Field of the invention:

The present invention provides a process for the preparation of (3β)-17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate compound of formula-1.

Formula-1 The present invention also provides a novel polymorph of compound of formula-1 and process for its preparation.

Background of the invention:

(3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate is commonly known as abiraterone acetate. It is a steroid compound which inhibits selectively and efficiently the enzyme 17-ohydroxylase-C17-20-lyase, which catalyzes the conversion of dehydroepiandrosterone and androstenedione to testosterone. The inhibition of said enzyme causes a strong decrease of testosterone levels in the patient and therefore this drug is used in the treatment of certain hormone-dependent tumors resistant to chemotherapy such as prostate cancer.

This compound was disclosed for the first time in US5604213A, which also provides a synthetic process for its preparation including as last step the reaction of an enol Inflate with a pyridine borate by Suzuki coupling. However, this process is not viable in practice, mainly because of the difficulty in preparing the enol triflate at the 17-position.

This step, apart from proceeding with a poor conversion and low yield, gives place to the impurity tri-unsaturated in a 10% yield, which only may be removed by column chromatography. Further, the product obtained after the subsequent Suzuki coupling must also be purified by column chromatography according to the examples provided therein.

US5618807A discloses two alternative processes for the preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate.

The first process involves the reaction of dehydroepiandrosterone with hydrazine hydrate and catalytic amount of hydrazine sulfate provides dehydroepiandrosterone- 17-hydrazone, which upon treatment with iodine solution provides 17-iodo-androsta-5,16-dien-3(3-ol. Heating the resulting iodo compound with diethyl(3-pyridyl)borane in presence of bis(triphenylphosphine) palladium(II) chloride, aq.sodium carbonate in tetrahydrofuran by oil bath at 80°C for 48 hrs provides 17-(3-pyridyl)androsta-5,16-dien-3p-ol. The resulting compound is further recrystallized form toluene and provided the compound in only 56% yield. The hydroxy compound thus obtained on acetylation with acetyl chloride in presence of triethylamine and 4-dimethylaminopyridine in dry diethyl ether provides (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate. The said acetylation step takes 12 hrs for completion of the reaction.

The second process involves heating a mixture of iodo compound and diethyl(3-pyridyl)borane in presence of bis(triphenylphosphine)palladium(II) chloride, aq.sodium carbonate in tetrahydrofuran under argon atmosphere at 80°C for 4 days. The obtained compound is first crystallized from a mixture of methanol/acetonitrile and then recrystallized from toluene/methanol mixture and provided the product in only 57% yield. The resulting hydroxy compound is acetylated by adding acetic anhydride to a suspension of the hydroxy compound in dry pyridine, which takes 24 hrs for completion.

Further the said process involves the column chromatography technique for the purification of the final compound which is not suitable on commercial scale.
Hence there is a significant need in the art to develop a simple process which provides the product in higher yield and purity in lesser reaction time and avoids the column chromatography technique for the purification of intermediates as well as final compound to reduce the time cycle and increase yield and purity.

US5604213 patent discloses (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate having M.R. 144-145°C. But there is no other characteristic data provided for the same in the said patent.

Later CN101768199A discloses crystalline form-A, B, C, D of Abiraterone acetate, CN102558275A discloses a-crystalline form, CN102321142A discloses crystalline form-E and CN102336801A discloses crystalline form-I of Abiraterone acetate.

All the above said polymorphs obtained by crystallizing from different solvents are seems to be similar.

Hence, there is still a significant need in the art to develop novel crystalline forms of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate.

The present inventors surprisingly found novel crystalline form of (3β)-17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate compound of formula-1.

Polymorphs are distinct solids having the same molecular formula yet having distinct advantageous physical properties compared to other polymorphic forms of the same compound. The difference in the physical properties of different polymorphic forms results from the orientation and intermolecular interactions of adjacent molecules in the bulk solid.

Polymorphism, the occurrence of different crystal forms, is a property of some molecules and molecular complexes. A single molecule may give rise to a variety of polymorphic forms having distinct crystal structures and physical properties like melting point, X-ray diffraction pattern, infrared absorption and solid state NMR spectrum. One polymorphic form may give rise to thermal behavior different from that of another polymorphic form.
Thermal behavior can be measured in the laboratory by such techniques as capillary melting point, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) as well as content of solvent in the polymorphic form, which have been used to distinguish polymorphic forms.

