Title of Invention

THE PROCESS FOR PURIFICATION OF PACLITAXEL.

Abstract

A process for the purification of paclitaxel comprising: (a) mixing crude paclitaxel of 40-50% w/w purity with a mixture of solvents selected from the group consisting of alkane and chlorinated alkane; (b) filtering the solid of step (a) followed by drying to obtain paclitaxel of 55-65% w/w purity; (c) repeating steps (a) and (b) one or more times to obtain paclitaxel of 60-70% w/w purity, (d) dissolving the solid obtained from step (c) in alkyl ketone followed by adding alkane thereto, filtering and drying the solid thus formed to obtain paclitaxel of 80-85% w/w purity; (e) repeating step (d) one or more times to obtain paclitaxel of 85-90% w/w purity; (f) dissolving the paclitaxel of 85-90% w/w purity obtained from step (e) in alkanol and then adding water, filtering and drying the solid thus formed, to obtain paclitaxel the purity of 97-98% w/w; and (g) dissolving the solid obtained from step (f) in alkyl ketone, filtering, followed by adding alkane to the filtrate, filtering and drying the solid thus formed to obtain pure paclitaxel of 98-100% w/w purity.

Full Text

FIELD OF THE INVNETION This invention relates to the process for purification of paclitaxel. BACKGROUND OF THE INVENTION Paclitaxel is an approved anticancer drug and is a natural product isolated from the bark of Yew tree. Since, it is available in very smal1 quantities from natural sources, semisynthetic methods have been developed to increase the yield and to meet the demands- Further, isolation of paclitaxel of pharmaceutical grade from both plants as uiel 1 as from semisynthetic crude paclitaxel is a great problem. In case of natural extracts, law concentration of paclitaxel along with high amount of structurally similar compounds requires tedious HPLC and/or chemical purifications- The semisynthetic crude paclitaxel also contains lots of degradation products of taxanaid structure. These are mainly formed during deprotection of coupled product, because the taxane nucleus is a fragile structure. Therefore, purification of crude paclitaxel also requires HPLC purification. The HPLC equipment are expensive to intal1 and run, and have limitation in scale up. The object of the present invention is to propose a process for the isolation of pharmaceutical grade pure paclitaxel from the semisynthetic crude paclitaxel and natural crude paclitaxel. Yet another object of this invention is to propose a simple-process for purification using solvents. Still another object of this invention is to propose a ' process 1 for purification which does not require any sophisticated instruments. BRIEF DESCRIPTION OF THE INVENTION 2 Paclitaxel is composed of two distinct units. One is baccatin, a taxane (3) , and other N-benzay 1-3-pheny 1 isoserine , the side chain connected to baccatin through ester linkage at C-13. The 13-hydroxy of baccatin is very difficult to esterify due to its spatial disposition. To selectively esterify 13-hydroxy, the other more active 7-hydraxy needs to be protected first. The functional groups of side chain also need to be protected in the forms which condense/couple smoothly with 13-hydroxy. The coupling product, the paclitaxel precursor is converted into paclitaxel by deprotection and often benzoylation. According to this invention there is provided a process for the purification of pad itaxel comprising: a) mixing crude paclitaxel with a mixture of solvents such as alkane and chlorinated alkane, fi1tering the sol id followed by drying to obtain paclitaxel of increased purity; b) repeating step (a) one or more times to obtain paclitaxel of i-ncreased-purity; c) dissolving the solid obtained from step (b) in alkyl ketone fallowed by adding alkane thereto, filtering and drying the solid thus formed to obtain paclitaxel of increased purity; d) repeating step (c) one or moretime to increase the purity of the paclitaxel; e) dissolving the paclitaxel obtained from step and water, filtering