Title of Invention

A NEW SEMI - SYNTHETIC METHOD OF PACLITAXEL AND DOCETAXEL

Abstract

A semi-synthetic method of Paclitaxel and Docetaxel involving oxazolination or Mitsunobu reaction of 2"-epi-intermediates wherein, 2"-epi-intermediates were synthesized based on the condensation reaction of protected 10-DAB III and novel chiral side chain of formula 2. Toluene and dicyclohexyl carbodiimide (DCC) were used as solvent and as condensation agent respectively. The method is simple, assuring high yield and suitable for industrial production.

Full Text

FORM 2 THE PATENTS ACT 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10 and rule 13) 1. TITLE OF THE INVENTION: "Anew semisynthetic method of Paclitaxel and Docetaxel" 2. APPLICANTS: (a) NAME: NAPROD LIFE SCIENCE CO., LTD. (b) NATIONALITY: Indian Company incorporated under the Indian Companies ACT, 1956 (c) ADDRESS: 304, Towncentre, Andheri-kurla Road, Andheri (E), Mumbai-400059, Maharashtra, India. (a) NAME: SHANGHAI PARLING PHARMA TECH CO., LTD. (b) NATIONALITY: China Company incorporated under the Chinese Companies Law (c) ADDRESS: Suite 2, No. 868 Zhenchen Road, Baoshan District, Shanghai, 200 444, China. 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed. Technical field of the invention: The present invention relates to semisynthetic process for the preparation of Paclitaxel and Docetaxel comprising condensation of protected 10-Deacetyl-baccatin-III (10-DAB) with 2S,3S-phenylsioserine as a source of C-13 side chain and replacement of 2'-hydroxy group from C-13 side chain using oxazolination or Mitsunobu reaction by inversion of configuration. Background and prior art: Paclitaxel and Docetaxel are the most effective anticancer drugs found so far. Paclitaxel is extracted from the plant of yew trees, which has low extracting content and also belongs to the national protected plants; therefore the chemical synthesis methods for Paclitaxel and Docetaxel become the research directions for many scientists. BocHN 0 6"H Docetaxel pho There are various synthetic routes for preparation of paclitaxel such as by converting 9-dihydro-13-acetylbaccatin III (9-DHAB) into 10-deacetylbaccatin III. But main drawback of such process is poor yields of final product. Thus, there is a need of an efficient method for preparation of Paclitaxel and Docetaxel. US 6784304 describes method of preparation of novel oxazolidines which is used in the preparation of C-13 acyloxy sidechain-bearing taxanes such as paclitaxel and analogs thereof and a methods of preparing the oxazolidines, as well as to novel methods of coupling the oxazolidines to form the C-13 sidechain-bearing taxanes. US 6576777 provides a semi-synthetic process to convert a naturally occurring taxane into a suitable starting compound for the synthesis of paclitaxel and related compounds. It is related to a process for the conversion of 9-dihydro-13-acetylbaccatin III into a 7-protected baccatin III, which can be used for the synthesis of taxol derivatives, e.g., paclitaxel, docetaxel, cephalomannine and other taxanes, which were structurally related to baccatin III. US 2006/00795 Al describes semisynthesis of Paclitaxel involving esteirification of condensation of protected baccatin III with oxazolidine derivatives followed by hydrolysis and acidic treatment to give paclitaxel derivative. Most of the prior art methods for the semisynthesis of paclitaxel and Docetaxel involve condensation of baccatin III derivatives with oxazolidine derivatives with Cis-chirality. But these methods give low yield of the final product. Therefore, there is a need of semisynthetic methods of Paclitaxel/Docetaxel which is high yielding with high efficiency and can be carried out industrially at low cost with mild reaction conditions. In