It is known in the art that X-ray powder diffraction pattern may be obtained which has one or more measurement errors depending on measurement conditions (such as equipment, sample preparation or machine used). In particular, it is generally known that intensities in an X-ray powder diffraction pattern may fluctuate depending on measurement conditions and sample preparation. For example, persons skilled in the art of X-ray powder diffraction will realize that the relative intensities of the peaks may vary according to the orientation of the sample under test and on the type and setting of the instrument used. The skilled person will also realize that the position of reflections can be affected by the precise height at which the sample sits in the diffractometer and the zero calibration of the diffractometer. The surface planarity of the sample may also have a small effect. Hence a person skilled in the art will appreciate that the diffraction pattern data presented herein is not to be construed as absolute and any crystalline form that provides a powder diffraction pattern substantially identical to those disclosed herein fall within the scope of the present disclosure.

Generally, a measurement error of a diffraction angle in an X-ray powder diffraction pattern is typically ± 0.2° of 2-theta.

Advantages of the present invention:

• The main advantage of the present invention is it avoids the usage of column chromatography technique for the purification of Abiraterone as well as Abiraterone acetate.

• The condensation of (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 to provide Abiraterone and acetylation of the obtained Abiraterone to Abiraterone acetate takes considerably lesser reaction time and provided the corresponding end products in high yield and purity.

• The crystalline form-M of the present invention is stable and non-hygroscopic in nature, hence is highly advantageous for formulators.

Brief description of the invention:

The first aspect of the present invention is to provide crystalline form of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, herein after referred as crystalline form-M.

The second aspect of the present invention is to provide an improved process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3β)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst and a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent in presence of a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) purifying the compound of formula-1 from a suitable solvent or mixture of solvents to provide pure compound of formula-1.

The third aspect of the present invention is to provide a process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst and a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent in presence of a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) treating the compound of formula-1 with a suitable HC1 source in a suitable solvent to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la,

d) optionally purifying the compound of formula-1 a from a suitable solvent,

e) neutralizing the acid-addition salt obtained in step-c) or step-d) by treating it with a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

The fourth aspect of the present invention is to provide a process for the preparation of crystalline form-M of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

The fifth aspect of the present invention is to provide crystalline form of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la, herein after designated as form-S.

Brief description of the drawings:

Figure-1: Illustrates the X-ray powder diffraction pattern of non-micronized crystalline form-M of (3p)-17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate compound of formula-1.

Figure-2: Illustrates the X-ray powder diffraction pattern of micronized crystalline form-M of (3p)-17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate compound of formula-1.

Figure-3: Illustrates the X-ray powder diffraction pattern of (3p)-17-(3pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained according to the process disclosed in US5604213.

Figure-4: Illustrates the X-ray powder diffraction pattern of crystalline form-S of (3p)-17-(3-pyridinyl) androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la.

Detailed description of the invention:

The term "suitable solvent" used in the present invention refers to "hydrocarbon solvents" such as n-pentane, n-hexane, n-heptane, cyclohexane, methyl cyclohexane, cycloheptane, pet ether, benzene, chlorobenzene, toluene, xylene and the like; "ether solvents" such as dimethyl ether, diethyl ether, diisopropyl ether, methyl tert-butyl ether, ethyl tert-butyl ether, di-tert-butyl ether, dimethoxy methane, 1,2-dimethoxy ethane (monoglyme), diglyme, 1,4-dioxane, tetrahydrofuran, 2-methyl tetrahydrofuran, morpholine and the like; "ester solvents" such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, iso-butyl acetate, tert-butyl acetate, diethyl carbonate and the like; "polar-aprotic solvents" such as dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), hexamethylphosphoramide (HMPA) and the like; "nitrile solvents" such as acetonitrile, propionitrile, butyronitrile, isobutyronitrile and like; "chloro solvents" such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride and the like; "ketone solvents" such as acetone, methyl ethyl ketone, diethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone and the like; "alcoholic solvents" such as methanol, ethanol, n-propanol, isopropanol, n-butanol, iso-butanol, tert-butanol, 2-pentanol, ethylene glycol, diethylene glycol, propylene glycol, 2-ethyl hexanol, benzyl alcohol and the like; "polar solvents" such as water; or mixtures thereof.

