FORM 2
THE PATENT ACT 1970

&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"A NOVEL PROCESS FOR THE PREPARATION OF TENELIGLIPTIN AND ITS PHARMACEUTICALLY ACCEPTABLE SALTS THEREOF"
2. APPLICANT (S)
(a) NAME: Wanbury Ltd.
(b) NATIONALITY: An Indian Company incorporated under the Indian Companies ACT 1956.
(c) ADDRESS:
Wanbury Ltd. , BSEL Tech park, B-wing, 10th floor, sec -30A, opp. Vashi Railway station, Vashi, Navi- Mumbai-400703, India.
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

A NOVEL PROCESS FOR THE PREPARATION OF TENELIGLIPTIN AND ITS PHARMACEUTICALLY ACCEPTABLE SALTS THEREOF.
FIELD OF THE INVENTION:
The present invention relates to a novel process for the preparation of Teneligliptin and its pharmaceutically acceptable salts thereof. The present invention further relates to a novel intermediate compound of structural formula V of Teneligliptin and process for the preparation thereof.
wherein,: R= H or-CHO.
BACKGROUND OF THE INVENTION:
Teneligliptin hydrobromide is chemically known as {(2S,4S-4- [4- (3-methyl-l-phenyl-lH-pyrazole-5-yl) -1-piperazinyl] -2-pyrrolidinyl} (l/3-thiazolidln-3-yl)methahdne, hydrobromide hydrate, known from U.S. Patent No. 7,074,794 and is represented by compound of structural formula I.

U.S. Patent No. 7,074,794 described a process for the preparation of Teneligliptin hydrochloride as shown below in Scheme 1.
The 1-(3-methyl-l-phenyl-lH-pyrazole-5-yl) piperazine compound of structural formula IV is the key intermediate for , the preparation of Teneligliptin.

The preparation of 1-(3-methyl-l-phenyl-lH-pyrazole-5-y1)
piperazine compound of structural formula IV involves
reaction of 1-tertbutoxycarbonylpiperazine compound of
structural formula IX with diketene compound of structural
formula X to produce . 1-acetoacetyl-4-tert-buto piperazine compound of structural formula XI. The obtained l-acetoacetyl-4 -tert-butoxycarbonylpiperazine compound of structural formula XI further reacted with phenylhydrazine in the presence of methane sulfonic acid, followed by addition
of pyridine and cyclizatibn ; using -ipPPClV^; .to v> yield., l-tert-butoxycarbonyl-4-(3-methyl-l-phenyl-5- pyrazole) piperazine compound of structural formula XII which on de-protection yields to 1-(3-methyl-l-phenyl-lH-pyrazole-5-yl) piperazine compound of structural formula IV.
The above process for the preparation : of 1-(3-methyl-l-phenyl-lH-pyrazole-5-yl) piperazine compound of structural formula IV involves, use of diketene compound of structural formula X, which is difficult to handle on commercial scale because of vunstabie: nature -of; di^ketene:.,/: compound of structural formula X causes lower yields; use of expensive compound such as 1-tertbutoxycarbonylpiperazine compound of structural formula IX; use of methane sulfonic

acid which is a potent iai/:precuE:so:r"f 6;^
use of POCI3 as a reagent, which is corrosive, unstable and
difficult to handle on large scale. The above process is not
eco-friendly as it involves use of carcinogenic solvents like
pyridine. All these drawbacks and shortfalls made above
process less economic, :haz#r;. ;;;...'.
Apart from the process for preparation of Teneligliptin hydrobromide, several crystalline polymorphs such as Form A,