the semisynthetic method of the present invention, condensation of trans-chiral side chain is more synthetically suitable than Cis-side chain. The invention is suitable with mild reactive conditions for industrial production. Summary of the invention: In one aspect of the invention, semisynthesis of Paclitaxel and Docetaxel comprises condensation 10-Deacetyl-baccatin-III (10-DAB) with 2S, 3S-phenylisoserine side chain at C-13 position. In second aspect of the invention, semisynthesis of Paclitaxel and Docetaxel comprises replacement of the configuration of side chain at 2'-OH group of condensation product by oxazolination or Mitsunobu reaction followed by deprotection. Detailed description of the invention: In an embodiment of the present invention, semisynthesis of Paclitaxel and Docetaxel comprises condensation of 10-DAB with 2S,3S-phenylisoserine side chain at C-13 position. In the second embodiment of the present invention, configuration of 2'-OH in the C-13 side chain of the condensation product is inverted by oxazolination or Mitsunobu reaction followed by deprotection to give Paclitaxel or Docetaxel. Paclitaxel or Docetaxel was synthesized through replacement of the configuration of side chain by oxazolination or Mitsunobu reaction followed by deprotection of all other protecting groups. In the preferred embodiment of the invention, the semisynthetic methods of Paclitaxel and Docetaxel provide the following steps: i) condensing protected 10-DAB of formula 1 with novel chiral side chain of formula 2 ; ii) deprotecting 2'-hydroxyl group to get compound in formula 4; iii) replacing 2'- hydroxyl group of C-13 side chain of compound of formula 4 by oxazolination or Mitsunobu reaction to give compound of formula 5; and iv) deprotecting compound of formula 5. Formula 3: Ph O OR O 0% *HN X X 3 Ihn^ R4HN' T °'" OR3 3 O OHO &W0 PhO^ R90 Ph O Formula 4: R4HN' T O'" OH 4 Ln Formula 5: 5 Ph ° Wherein, R1 is hydroxyl protecting group, for instance: tertbutylsilyl (TBS), triethylsilyl (TES), ethoxyethyl (EE), tetrahydropyranyl (THP), 2,2,2-trichloroethoxycarbonyl (Troc) or methoxymethyl (MOM); R2 is Ac or hydroxyl protecting group, for instance: TBS, TES, EE, THP, Troc or MOM; R3 is hydroxyl protection group, for instance: TBS, TES, EE, THP, Troc or MOM; R4 is benzoyl (Bz) or tertbutyloxycarbonyl (Boc); X is hydroxyl and thiol ester. Reaction process is schematically represented as follows: ^HN'V^O OR, R,0 PhO*^ 1 Ph 0 + R4HN^TXx OR3 Ph 0 OR3 3 o°i*5 cf Uo PhO*^ Paclitaxel Or Docetaxel Ph 0 i u w-ry^oR, ip u 0.^6 cfL-o In step i) condensation is carried out using carbodiimide as condensing agent such as dicyclohexyl carbodiimide and DMAP, wherein the equivalent of condensation agent and dehydrating agent is 1-10 equivalent and the equivalent of organic base is 1-10 equivalent (calculated in 10-DAB □) and the reaction is carried out at a temperature range of 30°C-40°C. In step ii) deprotection of 2'-hydroxyl group of C-13 side chain of compound 3 is carried out using alcohol preferably anhydrous alcohol and dilute acid such as hydrochloric acid to give compound of formula 4. In step iii) replacement of the configuration of 2'-hydroxyl group from the C-13 side chain of formula 4 is carried out using oxazoline reaction (for synthesis of Paclitaxel) using anhydrous pyridine and Vilsmeier reagent or using Mitsunobu reaction (synthesis of docetaxel) to give compound of formula 5. Deprotection of compound of formula 5 is carried out by refluxing in the mixture of acid and/or ethanol in the presence of catalyst such as zinc powder. In the semisynthetic method of the present invention, condensation of trans-chiral side chain is more synthetically suitable than cis-side chain. The invention is suitable with mild reactive conditions for