TRANDOLAPRIL SPECTRAL DATA

TRANDOLAPRIL

(2S,3aR,7aS)-1-[(2S)-2-{[(2S)-1-ethoxy-1-oxo-4-phenylbutan-2-yl]amino}propanoyl]-octahydro-1H-indole-2-carboxylic acid

87679-37-6  CAS NO

C24-H34-N2-O5, 430.549

Indications. hypertention

Abbott..(opten , godrik, mavik), HOECHST MARION ROUSSEL..Odrik,

RU-44570, Preran,

Aventis Pharma (Originator), Nippon Roussel (Originator), Abbott (Licensee), Chugai (Licensee)Launched-1993

Trandolapril is a non-sulhydryl prodrug that belongs to the angiotensin-converting enzyme (ACE) inhibitor class of medications. It is metabolized to its biologically active diacid form, trandolaprilat, in the liver. Trandolaprilat inhibits ACE, the enzyme responsible for the conversion of angiotensin I (ATI) to angiotensin II (ATII). ATII regulates blood pressure and is a key component of the renin-angiotensin-aldosterone system (RAAS). Trandolapril may be used to treat mild to moderate hypertension, to improve survival following myocardial infarction in clinically stable patients with left ventricular dysfunction, as an adjunct treatment for congestive heart failure, and to slow the rate of progression of renal disease in hypertensive individuals with diabetes mellitus and microalbuminuria or overt nephropathy.

Trandolapril is an ACE inhibitor used to treat high blood pressure, it may also be used to treat other conditions. It is marketed by Abbott Laboratories with the brand name Mavik.

Tarka is the brand name of an oral antihypertensive medication that combines a slow release formulation of verapamil hydrochloride, acalcium channel blocker, and an immediate release formulation of trandolapril, an ACE inhibtor. The patent, held by Abbott Laboratories, expires on February 24, 2015.

This combination medication contains angiotensin-converting enzyme (ACE) inhibitor and calcium channel blocker, prescribed for high blood pressure.

Trandolapril is a prodrug that is deesterified to trandolaprilat. It is believed to exert its antihypertensive effect through the renin-angiotensin-aldosterone system. Trandolapril has a half life of about 6 hours, and trandolaprilat has a half life of about 10. Trandolaprilat has about 8 times the activity of its parent drug. Approximately 1/3 of Trandolapril and its metabolites are excreted in the urine, and about 2/3 of trandolapril and its metabolites are excreted in the feces. Serum protein binding of trandolapril is about 80%.

Trandolapril is a drug that is used to lower blood pressure. Blood pressure is dependent on the degree of constriction (narrowing) of the arteries and veins. The narrower the arteries and veins, the higher the blood pressure. Angiotensin Il is a chemical substance made in the body that causes the muscles in the walls of arteries and veins to contract, narrowing the arteries and veins and thereby elevating blood pressure. Angiotensin Il is formed by an enzyme called angiotensin converting enzyme (ACE). Trandolapril is an inhibitor of ACE and blocks the formation of angiotensin Il thereby lowering blood pressure. The drop in blood pressure also means that the heart does not have to work as hard because the pressure it must pump blood against is less. The efficiency of a failing heart improves, and the output of blood from the heart increases. Thus, ACE inhibitors such as trandolapril are useful in treating heart failure.

Trandolapril's ACE-inhibiting activity is primarily due to its diacid metabolite, trandolaprilat, which is approximately eight times more active as an inhibitor of ACE activity.

........................

synthesis

(3aR,7aS)-octahydroindole-2(S)-carboxylic acid (I) goes through the process of esterification with benzyl alcohol (II) in the presence of SOCl₂ to produce the corresponding benzyl ester (III), and the yielding compound is then condensed with N-[1(S)-(ethoxycarbonyl)-3-phenylpropyl]-(S)-alanine (IV) in the presence of 1-hydroxybenzotriazole, N-ethylmorpholine and dicyclohexylcarbodiimide (DCC) in DMF to afford the benzyl ester (V) of the desired product. Lastly, the compound is debenzylated by hydrogenation with H₂ over Pd/C in ethanol.

