The present invention provides lifitegrast substantially free from compound of Formula I,
.

Present invention further provides a process for preparation of compound of Formula I for the identification and the quantification of itself in the lifitegrast.

BACKGROUND OF THE INVENTION
Lifitegrast, chemically known as (S)-2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid, approved by the USFDA under the brand name Xiidra for the treatment of dry eye disease (DED). Lifitegrast is generically disclosed in US 7,314,938.

US 8,080,562 and US 8,378,105 disclose process for the preparation of lifitegrast as mentioned in the scheme below:

Scheme 1:

US 8,367,701 disclose process of recrystallization of lifitegrast by slurrying lifitegrast in methyl ethyl ketone or acetonitrile followed by filtering and washing with water.

US 9,085,553 disclose a process of recrystallization of lifitegrast from solution comprising acetone, preferably aqueous acetone. It also discloses an alternate method for preparing lifitegrast which includes preparation of lifitegrast ester followed by hydrolysis of said ester as shown in the scheme below:

Scheme 2:

US 9,085,553 also disclose a process of preparing protected lifitegrast of Formula-J by another method as disclosed in the scheme below:
Scheme 3:

Although, certain published references provides processes for the preparation and purification of lifitegrast, however, present invention is focussed towards the development of a process for the preparation of pure lifitegrast which is substantially free from impurities and has a total purity of about 99.5% w/w and above.

OBJECT OF THE INVENTION
The main object of the present invention is to provide pure lifitegrast free from compound of Formula I and other related impurities.

Another object of the present invention is to provide a compound of Formula I.

Another object of the present invention is to provide a purification process to get pure lifitegrast.

Another object of the present invention is to provide a process for the preparation of compound of Formula I as a reference standard for its detection in lifitegrast.

SUMMARY OF THE INVENTION
Main aspect of the present invention provides, lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula I, relative to lifitegrast by area percentage of HPLC,
.

The another aspect of the present invention provides, lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carbonyl) -5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said compound of Formula I is less than about 0.2% w/w relative to lifitegrast by area percentage of HPLC,
.

In another aspect, the present invention provides a process for preparation of (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula I,
,
wherein said process comprising the steps of:
a) reacting (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III with compound of Formula VI to give N-protected (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula XIII,

;
wherein PG is a protecting group; and
b) converting compound of Formula XIII to (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I in presence of suitable reagent,
.

In another aspect, the present invention provides a process for the preparation of pure lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said process comprising the steps of:
a) condensing protected amine compound of Formula VI with acid protected compound of Formula VII or its pharmaceutical acceptable salt, to give protected compound of Formula VIII,

wherein PG is an amine protecting group, and R is an acid protecting group;
b) de-protecting amine group of compound of Formula VIII in presence of acid followed by hydrolysis in presence of base, in absence of alcohol to give compound of Formula III or pharmaceutically acceptable salt thereof;

c) purifying compound of Formula III in suitable solvent, wherein said Formula III is free of compound of Formula VIII,

wherein, PG is an amine protecting group, and R is an acid protecting group;
d) reacting compound of Formula III with benzofuran-6-carboxylic acid of Formula IV in presence of a condensing agent to give crude lifitegrast, wherein said benzofuran-6-carboxylic acid is optionally converted to benzofuran-6-carbonyl chloride,
; and
d) purifying and isolating the pure lifitegrast wherein said lifitegrast is substantially free from compound of Formula I,
.

In another aspect, the present invention provide (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1, 2,3,4-tetrahydro isoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula I,
.

DETAILED DESCRIPTION
The term “substantially free” or “substantially pure” used in the context of the present invention means lifitegrast having each impurity less than about 0.2% by area percentage of HPLC. In particular, less than about 0.15% by area percentage of HPLC, and more particularly, not in a detectable amount by area percentage of HPLC.

The term “PG” as used in the context of the present invention is a protecting group specifically amine protecting group comprising of any carbon or silyl containing moiety that protects the amine from undesired reactions.

