FORM 2
THE PATENT ACT 1970
(39 of 1970)
AND
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"PROCESS FOR PREPARATION OF PIPECURONIUM BROMIDE"

2. APPLICANT
(a) NAME: MAC CHEM PRODUCTS INDIA PVT. LTD.
(b) NATIONALITY: Indian Company incorporated under the Indian Companies
ACT, 1956
(c) ADDRESS: 304, Town Centre, Andheri-kurla Road, Andheri (E),
Mumbai-400059, Maharashtra, India.
3.PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed

Technical field:
This invention relates to an improved process for the synthesis of pure Pipecuronium
bromide [2p,16(3-bis-(4',4'-dimethyIpiperazino)-3a,17p-diacetoxy-5a-androstane
dibromide].
Background and prior art:
Neuromuscular blockers (NMB) are one of the three classes of drugs used widely during surgical anesthesia. All currently act by blocking the pharmacological effects of acetylcholine CH3C02CH2CH2N+Me3 at membrane bound ligand - gated nicotinic acetylcholine receptors on skeletal muscle.
Two classes of clinically used NMB drugs can be distinguished based upon their mechanisms of action, the depolarizing agents, e.g. suxamethonium and non-depolarizing agents e.g. Pancuronium, Pipecuronium, Vecuronium, Rocuronium and Atracurium.
Pipecuronium bromide is presently marketed under brand name Arduan ®. The steroidal skeleton is as shown herein below.

PIPECURONIUM BROMIDE
Pipecuronium bromide [2f3,16j3-bis-(4',4'-dimethylpiperazino)-3a,17p-diacetoxy-5a -androstane dibromide. CAS Number : 52212-02-9] is a steroidal neuromuscular blocking agent, resembling Pancuronium bromide not only in its chemical structure (Figure-I), but also in the potency and time-course of its neuromuscular blocking effect.

Pipecuronium bromide has been disclosed for the first time in DE Patent No. 2337882. According to said patent, method of producing Pipecuronium bromide involves the reaction of 2p,16p-bis-(4-methyl-l-piprazinyl)-3a,17f3-diacetoxy-5a-androstane, compound of formula (1)


H,C

(1)
with methyl bromide in a pressure tube for two days. The major drawbacks of this process are requirement of pressure reaction and the long reaction time. This process is complicated and time-consuming process and therefore inconvenient for large scale production.
Thus, there is a need to develop a process for preparation and purification of Pipecuronium bromide, using simple reaction conditions and technique, which will be suitable for industrial production.

Objects of the invention:
The object of the present invention is to provide an improved, industrially viable and cost effective process for the preparation of pure Pipecuronium bromide, substantially free of residual organic solvents and other impurities, in shorter time, avoiding use of pressure reaction.
Further object of the invention is to provide a process for the preparation of stable solid form of pure Pipecuronium bromide useful for pharmaceutical formulations.
These objects and features of the present invention are described below in more details.
Summary of the invention:
The present invention discloses an improved process for the synthesis of pure Pipecuronium bromide involving dissolution of 2p,l6p-bis-(4-methyl-l-piprazinyl)-3a,17p-diacetoxy-5tx-androstane of formula (1) in an organic solvent at ambient temperature, followed by passing methyl bromide gas into the solution to get crude Pipecuronium bromide. The dissolution of the crude product in suitable solvent followed by precipitation with a solvent having poor solubility for the product gave pure Pipecuronium bromide.
Detailed description of invention:
The process for synthesis of Pipecuronium bromide described in this invention can be classified into the following steps;
a. dissolving the compound of formula (1) in an organic solvent selected from
a group comprising of acetone, dichloromethane, acetonitrile, N-N-dimethjyformamide, tetrahydrofuran and mixture thereof; preferably acetonitrile;

b. passing methyl bromide gas into the solution of [step (a)] at room
temperature for the time period ranging from 2 hours to 10 hours, more
preferably 3 hours;
c. evaporating the solvent from step (b) under vacuum and at room
temperature;
d. adding suitable solvent to the mass from step (c) to precipitate crude
Pipecuronium Bromide. Suitable solvent include without limitation diethyl
ether, diisopropyl ether, petroleum ether, n-hexane.
e. isolating resulting solid under Nitrogen atmosphere.
f. dissolving the obtained solid from step (e) in suitable organic solvent
selected from a group comprising of acetone, dichloromethane, acetonitrile;
preferably acetonitrile, in 1 volume to 10 volumes, preferably 3 to 7
volumes; more preferably 4 to 6 volumes; most preferably in 5 volumes,
relative to quantity of crude product obtained in step (e);
g. pouring the reaction mass of step (f) in suitable solvent to obtain pure
Pipecuronium Bromide. Here, suitable solvent imply without limitation
solvents like ethyl acetate, diethyl ether and petroleum ether.
h. isolating the solid from step (g) under Nitrogen atmosphere.
i. drying the solid from step (h) at 40° under vacuum for time period of 10
hours to 20 hours, preferably 12 hours.

