Title of Invention	IMPROVED PROCESS FOR THE PREPARATION OF COENZYME Q10
Abstract	The present invention provides an improved process for the preparation of Coenzyme Q<sub>10</sub> (CoQ<sub>10</sub>) or Ubiquinone of formula (I) by condensing 2,3dimethoxy-5-methyl dihydroquinone with compound of formula (V) using a Lewis acid in the presence of mixture of two solvents followed by oxidizing to produce compound of formula

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Field of the Invention The present invention provides an improved process for the preparation of Coenzyme Q10 (CoQ10) or Ubiquinone of formula (I) Background of the invention Polyprenyl natural products, comprising a p-quinone head, play a vital role in biological processes of higher plants and animals. These quinones are inevitable in such living systems as they involve in the electron transport process for respiration and produce energy within the cell. In addition these natural products are also involved in blood clotting and oxidative phosphorylation. In this family, ubiquinone or coenzyme Q10 is well known redox carrier present in mitochondria of every cell in the human body. It plays an important role as an antioxidant by acting as a free radical scavenger. Adequate levels of CoQio must be maintained in the body to prevent the cellular damage resulting from normal metabolic processes. Also it has been found that the consequences of in-vivo deterioration can be substantial, as the levels of CoQio have been correlated with increased sensitivity to infection, strength of heart muscle. In recent past CoQ10 has been identified as the drug supplement in the treatment cardiovascular diseases, cancer, AIDS-related diseases, muscular dystrophy, etc. The structure of CoQ10 consists of a quinone ring attached to an isoprene side chain as shown in formula (I). CoQio closely resembles the members of the vitamin K group and tocopherylquinones, which are derived from tocopherols (vitamin E). In mammalian tissue the quinone ring of CoQio is synthesized from the amino acids, tyrosine and phenylalanine and the polyprenyl side chain is synthesized from acetyl-CoA. Large-scale production of CoQio via well-established fermentation and extraction processes is found to be more economic when compared to available total syntheses using chemical methods. However, the above said processes involves expensive infrastructure and hence total synthesis remains as an alternative option for the large-scale production. Owing to its wide range of pharmaceutical applications coenzyme Q10 (I) has drawn much attention from many pharmaceutical industries to develop a viable process for large-scale production. Past thirty years have witnessed remarkable increase in the consumption CoQio as a drug supplement for the treatment of various diseases. Consequently the synthetic organic chemists are making efforts, to develop viable synthetic methodologies to provide adequate material to meet the increasing requirement of CoQ10. As a result various methods of preparation were reported in the literature (US 2003/0073869, US 6,506,915, US 2002/0156302, US 6,545,184, US 5,547,580, US 4,952,712, US 4,270,003, US 4,163,864, US 4,039,573, US 3,998,858, JP 54104107, JP 07010800, or Synthesis 1991, 1130 etc). US 3549668 claim a process for the preparation of CoQ10. This patent also discloses a process for the preparation of solanesyl acetone (IV), a precursor of isodecaprenol (V), which involves reaction of solanesyl bromide (II) with ethyl acetoacetate (EAA), followed by saponification and decarboxylation. Reel. Trav. Chim. Pays-Bas 1993, 113, 153-161 discloses same process wherein anion of EAA generated using Na in ethanol. Zhurnal Organicheskoi Khimi 1988, 1172 uses sodium ethoxide. The preparation and handling of NaOEt needs special care as NaOEt is moisture sensitive and the use of Na in plant needs extra attention. Chemistry Express 1988, 3(11), 675-8 and JP 56092238A2 discloses a process for the preparation CoQ10 (I) from 2,3-dimethoxy-5-methylhydroquinone and isodecaprenol in nitroethane and octane. JP 53127891A2 discloses a process for the preparation CoQio by reacting