Form Band Form. C are .reported"in^U..^
Amorphous form is disclosed in PCT Publication No.
2014/041560.
Overall very few references have been reported for the preparation of: Teneiigiipti^
commercially viable alternative is available to avoid ■: diketene compound of structural formula X. Thus the object of the present invention is to overcome problems associated with the aforementioned processes and to provide a simple, •■••'.eco-friendly.,.''' atomic efficient and commercially^viable. process for the preparation of Teneligliptin and its pharmaceutical^ acceptable salt.
OBJECT OF THE INVENTION:
The object of the present invention ■■■' is. to : provide ;a:; novel -re-process for the preparation of Teneligliptin and its'.'" pharmaceutically acceptable salt thereof, which is simple, eco-friendly, atomic efficient and commercially viable.
Yet another object of the present invention :is-td. prbvide a novel intermediate for the preparation of Teneligliptin and the process for the preparation thereof.
, Yet another object of the present invention is to provide a
i'. ■'• '.. '*''.' ' ■;'.. •. - '.'\ '.■:■• ■.
novel, simple:,. eco-f riertdly and commerciaiily^ viable :p:rdoess.e:
for the preparation for 1-(3-methyl-l-Phenyl-lH-Pyrazole
-5-Y1)piperazine compound of structural formula IV.

SUMMARY OF THE INVENTION:
A first aspect of the present invention is relates to a novel process for the preparation of Teneligliptin and its :■■ ,;. pharmaceutically acceptable salt thereof.
A second aspect of the present invention is relates to a novel process for the preparation of Teneligliptin hydrobromide compound of structural formula I comprising the steps of: a.; reacting compound of structural formula VI with compound
of structural formula VII to obtain compound of; structural ;■ :
formula V
b;V deproteeting compouhdvof structural formula V to obtained compound of structural;formula IV, :
wherein, R = -H or -CHO. c.. reacting compound of structural formula IV with compound ..' of structural formula VIII to; obtained .compound of..-, structural formula III,

.d,.deprotecting . compound of structural ;:formula III with '"suitable acid and further treated ;wifch oxalic^'abid: to" obtained Teneligliptin oxalate compound of structural formula II, and
e.: transforming Teneligiiptin'oxalate compound of structural
formula II in to Teneligliptin hydrobromide compound of > ;. ' v structural formula I.
A third aspect of the present invention is relates to a novel process for the preparation of Teneligliptin hydrobromide compound of structural formula I comprising the steps :,of:...

a. reacting compound of structural formula XIX with compound
;.pf structural formula^XX.t6^Q
formula V .'.'.'',;'^-J:.i-■■■'■■; ■[
wherein, R = -H'or.-CHO. b. deprotecting compound of structural formula V to obtained compound of structural formula IV,
c. reacting compound of structural formula IV with compound of structural formula VIII to obtained compound of structural formula III,
d. deprotecting compound of structural formula III with suitable acid and further treated with oxalic acid to

obtained Teneliglipt'in^bxa'^ formula II, and
e. transforming Teneligliptin oxalate compound of structural formula II in to Teneligliptin hydrobromide compound of
:: structural- formula.-. I :r :■'..:.;.,;.■'; - ^'-.-. -t i-v .' #.r.; -
A fourth aspect of the present invention is relates to a novel
intermediate compound of structural formula V and process for
the preparation thereof:.. >^ ■■'^■}: ,'■ -':;:;■
wherein, R= -H or -CHO.
A fifth aspect of the present invention is relates to a process
.'.'.../'---V:-'■' for the preparation of novel intermediate compound of

structural formula V comprises reacting compound of structural formula VI with compound of structural formula VII to obtain compound of structural formula V.
Asixth aspect of the present invention is relates to a process for the preparation of novel intermediate compound of structural formula V comprises reacting compound of ■ Structural formula'-XIX with compourid. of structural, formula .. XX to obtain compound of structural formula V.
A;seventh aspect of the present invention is relates to a novel, simple, eco-friendly and commercially viable process for: the preparation for 1-(3-methyl-l-Phenyl-lH-Pyrazole-5-Yl) : piperazine compound of structural formula IV comprising the steps of: a. reacting compound of structural formula VI with compound
of structural formula VII to- obtain compound of; structural:j
formula V, and

b. deprotecting compound of structural formula V to obtained compound of structural formula IV. :
A eighth aspect of the present invention is relates to a novel, simple, eco-friendly and commercially viable process for the preparation : for ; 1-(3-methyl-l-Phenyl-lH-Pyrazole-5-Yl) piperazine compound of structural formula IV cdmprisiiig the steps of:
a. reacting compound of structural formula XIX with compound of structural formula XX to obtain compound of structural :: formula V, and
b. deprotecting compound of structural formula V to obtained compound of structural formula IV.

