Field of the Invention:

The present invention provides novel processes for the preparation of 2-[4-(2-{4-[l-(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl}ethyl)phenyl]-2-methylpropanoic acid represented by the following structural formula-1. The present invention also provides novel intermediate compounds useful for the preparation of compound of formula-1.

Background of the Invention:

2-[4-(2- {4-[ 1 -(2-ethoxyethyl> 1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2-methylpropanoic acid, commonly known as Bilastine is an antihistamine drug for the treatment of allergic rhinoconjunctivitis and urticaria (hives). It exerts its effect as a selective histamine HI receptor antagonist and has potency similar to cetirizine and is superior to Fexofenadine. US5877187A first discloses the synthesis of 2-[4-(2-{4-[l-(2-ethoxyethyl)-lH-benzimidazol-2-yl]-l-piperidinyl} ethyl)phenyl]-2-methylpropanoic acid. The process disclosed in the said patent is schematically represented in scheme-A. The disclosed process involves the reaction of the benzimidazole intermediate with tosylated oxazole intermediate in presence of sodium carbonate followed by reaction of obtained intermediate compound with l-chloro-2-ethoxyethane to provide oxazole protected Bilastine. Cleavage of the said oxazole ring by treating it with 3N HC1 provides Bilastine.

The above process has several disadvantages in that it involves the preparation of an intermediate compound having oxazole group and then cleavage of oxazole ring by hydrolyzing the compound in presence of acid and this making the whole process complicated. The above process involves the usage of alkali metal hydrides such as sodium hydride as a base. Usage of alkali metal hydrides is not advisable on commercial scale in safety point of view. Further, the above process produces Bilastine in very low yields with number of by-products. In view of all these disadvantages, there is a significant need in the art to develop a novel process for the preparation of 2-[4-(2-{4-[l-(2-ethoxyethyl)-lH-benzimidazol-2-yl]-l-piperidinyl}ethyl)phenyl]-2-methyl propanoic acid. The present inventors overcome all the disadvantages associated with the prior-art process by adopting a novel process for the preparation of 2-[4-(2-{4-[l-(2-ethoxyethyi)-lH-benzimidazol-2-yl]-l-piperidinyl}ethyl)phenyl]-2-methylpropanoic acid which is able to produce highly pure Bilastine with better yields.

Brief description of the invention:

The first aspect of the present invention is to provide a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl) phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH- benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-1-yl) acetyl)phenyl)-2-methylpropanoate compound of formula-5,

c) hydrolyzing the compound of formula-5 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl) phenyl)-2-methylpropanoic acid compound of formula-6,

d) reducing the compound of formula-6 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

The second aspect of the present invention is to provide a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl) phenyl]-2-methylpropanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-1-yl) acetyl)phenyl)-2-methylpropanoate compound of formula-5,

c) reducing the compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7,

d) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

The third aspect of the present invention is to provide a process for the preparation of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3, comprising of reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3. The fourth aspect of the present invention is to provide a process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2- methyl propanoic acid compound of formula-1, comprising of;

a) Reducing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-1-yl) acetyl)phenyl)-2-methylpropanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8,

b) reducing the compound of formula-8 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl) phenyl)-2-methylpropanoate compound of formula-7,

c) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

The fifth aspect of the present invention is to provide a process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Reducing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8,

b) hydrolyzing the compound of formula-8 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1-yl)-l-hydroxy ethyl)phenyl)-2-methylpropanoic acid compound of formula-9,

c) reducing the compound of formula-9 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

The sixth aspect of the present invention is to provide a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl}-1 -piperidinyl} ethyl) phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Hydrolyzing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl) phenyl)-2-methylpropanoic acid compound of formula-6,

b) reducing the compound of formula-6 with a suitable reducing agent in a suitable solvent to provide 2-(4-(2-(4-( 1 -(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxy ethyl)phenyl)-2-methylpropanoic acid compound of formula-9,

c) reducing the compound of formula-9 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

The seventh aspect of the present invention is to provide a process for the preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10, which is an useful intermediate in the synthesis of compound of formula-1, comprising of reducing the methyl 2-(4-(2 chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with a suitable reducing agent in a suitable solvent optionally in presence of a Lewis acid to provide compound of formula-10. The eighth aspect of the present invention is to provide a novel process for the preparation of methyl 2-(4-(2-(4-(l-(2-emoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7, comprising of;

a) Reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with a suitable reducing agent in a suitable solvent optionally in presence of a Lewis acid to provide methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10,

b) reacting the compound of formula-10 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-Lh benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide compound of formula-7.