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 and the like; "alkali metal bicarbonates" such as sodium bicarbonate, potassium 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 tert.butoxide, potassium tert.butoxide and the like; "alkali metal hydrides" such as sodium hydride, potassium hydride and the like; "alkali metal amides" such as sodium amide, potassium amide, lithium amide, lithium diisopropyl amide (LDA) and the like; "alkali metal phosphates" such as disodium hydrogen phosphate, dipotassiumhydrogen phosphate; and "organic bases" selected from but not limited to methyl amine, diisopropyl amine, diisopropylethyl amine (DIPEA), diisobutylamine, triethylamine, tert.butyl amine, pyridine, 4-dimethylaminopyridine (DMAP), N-methyl morpholine (NMM), 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU), l,5-diazabicyclo[4.3.0]non-5-ene (DBN), l,4-diazabicyclo[2.2.2] octane (DABCO), imidazole; or mixtures thereof.

The first aspect of the present invention provides crystalline form-M of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, characterized by its powder X-ray diffraction pattern having peaks at 4.5, 5.8, 8.6, 9.1, 11.6, 12.0, 14.8, 15.1, 15.9, 16.3, 17.2, 17.8, 18.4, 19.1, 19.3, 21.7, 21.9, 22.4, 23.0 and 27.5 ±0.2 degrees of 2-theta.

Polymorphs of a pharmaceutical solid may have different physical and solid state chemical (reactivity) properties. The most stable polymorphic form of a drug substance is often used because it has the lowest potential for conversion from one polymorphic form to another while the metastable form may be used to enhance the bioavailability.

The present invention provides stable crystalline form of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

It is known in the art that X-ray powder diffraction pattern may be obtained which has one or more measurement errors depending on measurement conditions (such as equipment, sample preparation or machine used). In particular, it is generally known that intensities in an X-ray powder diffraction pattern may fluctuate depending on measurement conditions and sample preparation. For example, persons skilled in the art of X-ray powder diffraction will realize that the relative intensities of the peaks may vary according to the orientation of the sample under test and on the type and setting of the instrument used. The skilled person will also realize that the position of reflections can be affected by the precise height at which the sample sits in the diffractometer and the zero calibration of the diffractometer. The surface planarity of the sample may also have a small effect. Hence a person skilled in the art will appreciate that the diffraction pattern data presented herein is not to be construed as absolute and any crystalline form that provides a powder diffraction pattern substantially identical to those disclosed herein fall within the scope of the present disclosure.

Generally, a measurement error of a diffraction angle in an X-ray powder diffraction pattern is typically ± 0.2° of 2-theta.

The second aspect of the present invention provides an improved process for the preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3β)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst and a suitable base in a suitable solvent to provide (3β)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent in presence of a suitable base in a suitable solvent to provide (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) purifying the compound of formula-1 from a suitable solvent or mixture of solvents to provide pure compound of formula-1.

Wherein, in step-a) the suitable catalyst is selected from but not limited to Pd(PPh3)2Cl27 Pd(PPh3)4) Pd(OAc)2, Pd(OH)2, Pd2(dba)3j Pd(dppe)2Cl2, Pd(dppf)Cl2, Pd(dppf)Cl2.CH2Cl2, Pd(dcypp)Cl2, Pd(PhCN)2Cl2 and Pd(CH3CN)2Cl2; the suitable base is selected from hydroxides, alkoxides, carbonates, bicarbonates and acetates of alkali metals or mixtures thereof; the suitable solvent is selected from ether solvents, nitrile solvents, ester solvents, hydrocarbon solvents, polar solvents or mixtures thereof;

In step-b) the suitable acetylating agent is selected from acetyl chloride, acetic anhydride, acetic acid; the suitable base is selected from organic bases; the suitable solvent is selected from hydrocarbon solvents, ether solvents, ester solvents or mixtures thereof;

In step-c) the suitable solvent is selected from hydrocarbon solvents, alcoholic solvents, polar solvents, ester solvents, chloro solvents or mixtures thereof.

In step-c) of the second aspect, the purification process comprises adding water to the reaction mixture obtained in step-b), separating the organic and aqueous layer and distilling off the solvent completely from the organic layer to form a residue. The compound is crystallized by adding methanol to the residue followed by water. The obtained crystals are further purified from a mixture of ethyl acetate and n-heptane to get pure compound of formula-1.