wherein, R = -H or -CHO.
DETAIL DESCRIPTION OF THE INVENTION:
In one embodiment, the present invention provides a novel process for the preparation of Teneligliptin and its pharmaceutically acceptable salt thereof.
In another embodiment, the present invention provides a novel process for the preparation of Teneligliptin hydrobromide compound of structural formula I wherein:
The react ion'-;' of compound, .of; structural; ./formula; V/I.. with compound of structural formula VII may be carried out in presence of suitable base and suitable solvent at a temperature in the range of 140°C to 150°C to obtained compound ;■.'..:•..■ of structural formula V.
The example of base may include but not limited to alkali metal carbonate such as potassium carbonate, sodium carbonate etc.
...The examples of suitable solvent may include but not limited topolar aprot.ic soivehts-such as>-acetone, dimethyl formamide, dimethyl sulphoxide, dichloromethane and the like.;

The .compound of ^structursl^^
quenching the reaction mixture with water at a temperature in the range of 10°C t 15°C, followed by treating it with hydrochloric acid up to pH 6 and extracting it with ■dichloromethane. The resultingdichloromethane layer was washed with 10% brine sdititi6h:;:^
dichloromethane layer then concentrated under reduced pressure and precipitated with diisopropyl ether to obtained solid. The resulting solid was filtered to obtained compound of structural formula V..
The deprotection of compound of structural formula V may be carried out in presence of suitable acid in suitable solvent at a temperature in the range of 70° to 120°C.
The examples of suitable acid may include but not limited to •;.:'/ inorganic acid or organic acid. Preferably inorganic acid like hydrochloric acid.
; The examples of suitable solvent may include but not limited to polar protic solvents such as : ethanol^ methanolv isopropanol, n-butanol and the like. Preferably n-butanol.
The compound of structural formula IV may be isolated as per methods known in the art or directly used in the next step of the reaction. •'";;
The reaction of compound of structural formula IV with compound of structural formula VIII may be carried out in presence of metal hydrogen complex, optionally in presence

of acid catalyst to obtained compound of structural formula III.
The examples :of metal .hydrpge^ but not
limited to sodium borohydride, sodium cyanobbrohydtide.,^nd:::■:■ sodium triacetoxyborohydride. Preferably sodium triacetoxyborohydride.
The examples of acid.catalyst, may include but not limited to acetic acid, p-toluenesulfonic acid and boron trif luoride.,
The compound of structural formula VIII used herein may be
prepared by the processes disclosed in U.S. Patent Nos.
•■'■. 7,:;074,794 and 8,003,790/ which are-incorporated herein as
reference only. ■'■■■.-:'■■'[■.}:'.■ ■,.
The deprotection of compound of structural formula III may be carried out in presence of suitable acid such as hydrochloric acid,... trifiluoroacetic: acid; and ,the like in suitable solvent such as methanol, ethanol, isopropanol/;.: ethyl acetate, dichloromethane, chloroform, tetrahydrofuran, 1, 4-dioxane and the like at a temperature in the range of 20°C to 75°C.
After completion of reaction resulting ;reactiori mixture may--; be treated with oxalic acid solution in alcohol solvent such as methanol, ethanol, isopropanol and the like at a temperature in the range of 20-30°C to obtained Teneligliptin oxalate compound of structural formula- II,.,■■■

