Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07J—STEROIDS
  • C07J43/00—Normal steroids having a nitrogen-containing hetero ring spiro-condensed or not condensed with the cyclopenta(a)hydrophenanthrene skeleton
  • C07J43/003—Normal steroids having a nitrogen-containing hetero ring spiro-condensed or not condensed with the cyclopenta(a)hydrophenanthrene skeleton not condensed
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07J—STEROIDS
  • C07J1/00—Normal steroids containing carbon, hydrogen, halogen or oxygen, not substituted in position 17 beta by a carbon atom, e.g. estrane, androstane
  • C07J1/0003—Androstane derivatives
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07J—STEROIDS
  • C07J1/00—Normal steroids containing carbon, hydrogen, halogen or oxygen, not substituted in position 17 beta by a carbon atom, e.g. estrane, androstane
  • C07J1/0003—Androstane derivatives
  • C07J1/0011—Androstane derivatives substituted in position 17 by a keto group
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07J—STEROIDS
  • C07J31/00—Normal steroids containing one or more sulfur atoms not belonging to a hetero ring
  • C07J31/006—Normal steroids containing one or more sulfur atoms not belonging to a hetero ring not covered by C07J31/003

Definitions

• the present invention relates to improvement in the process of preparation of abiraterone acetate or a pharmaceutically acceptable salt thereof wherein the improvement comprises purifying the crude 3-P-acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate by crystallization from a solvent to obtain acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate as a crystalline solid and converting it to abiraterone acetate or pharmaceutically acceptable salt thereof.
• Form ula I is a potent selective, orally active inhibitor of the key enzyme in testosterone synthesis, 17a- hydroxylase-C 17,20-lyase, also known as steroid 17a-monooxygenase inhibitor or Human Cytochrome P450
• WO-A-93/20097 discloses the synthesis of a compound of Formula:
• Stange et al advocates against the use of simple bases such as pyridine, lutidine or triethylamine, as these give undesirable by-products at the triflate stage.
• Stang et al. recommend the use of hindered base ie: 2,6-di-tert-bUtyl-4-methylpyridine (DTBMP) instead, in spite of that fact that this base is expensive.
• DTBMP 2,6-di-tert-bUtyl-4-methylpyridine
• WO-A-95/09178 suggests replacing the triflate with a corresponding vinyl iodide intermediate, and uses this to make compounds by reacting this with a (3-pyridyl)-substituted borane of
• R represents a hydrogen atom or an alkyl group of 1-4 carbon atoms and Z 1 and
• l Z ⁇ independently represent hydroxy or alkoxy or alkyl of 1-3 carbon atoms each or Z and Z 2 together represent an alkylenedioxy group of 2 or 3 carbon atoms. However, column chromatography is required for this process also.
• US patent 7,700,766; Chinese patent applications CN102558274, CN102731605, CN 103059090, CN103193849 and CN102030798 disclose preparation of abiraterone acetate starting from dehydroepiandrosterone-3-acetate, converting it to 3-P-acetoxyandrosta-5,16-diene- 1 7-yl trifluoromethane sulphonate followed by coupling with diethyl-(3-pyridyl)-borane in presence of a Palladium catalyst.
• the present invention provides an improvement in the process of preparation of abiraterone acetate or a pharmaceutically acceptable salt thereof which process comprises a first step in which deh droepiandrosterone-3 -acetate (DHEAA) of Formula II
• Formula II is inflated in the presence of a base and a solvent to form crude 3-P-acetoxyandrosta-5,16- diene- 1 7-yl trifluoromethane sulphonate (Formual III), which is also referred as the thriflate intermediate in the present specification,
• the previous workers have not envisaged preparation of crystalline solid of the triflate intermediate by simple crystallization.
• Present invention provides a purification process by crystallization to yield a high purity discrete solid triflate intermediate without the need for any chromatographic purification.
• This discrete solid triflate intermediate has significant impact in achieving a superior purity and a pharmaceutically elegant color of abiraterone acetate besides other desired critical quality attributes as per ICH guidelines, thus obviating any chromatography techniques of purification taught in prior art.
• the present invention provides a simple, economical and commercially scalable process for preparation of Abiraterone acetate or pharmaceutically acceptable salts thereof.
• an improvement in the process of preparation of abiraterone acetate or a pharmaceutically acceptable salt thereof which process comprises a first step in which dehydroepiandrosterone-3 -acetate (DHEAA) is triflated in the presence of a base and a solvent to form crude 3 ⁇ -acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate and a second step wherein the crude 3-P-acetoxyandrosta-5, 16- diene- 17-yl trifluoromethane sulphonate is converted to abiraterone acetate or a salt thereof, wherein the improvement comprises an intermediate step of purifying the crude 3- ⁇ - acetoxyandrosta-5, 16-diene-17-yl trifluoromethane sulphonate by crystallization from a solvent to obtain acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate as a
• the triflate intermediate obtained in most of the prior art processes is isolated in crude form (mostly in form of oil) and is directly taken for next step without subjecting it to purification.
• the crude oil contains unreacted starting material DHEAA along with other impurities and decomposed products.