The acetylation of (3β)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4 can also be carried out by treating it with acetic acid in presence of a suitable dehydrating agent such as dicyclohexylcarbodiimide, thionyl chloride, phosphoryl chloride, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HC1) in presence of a suitable organic or inorganic base in a suitable solvent selected from hydrocarbon solvents, ether solvents, ester solvents or their mixtures to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

The third aspect of the present invention provides a process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3β)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst and a suitable base in a suitable solvent to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent in presence of a suitable base in a suitable solvent to provide (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) treating the compound of formula-1 with a suitable HC1 source in a suitable solvent to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la,

d) optionally purifying the compound of formula-1 a from a suitable solvent,

e) neutralizing the acid-addition salt obtained in step-c) or step-d) by treating it with a suitable base in a suitable solvent to provide (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

Wherein, in step-a) & step-b) the suitable catalyst, the suitable acetylating agent, the suitable base and the suitable solvent are same as defined in step-a) & step-b) respectively of the second aspect of the present invention;

In step-c) the suitable HC1 source is selected from ethyl acetate-HCl, isopropanol-HCl, ethanolic HC1, aq.HCl, HC1 gas;

In step-c) & step-d) the suitable solvent is selected form alcoholic solvents;

In step-e) the suitable base is selected form hydroxides, carbonates and bicarbonates of alkali metals; the suitable solvent is selected from alcoholic solvents, polar solvents, ester solvents or mixtures thereof.

Step-a) of the process disclosed in second and third aspects of the present invention is carried out optionally in presence of a Siliabond metal Scavenger. The "SiliaBond metal Scavenger" is used for removing residual metals from post reactions. The toxic nature of transition metals has led to the reduction of tolerated residual concentration in active pharmaceutical ingredients (APIs) to single digit ppm.

The SiliaBond Metal Scavenger used in the present invention is selected from SiliaBond amine, SiliaBond diamine, SiliaBond triaminetetraacetic Acid, SiliaBond thiol, SiliaBond thiourea, SiliaBond propyl bromide and SiliaBond dimercaptotriazine. Thiophenol resin can also be used as a metal scavenger for the said reaction.

Two processes have been exemplified in US5618807A for the preparation of (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol which involves the condensation of (3β)-17-iodo-androsta-5,16-dien-3-ol with 3-(diethylboryl)pyridine. The said two processes involves the usage of Pd(PPh3)2Cl2 as a catalyst, tetrahydrofuran as the solvent system and sodium carbonate as a base. Among the two exemplified processes, one process takes 48 hrs and the other one takes 4 days for the completion of the reaction. Further both the processes ended up with only 56% & 57% yield respectively of the reaction product.

Such longer reaction times and lower yield of the product makes the process commercially not viable.

The present inventors when carried out the said reaction step using mixture of aqueous solutions of sodium carbonate and sodium hydroxide as base and tetrahydrofuran/acetonitrile as solvent system we surprisingly found that the said reaction completes within 90 min, which is significantly less when compared to the prior-art process.

Further the end product, i.e., the compound of formula-4 is obtained in about 85-90% of the yield with 98.5% of purity by HPLC.

The preferred embodiment of the present invention provides a process for the preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of Pd(PPh3)2Cl2, sodium carbonate and sodium hydroxide in a mixture of tetrahydrofuran and acetonitrile to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with acetic anhydride in presence of triethylamine and 4-dimethyalminopyridine in toluene to provide (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) treating the compound of formula-1 with isopropyl alcohol-HCl in isopropyl alcohol to provide (3μ)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la,

d) purifying the compound of formula-la by recrystallizing it from isopropyl alcohol,

e) neutralizing the hydrochloride salt obtained in step-d) by treating it with sodium bicarbonate solution in a mixture of methanol and water to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

The iodo intermediate compound of formula-2 of the present invention can be synthesized by any of the processes known in the art. For example it can be prepared as per the process disclosed in US5618807A.

The process described in step-e) of the third aspect of the present invention further comprises purifying the compound of formula-1 from a suitable solvent.

The fourth aspect of the present invention provides a process for the preparation of crystalline form-M of (3β)-17-(3-pyridinyl)androsta~5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Adding dichloromethane to (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained in step-c) of second aspect or step-e) of the third aspect or obtained by any of the prior reported processes,

b) treating the reaction mixture with charcoal,

c) filtering the reaction mixture,

d) distilling off the solvent completely form the filtrate,

e) adding n-heptane to the compound obtained in step-d) and stirring the reaction mixture,

f) cooling the reaction mixture to a suitable temperature,

g) filtering the solid to get crystalline form-M of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

Wherein, the suitable temperature in step-f) ranges between -20°C to 20°C, preferably 0°C to 15°C more preferably 10-15°C.