.....................................................

Trandolapril along with other related compounds was first disclosed in US4933361. The process for the synthesis of trandolapril was described in US4933361 and WO9633984.

US4933361 describes a process for the synthesis of trandolapril wherein the racemic benzyl ester of octahydro indole-2-carboxylic acid is reacted with N-[1-(S)-ethoxy carbonyl- 3- phenyl propyl]-L-alanine (ECPPA), to get racemic benzyl trandolapril, which is purified using column chromatography to get the 2S isomer of benzyl trandolapril, which is further debenzylated with Pd on carbon to get trandolapril as a foamy solid. This process has certain disadvantages, for example the product is obtained in very low yield. Purification is done using column chromatography, which is not suitable for industrial scale up.

WO9633984 discloses a process in which N-[1-(S)-ethoxy carbonyl-3- phenyl propyl]-L- alanine is activated with N-chlorosulfinyl imidazole, to get (N-[I-(S) N-[1-(S)-ethoxy carbonyl-3-phenyl propylj-L-alanyl-N-sulfonyl anhydride and which is further reacted with silyl-protected 2S,3aR,7aS octahydro indole 2-carboxyIic acid to obtain trandolapril. The main disadvantages of this process are that the silyl-protected intermediates are very sensitive to moisture, the process requires anhydrous conditions to be maintained and the solvent used has to be completely dried. It is very difficult to maintain such conditions on an industrial scale, and failing to do so leads to low yield of product.

The processes for preparing N-[1-(S)-ethoxy carbonyl-3-phenyl propyl]-L-alanine N- carboxyanhydride which is used in the process of the present invention are well known and are disclosed in JP57175152A, US4496541 , EP215335, US5359086 and EP1197490B1. Trans octahydro-IH-indole-2-carboxylic acid and its esters are the key intermediates in the synthesis of trandolapril. When synthesized, trans octahydro-1 H-indole-2-carboxylic acid is a mixture of four isomers, as shown below.

From the processes known in the prior art, trans octahydro-1 H-indole-2-carboxylic acid is converted to its ester and the ester is then either reacted directly with N-[1-(S)-ethoxy carbonyl-3-phenyl propyl]-L-alanine (ECPPA) and then the isomers are separated by column chromatography, or alternatively the ester is reacted with ECPPA followed by 0 deprotection. Trans octahydro-1 H-indole-2-carboxylic acid is always used in its protected form. No attempts have been made to resolve free trans octahydro-1 H-indole-2-carboxylic acid to convert it to the desired isomer (isomer D, above). Furthermore, none of the prior art processes is stereoselective, so resolution of the required isomer is required following condensation.

EP0088341 and US4490386 describe a method for the resolution of N-benzoyl (2RS,3aR,7aS) octahydro-1 H-indole-2-carboxylic acid using α-phenyl ethyl amine.

US6559318 and EP1140826 describe a process for the synthesis of (2S,3aR,7aS) 0 octahydro-1 H-indole-2-carboxylic acid using enzymatic resolution of its nitrile intermediate. Enzymatic resolution involves many steps and also requires column chromatography for purification making the process uneconomical industrially.

WO8601803 describes the preparation of (2S,3aR,7aS) octahydro-1 H-indole-2-carboxylic 5 acid ethyl ester and benzyl ester using 10-D-camphor sulphonic acid.

WO2004065368 describes the synthesis of (2S,3aR,7aS) octahydro-1 H-indole-2- carboxylic acid benzyl ester by resolution using 10-D-camphor sulphonic acid to prepare trandolapril. This process gives poor yields because the product has to be first resolved and then the ester is deprotected leading to further loss in yield, making the process low yielding and expensive.