• the present invention provides a simple process of purification of 3- -acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate by crystallizing it form a solvent without subjecting it to chromatographic purification.
• the process yields a solid triflate intermediate in purity greater than 98 %.
• Handling of oily intermediate in commercial scale has disadvantages like difficulty in storage and transferring into different reaction vessels. Handling of solid in comparison to oil is much easier. The advantage becomes multifold when tonnage quantities of material is involved during commercial level production.
• first step involves reacting dehydroepiandrosterone-3-acetate (DHEAA) with a inflating agent selected from triflic anhydride, triflic chloride or triflic acid.
• DHEAA dehydroepiandrosterone-3-acetate
• the '766 patent has demonstrated that base having pKa of its conjugate acid less than 5.21 at 25 H C are not suitable for the reaction as they lead to more competing reactions causing complications.
• the '766 patent further states that reactions performed in ethers and hydrocarbons solvent showed problems with solubility of the reactant along with their reactivity and suggest that chlorinated solvents are the optimum solvents for the reaction.
• DHEAA is trflated in the presence of a base in an aromatic hydrocarbon solvent. It was found that for a successful subsequent intermediate step of crystallization it was necessary to optimise the first step to form a crude 3-P-acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate which has amenable to crystallization and purification thereof. This optimization can be achieved by proper selection of conditions namely the base, the solvent and the ratio of the DHEAA to inflating agent.
• suitable base for the first step included organic bases like triethylamine, diisopropylethyl amine, pyridine, 2,6-luitidine, ⁇ , ⁇ -dimethylaniline, N,N- diethylaniline, 2,6-di-tert-butyl-4-methylpyridine and the like.
• organic bases like triethylamine, diisopropylethyl amine, pyridine, 2,6-luitidine, ⁇ , ⁇ -dimethylaniline, N,N- diethylaniline, 2,6-di-tert-butyl-4-methylpyridine and the like.
• Suitable solvents included aromatic hydrocarbon solvent selected from toluene, xylene, mixtures thereof and the like. Present inventors have found that the first step can be optimized in order to form
• the ratio of DHEAA: inflating agent is atleast 1 :2. More preferably, the ratio of DHEAA: inflating agent is in the range of 1 :2 to 1 :4. Most preferably, the ratio of DHEAA: triflating agent is 1 :2.5.
• the solvent used in the intermediate crystallization step is a mixture of a water miscible organic solvent and water. More preferably, water miscible solvent is a ketone or an alcohol. Most preferably, ketone is acetone and the alcohol is isopropyl alcohol.
• the improvement further comprises monitoring the unreacted DHEAA during the the first step and obtaining and purifying crude3- -acetoxyandrosta-5,16-diene-17-yl trifluoromethane sulphonate after less than 5% DHEAA remains unreacted.
• the ratio of DHEAA: triflating agent used in first step is an important factor to drive the reaction to a stage where more than 95 % of DHEAA is consumed in the reaction.
• the ratio of DHEAA: triflating agent should atleast be 1 :2 for more than 95 % conversion of DHEAA.
• the preferred embodiments of the improvement of the present invention helps to attain faster reaction rate.
• the present improvent in the process enables production of commercial scale batch of the triflate intermediate in one shift of 24 h or less than that.
• One of the major side reaction during the triflating step is elimination reaction which yields an impurity of a compound of Formula IV.
• the recommended dose of ZYTIGA (Abiraterone acetate) is 1,000 mg (four 250 mg tablets) administered orally once daily is high. Hence, the content of impurity in the product are required to be maintained at very low level.
• Purification of the triflate intermediate by crystallization with solvent as provided by the present improvement yields a product with less than 0.10 % of impurity of Formula IV.
• the content of the impuirty of compound of Formula IV in the triflate intermediate is less than 0.08%.
• the solid crystalline triflate intermediate have a HPLC purity of more than 99 % and most preferably more than 99.5 %.
• the triflate intermediate thus formed can be converted into Abiraterone acetate or pharmaceutically acceptable salts thereof by the processes known in the art. For instance, the triflate intermediate is subjected to coupling with with diethyl-(3-pyridyl)-borarie in presence of a Palladium catalyst in a suitable solvent.
• Palladium catalyst can be /i/ ' .s(triphenylphosphine)palladium(II) dichloride [Pd(PPh 3 ) 2 Cl 2 )] and suitable solvent can be tetrahydrofuran (THF).
• suitable solvent can be tetrahydrofuran (THF).
• THF tetrahydrofuran
• Use of pure crystalline solid triflate intermediate for the preparation of abiraterone acetate enables the present inventors to use lesser quantity of diethyl-(3-pyridyl)-borane.
• the '766 patent uses 1.7 molar equivalent of diethyl-(3-pyridyl)-borane with respect to the triflate intermediate whereas, the present improvement in the process enables to use only 1.05 molar equivalents.