The ninth aspect of the present invention is to provide novel intermediate compounds which are useful for the preparation of 2-[4-(2-{4-[l-(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-l-piperidinyl}ethyl)phenyl]-2-methylpropanoic acid compound of formula-1.

Detailed description of the Invention:

The term "suitable solvent" used in the present invention refers to "hydrocarbon solvents" such as n-hexane, n-heptane, cyclohexane, petroleum ether, benzene, toluene, xylene and the like; "ether solvents" such as dimethyl ether, diethyl ether, diisopropyl ether, methyl tert-butyl ether, 1,2-dimethoxy ethane, tetrahydrofuran, 1,4-dioxane and the like; "ester solvents" such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, tert-butyl acetate and the like; "polar-aprotic solvents" such as dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone (NMP) and the like; "chloro solvents" such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride and the like; "ketone solvents" such as acetone, methyl ethyl ketone, methyl isobutyl ketone and the like; "nitrile solvents" such as acetonitrile, propionitrile, isobutyronitrile and the like; "alcohol solvents" such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, tert-butanol, ethane- 1,2-diol, propane-1,2-diol and the like; "polar solvents" such as water; acetic acid, formic acid or their mixtures.

The term "suitable base" used in the present invention refers to inorganic bases selected from "alkali metal carbonates" such as sodium carbonate, potassium carbonate, lithium carbonate, cesium carbonate and the like; "alkali metal bicarbonates" such as sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, cesium bicarbonate and the like; "alkali metal hydroxides" such as sodium hydroxide, potassium hydroxide, lithium hydroxide and the like; "alkali metal alkoxides" such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, sodium tertbutoxide, potassium tert.butoxide, lithium tertbutoxide and the like; alkali metal hydrides such as sodium hydride, potassium hydride, lithium hydride and the like; alkali metal amides such as sodium amide, potassium amide, lithium amide and the like; ammonia, alkali metal and alkaline earth metal salts of acetic acid such as sodium acetate, potassium acetate, magnesium acetate, calcium acetate and the like; "organic bases" like dimethylamine, diethylamine, diisopropyl amine, diisopropylethylamine, di n-butylamine, diisobutylamine, triethylamine, tributylamine, tert-butyl amine, pyridine, 4-dimethylaminopyridine (DMAP), l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), l,5-diazabicyclo[4.3.0]non-5-ene(DBN), N-methylmorpholine (NMM), 1,4-diazabicyclo[2.2.2] octane (DABCO), 2,6-lutidine, lithium diisopropylamide; "organolithium bases" such as n-butyllithium, organosilicon bases such as lithium hexamethyldisilazide (LiHMDS), sodium hexamethyldisilazide (NaHMDS), potassium hexamethyldisilazide (KHMDS) or their mixtures.

The first aspect of the present invention provides a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)- lH-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2- methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 wherein, 'Et' represents ethyl group; in presence of a suitable base in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)acetyl)phenyl)-2-methyl propanoate compound of formula-5,

c) hydrolyzing the compound of formula-5 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl) phenyl)-2-methylpropanoic acid compound of formula-6,

d) reducing the compound of formula-6 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

Wherein, in step-a) the suitable Lewis acid is selected from but not limited to I aluminum chloride, aluminum bromide, boron trifluoride, boron tribromide, tin tetrachloride, tin tetrabromide, stannous chloride (SnCb), ferric chloride (FeCU), zinc chloride (ZnCfe), titanium tetrachloride (TiCL») or mixture or hydrates thereof;

In step-b) the suitable base is selected from organic bases, inorganic bases;

In step-c) the suitable base is selected from hydroxides, alkoxides, carbonates and > bicarbonates of alkali metals;