industrial production. The present investigation is more specifically explained by following examples. However, it should be understood that the scope of the present invention is not limited by the examples in any manner. It will be appreciated by any person skilled in this art that the present investigation includes the following examples and further can be modified and altered within the technical concept of the present investigation. EXAMPLE: Protected 10-DAB and novel chiral side chain in formula 2 is from Xi'an Natural Field Bio-technique Co., Ltd. Example 1: Synthesis of Paclitaxel. Step 1: AcO AcO Ph O Ph O •OTroc Ph H OTBS ■OTroc OH OTBS HO' Ph H OTBS DCC.DMAP oPJfe tf'l-b Ph O" 2a 3a To a solution of compound la (50g) in 500mL of toluene, N, N'-Dicyclohexyl-Carbodiimide (DCC) (50g) and 50g of compound 2a was added. The mixture was stirred at 30°C for 8 hours. When the reaction was complete, water was added. The solution was filtered off to separate water, and extraction was carried out with ethyl acetate (lOOmL x 2). The organic layer was dried over MgS04 and evaporated to dryness under reduced pressure. 65g of compound 3a (i.e. Yield: 86.7%) were obtained by column chromatography. Step 2: AcO AcO Ph 0 OTroc .OTroc Ph O Ph H OTBS 0^6 &V-0 3a Ph o^ EtOH.HCI 0^)6 Cf UO 4a Ph°^ To a solution of 65g of compound 3a in 1000ml of anhydrous alcohol, 50 ml of 2N dilute hydrochloric acid was added. The reaction mixture was stirred at room temperature over night. When the reaction was complete, the mixture was neutralized to ph 7, and toluene was removed under reduced pressure. 50g of compound 4a (i.e. Yield: 85.4%) were obtained by column chromatography. Step 3: O x Prf^NH O AcO AcO Ph" O ^ O OH •° Prf^NH O \ JL^° OTroc iPyr.A/ilsmeier Reagent 7 II W-rTx/ ^OTroc2.HCI/reflux Prf^VT)'" * OH To a solution of compound 4a (50g) in anhydrous pyridine (1L), Vilsmeier reagent (50g) was added. The mixture was stirred at room temperature for 2 hours and then poured into ice water. Extraction was carried out with ethyl acetate and washed with dilute hydrochloride until pH of solution was 7. The solvent was removed under reduced pressure. The residue was dissolved in methanol to which l00mL of 0.1N hydrochloride was added and mixture was refluxed. When the reaction was complete, sodium bicarbonate was added to neutralize and solvent was removed under reduced pressure. 40g compound 5a (i.e. Yield: 80%) was obtained by chromatography. Step 4: O Ph O rVvV OTroc AcO Ph' OH Paclitaxel Jh0A. 5a Ph o' Zn/AcOH/MeOH To a solution of compound 5a (40g) in 50ml of acetic acid, and 500ml of methanol, zinc power (50g) was added. The mixture was refluxed for 1 hour, the solution was filtered, and the filtrate was neutralized with saturated sodium bicarbonate. The solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate, washed with water, brine and dried to give oil. The crude product was purified further by column chromatography to give a white solid Paclitaxel of (25g) (i.e 75.5%) yield with following physical parameters, M.p. 213-216 °C IR (KBr): 3482, 1732, 1653 cm-'; [a] D25: -49.2° 1H NMR (CDC13, 500M)8: 8.12 (d, J=7.9 Hz, 2H), 7.71 (d, J=7.9 Hz, 2H), 7.58 (t, J=7.2 Hz, 1H), 7.53 (m, 5H), 7.40 - 7.30 (m, 5H), 6.98 (d, J=8.7Hz, 1H), 6.25 (s, 1H), 6.18 (bt, J=8.9Hz, 1H), 5.75 (dd, J=8.7, 2.6Hz, 1H), 5.63 (d, J=7.1Hz, 1H), 4.92 (bd, J=8.8Hz, 1H), 4.75 (d, J=2.1Hz, 1H), 4.36 (dd, J=10.5, 6.7 Hz, 1H), 4.29 (d, J=8.4 Hz, 1H), 4.17(d, J=8.3Hz, 1H), 3.76 (d, J=7.0 Hz, 1H), 3.54 (bs, 1H), 2.51(ddd, J=15.3, 9.5, 5.8Hz, 1H), 2.43(bs, 1H), 2.35 (s, 1H), 2.33 (dd, J=15.3, 8.7Hz, 1H), 2.27 (dd, J=15.3, 8.7Hz, 1H), 2.25 (s, 3H), 2.20 (s, 3H), 1.90-1.85(m, 1H), 1.75 (s, 3H), 1.65 (s, 3H), 1.20 (s, 3H), 1.11 (s, 3H); 13C NMR (CDC13, 125M) 6203.5, 172.6, 