Isolation, Synthesis And Characterization Of

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ISSN: 0973-4945; CODEN ECJHAO E-Journal of Chemistry Vol. 5, No.3, pp. 562-566, July 2008

Isolation, Synthesis and Characterization of Rosiglitazone Maleate Impurities SINGAMSETTY RADHA KRISHNA§, MANDAVA VENKATA NAGA BRAHMESHWAR RAO§, TIRMALARAJU SATYANARYANA RAJU§, VURIMIDI HIMABINDU# and GHANTA MAHESH REDDY§* §

Research and Development, Dr. Reddy’s Laboratories Ltd., Integrated Product and Development, Unit-III, Plot No. 116, S V Co-Op. Ind. Estate, Bollaram, Jinnaram, Medak Dist 502 325; A P, India # Institute of Sciences and Technology, Center for Environmental Sciences, J.N.T. University, Kukatpally, Hyderabad-500072, India Dr. Reddy’s communication No. DRL-IPDO-IPM - 00074 [email protected] Received15 November 2007; Accepted 2 January 2008 Abstract: Three unknown impurities in rosiglitazone maleate 1 bulk drug at level below 0.1% (ranging from 0.05 to 0.1%) were detected by simple reverse phase high performance liquid chromatography. These impurities were preliminarily identified with LC-MS and characterized by the mass number of the impurities. Different experiments were conducted and finally synthesized and characterized the unknown impurities. Keywords: Rosiglitazone, Drug, Impurities, Synthesis, HPLC and LC-MS

Introduction Rosiglitazone maleate 1, is an anti diabetic drug, which is a choice of non insulin dependent diabetes mellitus (NIDDM)1-5, during the process development of rosiglitazone maleate 1, three unknown impurities were identified in the analysis of different batches whose percentage area ranged from 0.05 to 0.1% by HPLC. A comprehensive study has been carried out to isolate or to prepare and characterize those impurities, due to the importance of the stringent requirement of regulatory authorities and all the impurities should be at the levels of >0.1% must identified and characterized. The present paper aims to isolate or prepare impurities and characterization.

Experimental Samples The investigated samples of Rosiglitazone maleate bulk drug material were prepared in Dr. Reddy’s Laboratories Ltd., Active Pharmaceutical Ingredient, Hyderabad, India.

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High performance liquid chromatography (HPLC) An in-house LC isocratic method was developed for the analysis of rosiglitazone maleate and its impurities, where a column (Inertsil ODS 3V, 250 x 4.6 mm, 5 µ) with a mobile phase consisting of buffer (4.14 g of sodium dihydrogen phosphate in 1000 mL of water, adjusted the pH to 6.2 with diluted sodium hydroxide), and acetonitrile in the ratio of 50:50 (v/v) with a flow rate of 1.0 mL/min, UV detection at 245 nm was used. This LC method was able to detect all these impurities.

Liquid chromatography-Mass spectrometry (LC-MS) LC-MS/MS compatible method was developed for the analysis of Rosiglitazone maleate and its impurities, where a column (Inertsil ODS 3V 250 X 4.6 X 5.0 µ) with a mobile phase consisting of 0.01M ammonium acetate (pH=6.0) adjusted with dilute acetic acid and acetonitrile in the ratio of 65:35, with a flow rate of 1.0 mL/min, UV detection at 280 nm was used. This LC method was able to detect all the impurities. The mass spectrum of impurities was recorded on AB-4000 Q-trap LC-MS/MS mass spectrometer.

Mass spectrometry The electro spray ionization and MS-MS studies were performed on AB-4000 LC-MS/MS mass spectrometer. The positive and negative electro spray MS data was obtained by switching the capillary voltage between n+5000 and -4500V respectively.

NMR spectroscopy The 1H NMR experiments of rosiglitazone maleate were done at 400 MHz and 100 MHz on Varian Mercury plus 400 MHz FT NMR Spectrometer and similar experiments for impurities 1, 2 and 3 were performed on Gemini-2000 (200 MHz) in DMSO-d6. The 1H chemical shift values were reported on the δ scale in ppm relative to TMS (δ=0.00ppm) and the chemical shift values were reported relative to CDCl3 (δ=77.00ppm) and DMSO-d6 (δ=39.50ppm) as internal standards respectively. DEPT spectra revealed the presence of methyl and methane groups as positive peaks and methylenes as negative peaks.

