WO2017021904A1 - Daclatasvir free base and process for the preparation thereof - Google Patents

Abstract

The present invention relates to daclatasvir free base, processes for its preparation, a process for its conversion into pharmaceutically acceptable salts of daclatasvir. The present invention also relates to a process for the preparation and purification of daclatasvir dihydrochloride.

Description

"DACLATASVIR FREE BASE AND PROCESS FOR THE PREPARATION THEREOF"

PRIORITY This application claims the benefit under Indian Provisional Application No. 4010/CHE/2015 filed on 03 Aug, 2015 entitled "Daclatasvir free base and process for the preparation thereof, the contents of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention generally relates to daclatasvir free base, substantially in a solid amorphous form, processes for its preparation, a process for its conversion into pharmaceutically acceptable salts of daclatasvir, and pharmaceutical compositions containing the same.

The present invention also relates to an improved process for the preparation of daclatasvir dihydrochloride and an improved process for the preparation of daclatasvir intermediates. BACKGROUND OF THE INVENTION

Daclatasvir, also known as methyl((lS)-l-(((2S)-2-(5-(4'-(2-((2S)-l-((2S)-2-((methoxy carbon yl)amino)-3-methylbutanoyl)-2-pyrrolidinyl)-lH-imidazol-5-yl)-4-biphenylyl)- lH-imidazol-2-yl)-l-pyrrolidinyl)carbonyl)-2-methyl-propyl)carbamate of Formula I:

Formula I

Daclatasvir is marketed as its dihydrochloride salt by Bristol-Myers Squibb Pharma under the trade name Daklinza^® for the treatment of Chronic Hepatitis C.

U.S. Patent No. 8,329,159 ("the Ί59 patent") discloses daclatasvir and its process for preparation thereof. The process disclosed in the ' 159 patent is schematically represented as follows:

According to the Ί59 patent, daclatasvir is isolated as its dihydrochloride salt. The free base of daclatasvir was not isolated, but was converted directly into the dihydrochloride salt of daclatasvir. The final saltification step involves reaction of ethanolic solution of daclatasvir free base with ethanolic HCl to obtain crude daclatasvir dihydrochloride salt compound, which was recrystallized from a mixture of methanol and acetone.

CN publication No.(S) 105622583 ("the '583 publication") & 105461701 ("the '701 publication") discloses a process for preparation of daclatasvir. The process disclosed in the '583 & '701 publications is schematically represented as follows: atasvir dihydrochloride

PCT publication No. 2016/079697 ("the '697 publication") discloses a process for preparation of daclatasvir intermediates. The process disclosed in the '697 publication is schematically represented as follows:

U.S. Patent No(s): 7,728,027("the '027 patent) & 8,629, 171 ("the ' 171 patent) are discloses similar process for the preparation of daclatasvir dihydrochloride. Further, the ' 171 patent discloses daclatasvir dihydrochloride polymorphic Form N-2, which is characterized by unit cell parameters, PXRD and melting point.

The ' 171 patent discloses preparation of Form N-2 from a set of solvents such as ethanol or a mixture of methanol and acetone with seeding. The ' 171 patent also discloses preparation of seed crystals from a mixture of isopropanol, ethanolic HC1 and methyl tert- butyl ether. The ' 171 patent discloses Form N-2 is having purity of 99% weight with differential scanning calorimetry onset temperature typically in the range of 225 -245 °C.

According to EMEA assessment report two neat crystalline daclatasvir dihydrochloride salts, Form N-l and Form N-2 have been identified in screening studies, it has been confirmed that the Form N-2 is the thermodynamically stable polymorph and only this form produced by the proposed synthetic process.

PCT publication No. 2015/109445 ("the '445 publication") discloses crystalline daclatasvir salts such as di 4-methyl benzenesulfonate, diphenyl sulfonate, citrate, glycolate, dimandelate, dichlorobenzene sulfonate, diethylene sulfonate, di a- keto glutarate, di 1,5-naphthalene sulfonate, 2-naphthalenesulfonate and tri hydrochloride salts.

The present invention provides daclatasvir free base substantially in a solid amorphous form, improved process for the preparation of daclatasvir dihydrochloride and its intermediates, which is readily amenable to large scale production with greater yield, and higher purity.

SUMMARY OF THE INVENTION In one aspect, there is provided a solid daclatasvir free base of Formula I:

Formula I

In one general aspect, there is provided an amorphous form of daclatasvir free base of Formula I.

In another general aspect, the amorphous form of daclatasvir free base has the X-ray powder diffraction pattern substantially as depicted in Fig.1.

In another general aspect, there is provided a process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a solvent; and

b) isolating amorphous form of daclatasvir free base.

In another general aspect, there is provided a process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a suitable solvent selected from the group consisting of ketones, esters, ethers, alcohols, nitriles, amides, sulfoxides, halogenated hydrocarbons, aromatic hydrocarbon solvent, water and mixture thereof; and

b) removing the solvent from step a) solution to obtain amorphous form of daclatasvir free base.

In another general aspect, there is provided an amorphous form of daclatasvir free base having a HPLC purity of about 98% or more, of about 99% or more, of about 99.5% or more as determined by high performance liquid chromatography (HPLC).

In another general aspect, there is provided a process for preparation of pharmaceutically acceptable salt of daclatasvir, the process comprising:

a) providing a solution of solid daclatasvir free base in a suitable organic solvent, b) adding a suitable acid to the reaction solution, and

c) isolating the daclatasvir pharmaceutically acceptable salt.

In another general aspect, there is provided a process for preparation of daclatasvir dihydrochloride, the process comprising:

a) providing a solution of solid daclatasvir free base in a suitable organic solvent, b) adding hydrochloric acid to the reaction solution, and

c) isolating the daclatasvir dihydrochloride salt. In another general aspect, there is provided a process for the purification of daclatasvir dihydrochloride, the process comprising:

a) providing a solution of daclatasvir dihydrochloride in a mixture of organic solvents selected from the group consisting of alcohols, ester and mixture thereof, b) optionally adding seed to the reaction solution, and

c) isolating the pure daclatasvir dihydrochloride; wherein the alcohls are selected from the group comprising methanol, ethanol, isopropanol, n-propanol, n- butanol, i- butanol, t-butanol and the like and mixtures thereof; and esters are selected from the group comprising methyl acetate, ethyl acetate, isopropyl acetate and the like; and mixtures thereof.

In another preferred general aspect, there is provided a process for the purification of daclatasvir dihydrochloride, the process comprising:

a) dissolving daclatasvir dihydrochloride in a first alcohol solvent,

b) optionally concentrating the step a) solution,

c) optionally cooling the step a) or b) solution to about 25 °C to about 35 °C, d) adding second alcohol solvent or ester solvnet to the step a) or b) or c) solution, e) optionally adding seed crystals to the step d) solution, and

f) isolating the pure daclatasvir dihydrochloride; wherein the first alcohol solvent is methanol, second alcohol solvent is selecetd from the group comprising ethanol, isopropanol, n-propanol, n-butanol, i-butanol, t-butanol and the like; and the ester solvnet is selecetd from the group comprising methyl acetate, ethyl acetate, isopropyl acetate and the like. In another general aspect, there is provided a daclatasvir dihydrochloride having a HPLC purity of about 99.5% or more as determined by high performance liquid chromatography (HPLC).