In step-d) the suitable reducing agent is selected from but not limited to trialkyl silanes such as trimethylsilane, triethylsilane optionally in combination with a Lewis acid such as defined in step-a) or trifluoroacetic acid or BF3-etherate; sodium borohydride optionally in combination with BF3-etherate, hydrazine (Wolff-Kishner reduction), Zn- I Hg/HCl (Clemmensen reduction); In step-a) to step-d) the suitable solvent is selected from chloro solvents, ketone solvents, ether solvents, ester solvents, hydrocarbon solvents, polar solvents, polar-aprotic solvents, nitrile solvents, alcohol solvents, acetic acid, formic acid or their mixtures. The l-(2-emoxyemyl)-2-(piperidm-4-yl)-lH-benzo[d]irnidazole compound of formula-4 utilized in step-b) of the first aspect of the present invention can be synthesized by any of the processes known in the art such as Drugs of the future, 2010, 35(2), 98-105, US20110009636A1, Synthetic Communications, 41, 1394-1402, 2011 or it can be synthesized by the process disclosed in the foregoing examples.

The methyl 2-methyl-2-phenylpropanoate compound of formula-2 can be prepared by any of the processes known in the art. The second aspect of the present invention provides a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl) phenyl] -2-methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5,

c) reducing the compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-emoxyemyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7,

d) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

Wherein, in step-a) and step-b) the suitable Lewis acid, the suitable base and the suitable solvent are same as defied for step-a) and step-b) respectively of the first aspect of the present invention; In step-c) the suitable reducing agent and the suitable solvent are same as defined for step-d) of the first aspect of the present invention; In step-d) the suitable base and the suitable solvent are same as defined for step-c) of the first aspect of the present invention. A preferred embodiment of the present invention provides a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl) phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of aluminium chloride in dichloromethane to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of potassium carbonate in acetone to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5,

c) reducing the compound of formula-5 with triethylsilane in dichloromethane in presence of titanium tetrachloride to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-1 -yl)ethyl)phenyl)-2-methylpropanoate of formula-7,

d) hydrolyzing the compound of formula-7 in presence of sodium hydroxide in ethanol to provide compound of formula-1.

The third aspect of the present invention provides a process for the preparation of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3, comprising of reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide compound of formula-3, wherein the suitable Lewis acid and the suitable solvent are same as defined for step-a) of the first aspect of the present invention. A preferred embodiment of the present invention provides a process for the preparation of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3, comprising of reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of aluminium chloride in dichloromethane to provide compound of formula-3.

The fourth aspect of the present invention provides a process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2-methylpropanoic acid compound of formula-1, comprising of;

i) Reducing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-1-yl) acetyl)phenyl)-2-methylpropanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8,

b) reducing the compound of formula-8 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l- yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7,

c) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

Wherein in step-a) the suitable reducing agent is selected from but not limited to 5 trialkyl silanes such as trimethylsilane, triethylsilane optionally in combination with a suitable Lewis acid or trifluoroacetic acid or BF3-etherate; trichlorosilane, sodium borohydride optionally in combination with BF3-etherate, diborane, potassium borohydride, sodium cyanoborohydride, lithium borohydride, diisobutylaluminium hydride (DIBAL), lithium triethylborohydride (UEt^BH), L-selectride (lithium tri-sec butyl(hydrido)borate(l-)) ) and the like; In step-b) the suitable reducing agent is selected from trialkyl silanes such as trimethylsilane, triethylsilane optionally in combination with a suitable Lewis acid or trifluoroacetic acid or BF3-etherate, Pd/C, Pt/C and the like; The suitable solvent used in step-a) and step-b) is selected from ketone solvents, 5 hydrocarbon solvents, ether solvents, ester solvents, polar solvents, alcohol solvents, polar-aprotic solvents, chloro solvents, nitrile solvents, acetic acid, formic acid or their mixtures; In step-c) the suitable base and the suitable solvent are same as defined for step-c) of the first aspect of the present invention.