W 02005/051909 describes a process for the preparation of trandolapril, i.e. (N-[I-(S)- carbethoxy-3-phenylpropyl}-S-alanyl-2S,3aR,7aS-octahydroindol-2-carboxyIic acid} as well as its pharmaceutical acceptable salts, using a racemic mixture of trans octahydroindole-2- carboxylic acid with the N-carboxyanhydride of {N-[1-(S)-ethoxycarbonyl-3-phenylpropyl}- S-alanyl (NCA) in a molar ratio of 1 :1 to 1.6:1 in a mixture of water and water-miscible solvent to obtain a mixture of diastereomers of trandolapril. The diastereomers are converted to salts which upon repeated crystallization from acetone and water, and reaction with a base gives pure trandolapril. Thus, the condensation reaction in the presence of water and a water-miscible solvent is not stereoselective.

The processes for preparing N-[1-(S)-ethoxy carbonyl-3- phenyl propyl]-l_-alanine N- carboxyanhydride starting from N-[1-(S)-ethoxy carbonyl-3- phenyl propyl]-L-alanine (ECPPA) are well known and are disclosed in JP57175152A, US4496541 , EP215335, US5359086 and EP1197490B1

The angiotensin-converting enzyme (ACE) inhibitor trandolapril is commonly prescribed as a cardiovascular drug for the control and management of mild to severe hypertension Chigh blood pressure) and may be used alone or in combination with diuretics or other antihypertensive agents. Administration of trandolapril is typically oral at a level of around 0.5-4 mg once a 15 day and may also be used in the management of conditions such as heart failure and left ventricular dysfunction following myocardial infarction.

Trandolapril itself is a prodrug, being converted to the  acid form "trandolaprilat" in vivo. It is, however, • generally desirable to prepare and administer the ester form.. The structures of trandolapril and trandolaprilat ^' are shown below.

Trandolapril Trandolaprilat

Various methods for the synthesis of trandolapril and related compounds have been proposed but each of these suffers from drawbacks . Frequently the syntheses require the use of dangerous reagents, which make industrial scale preparation hazardous and difficult and/or involve multiple steps resulting in a long and complex synthesis . One of the most important steps in the synthesis is the formation of the trans-fused octahydroindole ring, which is often difficult to separate from the cis-fused equivalent.

A number of the known synthetic routes to trandolapril proceed via the key intermediate (2S, 3aR,7aS) -octahydro,-lH-indole-2-carboxylic acid. This contains the key trans-fused octahydroindole ring and the correct stereochemistry for the carboxylic acid group at the 2-position. Frequently, these methods require the separation of the cis- and trans-fused rings and, in many cases, resolution of the carboxylate group at the 2 -position is necessary. Where production of the trans-fused ring junction has been possible without generating significant quantities of the cis-product, the syntheses have been long and/or required dangerous reagents such as mercury compounds.

(2S, 3aR, 7aS)-octahydro-lH-indole-2-carboxylic acid

US-A-4691022 gives a synthesis of the above intermediate compound in relatively few steps but requires the trans-octahydroindole as the starting material. The result is also a mixture of the 2-α and 2-β compounds.

EP-A-084164/US-A-4, 933,361 provides an apparently effective method for the synthesis of the cis-fused intermediate beginning with the high-pressure hydrogenation of indole at 100 atmospheres of hydrogen and a platinum catalyst. This document also provides two methods for forming the trans-fused octahydroindole ring, but neither is indicated as being efficient. The first method provides the stereochemistry for the 2 -position from substituted alanine, reacting this with activated cyclohexanone and cyclising the product to give a hexahydroindole . Unfortunately, the reduction of this hexahydroindole to the octahydro- compound produces both cis- and trans-fused product in unknown yield. The second method is to introduce the trans-ring via trans-octahydro-lH-quinolin-2 -one, but no indication of yield in the key step is given and complex series of halogenation, partial re-hydrogenation and re-arrangement are required to reach the desired intermediate .

WO 00/40555 / US 6559318 relies on enzymic resolution of a 2- (2 ' , 2 ' -methoxyethyl) cyclohexamine with Novozyme7 over 25 hours to provide the N-acetylated (1R, 2S) enantiomer which must then be separated by column chromatography from the. unreacted (IS, 2R) enantiomer. Neither the enzymic resolution nor the chromatography steps are well suited to industrial scale preparations. There are also around ten steps required to reach the desired compound.

