PROCESS FOR THE PREPARATION OF ELUXADOLINE

FIELD OF THE INVENTION

The present invention relates to a process for the preparation of Eluxadoline or pharmaceutically acceptable salts thereof and its intermediates. The present invention also relates to a process for the preparation of crystalline form a of Eluxadoline.

BACKGROUND OF THE INVENTION

Diarrhea-predominant irritable bowel syndrome is a chronic disorder that affects about 28 million patients. Opioid receptors are a group of inhibitory G protein-coupled receptors with opioids as ligands. Opioid ligands can be usefully employed to normalize altered visceral sensitivity in IBS patients. Mu (μ), kappa (κ), and delta (δ) opioid receptors represent the originally classified receptor subtypes, with opioid receptor like- 1 (ORL1) being the least characterized.

Eluxadoline (designated as VIBERZI ^® ) chemically represented as 5-[[[(2S)-2- amino-3 -[4-(aminocarbonyl)-2, 6-dimethylphenyl] - 1 -oxopropyl] [(1S)-1 -(4-phenyl- 1H- imidazol-2-yl) ethyl]amino]methyl]-2-methoxy benzoic acid is a mu-opioid receptor agonist, indicated in adults for the treatment of irritable bowel syndrome with diarrhea (IBS-D). Its chemical

(I)

WO 2005/090315 discloses Eluxadoline and pharmaceutically acceptable enantiomers, diastereomers, racemates, and salts thereof, methods for its preparation, pharmaceutical composition and their use in the treatment of disorders that may be ameliorated or treated by the modulation of opioid receptors. WO 2009/009480 describes process for making the zwitterion of Eluxadoline and two novel crystals of this zwitterion, namely crystalline form a and β of Eluxadoline and process for their preparation. Example 2 of WO '480 describes the process for the preparation of crystalline form a of Eluxadoline by storing the zwitterion of Eluxadoline at 0-25% relative humidity for 3 days.

WO 2017/015606, WO 2017/153471 and WO 2017/191650 describe processes for preparation of Eluxadoline. The method for the preparation of crystalline form a (alpha) of Eluxadoline described in the literature is difficult to operate at large scale and thus rendering them unsuitable for commercial scale. Therefore, there remains a need for the environmental friendly, highly pure, cost effective and industrially applicable process for the preparation of crystalline form a of Eluxadoline.

The processes for preparation of Eluxadoline described in the literature involves the reaction of the suitable amine with the suitable carboxylic acid under standard peptide coupling conditions with a carbodiimide coupling agent such as N-(3- Dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride (EDCI) and an additive such as hydroxybenzotriazole (HOBt) to prevent racemization for introduction of the carboxamide moiety in Eluxadoline.

WO 2017153471 describes use of 2-chloro-4, 6-dimethoxy-l, 3, 5-triazine (CDMT) for introducing the carboxamide function in Eluxadoline.

The present inventors have surprisingly found that introduction of the carboxamide moiety in Eluxadoline is better achieved by using quinoline based coupling agent, l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ) and isobutyl 1, 2- dihydro-2-isobutoxy-l-quinolinecarboxylate (IIDQ). The use of quinoline based coupling reagent involves direct coupling as the mixed carbonic anhydride intermediate is consumed very rapidly by the amino-component as soon as it is formed. This minimizes racemization during product formation, minimizes side reactions and workup is simple. 1- Isobutoxycarbonyl-2-isobutoxy-l, 2-dihydroquinoline (IIDQ) is an improved version of EEDQ. Both reagents are easily prepared, easily stored, and not prone to side reactions or racemization. No additives to prevent racemization and tertiary amine bases are needed for these reactions.

Furthermore the processes of the present invention are found to be highly cost effective, high yielding and industrially feasible process for the preparation of Eluxadoline.

SUMMARY OF THE INVENTION

The present invention provides a process for the preparation of Eluxadoline of formula (I) or pharmaceutically acceptable salts thereof and its intermediates. The present invention also provides a process for the preparation of crystalline form a of Eluxadoline. Moreover, the present invention provides a process for preparation of Eluxadoline of formula (I) comprising of reacting compound of formula (IV) with compound of formula (V) to provide compound of formula (VI) in the presence of a coupling agent such as 1- ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ), wherein no additives to prevent racemization and tertiary amine bases are required.

BRIEF DESCRIPTION OF THE FIGURE

Figure 1 : depicts the a - crystalline form of Eluxadoline

DETAILED DESCRIPTION OF THE INVENTION

The term "room temperature" as used herein refers to a temperature in the range of about 25°C to about 30°C. The term "alkyl group" means a straight or branched saturated monovalent hydrocarbon chain having 1 to 12 carbon atoms. The suitable alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, pentyl, hexyl, isohexyl, heptyl, 4, 4- dimethylpentyl, octyl, 2,2,4-trimethylpentyl, nonyl, decyl, and various branched chain isomers thereof. Further, the alkyl group may optionally be substituted.

The terms "arylalkyl" refer to alkyl groups as described above having an aryl substituent. The term "aryl group" means a monocyclic or bicyclic monovalent aromatic hydrocarbon group having 6 to 10 carbon atoms. Suitable arylalkyl group include - CH2C6H5 and -C2H4C6H5. Further, the arylalkyl group may optionally be substituted.

The term "nitrogen protecting group" as defined herein, shall mean a group which is attached to a nitrogen atom to protect said nitrogen atom from participating in a reaction and which may be readily removed following the reaction. A suitable nitrogen protecting group is selected from tert-butoxy carbonyl (BOC), benzyloxy carbonyl (CBz), acetyl (Ac), triflouoroacetyl (TFA), benzyl (Bn), dibenzyl, phthalimido, tosyl (Ts), p- methoxybenzylcarbonyl, 9-fluorenylmethyloxycarbonyl (FMOC), carbamate, p- methoxybenzyl (PMB), p-methoxyphenyl (PMP), tosyl (Ts), phenyl sulfonyl, trimethylsilylethoxymethyl (SEM) and benzoyl (Bz). Other suitable nitrogen protecting groups may be found in texts such as T. W. Greene & P. G. M. Wuts, Protective Groups in Organic Synthesis, John Wiley & Sons, 1991. The term "absence of additive" as defined herein, shall mean absence of 2- hydroxypyridine-N-oxide (HOPO), N-hydroxysuccinimide (HOSu), N-hydroxy-5- norbornene-2,3-dicarboximide (HONB), 1-hydroxybenzotriazole (HOBt), 6-chloro-l- hydroxybenzotriazole (6-Cl-HOBt), l-hydroxy-7-azabenzotriazole (HO At), 3-hydroxy-4- oxo-3,4-dihydro-l,2,3-benzotriazine (HODhbt) and its aza derivative (HODhat) and the like, which are helpful in reducing racemization in reactions involving amide bond formation.

The processes according to this invention are described in detail. The reaction conditions such as reagents, catalysts, solvents and temperature given are meant to provide preferred ranges and examples for the respective transformation that can be principally applied but are not supposed to restrict them to the selection given. In one embodiment, the present invention provides a process for the preparation of crystalline form a of Eluxadoline; comprising the steps of:

(a) providing Eluxadoline in a ketone solvent;

(b) heating the reaction mixture;

(c) optionally cooling; and

(d) isolating the crystalline form a of Eluxadoline.