isodecaprenol and 2,3-dimethoxy-5- methylhydroquinone in methylethyl ketone. Chemistry Letters 1982, 1131 discloses the usage of BF3.OEt2 in CC14 in polyprenyl rearrangement of 2,3-dimethoxy-4-hydroxy-5-methyl phenyl ethers to 2,3-dimethoxy-5-methyl-6-polyprenyl hydroquinone. Chemistry Letters 1988, 1597 reveals the use of mixed solvent of nitro methane and hexane in the synthesis of CoQ1o by the coupling of 2,3-dimethoxy-5-methylhydroquinone and isodecaprenol in the presence of a catalytic amount of BF3OEt2. Tetrahedron Letters 1992, 33, 4983-84 uses 1,4-dioxane for this condensation. Among various processes reported the following general process is most widely used: a. Synthesis 2,3-dimethoxy-5-methyl dihydroquinone, b. stereospecific synthesis of polyprenyl alcohol, c. condesation of the aromatic nucleus with alcohols of formula as shown in scheme I. Although various coupling methods have been tried with different solvent combination to introduce polyprenyl side chain into quinone nucleus the yield and purity of final compound is not satisfactory owing to byproducts formation, also they all require more than 6 equivalent of 2,3-dimethoxy-5-methylhydroquinone for the condensation reaction & column chromatography. With our research and intense investigation, we have achieved identifying acetonitrile/hexane combination as most suitable solvent system for the condensation reaction, which can address all the limitations discussed above, and produce the CoQio (I), which exhibits high stereo selectivity with good yields & excellent purity. Objectives of the Invention The main objective of the present invention is to provide a simple and commercially viable process for the large-scale production of pure CoQ10. Another objective of the present invention is to provide a process for preparation of ubiquinone, without employing the hazardous solvents like nitromethane, nitroethane, carbon tetrachloride, that are unsafe to use in manufacturing scales. Yet another objective of the present invention is to provide a process, which is capable of producing pure CoQio, by avoiding chromatographic technique. Still another objective of the present invention is to provide a purification process, which removes the impurities D and F as specified in the EP pharmacopoeia. Summary of the Invention Accordingly, the present invention provides simple and efficient stereo specific process for the preparation of pure CoQ10 of formula (I), the said process comprising the steps of (i) converting a solanesyl bromide (II) to solanesyl acetone (IV) by reacting solanesyl bromide with ethyl aceto acetate using NaOH and a solvent to produce compound of formula (III) followed by hydrolyzing the compound of formula (III) using a base and an alcoholic solvent, wherein the improvement lies in use of NaOH, (ii) reacting the compound of formula (IV) with vinyl magnesium bromide in a solvent to produce a compound of formula (V), (iii) condensing 2,3-dimethoxy-5-methyl dihydroquinone with compound of formula (V) using a Lewis acid in acetonitrile and an hydrocarbon solvent to produce compound of formula (VI), wherein the improvement consists of usage of acetonitrile, (vi) oxidizing the compound of formula (VI) using oxidizing agent and a solvent followed by purification to get coenzyme of formula (I). The process shown in Scheme II given below: Description of the Invention In an embodiment of the present invention the solvent used for conversion of compound of formula (II) to (III) in step (i) is selected from ether like isopropyl ether, diethyl ether, tetrahydrofuran, dimethoxyethane, 1,4-dioxane, toluene, hexane and the like. In another embodiment of the present invention the alcoholic solvent used for hydrolysis in step (i) is selected from methanol, ethanol, isopropyl alcohol and the like and the base used is selected from NaOH, KOH and the like. In still another embodiment of the present invention, the solanesyl acetone (IV) obtained can be purified by treating it with buffer solution like KH2P04, NaHPO4 followed by using alcoholic solvents like methanol, ethanol, and isopropyl alcohol by recrystalisation technique, or crystallization