1. A process for the preparation of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl] phenyl]-, (1S) compound of formula-1 comprising: a) Reacting the compound of general formula-7 with suitable thiol reagent in presence of suitable Lewis acid in a suitable solvent to get the compound of general formula-8;
b) reacting the compound of general formula-8 with the compound of general formula-11 in presence of a suitable base in a suitable solvent to provide the compound of general formula-9;
c) deprotecting the product obtained in step-b) to provide the D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl]phenyl]-,(1S) compound of formula-1.
wherein, R1 is selected from C1-C5 straight or branched chain alkyl groups; Pg is selected from -C(O)OC1-C6 alkyl; optionally substituted -C(O)OC1-C6 aryl; optionally substituted -C1-C12 aryl(C1-C3)alkyl; optionally substituted C7-C11 aryl carbonyl; C1-C6 alkanoyl; C1-C6

alkylsulfonyl; Z is alkyl group (C1-4 carbon atoms) or aryl group (phenyl or naphthyl) substituted with one or more electron withdrawing groups.
2. The process according to claim 1, wherein, in step-a), the suitable thiol reagent is thiol or dithiol alcohol which is selected from decanethiol, dodecane thiol, cyclohexane thiol, cyclopentane thiol, cyclo butane thiol, thiophenol, methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, n-butanethiol, tert-butanthiol, furan-2-ylmethanethiol, ethandithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,3-butanedithiol, 1,4-butanedithiol; the suitable Lewis acid is selected from AlCl3, AlBr3, BCl3, TiCl4, FeCl3 and ZnCl2.
3. The process according to claim 1, wherein, in step-b), the suitable base is selected from “alkali metal hydroxides” such as lithium hydroxide, sodium hydroxide, potassium hydroxide and the like; “alkali metal carbonates” such as sodium carbonate, potassium carbonate, lithium carbonate and the like; “alkali metal bicarbonates” such as sodium bicarbonate, potassium bicarbonate, lithium bicarbonate and the like; “alkali metal hydrides” such as sodium hydride, potassium hydride, lithium hydride and the like; “alkali metal alkoxides” such as sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide and the like.
4. The process according to claim 1, wherein, in step-a) and step-b), the suitable solvent is selected from alcohol solvents such as methanol, ethanol, n-propanol, i-propanol, butanol; chloro solvents such as methylene chloride, chloroform, carbon tetrachloride; ketone solvents such as acetone, butanone; nitrile solvents such as acetonitrile, propionitrile, butyronitrile; ester solvents such as ethyl acetate, methyl acetate, butyl acetate; hydrocarbon solvents such as heptane, hexane, benzene, toluene, xylene; ether solvents such as diethyl ether, methyl tert-butyl ether, tetrahydrofuran, 1,4-diethyl ether or mixture thereof.
5. The process according to claim 1, wherein, the deprotection is carried out using suitable base or suitable mineral acid.
6. A process for the preparation of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-
tetrahydro-3-furanyl]oxy]phenyl]methyl] phenyl]-, (1S) compound of formula-1 comprising:
a) Reacting the compound of formula-7a with dodecanethiol / AlCl3 to provide compound of formula-8a;

b) reacting the compound of formula-8a with (R)-tetrahydrofuran-3-yl 4-nitrobenzenesulfonate in presence of K2CO3 / dimethylformamide to provide compound of formula-9a;
c) deprotecting the product obtained in step-b) to provide the D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl]phenyl]-,(1S) compound of formula-1.
7. An improved process for the preparation of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1 comprising:
a) Reducing the compound of general formula-2 using suitable reducing agent in
presence of titanium tetrachloride (TiCl4) in a suitable solvent to provide the
compound of general formula-3;

b) reacting the compound of general formula-3 with the compound of formula-4 in presence of organolithium followed by treating with an acid in a suitable solvent to provide the compound of general formula-5;
wherein, R is hydrogen or C1-C5 straight or branched chain alkyl group
c) optionally isolating the product obtained in step-b);
d) reducing the product obtained in step-b) or step-c) with a suitable reducing agent in presence of a suitable solvent to provide the compound of general formula-6;

