DESC:FIELD OF THE INVENTION
Present invention provides novel process for the preparation of Netarsudil or pharmaceutically acceptable salts thereof involving a compound of Formula II or pharmaceutically acceptable salts thereof,

Formula II.
Present invention further provides a process for the preparation of novel compounds of Formula II or pharmaceutically acceptable salts thereof.

BACKGROUND OF THE INVENTION
Netarsudil is a Rho kinase inhibitor used for treatment of elevated intraocular pressure (IOP) in patients with open-angle glaucoma or ocular hypertension. Marketed in united states by the brand name “Rhopressa” having Netarsudil in the form of Dimesylate salt.

Netarsudil is chemically known as (S)-4-(3-amino-1-(isoquinolin-6-yl-amino)-1-oxopropan-2-yl) benzyl 2,4-dimethylbenzoate and is represented by compound of Formula I.

Formula I

Prior art processes suffer from drawback of large number of reaction steps, use of column and use of costly reagent like tetrabutylammonium fluoride which makes the process lengthy and costly and also not feasible for industrial scale of synthesis because of increase in number of steps which further causes increase in impurity and decreased in overall yield.

In view of the above, there is a need to develop a novel process for the preparation of Netarsudil and its pharmaceutically acceptable salts, that requires minimal steps and provides highly pure Netarsudil and its salts. Hence, present invention is focussed toward the development of the process for the preparation of Netarsudil by using novel intermediates and which not only involves lesser step but is reproducible and easy to handle during large scale production.

OBJECTIVE OF THE INVENTION
Main object of the present invention is to provide a process for the preparation Netarsudil of Formula I and/or its pharmaceutically acceptable salts by using compound of Formula II or pharmaceutically acceptable salts thereof, by involving commercially viable process which results in improved yield and purity.

Another object of the present invention is to provide novel compounds of Formula II or pharmaceutically acceptable salts thereof, use for the preparation of Netarsudil or pharmaceutically acceptable salts thereof.

Another object of the present invention is to provide a process for the preparation of compounds of Formula II or pharmaceutically acceptable salts thereof, and purification thereof.

SUMMARY OF THE INVENTION
Accordingly, the main aspect of the present invention provides process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, by using novel intermediates of Formula II or pharmaceutically acceptable salts thereof.

Another aspect of the present invention provides a compound of Formula II or pharmaceutically acceptable salts thereof,


Formula II,
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, benzyloxycarbonyl (Cbz), p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, Fluorenylmethoxycarbonyl (Fmoc), 2,7-di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group;
R3 is independently selected from hydrogen, suitable oxygen protecting group, or
,
wherein waved line shows point of attachment.

Another aspect of the present invention is to provide compound of Formula VI,

Formula VI,
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, benzyloxycarbonyl (Cbz), p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2,7-di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl(Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group;
R3 is as defined as above and R4 is selected from hydrogen or lower alkyl group.

Another aspect of the present invention is to provide process of preparing Netarsudil or its pharmaceutically acceptable salt by using compound of Formula VI.

Another aspect of the present invention provides process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, comprising the steps of:
a) condensing compound of Formula VI with 6-aminoisoquinoline or its N-oxide in presence of suitable activating agent to give compound of Formula II,

Formula VI Formula II,
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, p-toluene sulfonyl, benzyloxycarbonyl (Cbz), 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2,7-di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group,
R3 is independently selected from hydrogen, suitable oxygen protecting group, or
,
wherein waved line shows point of attachment, and
b) converting compound of Formula II to Netarsudil of Formula I or its pharmaceutically acceptable salts thereof.

Another aspect of the present invention provides a process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, comprising the steps of:
a) condensing compound of Formula VI with 6-aminoisoquinoline or its N-oxide in presence of suitable activating agent to give compound of Formula II or pharmaceutically acceptable salt thereof,

Formula VI Formula II,
b) reacting compound of Formula II or its pharmaceutically acceptable salt with compound of Formula A in presence of suitable activating agent to give compound of Formula VIII,
, and
Formula II Formula A Formula VIII
wherein R1, and R2 are as defined above, R3 is selected from hydrogen or oxygen protecting group and A is hydroxyl or halogen, and
c) deprotecting compound of Formula VIII to Netarsudil of Formula I or pharmaceutically acceptable salt thereof.

