, preferably ethers, esters, ketones, carbonates, acetonitrile; (b) water;

(c) apolar solvents selected from toluene and di chloromethane ; or mixtures thereof .

7. Process according to claim 6, wherein the solvent used in step a) is a mixture of water and an aprotic polar solvent, preferably an ether, more preferably methyltetrahydrofuran (Me-THF) .

8. Process according to any one of the preceding claims, wherein in step b) the compound of formula (IV) is isolated by crystallization, preferably by adding a mixture comprising water and a water-soluble solvent selected from C1-C4 alcohols and acetonitrile, preferably tert-butanol (t-BuOH) .

9. Process according to any one of the preceding claims, wherein after the isolation of step b) , the compound of formula (IV) has a purity > 95%.

10. Process according to any one of the preceding claims, wherein in step c) the catalyst is a copper II or copper I based catalyst, preferably is CuC12.

11. Process according to any one of the preceding claims, wherein step c) is carried out in an anhydrous environment, preferably with a water content not exceeding 2% by weight, determined according to the Karl- Fisher method.

12. Process according to any of the preceding claims, wherein step c) is carried out in a high boiling solvent, preferably a high boiling aprotic polar solvent, more preferably dimethyl sulfoxide (DMSO) or a mixture of DMSO with another solvent, more preferably a mixture of DMSO with toluene.

13. Process according to any one of the preceding claims, wherein step e) comprises the following steps: i) reacting the compound of formula (VII) with an acid, preferably with acetic acid, to obtain the compounds of formula (Vila) , (Vllb) or mixtures thereof; ii) converting the compounds of formula (Vila) , (Vllb) or mixtures thereof, into the compound of formula (Vile) by adding an oxidizing agent, preferably a hydroperoxidic oxidizing agent, more preferably tertbutylhydroperoxide, and subjecting the mixture to distillation, preferably to sequential distillations; iii) converting the compound of formula (Vile) into the compound of formula (VIII) by treatment with a nucleophilic base, preferably selected from DMAP (4- dimethylaminopyr idine ) , DBN ( 1 , 5-diazabicyclo [ 4.3.0 ] non-5-ene ) , TBD ( triazabicyclodecene ) , DBU (1,5- diazabicyclo ( 5.4.0 ) undec-7-ene ) , preferably DBN and DBU, more preferably DBU, and to isolate the compound of formula (VIII) , preferably by crystallization.

14. Process according to any one of the preceding claims, wherein in step f) (coupling reaction) the phosphinic ligand is a bidentate phosphinic ligand, preferably selected from: BINAP ( 1 , 1 ' -bisnaphthalene- 2 , 2 ' -diyl-bis ( diphenylphosphine ) ) , DPEPhos (bis [ (2- diphenylphosphino ) phenyl ] ether ) and DPPF (1, 1 '- ferrocenediyl-bis (diphenylphosphine) ) .

15. Process according to any one of the preceding claims, wherein in step f) the catalyst is a palladium compound (Pd) , preferably palladium acetate.

16. Process according to claim 15, wherein the catalyst has a Pd content not higher than 0.05 molar eq.

17. Process according to any one of the preceding claims, wherein in step f) the base is selected from amines and inorganic carbonates, preferably is an inorganic carbonate, in particular cesium carbonate.

18. Process according to any one of the preceding claims, wherein in step f) the organic solvent is selected from: amides, esters, ethers, ureas, or mixtures thereof, preferably the organic solvent is selected from: dioxane, dimethylisosorbate, dimethylcarbonate, N-butyl-pyrrolidone, N-methyl- pyrrolidone (NMP) , DMPU ( 1 , 3-dimethyl-3 , 4 , 5 , 6 - tetrahydro-2 ( 1H ) -pyr imidinone ) , DMI ( 1 , 3-dimethyl-2- imidazolidinone ) , tetramethylurea.

19. Process according to any one of the preceding claims, wherein in step g) the isolation of the compound (X) takes place by crystallization, preferably in a solvent selected from: esters, ethers, ureas, alcohols, optionally mixed with water.

20. Compound of formula (X) : wherein PG is a protective group.

21. Compound according to claim 20, wherein the protecting group PG is a protecting group labile under acidic conditions, preferably tert-butyloxycarbonyl- derived group, more preferably BOC (tert- butyloxycarbonyl) .

22. Compound according to claim 20, wherein the PG protecting group is a hydrogenation labile protecting group, preferably a carbobenzyloxy-derivative group, more preferably CBZ (carbobenzyloxy) .

23. Compound according to any one of claims from 20 to 22, having a Pd content lower than or equal to 30 ppm, preferably lower than or equal to 20 ppm, more preferably lower than or equal to 10 ppm, even more preferably lower than or equal to 5 ppm.