The synthetic route to the above octahydroindole intermediate proposed by Henning et al . (Tett. Lett. 24(1983), 5343-5346) quickly and elegantly introduces a 1,2-trans configuration around a cyclohexane ring, but requires the use of mercuric nitrate. The use of mercury compounds is obviously undesirable in the preparation of pharmaceuticals. A further synthesis is provided by Brion et al . (Tett. Lett. 33 (1992) 4889-4892) but it is unclear whether they in fact prepare 5% or 95% of the desired product with 2S stereochemistry. In any case, the method requires eleven steps including an initial pig liver esterase digestion to provide the product in stereochemically pure form but in a 95:5 mixture of isomers at position 2. This method is thus complex and ill suited to industrial scale preparation.

ROUTE A - Separation of enantiomers by the formation of diastereomeric salts with a chiral resolving agent HA* (such as 0, O' -dibenzoyl-L-tartaric acid), coupling with N- [1- (S) -ethoxycarbonyl-3-phenylpropyl] -L-alanine (ECPPA) derivative and finally deprotecting the carboxylic acid moiety R_λ (such as by hydrogenating a benzyl ester, where R_x = B_n) .

ROUTE B.- Direct reaction of 7A with ECPPA derivative that leads to the formation of diastereoisomers, deprotecting the carboxylic acid moiety and finally separation of diastereoisomers by conventional methods.

1) deprotection >■ trandolapril 2) separation of diastereoisomers

ROUTE C- Treatment of 7A in basic medium and deprotection that leads to the racemic mixture of octahydroindole acid followed by the reaction with ECPPA derivative. This will result in a diastereomeric mixture that can be separated by conventional methods.

COOEtCH,

,1 ) basic medium QC &^° ' - trandolapril 2) deprotection

2) separation of

racemic diastereoisomers 7A 6C

Route D. Separation of isomers of 6C by conventional methods (i.e. formation of a diastereomeric salt) and coupling with ECCPA derivative.

trandolapril

Route E

This route is an inversion of the steps of route B Firstly the isomers are separated and then the protecting group is removed. 1) separation of diastereoisomers trandolapπl

racemic 2) deprotection

Route F. - The compound 8A is treated to remove the protecting grqup and coupled with an ECPPA derivative,

1) deprotection

2) base treatment

racemic 7A 8A

X activating group

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US20060079698

http://www.google.com/patents/US20060079698

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INTERMEDIATE

(2S,3aR,7aS)-perhydroindole-2-carboxylic acid (42 g).

IR (Nujol, cm-1): 2923, 2854, 1600, 1458, 1377, 1319. 1H-NMR (D2O): δ 1.1-2.5 (m, 8H), 1.65(m,1H), 1.96-2.37 (m,2H), 2.91(td, 1H),4.46(d, 1H). Mass (m/z): 168.3(M-H).

http://www.faqs.org/patents/app/20110065930

(2S,3aR,7aS)-Octahydro-1H-indole-2-carboxylic acid hydrochloride

yield as a white solid.

 ¹H NMR (D₂O, 400 MHz): δ 4.42 (dd, 1H, J=11.1, 2.7 Hz), 2.93, (dt, 1H, J=11.8, 3.6 Hz), 2.36 (ddd, 1H, J=12.9, 6.7, 2.7 Hz), 2.31-2.16 (m, 1H), 2.11-2.01 (m, 2H), 1.92-1.90 (m, 1H), 1.79-1.75 (m, 1H), 1.68-1.53 (m, 2H), 1.34-1.13 (m, 3H);

LC-MS (m/z): 170.1 (M+H).sup.+. The isolated product (5) correlates to the material prepared according to U.S. Pat. No. 487,932 and Tetrahedron Lett., 1992, 33, 4889. 

(2s,3aR,7aS)-octahydro-1H-indole-2-carboxylic acid HCl

CAS No: 144540-75-0

............................................

REF

Tan, X; He, W; Liu, Y (2009). "Combination therapy with paricalcitol and trandolapril reduces renal fibrosis in obstructive nephropathy". Kidney international 76 (12): 1248–57. doi:10.1038/ki.2009.346. PMID 19759524.