Providing of Eluxadoline in step (a) includes:

(i) direct use of reaction mixture containing Eluxadoline that is obtained during its synthesis; or

(ii) dissolving or suspending Eluxadoline in a ketone solvent.

Any physical form (i.e., crystalline or amorphous) of Eluxadoline may be utilized in step (a). Eluxadoline that may be used as the input for the process of the present invention may be obtained by any process including the process described in the art (for e.g., WO 2005/090315 Al and WO2018/020450 A2) or by process of the present invention.

The ketone solvent of step (a) may be selected from the group consisting of acetone, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone or mixtures thereof in any suitable proportion. More preferably acetone may be used in any suitable proportion.

The reaction mixture obtained in step (a) may be heated at reflux temperature of the solvent for a period of about 10 minutes to about 40 hours. Optionally, the solution obtained above may be filtered to remove any insoluble particles. The insoluble particles may be removed suitably by filtration, centrifugation, decantation or any other suitable techniques. The solution may optionally be treated with carbon, hyflow or any other suitable material to remove colour and/or to clarify the solution.

The reaction mixture obtained in step (b) may be cooled to a temperature from about 0°C to about room temperature, preferably to room temperature. The stirring may be carried for a period of about 10 minutes to about 30 hours. Optionally, the resultant mixture may be further seeded with previously prepared crystals of a form of Eluxadoline. The obtained precipitate may be isolated using conventional techniques known in the art. One skilled in the art may appreciate that there are many ways to separate a solid from the mixture, for example it may be separated by using any techniques such as filtration, centrifugation, decantation and the like. After separation, the solid may optionally be washed with a suitable solvent. The obtained crystalline form a of Eluxadoline may optionally be further dried. Drying may be suitably carried out in equipment such as tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer and the like. The drying may be carried out at a temperature about 35°C to about 70°C, optionally under reduced pressure. The drying may be carried out for any time periods necessary for obtaining a product with desired purity such as from about 1 hour to about 25 hours or longer.

In another embodiment, the present invention provides a process for the preparation of crystalline form a of Eluxadoline; comprising the steps of:

(a) providing Eluxadoline in acetone;

(b) heating the reaction mixture;

(c) cooling to room temperature; and

(d) isolating the crystalline form a of Eluxadoline.

Any physical form (i.e., crystalline or amorphous) of Eluxadoline may be utilized in step (a). Eluxadoline that may be used as the input for the process of the present invention may be obtained by any process including the process described in the art (for e.g., WO 2005/090315 Al and WO2018/020450 A2) or by the process of the present invention. The suspension obtained in step (a) may be heated at a reflux temperature, preferably at a temperature about 50°C to about 60°C for a period about 10 minutes to about 40 hours. Optionally, the resultant mixture may be further seeded with previously prepared crystals of a form of Eluxadoline.

The reaction mixture obtained in step (b) may be cooled to room temperature followed by stirring for a period about 10 minutes to about 30 hours, preferably about 1 hour to about 3 hours.

The obtained precipitate may be isolated using conventional techniques known in the art. One skilled in the art may appreciate that there are many ways to separate a solid from the mixture, for example it may be separated by using any techniques such as filtration, centrifugation, decantation and the like. After separation, the solid may optionally be washed with a suitable solvent. The obtained crystalline form a of Eluxadoline may optionally be further dried. Drying may be suitably carried out in equipment such as tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer and the like. The drying may be carried out at temperature about 35°C to about 70°C, optionally under reduced pressure. The drying may be carried out for any time periods necessary for obtaining a product with desired purity such as from about 1 hour to about 25 hours or longer. In yet another embodiment, the present invention provides a process for the preparation of crystalline form a of Eluxadoline; comprising the steps of:

(a) providing Eluxadoline in a mixture of acetone and water;

(b) heating the reaction mixture;

(c) cooling to room temperature; and

(d) isolating the crystalline form a of Eluxadoline.

Any physical form (i.e., crystalline or amorphous) of Eluxadoline may be utilized in step (a). Eluxadoline that may be used as the input for the process of the present invention may be obtained by any process including the process described in the art (for e.g., WO 2005/090315 Al and WO2018/020450 A2) or by the process of the present invention. The reaction mixture obtained in step (a) may be heated at a reflux temperature, preferably at a temperature of about 50°C to about 60°C, more preferably at a temperature of about 30°C to 40°C for a period about 10 minutes to about 40 hours. Optionally, the reaction mixture of step (a) may be seeded with previously prepared crystals of a form of Eluxadoline.

The solution obtained in step (b) may be cooled to room temperature followed by stirring for a period about 10 minutes to about 30 hours, preferably about 1 hour to about 3 hours.

The obtained precipitate may be isolated using conventional techniques known in the art. One skilled in the art may appreciate that there are many ways to separate a solid from the mixture, for example it may be separated by using any techniques such as filtration, centrifugation, decantation and the like. After separation, the solid may optionally be washed with a suitable solvent. The obtained crystalline form a of Eluxadoline may optionally be further dried. Drying may be suitably carried out in equipment such as tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer and the like. The drying may be carried out at temperature about 35°C to about 70°C, optionally under reduced pressure. The drying may be carried out for any time periods necessary for obtaining a product with desired purity such as from about 1 hour to about 25 hours or longer.

In an aspect of the present invention, crystalline form a of Eluxadoline prepared according to the processes of the present invention can be substantially pure having a chemical purity greater than about 99% by weight as determined using high performance liquid chromatography.

In yet another aspect, the present invention provides pharmaceutical composition comprising crystalline form a of Eluxadoline prepared according to process of present invention with one or more pharmaceutically acceptable excipients and their use in the treatment of disorders that may be ameliorated or treated by the modulation of opioid receptors. The term "pharmaceutically acceptable excipients" used in the pharmaceutical composition of invention comprise but are not limited to diluents, binders, pH stabilizing agents, disintegrants, surfactants, glidants and lubricants known in the art. In a further embodiment the present invention provides a process for the preparation of Eluxadoline of formula (I) or pharmaceutically acceptable salts thereof; comprising the steps of:

(a) contacting a compound of formula (II) and a compound of formula (III), wherein R ¹ is lower alkyl or aryl alkyl; in the presence of a hydride source to obtain the compound of formula (IV);

(IV)

(b) optionally, providing the compound of formula (IV) and an acid in a suitable solvent to obtain the compound of formula (IV.Acid);

(c) optionally, contacting the compound of formula (IV.Acid) with a base in a suitable solvent to obtain compound of formula (IV. Pure);

(d) contacting the compound of formula (IV) or compound of formula (IV. Pure) with a compound of formula (V) in the presence of a coupling agent; in the absence of an additive; in a suitable solvent to obtain the compound of fonnula (VI); wherein 'Prot' is a nitrog

(IV) OR (IV. Pure)

(e) converting the compound of formula (VI) to the compound of formula (VII);

(f) contacting the compound of formula (VII) with a base in a suitable solvent to obtain compound of fonnula (I).