In another general aspect, there is provided a daclatasvir dihydrochloride having a HPLC purity of about 99.5% or more as determined by HPLC and contains less than about 0.1% as determined by HPLC of each of the impurity of Formula A, Formula C or Formula D.

In another general aspect, there is provided a daclatasvir dihydrochloride contains less than 0.1 % of impurity of Formula A as determined by HPLC.

In another general aspect, there is provided a daclatasvir dihydrochloride contains less than 0.1% of impurity of Formula B as determined by HPLC.

In another general aspect, there is provided a daclatasvir dihydrochloride contains less than 0.1 % of impurity of Formula C as determined by HPLC. In another general aspect, there is provided a daclatasvir dihydrochloride contains less than 0.1 % of impurity of Formula D as determined by HPLC.

In another general aspect, there is provided a daclatasvir dihydrochloride contains less than 0.1% as measured by HPLC of each of the impurity of Formula A, Formula B, Formula C or Formula D.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has a differential scanning calorimetry substantially as depicted in Fig. 3.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has the typical onset temperature of about 279°C by differential scanning calorimetry.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has the X-ray powder diffraction pattern substantially as depicted in Fig.4.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride, characterized by a differential scanning calorimetry substantially as depicted in Fig. 3 and X-ray powder diffraction pattern substantially as depicted in Fig.4.

In another general aspect, there is provided a process for the preparation of daclatasvir oxalate salt, the process comprising:

a) providing a solution of daclatasvir in a suitable solvent,

b) adding oxalic acid to the reaction solution, and

c) isolating the daclatasvir oxalate salt.

In another general aspect, there is provided a daclatasvir oxalate salt.

In another general aspect, the daclatasvir oxalate salt has the X-ray powder diffraction pattern substantially as depicted in Fig. 2.

In another general aspect, there is provided a process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof:

Formula I

comprising: a) reacting biphenyl of Formula III with a compound of Formula IV in presence of a suitable Lewis acid; wherein "X" represents halogen to obtain a compound of Formula V,

Formula III Formula IV CH FormulaC V b) reacting the compound of Formula V with a compound of Formula VI to obtain a compound of Formula VII; wherein "PG" represents a suitable protecting group,

Formula VI Formula VII c) cyclizing the compound of Formula VII to obtain a compound of Formula VIII,

Formula VIII

deprotecting the protecting group of Formula VIII with a suitable deprotecting agent to obtain a compound of Formula II or a pharmaceutically acceptable salt thereof, and

Formula II

converting the compound of Formula II or a pharmaceutically acceptable salt thereof in to daclatasvir or a pharmaceutically acceptable salt thereof. In another general aspect, there is provided a process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof, comprising: the above described step b) and step c) are carried out in a single solvent without isolating the compound of Formula VII. In another general aspect, there is provided a process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof, comprising: preparing the compound of Formula II or a pharmaceutically acceptable salt thereof according to the process as described above and converting the Formula II or a pharmaceutically acceptable salt thereof in to daclatasvir or a pharmaceutically acceptable salt thereof.

In another general aspect, there is provided a pharmaceutical composition comprosing daclatasvir free base together with one or more pharmaceutically acceptable excipients.

In another general aspect, there is provided a pharmaceutical composition comprosing daclatasvir dihydrochloride prepared by the processes described above, together with one or more pharmaceutically acceptable excipients. In another general aspect, there is provided a pharmaceutical composition comprosing a daclatasvir oxalate salt together with one or more pharmaceutically acceptable excipients.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.

Fig. 1 shows the powder X-ray diffractogram (PXRD) of the amorphous form of daclatasvir free base.

Fig. 2 shows the powder X-ray diffractogram (PXRD) of the daclatasvir oxalate salt.

Fig. 3 shows the differential scanning calorimetric (DSC) thermogram of the daclatasvir dihydrochloride as per example-8.

Fig. 4 shows the powder X-ray diffractogram (PXRD) of the daclatasvir dihydrochloride as per example-8. DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a solid daclatasvir free base and its process for preparation thereof. The present invention also relates to a process for purification of daclatasvir dihydrochloride.

The present invention further relates to an improved process for the preparation of daclatasvir intermediates or a pharmaceutically acceptable salt thereof.

In one general aspect, there is provided a solid daclatasvir free base of Formula I:

In another general aspect, there is provided an amorphous form of daclatasvir free base of Formula I. In another general aspect, the amorphous form of daclatasvir free base has the X-ray powder diffraction pattern substantially as depicted in Fig.1.

In another general aspect, there is provided a process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a solvent; and

b) isolating amorphous form of daclatasvir free base.

The step a) of providing a solution of daclatasvir includes, direct use of a reaction mixture containing daclataasvir that is obtained in the course of its synthesis; or dissolving daclatasvir in a solvent.

Any physical form of daclatasvir may be utilized for providing the solution of daclatasvir in step a). The dissolution temperature may range from about ambient to about reflux temperature of the solvent; preferably at about 40°C to about 80°C.

In an embodiment, daclatasvir can be dissolved in any suitable solvent. Suitable solvent include any solvent that have no adverse effect on the compound and can dissolve the starting material to a useful extent. Example of such solvents include, but are ot limited to: ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters, such as ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; ethers, such as tetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether or 1,4-dioxane; alcohols, such as methanol, ethanol, 2-methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles, such as acetonitrile or propionitrile; amides, such as formamide, N,N-dimethylformamide or N,N- dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene; water or any mixture of two or more thereof; preferably ethyl acetate or isopropyl ether. Step b) involves isolating amorphous Form of daclatasvir free base from the solution obtained in step a). Isolation of amorphous form of daclatasvir free base in step b) may involve method include removal of solvent, cooling, crash cooling, concentrating the mass, evaporation, flash evaporation, rotational drying, spray drying, agitated thin film drying, freeze-drying, adding anti-solvent, adding seed to include isolation, or the like. Stirring or other alternate methods such as shaking, agitation, or the like, may also be employed for the isoaltion; preferably amorphous Form of daclatasvir free base is isolated from step a) solution by cooling the reaction mass and the precipitated solid is recovered from the reaction mass by filtering the reaction mass.

Suitable temperature for isolation may be less than about 100°C, less than about 80°C, less than about 60°C, less than about 40°C, less than about 20°C, less than about 0°C, less than about -10°C or any oether suitable temperature; preferably less than about 40°C to about 20°C.

The recovered solid may optionally be dried. Drying may be carried out in a tray dryer, vacuum oven, air oven, cone vacuum dryer, rotary vacuum dryer, fluidized bed dryer, spin flash dryer, flash dryer, or the like. The drying may be carried out at tenperature less than that about 70°C, less than about 60°C, less than about 50°C, less than about 30°C, or any other suitable temperature, at atmospheric pressure or under a reduced pressure, as long as the daclatasvir is not degraded in quality. The drying may be carried out for any desired time untill the required product quality is achived; preferably drying is carried out at a temperature of about 45°C to about 65°C.