FT IR spectroscopy The IR spectra were recorded in the solid state as KBr dispersion medium using Perkin Elmer Spectrum One FT IR spectrophotometer.

Synthesis of impurities Synthesis of impurity 1 (desmethyl impurity) To a mixture of 2-chloropyridine, (2, 40.0 g, 0.352 mol) and 2-aminoethanol (3, 48.2 g, 0.790 mol) heated to 145-155OC and maintained for 10-12 h, the reaction was monitored by TLC, after completion of the reaction, cool to 25-35OC, added saturated sodium chloride solution (~ 98 mL), and extracted with toluene (4 x 50 mL), the combined organic layer was distilled, yielded 14 g of crude 4, proceeded to next step with out further purification. The crude compound 4 (10 g), potassium tert- butoxide (29.5 g), and DMF (30 mL) were stirred for 10 h at 25-35OC temperature, after completion of the reaction (monitored by TLC) water (500 mL) was added and stirred for 2-4 h, the obtained solid was filtered and washed with water suck dry for 1-1.5 h, the wet material was taken into the RBF, added thiazolidine-2,4dione (6, 5.5 g, 0.047 mol), benzoic acid (0.6 g), piperdine (0.5 g), toluene (82.0 mL) were heated to azotropically reflux for 4-8 h, cool to 25-35OC filtered the solid and washed with toluene, obtained compound 7, dried at 60-70OC, yield 7.0 g.

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The above compound 7(6.0 g), acetic acid and water mixture 100 mL (8:2) and wet palladium carbon (10 g) under hydrogen pressure 2.0 kg/cm in hydrogenation rector for 12 h, the reaction mass was filtered through hyflow, washed with acetic acid and pH was adjust to 6-7 with caustic lye, followed by extracted with dichloromethane (60 mL), the organic layer was distilled completely and product was isolated in isopropyl alcohol, yield 2.5 g, mass m/z 344, IR (KBr): 3333,1698, 1H NMR: 12.0(1H), 7.9-8.0(1H), 7.0-7.5(1H), 6.57.5(2H), 6.5-7.0(2H), 4.8-5.0(1H), 3.8-4.2(2H), 3.6-3.8(2H), 3.2-3.4(3H), 2.8-3.2(1H).

Synthesis of impurity 1 (dimer impurity) To a solution of 5-{4-[2-(methyl-pyridin-2-yl-amino)-ethoxy]-benzylidene}-thiazolidine2,4-dione (8, 300 g, 0.845.mol) in THF (1010 mL), cool the reaction mass to -5 to 0 °C and slowly added L-slectride (186 mL) using dropping funnel at -5 to 0 OC the reaction maintained for 40 minutes, then reaction was further cooled -10 OC and added 10% aqueous sodium hydroxide (338 mL) solution, followed by 27% hydrogen peroxide solution (84 mL) was added. The solvent was distilled below 0OC and pH was adjusted to 7 with 2M HCl solution (370 mL), the reaction mass was extracted with dichloromethane (3 x 150 mL), the separated organic layer was distilled completely, the crude was purified by column chromatography using dichloromethane and methanol as eluents, yield 4.0 g with 98% purity by HPLC, mass m/z 712, IR (KBr): 3434, 2927, 1753, 1702; 1HNMR: 7.94(1H), 7.9(1H), 7.37(1H), 6.46-7.39(4H), 3.97-4.61(2H), 3.82-3.95(4H), 2.4-3.5(2H).

Synthesis of impurity 2 (succinate impurity) A mixture of Rosiglitazone maleate (1, 10 g) and water (2 mL) were heated to 95-100OC for 120 h with out stirring, the reaction mass cooled to 25-35OC scratched 8.4 grams. Take this material and methanol (160 mL) heat to 60-65OC, stirred for 20-30 minutes and cool to 4045OC, filter the solid and dried at 50-55OC, yield 3.9 g with 99% purity by HPLC, MS : m/z 473, IR(KBr): 3547, 3422 and 1755,1715; 1HNMR: 4.97(dd,1H), 3.05(dd,1H), 3.38(m,1H), 7.15(d,1H), 6.86(d,1H), 4.11(t,2H), 3.89(t,2H), 3.06(s,3H), 8.07(d,1H), 6.56(t,1H), 7.50 (t,1H) 6.65(d,1H), 5.07(t,1H), 2.65(d,1H), 3.02(m,1H).