(VII) ⁽

(g) optionally, providing Eluxadoline of fonnula (I) in a ketone solvent and isolating crystalline form a of Eluxadoline.

The hydride source of step (a) includes metal hydride or hydrogen in the presence of a catalyst. In one aspect of the invention such a catalyst is a transition metal catalyst optionally in the form of a complex. In a preferable aspect, metal hydride is used as a hydride source. The metal hydride is selected from sodium borohydride, sodium triacetoxy borohydride, sodium cyanoborohydride, lithium cyanoborohydride, potassium borohydride, lithium borohydride, zinc borohydride, calcium borohydride, magnesium borohydride and zirconium borohydride.

The suitable solvent of step (a) is selected from the group of alcohol, ester, ether, formamide, hydrocarbon, sulfoxide, nitrile, water or mixtures thereof in a suitable proportion. The preferred alcohol is methanol, ethanol, isopropanol, 2-propanol, 1- butanol, t-butyl alcohol, 1-pentanol, 2-pentanol and amyl alcohol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred ether is methyl tert-butyl ether, ethyl tert-butyl ether, diethyl ether, dimethyl ether, isopropyl ether, dibutyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran (THF), dioxane, dimethoxyethane and diglyme; the preferred formamide is dimethylformamide; the preferred hydrocarbon is dichloromethane, ethylene dichloride, cyclohexane, toluene and xylene; the preferred sulfoxide is dimethyl sulfoxide; the preferred nitrile is acetonitrile and water or mixtures thereof in a suitable proportion. The preferred alcohol of step (a) is methanol. The step (a) is carried out at a temperature of about 20°C to 50°C, preferably at about 25 °C to 45 °C.

In step (b) the acid is selected from inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid and organic acid such as citric acid, malic acid, succinic acid, p-toluene sulfonic acid, ethane sulfonic acid, methane sulfonic acid and the like in a suitable solvent.

In an aspect the compound of formula (IV.acid) is compound (S)-2-methoxy-5-(((l- (4-phenyl-lH-imidazol-2-yl) ethyl)amino)methyl)benzoate citric acid salt of formula:

The suitable solvent of step (b) is selected from the group of alcohol, ester and chlorinated hydrocarbon. The preferred alcohol is methanol, ethanol and isopropanol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred chlorinated hydrocarbon is dichloromethane and ethylene dichloride

The base of step (c) is selected from hydroxides of alkali and alkaline earth metals such as sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like.

The suitable solvent of step (c) is selected from the group of alcohol, ester and chlorinated hydrocarbon and mixtures thereof.

The compound of formula (IV) is optionally subjecting it to process steps (b) and (c) and may be used directly for the next step (d) as present in the reaction mixture,without isolation.

A compound of formula (VI) is prepared in step (d) by contacting compound of formula (IV) or compound of formula (IV. Pure) with a compound of formula (V) in the presence of a suitable coupling agent; in the absence of an additive; in a suitable solvent. The reaction of step (d) is carried out at a temperature of about 5°C to about 70°C, preferably at about 25°C to 40°C. The suitable coupling agent of step (d) is quinoline based coupling reagent such as l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ) and isobutyl 1, 2-dihydro-2- isobutoxy- 1 -quinolinecarboxylate (IIDQ) . The reaction of step (d) is carried out in a suitable solvent selected from the group of alcohols, amides, sulphoxides, pyrrolidones, esters, hydrocarbons, ketones, ethers, nitriles or mixtures thereof in a suitable proportion. The preferred alcohol is methanol, ethanol, isopropanol, butanol and iso-butanol; the preferred ester is ethyl acetate, methyl acetate, tertiarybutyl acetate and iso-propyl acetate; the preferred ketone is acetone, methylisobutyl ketone, methylethyl ketone, diethyl ketone and dimethyl ketone; the preferred hydrocarbon is toluene; the preferred ether is ethyl ether, methyl ether, diisopropylether, methyltertbutyl ether, dioxane and tetrahydrofuran the preferred amide is N,N-dimethylformamide, N-methyl acetamide and N,N-dimethylacetamide; the preferred sulfoxide is dimethylsulphoxide; the preferred pyrrolidone is N- methylpyrrolidone; the preferred hydrocarbon is 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, benzene and xylene; the preferred nitrile is acetonitrile or mixtures thereof in suitable proportions.

In step (e) the compound of formula (VI) is converted to compound of formula (VII) by conventional processes such as reduction, acid treatment and the like.

Acid treatment is done by contacting the compound of formula (VI) with organic or inorganic acids. The organic acid is selected form the group of carboxylic acid or sulphonic acid such as trifluoroacetic acid, trifluoromethane sulphonic acid, methane sulphonic acid, formic acid, tartaric acid and p-toluenesulphonic acid and the like. The inorganic acid is selected from the group of hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid and sodium hydrogen phosphate and the like. The said reaction is carried out at a temperature of about 50°C to 70°C, preferably at about 25°C to 50°C.

The reaction of step (e) is optionally carried out in the presence of an organic solvent. The organic solvent of step (e) is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof. Examples of suitable solvent includes but not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiary butyl acetate, isopropyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone, dimethyl ketone, methyl isobutyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutylether, cyclopentyl methyl ether, dioxane, tetrahydrofuran, N,N-dimethylformamide, N-methyl acetamide, N,N-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene, monoglyme, diglyme, diethoxy methane or mixtures thereof.

The compound of formula (I) is prepared in step (f) by contacting the compound of formula (VII) with an aqueous base in a suitable solvent. The said reaction is carried out at a temperature of about -10°C to 70°C, preferably at about 0°C to 45 °C.

The base used in step (f) is selected from the group of hydroxides of alkali and alkaline earth metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide, cesium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like. The suitable solvent of step (f) is selected from the group of alcohol such as methanol, ethanol, isopropanol and water or mixtures thereof. The preferred alcohol of step (e) is methanol.

In another embodiment, the invention provides a process for the preparation of Eluxadoline of formula (I) or pharmaceutically acceptable salts thereof; comprising the steps of: (a) contacting a compound of formula (II) with a compound of formula (Ilia) in the presence of metal hydride and a catalytic amount of acetic acid, to obtain the compound

(IVa)

(b) optionally, providing the compound of formula (IVa) and an acid in a suitable solvent to obtain the compound of formula (IVa.Acid);

(c) optionally, contacting the compound of formula (IVa.Acid) with a base in an organic solvent to

(IVa.Acid)

(d) contacting the compound of formula (IV) or compound of formula (IVa.Pure) with a compound of formula (Va) in the presence of a coupling agent; in the absence of an ad

(e) providing the compound of formula (Via) with an acid to obtain the compound of formula (Vila); and

(g) optionally, providing Eluxadoline of formula(I) in a ketone solvent and isolating crystalline form a of Eluxadoline. In step (a) the compound of formula (II) is reacted with a compound of formula

(Ilia) in the presence of a metal hydride and catalytic amount of acetic acid, in a suitable solvent; to obtain the compound of formula (IVa). The step (a) is carried out at a temperature of about 20°C to about 50°C, preferably at about 25°C to 45°C. The metal hydride of step (a) is selected from sodium borohydride, sodium triacetoxy borohydride, sodium cyanoborohydride, lithium cyanoborohydride, potassium borohydride, lithium borohydride, zinc borohydride, calcium borohydride, magnesium borohydride and zirconium borohydride. The preferred hydride of step (a) is sodium borohydride.