In another general aspect, there is provided a process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a suitable solvent selected from the group consisting of ketones, esters, ethers, alcohols, nitriles, amides, sulfoxides, halogenated hydrocarbons, aromatic hydrocarbon solvent, water and mixture thereof; and

b) removing the solvent from step a) solution to obtain amorphous form of daclatasvir free base. The step a) of providing a solution of daclatasvir includes, direct use of a reaction mixture containing daclataasvir that is obtained in the course of its synthesis; or dissolving daclatasvir in a solvent.

Any physical form of daclatasvir may be utilized for providing the solution of daclatasvir in step a). The dissolution temperature may range from about ambient to about reflux temperature of the solvent; preferably at about 40°C to about 80°C.

Example of suitable solvent include, but are ot limited to: ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters, such as ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; ethers, such as tetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether or 1,4-dioxane; alcohols, such as methanol, ethanol, 2-methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles, such as acetonitrile or propionitrile; amides, such as formamide, Ν,Ν-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene; water or any mixture of two or more thereof; preferably ethyl acetate or isopropyl ether.

The step of removing the solvent from step a) solution is carried out by any one of the following: concentrating the mass by solvent evaporation, rotational drying, spray drying, agitated thin film drying, freeze-drying and the likel; preferably by solvent evaporation.

The recovered solid may optionally be dried. Drying may be carried out in a tray dryer, vacuum oven, air oven, cone vacuum dryer, rotary vacuum dryer, fluidized bed dryer, spin flash dryer, flash dryer, or the like. The drying may be carried out at tenperature less than that about 70°C, less than about 60°C, less than about 50°C, less than about 30°C, or any other suitable temperature, at atmospheric pressure or under a reduced pressure, as long as the daclatasvir is not degraded in quality. The drying may be carried out for any desired time untill the required product quality is achived; preferably drying is carried out at a temperature of about 45 °C to about 65 °C.

In another general aspect, there is provided an amorphous form of daclatasvir free base prepared by the process described above may be used as an intermediate for preparation of daclatasvir or a pharmaceutically acceptable salt thereof or it can be used for pharmaceutical compositions thereof.

In another general aspect, there is provided an amorphous form of daclatasvir free base obtained by the process as descibed just above having a HPLC purity of about 98% or more, of about 99% or more, of about 99.5% or more as determined by high performance liquid chromatography (HPLC).

In another general aspect, there is provided an amorphous form of daclatasvir free base obtained by the process as descibed just above having an X-ray diffractogram (PXRD) substantially in accordance with Fig. 1.

Daclatasvir free base obtained by the process as descibed just above may be suitable for formulation as of daclatasvir dihydrochloride.

In another general aspect, there is provided a pharmaceutical composition comprising a solid daclatasvir free base as prepared by the process described above together with one or more pharmaceutically acceptable excipients.

In another general aspect, there is provided a process for preparation of pharmaceutically acceptable salt of daclatasvir, the process comprising:

a) providing a solution of solid daclatasvir free base in a suitable organic solvent, b) adding a suitable acid to the reaction solution, and

c) isolating the daclatasvir pharmaceutically acceptable salt.

The solid daclatasvir free base used herein the step a) may be obtained from the process described as above.

The step a) process involves dissolving solid daclatasvir free base in any suitable solvent. The suitable solvent include, but are ot limited to: ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters, such as ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; alcohols, such as methanol, ethanol, 2- methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles, such as acetonitrile or propionitrile; amides, such as formamide, N,N- dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene; water or any mixture of two or more thereof; preferably methanol or ethanol and a mixture thereof.

Suitable temperature for dissolving solid daclatasvir free base in a suitable solvent may be less than about 100°C, less than about 80°C, less than about 60°C, less than about 40°C, less than about 20°C, less than about 0°C or any other suitable temperature; preferably at about 40°C to 70°C.

The step b) process involves adding a suitable acid to the solution obtained in step a). The suitable acid includes but is not limited to hydrochloric acid, hydrobromic acid, acetic acid, trifluoro acetic acid or any pharmaceutically acceptable acid.

The acid source may be in the form of an aqueous, anhydrous or gas form, for example aqueous hydrochloric acid or solvent containing hydrochloric acid or hydrochloric acid gas can be used. The solvent may be used for dissolving acid source is selected from the group consisting of methanol, ethanol, isopropanol and the like and mixtures thereof; preferably ethanol.

Step c) involves isolating pharmaceutically acceptable salt of daclatasvir from step b) reaction mass. Isolation of pharmaceutically acceptable salt of daclatasvir in step c) may involve method include removal of solvent, cooling, concentrating the mass, evaporation, filtration, rotational drying, adding seed to include isolation, or the like. Stirring or other alternate methods such as shaking, agitation, or the like, may also be employed for the isoaltion.

Pharmaceutically acceptable salt of daclatasvir recovered using the process described just as above is daclatasvir dihydrochloride. In another general aspect, there is provided a process for the purification of daclatasvir dihydrochloride, the process comprising:

a) providing a solution of daclatasvir dihydrochloride in a mixture of organic solvents selected from the group consisting of alcohols, ester and mixture thereof, b) optionally adding seed to the reaction solution, and

c) isolating the pure daclatasvir dihydrochloride; wherein the alcohls are selected from the group comprising methanol, ethanol, isopropanol, n-propanol, n- butanol, i- butanol, t-butanol and the like and mixtures thereof; and esters are selected from the group comprising methyl acetate, ethyl acetate, isopropyl acetate and the like; and mixtures thereof.

In another preferred general aspect, there is provided a process for the purification of daclatasvir dihydrochloride, the process comprising:

a) dissolving daclatasvir dihydrochloride in a first alcohol solvent,

b) optionally concentrating the step a) solution,

c) optionally cooling the step a) or b) solution to about 25 °C to about 35 °C, d) adding second alcohol solvent or ester solvnet to the step a) or b) or c) solution, e) optionally adding seed crystals to the step d) solution, and

f) isolating the pure daclatasvir dihydrochloride; wherein the first alcohol solvent is methanol, second alcohol solvent is selecetd from the group comprising ethanol, isopropanol, n-propanol, n-butanol, i-butanol, t-butanol and the like; and the ester solvnet is selecetd from the group comprising methyl acetate, ethyl acetate, isopropyl acetate and the like.

In a preferred aspect, there is provided a process for the purification of daclatasvir dihydrochloride, wherein the organic solvents are a mixture of methanol and ethanol.

In a preferred aspect, there is provided a process for the purification of daclatasvir dihydrochloride, wherein the organic solvents are a mixture of methanol and ethyl acetate.