• the discrete solid triflate intermediate with HPLC purity >97% and impurity of compound of Formula IV less than ⁇ 0.5% has significant impact in achieving
• T he crude Abiraterone acetate obtained in second step can be purified by recrystallization successively from n-Heptane followed by Acetone: water (80:20). Alternatively, after work up, the reaction mixture is directly used, to prepare the p-TSA salt of Abiraterone acetate which further treated with base to yield abiraterone acetate having > 99.5% purity by HPLC.
• Abiraterone acetate or pharmaceutically acceptable salt thereof prepared by the improvement of the present invention has a HPLC purity of 99 %, preferably more than 99.5 % and most preferably more than 99.8 %.
• the triflate intermediate is defined as a compound of Formula III
• Abiraterone acetate is the product formed in the reaction mixture when the triflate intermediate of Formula III is subjected to coupling with diethyl-(3- pyridyl)-borane in presence of palladium catalyst and/or isolated from the reaction mixture by any known technique under the purview of a skilled artisan like extracting the reaction mixture with a water immiscible solvent, washing it with water and concentrating the solvent, without carrying out any further purification by way of recrystallization, any chromatographic puri fication or the like.
• the triene impurity is a compound of Formula V
• Triflic anhydride (213.43g, 0.756 moles) was added to a stirred solution of Dehydroepiandrosterone acetate (II) (l OOg, 0.3026 moles) in Toluene at 0-2 °C.
• II Dehydroepiandrosterone acetate
• a solution of N,N-Dimethylaniline(82.5g,, 0.680) dissolved in Toluene was added over a period of 20-30 minutes at 3-7 °C. Resulting reaction mixture was stirred for about 90 minutes at 3-7 °C. After completion of reaction, water was added to quench the reaction and the biphasic solution was separated at room temperature. The product enriched organic layer was washed with 2N HC1 followed by Brine solution.
• the product enriched organic layer was concentrated and degassed under reduced pressure below 45 °C.
• the residual mass was dissolved in Acetone: Water mixture (80:20, 20 volumes) at 40-45 °C, filtered hot to remove any suspended matter and the filtrate solution was cooled to - 10 to -8 °C. After maintaining the temperature for about 75 minutes the crystallized solid was filtered, washed with water and dried under vacuum below 40°C to obtain the product in the form of a solid.. (85g).
• the crude product was dissolved in IPA:Water mixture (80:20, 15 volumes) at 70-80 °C, treated with charcoal and cooled to 5-10 °C. After maintain for 3-5 hours the product was filtered, washed with water and dried under reduced pressure below 45°C to obtain pure (III), (yield 68 g 48.5% Th)
• Buffer solution Transfer 1.15 g of ammonium dihydrogen ortho phosphate in to a 1000 ml volumetric flask. Dissolve inand dilute up to mark with water. Adjust the pH of the solution to 3.00 + 0.10 with dilute ortho phosphoric acid solution.
• Triflic anhydride 32.01 kg was added to a stirred solution of Dehydroepiandrosterone acetate ( ⁇ ) (15 kg) in Toluene at 0-2 °C.
• ⁇ Dehydroepiandrosterone acetate
• N,N-Dimethylaniline (12.37 kg) dissolved in Toluene was added over a period of 20-30 minutes at 3-7 °C.
• Resulting reaction mixture was stirred for about 90 minutes at 3-7 °C.
• After completion of reaction water was added to quench the reaction and the layers were separated at room temperature.
• the product enriched organic layer was washed with 2N HC1 followed by brine solution.
• the product enriched organic layer was concentrated and degassed under reduced pressure below 45°C.
• the degassed oily mass was stirred in Methanol (800 ml) and was heated at 45-55°C after adding charcoal to it.
• the precipitated solid along with charcoal was filtered and washed with Methanol (200 ml).
• Water (450 ml) was slowly added to the filtrate at 40-50°C under stirring.
• the resulting suspension was maintained at 20-25°C for 3 hours and filtered the solid. Filtered solid was washed with water and dried under reduced pressure at 55-65°C to obtain crude Abiraterone acetate.
• Obtained Abiraterone acetate further purified by direct purification using heptane or optionally using salt screen purification as described in specification.
• EXAMPLE 5 Optional purification by salt screening p-Toluenesulfonic acid(20.4 g) was added to a stirred solution of crude Abiraterone acetate(40 g) dissolved in Toluene(400 ml) at 15-20°C and maintained for 15-30 minutes. Added Hexane (400 ml) to it and stirred the suspension for 45-60 minutes. Filtered the solid and washed with hexane. Product cake was suck dried under nitrogen atmosphere. The p-TSA salt was suspended in water and Toluene mixture and treated with sodium bicarbonate. The product enriched organic layer was washed with brine solution followed by treatment of Anhydrous sodium sulphate and charcoal.

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• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
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• 2014
  • 2014-06-24 IN IN2133MU2013 patent/IN2013MU02133A/en unknown
  • 2014-06-24 JP JP2016522965A patent/JP2016527213A/ja active Pending
  • 2014-06-24 WO PCT/IN2014/000420 patent/WO2014207762A1/en not_active Ceased
  • 2014-06-24 EP EP14816900.6A patent/EP3013844A4/en not_active Withdrawn
  • 2014-06-24 US US14/392,210 patent/US20160176915A1/en not_active Abandoned

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