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ERREGIERRE S.P.A. [IT/IT]; Via Francesco Baracca, 19 I-24060 San Paolo D’argon (IT)

Erregierre SpA



A novel process is described for the production of Dabigatran etexilate mesylate, a 5 compound having the following structural formula: and two novel intermediates of said process.


Dabigatran etexilate mesylate is an active substance developed by Boehringer

Ingelheim and marketed under the name Pradaxa® in the form of tablets for oral administration; Dabigatran etexilate mesylate acts as direct inhibitor of thrombin (Factor I la) and is used as an anticoagulant, for example, for preventing strokes in patients with atrial fibrillation or blood clots in the veins (deep vein thrombosis) that could form following surgery.

Dabigatran etexilate mesylate is the INN name of the compound 3-({2-[(4-{Amino-[(E)-hexyloxycarbonylimino]-methyl}-phenylamino)-methyl]-1 -methyl-1 H-benzimidazol-5-carbonyl}-pyridin-2-yl-amino)-ethyl propanoate methanesulphonate, having the following structural formula:

The family of compounds to which Dabigatran etexilate belongs was described for the first time in patent US 6,087,380, which also reports possible synthesis pathways.

The preparation of polymorphs of Dabigatran etexilate or Dabigatran etexilate mesylate is described in patent applications US 2006/0276513 A1 , WO 2012/027543 A1 , WO 2008/059029 A2, WO 2013/124385 A2, WO 2013/124749 A1 , WO 2013/1 1 1 163 A2 and WO 2013/144903 A1 , while patent applications WO 2012/044595 A1 , US 2006/0247278 A1 , US 2009/0042948 A2, US 2010/0087488 A1 and WO 2012/077136 A2 describe salts of these compounds.

One of the objects of the invention is to provide an alternative process for the preparation of Dabigatran etexilate mesylate and two novel intermediates of the process.

These objects are achieved with the present invention, which, in a first aspect thereof, relates to a process for the production of Dabigatran etexilate mesylate, comprising the following steps:

a) reacting 4-methylamino-3-nitrobenzoic acid (I) with thionyl chloride to give 4- methylamino-3-nitrobenzoyl chloride hydrochloride (II):

(I) (ID

b) reacting compound (II) with 3-(2-pyridylamino) ethyl propanoate (III) to give the compound 3-[(4-methylamino-3-nitro-benzoyl)-pyridyn-2-yl-amino]-ethyl propanoate (IV):

(II) (IV)

reducing compound (IV) with hydrogen to 3-[(3-amino-4-methyl benzoyl)-pyridin-2-yl-amino]ethyl propanoate (V):

(IV) (V)

d) reacting N-(4-cyanophenyl)glycine (VI) with 1 ,1 -carbonyldiimidazole (CDI) to give 4-(2-imidazol-1 -yl-2-oxo-ethylamino)-benzonitrile (VII):

(VI) (VII)

e) reacting compound (VII) with compound (V) obtained in step c) to give one of compounds 3-({3-[2-(4-cyano-phenylamino)-acetylamino]-4-methylamino- benzoyl}-pyridin-2-yl-amino)-ethyl propanoate (VIII) and 3-[(3-amino-4-{[(2- (4-cyano-phenylamino)-acetyl]-methylamino}-benzoyl)-pyridin-2-yl- amino]ethyl propanoate (IX), or a mixture of the two compounds (VIII) and (IX):

f) transforming, through treatment with acetic acid, compounds (VIII) or (IX) or the mixture thereof into the compound 3-({2-[(4-cyano-phenylamino)-methyl]- 1 -methyl-1 H-benzimidazol-5-carbonyl}-pyridin-2-yl-amino)-ethyl propanoate (X), and then treating compound (X) with hydrochloric or nitric acid to form the corresponding salt (XI):


[(VIII) ; (IX)]

wherein A is a chlorine or nitrate anion;

liberating in solution compound (X) from salt (XI), and reacting compound (X) in solution with ethyl alcohol in the presence of hydrochloric acid and 2,2,2-trifluoroethanol to give the compound 3-({2-[(4-ethoxycarbonimidoyl-phenylamino)-methyl]-1 -methyl-1 H-benzimidazol-5-carbonyl}-pyridin-2-yl-amino)-ethyl propanoate hydrochloride (XII):

reacting compound (XII) with ammonium carbonate to form compound Dabigatran ethyl ester (XIII):

reacting compound (XIII) with maleic acid to produce the maleate salt thereof (XI 11 ‘) and isolating the latter:

j) reacting maleate salt (XI 11 ‘) with hexyl chloroformate to give compound Dabigatran etexilate (XIV :

hexyl chloroformate

k) reacting compound (XIV) with methanesulfonic acid to give the salt Dabigatran etexilate mesylate:

a gatran etex ate mesy ate


Preparation of Dabigatran etexilate mesylate (step k).