Starting daclatasvir dihydrochloride may be obtained from the process described as above or it may be obtianed by any process known in the art can be utilized for providing the solution of step a). The dissolution temperature may range from about ambeint to about reflux temperature of the solvent; preferably at about 25°C to about 55°C. Optionally treating the step a) solution with charcoal at a temperature of about 25 °C to about 55°C. Then the clear filterate may be partially evaporated at a temperature of about 35°C to about 55°C and then optionnaly cooling the reaction solution to about 25°C to about 35°C. Then, adding second alcohol solvent or ester solvent preferably ethanol or ethyl acetate to the reaction solution of step a) or step b) or step c). Optionally, seed crystals may be added to the reaction soltuon to initiate the crystallization. The addition of seed crystals may be advantageously carreid out at a temperature of about not more than 35 °C and stirring the resultent reaction mass for about 5 to 15 hours to precipitate out the pure daclatasvir dihydrochloride. Then isolating the pure daclatasvir dihydrochloride by methods known in the art for example decantation, centrifugation, gravity filteration, suction filtration, or any other technique for the recovery of solids; preferably by filteraion. Typically, if stirring is involved, the temperature during stirring can be less than about 25 °C. The recovered solid may optionally be dried. Drying may be carried out in a tray dryer, vacuum oven, air oven, cone vacuum dryer, rotary vacuum dryer or the like. The drying may be carried out at temperature less than about 100°C, less than about 80°C or any other suitable temperature, at atmospheric pressure or under a reduced pressure, as long as the daclatasvir dihydrochloride is not degraded in quality. The drying may be carried out for any desired time until the required product quality is achived. The dried product may be optionally be subjected to a size reduction procudere to produce desired particle size. Milling or micronization may be performed before drying, or after the completion of drying of the product. Techniques that may be used for particle size reduction include, without limition, ball, roller, and hammer milling, and jet milling.

The resulting pure daclatasvir dihydrochloride, obtained by the aforementioned process, may have a HPLC purity of about 99.5% or more, of about 99.9% or more as determined by HPLC and contains less than 0.1% as measured by HPLC of each of the impurity of Formula A, Formula B, Formula C or Formula D.

Pure daclatasvir dihydrochloride recovered using the purification process as described above is substantially in a crystalline form, which is characterized by one or more techniques such as DSC of Fig. 3 and/or XRD of Fig. 4.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has a differential scanning calorimetry substantially as depicted in Fig. 3. In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has the typical onset temperature of about 279°C by differential scanning calorimetry. In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride has the X-ray powder diffraction pattern substantially as depicted in Fig.4.

In another general aspect, there is provided a crystalline form of daclatasvir dihydrochloride, characterized by a differential scanning calorimetry substantially as depicted in Fig. 3 and X-ray powder diffraction pattern substantially as depicted in Fig.4.

In another general aspect, there is provided a pharmaceutical composition comprosing a pure daclatasvir dihydrochloride preparaed by the process described above, together with one or more pharmaceutically acceptable excipients.

In another general aspect, there is provided a daclatasvir oxalate salt.

In another general aspect, the daclatasvir oxalate salt has the X-ray powder diffraction pattern substantially as depicted in Fig. 2.

In another general aspect, the daclatasvir oxalate salt has the X-ray powder diffraction (XRD) peaks at about 5.5, 7.6, 10.8, 14.4, 16.2 andl9.8 ± 0.2° 2Θ. In another general aspect, there is provided a process for the preparation of daclatasvir oxalate salt, the process comprising:

a) providing a solution of daclatasvir base in a suitable solvent,

b) adding oxalic acid to the reaction solution, and

c) isolating the daclatasvir oxalate salt.

The step a) of providing a solution includes: direct use of a reaction mixture containing daclatasvir that is obtained in the cource of its synthesis; or dissolving daclatasvir in a suitable solvent. Any physical form of daclatasvir base may be utilized for providing the solution of daclatasvir in step a). The dissolution temperature may range from about ambient to reflux temperature of the solvent; preferably at about 25°C to about 35°C.

Suitable solvent used herein for dissolving daclatasvir base include, but are not limited to: ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters, such as ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; alcohols, such as methanol, ethanol, 2-methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles, such as acetonitrile or propionitrile; amides, such as formamide, Ν,Ν-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene; or any mixture of two or more thereof; preferably ethanol.

The addition of oxalic acid to the step a) solution in any form such as by dissolving the oxalic acid in a suitable solvent used in the reaction or may be by adding solid oxalic acid directly to the reaction solution; preefrably oxalic acid is dissolved in ethanol.

The isolation of daclatasvir oxalate salt may involve methods known in the art such as cooling, concentrating the mass, stirring or other alternate methods such as shaking, agitation, or the like. Suitable temperature for isolation may be less than about 30°C or any other suitable temperature.

The daclatasvir oxalate salt may be recovered by methods known in the art for example decantation, centrifugation, gravity filteration, suction filtration, or any other technique for the recovery of solids. The recovered solid may optionally be dried. Drying may be carried out in a tray dryer, vacuum oven, air oven, cone vacuum dryer, rotary vacuum dryer, or the like. The drying may be carried out at temperature less than about 100°C, less than about 80°C, less than about 60°C, or any other suitable temperature, at atmospheric pressure or under a reduced pressure, as long as the daclatasvir oxalate salt is not degraded in quality. The drying may be carried out for any desired time until the required product quality is achived; preferably drying is carried out at a temperature of about 40°C to about 55°C.

The recovered daclatasvir oxalate salt can be used as intermediate in the process of preparing pure daclatasvir or a pharmaceutically acceptable salt.

In another general aspect, there is provided a pharmaceutical composition comprosing a daclatasvir oxalate salt as prepared by the process described above together with one or more pharmaceutically acceptable excipients. In another general aspect, there is provided a process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof:

Formula I

comprising:

a) reacting biphenyl of Formula III with a compound of Formula IV in presence of a suitable Lewis acid; wherein "X" represents halogen to obtain a compound of Formula V,

Formula III Formula IV Formula V b) reacting the compound of Formula V with a compound of Formula VI to obtain a compound of Formula VII; wherein "PG" represents a suitable protecting group,

Formula VI Formula VII

c) cyclizing the compound of Formula VII to obtain a compound of Formula VIII,

Formula VIII

deprotecting the protecting group of Formula VIII with a suitable deprotecting agent to obtain a compound of Formula II or a pharmaceutically acceptable salt thereof, and

Formula II

e) converting the compound of Formula II or a pharmaceutically acceptable salt thereof in to daclatasvir or a pharmaceutically acceptable salt thereof. As used herein, the term "PG" suitable protecting group" refers to a moiety that can be selectively attached to and removed from a nitrogen atom to prevent it from participating in undesired chemical reactions, without unacceptably adverse effects on desired reactions. Examples of amino protecting groups include acetyl, tertiary butyloxy carbonyl (Boc), carboxy benzyl (Cbz), fluorenylmethyloxycarbonyl (Fmoc), phthalimide, triphenylmethyl, p-nitrobenzoyl (PNB), benzoyl, trimethylsilyl (TMS) and the like; preferably tertiary butyloxy carbonyl.

As used herein, the term "halogen" relates to fluorine, chlorine, bromine or iodine. The reported literatures involves a process for preparation of compound of Formula II, which involves reaction of l, -(biphenyl-4,4'-diyl)diethanone with bromine in methylene chloride for a prolonged reaction time of about 20 hr to obtain a compound of Formula V. Generally bromination reactions are corrosive and utmost care needs to be taken. Further, bromination reactions are always possible to yields dibromo compounds as impurity, which processes involve additional purifications to remove such impurities. Further, the bromination reaction mentioned in the reported literatures involves about 20 hours to completion, the prolonged period of reaction leads to an increase in the manufacturing cycle time. To overcome the difficulties associated with the processes described above, the inventors of the present invention have surprisingly developed a process in order to avoid corrosive bromination reactions instead adopts a simple and inexpensive raw materials i.e. reaction of biphenyl with chloroacetyl chloride in presence of aluminium chloride for the preparation of compound of Formula V with less reaction time period of about 1-4 hr thereby decreasing the cost as compared to the reported processes.