In the above process, the hydroxy group of compound of formula-8 can be optionally converted into easily leaving groups such as methane sulfonate, ethane sulfonate, benzene sulfonate, toluene sulfonate or the like followed by reduction of the obtained compound with a suitable reducing agent in a suitable solvent provides compound of formula-7. The fifth aspect of the present invention provides a process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2-methylpropanoic acid compound of formula-1, comprising of;

a) Reducing the methyl 2-(4-(2-(4-(l -(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8,

b) hydrolyzing the compound of formula-8 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1-yl)-l-hydroxy ethyl)phenyl)-2-methylpropanoic acid compound of formula-9,

c) reducing the compound of formula-9 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

In step-a) the suitable reducing agent and the suitable solvent are same as defined for step-a) of the fourth aspect of the present invention; In step-b) the suitable base and the suitable solvent are same as defined for step-c) of the first aspect of the present invention; In step-c) the suitable reducing agent and the suitable solvent are same as defined for step-b) of the fourth aspect of the present invention. The sixth aspect of the present invention provides a novel process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl} ethyl)phenyl]-2- methyl propanoic acid compound of formula-1, comprising of;

a) Hydrolyzing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5 in presence of a suitable base in a suitable solvent to provide 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl) phenyl)-2-methylpropanoic acid compound of formula-6,

b) reducing the compound of formula-6 with a suitable reducing agent in a suitable solvent to provide 2-(4-(2-(4-( 1 -(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxy ethyl)phenyl)-2-methylpropanoic acid compound of formula-9,

c) reducing the compound of formula-9 with a suitable reducing agent in a suitable solvent to provide compound of formula-1.

In step-a) the suitable base and the suitable solvent are same as defined for step-c) of the first aspect of the present invention; In step-b) the suitable reducing agent and the suitable solvent are same as defined for step-a) of the fourth aspect of the present invention; In step-c) the suitable reducing agent and the suitable solvent are same as defined for step-b) of the fourth aspect of the present invention. The hydroxy group of compound of formula-9 obtained in step-b) of the fifth and sixth aspects of the present invention can be optionally converted into easily leaving groups such as methane sulfonate, ethane sulfonate, benzene sulfonate, toluene sulfonate or the like followed by reduction of the obtained compound with a suitable reducing agent in a suitable solvent provides compound of formula-1. The seventh aspect of the present invention provides a process for the preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10, which is an useful intermediate in the synthesis of compound of formula-1, comprising of reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate of formula-3 with a suitable reducing agent in a suitable solvent to provide compound of formula-10.

Wherein, the suitable reducing agent and the suitable solvent are same as defined for step-d) of the first aspect of the present invention. A preferred embodiment of the present invention provides a process for the preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10, comprising of reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with triethylsilane in dichloromethane in presence of titanium tetrachloride to provide compound of formula-10. The eighth aspect of the present invention provides a novel process for the preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7, comprising of;

a) Reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10,

b) reacting the compound of formula-10 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide compound of formula-7.

Wherein, in step-a) the suitable reducing agent and the suitable solvent are same as defined for step-d) of the first aspect of the present invention;
In step-b) the suitable base and the suitable solvent are same as defined for step-b) of the first aspect of the present invention. A preferred embodiment of the present invention provides a novel process for the preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7, comprising of;

a) Reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with triethylsilane in dichloromethane in presence of titanium tetrachloride to provide methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10,

b) reacting the compound of formula-10 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of sodium carbonate in toluene to provide compound of formula-7.

The ninth aspect of the present invention provides novel intermediate compounds useful for the preparation of 2-[4-(2-{4-[l-(2-ethoxyethyl)-lH-benzimidazol-2-yl]-l-piperidinyl}ethyl)phenyl]-2-methylpropanoic acid compound of formula-1. The novel intermediate compounds are represented by the structural formulae given below; Wherein, 'Me' represents methyl group and 'Et' represents ethyl group. The best mode of carrying out the present invention is illustrated by the below mentioned examples. These examples are provided as illustration only and hence should not be construed as limitation to the scope of the invention. Examples:

Example-1: Preparation of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate (Formula-3) Aluminium chloride (78.4 gm) was slowly added to a pre-cooled solution of methyl 2-methyl-2-phenylpropanoate compound of formula-2 (50 gm) in dichloromethane (1500 ml) at 0-5°C. Chloroacetyl chloride (38 gm) was slowly added to the reaction mixture at 0-5°C and stirred for 15 min at the same temperature. Raised the temperature of the reaction mixture to 25-30°C and stirred for 10 hrs at the same temperature. After completion of the reaction, the reaction mixture was slowly added to pre-cooled 2N hydrochloric acid solution at 0-5°C and stirred for 10 min at the same temperature. Both the organic and aqueous layers were separated and the aqueous layer was extracted with dichloromethane. The combined organic layer was washed with 10% aqueous sodium bicarbonate solution followed by with aqueous sodium chloride solution. Dried the organic layer over sodium sulfate and distilled off the solvent completely under reduced pressure to get the title compound. Yield: 55.0 gm.