 Drugs Fut1989,14,(8):778

Urbach, H., Henning, R., Teetz, V., Geiger, R., Becker, R. and Gaul, H. (Hoechst A.G.) Bicyclic amino acid derivatives.DE 3151690, EP 084164, EP 170775.JP 1989301659; JP 1989301695

• Mavik (PDF from manufacturer's website)
• Tarka (PDF from manufacturer's website)
• Trandolapril (patient information)
• Trandolapril Information - rxlist.com (Rxlist.com, The Internet Drug Index)

..................................................................................

The ESI mass spectrum of the drug trandolapril displayed a molecular ion peak [M+H] + at 431.1 amu. The tandem mass spectra (MS2) showed the fragment ions at m/z 234.2, 170.2, 160.3, 134.2, 130.3, 117.2, 102.3 and 91

The IR spectrum of new impurity showed the following absorption bands 3277cm-1 (NH stretch), 2941cm-1 (aliphatic CH stretch), 1734 and 1653cm-1 (C=O) stretch and 1192cm-1 (C-O stretch)

1H NMR

13 C NMR

TRP = TRANDOLAPRIL COMPARED WITH 2 IMPURITIES

...................................................................................................

TRANDOLAPRIL SPECTRAL DATA

http://www.google.com.br/patents/US20060079698

IR (KBr, cm-1): 3444, 3280, 2973, 2942, 2881, 1735, 1654, 1456, 1367, 1193, 1024, 699.

The 1H-NMR (CDCl3): δ 7.2 (s, 5H), 4.4(m,4H), 4.2 (q,2H), 3.6-1.3 (m, 18H), 1.28(d+t,6H). CI Mass (m/z): 429.6(M-H).

..........................................

United States Patent Application 20080171885

http://www.freepatentsonline.com/y2008/0171885.html

M.P.: 122-124° C.,

IR (KBr): 3278.7, 2942.2, 1735.2, 1654.3, 1456.7, 1433.7, 1366.5, 1192.8, 1101.5, 1063.8 and 1023.8 cm⁻¹ (FIG. 1).

¹H NMR (CD₃OD, δ ppm): 7.33 (s, 5H), 4.34 (m, 3H), 3.86 (q, 2H), 3.28-1.46 (m, 17H) and 1.39 (d+t, 6H),

Mass (m/z, amu): 453.5 (M+Na) and 431.7 (M+H)⁺ molecular ion.

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MORE INFO FOR READERS

trandolapril

• synthesis of organic compounds related to L-alanine, which are starting materials for synthesizing building blocks needed for the production of indole-like inhibitors of Angiotensin I Converting Enzyme (IACE), namely Trandolapril and its derivatives.
• [0002]
  More specifically the invention relates to a new synthesis of Trandolapril and other indole-like IACE, which are potent hypertension inhibitors.
• [0003]
  Trandolapril is a known antihypertensive agent defined as (2S, 3aR, 7aS)-1-[(1S)-1-ethoxycarbonyl)-3-phenylpropylamino-1-oxopropyl] octahydro-[1 H]-indole-2-carboxylic acid. Trandolapril has the following structural formula:

  

• The general approach in most of the Trandolapril synthesis is a peptide coupling of N-[(1-ethoxy carbonyl)-3-phenyl propyl)-S-alanine with benzyl-(2s,3aR,7aS)-octahydroindole-2-carboxylate using as coupling agent dicyclohexylcarbodiimiide in combination with 1-hydroxy benzotriazole or n-alkyl phosphonic anhydride in presence of an organic base, such as triethylamine. (2S,3aR,7aS)-octahydroindole-2-carboxylic acid is a key intermediate for the synthesis of trandolapril, which is described in the US Patent 4,525,803 .
• [0005]
  The synthesis of the key intermediate is described in the following patents or publications viz., Tetrahedron Letters, Vol. 24, (48), 5339-5345; Tetrahedron Letters, Vol. 24, (48), 5347-5350 ; US Patent 4.879.392 ; US Patent 49633361 / EP 084164 ; Tetrahedron Letters Vol. 35 (54), 4889-4892; and US Patent 6, 559, 318 .
• [0006]
  The synthesis of octahydroindole-2-carboxylic acid as described in Tetrahedron Letters, Vol. 24, (48), 5339-5345 is given in the scheme-I

  
• [0007]
  In this method, trans decahydroquinoline derivative of formula-Xlla is subject to Favorskii type ring contraction, followed by hydrolysis to give a mixture of III a and III b as a 1:1 mixture.
• [0008]
  A similar reaction with cis derivative XII b gives a mixture of IIIc and IIId as a 9:1 mixture.