Further reported literatures involves reaction of compound of Formula V with 1 -boc-L- proline in acetonitrile to obtain a compound of Formula VII and then the compound rich acetonitrile reaction solvent was exchanged in to toluene and cyclized in presence of ammonium acetate to obtain a compound of Formula VIII. The use of two different solvents for conversion of compound of Formula V to Formula VIII increases the manufacturing time and cost. The present inventors have surprisingly found that the conversion of compound of Formula V to Formula VIII can be achieved by using a single solvent without isolating a compound of Formula VII. The step a) of the aforementioned process involves reaction of biphenyl of Formula III with a compound of Formula IV in presence of a suitable Lewis acid; wherein "X" represents halogen; preferably chloro to obtain a compound of Formula V.

The suitable Lewis acid includes but is not limited to aluminum chloride, aluminum bromide, ferric chloride, tin chloride, or stannic chloride and the like; preferably aluminum chloride. The reaction of biphenyl of Formula III with chloroacetyl chloride of Formula IV may be carried out in a suitable solvent. The suitable solvent includes but is not limited to ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters, such as ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; nitriles, such as acetonitrile or propionitrile; amides,such as formamide, N,N-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene; or any mixture of two or more thereof; preferably methylene chloride.

The reaction of biphenyl of Formula III with chloroacetyl chloride of Formula IV is carried out at a temperature of about 25 °C to reflux temperature for a period of about 1 hour to about 5 hours; preferably at about 30°C to about 50°C for a period of about 3 hours.

After completion of the reaction, the reaction mass may be advantageously quenched in to alcohol solvent such as methanol, ethanol and the like at a temperature of about 0°C to about 10°C to precipitate out compound of Formula V as a solid. The precipitated compound of Formula V may be separated out by methods known in the art, for example filtration.

The step b) of aforementioned process involves reaction of compound of Formula V with a compound of Formula VI in presence of a suitable base and in an organic solvent to obtain a compound of Formula VII; wherein "PG" represents a suitable protecting group; preferably boc protecting group.

The suitable base used herein for the reaction of compound of Formula V with a compound of Formula VI; wherein "PG" as defined as above, include but is not limited to inorganic bases selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide and the like; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide and the like; alkali metal carbonates such as sodium carbonate, potassium carbonate, cesium carbonate and the like; alkali metal bicarbonates such as sodium bicarbonate, potassium bicarbonate and the like; and organic bases selected from the group consisting of triethylamine, isopropyl ethylamine, diisopropyl amine, diisopropyl ethylamine, N-methyl morpholine, piperidine, pyridine and the like and mixtures thereof; preferably diisopropyl amine.

The organic solvent for the reaction of compound of Formula V with a compound of Formula VI; wherein "PG" as defined as above, includes but is not limited to ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; nitriles, such as acetonitrile or propionitrile; amides, such as formamide, N,N-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides, such as dimethylsulfoxide; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons, such as toluene, xylene; or any mixture of two or more thereof; preferably toluene.

The reaction of compound of Formula V with a compound of Formula VI; wherein "PG" as defined as above, is carried out at a temperature of about 25 °C to reflux temperature; preferably at about 60°C to about 80°C.

After completion of the reaction, advantageously the inorganic solids were separated by filtering the reaction mass and the filterate is proceeded for next step without isolating the compound of Formula VII; wherein "PG" as defined as above.

In another general aspect, there is provided a process for preparation of compound of Formula VIII, comprising: cyclization of a compound of Formula VII in a same reaction solvent used for preparation of compound of Formula VII without isolating the compound from the reaction mass.

The step c) of aforementioned process involves cyclization of compound of Formula VII in presence of a suitable ammonium salt such as ammonium acetate and the like to obtain a compound of Formula VTII; wherein "PG" as defined as above. The cyclization of compound of Formula VII; wherein "PG" as defined as above, is carried out at a temperature of about 25°C to reflux temperature; preferably at about 80°C to 100°C.

After completion of the reaction, aqueous alcoholic solvent such as aqueous methanol may advantageously be added to the reaction mass to precipitate out the compound of Formula VIII as a solid. The precipitated compound of Formula VIII may be separated by methods known in the art, for example filtration.

In another general aspect, there is provided a process for preparation of compound of Formula VIII, comprising: the step b) and step c) are carried out in a single solvent without isolating the compound of Formula VII.

The step d) of aforementioned process involves deprotection of Formula VIII; wherein "PG" as defined as above, with a suitable deprotecting agent to obtain a compound of Formula II or a pharmaceutically acceptable salt thereof. The suitable deprotecting agent includes but is not limited to source of acid in a solvent such as HC1 in methanol, HC1 in ethanol, HC1 in isopropyl alcohol, HC1 in methylene chloride, HC1 in dioxane, HC1 in diethyl ether and the like; preferably HC1 in isopropyl alcohol.

The deprotection of Formula VTII; wherein "PG" as defined as above may be carried out in a suitable solvent. The suitable solvent includes but is not limited to alcohols, such as methanol, ethanol or isopropyl alcohol; halogenated hydrocarbons, such as methylene chloride, chloroform, or chlorobenzene; ethers, such as diethyl ether, tetrahydrofuran, or methyl tetrahydrofuran; water or any mixture of two or more thereof; preferably isopropyl alcohol and water. The deprotection of Formula VIII; wherein "PG" as defined as above, is carried out at a temperature of about 20°C to reflux temperature; preferably at about 25 °C to 40°C.

In another general aspect, there is provided a process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof, comprising: preparing the compound of Formula II or a pharmaceutically acceptabul salt thereof according to the process as described above and converting the Formula II or a pharmaceutically acceptabul salt thereof in to daclatasvir or a pharmaceutically acceptable salt thereof by any process known in the art or by the process described in the example section.

As used herein, the pharmaceutical acceptable salts include acid addition salts formed with inorganic acids or with organic acids. The inorganic acids may be selected from hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, sulfamic acid, acetic acid, trifluoro acetic acid and the like; organic acids such as acetic acid, oxalic acid, fumaric acid, citric acid, succinic acid, tartaric acid, salicylic acid, benzoic acid, glycolic acid, methane sulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p- toluenesulfonic acid, lactic acid, maleic acid, malonic acid, malic acid, isethionic acid, lactobionic acid, mandelic acid and the like.

As used herein the X-Ray powder diffraction can be measured by an X-ray powder Diffractometer equipped with a Cu-anode ([λ] =1.54 Angstrom), X-ray source operated at 30kV, 15 mA. Two-theta calibration is performed using an NIST SRM 640c Si standard. The sample was analyzed using the following instrument parameters: measuring range=3-45°20; step width=0.020°; and scan speed=5°C/minute.