Example-2: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate(FormuIa-5) A mixture of l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 (2 gm), acetone (30 ml) and potassium carbonate (1.51 gm) was stirred for 2 hrs at 25-30°C. A solution of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 (1.86 gm) in acetone (10 ml) was slowly added to the reaction mixture at 25-30°C and stirred for 10 hrs at the same temperature. After completion of the reaction, water and ethyl acetate were added to the reaction mixture. Both the organic and aqueous layers were separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed with 10% aqueous sodium bicarbonate solution followed by with aqueous sodium chloride solution. Dried the organic layer over sodium sulfate and distilled off the solvent completely under reduced pressure to get the title compound. Yield: 3.2 gm.

Example-3: Preparation of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methyIpropanoate (Formula-3) Aluminium chloride (112.7 gm) and dichloromethane (500 ml) were added to methyl 2-methyl-2-phenylpropanoate compound of formula-2 (50 gm) at 25-30°C. Cooled the reaction mixture to -10°C to -5°C. Chloroacetyl chloride (34 ml) was slowly added to the reaction mixture at -10°C to -5°C. Raised the temperature of the reaction mixture to 25-30°C and stirred for 12 hrs at the same temperature. Quenched the reaction mixture with water. Both the organic and aqueous layers were separated and the aqueous layer was extracted with dichloromethane. Combined the organic layers and washed with aqueous sodium bicarbonate solution followed by with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 70.5 gm.

Example-4: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)acetyl)phenyl)-2-methylpropanoate (Formula-5) A mixture of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 (14 gm), l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 (15 gm), acetone (150 ml) and potassium carbonate (15 gm) was stirred for 6 hrs at 25-30°C. Water and methyl tert-butyl ether were added to the reaction mixture and stirred for 10 min. Both the organic and aqueous layers were separated. 2N HC1 solution was added to the organic layer and stirred for 5 min. Both the organic and aqueous layers were separated and the aqueous layer was neutralized using potassium carbonate. Extracted the aqueous layer with methyl tert-butyl ether and dried the organic layer over sodium sulfate. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 21.5 gm.

Example-5: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate (FormuIa-7) Titanium tetrachloride (19.3 gm) was slowly added to a pre-cooled mixture of methyl 2-(4-(2-(4-( 1 -(2-ethoxyethyl> 1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)acetyl)phenyl)-2-methyl propanoate compound of formula-5 (10 gm) and dichloromethane (200 ml) at 0-5°C. Raised the temperature of the reaction mixture to 25-3 0°C, triethylsilane (9 gm) was added and stirred the reaction mixture for 4 hrs at the same temperature. Quenched the reaction mixture with water at below 10°C. Both the organic and aqueous layers were separated and the organic layer was washed with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 9.0 gm.

Example-6: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)-l-hydroxyethyl)phenyl)-2-methylpropanoate(Formula-8) Sodium borohydride (1.54 gm) was slowly added to a pre-cooled mixture of methyl 2-(4-(2-(4-( 1 -(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)acetyl)phenyl)-2-methyl propanoate compound of formula-5 (10 gm) and methanol (50 ml) under nitrogen atmosphere at -10°C to -15°C and stirred the reaction mixture for 2 hrs at the same temperature. 12% aqueous sodium bicarbonate solution and dichloromethane were slowly added to the reaction mixture at -10°C to -15°C. Slowly raised the temperature of the reaction mixture to 25-30°C and stirred for 30 min at the same temperature. Both the organic and aqueous layers were separated and extracted the aqueous layer with dichloromethane. Combined the organic layers and washed with 12% aqueous sodium bicarbonate solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 9.5 gm.