The suitable solvent of step (a) is selected from the group of alcohol, ester, ether, formamide, hydrocarbon, sulfoxide, nitrile, water or mixtures thereof in a suitable proportion. The preferred alcohol is methanol, ethanol, isopropanol, 2-propanol, 1- butanol, t-butyl alcohol, 1-pentanol, 2-pentanol and amyl alcohol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred ether is methyl tert-butyl ether, ethyl tert-butyl ether, diethyl ether, dimethyl ether, isopropyl ether, dibutyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran (THF), dioxane, dimethoxyethane and diglyme; the preferred formamide is dimethylformamide; the preferred hydrocarbon is dichloromethane, ethylene dichloride, cyclohexane, toluene and xylene; the preferred sulfoxide is dimethyl sulfoxide; the preferred nitrile is acetonitrile and water or mixtures thereof in a suitable proportion. The preferred alcohol of step (a) is methanol.

In step (b) the acid is selected from inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid and organic acid such as citric acid, malic acid, succinic acid, p-toluene sulfonic acid, ethane sulfonic acid, methane sulfonic acid and the like in a suitable solvent.

The suitable solvent of step (b) is selected from the group of alcohol, ester and chlorinated hydrocarbon. The preferred alcohol is methanol, ethanol and isopropanol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred chlorinated hydrocarbon is dichloromethane and ethylene dichloride

The base of step (c) is selected from hydroxides of alkali and alkaline earth metals such as sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like. The suitable solvent of step (c) is selected from the group of alcohol, ester and chlorinated hydrocarbon and mixtures thereof. The compound of formula (IVa) is optionally subjecting it to process steps (b) and

(c) and may be used directly for the next step (d) as present in the reaction mixture,without isolation.

A compound of formula (Via) is prepared in step (d) by contacting a compound of formula (IVa) or compound of formula (IVa.Pure) with a compound of formula (Va) in the presence of a suitable coupling agent; in the absence of an additive; in a suitable solvent. The reaction step (d) is done at a temperature of about 5°C to about 70°C, preferably at about 25°C to 40°C.

The suitable coupling agent of step (d) is quinoline based coupling reagent such as l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ) and isobutyl 1, 2-dihydro-2- isobutoxy- 1 -quinolinecarboxylate (IIDQ) .

The suitable solvent of step (d) is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof in any suitable proportion. Examples of suitable solvent includes but are not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiarybutyl acetate, iso-propyl acetate, acetone, methylisobutyl ketone, methylethyl ketone, diethyl ketone, dimethyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutyl ether, dioxane, tetrahydrofuran, N,N- dimethylformamide, N-methyl acetamide, Ν,Ν-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene or mixtures thereof in any suitable proportion. Preferably dichloromethane, dimethylformamide or mixtures thereof is the suitable solvent of step (d). In step (e) the compound of formula (Via) is contacted with an acid. The said reaction is carried out at a temperature of about 5°C to 70°C, preferably at about 25°C to 50°C. The reaction of step (e) is optionally carried out in the presence of an organic solvent.

The organic solvent of step (e) is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof. Examples of suitable solvent includes but not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiary butyl acetate, isopropyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone, dimethyl ketone, methyl isobutyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutylether, cyclopentyl methyl ether, dioxane, tetrahydroiuran, N,N-dimethylformamide, N-methyl acetamide, N,N-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene, monoglyme, diglyme, diethoxy methane or mixtures thereof. Preferably THF is used as suitable solvent. The acid of step (e) is selected from organic and inorganic acid. The organic acid is selected form carboxylic acid or sulphonic acid such as trifluoroacetic acid, trifluoromethane sulphonic acid, methane sulphonic acid, formic acid, tartaric acid and p- toluene sulphonic acid. The inorganic acid is selected from hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid and sodium hydrogen phosphate. The preferred acid of step (e) is hydrochloric acid.

The compound of formula (I) is prepared in step (f) by contacting the compound of formula (Vila) with an aqueous base in a suitable solvent. The said reaction is carried out at temperature of about -10°C to 70°C, preferably at about 0°C to 45 °C.

The base used in step (f) is selected from the group of hydroxides of alkali and alkaline metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide, cesium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like. Preferably sodium hydroxide may be used as base.

Suitable solvents that can be used in the step (f) include but are not limited to alcoholic solvents such as methanol, ethanol, isopropanol preferably methanol and the like; water and mixtures thereof. In yet another embodiment, the invention provides a process for the preparation of

Eluxadoline of formula (I) or pharmaceutically acceptable salts thereof; comprising the steps of:

(a) providing the compound of formula (IV) and an acid in a suitable solvent to obtain the compound of formula (IV. Acid);

(b) contacting the compound of formula (IV .Acid) with a base in a suitable solvent to obtain compound of formula (IV. Pure);

(IV.Acid) (c) contacting the compound of formula (IV. Pure) with a compound of formula (V) in the presence of a coupling agent; in the absence of an additive; in a suitable solvent to obtain the compound of formula (VI); wherein 'Prot' is a nitrogen protecting group;

(d) contacting the compound of formula (VI), wherein R ¹ is lower alkyl or aryl alkyl and 'Prot' is a nitrogen protecting group with a base to obtain the compound of formula (VIII); and

(e) converting the compound of formula (VIII) to the compound of formula (I);

(f) optionally, providing Eluxadoline of formula(I) in a ketone solvent and isolating crystalline form a of Eluxadoline.

In step (a) the suitable acid is selected from inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid and organic acid such as citric acid, malic acid, succinic acid, p-toluene sulfonic acid, ethane sulfonic acid, methane sulfonic acid and the like in a suitable solvent.

The suitable solvent of step (a) is selected from the group of alcohol, ester and chlorinated hydrocarbon. The preferred alcohol is methanol, ethanol and isopropanol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred chlorinated hydrocarbon is dichloromethane and ethylene dichloride. The base of step (b) is selected from hydroxides of alkali and alkaline earth metals such as sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like.

The suitable solvent of step (b) is selected from the group of alcohol, ester and chlorinated hydrocarbon and mixtures thereof.

The compound of formula (IV) may be used as such; optionally subjecting it to process steps (a) and (b).

The compound of formula (IV. Pure) is contacted with the compound of formula (VI) in step (c) in the presence of a suitable coupling agent; in the absence of additive; in a suitable solvent as described hereinabove.

The compound of formula (VIII) is prepared in step (d) by treating the compound of formula (VI) with an aqueous base in a suitable solvent. The said reaction is carried out at a temperature of about -10°C to 70°C, preferably at a temperature of about 0°C to 50°C.