Figure 1. Blend chromatogram of rosiglitazone and its impurities Table 1. IR and mass spectral data of impurities 1, 2 & 3. compound IR cm-1 MS S.No. 1 Impurity 1 3434(NH), 2927(OH) protonated molecular ion 1753(C=O), 1702 (C=O) +ve ES m/z = 713 2 Impurity 2 3547(NH), 3422(OH) protonated molecular ion 1755(C=O), 1715 (C=O) +ve ES m/z = 473 3 Impurity 3 3333(NH), 1698(OH) protonated molecular ion 1753(C=O), 1702 (C=O) +ve ES m/z = 344

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Table 2. 1H NMR spectral date of impurities 1,2&3 Impurity 1 Impurity 2 Impurity 3 S.No. H ppm H ppm H ppm 1 1H 7.94 1H 4.97 2H 11.0 2 1H 7.90 1H 3.05 1H 7.9 3 1H 7.37 1H 3.38 1H 7.0 4 4H 6.46 1H 7.15 4H 6.5 5 2H 3.97 1H 6.86 1H 4.8 6 4H 3.82 2H 4.11 2H 3.8 7 2H 2.4 2H 3.89 2H 3.6 8 3H 3.06 3H 3.2 9 1H 6.56 1H 2.8 10 1H 5.07 11 1H 2.65 12 1H 3.02

Results and Discussion In our approach based on the mass information from LC-MS we have proposed structures and synthetic schemes (1-3) for the impurities. We have also designed different experiment and synthesized these compounds and characterized. The isolated compounds RRT’s are matching with of unknown impurities. The same impurities were enriched from the filtrates of the isolated compounds, by keeping compound stability at variable temperatures.

Synthesis of rosiglitazone impurities

N 2

F

OH Toluene

+ H2N Cl

N 4

3

OH

N

CHO DMF/ t BuOK

N

N

H

H

O

CHO

5 O NH S

O N

N H

O

6 NH

S Impurity 1

O

O

Pd/C, AcOH N

O

O

N

NH 7

H

S

O

(Desmethyl Rosiglitazone)

Scheme 1 H N

O O N

NH L-slectride

O

N

S

CH3

N

N

O

O

N

S

CH3

O

O

O

N H

8

O Impurity 2 (Dimer impurity)

Scheme 2

H3C

S

N

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G. MAHESH REDDY et al. O

N

N

O

CH3

O NH .

S

O

COOH

water

COOH

N

N CH3

O

N S

COOH

O COOH

Impurity 3 (succinate impurity)

Rosiglitazone Maleate (1)

Scheme 3

Conclusion The results from various physio-chemical techniques confirm the structures of three impurities of Rosiglitazone maleate 1. Based on the through analytical and the sequence of preparations, the structures of three impurities were established with well characterization.

Acknowledgement We thank the management of Dr. Reddy’s laboratories Ltd. for supporting this work. Cooperation extended by all college of Analytical Research and Development division is gratefully acknowledged.

References 1. 2. 3. 4. 5.

Barrie C C C, Michael A C, Grahem P C, Peter T D, David H, Richard M H., Carolyn A L, Stephen A S and Peter L H, J. Med. Chem. 1994, 37, 3977. DeFronzo R A, Ferrannini E and Koivisto V, Am. J. Med 1983, 17, 74(1A) 52. Meguro K and Fujita T, US 4687777, 1987; Chem. Abstr. 1986,105:226543. Momose Y, Meguro K, Ikeda H, Hatanaka C, Oi S and Sohda T, Chem. Pharm Bull. 1991, 39(6), 1440. Barrie C C C, Drake S E, David H, Curtis H R, Catherine M H, Richard M H, Keith R J, John T S and Stefan R W, J. Chem. Soc., Perkin Trans-1, 1994, 3319.