All ranges recited herein include the endpoints and the terms “about”, “from”, “to” are to be construed as modifying a value they are applied to such that it is not absolute and includes, to the very least, the degree of expected experimental error, limitation of method or instrument error for a given technique used to measure the value.

As used herein, the term “solution” or “reaction mixture” does not limit to a clear solution only and includes any hazy or opaque mass obtained.

The condensing agent used in context of the present invention, is selected from the group comprising of 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), N,N'-Dicyclohexylcarbodiimide (DCC), N-[(Dimethylamino)-1H-1,2,3-triazolo-[4,5-b]pyridin-1-ylmethylene]-N-methylmethanaminium hexafluorophosphate N-oxide (HATU), Hydroxybenzotriazole (HOBt), Hexafluorophosphate Benzotriazole Tetramethyl Uronium (HBTU), O-(Benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), thionyl chloride, oxalyl chloride, phosphorus oxychloride, and the like.

The base used for preparing lifitegrast and compound of Formula I, especially during condensation reaction, is selected from, but not limited to, dimethyl amino pyridine (DMAP), triethylamine (TEA), diisopropyl ethyl amine (DIPEA), 2,4,6-collidine, 1,3,5-collidine, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, cesium bicarbonate and the like.

The solvent(s) used for preparing lifitegrast and compound of Formula I, is selected from, but not limited to, polar aprotic solvents such as dimethyl formamide (DMF), dimethyl acetamide (DMAc), N-methyl pyrrolidinone (NMP), and dimethyl sulfoxide (DMSO); halogenated solvents such as dichloromethane (DCM), dichlorobenzene, dichloroethane; esters such as ethyl acetate (EtOAc), n-butyl acetate, isopropyl acetate, n-propyl acetate, propenyl acetate, pentyl acetate; ethers such as diethyl ether, tetrahydrofuran (THF), dioxane, methyl tetrahydrofuran (Me-THF); ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; organic amines such as secondary and tertiary amines; other solvents such as acetonitrile, xylene, toluene water; and mixture thereof.

The present invention will now be explained in details. While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the scope of the invention as defined by the appended claims.

The steps of a method may be providing more details that are pertinent to understanding the embodiments of the present invention and so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

Further characteristics and advantages of the process according to the invention will result from the description herein below of preferred exemplary embodiments, which are given as indicative and non-limiting examples.

In one embodiment, the present invention provides lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl) phenyl)propanoic acid of Formula I, relative to lifitegrast by area percentage of HPLC,
.

In a preferred embodiment, the present invention provides lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydro isoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said compound of Formula I is less than about 0.2% w/w relative to lifitegrast by area percentage of HPLC,
.

In another embodiment, the compound of Formula I is formed as impurity during the process of preparing lifitegrast.

In one another embodiment, the (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I is isolated in pure form and can be used as reference standard.

In one another embodiment, the present invention provides (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl )phenyl)propanoic acid of Formula I,
.

In another embodiment, the present invention provides a process for preparation of (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl) phenyl)propanoic acid of Formula I,
,
wherein said process comprising the steps of:
a) reacting (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III with compound of Formula VI to give N-protected (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl) phenyl)propanoic acid of Formula XIII,

;
wherein PG is a protecting group; and
b) converting compound of Formula XIII to (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydro isoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I in presence of suitable reagent,
.

In another embodiment, wherein said compound of Formula III is purified before condensing with compound of Formula VI, wherein said Formula III is free of compound of Formula VIII,

wherein, PG is an amine protecting group, and R is an acid protecting group.

In another embodiment, compound of Formula XIII is converted to compound of Formula I by deprotecting N-protected (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula XIII in presence of acid followed by condensation of deprotected intermediate of Formula XIV with suitable condensing agent in presence of suitable condensing reagent as depicted in the scheme below:
.
In one another embodiment, in the process for preparation of compound of Formula I, one or more steps are carried out in single pot without isolation of intermediate (s), or, each intermediate is isolated and optionally purified before proceeding to next step.

In one another embodiment, compound of Formula XIV may be reacted with benzofuran-6-carbonyl chloride wherein said benzofuran-6-carbonyl chloride is prepared insitu from benzofuran-6-carboxylic acid.