The transformation of Teneligliptin oxalate compound of structural formula II in to Teneligliptin hydrobromide compound of structural fd:rm>la;:I.;may;b^^car;rie.dvout:-bY,treatinij . Teneligliptin oxalate compound of structural formula II with base in suitable solvent and then treating resulting reaction mixture with aqueous solution of hydrobromic acid at 50-60°C fpr 30 minutes to 4 hours to obtained Teneligliptin hydrobromide compound of.structuralformula Iy,
The examples of base may include but not limited to sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate and the lake.;:- fe;
Examples of suitable solvent may include but not limited to ethanol, methanol isopropanol, dichloromethane, ethyl acetate, water or mixture(s) thereof.
Teneligliptin hydrobromide compound of structural formula I may be isolated as per methods known in the art.
The. reaction of compound of structural formula XIX with compound of structural formula XX''may be ;carried-:out in presence of suitable base and suitable solvent at a temperature in the range of 5°C to 40°C to obtained compound of structural formula V.
The example of base may include but ndt limited tdalkaii metal carbonate such as potassium carbonate, sodium carbonate etc.

.The examples of suitable-solvent may include but not limited to polar aprotic solvents"such:'Sis,r adetonev :;%etrahydrd;furany;. ; , dimethyl formamide, dimethyl sulphoxide, dichloromethane and the like.
The compound ,of structural .formula .;VI(b): (Wherein R= -CHO) may be prepared by reacting compound/'d-f'strudturUi:sform^la ;v: VI (a) (wherein, R=-H) with P0C13 and DMF or formylating agents such as formic acid, ammonium formate, N-methyl formanilide in polar aprotic solvents such as, acetone, dimethyl formamide, dimethyl sulphoxide, dichloromethane and the like at a temperature in the range'of 50°C to 110°C.
In another embodiment, the present invention provides a novel intermediate compound of structural formula V and process for the preparation thereof.
In the preparation of novel intermediate compound of structural formula V, wherein R = -CHO prevents side reaction and increase rate of reaction between compound of structural

formula VI and compound '".of structural- formula. ;;VII.' Also. i;n vthe preparation of novel intermediate compound of structural
formula V involves use of compound of formula VII, wherein
-CHO group used as protecting group which inhibit dimer
.formation, easily deprotect.edand increase.atomic efficiency
'of the reaction.' ■ :';'''v\; ?'". ";^
In another embodiment, the present invention provides a novel, simple, eco-friendly and commercially viable process for the preparation for 1-(3-methyl-l-Phenyl-lH-Pyrazole-5-Yl) piperazine compound of structural-formula IV ::
EXAMPLES:
The present invention is described with reference of the following examples. However these examples are for '..''illustrative"1.-purpose-' only and not to be construed as limitations on the scope of the invention.
Example 1: Process for preparation of 5-chloro-3-methyl-l-phenyl-lH -pyrazole-4-carbaldehyde compound of structural formula VI (fc). ;
To a dimethyl formamide (80 ml) was slowly added phosphorous oxychloride (160 gm) at temperature 5-10°C, followed by 5-chloro-3-methyl-lphenyl-lH-pyrazole compound of structural formula VI(a) (lOOg) was added to it and temperature raised :to l05-1100Gi and: stirred fpr;30. hours. The.

reaction mixture was maintained till completion of reaction,
then cooled to 40-45°C and quenched in another flask containing
DM water (2500 ml) at 15-20°C. Reaction mass was stirred for
10 hours at 25-30°C and 'filter^ .'.
structural formula VI(b) which was : further purified- by... .. recrystallization in isopropanol to obtain pure compound of structural formula VI(b). Yield: 79% \. -Purity:v99.5r. .; ■:;. ' .-t- . ^
Example 2: Process for preparation of 5-(4-formyl -piperazine-1-yl)-3-methyl-l-phenyl-lH-pyrazole-4-carbald ehyde compound of structural formula V (Wherein, R = -CHO).
Piprazine aldehyde^, (2. 58 . gm)v and ^compound of structural formula VI (b) (10 gm) was added to the solution of dimethyl, --■■■ formamide (60 ml) and potassium carbonate (12.5 gm) and heated to 145-150°C for 10 hours. The resulting reaction mixture was filtered at ambient temperature to remove inorganic salt. The filtrate was quenched into DM water .(250. 0 ml) at 10-15°C and pH of filtrate was adjusted to 6 using diluted.Hydrochloric acid (5N) . The resulting reaction mixture was extracted with dichloromethane (150.0ml) and washed with 10% solution of brine (50.0ml) and water (50.0ml) subsequently. The resulting organic layer was concentrated under reduced pressure, and solid was precipitated with diisopropyl ether (50.0 ml) . The resulting solid was filtered to obtain the compound of structural formula V. Yield: 75% - . Purity: 99.5% ' . .'■" $■■'■'. :;.V:-' b;:

Example 3: Process for preparation of 3-{(2S,4S)-l-tert-butoxycarbonyl-4-[4-(3-methyl-l-phenyl-5-pyrazolyl)-1 -piperazinyl] -2^pyrrolidinyl^arbonyl}:wl,3^th;iazolidine compound of structural formula III.
Compound of structural formula V (10.0 gm) was added to the mixture of n-butanol (60.0 ml) and concentrated hydrochloric acid (40.0 ml) . The resulting reaction mixture was heated to 115-120°C for ;the period'pf 5 hours.. ■After- the: completion- of/ . ' ■ reaction solvents were evaporated under reduced pressure at 50-60°C completely. The reaction mixture was taken in to the water (100.0 ml) and washed with ethyl acetate (2 x 50.0 ml) and toluene (50 ml) . The pH of the aqueous layer was adjusted to 10 using 6N caustic solution. The product •£;e.//Compound.. of structural formula IV was extracted in dichloromethane(2 x 50. 0 ml) which was further washed with 10% solution of brine (50.0 ml) and water (50.0 ml) subsequently. The organic layer was dried over sodium sulfate and compound of structural formula VIII (10.06 gm) --with /acetic acidf3.78 -ml) .was '■•a'dded..'■■':■ to it followed by sodium triacetoxyborohydride (13.5 gm) was added lot wise (4 x 3.375 gm) and stirred at 25-30°C for 8 hours. The reaction mixture was quenched with water (100.0 ml)and then organic layer was separated and further washed with saturated solution; of -sodium bicarbonate (100.0 ml) followed by 10% solution of brine (50.0 ml) and water (50.0'" ml) subsequently. The resulting organic layer was dried and distilled to dryness under reduced pressure to obtained foamy mass which was isolated as solid using n-hexane (100. 0ml) to obtained compound of ^structural;-:fbrmuia ITi> ■ ; Yield: 90% Purity: 94.5%

Example 4: Process for preparationof' ~3^{(2S,4S) -4-[4-(3-methyl-l-phenyl-5-pyrazolyl)-l-piperazinyl}-2-py rrolidinylcarbonyl}-1,3-thiazolidine oxalate compound of structural formula II.
The, compound; of structural;,formula III (10.;0 gm) was added to the mixture of isopropanol (30.0 ml) and isbpropanolic: hydrochloric acid (30.0 ml) . The resulting reaction mixture was heated to 65-70°C for 5 hours. After completion of reaction the reaction mass was concentrated under reduced pressure and "'■..";'■;■■ water (100.0 ml) was added to.the reaction mass followed by
dichloromethane (50.0 ml) was added to the reaction, mass and '■"■■' pH of the reaction mass was adjusted to 8 using saturated solution of sodium bicarbonate. The organic layer was separated and washed with water (50.0 ml) and dried over sodium \ sulfate. The resulting organic layer was added; solution of oxalic acid (2.73 gm of oxalic acid dissolved in 10.0 ml of isopropanol) and stirred for 1 hour at 25-30°C. The resulting reaction mass was concentrated under reduced pressure and solid product was isolated using methyl-tert-butyl ether(100.0 ml) under nitrogen atmosphere to obtain compound structural formula II. Yield: 88% Purity: 96.5%
Example 5: Process for preparation of Teneligliptin hydrobromide compound of structural formula I.
The 3-{(2S,4S)-4-[4-(3-methyl-l-phenyl-5-pyrazolyl) -1-piperazinyl}-2-pyrrolidinylcarbonyl}-1,3-thiazolidine oxalate compound of structural formula II (10.0 gm) was added

