Field of the invention This invention in general relates to a novel solvate of sumatriptan succinate. More particularly, but without restriction to the particular embodiments herein after described in accordance with the best mode of practice, the present invention is directed to an ethanol solvate of sumatriptan succinate and a process for preparing the sumatriptan salt using the same.
Background of the invention The indole derivatives are used in the treatment of migrane. It has been suggested that the pain of migrane may be associated with excessive dilatation of the cranial vasculature.
The indole derivatives are selective 5HTi-like receptors agonists and exhibit selective vasoconstrictor activity, which has been described in the art as useful in the treatment of migrane. The selection of indole molecule compound having two specific substituents, namely the methylaminosulphonylmethyl group at the 5-position of the indole molecule and the N,N-dimethylaminoethyl substituent at the 3-position, wherein said compound (Sumatriptan) having a combination has highly advantageous properties for the treatment of migrane, which is having the following structure:

Various prior arts disclose the process for preparation of sumatriptan and its salts, however, the processes used in prior arts differ from each other.

us Pat No. 5,037,845 filed on August 01, 1985, was granted on August 06, 1991 and
assigned to Glaxo Group Limited. In this patent, process for the preparation of
Sumatriptan Succinate is disclosed, wherein 4,4-dimethylbutanamine is reacted with 4-
hydrazino-N-methylbenzenemethane sulfonamide hydrochloride followed by work up to
give 4- [2- [4-(dimethy lamino)butylidene]hydrazine] -N-methylbenzenemethane
sulphonamide, which is subjected to cyclization reaction in the presence of polyphosphate ester in chloroform. Reaction mass is concentrated and purified by column chromatography to give Sumatriptan base, which is treated with succinic acid in industrial methylated spirit (IMS) to give Sumatriptan Succinate.
US publication no. 2007/0054953 discloses process for the preparation of sumatriptan base and sumatriptan succinate. The crude sumatriptan is dissolved in acetone at reflux temperature, treated with carbon and filtered to give pure sumatriptan base. It is further reacted with different acids such as citric acid, ascorbic acid and oxalic acid to give corresponding sumatriptan acid addition salts. The sumatriptan acid addition salts so obtained are set free by treating with sodium or potassium carbonate and subjected to crystallization to give pure sumatriptan base. Pure sumatriptan base is further converted to pure simiatriptan succinate by conventional method.
The processes disclosed above according to cited prior arts are cumbersome and involve number of purification steps and require different solvents which results in loss of yield at each purification step, thereby making the process uneconomical.
Therefore, there is an unmet need to develop a simple and economical process for preparing sumatriptan succinate with improved yield and quality.
Objects and Summary of the Invention In is a principal object of the present invention to provide a novel crystalline solvate of sumatriptan succinate.
It is one other object of the present invention to provide a process for the preparation of novel crystalline solvate of sumatriptan succinate.

It is yet another object of the present invention to provide an improved process for preparation of sumatriptan succinate of high purity and quality employing the novel crystalline solvate of sumatriptan succinate.
The above and other objects of the present invention are further attained and supported by the following embodiments described herein. However, the scope of the invention is not restricted to the described embodiments herein after.
In accordance with one preferred embodiment of the invention, there is provided a crystalline sumatriptan succinate ethanol solvate characterized by X-Ray powder diffraction pattern having peaks at 12.26, 15.05, 15.73, 16.45, 17.22, 19.25, 19.63, 20.49, 20.77, 21.59,22.12,23.64,29.32 ±0.2 two theta values.
In accordance with another preferred embodiment of the present invention, the crystalline sumatriptan succinate ethanol solvate contains about 3.68% of ethanol content supported by weight loss in TGA.
In accordance with yet another preferred embodiment of the present invention, the crystalline sumatriptan succinate ethanol solvate is characterized by DSC pattern having peaks at about 113.46°C and 168.2''C.
In accordance with another preferred embodiment of the present invention, there is provided a process for the preparation of novel crystalline ethanol solvate of sumatriptan succinate, wherein the process comprises of dissolving sumatriptan base in a solvent, adding succinic acid solution to obtain a mixture and recovering crystalline sumatriptan succinate ethanol solvate from the mixture, wherein said solvent is selected from ethanol or industrial methylated spirit.
In accordance with yet another preferred embodiment of the present invention, there is provided an improved process for preparation of sumatriptan succinate of high purity and quality employing crystalline ethanol solvate of sumatriptan succinate, wherein the process comprises of heating crystalline ethanol solvate of sumatriptan succinate in a solvent and isolating highly pure sumatriptan succinate, wherein said solvent is selected