In one another embodiment, the compound of Formula III is either taken directly as a reaction mixture, or may be isolated from the reaction mixture as crude mass, or may be purified and crystallized before reacting with compound of Formula IV.

In another embodiment, the isolated (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I is characterized by 1H NMR chemical shifts (DMSO-d6, 400 MHz) at d 8.90 (bs, 1H), 8.13 (d, 1H), 7.85 (s, 1H), 7.75-7.77 (d, 2H), 7.65-7.67 (d, 1H), 7.54-7.57 (t, 1H), 7.48 (s, 1H), 7.35-7.37 (d, 1H), 7.05 (s, 1H), 4.69-4.85 (m, 4H), 4.4 (s, 1H), 3.92 (bs, 1H), 3.67 (bs, 2H), 3.44-3.47 (m, 2H), 3.28 (m, 3H), 3.13-3.14 (d, 3H), 3.00-3.06 (m, 1H), 2.84-2.89 (m, 2H), 2.77-2.78 (m, 1H), and 2.69-2.71 (m, 1H).

In another embodiment, the present invention provides a process for the preparation of pure lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said process comprising the steps of:
a) condensing protected amine compound of Formula VI with acid protected compound of Formula VII or its pharmaceutical acceptable salt, to give protected compound of Formula VIII,

wherein PG is an amine protecting group, and R is an acid protecting group;
b) de-protecting amine group of compound of Formula VIII in presence of acid followed by hydrolysis in presence of base, in absence of alcohol to give compound of Formula III or pharmaceutically acceptable salt thereof;

c) purifying compound of Formula III in suitable solvent, wherein said Formula III is free of compound of Formula VIII,

wherein, PG is an amine protecting group, and R is an acid protecting group;
d) reacting compound of Formula III with benzofuran-6-carboxylic acid of Formula IV in presence of a condensing agent to give crude lifitegrast, wherein said benzofuran-6-carboxylic acid is optionally converted to benzofuran-6-carbonyl chloride,
; and
d) purifying and isolating the pure lifitegrast wherein said lifitegrast is substantially free from compound of Formula I,
.

In a preferred embodiment, the solvent used for condensation of compound of Formula III with compound of Formula IV is selected from dichloromethane (DCM), dichlorobenzene, dichloroethane, ethyl acetate (EtOAc), n-butyl acetate, isopropyl acetate, n-propyl acetate, propenyl acetate, pentyl acetate, acetonitrile, water or mixture thereof. Most preferably, the solvent used in above said condensation reaction is dichloromethane.

In one another embodiment, compound of Formula II is prepared by reacting compound of Formula III with benzofuran-6-carbonyl chloride wherein said benzofuran-6-carbonyl chloride is prepared insitu from benzofuran-6-carboxylic acid of Formula IV.

In one another embodiment, compound of Formula II is prepared by reacting compound of Formula III with benzofuran-6-carboxylic acid of Formula IV in presence of suitable condensing reagent.

In another embodiment, the process of de-protection of amine group of compound of Formula VI is performed in presence of acid selected from dilute hydrochloric acid, dioxane hydrochloric acid, methanesulfonic acid, and trifluoro acetic acid.

In another embodiment, the solvent used for conducting deprotection of amine group of compound of Formula VI is selected from diethyl ether, tetrahydrofuran (THF), dioxane, methyl tetrahydrofuran (Me-THF), acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, acetonitrile and mixture thereof.

In further embodiment, the compound of Formula III may be purified and crystallized before proceeding to next step of condensation with compound of Formula IV to get lifitegrast.

In further embodiment, the compound of Formula III is purified and isolated before proceeding to next step of condensation with compound of Formula IV, wherein said Formula III is free of compound of Formula VIII.

In one another embodiment, the present invention provides a novel process for the preparation of pure lifitegrast of Formula II substantially free from compound of Formula I, wherein said process comprises the steps of:
a) preparation of 2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxylic acid of Formula IX,

by condensation of benzofuran-6-carbonyl chloride with 5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxylic acid of Formula X in presence of acylating agent and base;

b) condensation of compound of Formula IX with (S)-2-amino-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula XI or its pharmaceutical acceptable salt,

to give lifitegrast of Formula I; and
c) purifying lifitegrast of Formula I.