h) reacting the compound of general formula-8 with the compound of general formula-11 in presence of a suitable base in a suitable solvent to provide the compound of general formula-9;
i) deprotecting the compound of general formula-9 in presence of suitable base in suitable solvent to provide the compound of formula-1.
wherein, X is iodine or bromine, R1 is alkyl group having C1-5 carbon atoms; R is hydrogen or alkyl group having C1-5 carbon atoms; Pg and Z are same as define in claim 1.
8. The process according to claim 7, wherein, in step-a), the suitable reducing agent is selected from trialkylsilyl hydrides, hydrogen gas in presence of Pd, Pt, Raney Ni, Fe; the suitable metal catalyst is TiCl4; the suitable solvent is selected from halohydrocarbon solvents, ether solvents, ester solvents, polar-aprotic solvents or the mixture of solvents thereof;
in step-b), the organolithium base is selected from n-butyl lithium, t-butyl lithium; the suitable acid is selected from mineral acids such as aqueous hydrochloric acid, hydrobromic acid or organic acids such as alkyl sulfonic acids, aryl sulfonic acids, the suitable solvent is selected from water and alcohol solvents having C1-C5 carbon atoms;
in step-d), the suitable reducing agent is selected from trialkyl silylhydride such as trimethylsilyl hydride, triethylsilylhydride, tributylsilylhydride and the like; the suitable solvent is selected from acetonitrile, dimethylformamide, dimethylsulfoxide, dimethylacetamide, dichloromethane, chlorobenzene, chloroform, toluene, xylene, benzene,

ethyl acetate, methyl acetate, propyl acetate, diethylether, tert-butylmethyl ether, tetrahydrofuran or the mixture of solvents thereof;
in step-f), the suitable protecting agent is R2-C(O)-Cl, wherein R2 is alkyl or aryl group; the suitable base is selected from dimethylaminopyridine, triethylamine, diisopropylethylamine, diethylamine, ammonia and the like; the suitable solvent is is selected from acetonitrile, dimethylformamide, dimethylsulfoxide, dimethylacetamide, dichloromethane, chlorobenzene, chloroform, toluene, xylene, benzene, ethyl acetate, methyl acetate, propyl acetate, diethylether, tert-butylmethyl ether, tetrahydrofuran or the mixture of solvents thereof;
in step-g), the suitable thiol reagent is thiol or dithiol alcohol which is selected from decanethiol, dodecane thiol, cyclohexane thiol, cyclopentane thiol, cyclo butane thiol, thiophenol, methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, n-butanethiol, tert-butanthiol, furan-2-ylmethanethiol, ethandithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,3-butanedithiol, 1,4-butanedithiol; suitable Lewis acid is selected from aluminium trihalides such as AlCl3, AlBr3 and the like, boron trihalides such as BF3, BCl3, and the like; TiCl4, FeCl3, ZnCl2 and the like;
in steps-f) and h), the suitable base is selected from inorganic base such as sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium hydride and the like; the suitable solvent is selected from alcohol solvents, chloro solvents, ketone solvents, polar aprotic solvents, nitrile solvents, ester solvents, hydrocarbon solvents, ether solvents and polar solvents like water or mixture thereof;
in step-i), the deprotection is carried out in presence of suitable base or suitable mineral acid. The suitable inorganic base is selected from sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium hydride and the like. The suitable mineral acid is selected from hydrochloric acid, hydrobromic acid, sulfuric acid, acetic acid, nitric acid or their aqueous mixtures. The suitable solvent is selected from alcohol solvents, chloro solvents, ketone solvents, polar aprotic solvents, nitrile solvents, ester solvents, hydrocarbon solvents, ether solvents and polar solvents like water or mixture thereof.

9. An improved process for the preparation of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1 comprising:
a) Reducing the compound of formula-2a with triethylsilylhydride in presence of
titanium tetrachloride (TiCl4) in methylene chloride to provide the compound of
formula-3a;
b) reacting the compound of formula-3a with the compound of formula-4 in presence of w-butyl lithium followed by treating with aqueous HCl and water to provide the compound of formula-5a;
c) reducing the product obtained in step-b) with triethylsilylhydride in presence of BF3.etherate to provide the compound of formula-6a;
d) reacting the product obtained in step-c) with aceticanhydride, dimethylaminopyridine (DMAP) in methylene chloride to provide the compound of formula-7a;