Another aspect of the present invention provides process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, by using compound of Formula VIII or pharmaceutically acceptable salt thereof, wherein said compound of Formula VIII is represented by Formula IV or pharmaceutically acceptable salt thereof, comprising the steps of:
a) de-protecting compound of Formula IV to give Netarsudil of Formula I,
, and
b) optionally converting compound of Formula I to its pharmaceutically acceptable salts.

Another aspect of the present invention provides compound of Formula VII, wherein said compound is represented as compounds of Formulae VIIa and VIIb,
,
wherein R3 is as defined above.

Another aspect of the present invention is to provide 6-Aminoisoqunoline-N-oxide compound of Formula IX,
.
Formula IX

Another aspect of the present invention provides compound of Formula II, wherein said compound is isolated as crystalline solid.

Another aspect of the present invention provides compound of Formula II, wherein said compound is isolated as amorphous solid.
DETAILED DESCRIPTION OF THE INVENTION
There are few processes known for the preparation of Netarsudil, however known processes suffer from drawbacks such as use of large number of reaction steps and its application on commercial stage. Present invention has dealt with aforesaid drawbacks by developing a novel process for the preparation of Netarsudil or pharmaceutically acceptable salt by using novel intermediates of Formula II or pharmaceutically acceptable salt thereof,

Accordingly, main embodiment of the present invention provides a compound of Formula II or pharmaceutically acceptable salts thereof,

Formula II
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, benzyloxycarbonyl (Cbz), p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2,7-di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group,
R3 is independently selected from hydrogen, suitable oxygen protecting group, or
,
wherein waved line shows point of attachment.

Another embodiment of the present invention provides process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, by using novel intermediates of Formula II or pharmaceutically acceptable salts thereof.

Another embodiment of the present invention provides novel compound of Formula II, or pharmaceutically acceptable salts thereof, wherein said compound is represented by formulae:
.

Another embodiment of the present invention is to provide compound of Formula VI,

Formula VI
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2,7-Di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group,
R3 is as defined above and R4 is selected from hydrogen or lower alkyl group.

Another embodiment of the present invention is to provide process of preparing Netarsudil or its pharmaceutically acceptable salt by using compound of Formula VI.

Another embodiment of the present invention provides a process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, comprising the steps of:
a) condensing compound of Formula VI with 6-Aminoisoquinoline in presence of carboxyl activating agent to give compound of Formula II,

Formula VI Formula II,
wherein,
R1 and R2 are independently or together selected from hydrogen, amine protecting group such as Boc, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, benzyloxycarbonyl (Cbz), p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2,7-di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, 9-(4-bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-nitrobenzyl, or any other suitable amine protecting group,
R3 is independently selected from hydrogen, suitable oxygen protecting group,
,
wherein waved line shows point of attachment, and
b) converting compound of Formula II to Netarsudil of Formula I or its pharmaceutically acceptable salts thereof.

Another embodiment of the present invention provides a process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, comprising the steps of:
a) condensing compound of Formula VI with 6-Aminoisoquinoline or its N-oxide in presence of suitable activating agent to give compound of Formula II or its pharmaceutically acceptable salt,

Formula VI Formula II
b) reacting compound of Formula II or its pharmaceutically acceptable salt with compound of Formula A in presence of suitable activating agent to give compound of Formula VIII,
; and
Formula II Formula A Formula VIII
c) deprotecting compound of Formula VIII to Netarsudil of Formula I or pharmaceutically acceptable salt;
wherein, R1, R2 and R4 are as defined above; R3 is selected from hydrogen, oxygen protecting group and A is hydroxyl or halogen.