Example-7: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate(Formula-7) Methane sulfonyl chloride (1.4 gm) was slowly added to a mixture of methyl 2-(4-(2-(4-( 1 -(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methyl propanoate compound of formula-8 (5 gm), dichloromethane (35 ml) and triethylamine (1.25 gm) at 25-30°C and stirred the reaction mixture for 3 hrs at the same temperature. Water and dichloromethane were added to the reaction mixture. Both the organic and aqueous layers were separated and the aqueous layer was extracted with dichloromethane. Combined the organic layers and washed with 10% aqueous sodium chloride solution. Dried the organic layer over sodium sulfate and distilled off the solvent completely under reduced pressure. Dissolved the obtained compound in methanol (100 ml) at 25-30°C and 5% Pd/C (5 gm) was added. Transferred the obtained reaction mixture into an autoclave vessel and 4Kg/Cm2 hydrogen gas pressure was applied. Heated the reaction mixture to 40-45°C and stirred for 14 hrs at the same temperature. Cooled the reaction mixture to 25-30°C and released the hydrogen gas pressure. Filtered the reaction mixture through hyflow bed and washed with methanol. Distilled off the solvent completely from the filtrate and dried the obtained material to get the title compound. Yield: 3.9 gm.

Example-8: Preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate (Formula-10) Titanium tetrachloride (37.2 gm) was slowly added to a pre-cooled mixture of methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 (10 gm) and dichloromethane (200 ml) at 0-5°C. Raised the temperature of the reaction mixture to 25-30°C, triethylsilane (17.3 gm) was added and stirred the reaction mixture for 4 hrs at the same temperature. Quenched the reaction mixture with water at below 10°C. Both the organic and aqueous layers were separated and the organic layer was washed with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 9.5 gm.

Example-9: Preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazoI-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate (Formula-7) Sodium carbonate (2.7 gm) was added to a mixture of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10 (3.4 gm), l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 (3.5 gm) and toluene (35 ml) at 25-30°C. Heated the reaction mixture to 105-110°C and stirred for 12 hrs at the same temperature. Cooled the reaction mixture to 25-30°C, water was added and stirred for 15 min at the same temperature. Both the organic and aqueous layers were separated and the organic layer was washed with IN HC1 solution. Both the organic and aqueous layers were separated and the aqueous layer was neutralized using aqueous sodium carbonate solution. Extracted the aqueous layer with methyl tert-butyl ether and the organic layer was washed with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 3.0 gm.

Example-10: Preparation of tert-butyl 4-(lH-benzo[d]imidazol-2-yl)piperidine-l-carboxylate (Frormula-14) A mixture of benzene-1,2-diamine compound of formula-11 (100 gm), piperidine-4-carboxylic acid compound of formula-12 (131.2 gm) and polyphosphoric acid (600 gm) was heated to 115-120°C and stirred for 20 hrs at the same temperature. Cooled the reaction mixture to 80-85°C and quenched the reaction mixture with water. Cooled the reaction mixture to 10-15°C and basified using aqueous sodium hydroxide solution. Di.tert-butyl dicarbonate (222 gm) was slowly added to the reaction mixture at 10-15°C and stirred for 6 hrs at the same temperature. Filtered the precipitated solid, washed with water. Cyclohexane (1000 ml) was added to the obtained compound at 25-30°C. Heated the reaction mixture to 80-85°C and stirred for 40 min at the same temperature. Cooled the reaction mixture to 25-30°C and stirred for 40 min at the same temperature. Filtered the solid, washed with cyclohexane and dried the material to get the title compound. Yield: 230 gm.

Example-11: Preparation of tert-butyl 4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidine-l carboxy!ate(Formula-15) Tert-butyl 4-(lH-benzo[d]imidazol-2-yl)piperidine-l-carboxylate compound of frormula-14 (100 gm), sodium iodide (10 gm) and l-chloro-2-ethoxyethane (54 gm) were slowly added to a pre-heated mixture of dimethylsulfoxide (200 ml) and sodium hydroxide (39.8 gm) at 40-45°C. Heated the reaction mixture to 95-100°C and stirred for 3 hrs at the same temperature. Cooled the reaction mixture to 10-15°C and water was slowly added. Neutralized the reaction mixture using aqueous hydrochloric acid. Ethyl acetate was added to the reaction mixture and stirred for 20 min. Both the organic and aqueous layers were separated and the organic layer was washed with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure. Ethyl acetate (50 ml) was added to the obtained compound. Heated the reaction mixture to 60-65°C and stirred for 15 min at the same temperature. Cooled the reaction mixture to 40-45°C and petroleum ether (650 ml) was slowly added. Cooled the reaction mixture to 0-5°C and stirred for 10 min at the same temperature. Filtered the precipitated solid, washed with petroleum ether and dried to get the title compound. Yield: 93.0 gm.