to the mixture of water (50. 0 ml) and dichloromethane :(50,0:. : . ml) and pH of the solution was adjusted to 8 by using 10% solution of sodium bicarbonate (30 ml) . Then organic layer was separated, washed with water (50.0 ml), 10% solution of brine (50.0 ml) .and dried; :^
resulting organic layer was co distilled with isopropanol.
The resulting isopropanol layer was treated with charcoal at
50-55 °C and filtered through micron filter to obtain filtrate.
The resulting filtrate was added aqueous solution of
hydrobromic acid (4:;8%.,, 5T5 ml )'■•■'at. 5.5.-60?C-and maintained for.
60 minutes. The resulting reaction mixture was cooled' to ;
ambient temperature to obtain solid. The resulting solid was
filtered to obtain Teneligliptin hydrobromide compound of
structural formula I.
. Yield: 95% . '-;■ .::■:'%■■'.■■[. .-,/..-,'■■
Purity: >99%
Example 6: Process for preparation of 5-(4-formyl -piperazine-1-yl)-3-methyl-l-phenyl-lH-pyrazole compound of structural formula V (Wherein, k = -H)
The compound of structural formula XIX '(wherein, R = -H) was added to a suspension of sodium hydride (5.0 gm) in tetrahydrofuran (100 ml) under inert atmosphere at 10-15°C stirred for 30-60 minutes. The resulting reaction mixture was added, a .solution of compound of struc.tura;l formula :,XX-;'(;9, 82 gm, dissolved in 50 ml of tetrahydrofuran) over period of 60 minutes at 10-15°C and then reaction mixture was stirred for 3 hours at 20-25°C. The resulting reaction mixture was /quenched with saturated solution of ammonium chloride (100
ml) at 5-10°C and extracted with dictiloromethane:i. (.3 x 50 ml) . \.

The all organic layers were combined, concentrated under reduced pressure and solid product was isolated using methyl-tert-butyl ether(50.0 ml) under nitrogen atmosphere .to obtain compound, st:ru©tiifa;lV-fd:r^ Yield: 57% Purity: 99.4%
Example 7: Process for preparation of 5-(4-formyl -piperazine-1-yl) -3-methyl-l-phenyl-lH-pyrazoJ.e--4-carbald ehyde compound of structural formula V (Wherein, R = —CHO)
The compound of structural formula XIX (wherein, R = -CHO) was added to a suspension of sodium hydride (4.2.0 gm) in tetrahydrofuran (100 ml) under inert atmosphere at 10-15°C and stirred for 30-60 minutes. The resulting reaction mixture was added a solution of compound of structural formula XX (8 .45 gm, dissolved in 50 ml of tetrahydrofuran) over period of 60 minutes at 10-15°C and then reaction mixture was stirred for 3 hours at 20-25°C. The resulting reaction mixture was :quenched with saturated"solution of; ammonium chloride (100 ml) at 5-10°C and extracted with dichloromethane (3 x 50 ml) . ' The all organic layers were combined, concentrated under reduced pressure and solid product was isolated using methyl-tert-butyl ether(50.0 ml) under nitrogen atmosphere to obtain compound ^structural- formula :V.;:;-Yield: 55% Purity: 99.3%