The crystalline form-M of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained in the present invention is stable and non-hygroscopic in nature. The non-hygroscopic nature of the compound is determined by the method described in European pharmacopeia.

The non-hygroscopic nature of crystalline form-M obtained by the process of the present invention is confirmed by the fact that there is no substantial change in the water content even after the compound is placed in a desiccator containing aqueous ammonium chloride solution for a period of 24 hours at 80±2% relative humidity (RH). The water content of crystalline form-M produced according to the present invention is increased by 0.1% in 24 hours, which confirms the non-hygroscopic nature of the compound. The said characteristic nature is always an advantageous property for formulations.

The fifth aspect of the present invention is to provide crystalline form-S of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-la, characterized by its powder X-ray diffraction pattern having peaks at 4.5, 7.8, 12.3, 15.0, 15.8, 16.1, 16.7, 17.1, 18.4, 19.7, 20.4, 23.9, 25.1, 26.1 and 28.4 ± 0.2 degrees of 2-theta.

The said crystalline form-S is further characterized by its powder X-ray diffraction pattern substantially in accordance with figure-4.

PXRD analysis of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 and its hydrochloride salt compound of formula-la was carried out using BRUKER/AXS X-Ray diffractometer using Cu Ka radiation of wavelength 1.5406 A° and continuous scan speed of 0.03°/min.
(3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 of the present invention was analyzed by HPLC under the following conditions; Apparatus: A liquid chromatographic system is to be equipped with variable wavelength UV-detector; Column: Symmetry Shield RP18 250x4.6 mm, 5 μm or equivalent; Flow rate: 1.0 mL/minute; Wave length: 252 nm; Injection volume: 5 μL; Column temperature: 25°C; Run time: 38 minutes; Mobile phase-A: Weigh accurately 1.36 gm of potassium dihydrogen phosphate in 1000 ml of milli-Q-water, mix well and filter through 0.45u nylon membrane filter paper. Mobile phase-B: Acetonitrile: water (90:10 v/v); Diluent: Methanol; Elution: Gradient.

The particle size distribution of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 of the present invention was measured using Malvern Mastersizer 2000 instrument.

(3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 and its hydrochloride salt compound of formula-la of the present invention can be further micronized or milled to get the desired particle size to achieve desired solubility profile based on different forms of pharmaceutical composition requirements. Techniques that may be used for particle size reduction include, but not limited to ball mills, roller and hammer mills and jet mills. Milling or micronization may be performed before drying or after the completion of drying of the product.

The present invention is schematically represented as follows: Scheme-I:

Examples:

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.

Example-1: Preparation of (3β)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol (Formula-4)
(3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 (20 gm) was added to a mixture of tetrahydrofuran (100 ml) and acetonitrile (100 ml) at 25-30°C. Aq. sodium carbonate solution (29.69 gm of sodium carbonate in 140 ml of water) followed by aq.sodium hydroxide solution (1.6 gm of sodium hydroxide in 40 ml of water) were added to the reaction mixture at 25-30°C and stirred for 15 min at the same temperature. Bis(triphenylphosphine)palIadium(II) dichloride (0.35 gm) followed by 3-(diethylboryl)pyridine compound of formula-3 (8.2 gm) were added to the reaction mixture at 25-30°C. Heated the reaction mixture to 70-75°C and stirred for 90 min at the same temperature. After completion of the reaction, dichloromethane was added to the reaction mixture at 25-30°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. Distilled off the solvent completely from the combined organic layer under reduced pressure. Ethyl acetate (30 ml) was added to the reaction mixture at 25-30°C and stirred for 15 min at the same temperature. Pet ether (300 ml) was added to the reaction mixture at 25-30°C and stirred for 10 min at the same temperature. Cooled the reaction mixture to 0-5°C and stirred for 45 min at the same temperature. Filtered the precipitated solid, washed with pet ether and then dried to get the title compound. Yield: 15.1 gm; Purity by HPLC: 98.5%.