  
• [0009]
  The selectivity for IIIc over IIId, when the reaction is conducted with cis lactam Xllb, is due to less thermal instability of IIIb on account of 1,3-cis interaction of a carboxyl group and a six-member ring. Such interaction, is not present in IIIa and IIIb, formed from trans lactam XIIa, hence the product is formed as a 1:1 mixture
  The scheme-II describes the methodology used in Tetrahedron Letters, Vol. 24, (48), 5347-5350 for the preparation of trans octahydroindole-2-carboxylic acid

  

  Reaction of cyclohexene with acetonitrile and mercuric acetate followed by ligand exchange with sodium chloride gives the crystalline acetamidomercury chloride in 98% yield. Reaction of the product of formula XIIIa with α-chloro acrylonitrile followed by reaction with NaBH4 and ethanol gives the product of formula XIIIb, which is cyclized with sodium in DMF to get a mixture of Xlllc and XIIId in the ratio of 18.5 : 1. On hydrolysis, IIIa is obtained selectively.
• [0010]
  Another method of preparation for octahydroindole-2-carboxylic acid is disclosed in the US Patent 4,879,392 , and is reported in scheme III

  
• [0011]
  Herein, the cyclohexane derivative of formula XIV is converted into octahydroindole-2-carbonitrile the derivative of formula XV, which is hydrolyzed to give octahydroindole-2-carboxylic acid of formula III a.
• [0012]
  Another method for the synthesis of octahydroindole-2-carboxylic acid and its subsequent conversion to trandolapril is disclosed in the US Patent 4963361 / EP 084164 and given in the scheme IV

  
• [0013]
  In this patent, methyl-β-chloro alaninate hydrochloride of formula XVI is acetylated to give a product of formula XVII, which is treated with the enamine derivative of formula XVIII to give hexahydroindoline-2-carboxylicacid of formula-IV. The product of formula IV is hydrogenated and the required enantiomer is isolated by cooling to -20°C. (2S,3aR,7aS)-Octahydroindole-2-carboxylic acid is first esterified with benzyl alcohol, coupled with ECPPA using DCC/HoBT, and finally debenzylated to yield trandolapril.
  Tetrahedron Letters Vol. 35 (54), 4889-4892 describes another methodology for the synthesis of (2S,3aR,7aS)-octahydroindole-2-carboxylic acid, which is depicted in scheme V

  
• [0014]
  Dimethyl-1,2-cyclohexane dicarboxylate of formula XX is enzymatically resolved to give the monomethyl ester of 1,2-cyclohexane dicarboxylic acid of formula XXI, which is converted into hexahydroisobenzofuranone of formula XXII. The product of formula XXII is reacted with pyrrolidine to yield a product of formula XXIII which is converted to hexahydroisobenzofuranone of formula XXII a. This product is treated with ammonia to give cyclohexane carboxamide of formula XXV. This product is subject to the Hoffmann reaction, followed by reaction with formaldehyde and potassium cyanide to give cyclohexyl amine derivative of formula XXVI. The product of formula XXVI, in reaction with methane sulphonyl chloride and benzoyl chloride give a product of formula XXVII. This product is converted into a mixture of octahydroindole-2-carbonitrile of formula XXVIII a and XXVIII b. Octahydrindole-2-carbonitrile is hydrolyzed to give octahydroindole-2-carboxylic acid of formula III a.
  The process for the synthesis of (2S,3aR,7aS)-octahydroindole-2-carboxylic acid is described in the US Patent 6,559,318 and reported in the scheme VI.