In another embodiment, the suitable activating agent used for condensation at step a) or step b) is selected from, but not limited to, benzotriazole-1-yl-oxy-tris (dimethylamino)phosphoniumhexafluoro-phosphate (BOP), N,N'-dicyclohexylcarbodiimide (DCC), 1-hydroxibenzotriazol anhydrous(HOBt), N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide (EDC), 1-[bis(dimethylamino) methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxidhexafluorophosphate (HATU), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafhexafluoro phosphate (HBTU) and the like.

In another embodiment, said oxygen protection group may be selected from, but not limited to, triisopropylsilane (TIPS); methoxymethyl ether, tetrahydropyranyl ether, t-butyl ether, allyl ether, benzyl ether, t-butyldimethylsilyl ether, t-butyldiphenylsilyl ether, acetic acid ester, pivalic acid ester, benzoic acid ester and the like.

In another embodiment, condensation at step a), or reaction at step b) may be carried out in presence of a suitable solvent. The suitable solvent includes but is not limited to, alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, pentanol, octanol and the like; esters such as methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate and the like; ketones such as acetone, ethyl methyl ketone, methyl isobutyl ketone and the like; ethers such as dimethyl ether, diethyl ether, diisopropyl ether, tert-butyl methyl ether, dimethoxyethane, tetrahydrofuran, dioxane and the like; hydrocarbons such as toluene, xylene, chlorobenzene, heptane, hexane and the like; acetonitrile; dimethylformamide; dimethyl sulfoxide; water or mixtures thereof.
In another embodiment, condensation at step a), or reaction at step b) may be carried out in presence of inorganic base such as potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate; or organic base such as triethylamine, diisopropylethylamine, pyridine, dimethyl amino pyridine (DMAP); or mixture thereof.

In another embodiment, compound of Formula II wherein R3 is oxygen protection group may be subjected to deprotection using TBAF in ether solvents such as THF.
In another embodiment, deprotection of the amino group of the compound of Formula VIII is carried out in presence of a suitable deprotecting agent and a suitable solvent. The suitable solvent includes, but is not limited to, alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, pentanol and the like; esters such as methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate and the like; ketones such as acetone, ethyl methyl ketone, methyl isobutyl ketone and the like; ethers such as dimethyl ether, diethyl ether, diisopropyl ether, tertbutyl methyl ether, dimethoxyethane, tetrahydrofuran, dioxane and the like; hydrocarbons such as toluene, xylene, chlorobenzene, heptane, hexane and the like; halogenated solvents such as methylene dichloride, ethylene dichloride and the like; acetonitrile; dimethylformamide; dimethyl sulfoxide; water; or mixture thereof.

The deprotecting agent used at step c) may be selected from the group consisting of acid such as hydrochloric acid, sulfuric acid, hydrobromic acid, formic acid, acetic acid, trifluoroacetic acid and the like.

In another embodiment, when the compound of Formula VIII is N-oxide (n = 1), said compound is deprotected at step c) above, by using titanium tetrachloride, tin (II) chloride or mixture thereof.

Another embodiment of the present invention provides a process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, wherein said compound of Formula VIII is represented by Formula IV or pharmaceutically acceptable salt thereof, comprising the steps of:
a) de-protecting compound of Formula IV to give Netarsudil of Formula I,
, and
b) optionally converting compound of Formula I to its pharmaceutically acceptable salts.

In another embodiment, the present invention provides a process for the preparation of Netarsudil Dimesylate salt by reaction of Netarsudil with methanesulphonic acid in presence of suitable solvent to give Netarsudil Dimesylate salt.

In another embodiment, the suitable solvent used for the synthesis of Netarsudil dimesylate salt includes, but is not limited to, alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, pentanol, octanol and the like; esters such as methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate and the like; ketones such as acetone, ethyl methyl ketone, methyl isobutyl ketone and the like; ethers such as dimethyl ether, diethyl ether, diisopropyl ether, tertbutyl methyl ether, dimethoxyethane, tetrahydrofuran, dioxane and the like; hydrocarbons such as toluene, xylene, chlorobenzene, heptane, hexane and the like; halogenated solvents such as methylene dichloride, ethylene dichloride and the like; acetonitrile; dimethylformamide; dimethyl sulfoxide; water; or mixtures thereof.