All DSC data reported herein were analyzed using DSC (DSC Q200, TA instrumentation, Waters) in an aluminium pan at a scan rate of 10°C per minute with an Indium standard.

In general aspect, there is provided daclatasvir or a pharmaceutically acceptable salt thereof and its intermediates, obtained by the above process, as analyzed using high performance liquid chromatography ("F£PLC") with the conditions are tabulated below:

Wavelength By UV-300nm

Injection Volume lOul

Elution Gradient (T/B %): 0/30,25/35,35/50,40/80,50/80,55/30,60/30

In general aspect, there is provided a pharmaceutical composition, comprising daclatasvir or a pharmaceutically acceptable salt thereof prepared by the processes of the present invention and at least one pharmaceutically acceptable excipient. Such pharmaceutical composition may be administered to a mammalian patient in any dosage form, e.g., solid, liquid, powder, injectable solution, etc.

EXAMPLES

The following non limiting examples illustrate specific embodiments of the present invention. They are not intended to be limiting the scope of the present invention in any way.

Example 1: Preparation of l,l'-biphenyl-4,4'-diylbis(2-chloroethanone) of formula V

In 1 lit three necked round bottom flask equipped with mechanical stirrer, thermometer and an addition funnel, 216.3 g anhydrous A1C1₃ and 500 ml methylene chloride were taken at 25-30°C. The content was stirred for 20 min at 25-30°C. To this, 183.1 g chloro acetyl chloride was added slowly at 5-10°C over a period of 25 min and stirred for 30 min at same temperature. To this, biphenyl solution (100 g biphenyl dissolved in 300 methylene chloride) was added at 5-10°C and stirred for 30 min at same temperature. Reaction mass was heated to 35-40°C and stirred for 3 hr. After completion of the reaction, cool the reaction mass to 25-30°C. In another 5 lit three necked round bottom flask, 3 liters methanol was taken and cooled to 0-5 °C. The above reaction mass was quenched in to methanol at 0-30°C and stirred for 1 hr at 25-30°C. Filtered the obtained solids and washed with 100 ml methanol. To the obtained solids 5 v water was added and stirred for 30 min at 25-30°C. Filtered the solids and washed with water. To the solid 500 ml methanol was added and stirred for 30 min at 25-30°C. Filtered the solids and washed with 100 ml methanol and dryed at 60-65 °C to get title compound. Yield: 180 g.

Example 2: Preparation of di-tert-butyl (2S,2'S)-2,2'-(4,4'-biphenyldiylbis(lH- imidazole-5,2-diyl)di(l-pyrrolidin carboxylate) of formula VIII

In 2 lit three necked round bottom flask equipped with mechanical stirrer, 50 g of 1,1'- biphenyl-4,4'-diylbis(2-chloroethanone) of Formula V, 400 ml toluene, 80.51 g of N-boc- proline and 63 g diisopropylethylamine were added at 25-30°C and stirred for 15 min at same temperature. Reaction mass was heated to 70-75°C and stirred for 4 hr. After completion of the reaction, filtered the reaction mass and washed with 100 ml toluene. To the filterate, 250.5 g ammonium acetate was added and heated to 95°C and stirred for about 20hr at same temperature. After completion of the reaction, reaction mass was allowed to cool to 60°C and 500 ml 10% methanol in water was added slowly at 50- 55 °C. The precipitated solids was filtered and washed with water. The obtained solid compound was stirred in 250 ml methanol at 60-65 °C for 1 hr and the reaction mass was allowed to cool to 25-30°C, filtered the solids and washed with 50 ml methanol followed by dried at 60-65 °C to get title compound. Yield: 70.2 g.

Example 3: Preparation of 5,5'-(4,4'-biphenyldiyl)bis-(2-((2S)-2-pyrrolidinyl)- lHimidazole 4.HC1 of Formula II

In 250 ml three necked round bottom flask equipped with mechanical stirrer, 10 g of di- tert-butyl (2S,2'S)-2,2'-(4,4'-biphenyldiylbis(lH-imidazole-5,2-diyl)di(l-pyrrolidin carboxylate) of formula VIII and 70 ml isopropyl alcohol were added and stirred for 5 min at 25-30°C. To this, 3N HCl in isopropyl alcohol was added slowly over 60 min at 25-30°C and stirred for 1 hr. After completion of the reaction, solvent was removed under vacuum at 40-45°C. To this, 20 ml acetone was charged at 25-27°C and stirred for 30 min, filtered the solids and washed with 20 ml acetone and dried at 50-55 °C to get title compound. Yield: 6.3 g; Purity by HPLC: 99.82%.

Example 4: Preparation of 5,5'-(4,4'-biphenyldiyl)bis-(2-((2S)-2-pyrrolidinyl)- lHimidazole 4.HC1 of Formula II

In 1 lit three necked round bottom flask equipped with mechanical stirrer, 100 g of di- tert-butyl (2S,2'S)-2,2'-(4,4'-biphenyldiylbis(lH-imidazole-5,2-diyl)di(l-pyrrolidin carboxylate) of formula VIII and 300 ml isopropyl alcohol and 130 ml water were added and stirred for 5 min at 25-30°C. To this, 130 ml concentrated HCl was added slowly over 60 min at 25-30°C and stirred for 15 min. Reaction mass was heated to 50-55 °C and stirred for 3 hrs at same temperature. After completion of the reaction, 700 ml isopropyl alcohol was added to the reaction mass at 50-55°C. Reaction mass was allowed to cool to 25-35°C and stirred for 1 hr at same temperature, filtered the solids and washed with 100 ml isopropyl alcohol. The obtained solid was dissolved in 400 ml methanol at 50-55°C and stirred for 3 hrs at same temperature. Reaction mass was allowed to cool to 25-35°C and stirred for 1 hr at same temperature. Precipitated solid was filtered and washed with 100 ml methanol and 150 ml acetone and dried at 60-65°C to get title compound. Yield:

70 g; Purity by HPLC: 99.9%. Example 5: Preparation of amorphous form of daclatasvir.

In 3 lit three necked round bottom flask equipped with mechanical stirrer, thermometer,

71 g HOBt and 1 lit acetonitrile were charged at 25-30°C u/nitrogen and stirred for 15 min at same temperature. To this, 92 g N-(methoxy carbonyl)-L-valine and 100.8 g EDC HCl were charged at 25-30°C u/nitrogen and stirred for 1-2 hrs at same temperature. To the reaction mass 100 g 5,5'-(4,4'-biphenyldiyl)bis-(2-((2S)-2-pyrrolidinyl)-lH- imidazole 4.HC1 of Formula II was added at 25-30°C u/nitrogen and cooled the reaction mass to 0-5°C. To the reaction mass mixture of 136 g of dried diisopropyl ethyl amine was added at 0-5°C and heated to 25-30°C, stirred for 15-16 hr at same temperature. After completion of the reaction, 600 ml 13% aq NaCl solution was charged and reaction mass was heated to 50-55°C and stirred for 1-2 hrs. Reaction mass was allowed to cool to 25-30°C, charged 600 ml ethyl acetate and stirred for 15 min. Layers were separated and the organic layer was washed with 2%(w/v) aq NaOH solution (2x600 ml), 13% aq NaCl solution (3x600 ml) sequentially. Then the product containing organic layer was concentrated completely under vacuum at 40-45 °C. Strip of the reaction mass was with ethyl acetate (40+30 ml) at 40-45°C under mild vacuum to obtain a solid. In another round bottom flask the obtained solid and 1 lit isopropyl ether was charged at 25-30°C and heated to 65-70°C. After 1 hr stirring at 65-70°C reaction mass was cooled to 25- 30°C and stirred for 1 hr. The precipitated solid was filtered and washed with 100 ml isopropyl ether and was further dried at 50-55°C under vacuum for 8 hr to get amorphous form of daclatasvir. Yield: 124 g; PXRD: Fig. 1; Purity by HPLC: 99.1%.