In further embodiment, it is provided that the compound of Formula IX can be prepared either by the process of the present invention or as per the disclosure of the prior published references.

In yet another embodiment, the present invention provides pure lifitegrast of Formula II wherein said process comprising the steps of:
(a) adding crude lifitegrast to a suitable solvent system comprising one or more solvent wherein atleast one solvent is water;
(b) adding aqueous sodium hydroxide to the solvent system;
(c) adjusting pH between 2 to 5 to get precipitates; and
(d) filtering the precipitates and washing with water to get lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said compound of Formula I is less than about 0.2% w/w relative to lifitegrast by area percentage of HPLC.

In another embodiment, the solvent system comprises of one or more solvents wherein atleast one solvent is water. Moreover the solvents are selected from the group comprising of halogenated solvents such as dichloromethane (DCM), dichlorobenzene, dichloroethane; esters such as ethyl acetate (EtOAc), n-butyl acetate, isopropyl acetate, n-propyl acetate, propenyl acetate, pentyl acetate; ethers such as diethyl ether, tetrahydrofuran (THF), dioxane, methyl tetrahydrofuran (Me-THF), methyl ethyl ether; ketones such as acetone, methyl ethyl ketone; organic amines such as secondary and tertiary amines; other solvents such as acetonitrile, xylene, toluene, water; and mixture thereof.

In a preferred embodiment, the solvent system consists of water and/or solvent selected from dichloromethane, ethyl acetate, n-butyl acetate, propenyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, diethyl ether, methyl ethyl ether, and acetonitrile.

Another embodiment of the present invention provides a process of preparing substantially pure lifitegrast by reacting crystalline (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III with benzofuran-6-carbonyl chloride or benzofuran-6-carboxylic acid of Formula IV, wherein said compound of Formula III is characterized by X-ray powder diffraction pattern comprising peaks at about 9.55, 12.44, 17.93, 19.57, 20.97, 23.98±0.2o2?.

In a preferred embodiment, (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III is characterized by X-ray powder diffraction pattern consisting peaks at about 4.71, 9.55, 10.36, 12.44, 12.81, 16.22, 17.93, 19.00, 19.57, 20.16, 20.97, 21.39, 22.48, 23.12, 23.98, 26.39, 30.14, 31.73, 33.33, and 36.88 ±0.2°?.

In another preferred embodiment, (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III is characterized by Differential Scanning Calorimetry (DSC) plot having peak onset at about 297.47oC and endotherm peak at about 305.17oC.

In further embodiment, the present invention further relates to a composition comprising lifitegrast of Formula II substantially free from compound of Formula I, along with at least one pharmaceutically acceptable excipients thereof.

In one more embodiment, present invention provides use of compound of Formula II as prepared by the process of the present invention, as a LFA-1 inhibitor and for the treatment of dry eye disease.

In one more embodiment, present invention provides use of compound of Formula I for the identification and the quantification of itself in the lifitegrast of Formula II.

In other embodiment, the lifitegrast as prepared by the process of the present invention is isolated with purity of 99.5% and above and preferably, 99.8% and above and most preferably with purity of 99.9% and above.

The present invention is explained below by way of examples. However, the examples are provided as one of the possible way to practice the invention and should not be considered as limitation of the scope of the invention.

EXAMPLES:

Example 1: Synthesis of Lifitegrast
Charged 1-benzofuran-6-carboxylic acid (5.0 g) in dichloromethane and added thionyl chloride (4.5 g) followed by stirring to get clear solution. The solvent was removed under reduced pressure. Methylene chloride (20 ml) was charged to the residue. The acid chloride, in methylene chloride (dichloromethane) was added slowly to a solution of (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid (13.8 g) and diisopropylethylamine (10 ml) below 5°C. Reaction mass was stirred at 0-5°C till completion of reaction. Reaction mass was then quenched with water 25ml. Layers were separated and organic layer washed with sodium bicarbonate solution. Organic layer concentrated to get crude Lifitegrast. Crude lifitegrast thus obtained was then recrystallized in acetone to get 13 g of pure lifitegrast with 72.8% yields.