and drying the solid thus formed, to obtain paclitaxel of increased purity; f) dissolving the sol id obtained from step (e) in alkyl ketone, filtering, followed by adding alkane to the filtrate, filtering and drying the solid thus formed to obtain pure paclitaxel. In accordance with this invention a) paclitaxel of 40-50% w/w purity and 60-70% chroma tographic purity from semisynthetic or natural source are used for purification. Such material is mixed with a mixture of alkane and chlorinated alkane and stirred for several hours. The solid is filtered out and dried under vacuum. After this step, purity of crude goes up to 55-65% w/w. 3 b) The first step is repeated one mare time to raise the purity of crude up to 60-70% w/w. c) The solid obtained in step-2 is dissolved in alkyl ketone under stirring and then alkane is added. The stirring is continued for several hours. The precipitated solid is filtered out and dried under vacuum and after this step, the purity of crude goes up to 80-85% w/w. d) The step-3 is repeated one more time and after this step to raise the purity of crude up to 85-90% w/w. e) The solid obtained in step-4 is dissolved under stirring in alkanol and wat-e-t _is. added. The stirring is continued for several hours. The precipitated sol id is filtered out and dried under vacuum until water content goes below 5%. After this step, the purity of crude goes up to 97-98*/4 w/w. f) The sol id obtained in step-5 is dissolved in alkyl ketone and then filtered through celite. Alkane is then added under stirring to the filtrate. The sol id .precip i tated is filtered out and dried until the constant weight- The solid powder thus obtained meets all specification generally required in pharmaceutical grade material (98-100% w/w purity and 99-99.5% chromatographic purity with individual impurities less than 0.2% in HPLC analysis and water guide 1ines, and also passes ash analysis test), g) The last two steps are very critical steps and in case, material fails specification, the sequential repetition of these steps helps in achieving the desired purity level. 4 h) The overall yield in the end comes to approximately 80%. The mother liquors from step~5 is concentrated to remove methanol and the solid is filtered out. The mother liquor from step-6 is evaporated to obtain the solid residual mass. These solid are mixed and used for isolation of the second crop of pure paclitaxel (~10%) following consecutively the procedure given in sstep-5 and 6. The preferred alkane used are pentane or hexane; chlorinated alkane used is dischloromethane or chloroform; alkyl ketone is acetone or ethlyl methyl ketone and the preferred alkanol alkanol is methanol or ethanol. The invention will now be explained in greater detail with the help of the following non-limiting example. STEP: 1 (alkane:chlorinated alkane purification) To a stirred mixture of dichloromethane - hexane (1:9) crude paclitaxel 1-5kg (52% w/w purity and 66.5% chromatographic purity) is added under stirring. The stirring is continued for o 10-12 h at 20-25 C. The solid is filtered and dried under vacuum o at 50 C. This step is repeated to reach the purity 70-75% w/w. Yield : 980gm (w/w purity 75.3%). STEP:2 (alkane s alkyl ketone purification) Paclitaxel (980gm, obtained from step-1) is added to acetone 5 o L). The mixture is stirred at 30 C to get clear solution. Hexane (18L) is added slowly under stirring, A white precipitate appears. Stirring is continued at for additional 4 h. The o material is filtered and then dried at 60 C for 5-6 h. This step is repeated to reach the purity 90V. w/w. Yield: 790 gm (w/w purity 90. 