All the Dabigatran etexilate obtained in Example 1 1 (4.7 kg; 7.49 moles) is loaded into a reactor along with 28.2 kg of acetone and the mass is heated at 50-60 °C until a complete solution is obtained; it is then filtered to remove suspended impurities. The filtered solution is brought to 28-32 °C. Separately, a second solution is prepared by dissolving 0.705 kg (7.34 moles) of methanesulfonic acid in 4.7 kg of acetone; the second solution is cooled down to 0-10 °C. The second solution is poured into the Dabigatran etexilate solution during 30 minutes, while maintaining the temperature of the resulting solution at 28-32 °C with cooling. The salt of the title is formed. The mass is maintained at 28-32 °C for 2 hours, then cooled to 18-23 °C to complete precipitation and the system is maintained at this temperature for 2 hours; lastly, centrifugation takes place, washing the precipitate with 5 kg of acetone. The precipitate is dried at 60 °C.

4.88 kg of Dabigatran etexilate mesylate, equal to 6.74 moles of compound, are obtained, with a yield in this step of 90%.


0.5 g of the crystalline compound (XIV) obtained in Example 1 1 are ground thoroughly and loaded into the sample holder of a Rigaku Miniflex diffractometer with copper anode.

The diffractogram shown in Figure 1 is obtained; a comparison with the XRPD data of the known Dabigatran etexilate polymorphs allows to verify that the polymorph of Example 1 1 is novel.


0.7 g of the crystalline compound (XIV) obtained in Example 1 1 are loaded into

the sample holder of a Perkin-Elmer DSC 6 calorimeter, performing a scan from ambient T to 350 °C at a rate of 10 °C/min in nitrogen atmosphere. The graph of the test is shown in Figure 2, and shows three endothermic phenomena with peaks at 83.0-85.0 °C, 104.0-104.2 °C and 129.9 °C; events linked to the thermal decomposition of the compound are evident at about 200 °C.

Figure 1 is an XRPD spectrum of the novel polymorph of Dabigatran etexilate of the invention;

Figure 2 is the graph of a DSC test on the novel polymorph of Dabigatran etexilate of the invention.


Dabigatran etexilate mesylate 872728-81-9

1h nmr.



Reference examples:

Preparation of starting material: Dabigatran etexilate mesylate form I according to US 2005/0234104 example 1:

Ethyl 3 – [(2- { [4-(hexyloxycarbonylarninoimmomemyl)phenylammo]methyl } –

1 – methyl- lH-benzimidazole-5-carbonyl)pyridm-2-ylamino]propionate base (52.6 kg) (which has preferably been purified beforehand by recrystallization from ethyl acetate) is placed in an agitator apparatus which has been rendered inert and then 293 kg of acetone is added. The contents of the apparatus are heated to 40° C to 46° C with stirring. After a clear solution has formed, the contents of the apparatus is filtered into a second agitator apparatus through a lens filter and then cooled to 30° C to 36° C. 33 kg of acetone precooled to 0° C to 5° C, 7.9 kg of 99.5% methanesulfonic acid, and for rinsing another 9 kg of acetone are placed in the suspended container of the second apparatus. The contents of the suspended container are added in metered amounts to the solution of ethyl 3-[(2-{[4-(hexyloxycarbonylamino- iminomethyl)phenylamino]methyl} – 1 -methyl- 1 H-benzimidazole-5-carbonyl)pyridin-

2- ylamino]propionate base at 26° C to 36° C within 15 to 40 minutes. Then the mixture is stirred for 40 to 60 minutes at 26° C to 33° C. It is then cooled to 17° C to 23° C and stirred for a further 40 to 80 minutes. The crystal suspension is filtered through a filter dryer and washed with a total of 270 L of acetone. The product is dried in vacuum at a maximum of 50° C for at least 4 hours. Yield: 54.5-59.4 kg;

90%-98% of theory based on ethyl 3-[(2-{[4-(hexyloxycarbonyl- ammoiminomethyl)phenylamino]methyl} – 1 -methyl- 1 H-benzimidazole-5-carbonyl)- pyridm-2-ylamino]propionate base.