The base used in step (d) is selected from the group of hydroxides of alkali and alkaline metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide, rubidium hydroxide, cesium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like.

The suitable solvents of step (d) includes but is not limited to alcoholic solvents such as methanol, ethanol, isopropanol preferably methanol and the like; water and mixtures thereof. The compound of formula (I) is prepared in step (e) by subjecting compound of formula (VIII) to conventional processes such as reduction, acid treatment and like. Acid treatment is carried out by treating the compound of formula (VIII) with organic or inorganic acids. The organic acid is selected form carboxylic acid or sulphonic acid such as trifluoroacetic acid, trifluoromethane sulphonic acid, methane sulphonic acid, formic acid, tartaric acid, p-toluenesulphonic acid and the like. The inorganic acid is selected from hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid, sodium hydrogen phosphate and the like. The said reaction is carried out at a temperature of about 50°C to 70°C, preferably at about 25°C to 50°C. The reaction of step (e) is carried out in the absence or presence of a suitable organic solvent which is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof. Examples of suitable solvent includes but not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiary butyl acetate, isopropyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone, dimethyl ketone, methyl isobutyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutylether, cyclopentyl methyl ether, dioxane, tetrahydrofuran, N,N- dimethylformamide, N-methyl acetamide, Ν,Ν-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene, monoglyme, diglyme, diethoxy methane or mixtures thereof. The compound of formula (I) prepared in step (e) is isolated at a pH range of about 5 to 11, more preferably at a pH range of about 6 to 7. The pH is adjusted using organic or inorganic acids. The organic acid is selected form the group of carboxylic acid such as citric acid, tartaric acid, malic acid and the like. The inorganic acid is selected from the group of hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid and sodium hydrogen phosphate and the like. The said pH adjustment is carried out at a temperature of about 10°C to 50°C, preferably at about 20°C to 40°C.

In a further embodiment the present invention provides process for preparation of intermediate of Eluxadoline, compound of formula (VI) comprising reacting compound of formula (IV) or compound of formula (IV. Pure) with a compound of formula (V) in the presence of a suitable coupling agent; in the absence of an additive; in a suitable solvent.

The suitable coupling agent is quinoline based coupling reagent such as quinoline based coupling agent, l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ) and isobutyl 1, 2-dihydro-2-isobutoxy-l-quinolinecarboxylate (IIDQ).

In yet another embodiment, the invention provides a process for the preparation of Eluxadoline of formula (I) or pharmaceutically acceptable salts thereof; comprising the steps of:

(a) contacting a compound of formula (II) with a compound of formula (Ilia) in the presence of metal hydride and a catalytic amount of acetic acid, to obtain the compound of formula (IVa);

(b) optionally, providing the compound of formula (IVa) and an acid in a suitable solvent to obtain the compound of formula (IVa.Acid);

(IVa) (IVa.Acid)

(c) optionally, contacting the compound of formula (IVa.Acid) with a base in an organic solvent to obtain compound of formula (IVa.Pure);

(IVa.Acid)

(d) contacting the compound of formula (IV) or compound of formula (IVa.Pure) with a compound of formula (Va) in the presence of a coupling agent; in the absence of an additive; in a suitable solvent to obtain the compound of formula (Via);

(e) contacting the compound of formula (Via), wherein 'Prot' is a nitrogen protectin group with a base to obtain the compound of formula (VIII); and

(f) converting the compound of formula (VIII) to the compound of formula (I);

(g) optionally, providing Eluxadoline of formula(I) in a ketone solvent and isolating crystalline form a of Eluxadoline.

In step (a) the compound of formula (II) is reacted with a compound of formula (Ilia) in the presence of a metal hydride and catalytic amount of acetic acid, in a suitable solvent; to obtain the compound of formula (IVa). The step (a) is carried out at a temperature of about 20°C to about 50°C, preferably at about 25°C to 45°C.

The metal hydride of step (a) is selected from sodium borohydride, sodium triacetoxy borohydride, sodium cyanoborohydride, lithium cyanoborohydride, potassium borohydride, lithium borohydride, zinc borohydride, calcium borohydride, magnesium borohydride and zirconium borohydride. The preferred hydride of step (a) is sodium borohydride.

The suitable solvent of step (a) is selected from the group of alcohol, ester, ether, formamide, hydrocarbon, sulfoxide, nitrile, water or mixtures thereof in a suitable proportion. The preferred alcohol is methanol, ethanol, isopropanol, 2-propanol, 1- butanol, t-butyl alcohol, 1-pentanol, 2-pentanol and amyl alcohol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred ether is methyl tert-butyl ether, ethyl tert-butyl ether, diethyl ether, dimethyl ether, isopropyl ether, dibutyl ether, tert-butyl methyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran (THF), dioxane, dimethoxyethane and diglyme; the preferred formamide is dimethylformamide; the preferred hydrocarbon is dichloromethane, ethylene dichloride, cyclohexane, toluene and xylene; the preferred sulfoxide is dimethyl sulfoxide; the preferred nitrile is acetonitrile and water or mixtures thereof in a suitable proportion. The preferred alcohol of step (a) is methanol. In step (b) the acid is selected from inorganic acid such as hydrochloric acid, sulfuric acid or phosphoric acid and organic acid such as citric acid, malic acid, succinic acid, p-toluene sulfonic acid, ethane sulfonic acid, methane sulfonic acid and the like in a suitable solvent.

The suitable solvent of step (b) is selected from the group of alcohol, ester and chlorinated hydrocarbon. The preferred alcohol is methanol, ethanol and isopropanol; the preferred ester is ethyl acetate, propyl acetate, isopropyl acetate, t-butyl acetate and isobutyl acetate; the preferred chlorinated hydrocarbon is dichloromethane and ethylene dichloride.

The base of step (c) is selected from hydroxides of alkali and alkaline earth metals such as sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like.

The suitable solvent of step (c) is selected from the group of alcohol, ester and chlorinated hydrocarbon and mixtures thereof.

The compound of formula (IVa) may be used as such without isolation in step (d) and optionally subjecting it to process steps (b) and (c). A compound of formula (Via) is prepared in step (d) by contacting a compound of formula (IVa) or compound of formula (IVa.Pure) with a compound of formula (Va) in the presence of a suitable coupling agent; in the absence of an additive; in a suitable solvent. The reaction step (d) is done at a temperature of about 5°C to about 70°C, preferably at about 25°C to 40°C. The suitable coupling agent of step (d) is quinoline based coupling reagent such as l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (EEDQ) and isobutyl 1, 2-dihydro-2- isobutoxy- 1 -quinolinecarboxylate (IIDQ) . The suitable solvent of step (d) is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof in any suitable proportion. Examples of suitable solvent includes but are not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiarybutyl acetate, iso-propyl acetate, acetone, methylisobutyl ketone, methylethyl ketone, diethyl ketone, dimethyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutyl ether, dioxane, tetrahydrofuran, N,N- dimethylformamide, N-methyl acetamide, Ν,Ν-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1,1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene or mixtures thereof in any suitable proportion. Preferably dichloromethane, dimethylformamide or mixtures thereof is the suitable solvent of step (d).