8%) . STEP:3 (alkanol : water purification) Paclitaxel (790gm, obtained from step-2) is added to methanol o (23.5 L). The mixture is stirred at 30 C to get a clear solution. Water (23.S L) is added slowly under stirring. A white precipitate appears. Stirring is continued at for additional 4 h. The material is filtered and the wet cake is dissolved indichlaromethane (8.0L). The water layer is separated from o organic layer. The organic layer is evaporated and dried at 60 C far 3 h. Yield 730gm (w/w purity 98-2%). STEP:4 (alkane : alky 1 ketone purirication) Paclitaxel (730gm, obtained from step-3) is added to acetone o (14.6L). The mixture is stirred at 30 C to get clear solution and filter it through 10 micron filter paper. Hexane (33L) is added slowly under stirring. A white precipitate appears. Stirring is continued at for additional 4 h. The material is filter and then o dried at 60 C for 5-6 h. Yield 650gm (w/w purity 99-100%, chromatographic purity >99.5% and total impurity NMT 0.5%). 6 WE CLAIM: 1. A process for the purification of paclitaxel comprising: a) mixing crude paclitaxel of 40-50% w/w purity with a mixture of solvents selected from the group consisting of alkane and chlorinated alkane; b) filtering the solid of step(a) followed by drying to obtain paclitaxel of 55-65% w/w purity; c) repeating steps (a) and (b) one or more times to obtain paclitaxel of 60-70% w/w purity, d) dissolving the solid obtained from step (c ) in alkyl ketone followed by adding alkane thereto, filtering and drying the solid thus formed to obtain paclitaxel of 80-85% w/w purity; e) repeating step (d) one or more times to obtain paclitaxel of 85-90% w/w purity; f) dissolving the paclitaxel of 85-90% w/w purity obtained from step (e) in alkanol and then adding water, filtering and drying the solid thus formed, to obtain paclitaxel the purity of 97-98% w/w; and g) dissolving the solid obtained from step (f) in alkyl ketone, filtering, followed by adding alkane to the filtrate, filtering and drying the solid thus formed to obtain pure paclitaxel of 98-100% w/w purity. 2. The process as claimed in claim 1, wherein the alkane solvents used are preferable selected from pentane and hexane. 7 8 3. The process as claimed in claim 1, wherein the chlorinated alkane is preferably selected from dichloromethane, chloroform. 4. The process as claimed in claim 1, wherein the alkyl ketone is preferably selected from acetone, ethyl methyl ketone. 5. The process as claimed in claim 1, wherein the alkanol is preferably selected from methanol, ethanol. 6. The process as claimed in claim 1, wherein said crude paclitaxel is obtained from semisynthetic or natural sources. 7. The process for the purification of paclitaxel substantially as herein described. A process for the purification of paclitaxel comprising: (a) mixing crude paclitaxel of 40-50% w/w purity with a mixture of solvents selected from the group consisting of alkane and chlorinated alkane; (b) filtering the solid of step (a) followed by drying to obtain paclitaxel of 55-65% w/w purity; (c) repeating steps (a) and (b) one or more times to obtain paclitaxel of 60-70% w/w purity, (d) dissolving the solid obtained from step (c) in alkyl ketone followed by adding alkane thereto, filtering and drying the solid thus formed to obtain paclitaxel of 80-85% w/w purity; (e) repeating step (d) one or more times to obtain paclitaxel of 85-90% w/w purity; (f) dissolving the paclitaxel of 85-90% w/w purity obtained from step (e) in alkanol and then adding water, filtering and drying the solid thus formed, to obtain paclitaxel the purity of 97-98% w/w; and (g) dissolving the solid obtained from step (f) in alkyl ketone, filtering, followed by adding alkane to the filtrate, filtering and drying the solid thus formed to obtain pure paclitaxel of 98-100% w/w purity.

Documents:

00305-cal-2001-abstract.pdf

00305-cal-2001-claims.pdf

00305-cal-2001-correspondence.pdf

00305-cal-2001-description(complete).pdf

00305-cal-2001-description(provisional).pdf

00305-cal-2001-form-1.pdf

00305-cal-2001-form-18.pdf

00305-cal-2001-form-2.pdf

00305-cal-2001-form-26.pdf

00305-cal-2001-form-3.pdf

00305-cal-2001-form-5.pdf

00305-cal-2001-letters patent.pdf

00305-cal-2001-reply f.e.r.pdf

305-CAL-2001-(09-04-2012)-CORRESPONDENCE.pdf

305-CAL-2001-CORRESPONDENCE-1.1.pdf

305-CAL-2001-FORM 16.pdf