Pipecuronium bromide obtained in accordance with present invention has a Potentiometric assay of greater then 98%. The purity of the obtained product was ascertained by its TLC (method described).
TLC Method:
Test solution was prepared by dissolving 0.2 gm of Pipecuronium Bromide in 10 ml methanol. Reference solution was prepared by diluting 0.2 ml of test solution to 10 ml with methanol. Stationary phase was Silica plate GF254. Mobile phase was prepared by mixing 8.5 volumes of isopropyl alcohol, 1.0 volume of Acetonitrile and 0.5 volume of sodium Iodide (20% w/v). 5ul of each test solution and reference solution were spotted on stationary phase. Plate was developed in saturated chamber and then dried in air for 15 mins. Plate was detected in iodine chamber.
Stability study was performed on pure Pipecuronium bromide. The study showed that the Pipecuronium bromide prepared in accordance with the present invention is stable as illustrated in Table 1, wherein there was no increase in the level of impurities after stability study. The product was found to be physically and chemically stable at ambient temperature.
The following examples illustrate embodiments of the present invention and are not limiting to the specification and the claims in anyway.
Examples:
Example 1
Methyl bromide gas was passed through a stirred solution of compound of formula (1) (25gm) in 250 ml acetonitrile at room temperature till completion of reaction, preferably for 3 hours at room temperature. The solvent was distilled off completely under vacuum and 200 ml of diethyl ether was added. Reaction mass was stirred at room temperature for 30 mins. The obtained solid was filtered under Nitrogen atmosphere and washed with ether. Yield = 27gm.

Example 2
Methyl bromide gas was passed through a stirred solution of compound of formula (1) (20gm) 200 ml of dichloromethane at room temperature preferably for 8 to 10 hours. Sticky mass was observed and solvent was evaporated completely under vacuum. 200 ml of Diethyl ether was added and reaction mass was stirred at room temperature for 30 mins. The obtained solid was filtered under Nitrogen atmosphere and washed with ether. Yield = 17gm
Example 3 Purification:
Crude [prepared as in example 1 & 2] (25gm) was taken in acetonitrile (125 ml) and stirred to dissolve at room temperature. The reaction mass was quenched in 1250 ml of ethyl acetate at room temperature slowly. The solid was stirred at room temperature for 30 mins. Then the reaction mass was filtered under Nitrogen atmosphere and washed with ethyl acetate. The obtained solid was dried at 40° under vacuum for 12 hours.

Yield - 22.5 gm
Colour = White solid
Potentiometric Assay = > 98%
Melting Point = 268 - 269°
Optical Rotation [a] D25 = + 8.1 (c=l in water)
Moisture content = <8%
Bromide content = 20.85 (Theory = 20.95)
OVI (organic volatile impurities)
Ethylacetate = Nil
Acetonitrile = 0.002 %

STABILITY DATA
Table 1

Batch No. Result

Conditions Description (White to Off-white) Water (NMT 8.0%) SOR
(+6 to+10) Related
Substance
byTLC Assay
(98% to
102%)
29 As Such White 7.80 +7.43 Complies 101.00

1M LT White 7.60 +7.08 Complies 98.95

3M LT White 7.50 +7.61 Complies 98.18

Acce. White 7.85 +7.05 Complies 98.91

6M LT White 7.45 +7.46 Complies 99.04

Acce. White 7.70 +7.59 Complies 98.88
30 As Such White 7.10 +7.63 Complies 99.5

1M LT White 7.70 +6.83 Complies 98.40

3M LT White 7.30 +7.66 Complies 98.50

Acce. White 7.81 +7.54 Complies 98.68

6M LT White 7.90 +7.45 Complies 98.33

Acce. White 7.60 +7.66 Complies 98.54
31 As Such White 4.80 +7.30 Complies 100.65

1M LT White 7.90 +7.50 Complies 98.29

3M LT White 7.35 +7.50 Complies 98.80

Acce. White 7.84 +7.72 Complies 98.36

6M LT White 7.60 +7.30 Complies 98.84

Acce. White 7.80 +7.51 Complies 98.45
LT: Long Term (30° C/65%RH) Acce.: Accelerated (40° C/75%RH)

We claim,
1. A process for preparation of Pipecuronium bromide comprises passing of methyl bromide gas through a stirred solution of compound of formula (1) in an organic solvent at ambient temperature.


N CH,

(D
2. The process as claimed in claim 1, wherein an organic solvent is selected from a group comprising of acetone, dichloromethane, acetonitrile, N-N-dimethlyformamide, tetrahydrofuran and mixture of tetrahydrofuran and dichloromethane; preferably acetonitrile.
3. The process as claimed in claim 1, wherein methyl bromide gas is passed for 2 to 10 hours; preferably 3 hours.
4. A process for purifying Pipecuronium bromide comprising dissolution of crude Pipecuronium bromide followed by its precipitation.
5. The process as claimed in claim 4, wherein solvent suitable for dissolution is selected from a group comprising of acetone, dichloromethane, acetonitrile; preferably acetonitrile.

6. The process as claimed in claim 4, wherein solvent suitable for precipitation is selected from a group comprising of diethyl ether, diisopropyl ether, petroleum ether and n- hexane; preferably ethyl acetate.
7. The process as claimed in claim 4, wherein solvent is added in 1 to 10 volumes with respect to crude product; preferably 3 to 7 volumes; more preferably 4 to 6 volumes; most preferably 5 volumes.
8. The process as claimed in claim 4, comprising Pipecuronium bromide with of residual organic solvents within acceptable limits and having purity more than or equal to 98%.
9. The process for preparation of pure Pipecuronium Bromide as claimed in preceding claims, stable for use in pharmaceutical preparation.
Dated this 4th Day of December, 2008

Dr.P.Aruna Sree Agent for the Applicant