The compound of formula (VIII) is prepared in step (e) by treating the compound of formula (Via) with an aqueous base in a suitable solvent. The said reaction is carried out at a temperature of about -10°C to 70°C, preferably at a temperature of about 0°C to 50°C.

The base used in step (e) is selected from the group of hydroxides of alkali and alkaline metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide, rubidium hydroxide, cesium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like. The suitable solvents of step (e) includes but is not limited to alcoholic solvents such as methanol, ethanol, isopropanol preferably methanol and the like; water and mixtures thereof. The compound of formula (I) is prepared in step (f) by subjecting compound of formula (VIII) to conventional processes such as reduction, acid treatment and like. Acid treatment is carried out by treating the compound of formula (VIII) with organic or inorganic acids. The organic acid is selected form carboxylic acid or sulphonic acid such as trifluoroacetic acid, trifluoromethane sulphonic acid, methane sulphonic acid, formic acid, tartaric acid, p-toluenesulphonic acid and the like. The inorganic acid is selected from hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid, sodium hydrogen phosphate and the like. The said reaction is carried out at a temperature of about 50°C to 70°C, preferably at about 25°C to 50°C.

The reaction of step (f) is carried out in the absence or presence of a suitable organic solvent which is selected from the group of alcohols, amides, sulphoxides, pyrrolidones, ethers, hydrocarbons, ketones, esters, nitriles or mixtures thereof. Examples of suitable solvent includes but not limited to methanol, ethanol, isopropanol, butanol, iso-butanol, ethyl acetate, methyl acetate, tertiary butyl acetate, isopropyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, diethyl ketone, dimethyl ketone, methyl isobutyl ketone, toluene, ethyl ether, methyl ether, diisopropylether, methyltertbutylether, cyclopentyl methyl ether, dioxane, tetrahydrofuran, 2-methyl tetrahydrofuran, N,N-dimethylformamide, N-methyl acetamide, N,N-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidone 1, 1-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, acetonitrile, benzene, xylene, monoglyme, diglyme, diethoxy methane or mixtures thereof. The compound of formula (I) prepared in step (e) is isolated at a pH range of about 5 to 1 1, more preferably at a pH range of about 6 to 7. The pH is adjusted using organic or inorganic acids and/or inorganic bases. The organic acid is selected form the group of carboxylic acid such as citric acid, tartaric acid, malic acid and the like. The inorganic acid is selected from the group of hydrochloric acid, hydrobromic acid, sulphuric acid, phosphoric acid and sodium hydrogen phosphate and the like. The inorganic base is selected from the group of hydroxides of alkali and alkaline metals such as lithium hydroxide, sodium hydroxide, potassium hydroxide calcium hydroxide, ammonium hydroxide, rubidium hydroxide, cesium hydroxide and the like; carbonates of alkali and alkaline metals such as sodium carbonate, potassium carbonate and the like; and bicarbonates of alkali and alkaline metals such as sodium bicarbonate, potassium bicarbonate and the like.

The said pH adjustment is carried out at a temperature of about 10°C to 50°C, preferably at about 20°C to 40°C.

In yet another aspect, the present invention provides pharmaceutical composition comprising of Eluxadoline and crystalline form a of Eluxadoline prepared by the processes of the present invention with one or more pharmaceutically acceptable excipients and their use in the treatment of disorders that may be ameliorated or treated by the modulation of opioid receptors.

One skilled in the art will recognize that additional starting compounds and/or reagents are commercially available or may be easily prepared according to conventional methods well known to these skilled in the art.

The present invention is further illustrated with the following non-limiting examples.

EXAMPLES

Example 1: Preparation of Eluxadoline

Step 1- Preparation of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6-dimethyl - phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid methyl ester

To a stirred solution of 1 -(4-phenyl- lH-imidazole-2-yl)-ethyl amine (95 gm) and 5- formyl-2-methoxy-benzoic acid methyl ester (100 gm) in methanol (250 ml) was added catalytic amount of acetic acid (1 ml). The reaction mixture was cooled at -10 to 10°C and sodium borohydride (9.7 gm) was added. The reaction mixture was further stirred for 2-3 hours at room temperature. The resultant mixture was diluted with water and dichloromethane. The organic phases were separated and further partially concentrated under vacuum to obtain 2-methoxy-5-{[l-(4-phenyl-lH-imidazol-2-yl)ethylamino]- methyl)benzoic acid methyl ester; which was further added into the mixture of 2-tert- butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl-phenyl-propi onic acid (138 gm), 1- ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HC1, 277 gm) and 1- hydroxybenzotriazole (HOBt, 78.8 gm) in dimethylformamide (400 ml). Diisopropylethylamine (DIPEA) was further added and resultant mixture was further stirred for 3 to 4 hours at room temperature. The resultant mixture was diluted with water and dichloromethane. The separated organic phase was washed sequentially with aqueous NaOH solution, 10% HCl solution and water. The reaction mixture was cooled, filtered and further purified using methanol and ethyl acetate to afford titled compound (yield: 185 gm).

Step 2: Preparation of 5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)-propionyl] - [ 1 -(4-phenyl- 1 W-imidazol-2-yl)-ethyl] -amino } -methyl)-2-methoxy- benzoic acid.

Into an ice cooled solution of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6- dimethyl-phenyl)-propionyl]-[l-(4-phenyl-lH-imidazol-2-yl)-e thyl]-amino}-methyl)-2- methoxy-benzoic acid methyl ester (Step-1 product, 100 gm) in methanol (250 ml) and tetrahydrofuran (450 ml) was added an aqueous solution of lithium hydroxide (18.41 gm in 175 ml water). The resultant mixture was stirred at room temperature for overnight.

After completion of reaction, mixture was partially concentrated and further diluted with water. The pH (5-5.5) was adjusted using 20% citric acid and further stirred for 60 min.

The solid precipitated was filtered, washed with water and dried to obtain titled compound (yield: 85 gm).

Step 3: Preparation of Eluxadoline 5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)- propionyl]-[l-(4-phenyl-lH-imidazol-2-yl)-emyl]-amino}-methy l)-2-methoxy-benzoic acid (Step-2 product, 100 gm) was added into ice cooled solution of IPA.HC1 (650 ml). The reaction mixture was stirred at room temperature for 24 hours. After completion of reaction, the resultant residue was added into water. The pH (6-7) was adjusted using IN NaOH solution and the precipitated was filtered, washed with water and dried to obtain titled compound, (yield: 75 gm).

Example 2: Preparation of crystalline form a of Eluxadoline

Eluxadoline (5 gm) was suspended in acetone (50 ml) and resultant reaction mixture was heated at 50 to 55 °C and further stirred for 20 hours. The mixture was cooled to room temperature and solid precipitate was filtered and further dried to obtain a crystal of Eluxadoline (yield: 4.8 gm). Example 3: Preparation of crystalline form a of Eluxadoline

Eluxadoline (100 gm) was suspended in acetone (950 ml) and resultant reaction mixture was heated at 50 to 55 °C and further seeded with crystalline form a of Eluxadoline. The mixture was stirred at same temperature for 26 hours. The mixture was cooled to room temperature and solid precipitate was filtered, washed with acetone and further dried to obtain 75 gm of crystalline form a of Eluxadoline.