Example-2: Preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate (Formula-1)

Acetic anhydride (8.75 gm), triethylamine (21.7 gm) followed by 4-dimethylamino pyridine (3.5 gm) were added to a pre-cooled solution of (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4 (25 gm) in toluene (250 ml) at 0-10°C and stirred for 2 hrs at the same temperature. After completion of the reaction, water was slowly added to the reaction mixture at 25-30°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 toluene. Separated the organic and aqueous layers and combined the organic layers. Washed the combined organic layers with water and distilled off the solvent completely from the organic layer under reduced pressure to get the title compound. Yield: 22.4 gm; Purity by HPLC: 95.55%.

Example-3: Purification of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate (Formula-1)

Methanol (200 ml) was added to (3(3)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained in example-2 (20 gm) at 25-30°C. Water (200 ml) was added to the reaction mixture at 25-30°C and stirred for 45 min at the same temperature. Filtered the precipitated solid and washed with water to get the title compound. Yield: 18.0 gm; M.R: 136-139°C; Purity by HPLC: 99.64%.

Example-4: Purification of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate (Formula-1)

Ethyl acetate (12.5 ml) and n-heptane (50 ml) added to (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained in example-3 (15 gm) at 25-30°C. Cooled the reaction mixture to 0-5 °C and stirred for 30 min at the same temperature. Filtered the precipitated solid, washed with n-heptane and suck-dried the compound. Filtered the precipitated solid, washed with n-heptane and then dried to get the title compound. Yield: 13.5 gm; M.R: 142-143°C; Purity by HPLC: 99.89%.

Example-5: Preparation of crystalline form-M of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate (Formula-1)

(3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1 obtained by the process of example-4 (25 gm) was added to dichloromethane (125 ml) at 25-30°C and stirred for 15 min at the same temperature. Charcoal (2.5 gm) was added to the reaction mixture at 25-30° and stirred for 30 min at the same temperature. Filtered the reaction mixture through hyflow bed. Distilled off the solvent completely from the filtrate under reduced pressure and co-distilled with n-heptane. 25 ml of n-heptane was added to the obtained compound at 25-30°C, slowly cooled the reaction mixture to 10-15°C and stirred for 45 min at the same temperature. Filtered the precipitated solid, washed with n-heptane and dried to get the pure title compound. Yield: 23.5 gm.

Example-6: Preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride (Formula-la)

Acetic anhydride (8.75 gm), triethylamine (21.7 gm) followed by 4-dimethylamino pyridine (3.5 gm) were added to a pre-cooled solution of (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4 (25 gm) in toluene (250 ml) at 0-10°C and stirred for 2 hrs at the same temperature. Water was added to the reaction mixture and stirred for 10 min. Both the aqueous and toluene layers were separated and the aqueous layer was extracted with dichloromethane. Combined the organic layers and washed with water. Distilled off the solvent completely from the organic layer under reduced pressure. Ethyl acetate (125 ml) followed by methyl tert.butyl ether (125 ml) were added to the obtained compound at 25-30°C. Cooled the reaction mixture to 0-5°C, isopropyl alcohol-HCl (3.39 gm) was slowly added and stirred for 30 min at the same temperature. Filtered the precipitated solid, washed with methyl tertbutyl ether. Isopropyl alcohol (300 ml) was added to the obtained compound, heated the reaction mixture to 65-70°C and stirred for 45 min at the same temperature. Cooled the reaction mixture to 25-30°C and stirred for 30 min at the same temperature. Filtered the reaction mixture and the compound was washed with isopropyl alcohol and dried to get the title compound. Yield: 24.0 gm.

Example-7: Preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride (Formula-la)

Toluene (250 ml), (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4 (25 gm), acetic acid (8.58 gm), dicyclohexylcarbodiimide (29.5 gm) and 4-dimethylaminopyridine (3.5 gm) were charged into a clean and dry RBF at 25-30°C and stirred for 1 hr at the same temperature. After completion of the reaction, filtered the reaction mixture. Water was slowly added to the filtrate at 25-30°C and stirred for 10 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 water. Distilled off the solvent completely form the organic layer under reduced pressure. Isopropyl alcohol (250 ml) was added to the obtained compound at 25-30°C. Cooled the reaction mixture to 0-5°C, isopropyl alcohol-HC1 (3.39 gm) was slowly added and stirred for 30 min at the same temperature. Filtered the precipitated solid, washed with methyl tert.butyl ether. Isopropyl alcohol (300 ml) was added to the obtained compound, heated the reaction mixture to 65-70°C and stirred for 45 min at the same temperature. Cooled the reaction mixture to 25-30°C and stirred for 30 min at the same temperature. Filtered the reaction mixture, washed the compound with isopropyl alcohol and then dried to get the title compound. The PXRD pattern of the obtained compound is shown in figure-4. Yield: 25.0 gm; M.R: 225-231°C; Purity by HPLC: 99.83%.