171.2, 170.3, 167.1,167.0, 142.1, 137.8, 133.6, 133.6, 133.0, 132.0, 130.2, 129.1, 129.0,128.8, 128.7, 128.4, 127.1, 127.0, 84.4, 81.0, 79.0, 76.4, 75.4, 74.8,73.3, 72.3, 72.2, 58.6, 55.0, 45.6, 43.1, 35.6, 35.6, 26.8, 22.6, 21.8, 20.9, 14.9, 9.5. Example 2: Synthesis of Docetaxel. Stepl: Ph O OTBS 2b TrocO TrocO Ph O BocHN' Y vO OTBS ■OTroc OTroc OH DCC.HBT HO' 0^6 tfVo BocHN PhO" 3b PhO^ 1b To a solution of compound lb (50 g) in 500ml of toluene, 50g of 2-Hydrazinobenzothiazole (HBT) and 50g of N,N'-Dicyclohexyl-Carbodiimide (DCC) and 50g of protected 2S,3S-phenylisoserine of formula 2b was added. The reaction mixture was stirred at 30°C for 8 hours. To this mixture, water was added and the solution was filtered. The organic layer was dried over MgSO4 and evaporated to dryness under reduced pressure. 65g of compound 3b (i.e. Yield: 91%) were obtained by column chromatography. Step 2: TrocO TrocO Ph O BocHN' Y "O OH .OTroc .OTroc Ph O BocHN T O'" OTBS 0PJ6 cf\-b 3b Ph O^- HF/Pyr 04^6 cfuo 4b Ph0^ To a solution of compound 3b (65g) in 1000ml anhydrous dichloromethane, HF/Pyr (l0g) was added. The reaction mixture was stirred at room temperature over night. Compound 4b (50g) (i.e. Yield: 84.5%) was obtained after column chromatography. Step 3: Ph O BocHN' J ^0« HO 0Tr0C PPh3/DEAD B°CHN- ° OTroc 5b TrocO o^o tfUo 4b Ph (J TrocO O&X) 0s UO PhO' To a solution of compound 4b (50g) in IL of anhydrous dichloromethane, PPh3 (50g) and DEAD (50g) was added. When the reaction was complete, the organic layer was washed with water, brine and dried over MgSO4. Compound 5b (43g) (i.e. Yield: 86.0%) was obtained by column chromatography. Step 4: OTroc BocHN. Zn/AcOH/MeOH ► Ph' BocHN TrocO T 1 5b Pho^ oPJJo o°V-o Docetaxel ph o To a solution of compound 5b (40g) in 50ml of acetic acid, and 500ml of methanol, zinc power (50g) was added. The reaction mixture was refluxed for 1 hour. Mixture was then filtered, and the filtrate was neutralized with saturated sodium bicarbonate. The solvent was removed under reduced pressure. The residue was dissolved in ethyl acetate, washed with water, brine and dried to give oil. The crude product was purified further by column chromatography to give a white solid Docetaxel of (20g) (i.e 73.0%) yield with following physical parameters, M.p. 232-234 °C IR (KBr): 3400, 2900, 1710 cm-1; [a] D25:-36.2° 'H NMR (CDCl3, 500M) 8: 8.12 (m, 1H), 7.60 (m, 2H), 7.50 (m, 2H), 7.38 (m, 5H), 6.22 (t, J=9.0 Hz, 1H), 5.68 (d, J=7.0 Hz, 1H), 5.46 (d, J=9.0 Hz, 1H), 5.26 (d, J=9.0 Hz, 1H), 5.22 (s, 1H), 4.94 (d, J=9.0 Hz, 1H), 4.62 (m, 1H), 4.32 (d, J=9.0 Hz, 1H), 4.26 (m, 1H), 4.19 (d, J=9.0 Hz, 1H), 3.91 (d, J=7.0 Hz, 1H), 2.58 (m, 1H), 2.37 (s, 3H), 2.28 (m, 2H), 1.88 (s, 3H), 1.75 (s, 3H), 1.35 (s, 9H), 1.23 (s, 3H), 1.11 (s, 3H); 13C NMR (CDCI3, 125M) 8211.1, 172.7, 170.3, 167.0, 155.5, 138.6, 138.5, 136.0, 133.0, 130.2, 129.3 128.7, 127.9, 127.4, 126.9, 84.4, 81.1, 80.2, 78.9, 77.3, 75.1, 74.5, 73.9, 72.3, 71.8, 57.7, 56.6, 46.6, 43.1, 36.7, 35.8, 28.2, 26.5, 22.5, 20.7, 14.3, 9.9. Example 3: Synthesis of Paclitaxel Stepl: AcO AcO OTroc Ph O Ph H OTBS ■OTroc OH OTBS HO' Pl DCC.DMAP PhO' 2c 3c To a solution of compound la (50g) in 500mL of toluene, DCC (50g) and 50g of compound 2a was added. The mixture was stirred at 80°C for 8 hours. When the reaction was complete, water was added. The solution was filtered off to separate water, and extraction was carried out with ethyl acetate (l00mL x 2). The organic layer was dried over MgSO4 and evaporated to dryness under reduced pressure. 65 g of compound 3c were obtained by column chromatography. jficO q Ph OTroc AsO To a solution of 65g of compound 3c in 1000ml of anhydrous alcohol, 50 ml of 2N dilute hydrochloric acid was added. The reaction mixture was stirred at room temperature over night. When the reaction was complete, the mixture was neutralized to pH 7, and toluene was removed under reduced pressure. 