11. The process according to claim 10, wherein, the thiol reagent is selected from decanethiol, dodecane thiol, cyclohexane thiol, cyclopentane thiol, cyclo butane thiol, thiophenol, methanethiol, ethanethiol, 1-propanethiol, 2-propanethiol, n-butanethiol, tert-butanthiol, furan-2-ylmethanethiol, ethandithiol, 1,2-propanedithiol, 1,3-propanedithiol, 1,3-butanedithiol, 1,4-butanedithiol; suitable Lewis acid is selected from aluminium trihalides such as AlCl3, AlBr3 and the like, boron trihalides such as BF3, BCl3, and the like; TiCl4, FeCl3, ZnCl2 and the like.
12. A process for the preparation of compound of formula-8a, comprising: reacting the compound of formula-7a with dodecanethiol / AlCl3 to provide the compound of formula-8a.
13. A process for the preparation of the compound of general formula-8 comprising, treating the compound of general formula 2' with suitable deacylating agent in a suitable organic solvent to produce the compound of general formula-8.
wherein, the acyl group is -(CO)R2 wherein, R2 is C1-C5 straight chain or branched substituted or unsubstituted alkyl groups, phenyl, benzyl and the like.
14. The process according to claim 13, wherein, the suitable deacylating agent is selected from ammonium acetate, sodium sulfite. Preferably ammonium acetate.
15. An improved process for the preparation of the compound of general formula-10, comprising: reacting the compound of general formula-3 with thiol reagent (or) aqueous hydrobromic acid and C1-C3 carboxylic acid

wherein, Z is alkyl group (C1-4 carbon atoms) or aryl group (phenyl or naphthyl) substituted with one or more electron withdrawing groups.
17. The compound according to claim 16, wherein, the electron withdrawing groups is selected from –NO2, -NH3+, -N(R1)3, -CN, -CHO, -COOH, trifluoroalkyl, halogen.. Preferably, (R)-tetrahydrofuran-3-yl 4-nitrobenzenesulfonate, (R)-tetrahydrofuran-3-yl 2-nitrobenzenesulfonate or (R)-tetrahydrofuran-3-yl methane sulfonate.
18. The use of compound of general formula-11
in the synthesis of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S).
19. A process for the preparation of compound of general formula-11, comprising: reacting the (R)-tetrahydrofuran-3-ol with compound of general formula-12 in presence of suitable base and suitable solvent to provide the compound of general formula-11.

wherein, Z is alkyl group (C1-4 carbon atoms) or aryl group (phenyl or naphthyl) substituted with one or more electron withdrawing groups such as –NO2, -NH3+, -N(R1)3, -CN, -CHO, -COOH, trifluoroalkyl, halogen.
20. The process according to claim 19, wherein, the suitable base is organic base or inorganic base which are selected from dimethylaminopyridine (DMAP), triethylamine, trimethylamine, tripropylamine, diisopropylethylamine (DIPEA), pyridine or mixtures thereof; the inorganic base is selected from sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium hydride and the like; the suitable solvent is selected from methylene chloride, methanol, ethanol, isopropanol, n-butanol, isobutanol, ethyl acetate, methyl acetate, propyl acetate, acetonitrile, dimethyl formamide, dimethylacetamide, diethyl ether, methyl tert-butyl ether, tetrahydrofuran and the like.
21. A process for the preparation of (R)-tetrahydrofuran-3-yl 4-nitrobenzenesulfonate of formula-11a, comprising: reacting (R)-tetrahydrofuran-3-ol with 4-nitrobenzene-1-sulfonyl chloride in presence dimethylaminopyridine, triethylamine and methylene chloride.

22. The crystalline form-M of Empagliflozin according to claim 22, further characterized by PXRD additional peaks at 3.6, 4.6, 6.8, 7.5, 16.3, 17.2, 20.5, 21.4, 23.8, 25.0 ± 0.2º of two-theta.
23. The crystalline form-M of Empagliflozin according to claim 22, further characterized by PXRD pattern as shown in figure-1.
24. A process for the preparation of crystalline form-M of Empagliflozin, comprising:

a) suspending Empagliflozin in a suitable solvent,
b) heating the reaction mixture of step-a) to a suitable temperature,
c) adding suitable anti-solvent to the reaction mixture of step-b) at a suitable temperature,
d) stirring the reaction mixture of step-c) at a suitable temperature,
e) isolating the crystalline form-M of Empagliflozin.