Example-8: Preparation of (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate (Formula-1)

(3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride compound of formula-la (15 gm) was dissolved in a mixture of methanol (75 ml) and water (150 ml) at 25-30°C. Basified the reaction mixture by using 7% sodium bicarbonate solution. Dichloromethane (150 ml) was added to the reaction mixture at 20-25°C and stirred for 5 min at the same temperature. Both the organic and aqueous layers were separated and the aqueous layer was extracted with dichloromethane. Combined the organic layers and washed with water. Charcoal (2 gm) was added to the organic layer at 25-30°C and stirred for 15 min at the same temperature. Filtered the reaction mixture through hyflow bed and distilled off the solvent completely from the filtrate under reduced pressure and co-distilled with n-heptane. 15 ml of n-heptane was added to the obtained compound, cooled the reaction mixture to 10-15°C and stirred for 45 min at the same temperature. Filtered the precipitated solid, washed with n-heptane and dried to get the title compound.
Yield: 11.5 gm; M.R: 145.5-146.3°C; Purity by HPLC: 99.8%; Water content: 0.22% w/w; Particle size distribution (before micronization): D(0.1) is 6.20 μm; D(0.5) is 21.08μm; D(0.9) is 52.35 μm; Particle size distribution (after micronization): D(0.1) is 0.46μm; D(0.5) is 4.90μm; D(0.9) is 13.34μm.

We Claim:
1. Crystalline form-M of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, characterized by;

a) its powder X-ray diffraction pattern having peaks at about 4.5, 5.8, 8.6, 9.1, 11.6, 12.0, 14.8, 15.1, 15.9, 16.3, 17.2, 17.8, 18.4, 19.1, 19.3, 21.7, 21.9, 22.4, 23.0 and 27.5 ± 0.2 degrees of 2-theta, and

b) its powder X-ray diffraction pattern substantially in accordance with figure-2.

2. A process for the preparation of (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4, comprising of reacting the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of Pd(PPh3)2Cl2, aq.sodium carbonate and aq.sodium hydroxide in a mixture of tetrahydrofuran and acetonitrile to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4.

3. A process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst selected from Pd(PPh3)2Cl2, Pd(PPh3)4, Pd(OAc)2, Pd(OAc)2(PPh3)2) Pd(OH)2, Pd2(dba)3, Pd(dppe)2Cl2, Pd(dppf)Cl2, Pd(dppf)Cl2.CH2Cl2, Pd(dcypp)Cl2, Pd(PhCN)2Cl2 and Pd(CH3CN)2Cl2 and a suitable base selected from hydroxides, alkoxides, carbonates, bicarbonates and acetates of alkali metals or their mixtures in a suitable solvent selected from ether solvents, nitrile solvents, ester solvents, hydrocarbon solvents, polar solvents or their mixtures to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent selected from acetyl chloride, acetic anhydride, acetic acid in presence of a suitable organic base in a suitable solvent selected from hydrocarbon solvents, ether solvents, ester solvents or their mixtures to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl
acetate compound of formula-1,

c) treating the compound of formula-1 with a suitable HC1 source selected from ethyl acetate-HCl, isopropanol-HCl, ethanolic HO, aq.HCl, HC1 gas in isopropyl alcohol to provide (3β )-17-(3-pyridinyl)androsta-5, 16-dien-3-yl acetate hydrochloride salt compound of formula-la,

d) optionally purifying the compound of formula-la from isopropyl alcohol,

e) neutralizing the hydrochloride salt compound of formula-la obtained in step-c) or step-d) by treating it with a suitable base selected form hydroxides, carbonates and bicarbonates of alkali metals in a suitable solvent selected from alcoholic solvents, polar solvents, ester solvents or their mixtures to provide (3p)-17-(3-pyridinyi)androsta-5,16-dien-3-yl acetate compound of formula-1,

f) optionally purifying the compound of formula-1 from a suitable solvent to provide pure compound of formula-1.