Example 2: Synthesis of Lifitegrast
Charged 1-benzofuran-6-carboxylic acid (10 g), HOBt (12.5 g) and EDC.HCl (17.75 g) in THF (60 ml). and added diisopropyl ethylamine (22.2 g). Reaction mass was cooled to 0-5°C followed by addition of (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid (28.5g) lot wise at -10°C. Raised the temperature of reaction mass to room temperature. After completion of reaction, water (100 ml) and MDC (100 ml) were added. Stirred and separated the layers. Organic layer so obtained was washed with brine and 10% sodium carbonate solution. Organic layer was distilled to get crude lifitegrast which was then purified in acetone and methanol to get pure lifitegrast (31.2 g, 83.8%).

Example 3: Synthesis of Lifitegrast
Charged 3.6 g of 1-benzofuran-6-carboxylic acid in dichloromethane and added oxalyl chloride (3.44g) and stirred for 5-8hrs at 0-10oC under nitrogen and added mixture of (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid (10.0g) and sodium hydroxide solution (NaOH 4.24 g + 50.0 ml water) in 50 ml of dichloromethane at temperature of -5 to 0oC. Stirred the reaction mass for 30-60 min at -5 to 0oC, and then added conc. HCl solution to adjust the pH to 1-2. Stirred the reaction mass for 10-15 minutes followed by the separation of aqueous and dichloromethane layers. Seeded the dichloromethane layer and stirred for 30 min and then charged acetonitrile (50 ml) and stirred for 10-15 hr at 20-25oC. Filtered the solid material and washed with acetonitrile to get crude lifitegrast (10-12g).

Example 4: Purification of Lifitegrast
Charged acetonitrile (150ml) and 10g of crude lifitegrast followed by heating to 80-85oC. Stirred the solution at 80-85oC for 1h and then slowly cooled to 20-25oC. Stirred for 1-4hr at 20-25oC and filtered the solid material followed by washing with acetonitrile (20ml). Dried the material at 40-45oC under vacuum for 4-8 hrs.

Example 5: Purification of Lifitegrast
Charged 150 ml of water to 10g of lifitegrast and added 10% caustic solution. Stirred the reaction mass at room temperature for 1 hr. Added conc. HCl solution to adjust the pH to less than 1.0 at 20-25oC. Stirred for 1-4 hr at 20-25oC, filtered the solid material and washed with water (20ml). Dried the solid under vacuum at 40-50oC to get pure lifitegrast.

Example 6: Preparation of (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I:

Step 1: Preparation of (S)-2-(2-(2-(tert-butoxycarbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula XIII (PG=Boc):
Charged 10g of (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid in 30 ml of dimethyl formamide to round bottom flask and added 12.0g of HATU and 18.5g of diisopropyl ethyl amine followed by addition of 14.3 g of 2-(tert-butoxycarbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxylic acid and stirred the reaction mass at room temperature till completion of reaction. After completion of reaction, acidified with dilute hydrochloric acid and extracted the compound in ethyl acetate (3x). Collected the organic layer and concentrated under vacuum to get 20g of desired compound.

Step 2: Preparation of (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxa mido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula XIV:
Reacted 20g of (S)-2-(2-(2-(tert-butoxycarbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula XIII with 20 ml of concentrated hydrochloric acid in DM water: 1,4-dioxane at room temperature. After completion of reaction, adjusted the pH to 6-8 and filtered the precipitates so obtained. Dried the solid to get 5.4g of desired compound.

Step 3: Preparation of (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I:
Charged 2.4g of benzofuran-6-carboxylic acid in round bottom flask and added 2.2g of oxalyl chloride in 100ml of dichloromethane and added catalytic amount of dimethyl formamide. Stirred the reaction mass at room temperature till completion of reaction. Reaction mass was distilled and further diluted with dichloromethane. The reaction mass so obtained is added to a reaction mixture containing 11.2 g of (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula XIV in water and sodium hydroxide solution at 0-5oC. Stirred the reaction mass so obtained at room temperature and after completion of reaction, acidified the reaction mixture with 10.0 ml of concentrated hydrochloric acid and extracted the compound with dichloromethane. Distilled the organic layer to get 5.4g of crude compound of Formula I.