Another embodiment of the present invention provides compounds of Formulae VII, wherein said compound is represented as compounds of Formulae VIIa and VIIb,
,
wherein R3 is as defined above.

Another aspect of the present invention is to provide 6-Aminoisoquinoline N-oxide compound of Formula IX,
.
Formula IX

Another embodiment of the present invention is to provide process of preparing Isoquinoline-N-oxide compound of Formula IX, wherein said process comprising the steps of:
a) reacting 6-bromo isoquinoline with hydrogen peroxide in presence of acid to give 6-bromo isoquinoline N-oxide (Formula B),
,
Formula B
b) reacting 6-bromo isoquinoline N-oxide (Formula B) with phthalimide in presence of base to give compound of Formula X,
, and
Formula B Formula X
c) deprotecting compound of Formula X to give compound of Formula IX,

Formula X Formula IX .

Another embodiment of the present invention provides compound of Formula II, or Formula VII, wherein said compounds are isolated as solid.

Another embodiment of the present invention provides compound of Formula II, or Formula VII, wherein said compounds are isolated solid such as crystalline or amorphous form.

In another embodiment, the process of preparing Netarsudil or its pharmaceutically acceptable salt is carried out at temperature ranging from 0oC to reflux temperature of the solvent.

In another embodiment, the present invention also relates to novel crystalline form of Netarsudil Dimesylate salt. In a further embodiment, crystalline form as prepared by the present invention is stable at 30ºC and above and all humidity conditions. In a further embodiment, stable polymorph obtained as per present invention does not convert to any other polymorph at 30ºC and above and all humidity conditions. In a further embodiment, crystalline form as prepared by present invention is chemically stable.

In another embodiment, the process of preparing Netarsudil or its pharmaceutically acceptable salt may involve isolation and/or purification of intermediate, or may be carried out in one pot without isolation of intermediates.

In another embodiment, Netarsudil or its pharmaceutically acceptable salt as prepared by the process of the present invention is characterized by particle size distribution wherein, d90 is 0.1µm to 500µm.

In further embodiment, the present invention provides Netarsudil or its pharmaceutically acceptable salt having purity 99.5% and above, and preferably 99.9% and above.

In further embodiment, the present invention further provides a composition comprising Netarsudil or its pharmaceutically acceptable salt obtained by the process of the present invention along with at least one pharmaceutically acceptable excipients thereof.

In another embodiment, the compound of Formula I or its pharmaceutically acceptable salt thereof is prepared as per the Scheme 1 mentioned below:
Scheme 1: -

R is a protecting group selected from boc anhydride, pthalimide, acetyl, benzylideneamine, benzyl ester.

EXAMPLES
Example-1: Preparation of (4-iodobenzyloxy) triisopropylsilane
Charged dichloromethane (500mL) [or acetonitrile or tetrahydrofuran or toluene or dimethylformamide], 4-Iodo benzyl alcohol (100g), Imidazole (64.0g) [or dimethylaminopyridine or diisopropylethylamine] at 20-25ºC into round bottom flask. Stirred the mass at 20-25 ºC for 15-20 min, charged tri-isopropyl chlorosilane (82.38 g) to it at 20-25°C, continued stirring the mass at 20-25ºC overnight and monitored the reaction by TLC. After completion of the reaction, charged DM water (500mL) into the reaction mass at 20-25 ºC and stirred. Allowed to settle the mass and separated the layers at 20-25ºC. Charged organic layer, added saturated brine (500mL) at 20-25ºC to round bottom flask and stirred. Allowed to settle the mass and separated the layers at 20-25ºC. Distilled out organic layers (dichloromethane) at 40-45ºC to recover dichloromethane till solvent ceases to come. Degassed the mass completely under vacuum at 40-45ºC to give title compound. yield 150g.