  

  In this method, cyclohexylamine derivative of formula-XXIX is resolved to produce enantiomerically pure product of formula XXX, which is converted to octahydroindole-2-carbonitrile of formula XXVIII a. The product of formula XXVIII a on hydrolysis yields the octahydroindole-2-carboxylic of formula III a.
• [0015]
  The above description gives various methods adopted to synthesize octahydroindole-2-carboxylic acid, which is the key intermediate in the preparation of trandolapril. After analyzing the different methods, it can be concluded that except the methodologies described in the US Patent 4963361 / EP 084164 , all the other methods are not suitable for industrial purpose.
• [0016]
  The method described in the US Patent 4963361 / EP 084164 has also the following drawbacks:

  • i) The synthesis of methyl -β-chloro alaninate makes use of phosphorous pentachloride, which is a corrosive reagent and difficult to handle.
  • ii) Isolation of (2S,3aR,7aS)-octahydroindole-2-carboxylic acid at -20°C is a difficult attempt during the scale up
  • iii) Use of dicyclohexylcarbodiimiide in combination with hydroxybenzotriazole makes the process costlier

IRBESARTAN SPECTRAL DATA

IRBESARTAN, SR 47436, BMS-186295

Avapro® (Bristol-Myers Squibb) and Karvea®
(Sanofi-Winthrop)

2-butyl-3-({4-[2-(2H-1,2,3,4-tetrazol-5-yl)phenyl]phenyl}methyl)-1,3-diazaspiro[4.4]non-1-en-4-one

138402-11-6  CAS NO

U.S. Patents 5,270,317 and 5,352,788, 6,162,922

The compound prepared according to US 5270317 is polymorph A

• Irbesartan is known by following chemical names:
  1. (a) 2-Butyl-3-[[2'-(1H-tetrazol-5-yl)[1,1'-biphenyl]-4-yl]methyl]-1,3-diazaspiro[4,4]non-1-en-4-one
  2. (b) 2-Butyl-3-[p-(o-1H-tetrazol-5-ylphenyl)benzyl]-1,3-diazaspiro[4,4]non-1-en-4-one
  3. (c) 2-n-butyl-4-spirocyclopentane-1-[(2'-(tetrazol-5-yl)biphenyl-4-yl) methyl]-2-imidazolin-5-one.
• 
  
  The structural formula of Irbesartan is represented below.
  

  

  Irbesartan
• 
  
  The synthesis of irbesartan is first disclosed in US5270317 (equivalentEP0454511 ) and subsequently, several other patents disclose the synthesis of irbesartan by different methods. Basically the synthesis of this molecule involves two common intermediates namely spiroimidazole and substituted 4'-bromomethylbiphenyl.
• 
  
  US 5270317 describes preparation of irbesartan wherein 1-[(2'-cyanobiphenyl-4-yl)methyl]-2-n-butyl-4-spirocyclopentane-2-imidazolin -5-one which is reacted with tributyltin azide in xylene at reflux temperature for 66 hours to give a product which is isolated from the reaction mass as trityl irbesartan and then deprotected in methanol/THF mixture using 4N hydrochloric acid to get irbesartan.
• 
  
  US5629331 describes a process for the preparation of irbesartan from 1-[(2'-cyanobiphenyl)4-yl)methyl]-2-n-butyl-4-spirocyclopentane-2-imidazolin-5-one using sodium azide, TEA.HCl in N-methylpyrrolidone. The product is isolated from the alkaline reaction mass after acidification to pH 4.7 to 5.8 and the crude product is recrystallised from IPA/water to get Form A and ethanol/water to get Form B.

Irbesartan (INN) /ɜrbəˈsɑrtən/ is an angiotensin II receptor antagonist used mainly for the treatment of hypertension. Irbesartan was developed by Sanofi Research (now part ofsanofi-aventis). It is jointly marketed by sanofi-aventis and Bristol-Myers Squibb under thetrade names Aprovel, Karvea, and Avapro.

It is marketed in Brazil by Sanofi-Aventis under the trade name Aprovel .