Example-12: Preparation of l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole (Formula-4) A mixture of tert-butyl 4-(l-(2-emoxyemyl)-lH-benzo[d]imidazol-2-yl)piperidine-l-carboxylate compound of formula-15 (50 gm), hydrochloric acid (70 ml) and water (700 ml) was stirred for 6 hrs at 25-30°C. Neutralized the reaction mixture using aqueous ammonia solution. Sodium chloride was added to the reaction mixture and stirred for 10 min. Extracted the reaction mixture with n-butanol and distilled off n-butanol completely. Dichloromethane (500 ml) was added to the obtained compound at 25-3 0°C and stirred for 10 min at the same temperature. Filtered the reaction mixture and distilled off the solvent completely from the filtrate. Petroleum ether (250 ml) was added to the obtained compound at 25-30°C and stirred for 5 min at the same temperature. Filtered the solid, washed with petroleum ether and dried to get the title compound. Yield: 34.0 gm.

Example-13: Preparation of 2-[4-(2-{4-[l-(2-ethoxyethyI)-lH-benzimidazol-2-yl]-l piperidinyl}ethyl)phenyl]-2-methylpropanoic acid (Formula-1 A mixture of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-l-yl)ethyl)phenyl)-2 methylpropanoate compound of formula-7 (3 gm), sodium hydroxide (0.5 gm) and ethanol (21 ml) was heated to 65-70°C and stirred for 4 hrs at the same temperature. Water and dichloromethane were added to the reaction mixture and stirred for 15 min at the same temperature. Both the organic and aqueous layers were separated and the aqueous layer was neutralized using acetic acid. Extracted the aqueous layer with dichloromethane and the organic layer was washed with aqueous sodium chloride solution. Distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 1.3 gm.

Example-14: Purification of 2-[4-(2-{4-Il-(2-ethoxyethyl)-lH-benzimidazol-2-yl]-l-piperidinyl}ethyl)phenyl]-2-methylpropanoic acid (Formula-1) A mixture of 2-[4-(2-{4-[l-(2-emoxyethyl)-lH-benzimidazol-2-yl]-l-piperidinyl} ethyl) phenyl]-2-methylpropanoic acid compound of formula-1 (8 gm) and n-butanol (75 ml) was heated to 110-115°C and stirred for 10 min at the same temperature. Carbon (0.8 gm) was added to the reaction mixture and stirred for 30 min at the same temperature. Filtered the reaction mixture through hyflow bed and washed the hyflow bed with n-butanol. Cooled the reaction mixture to 5-10°C and stirred for 30 min at the same temperature. Filtered the solid, washed with n-butanol and dried the material to get pure title compound. Yield: 7.0 gm.

We Claim:

1. A process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl}ethyl)phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of a Lewis acid in a suitable solvent to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of a suitable base in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)acetyl)phenyl)-2-methyl propanoate compound of formula-5,

c) reducing the compound of formula-5 with a suitable reducing agent in a suitabl* solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7,

d) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

2. A process according to claim 1, wherein, in step-a) the suitable Lewis acid is selected from aluminum chloride, aluminum bromide, boron trifluoride, boron tribromide, tin tetrachloride, tin tetrabromide, stannous chloride (SnCk), ferric chloride (FeCla), zinc chloride (ZnCk), titanium tetrachloride (TiCU) or mixture or hydrates thereof; in step-b) the suitable base is selected from organic bases, inorganic bases; in step-c) the suitable reducing agent is selected from trialkyl silanes such as trimethylsilane, triethylsilane optionally in combination with a Lewis acid such as defined in step-a) or trifluoroacetic acid or BF3-etherate; sodium borohydride optionally in combination with BF3-etherate, hydrazine, Zn-Hg/HCl; in step-d) the suitable base is selected from hydroxides, alkoxides, carbonates and bicarbonates of alkali metals; in step-a) to step-d) the suitable solvent is selected from chloro solvents, ketone solvents, ether solvents, ester solvents, hydrocarbon solvents, polar solvents, polar-aprotic solvents, nitrile solvents, alcohol solvents, acetic acid, formic acid or their mixtures.