WE CLAIM:
1. .A novel process for ;ithey ■preparation^ of ; Teneligliptin hydrobromide compound-of: structural fdrm^ the steps of: a. reacting compound of structural formula VI with
compound of structural formula VII to obtain compound
of structural formula V.,
wherein, R = -H or -CHO.
b. deprotecting compound of structural formula V to obtained compound of structural formula IV,
wherein, R = -H or -CHO. ■c. reacting compound" bf 'structural ^formula,.';. IV; with;;
compound of structural formula VIII to obtained
compound of structural formula III,

d. deprotacting compound,of structural.formula III with suitable acid and further t'f^eatea"Vi|::n-'bx.ail.c-'"'adi;^,--.t.o'. obtained Teneligliptin oxalate compound of structural formula II, and
' e. transforming Teneligliptin :._ oxalate compound of structural formula II in to Teneligliptin hydrobromide compound of structural formula I.
2. The process according to claim 1, wherein the reaction of compound of structural 'formula; VI -with compound of structural formula VIII is carried out in presence of suitable base such as alkali metal carbonate selected from the group consisting of potassium carbonate, sodium carbonate and the like, and suitable solvent such as polar ,.aprotic: solvents^ such;selected from the group consisting, of acetone, dimethyl formamide, dimethyl sulphoxide,. dichloromethane and the like at a temperature in the range of 140°C to 150°C.

3. The process according to claim 1, wherein the depfotection
of compound of structural formula V is carried out in
presence of suitable acid selected from the group
: ■ consisting of inorganic acid or organic acid; Preferably ^: inorganic ac^
selected from the group consisting of polar protic solvents : ;* such as ethanol, methanol, isopropanol, n-butanol and the like; Preferably n-butanol; at a temperature in the range of 70° to 120°C.
4. The process according to claim 1, wherein the reaction of
compound of structural formula IV with compound of
structural formula VIII is carried out in presence of metal
.hydrogen complex selected from the group consisting of sodium borohydride, sodium/; cyanqboroftydride and sodium triacetoxyborohydride; Preferably sodium triacetoxyborohydride; optionally in presence of acid catalyst selected from the group consisting of acetic acid, '■•: p-toluenesulfonic acid and boron trifluoride.
5. The process according to claim 1, wherein the deprotection
of compound of structural formula III is carried out in
presence of suitable acid such as hydrochloric acid,
; -tri'f luoroacetic acid and the like; in suitable solvent such ■■/■■■'as; methanol, : ethanol,■ isopropanol// ethyl . acetate, dichloromethane, chloroform, tetrahydrofurari, 1,4-dioxane and the like; at a temperature in the range of 20°C to 75°C, followed by reaction mixture is treated with oxalic acid solution in alcohol solvent such as

methanol, ethanol, isopropanol and the like at a temperature in the range of 20-30°C.
'6. The -process :,;,;accord^hg^..^ ..:■ the.
transformation of Teneligliptin oxalate compound of ■: structural formula II in to Teneligliptin hydrobromide compound of structural formula I is carried out by -, treating Teneligliptin oxalate compound of structural ■formula II with base ■seleciied from the: group consisting of sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate and the like; in suitable solvent selected fromthe. group consisting of -ethanol; methanol isppropanol, ?-dichioromethane^-. ethyl . acetate, water or mixture(s) thereof and then treating resulting reaction mixture with aqueous solution of hydrobromic acid at 50-60°C for 30 minutes to 4 hours.
. 7 . A novel intermediate compound ^of-structuxal formula V and. : process for the preparation thereof.
wherein, R= -H or -CHO.
■ 8.; A process, for :the preparation .. of; novel intermediate compound of structural formula V: comprises reacting compound of structural formula XIX with compound of

structural formula XX to obtain compound of structural formula V.
9. The process according to claim 8, wherein the reaction of
compound of structural formula XIX with compound of
structural formula XX is: carried out in presence of
suitable base and suitable solvent at a'temperature, in. the:
range of 5°C to 40°C.
10. The process according to claim 9, wherein the suitable
; base is selected from the group consisting of alkali metal
carbonate such as potassium carbonate> sodium carbonate
etc., Suitable solvent is selected from the group
consisting of polar aprotic solvents such as acetone,
tetrahydrofuran, dimethyl formamide, dimethyl sulphoxide,
dichloromethane-. and the like. .