Example 2: Preparation of Ethyl 2-cyano-2-(4-((triisopropylsilyloxy)methyl) phenyl)acetate
Charged dimethylsulfoxide (200 mL) [dimethylformamide, dimethylacetamide, acetonitrile], (4-iodobenzyloxy) triisopropylsilane (100g) from example-1, potassium carbonate (37.13g) [or sodium hydroxide, sodium carbonate, potassium hydroxide], copper iodide (0.005g) and L-Proline (0.012g) into round bottom flask at 20-25 ºC under nitrogen atmosphere. Stirred the reaction mass at 20-25 ºC under nitrogen for 15-25 minute and added ethyl 2-cyanoacetate (70.0g) at 25-30°C under nitrogen atmosphere. Heated the reaction mass under nitrogen atmosphere at 85-90°C for 24-48 hours. After completion of the reaction, cooled the reaction mass up to 25-30°C. Charged DM water (1000 mL) to the reaction mass & extracted with ethyl acetate (1000 mL X 2) at 25-30 ºC. Combined the organic layers, washed with water (1000ml), saturated brine solution (500 mL) at 25-30°C for 15-30 minute. Distilled out ethyl acetate under vacuum at 45-50°C. Degased the mass completely under vacuum at 55-60ºC to give title compound. Yield 96g.

Example 3: Preparation of ethyl 3-amino-2-(4-((triisopropylsilyloxy)methyl) phenyl) propanoate
Charged methanol (800 mL) [or ethanol, dimethylformamide, acetonitrile, dimethylsulfoxide, dimethylacetamide], ethyl 2-cyano-2-(4-((triisopropylsilyloxy) methyl) phenyl)acetate (80g) from example-2, aqueous ammonia (100.0 ml) [or NaOH or Sodium carbonate], and raney nickel (20.0g) into 2.0 L. hydrogenator at 25-30 ºC. Purged hydrogen pressure 4-6 kg/cm2 at 25-30°C. Heated the reaction mass at 40-45°C and maintained H2 pressure 4-6 Kg/cm2 for 6-12 hour and monitored the reaction by TLC. After completion of the reaction, cooled the reaction mass up to 25-30°C, released the hydrogen pressure, and flushed with nitrogen three to four times. Filtered the mass through hyflo and washed with methanol (800 ml) at 25-30°C. Charged filtrate into round bottom flask and distilled out methanol under vacuum at 45-50°C. Degas under vacuum at NMT 50°C for 45-60 minutes to give title compound. Yield (68.0g).

Example 4: Preparation of (S)-ethyl 3-amino-2-(4-((triisopropylsilyloxy) methyl) phenyl) propanoate
Charged mixture of ethanol (2400 ml) [alcoholic solvent, acetonitrile, ethyl acetate] and DM water (3000 ml), ethyl 3-amino-2-(4-((triisopropylsilyloxy)methyl) phenyl) propanoate (68.0g) from example-3 at 45-50°C into round bottom flask and stirred the mass till the clear solution is obtained. Added (+)-Dibenzoyl-D-tartaric acid (89.84g) at 45-50°C to the reaction mass, raised temperature up to 75-76°C and maintained the temperature 75-76°C for 4.0 hrs. Slowly cooled the mass up to 10°C and stirred the mass for 3 hrs at 10°C. Filtered the solid material and washed with mixture of ethanol and water (100 ml) at 10°C. Suck dried the wet material (70g) under vacuum at 25-30°C. Charged wet material (70.0g) in 4N RBF and added mixture of ethanol and water (5:1) at 25-30°C. Heated the mass up to 76°C till the clear solution is obtained. Cooled down immediately the mass up to 10°C. Stirred the mass at 10°C for 2-3 hrs. Filtered the solid mass and washed with mixture of ethanol and water (100 ml) at 10°C. Suck dried under vacuum at 25-30°C. Unloaded material and dried under vacuum at 45-50°C for 10-12 hrs.
Charged dried material (52g) in RBF at 25-30°C. Charged DM water (800.0 ml) and dichloromethane (800.0 ml) to the RBF at 25-30°C. Adjusted the pH 7.0-8.0 with 20% sodium carbonate solution (500.0 ml) at 25-30°C. After pH adjustment, stirred the mass for 15-30 minutes at 25-30°C. Allowed to settle the layer for 15-30 minute at 25-30°C. Separated the layers at 25-30°C. Aqueous layer extracted with dichloromethane (500ml) at 25-30°C. Combined the organic layers and washed with DM water (500.0 ml) at 25-30°C. Distilled out dichloromethane completely under vacuum at NMT 50°C and degassed under vacuum at NMT 50°C for 45-60 minute to give desired isomer. Yield-32.50g