from methanol, isopropyl alcohol, acetone, acetonitrile, ethyl acetate, dichloromethane, preferably methanol.
Brief Description of the Drawings Further objects of the present invention together with additional features contributing thereto and advantages accruing there from will be apparent from the following description of preferred embodiments of the invention which are shown in the accompanying drawing figures, wherein:
Figure 1 is the X-ray powder diffraction pattern of crystalline sumatriptan succinate ethanol solvate.
Figure 2 is the DSC of crystalline sumatriptan succinate ethanol solvate. Figure 3 is the TGA of crystalline sumatriptan succinate ethanol solvate.
Detailed Description of the Invention While this specification concludes with claims particularly pointing out and distinctly claiming that, which is regarded as the invention, it is anticipated that the invention can be more readily understood through reading the following detailed description of the invention and study of the included examples.
The present invention discloses a novel crystalline solvate of sumatriptan succinate, and is intended to be encompassed with in the scope of the present invention. The said solvate is characterized by X-ray powder diffraction patterns, thermo gravimetric analysis (TGA) and differential scanning calorimetric patterns (DSC).
Further, the present invention describes the process for preparing crystalline solvate of sumatriptan succinate. In addition, the present invention describes an improved process for the preparation of highly pure sumatriptan succinate from the crystalline solvate of sumatriptan succinate.
Powder X-rav Diffraction (PXRD)
Ethanol solvate of the present invention is characterized by its X-ray powder diffraction
pattern. Thus, the X-ray diffraction pattem of said ethanol solvate of the invention was

measured on PANalytical, X'Pert PRO powder diffractometer equipped with goniometer of 9/0 configuration and X'Celerator detector. The Cu-anode X-ray tube was operated at 40 KV and 30 mA. The experiments were conducted over the 20 range of 2.0°-50.0°, 0.030° step size and 50 seconds step time.
Differential Scanning Calorimetrv (DSC)
The DSC measurements were carried out on Mettler Toledo 822 Star^ and TA QIOOO of
TA instruments. The experiments were performed at a heating rate of 10.0°C/min over a
temperature range of 30° C-300° C purging with nitrogen at a flow rate of 150 ml/min
and 50ml/min. Standard aluminum crucibles covered by lids with three pin holes were
used.
Thermo gravimetric Analysis (TGA)
TGA were carried out on the instrument Mettler Toledo TGA/SDTA 851^ and TAQ 5000
of TA instruments. The experiments were performed at a heating rate of 10.0°C/min over
a temperature range of 30-300° C purging with nitrogen at a flow rate of 20ml/min and
25ml/min.
Water Content:
Water content was determined on Metrohm Karl-Fischer titrator (Model: 794 Basic Titrino) using pyridine free single solution (Merck, Mumbai) with sample mass between 450 mg and 550 mg.
Crystalline sumatriptan succinate ethanol solvate is characterized by X-ray powder diffraction pattern as shown in Figure 1 having peaks at 8.61, 12.26, 12.64, 13.30, 13.68, 13.92, 14.83, 15.05, 15.41, 15.73, 16.20, 16.45, 16.84, 17.22, 17.73, 18.09, 18.86, 19.25, 19.63, 19.89, 20.25, 20.49, 20.77, 20.96, 21.36, 21.59, 22.12, 22.45, 22.76, 23.31, 23.64, 24.69, 24.88, 25.41, 26.03, 26.92, 27.72, 28.29, 29.32, 29.67, 30.90, 31.44, 31.78 ±0.2 two theta values.
Crystalline sumatriptan succinate ethanol solvate is characterized by DSC with two endothermic peaks, first at about 113.46° C attributed to the loss of solvent and 168.21°C

corresponding to melting of the product as shown in Figure 2. Crystalline sumatriptan succinate ethanol solvate contains about 3.68% of ethanol as shown by weight loss in TGA shown in Figure 3.
The present invention also provides a process for the preparation of crystalline sumatriptan succinate ethanol solvate, wherein the process involves dissolving sumatriptan base in a solvent such as ethanol or industrial methylated spirit (IMS), by heating to 60-80° C to obtain a clear solution. Subsequently, a succinic acid solution is added to the solution of sumatriptan base at 60-80° C, the succinic acid solution being prepared by dissolving succinic acid is ethanol, followed by rapid cooling of reaction mixture to room temperature over a period of 30-45 minutes. The reaction mixture is further cooled to 0°C followed by filtration to isolate the solid. The isolated solid is washed with chilled IMS and dried to recover sumatriptan succinate ethanol solvate.
The process for preparation of pure sumatriptan succinate according to the present invention comprising heating the sumatriptan succinate ethanol solvate in a solvent, wherein the sumatriptan succinate ethanol solvate is dissolved in the solvent at 40-60° C to give a clear solution followed by filtration, optionally treating with carbon. The solid so isolated is cooled to give pure crystalline sumatriptan succinate having HPLC purity of more than 99.0%. The solvent used in the process is selected fi-om methanol, isopropyl alcohol, acetone, acetonitrile, ethyl acetate and dichloromethane. The solvent preferably used is methanol.
Crystalline sumatriptan succinate obtained above is characterized by X-ray diffraction peaks at about 12.61,15.39,15.69,16.17,16.40,18.06,18.57,19.87,20.22,20.59, 21.34, 22.05,22.73,23.29,23.69,26.93 ±0.2 two theta values .
Crystalline sumatriptan succinate is further characterized by endothermic DSC peak at about 168.80°C and TGA showing weight loss of about 0.177%.
The following non-limiting examples illustrate specific embodiments of the present invention. They are, not intended to be limiting the scope of present invention in any way.