Preparation of starting material: Dabigatran Etexilate free base

Dabigatran Etexilate free base can be prepared according to the procedures disclosed in US 6087380 – example 113 or US 7202368 – example 5 Example 1

2.08 g of dabigatran etexilate free base was dissolved in 14.7 ml of acetone at 30 – 36 °C. 0.210 ml of methanesulfonic acid diluted in 2.20 ml of acetone was added within 15 – 40 min. at 26 – 36 °C. The resulting mixture was first steered for 40 – 60 min. at 26 – 36 °C and then for 40 – 80 min at 17 – 23 °C.

The resulting crystalline product was filtered off, washed with 17.87 ml of acetone and dried at 50 °C for 18 hours at 540 mbar.



Chinese Journal of Applied Chemistry
Synthesis of Dabigatran Etexilate
LIU Xiaojun, CHEN Guohua*
(Department of Medicinal Chemistry,China Pharmaceutical University,Nanjing 210009,China)

4-Methylamino-3-nitrobenzoic acid(3) was prepared from 3-nitro-4-chlorobenzoic acid by methylamination. 3-[(Pyridin-2-yl)amino]propinoic acid ethyl ester(5) was prepared from 2-aminopyridine and ethyl acrylate by Michael addition. Dabigatran etexilate was synthesized from compounds 3 and 5 via condensation, catalytic hydrogenation, acylation with N-(4-cyanophenyl)glycine(9), cyclization, Pinner reaction, followed by reaction with n-hexyl chlorofomate. The overall yield is about 40% and the structure of the product was determined by IR, 1H NMR and MS.

ESIMS(m/z):628[M+H]+;1 HNMR(500MHz,DMSOd6), δ:091(t,3H,J=90Hz,CH3),116(t,3H,J=85Hz,CH3),125~169(m,8H,4×CH2),274(t, 2H,J=145Hz,CH2CO),379(s,3H,CH3N),395~403(m,4H,2CH2O),428(t,2H,J=140Hz, CH2),451(d,2H,J=55Hz,CH2N),676(d,J=85Hz,2H,Ar—H),688(d,J=75Hz,1H,Ar— H), 702(s,1H,N—H),713~721(m,2H,Py—H),740(d,J=85Hz,1H,Ar—H),747(d,J=15Hz, 1H,Ar—H),755~759(m,1H,Py—H),786(d,J=85Hz,2H,Ar—H),836~843(m,1H,Py—H), 902(brs,2H,NH2);IR(KBr),σ/cm-1 :3374,2953,2929,1730,1640,1610,1470,1389,1326,1256,1192, 1145,1127,1021,945,835,811,768,747。

Synthesis of Dabigatran Etexilate.pdf





Identification, Synthesis, and Strategy for the Reduction of Potential Impurities Observed in Dabigatran Etexilate Mesylate Processes

Novel Technology Center of Pharmaceutical Chemistry, Shanghai Institute of Pharmaceutical Industry, 1111 North Zhongshan No. 1 Road, Shanghai 200437, P. R. China
Department of Pharmacy, Shandong Provincial Hospital affiliated to Shandong University, Jinan 250021,P. R. China
Org. Process Res. Dev., 2014, 18 (6), pp 744–750
DOI: 10.1021/op500084q
Abstract Image

Synthetic impurities that are present in dabigatran etexilate mesylate were studied, and possible pathways by which these impurities are formed during the manufacturing process were examined. The impurities were monitored by high-performance liquid chromatography, and their structures were determined by mass spectrometry and 1H and 13C NMR. Potential causes for the formation of these impurities are discussed, and strategies to minimize their formation are also described.




Dabigatran etexilate 211915-06-9 H-NMR

Dabigatran etexilate 211915-06-9C-NMR S


WO2015044375A1 * Sep 26, 2014 Apr 2, 2015 Ratiopharm Gmbh Pharmaceutical preparation comprising dabigatran etexilate bismesylate

See full gatran series at………………




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DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 29 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international, etc in organic chemistry are some most read blogs He has hands on experience in initiation and developing novel routes for drug molecules and implementation them on commercial scale over a 29 year tenure till date Aug 2016, Around 30 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 25 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 13 lakh plus views on New Drug Approvals Blog in 212 countries...... , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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