4. A process for the preparation of (3β )-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of Pd(PPh3)2Cl2, sodium carbonate and sodium hydroxide in a mixture of tetrahydrofuran and acetonitrile to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with acetic anhydride in presence of triethylamine and 4-dimethyalminopyridine in toluene to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) treating the compound of formula-1 with isopropyl alcohol-HCl in isopropyl alcohol to provide (3β)-17.-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride salt compound of formula-1 a,

d) purifying the compound of formula-1 a by recrystallizing it from isopropyl alcohol,

e) neutralizing the hydrochloride salt obtained in step-d) by treating it with sodium bicarbonate solution in a mixture of methanol and water to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

5. A process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of formula-3 in presence of a suitable catalyst selected from Pd(PPh3)2Cl2, Pd(PPh3)4, Pd(OAc)2, Pd(OAc)2(PPh3)2, Pd(OH)2 and a suitable base selected from hydroxides, alkoxides, carbonates, bicarbonates and acetates of alkali metals or their mixtures in a suitable solvent selected from ether solvents, nitrile solvents, ester solvents, hydrocarbon solvents, polar solvents or their mixtures to provide (3β )-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with a suitable acetylating agent selected from acetyl chloride, acetic anhydride, acetic acid in presence of a suitable organic base in a suitable solvent selected from hydrocarbon solvents, ether solvents, ester solvents or their mixtures to provide (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) purifying the compound of formula-1 from a suitable solvent or mixture of solvents to provide pure compound of formula-1.

6. The process according to claim-5, characterized in that the purification process comprises;

a) Adding water to the reaction mixture obtained in step-b),

b) separating the organic and aqueous layers and distilling off the solvent completely from the organic layer,

c) adding methanol to the compound obtained in step-b),

d) adding water to the reaction mixture,

e) filtering the reaction mixture,

f) adding ethyl acetate followed by n-heptane to the obtained compound,

g) stirring the reaction mixture,

h) filtering the solid to get pure compound of formula-1.

7. A process for the preparation of (3β )-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Condensing the (3p)-17-iodo-androsta-5,16-dien-3-ol compound of formula-2 with 3-(diethylboryl)pyridine compound of forniula-3 in presence of Pd(PPh3)2Cl2, sodium carbonate and sodium hydroxide in a mixture of tetrahydrofuran and acetonitrile to provide (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4,

b) acetylating the compound of formula-4 by treating it with acetic anhydride in presence of triethylamine and 4-dimethyalminopyridine in toluene to provide (3β)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1,

c) adding water to the reaction mixture obtained in step-b),

d) separating the organic and aqueous layers and distilling off the solvent completely from the organic layer,

e) adding methanol to the compound obtained in step-d),

f) adding water to the reaction mixture,

g) filtering the reaction mixture,

h) adding ethyl acetate followed by n-heptane to the obtained compound,

i) stirring the reaction mixture,

j) filtering the solid to get pure compound of formula-1.

8. A process for the preparation of crystalline form-M of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of;

a) Adding dichloromethane to (3β )-17-(3 -pyridinyl)androsta-5,16-dien-3 -yl acetate compound of formula-1 obtained in step-e) of claim-4 or step-j) of claim-7 or obtained by any of the prior reported processes,

b) treating the reaction mixture with charcoal,

c) filtering the reaction mixture,

d) distilling off the solvent completely form the filtrate,

e) adding n-heptane to the compound obtained in step-d) and stirring the reaction mixture, 0 cooling the reaction mixture to a suitable temperature preferably -15°C to 20°C, more preferably 10-15°C, g) filtering the solid to get crystalline form-M of (3β )-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.

9. Crystalline form-S of (3β )-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate hydrochloride, characterized by;

a) Its powder X-ray diffraction pattern having peaks at 4.5, 7.8, 12.3, 15.0, 15.8, 16.1, 16.7, 17.1, 18.4, 19.7,20.4,23.9,25.1 ,26.1 and 28.4 ±0.2 degrees of 2-theta, and

b) its powder X-ray diffraction pattern substantially in accordance with figure-4.

10. A process for the preparation of (3p)-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1, comprising of acetylating the (3p)-17-(3-pyridinyl)-androsta-5,16-dien-3-ol compound of formula-4 with acetic acid in presence of a suitable dehydrating agent such as dicyclohexylcarbodiimide, thionyl chloride, phosphoryl chloride, l-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HC1) and a suitable organic or inorganic base in a suitable solvent selected from hydrocarbon solvents, ether solvents, ester solvents or their mixtures to provide (3β )-17-(3-pyridinyl)androsta-5,16-dien-3-yl acetate compound of formula-1.