Example 6: Preparation of daclatasvir dihydrochloride

In 1 lit three necked round bottom flask equipped with mechanical stirrer, thermometer, 124 g of amorphous form of daclatasvir free base and 150 ml methanol were taken at 25- 35°C. Reaction mass was heated to 50-55°C. To the reaction mass slowly added 13% ethanolic HC1 (250 ml) at 50-55°C and stirred for 3 hr at same temperature. Reaction mass was allowed to cool to 25-30°C and stirred for 1 hr. The precipitated solid was filtered and washed with a mixture of methanol (33 ml) and ethanol (66 ml) and further dryed at 50-55°C to get daclatasvir dihydrochloride. Yield: 120 g.

Example 7: Preparation of daclatasvir oxalate salt

In 50 ml three necked round bottom flask equipped with mechanical stirrer, thermometer, 5 g of daclatasvir and 10 ml ethanol were taken at 25-35°C. To this, oxalic acid (1.52 g was dissolved in 15 ml ethanol) was added at 45-50°C. The content was stirred for 1 hr at 45-50°C. Reaction mass was allowed to cool to 25-30°C and stirred for 1 hr at same temperature. Precipitated solid was filtered and washed with 5 ml ethanol and dryed at 45-50°C to get 4.1 g of daclatasvir oxalic acid crude. To the obtained crude material 25 ml methanol was added and stirred at 40-45 °C. To the reaction mass 75 ml ethanol was added at 40-45°C and stirred for 1 hr at same temperature. Reaction mass was allowed to cool to 25-30°C and stirred for 6 hr. The precipitated solid was filtered and washed with 5 ml ethanol and further dryed at 45-50°C to get daclatasvir oxalic acid. Yield: 2.62 g; Purity by HPLC: 99.8%; PXRD: Fig. 4; Oxalate content: 12.97(%w/w).

Example 8: Purification of daclatasvir dihydrochloride In 1 lit three necked round bottom flask equipped with mechanical stirrer, thermometer, 100 g daclatasvir dihydrochloride and 500 ml methanol were taken at 25-30°C. The content was stirred for 30 min at 25-30°C. To this, 50 ml methanol slurry of 15 g PS-133 carbon was added and stirred for 1 hr at 25-30°C.The content was filtered through hyflo bed, and the bed was washed with 200 ml methanol. The filterate was concentrated partially under vacuum at 40-45 °C till 300 ml methanol remains in the flask. Reaction mass was cooled to 25-30°C and 900 ml ethanol and 0.15 g seed material was added and stirred for 12 hr at same temperature. The precipitated solid was filtered and washed with a mixture of methanol: ethanol (1 :2; 100 ml) and further dried at 70-75°C under vacuum for 12-15 hr to get pure daclatasvir dihydrochloride. Yield: 65 g; DSC: Fig. 3; PXRD: Fig. 4; Purity by HPLC: 99.8%; Formula A by HPLC: 0.02%; Formula C by HPLC: 0.04%; Formula D by HPLC: Not detected (LOD-0.01%).

Example 9: Purification of daclatasvir dihydrochloride

In 1 lit three necked round bottom flask equipped with mechanical stirrer, thermometer, 100 g daclatasvir dihydrochloride and 500 ml methanol were taken at 25-30°C. The content was stirred for 30 min at 25-30°C. To this, 50 ml methanol slurry of 15 g PS-133 carbon was added and stirred for 1 hr at 25-30°C.The content was filtered through hyflo bed, and the bed was washed with 200 ml methanol. The filterate was concentrated partially under vacuum at 40-45 °C till 300 ml methanol remains in the flask. Reaction mass was allowed to cool to 25-30°C and 900 ml ethyl acetate and 0.15 g seed crystals were added and stirred for 12 hr at same temperature. The precipitated solid was filtered and washed with a mixture of methanol: ethyl acetate (1:2; 100 ml) and further dried at 70-75°C under vacuum for 12-15 hr to get pure daclatasvir dihydrochloride. Yield: 75 g; Purity by HPLC: 99.7%.

While the invention has been described with reference to above detailed description and the preferred examples, it is not intended to be limited thereto. Therefore the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. For example, the functions described above and implemented as the best mode for operating the present invention are for illustration purposes only. Other arrangements and methods may be implemented by those skilled in the art without departing from the scope and spirit of this invention. Moreover, those skilled in the art will envision other modifications within the scope and spirit of the specification appended hereto.

Claims

WE CLAIM:

Claim 1 : A process for preparation of daclatasvir of Formula I or a pharmaceutically acceptable salt thereof:

Formula I

comprising:

a) reacting biphenyl of Formula III with a compound of Formula IV in presence of a suitable Lewis acid; wherein "X" represents a halogen, to obtain a compound of Formula V,

Formula III Formula IV Formula V b) reacting the compound of Formula V with a compound of Formula VI in presence of a base in an organic solvent to obtain a compound of Formula VII; wherein "PG" represents a suitable protecting group,

Formula VI Formula VII

c) cyclizing the compound of Formula VII to obtain a compound of Formula VIII,

Formula VIII

d) deprotecting the protecting group of Formula VIII with a suitable deprotecting agent to obtain a compound of Formula II or a pharmaceutically acceptable salt thereof, and

Formula II

e) converting the compound of Formula II or a pharmaceutically acceptable salt thereof in to daclatasvir or a pharmaceutically acceptable salt thereof.

Claim 2: The process of claim 1, wherein the step b) and step c) are carried out in a single solvent without isolating the compound of Formula VII.

Claim 3: The process of claim 1, wherein the "X" represents chlorine and "PG" represents tertiary butyloxy carbonyl.

Claim 4: The process of claim 1, wherein the suitable Lewis acid is selected from the group consisting of aluminum chloride, aluminum bromide, ferric chloride, tin chloride and stannic chloride.

Claim 5: The process of claim 4, wherein the suitable Lewis acid is aluminum chloride.

Claim 6: The process of claim 1, wherein the step a) is carried out in a suitable solvent selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters selected from ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, Ν,Ν-dimethylformamide or N,N- dimethylacetamide; sulfoxides selected from dime thylsulf oxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene and mixture thereof.

Claim 7: The process of claim 6, wherein the suitable solvent is methylene chloride.

Claim 8: The process of claim 1, wherein the step a) is carried out at a temperature of about 30°C to about 50°C.

Claim 9: The process of claim 1, wherein the compound of Formula V is isolated by quenching the step a) reaction mass in to alcohol solvent selected from methanol, ethanol and mixture thereof.