Example-5: Preparation of Formula VI (R1 = hydrogen, R2 = boc, R3 = triisopropylsilyl, R4 =ethyl)
Charged dichloromethane (650.0 ml) [acetonitrile, tetrahydrofuran, toluene, example-4 compound (32.5.0 g) and trimethylamine 21.77g [or diisopropylethylamine, sodium hydroxide, potassium carbonate, sodium carbonate, dimethylaminopyridine, imidazole] at 25-30°C and stirred for 15-30 minute at 5-15°C. Slowly added Boc anhydride (19.50g) at 5-15°C in NLT 60 minutes. Stirred the reaction mass for 4-6 hrs. at 25-30°C. After reaction completion, charged saturated sodium bicarbonate solution (130 ml) to the reaction mass at 25-30°C. Stirred for 15-30 minute at 25-30°C and allowed to settle the layers for 15-30 minute at 25-30°C. Separated the layers at 25-30°C and distilled out the organic layer under vacuum at NMT 50°C to give title compound. Yield: 40.0g; purity 98 % by HPLC.

Example-6: Preparation of Formula VI (R1 = hydrogen, R2 = boc, R3 = triisopropylsilyl, R4 =Hydrogen)
Charged methanol 500ml [alcoholic solvent, protic solvent, tetrahyrofuran], example-5 compound (40.0 g) into round bottom flask. Stirred for 15-30 minutes at 10-20°C. Slowly charged lithium hydroxide 24.0g [NaOH, KOH] lot wise at 10-20°C within 45 minutes. Stirred the reaction mass for 4-6 hrs. at 25-30°C. After reaction completion, filter the reaction mass and distilled out filter completely under vacuum at NMT 50°C. Cooled the reaction mass at 25-30°C and charged water (250ml) at 25-30°C. Adjusted pH 2-3 by dil. HCl or Citric acid at 25-30°C, extracted with dichloromethane 325 ml X2 at 25-30°C and distilled out organic layer under vacuum at NMT 50°C to give title compound. Yield 30.0g; purity 98.2% by HPLC.

Example-7: Preparation of compound of formula II (R1 = hydrogen, R2 = boc, R3 = triisopropylsilyl, n = 1)
Charge dimethylformamide (300.0 ml) [or dimethylacetamide, dimethylsulfoxide, acetonitrile, pyridine] & example-6 compound (30.0 g) into round bottom flask and stirred for 15-30 minute at 25-30°C. Charged dimethylaminopyridine (5.5g) & EDC Hydrochloride (21.6) at 25-30°C. Slowly charged 6-aminoisoquinoline N-oxide (11.8g), stirred the reaction mass for 24-30 hours at 25-30°C. After reaction completion, filtered the reaction mass. Distilled out filter completely under vacuum at NMT 50°C and cooled the reaction mass at 25-30°C. Charged water 250ml at 25-30°C and extracted with ethyl acetate 500.0ml X 2 at 25-30°C. Combined the organic layers (Ethyl acetate), washed with saturated sodium bicarbonate solution 100ml at 25-30°C. Charge Organic layer in RBF at 25-30°C. Distilled out organic layer under vacuum at NMT 50°C to give title compound. Yield-35g; purity 98.8 % by HPLC.