technique etc. In yet another embodiment of the present invention the solvent used in step (ii) is selected from isopropyl ether, diethyl ether, tetrahydrofuan, THF, toluene, hexane, dimethoxy ethane and the like or mixtures thereof. In yet another embodiment of the present invention the hydrocarbon solvent used in step (iii) is selected form hexane, heptane, octane, toluene, and mixture thereof. After surveying several solvent systems we found that a combination of hexane/acetonitrile is best system in terms of the quality and yield of the final product (I) and provides a non-hazardous process. Hexane/acetonitrile combination has been proved to be much better solvent system when compared any other solvents system reported in the literature. The Lewis acid used in this reaction is selected form BF3.OEt2, ZnCl2, TiCl4, AICI3, EtAlCl2, SnCl4, or similar reagents. In still another embodiment of the present invention, the oxidizing agent used in step (iv) is selected form FeCl3.6H20, CAN, CuCl2, Mn02, AgO, H202/I2, NaI04 and the solvent used is selected from hexane, toluene, octane, acetonitrile, alcohols such as methanol, ethanol or isopropyl alcohol, water or mixtures thereof. In yet another embodiment of the present invention the C0Q10 obtained is purified using alcoholic solvent such as methanol, isopropanol, 2-butanol and the like and by means crystallization / recrystallization. This purification steps helps to remove the impurities D and F (These impurities are common impurities which are present in all most all prior art processes) as specified in the EP pharmacopoeia. Most preferably recrystallization of impure CoQlO using 2-butanol efficiently removes the Impurities D and F. In another embodiment of the present invention the starting material solanesyl bromide can be prepared from the literature known in the prior art. The foregoing technique has been found to be attractive from commercial, technological and ecological perspective, and affords pure trans (E) isomer of CoQ10. Many other beneficial results can be obtained by applying disclosed invention in a different manner or by modifying the invention within the scope of disclosure. The present invention is illustrated with the following examples, which should not be construed for limiting the scope of the invention. Example 1: Preparation of Solanesyl acetone: To a stirred suspension of sodium hydroxide (10.4 g, 0.26 mol) in diisopropyl ether (700 mL) was added ethyl acetoacetate (72.4 g, 0.56 mol). The resultant mixture was heated at 40-42 °C for about lh and then cooled to 0-5 °C. A solution of solanesyl bromide (104.5 g, 0.15 mol) in diisopropyl ether (300 mL) was added slowly and heated at 60 °C till completion of reaction. The reaction mixture was cooled to room temperature, filtered and the filtrate was concentrated under reduced pressure to give solanesyl ester as brown color liquid contaminated with residual ethyl acetoacetate (145 g). The crude solanesyl ester was dissolved in isopropyl alcohol (350 mL) and cooled to 5-10 °C. A solution of potassium hydroxide (29.5 g, 0.74 mol) in water (300mL) was added. The resultant mixture was heated at 40-45 °C till the completion of reaction. The reaction mixture was cooled to room temperature and was added water (1400 mL). The aqueous layer was extracted with ethyl acetate (2x450 mL). The combined organic layers were washed with buffer solution, brine solution and water. The organic layer was concentrated under reduced pressure to yield crude solanesyl acetone (112 g, purity 89-92 %) as a brown color greasy material. The crude solanesyl acetone was purified using isopropanol and methanol to get pure solanesyl acetone (74.5 g, 74 % yield, HPLC purity: >97 %). Preparation of isodecaprenol: To a stirred solution of solanesyl acetone (100 g, 0.15 mol) in toluene (1.0 L), at 0 °C, was added a 1.0 M solution of vinyl magnesium bromide (224 mL, 0.224 mol) over a period of 20 min. The resultant mixture was stirred at 0-5 °C for about 30 min. After the completion of the reaction it was quenched with saturated ammonium chloride solution (400 mL) and the reaction mixture was allowed to stir