Example-1
Preparation of sumatriptan succinate ethanol solvate
Sumatriptan base (lOOgm) was dissolved in 95% ethanol (1900ml) at 70-75° C. The resultant mixture was stirred for 10-15 min at 70-75° C to obtain a solution. An acid solution was prepared in a separate flask by dissolving succinic acid in 95% ethanol at 70-75°C. The acid solution was slowly added to the sumatriptan base solution at 70-75°C. Reaction mixture was rapidly cooled to room temperature over a period of 30 minutes and further to 0°C followed by filtration to isolate the solid. The resultant solid was washed with chilled 95% ethanol, unloaded and dried to yield sumatriptan succinate ethanol solvate.
Example-2
Preparation of sumatriptan succinate
Sumatriptan succinate ethanol solvate obtained in Example-1 was dissolved in methanol (1300ml) at 65° C to obtain a clear solution. The clear solution was treated with activated carbon (5gm) and filtered over hyflo. Filtrate was cooled to room temperature and further to 0-5° C. Solid was filtered and washed with chilled methanol (100ml) followed by drying under reduced pressure to yield sumatriptan succinate.
Certain modifications and improvements of the disclosed invention will occur to those skilled in the art without departing from the scope of invention, which is limited only by the appended claims.

We Claim:
1. A crystalline sumatriptan succinate ethanol solvate, wherein said ethanol solvate is characterized by an X-ray powder diffraction pattern having peaks at 12.26, 15.05, 15.73, 16.45, 17.22, 19.25, 19.63, 20.49, 20.77, 21.59, 22.12, 23.64, 29.32 ±0.2 29".
2. The crystalline sumatriptan succinate ethanol solvate according to claim 1, wherein said ethanol solvate is characterized by an X-ray powder diffraction pattern having peaks at 8.61,12.26,12.64,13.30, 13.68,13.92,14.83,15.05,15.41,15.73, 16.20, 16.45, 16.84, 17.22, 17.73, 18.09, 18.86, 19.25, 19.63, 19.89, 20.25, 20.49, 20.77, 20.96, 21.36, 21.59, 22.12, 22.45, 22.76, 23.31, 23.64, 24.69, 24.88, 25.41, 26.03, 26.92, 27.72, 28.29,29.32,29.67, 30.90, 31.44, 31.78 ±0.2 2θ°.
3. The crystalline sumatriptan succinate ethanol solvate according to claim 1, wherein said ethanol solvate is having a substantially similar X-ray powder diffraction pattern as shown in Figure 1.
4. The crystalline sumatriptan succinate ethanol solvate according to claim 1, wherein said ethanol solvate is characterized by differential scanning calorimetry (DSC) as shown in Figure 2.
5. The crystalline sumatriptan succinate ethanol solvate according to claim 4, wherein differential scanning calorimetry (DSC) has characteristic peaks at about 113.46°C and 168.2° C.
6. The crystalline sumatriptan succinate ethanol solvate according to claim 1, wherein said ethanol solvate is characterized by a thermal gravimetric analysis (TGA) as shown in Figure 3.
7. The crystalline sumatriptan succinate ethanol solvate according to claim 6, wherein the thermal gravimetric analysis (TGA) shows weight loss of about 3.68%.
8. A process for preparing of crystalline sumatriptan succinate ethanol solvate comprising the steps of:

a) dissolving sumatriptan base in a solvent;
b) adding succinic acid to obtain a mixture; and
c) recovering the crystalline sumatriptan succinate ethanol solvate from
the mixture.
9. The process according to claim 8, wherein the solvent is selected from
ethanol or industrial methylated sprit (IMS).
10. The process according to claim 8, wherein the succinic acid is added in a solution form comprising succinic acid in ethanol.
11. A process for preparing sumatriptan succinate, the process comprising the steps of:

a) heating sumatriptan succinate ethanol solvate in a solvent; and
b) isolating pure sumatriptan succinate.
12. The process according to claim 11, wherein the solvent is selected from a
group comprising methanol, isopropyl alcohol, acetone, acetonitrile, ethyl acetate or
dichloromethane preferably methanol.