26. The process according to claim 25, in step-a), wherein, the suitable solvent is selected from ester solvents, hydrocarbon solvents, polar aprotic solvents, alcohol solvents having C1-C5 carbon atoms, chloro solvents, or mixtures thereof; in step-b), the suitable temperature is ranging from 30°C to 85oC; in step-c), the suitable anti-solvent is selected from hydrocarbons solvents, ether solvents; in step-c) and step-d), the suitable temperature is ranging from -50oC to -40oC; in step-e), the isolation is carried out by distilling obtained reaction mixture from step-d) to afford the crystalline form-M of Empagliflozin.
27. Crystalline Form-I of Empagliflozin-L-proline characterized by PXRD peaks at about 19.9, 31.9 and 33.8 ± 0.2º of two-theta.

28. The crystalline form-I of Empagliflozin L-Proline according to claim 27, further characterized by PXRD additional peaks at about 4.2, 15.6, 18.7, 19.9, 22.3, 31.9, 33.8 ± 0.2º of two-theta.
29. The crystalline form-I of Empagliflozin L-Proline according to claim 27, further characterized by PXRD pattern as shown in figure-4.
30. A process for the preparation of crystalline Form-I of Empagliflozin-L-proline, comprising:

a) suspending Empagliflozin and L-proline in a mixture of isopropanol, dichloromethane, chlorobenzene, tetrahydrofuran or their mixtures
b) heating and stirring the reaction mixture at 60oC to 65oC;
c) cooling and stirring the reaction mixture to 25-30º;
d) isolating crystalline Form-I of Empagliflozin-L-proline.

31. Crystalline Form-II of Empagliflozin-L-proline characterized by PXRD peaks at about 6.9, 9.7, 18.9 and 20.8 ± 0.2º of two-theta.
32. The crystalline form-II of Empagliflozin L-Proline according to claim 31, further characterized by PXRD additional peaks at 4.6, 13.6, 15.9, 16.3, 17.3, 18.6, 19.8, 22.2, 22.6, 23.4, 27.3, 32.0, 33.4 ± 0.2º of two-theta.
33. The crystalline form-II of Empagliflozin L-Proline according to claim 31, further characterized by its PXRD pattern as shown in figure-5.
34. A process for the preparation of crystalline Form-II of Empagliflozin-L-proline,
comprising:
a) Suspending Empagliflozin and L-proline in a mixture of ethanol and toluene;
b) heating the reaction mixture to 60oC to 65oC.;
c) stirring the reaction mixture at 60oC to 65oC;
d) isolating crystalline Form-II of Empagliflozin-L-proline.

35. The crystalline Form-III of Empagliflozin-L-proline characterized by PXRD peaks at about 4.1, 15.5, 19.8 and 31.9 ± 0.2º of two-theta.
36. The crystalline form-III of Empagliflozin L-Proline according to claim 35, further characterized by its PXRD pattern as shown in figure-6.
37. A process for the preparation of crystalline Form-III of Empagliflozin-L-proline, comprising:

a) suspending Empagliflozin and L-proline in a mixture of isopropanol, dichloromethane, chlorobenzene and tetrahydrofuran;
b) heating the reaction mixture to 60oC to 65oC;
c) stirring the reaction mixture at 60oC to 65oC;

d) isolating crystalline Form-III of Empagliflozin-L-proline.
38. The crystalline Form-IV of Empagliflozin-L-proline characterized by PXRD peaks at about 4.2, 12.8, 15.6 and 18.7 ± 0.2º of two-theta.
39. The crystalline form-IV of Empagliflozin L-Proline according to claim 38, further characterized by PXRD additional peaks at about 8.5, 11.6, 14.0, 16.8, 17.1, 18.2, 18.9, 19.9, 21.0, 21.6, 22.2, 23.0, 24.4 ± 0.2º of two-theta.
40. The crystalline form-IV of Empagliflozin L-Proline according to claim 38, further characterized by its PXRD pattern as shown in figure-7.
41. A process for the preparation of crystalline Form-IV of Empagliflozin-L-proline, comprising:

a) Suspending Empagliflozin and L-proline in a suitable solvent;
b) heating to a suitable temperature;
c) stirring for eight hours at suitable temperature;
d) isolating crystalline Form-IV of Empagliflozin-L-proline.
wherein, in step-a), the suitable solvent is selected from ethanol, isopropanol, toluene, dichloromethane, chlorobenzene and tetrahydrofuran or mixtures thereof; in step-b) & step-c), the suitable temperature is about 60oC to 65oC.
42. The Empagliflozin N-methyl-2-pyrrolidone solvate characterized by PXRD pattern having
characteristic peaks at about 4.7, 7.1, 11.1, 23.1, 26.0 ± 0.2º of two-theta.
43. The Empagliflozin N-methyl-2-pyrrolidone solvate according to claim 42, further
characterized by its PXRD pattern as shown in figure-8.
44. Use of Empagliflozin N-methyl-2-pyrrolidone solvate in the preparation of
pharmaceutical compositions of Empagliflozin.
45. Use of Empagliflozin N-methyl-2-pyrrolidone solvate in the preparation of crystalline or
amorphous form of Empagliflozin.