at 0 °C for about 15 min. The mixture was diluted with EtOAc (500 mL) and the layers were separated. The organic layer was washed with KH2P04 solution, water and brine. The organic layer was dried over anhydrous sodium sulfate and the concentrated under reduced pressure to give crude isodecaprenol (105 g), which was purified using hexane to give isodecaprenol as pale brown color syrup (101 g, 97 % yield, HPLC purity: 91-94 %) Preparation of CoQ10: To a solution of 2,3-dimethoxy-5-methyl dihydroquinone (52.6 g, 0.286 mol) in CH3CN (150 mL) was added to a solution of isodecaprenol (100 g, 0.143 mol) in hexane and the resultant bi-phasic solution was allowed to come to 30 °C. A 10 % solution of BF3.OEt2 (150 mL) in CH3CN was added to the reaction mixture over a period of 15 min and the resultant mixture was stirred at 30 °C - 40 °C till completion of reaction. The hexane layer was separated and washed with acetonitrile and then diluted with isopropyl alcohol (500 mL). The mixture was treated with FeCl3.6H20 (62.5 g, 0.231 mol) at room temperature for about lh. The reaction mixture was poured in to ice cold water (1.0 L) and the layers were separated. The hexane layer was washed with NaHC03 solution (200 mL), water and brine (250 mL). The organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure to a volume of 500 mL and then subjected to charcoal treatment. Carbon was filtered and the filtrate was concentrated under reduced pressure to give orange syrup (66 g), which was dissolved in isopropyl alcohol and stirred at room temperature to precipitate the pure CoQ1o. The solid obtained was recrystallised using 2-butanol filtered and dried to give amorphous yellow powder ( HPLC purity: >98 %). Advantageous: • Only 2 mole of 2,3-dimethoxy-5-methyl dihydroquinone is used where as literatures suggests more than 6 mole equivalent of 2,3-dimethoxy-5-methyl dihydroquinone. • Use of acetonitrile, removes hazardous nitro methane. • Purification without column chromatography. • Use of 2-butanol in recrystallization removes impurities D and F as specified in the EP pharmacopoeia. (iii) condensing 2,3-dimethoxy-5-methyl dihydroquinone with compound of formula (V) using a Lewis acid in acetonitrile and an hydrocarbon solvent to produce compound of formula (VI), wherein the improvement consists of usage of acetonitrile, and (vi) treating the compound of formula (VI) with oxidizing agent and a solvent followed by purification to get coenzyme of formula (I). 2. A process as claimed in claim 1, wherein the solvent used for conversion of compound of formula (II) to (III) in step (i) is selected from isopropyl ether, diethyl ether, tetrahydrofuran, dimethoxyethane, 1,4-dioxane, toluene, hexane or mixtures thereof. 3. A process as claimed in claim 1, wherein the alcoholic solvent used for hydrolysis in step (i) is selected from methanol, ethanol, or isopropyl alcohol; and the base used is selected from NaOH or KOH. 4. A process as claimed in claim 1, wherein solvent used in step (ii) is selected from isopropyl ether, diethyl ether, tetrahydrofuran, THF, toluene, hexane, dimethoxy ethane or mixtures thereof. 5. A process as claimed in claim 1, wherein the hydrocarbon solvent used in step (iii) is selected form hexane, heptane, octane, or toluene. 6. A process as claimed in claim 1, wherein Lewis acid used in step (iii) selected form BF3.OEt2, ZnCl2, TiCl4, A1C13, EtAlCl2, or SnCl4. 7. A process as claimed in claim 1, wherein oxidizing agent used in step (iv) is selected form FeCl3.6H20, CAN, CuCl2, Mn02, AgO, H202/I2, or NaI04; and the solvent used in step (iv) is selected from hexane, toluene, octane, acetonitrile, alcohols such as methanol, ethanol or isopropyl alcohol, water or mixtures thereof. 8. A process for the purification of CoQlO by crystallizing impure CoQio using alcoholic solvents selected from methanol, iso-propanol or 2-butanol. 9. A process for the purification of CoQlO by crystallizing impure CoQio using 2- butanol. Dated this twenty ninth (29th) day of September 2004 for Orchid Chemicals & Pharmaceuticals Ltd., Dr. C. B. Rao Dy. Managing Director

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