Example 4: Preparation of crystalline form a of Eluxadoline

To a mixture of acetone (270 ml) and water (180 ml) cooled to 20 to 25 °C was added Eluxadoline (100 gm) in lots of 20 gm each. Gradually allowed the reaction mixture to attain room temperature and stirred for 15 to 30 min followed by addition of seed of crystalline form a of Eluxadoline (0.01 gm). The reaction mixture was heated to 30 to 35 °C, stirred for 1 to 2 hrs, cooled to room temperature, filtered, washed with acetone and dried to afford 90 gm of crystalline form a of Eluxadoline. Example 5: Preparation of Eluxadoline

Step 1: Preparation of methyl (S)-2-methoxy-5-(((l-(4-phenyl-lH-imidazol-2-yl) ethyl) amino)methyl)benzoate

To a stirred solution of l-(4-phenyl-lH-imidazole-2-yl)-ethyl amine (95 gm) and 5- formyl-2-methoxy-benzoic acid methyl ester (100 gm) in methanol (250 ml) was added catalytic amount of acetic acid (1 ml). The reaction mixture was cooled at 5°C-10°C and sodium borohydride (9.74 gm) was added. The reaction mixture was further stirred for 2- 3 hours at room temperature followed by addition of dichloromethane (500 ml) and water (500 ml). The phases were separated and the dichloromethane layer was washed with water (500 ml). The dichloromethane layer (~ 600 ml) containing (S)-2-methoxy-5-(((l- (4-phenyl-lH-imidazol-2-yl)ethyl)amino)methyl)benzoate was preserved to be used in Step 2.

Step 2: Preparation of (S)-2-methoxy-5-(((l -(4-phenyl- lH-imidazol -2- citric acid salt

To citric acid monohydrate (98.79 gm) taken in methanol (200 ml), dichloromethane solution of (S)-2-methoxy-5 -((( 1 -(4-phenyl- lH-imidazol-2- yl)ethyl)amino)methyl)benzoate (-600 ml) obtained in step- 1 was added and stirred for 12-14 hrs. Filtered the solid and dried under vacuum to afford 245 gm of the title compound.

Step 3: Preparation of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6-dimethyl - phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid methyl ester

To a stirring mixture of 2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl -propionic acid (138.48 gm), l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (152.56 gm) in dimethyl formamide (250 ml) at 0-5°C was added a solution of (S)-2- methoxy-5 -((( 1 -(4-phenyl- lH-imidazol-2-yl)ethyl)amino)methyl)benzoate in dichloromethane [the solution of (S)-2-methoxy-5-(((l-(4-phenyl-lH-imidazol-2- yl)ethyl)amino)methyl)benzoate in dichloromethane was obtained by adding dichloromethane (100 ml) and water (100 ml) to (S)-2-methoxy-5-(((l -(4-phenyl- 1H- imidazol-2-yl)ethyl)amino)methyl)benzoate citric acid salt (245 gm obtained in step 2) followed by addition of 8% aqueous sodium hydroxide solution (750 ml) at room temperature, stirring and separating the dichloromethane followed by volume reduction to ~ 4.0 volumes] in 1 hrs. The reaction mixture was stirred for 4hrs at 0-5°C, then the temperature was raised to 15-18 °C and stirring was continued for 20 hrs. Thereafter dichloromethane (500 ml) and water (500 ml) were added to the reaction mixture and stirred and settled. The phases were separated. The organic layer was washed with 5% aqueous sodium hydroxide (500 ml), cooled to 0-5°C and added dil. hydrochloric acid (1000 ml) gradually and stirred the reaction mixture for 3 hrs., filtered and dried under vacuum to afford 256.89 gm of the title compound.

Step 4: Preparation of methyl 5-((2-amino-3-(4-carbamoyl-2,6-dimethylphenyl)-N-(l-(4- phenyl- anamido)methyl)-2-methoxybenzoate

To a stirred solution of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6-dimethyl - phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid methyl ester (20 gm) in THF (80 ml) was added Cone. HC1 solution (30 ml). The reaction mixture was heated at 40°C-45°C. After completion of reaction, the mixture was concentrated and resultant residue was diluted with water. The pH (9-10) was adjusted using 3N NaOH solution; and the resultant sticky mass was dissolved in methanol. The resultant solution was concentrated under vacuum to afford 18.1 gm of the title compound.

Step 5: Preparation of Eluxadoline

To an ice cooled solution of methyl 5-((2-amino-3-(4-carbamoyl-2,6-dimethylphenyl)-N- ( 1 -(4-phenyl- lH-imidazol-2-yl)ethyl)propanamido)methyl)-2-methoxybenzoate (15 gm) in methanol was added an aqueous lithium hydroxide (3.23 gm in 30 ml water) and the resultant mixture was heated at 40°C-45°C. After completion of reaction, mixture was concentrated and further diluted with water. The pH (6-7) was adjusted using 2N citric acid and resultant residue was dissolved in methanol. The resultant solution was added slowly to the acetone and stirring was continued for overnight. The solid precipitated was filtered, washed with acetone and dried to obtain 3.5 gm of the title compound.

Example 6: Preparation of Eluxadoline

Step 1: Preparation of 5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid

To an ice cooled solution of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6- dimethyl-phenyl)-propionyl]-[l-(4-phenyl-lH-imidazol-2-yl)-e thyl]-amino}-methyl)-2- methoxy-benzoic acid methyl ester (85 gm) in methanol (225 ml) and 2-methyl tetrahydrofuran (425 ml) was added an aqueous solution of lithium hydroxide (20.89 gm in 150 ml water) and the resultant reaction mixture was stirred at room temperature for overnight. After completion of reaction, the reaction mixture was partially concentrated and diluted with water (500 ml). The reaction mixture was cooled to 10°C -15°C. Thereafter the pH of the reaction mixture was adjusted to 5 to 6 with 20% aqueous citric acid solution and further stirred for 60 min. The precipitated solid was filtered, washed with water and dried under vacuum to afford 140 gm of the title compound. Step 2: Preparation of Eluxadoline

5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)-propionyl]-[l-(4- phenyl-lH-imidazol-2-yl)-ethyl]-amino}-methyl)-2-methoxy-ben zoic acid (70 gm) was added to a solution of acetonitrile (250 ml) and Cone. HC1 (105 ml) under stirring. Thereafter the reaction mixture was stirred for 5hrs at room temperature. The slurry was filtered (wet cake 75 gm) and contacted with water (560 ml). The reaction mixture was stirred and filtered through micron filter. The resultant filtrate was gradually added to a cooled solution of IN sodium hydroxide (280 ml). Raised the temperature stirred for 2 hrs, filtered and dried under vacuum to afford 102 gm of title compound.