50g of compound 4c were obtained by column chromatography. Conversion of 4c to paclitaxel is carried out similarly as in Example 1. Example 4: Synthesis of Docetaxel. Stepl: Ph O OTBS TrocO TrocO ,0 Ph O .OTroc 1 JJ DCC.HBT + BocHNfY~OH OTBS OTroc HO" 0^5 tfUO BocHN PhO' 3d PhO^- 1d To a solution of compound lb (50 g) in 500ml of toluene, 50g HBT and 50g DCC and 50g compound 2b was added. The reaction mixture was stirred at 80°C for 8 hours. To this mixture water was added and the solution was filtered. The organic layer was dried over MgSO4 and evaporated to dryness under reduced pressure. 65g of compound 3d were obtained by column chromatography. Step 2: OTroc Hr/v^Q" Boc 3d Ph o*^ TrocO Ph 0 \ X^J3 n-r OH 4cl Ph °^ To a solution of compound 3d (65g) in 1000ml anhydrous dichloromethane, HF/Pyr (lOg) was added. The reaction mixture was stirred at room temperature over night. Compound 4d (50g) was obtained after column chromatography. Conversion of 4d to Docetaxel was similarly carried out as in Example 2. It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and examples be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. We claim: 1. A semi-synthetic method of Paclitaxel and Docetaxel comprising following steps: i) condensing protected 10-DAB III of formula 1 with chiral side chain of formula 2 to give compound of formula 3; ii) deprotecting the compound of formula 3 at 2'-position of chiral side chain to form compound of formula 4; iii) compound of formula 5 is obtained through replacement of 2'-hydroxyl group of compound of formula 4; and iv) deprotecting compound of formula 5 to give Paclitaxel and Docetaxel. R,0 Formula 1: PhO' 1 Formula 2: Ph 0 R4HN/kfAx OR, R,0 Ph 0 R4HN Formula 3: 3 OOHO &U> PhO^ Ph 0 R20 Ph O II H R4HN i^O"- OH oMi cfVb Formula 5: 5 Ph ° Rl is TBS, TES, EE, THP, Troc or MOM; R2 is Ac, TBS, TES, EE, THP, Troc or MOM; R3 is TBS, TES, EE, THP, Troc, Ac or MOM; R4 is Bz or Boc. X is hydroxyl or thiol ester. 2. Semisynthetic method of claim 1, wherein the condensation in step (i) is carried out using carbodi-imide as condensing agent and dehydrating agent in the presence of catalyst such as organic base. 3. Semisynthetic method of claim 1 and 2, wherein condensation agent and dehydrating agent is present in 1-10 equivalent and organic base is present 1-10 equivalent to 10-DAB III. 4. Semisynthetic method of claim 1 and 2, wherein the carbodi-imide condensing agent is dicyclohexyl carbodiimide. 5. Semisynthetic method of claim 1 and 2, wherein said dehydrating agent is 2-Hydrazinobenzothiazole and said organic base is anhydrous or triethylamine. 6. Semisynthetic method of claim 1 and 2, wherein condensation reaction in step i) is carried out at temperature range of 30°C- 40°C. 7. Semisynthetic method of claim 1, wherein replacement of hydroxyl group is carried out by oxazoline reaction or Mitsunobu reaction. 8. Semisynthetic method of claim 1, wherein the method further involves deprotecting of 7-position of compound in formula 5 in step (iii) to give paclitaxel and deprotection of 7- and 10-position of compound of formula 5 to give Docetaxel. Abstract: A semi-synthetic method of Paclitaxel and Docetaxel involving oxazolination or Mitsunobu reaction of 2'-epi-intermediates wherein, 2'-epi-intermediates were synthesized based on the condensation reaction of protected 10-DAB III and novel chiral side chain of formula 2. Toluene and dicyclohexyl carbodiimide (DCC) were used as solvent and as condensation agent respectively. The method is simple, assuring high yield and suitable for industrial production.

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