Step 4: Purification of compound of Formula I:
Crude compound obtained in step 3 was purified by Teledyne Preparative Reverse Phase Chromatography by Gradient Method. Pure fractions were collected and distilled to get 1.3g of pure compound of Formula I.

CLAIMS:WE CLAIM:
1. Pure lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroiso quinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydro isoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I, wherein said compound of Formula I is less than about 0.2% w/w relative to lifitegrast by area percentage of HPLC,
.

2. A process for the preparation of pure lifitegrast substantially free from (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula I, wherein said process comprising the steps of:
a) condensing protected amine compound of Formula VI with acid protected compound of Formula VII or its pharmaceutical acceptable salt, to give protected compound of Formula VIII,

wherein PG is an amine protecting group, and R is an acid protecting group;
b) de-protecting amine group of compound of Formula VIII in presence of acid followed by hydrolysis in presence of base, in absence of alcohol to give compound of Formula III or pharmaceutically acceptable salt thereof;

c) purifying compound of Formula III in suitable solvent, wherein said Formula III is free of compound of Formula VIII,

wherein, PG is an amine protecting group, and R is an acid protecting group;
d) reacting compound of Formula III with benzofuran-6-carboxylic acid of Formula IV in presence of a condensing agent to give crude lifitegrast, wherein said benzofuran-6-carboxylic acid is optionally converted to benzofuran-6-carbonyl chloride,
; and
d) purifying and isolating the pure lifitegrast wherein said lifitegrast is substantially free from compound of Formula I,
.

3. The process as claimed in claim 2, wherein said condensing agent is selected from the group comprising of 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), N,N'-Dicyclohexylcarbodiimide (DCC), N-[(Dimethylamino)-1H-1,2,3-triazolo-[4,5-b]pyridin-1-ylmethylene]-N-methylmethanaminium hexafluorophosphate N-oxide (HATU), Hydroxybenzotriazole (HOBt), Hexafluorophosphate Benzotriazole Tetramethyl Uronium (HBTU), O-(Benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), thionyl chloride, oxalyl chloride, and phosphorus oxychloride.

4. The process as claimed in claim 2, wherein said aqueous solution of base is aqueous solution of sodium hydroxide.

5. The process as claimed in claim 2, wherein said solvent used in step (b) comprises of a solvent system having one or more solvent, and wherein atleast one solvent is water.

6. The process as claimed in claim 2, wherein said lifitegrast is isolated with purity of 99.5% and above.

7. A process for preparation of (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I,
,
wherein said process comprising the steps of:
a) reacting (S)-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula III with compound of Formula VI to give N-protected (S)-2-(5,7-dichloro-2-(5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-1,2,3,4-tetrahydroisoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl) propanoic acid of Formula XIII,

;
wherein PG is a protecting group; and
b) converting compound of Formula XIII to (S)-2-(2-(2-(benzofuran-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydroisoquinoline-6-carbonyl)-5,7-dichloro-1,2,3,4-tetrahydro isoquinoline-6-carboxamido)-3-(3-(methylsulfonyl)phenyl)propanoic acid of Formula I in presence of suitable reagent,
,
wherein said compound of Formula I is used as reference standard for the identification and the quantification of itself in the lifitegrast.

8. The process as claimed in claim 7, wherein said compound of Formula III is purified before condensing with compound of Formula IV or VI, wherein said Formula III is free of compound of Formula VIII,

wherein, PG is an amine protecting group, and R is an acid protecting group.

9. A composition comprising lifitegrast of Formula II substantially free from compound of Formula I, along with at least one pharmaceutically acceptable excipients thereof.

10. Compound of Formula I,
,
wherein said compound of Formula I is used as reference standard for the identification and the quantification of itself in the lifitegrast.