Example-7: Preparation of (S)-2-methoxy-5-(((l-(4-phenyl-lH-imidazol-2- yl)ethyl)amino)methyl)benzoate hydrochloric acid salt

To a stirred solution of l-(4-phenyl-lH-imidazole-2-yl)-ethyl amine (95 gm) and 5- formyl-2-methoxy-benzoic acid methyl ester (100 gm) in methanol (250 ml) was added catalytic amount of acetic acid (1 ml). The reaction mixture was cooled at 5°C-10°C and sodium borohydride (9.74 gm) was added. The reaction mixture was further stirred for 2- 3 hours at room temperature followed by addition of dichloromethane (500 ml) and water (500 ml). The phases were separated and the dichloromethane layer was washed with water (500 ml). To the dichloromethane layer (~ 600 ml) containing (S)-2-methoxy-5- (((l-(4-phenyl-lH-imidazol-2-yl) ethyl)amino)methyl)benzoate added ethyl acetate (1000 ml). Raised the temperature of the reaction mixture to 35 °C to 40 °C, added ethylacetate. HC1 (250 ml) and stirred for 1 hr. Further raised the temperature of the reaction mixture to 45 °C to 55 °C stirred for 1 hr, cooled to room temperature and stirred overnight. Filtered and dried under vacuum to afford 188.2 gm of the tile compound. Example-8: Preparation of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6- dimethyl-phenyl)-propionyl]-[l-(4-phenyl-lH-imidazol-2-yl)-e thyl]-amino}-methyl)- ester

To a stirring mixture of 2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl -propionic acid (156 gm), l-ethoxycarbonyl-2-ethoxy- l, 2-dihydroquinoline ( 152.8 gm) in dimethyl formamide (300 ml) at 0-5°C was added a solution of (S)-2-methoxy-5- (((l-(4-phenyl-lH-imidazol-2-yl)ethyl)amino)methyl)benzoate in dichloromethane [the solution of (S)-2-methoxy-5-(((l-(4-phenyl- lH-imidazol-2- yl)ethyl)amino)methyl)benzoate in dichloromethane was obtained by adding dichloromethane (100 ml) and water (100 ml) to (S)-2-methoxy-5-((( l-(4-phenyl-lH- imidazol-2-yl)ethyl)amino)methyl)benzoate hydrochloric acid salt (180 gm obtained in Example 4) followed by addition of 5% aqueous sodium hydroxide solution (500 ml) at 10°C to 15°C, stirring and separating the dichloromethane layer] in 1 hr. The reaction mixture was stirred for 4hrs at 0-5°C, then the temperature was raised to 15-18 °C and stirring was continued for 20 hrs. Thereafter dichloromethane (500 ml) and water (500 ml) were added to the reaction mixture and stirred and settled. The phases were separated. The organic layer was washed with 2% aqueous sodium hydroxide (500 ml), cooled to 0- 5°C and added dil. hydrochloric acid ( 1000 ml) gradually and stirred the reaction mixture for 3 hrs., filtered and dried under vacuum to afford 284.9 gm of the title compound.

Example 9: Preparation of Eluxadoline

Step-1 Preparation of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6-dimethyl - phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid methyl ester

To a stirred solution of l-(4-phenyl-lH-imidazole-2-yl)-ethyl amine (92 gm) and 5- formyl-2-methoxy-benzoic acid methyl ester (100 gm) in methanol (250 ml) was added catalytic amount of acetic acid (1 ml). The reaction mixture was cooled at -5°C-10°C and sodium borohydride (9.74 gm) was added. The reaction mixture was further stirred for 2- 4 hours at room temperature followed by addition of dichloromethane (500 ml) and water (500 ml). The phases were separated and the dichloromethane layer was washed with water (500 ml). The dichloromethane layer (~ 600 ml) containing (S)-2-methoxy-5-(((l- (4-phenyl-lH-imidazol-2-yl)ethyl)amino)methyl)benzoate was distilled to reduce volume to 2 to 2.5 volumes of the input batch size and diluted with dimethylformamide (100ml). The solution of (S)-2-methoxy-5-(((l-(4-phenyl-lH-imidazol-2- yl)ethyl)amino)methyl)benzoate thus obtained was added gradually to a stirring mixture of 2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl-pheny l-propionic acid (156 gm) and l-ethoxycarbonyl-2-ethoxy-l, 2-dihydroquinoline (153 gm) in dimethyl formamide (350 ml) at 0-5°C The reaction mixture was stirred for 0.5 to lhr at 0-5°C, then the temperature was raised to 15-20 °C and stirring was continued for 12 to 18 hrs. The reaction mixture was quenched into dilute hydrochloric acid solution (2000 ml) at 25-30 °C. The quenched reaction mixture was cooled to 10-15 °C and stirred for 1 to 2 hrs, filtered and washed with dichloromethane followed by water. The solid obtained was purified by dissolving in methanol and precipitating with ethylacetate and dried under vacuum to afford 250 gm of title compound.

Step-2 Preparation of 5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)-propionyl] - [ 1 -(4-phenyl- lH-imidazol-2-yl)-ethyl] -amino} -methyl)-2-methoxy- benzoic acid

To an ice cooled solution of 5-({[2-tert-butoxycarbonylmethyl-3-(4-carbamoyl-2,6- dimethyl-phenyl)-propionyl]-[l-(4-phenyl-lH-imidazol-2-yl)-e thyl]-amino}-methyl)-2- methoxy-benzoic acid methyl ester (100 gm) in methanol (500 ml) and tetrahydrofuran (800 ml) was added an aqueous solution of lithium hydroxide (10 ml; prepared by dissolving 28.5 gm LiOH in 240 ml water) and the resultant reaction mixture was stirred at 15-20°C for 14-22 hrs. After completion of reaction, the reaction mixture was diluted with water (300 ml) and the pH of the reaction mixture was adjusted to 7.5 to 8 with 20% aqueous citric acid solution. Reduced the volume of reaction mixture till -8-10 volume of reaction mixture is left with respect to input. Thereafter water (450 ml) is added gradually at 45-50°C and stirred for 1 hr followed by stirring for 1 hr at 25-30°C, filtered washed with water and dried the solid to afford 85 gm of title compound.

Step-3 Preparation of Eluxadoline

5-({[2-tert-butoxycarbonylamino-3-(4-carbamoyl-2,6-dimethyl- phenyl)-propionyl]-[l-(4- phenyl-lH-imidazol-2-yl)-ethyl]-amino}-methyl)-2-methoxy-ben zoic acid (100 gm) was added to a solution of acetonitrile (350 ml) and Cone. HC1 (150 ml) under stirring at room temperature. Thereafter the reaction mixture was stirred for 5-8 hrs at room temperature, filtered and washed with acetonitrile (200 ml) under inert atmosphere. The wet cake was added to water (900 ml), stirred and filtered through micron filter. The resultant filtrate was gradually added to a cooled solution of IN sodium hydroxide (380 ml) at 10-15°C maintaining the pH at 6.5 to 7 (adjusted using IN NaOH or IN HC1). Raised the temperature to 25-30°C and stirred for 2-3 hrs, filtered, washed with water (500 ml) followed by cyclohexane (200 ml). The wet cake was slurried with water and dried under vacuum to afford 65 gm of title compound.