Example 8: Preparation of compound of formula II (R1 = hydrogen, R2 = boc, R3 = H, n = 1)
Charged tetrahydrofuran (500.0 ml) [or acetonitrile, methyl tertiary butyl ether, dimethylformaide, ethyl acetate] & example-7 compound (35.0 g) into round bottom flask and stirred for 15-30 minutes at 25-30°C. Charged Tetrabutylammonium fluoride solution 1.0 M in tetrahydrofuran (90.30ml) at 25-30°C to the reaction mass and stirred the reaction mass for 10-12 hours at 25-30°C. After reaction completion, distilled out completely under vacuum at NMT 50°C. Cooled the reaction mass at 25-30°C, charged water 150ml at 25-30°C and extracted with dichloromethane 200 ml X 2 in reaction mass at 25-30°C. Combined the organic layers, washed with saturated sodium bicarbonate solution 100ml at 25-30°C and distilled out organic layer under vacuum at NMT 50°C to give title compound. Yield-25.0g; purity 99.1% by HPLC.

Example 9: Preparation of compound of formula II (R1 = hydrogen, R2 = boc, R3 = 2,4-dimethyl benzoyl, n = 1)
Charged methylene dichloride (525.0 ml) [or tetrahydrofuran, EDC, methyl tertiary butyl ether, ethyl acetate, acetonitrile], example-8 compound (25.0 g) into round bottom flask. Charged 2,4-dimethyl benzoic acid (9.5g) to it and stirred for 15-30 minute at 25-30°C. Charged dimethylaminopyridine (2.5g) [or imidazole, DBU] & EDC.HCl (20.0g) at 25-30°C. Stirred the reaction mass for 5-6 hours at 25-30°C. After reaction completion, filtered the reaction mass and distilled out filter completely under vacuum at NMT 50°C. Cooled the reaction mass at 25-30°C. Charged water (250ml) at 25-30°C to the mass and extracted with dichloromethane 300 ml X 2 at 25-30°C. Combined organic layers and washed with saturated sodium bicarbonate solution at 25-30°C. Distilled out organic layer under vacuum at NMT 50°C to give title compound. Yield-32.0g; purity 99 % by HPLC.

Example 10: Preparation of Netarsudil
Charged acetonitrile (400.0 ml), titanium tetra chloride (8.5ml) and stannous chloride (10.5g) in to round bottom flask at 25-30°C and stirred for 15min. Charged example-9 compound (30.0g) to the reaction mixture. Stirred the reaction mass for 2 hours at 25-30°C. After reaction completion, cooled the reaction mass at 5-10°C. Slowly charged saturated sodium carbonate solution (100ml) and ethyl acetate (400ml). Stirred the reaction mass 15-30 minutes at 25-30°C. Allowed to settle the layers for 15-30 minute at 25-30°C. Separated the organic layers (Ethyl acetate) at 25-30°C and distilled out organic layers under vacuum at NMT 50°C to give Netarsudil. Yield-25.0g; purity 99.8% by HPLC.

Example 11: Preparation of Netarsudil Dimesylate
Charged methanol (250.0 ml) & Netarsudil (25.0 g) to a round bottom flask. Stirred for 15-30 minutes at 25-30°C and added methyl sulfonic acid solution (10.63g in methanol 200ml) to it at 25-30°C. Stirred the reaction mass for 2-4 hours at 25-30°C under nitrogen atmosphere. Cooled the reaction mass 0-10°C under nitrogen atmosphere. Stirred the reaction mass for 2-4 hours at 0-10°C under nitrogen atmosphere. Filter the reaction mass under vacuum at 0-10°C under nitrogen atmosphere and washed with methanol (50ml) at 0-10°C under nitrogen atmosphere to Netarsudil dimesylate. Yield-15.0g; purity 99.9 % by HPLC.
,CLAIMS:We Claim:

1. A compound of Formula II & Formula VI or pharmaceutically acceptable salts thereof,
,
Formula II Formula VI
wherein,
n = 0, 1, 2;
R1 and R2 are independently or together selected from hydrogen, tertiary butoxy carbonyl, phthalimide, acetyl, benzylidene, benzyl, substituted benzyl, p-toluene sulfonyl, 2-nitrophenylsulphenyl, 2,4-dinitrobenzenesulfonyl, trityl, fluorenylmethoxycarbonyl (Fmoc), 2, 7-Di-tert-butyl-Fmoc, tetrachlorophthaloyl (TCP), benzothiazole-2-sulfonyl (Bts), p-nitrobenzyloxycarbonyl, 4-nitroveratryloxycarbonyl, benzyloxycarbonyl (Cbz), 9-(4-Bromophenyl)-9-fluorenyl (BrPhF), 2,4,6-trimethoxybenzyl (Tmob), monomethoxytrityl (Mmt), o-Nitrobenzyl;
R3 is independently selected from hydrogen, oxygen protecting group, or
,
wherein waved line shows point of attachment; R4 is selected from hydrogen, or lower alkyl group.

2. The compound as claimed in claim 1, wherein said compound of Formula II is represented by following formulae,
,
and compound of formula VI represented by following formulae,

wherein, R3 is as define above.

3. A process for the preparation of Netarsudil or pharmaceutically acceptable salt thereof, comprising the steps of:
a) condensing compound of Formula VI with 6-Aminoisoquinoline or its N-oxide in presence of activating agent to give compound of Formula II or its pharmaceutically acceptable salt,
,
Formula VI Formula II
wherein R1, R2 and R4 are as defined in claim 1; R3 is independently selected from hydrogen or oxygen protecting group;
b) reacting compound of Formula II or its pharmaceutically acceptable salt with compound of Formula A in presence of activating agent to give compound of Formula VIII,
; and
Formula II Formula A Formula VIII
wherein A is hydroxyl or halogen;
c) deprotecting compound of Formula VIII to Netarsudil of Formula I or pharmaceutically acceptable salt.

4. The process according to claim 3, oxygen protecting group is selected from the group of triisopropylsilane (TIPS), methoxymethyl ether, tetrahydropyranyl ether, t-butyl ether, allyl ether, benzyl ether, t-butyldimethylsilyl ether, t-butyldiphenylsilyl ether, acetic acid ester, pivalic acid ester, benzoic acid ester.

5. The process according to claim 3, activating agent is selected from the group of benzotriazole-1-yl-oxy-tris (dimethylamino)phosphoniumhexafluoro-phosphate (BOP), N,N'-dicyclohexylcarbodiimide (DCC), 1-hydroxibenzotriazol anhydrous(HOBt), N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide (EDC), 1-[bis(dimethylamino) methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxidhexafluorophosphate (HATU), 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU), 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafhexafluoro phosphate (HBTU) or mixtures thereof.

6. The process according to claim 3, wherein converting compound of formula IV to give Netarsudil of Formula I,
, and
b) optionally converting compound of Formula I to its pharmaceutically acceptable salts.

7. The process according to claims 3 and 6, deprotection is carried using hydrochloric acid, sulfuric acid, hydrobromic acid, formic acid, acetic acid, trifluoroacetic acid, titanium tetrachloride, tin (II) chloride or mixture thereof.

8. The process according to claim 3, wherein 6-aminoisoquinoline-N-oxide compound of Formula IX is prepared by a method, comprising the steps of:
a) reacting 6-bromo isoquinoline with hydrogen peroxide in presence of acid to give 6-bromo isoquinoline N-oxide (Formula B),
,
Formula B
b) reacting 6-bromo isoquinoline N-oxide (Formula B) with phthalimide in presence of base to give compound of Formula X,
, and
Formula B Formula X
c) deprotecting compound of Formula X to give compound of Formula IX,

Formula X Formula IX.

9. The process according to claim 8, base is selected from the group of potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, triethylamine, diisopropylethylamine, pyridine, dimethyl amino pyridine (DMAP) or mixtures thereof.

Dated 14th Day of May, 2024
For Mankind Pharma Ltd.

Dr. Anil Kumar

Chief Scientific Officer