46. Use of crystalline forms I to IV of Empagliflozin L-proline in the preparation of pharmaceutical compositions of Empagliflozin.
47. Use of crystalline forms I to IV of Empagliflozin L-proline in the preparation of crystalline or amorphous form of Empagliflozin.
48. An improved process for the preparation of pure D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-
[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1
comprising:
a) reacting (2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-hydroxybenzyl)phenyl)-6-(hydroxy-
methyl)tetrahydro-2H-pyran-3,4,5-triol formula-13 with compound of general formula Si(R1)(R3)(R4)Cl in presence of suitable base in a suitable solvent;
wherein, R1, R3 & R4 are independently of one another denote C1-4-alkyl, aryl or aryl-C1-3-alkyl, while the alkyl groups may be mono- or polysubstituted by halogen.
49. The process according to claim 48, wherein, the suitable base is selected from N-methyl morpholine, diisopropylethylamine, pyridine, dimethylaminopyridine, sodium hydroxide,

sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium hydride and the like; the suitable solvent is selected from tetrahydrofuran, acetonitrile, ethyl acetate, methyl acetate, methyl tert-butyl ether, C1-5 alcohol solvents.
50. An improved process for the preparation of pure D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1 comprising:
a) reacting (2S,3R,4R,5S,6R)-2-(4-chloro-3-(4-hydroxybenzyl)phenyl)-6-(hydroxy-
methyl)tetrahydro-2H-pyran-3,4,5-triol of formula-13 with trimethylchlorosilane in presence of N-methyl morpholine in tetrahydrofuran to produce (((2S,3S,4R,5R,6R)-2-(4-chloro-3-(4-((trimethylsilyl)oxy)benzyl)phenyl)-6-(((trimethylsilyl)oxy)methyl) tetrahydro-2H-pyran-3,4,5-triyl)tris(oxy))tris(trimethylsilane) of formula-14a;
b) reacting the compound of formula-14a with (R)-tetrahydrofuran-3-yl 4-nitrobenzenesulfonate in presence of K2CO3 in acetonitrile to produce D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl]phenyl]-, (1S) of formula-1

51. The process according to claim 50, the D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-
[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl]phenyl]-, (1S) of formula-1 is having purity
more than 99%, preferably more than 99.39% by HPLC.
52. An improved process for the preparation of pure D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-
[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1
comprising: reacting the compound of general formula-15 with the compound of general
formula-11 in presence of suitable base in a suitable solvent to produce D-glucitol, 1,5-
anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S)
compound of formula-1.
53. The process according to claim 52, wherein, the suitable base is selected from N-methyl morpholine, diisopropylethylamine, pyridine, dimethylaminopyridine, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, sodium hydride and the like; the suitable solvent is selected from tetrahydrofuran, acetonitrile, ethyl acetate, methyl acetate, methyl tert-butyl ether, C1-5 alcohol solvents and the like.
54. An improved process for the preparation of D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl] methyl] phenyl]-, (1S) compound of formula-1 comprising: reacting 4-(2-chloro-5-((2S,3S,4R,5R,6R)-3,4,5-tris((trimethylsilyl)oxy)-6-(((trimethylsilyl)oxy)methyl) tetrahydro-2H-pyran-2-yl)benzyl)phenol of formula-15a with (R)-tetrahydrofuran-3-yl 4-nitrobenzenesulfonate in presence of K2CO3 in acetonitrile to produce D-glucitol, 1,5-anhydro-1-C-[4-chloro-3-[[4-[[(3S)-tetrahydro-3-furanyl]oxy]phenyl]methyl]phenyl]-, (1S) of formula-1.

55. Particle size distribution of amorphous form of Empagliflozin of formula-1 having D(90) less than 300 mm.
56. Particle size distribution of amorphous form of Empagliflozin according to claim 55, is having D(90) less than 200 mm.
57. Particle size distribution of amorphous form of Empagliflozin of formula-1 having D(50) less than 150 mm.
58. Particle size distribution of amorphous form of Empagliflozin according to claim 57, is having D(50) less than 100 mm.