3. A process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 - piperidinyl}ethyl)phenyl]-2-methyl propanoic acid compound of formula-1, comprising of;

a) Reacting the methyl 2-methyl-2-phenylpropanoate compound of formula-2 with chloroacetyl chloride in presence of aluminium chloride in dichloromethane to provide methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate of formula-3,

b) reacting the compound of formula-3 with l-(2-ethoxyethyl)-2-(piperidin-4-yl)-lH-benzo[d]imidazole compound of formula-4 in presence of potassium carbonate in acetone to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-1 -yl)acetyl)phenyl)-2-methylpropanoate compound of formula-5,

c) reducing the compound of formula-5 with triethylsilane in dichloromethane in presence of titanium tetrachloride to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl)piperidin-l-yl)ethyl)phenyl)-2-methylpropanoate compound of formula-7,

d) hydrolyzing the compound of formula-7 in presence of sodium hydroxide in ethanol to provide compound of formula-1.

4. A process for the preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10, r^rr0Me Ct^^\J O Formula-10 comprising of reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with a suitable reducing agent in presence of a Lewis acid or BF3-etherate in a suitable solvent to provide compound of formula-10.

5. A process according to claim 4, wherein, the suitable reducing agent is selected from trialkyl silanes such as trimethylsilane, triethylsilane and sodium borohydride; the suitable solvent is selected from chloro solvents, ketone solvents, ether solvents, ester solvents, hydrocarbon solvents, polar solvents, polar-aprotic solvents, nitrile solvents, alcohol solvents, acetic acid, formic acid or their mixtures.

6. A process for the preparation of methyl 2-(4-(2-chloroethyl)phenyl)-2-methylpropanoate compound of formula-10, comprising of reducing the methyl 2-(4-(2-chloroacetyl)phenyl)-2-methylpropanoate compound of formula-3 with triethylsilane in dichloromethane in presence of titanium tetrachloride to provide compound of formula-10.

7. A process for the preparation of 2-[4-(2- {4-[ 1 -(2-ethoxyethyl)-1 H-benzimidazol-2-yl]-1 -piperidinyl}ethyl)phenyl]-2-methylpropanoic acid compound of formula-1, comprising of;

a) Reducing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-lH-benzo[d]imidazol-2-yl) piperidin-1-yl) acetyl)phenyl)-2-methylpropanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)- lH-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8,

b) optionally converting the hydroxy group of compound of formula-8 to a suitable leaving group,

c) reducing the compound of formula-8 or the compound obtained in step-b) with a suitable reducing agent in a suitable solvent to provide methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)ethyl)phenyl)-2-methyl propanoate compound of formula-7,

d) hydrolyzing the compound of formula-7 in presence of a suitable base in a suitable solvent to provide compound of formula-1.

8. A process for the preparation of methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1H-benzo[d]imidazol-2-yl)piperidin-1 -yl)-1 -hydroxyethyl)phenyl)-2-methylpropanoate compound of formula-8, comprising of reducing the methyl 2-(4-(2-(4-(l-(2-ethoxyethyl)-1 H-benzo[d]imidazol-2-yl)piperidin-1 -yl)acetyl)phenyl)-2-methyl propanoate compound of formula-5 with a suitable reducing agent in a suitable solvent to provide compound of formula-8.

9. A process according to claim 8, wherein, the suitable reducing agent is selected from trialkyl silanes optionally in combination with a suitable Lewis acid or trifluoroacetic acid or BF3-etherate; trichlorosilane, sodium borohydride optionally in combination with BF3-etherate, diborane, potassium borohydride, sodium cyanoborohydride, lithium borohydride, diisobutylaluminium hydride (DIBAL), lithium triethylborohydride (LiEtsBH), L-selectride; the suitable solvent is selected from chloro solvents, ketone solvents, ether solvents, ester solvents, hydrocarbon solvents, polar solvents, polar-aprotic solvents, nitrile solvents, alcohol solvents, acetic acid, formic acid or their mixtures.

10. Compounds having the structural formulae;