Claim 10: The process of claim 1, wherein the step b) is carried out in presence of a suitable base and in an organic solvent. Claim 11 : The process of claim 10, wherein the suitable base is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium methoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, cesium carbonate, sodium bicarbonate, potassium bicarbonate, triethylamine, isopropyl ethylamine, diisopropyl amine, diisopropyl ethylamine, N-methyl morpholine, piperidine, pyridine and mixtures thereof.

Claim 12: The process of claim 10, wherein the organic solvent is selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, Ν,Ν-dimethylformamide or N,N-dimethylacetamide; sulfoxides selected from dimethylsulfoxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene, xylene and mixture thereof. Claim 13: The process of claim 10, wherein the suitable base is diisopropyl amine and the organic solvent is toluene.

Claim 14: The process of claim 1, wherein the step b) is carried out at a temperature of about 60°C to about 80°C.

Claim 15: The process of claim 1, wherein the step c) is carried out in presence of ammonium acetate.

Claim 16: The process of claim 1, wherein the step c) is carried out at a temperature of about 80°C to about 100°C.

Claim 17: The process of claim 1, wherein the suitable deprotecting agent is elected from the group consisting of HC1 in methanol, HC1 in ethanol, HC1 in isopropyl alcohol, HC1 in methylene chloride, HC1 in dioxane and HC1 in diethyl ether.

Claim 18: The process of claim 1, wherein the step d) is carried out at a temperature of about 25°C to about 40°C.

Claim 19: A process for the purification of daclatasvir dihydrochloride, the process comprising:

a) dissolving daclatasvir dihydrochloride in a first alcohol solvent,

b) optionally concentrating the step a) solution,

c) optionally cooling the step a) or b) solution to about 25 °C to about 35 °C, d) adding second alcohol solvent or ester solvnet to the step a) or b) or c) solution, e) optionally adding seed crystals to the step d) solution, and f) isolating the pure daclatasvir dihydrochloride; wherein the first alcohol solvent is methanol, second alcohol solvent is selecetd from the group comprising ethanol, isopropanol, n-propanol, n-butanol, i-butanol, t-butanol and the like; and the ester solvnet is selecetd from the group comprising methyl acetate, ethyl acetate, isopropyl acetate and the like.

Claim 20: The process of claim 19, wherein the first alcohol solvent is methanol and second alcohol solvent is ethanl and ester solvnet is ethyl acetate.

Claim 21 : The process of claim 19, wherein the step a) is carried out at a temperature of about 25°C to about 55°C.

Claim 22: A crystalline form of daclatasvir dihydrochloride, characterized by a differential scanning calorimetry substantially as depicted in Fig. 3 and X-ray powder diffraction pattern substantially as depicted in Fig.4.

Claim 23 : A crystalline form of daclatasvir dihydrochloride has a differential scanning calorimetry substantially as depicted in Fig. 3.

Claim 24: Daclatasvir oxalate salt.

Claim 25 : Daclatasvir oxalate salt has the X-ray powder diffraction pattern substantially as depicted in Fig. 2.

Claim 26: A process for the preparation of daclatasvir oxalate salt, the process comprising:

a) providing a solution of daclatasvir base in a suitable solvent,

b) adding oxalic acid to the reaction solution, and

c) isolating the daclatasvir oxalate salt. Claim 27: The process of claim 26, wherein the suitable solvent is selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters selected from ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; alcohols selected from methanol, ethanol, 2-methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, N,N-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides selected from dimethylsulfoxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene and mixture thereof.

Claim 28: The process of claim 27, wherein the suitable solavent is ethanol. Claim 29: The process of claim 26, wherein the step a) is carried out at a temperature of about 25°C to about 35°C.

Claim 30: Amorphous form of daclatasvir free base. Claim 31 : Amorphous form of daclatasvir free base has the X-ray powder diffraction pattern substantially as depicted in Fig.1.

Claim 32: A process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a solvent; and

b) isolating amorphous form of daclatasvir free base.

Claim 33: The process of claim 32, wherein the solvent is selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters selected from ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; ethers selected from tetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether or 1,4-dioxane; alcohols selected from methanol, ethanol, 2- methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, N,N- dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides selected from dimethylsulfoxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene; water and any mixture thereof. Claim 34: The process of claim 33, wherein the solvent is ethyl acetate or isopropyl ether.

Claim 35: The process of claim 32, wherein the step a) is carried out at a temperature of about 40°C to about 80°C.

Claim 36: A process for the preparation of an amorphous form of daclatasvir free base, the process comprising:

a) providing a solution of daclatasvir in a suitable solvent selected from the group consisting of ketones, esters, ethers, alcohols, nitriles, amides, sulfoxides, halogenated hydrocarbons, aromatic hydrocarbon solvent, water and mixture thereof; and

b) removing the solvent from step a) solution to obtain amorphous form of daclatasvir free base. Claim 37: The process of claim 36, wherein the solvent is selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters selected from ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; ethers selected from tetrahydrofuran, dimethyl ether, isopropyl ether, methyl tertiary butyl ether or 1,4-dioxane; alcohols selected from methanol, ethanol, 2- methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, N,N- dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides selected from dimethylsulfoxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene; water and mixture thereof. Claim 38: The process of claim 37, wherein the solvent is ethyl acetate or isopropyl ether.

Claim 39: The process of claim 36, wherein the step a) is carried out at a temperature of about 40°C to about 80°C.

Claim 40: A process for preparation of pharmaceutically acceptable salt of daclatasvir, the process comprising:

a) providing a solution of solid daclatasvir free base in a suitable organic solvent, b) adding a suitable acid to the reaction solution, and

c) isolating the daclatasvir pharmaceutically acceptable salt.

Claim 41 : The process of claim 40, wherein the organic solvent is selected from the group consisting of ketones selected from acetone, methyl ethyl ketone, methyl isobutyl ketone, or diethyl ketone; esters selected from ethyl acetate, propyl acetate, isopropyl acetate, or butyl acetate; alcohols selected from methanol, ethanol, 2-methoxy ethanol, isorpropyl alcohol, diethylene glycol, cyclohexanol, or glycerol; nitriles selected from acetonitrile or propionitrile; amides selected from formamide, N,N-dimethylformamide or Ν,Ν-dimethylacetamide; sulfoxides selected from dimethylsulfoxide; halogenated hydrocarbons selected from methylene chloride, chloroform, or chlorobenzene; aromatic hydrocarbons selected from toluene; water and mixture thereof.

Claim 42: The process of claim 41, wherein the solvent is methanol, ethanol or a mixture thereof. Claim 43 : The process of claim 40, wherein the step a) is carried out at a temperature of about 40°C to about 70°C.

Claim 44: The process of claim 40, wherein the suitable acid is selected from the group consisting of hydrochloric acid, hydrobromic acid, acetic acid and trifluoro acetic acid. Claim 45 : Daclatasvir containing less than 0.1% as measured by HPLC of one or more of impurities of Formula A, Formula B, Formula C or Formula D.

Claim 46: A pharmaceutical composition comprising daclatasvir according to claim 1-45 and at least one pharmaceutically acceptable excipient.