As with all angiotensin II receptor antagonists, irbesartan is indicated for the treatment ofhypertension. Irbesartan may also delay progression of diabetic nephropathy and is also indicated for the reduction of renal disease progression in patients with type 2 diabetes,^[1]hypertension and microalbuminuria (>30 mg/24 hours) or proteinuria (>900 mg/24 hours).^[2]

Irbesartan is also available in a combination formulation with a low dose thiazide diuretic, invariably hydrochlorothiazide, to achieve an additive antihypertensive effect. Irbesartan/hydrochlorothiazide combination preparations are marketed under similar trade names to irbesartan preparations, including Irda, CoIrda, CoAprovel, Karvezide,Avalide and Avapro HCT.

A large randomized trial following 4100+ men and women with heart failure and normal ejection fraction (>=45%) over 4+ years found no improvement in study outcomes or survival with irbesartan as compared to placebo.^[3]

BMS annual sales approx $1.3bn. Sanofi-aventis annual sales approx $2.1bn. In the United States, a generic version is available. Patent expired March 2012.

1. Lewis EJ, Hunsicker LG, Clarke WR, Berl T, Pohl MA, Lewis JB, Ritz E, Atkins RC, Rohde R, Raz I; Collaborative Study Group. (2001). "Renoprotective effect of the angiotensin-receptor antagonist irbesartan in patients with nephropathy due to type 2 diabetes". N Engl J Med 345 (12): 851–60. doi:10.1056/NEJMoa011303.PMID 11565517.
2.  Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. ISBN 0-9757919-2-3
3.  Massie BM, Carson PE, McMurray JJ, Komajda M, McKelvie R, Zile MR, Anderson S, Donovan M, Iverson E, Staiger C, Ptaszynska A (December 2008). "Irbesartan in patients with heart failure and preserved ejection fraction". N. Engl. J. Med. 359 (23): 2456–67.doi:10.1056/NEJMoa0805450. PMID 19001508.

4..........C. A. Bernhart, P. M. Perreaut, B. P. Ferrari, Y. A. Muneaux,
J.-L. A. Assens, J. Clement, F. Haudricourt, C. F. Muneaux,
J. E. Taillades, M.-A. Vignal, J. Gougat, P. R. Guiraudou, C.
A. Lacour, A. Roccon, C. F. Cazaubon, J.-C. Brelihre, G. Le
Fur, D. Nisato, J. Med. Chem. 1993, 36, 3371–3380.
5.... K. F. Croom, M. P. Curran, K. L. Goa, Drugs 2004 64,
999–1028.
6... C. Bernhard, J.-C. Breliere, J. Clement, D. Nisato, P. M. Perreaut, C. F. Muneaux, (Elf Sanofi) US 5 270 317; Chem. Abstr. 1993, 119, 95560.
7. S. Chava, M. Bandari, K. S. Mathuresh, (Matrix Laboratories) WO 2005/122699; Chem. Abstr. 2005, 144, 88292.
5. S. Zupan~i~, A. Pe~avar, R. Zupet, (Krka) WO 2006/073376;
Chem. Abstr. 2006, 145, 124576.
8. C. V. Kavitha, S. L. Gaonkar, J. N. Chandra, S. Narendra, C.
T. Sadashiva, K. S. Rangappa, Bioorg. Med. Chem. 2007, 15,
7391–7398.
9. S. Rádl, J. Stach, O. Klecán, (Zentiva) WO 2005/021535;
Chem. Abstr. 2005, 142, 298118.
10. B. Satyanarayana, Y. Anjaneyulu, P. Veerasomaiah, P. P.
Reddy, Heterocycl. Commun. 2007, 13, 223–228.
11. V. V. Korrapati, P. Rao, R. Dandala, V. K. Handa, I. V. S. Rao,
A. Rani, A. Naidu, Synth. Commun. 2007, 37, 2897–2905.
12. J. Havlí~ek, Z. Mandelová, R. Weisemann, I. Strˇelec, S.
Rádl, Collect. Czech. Chem. Commun. 2009, 77, 347.
Irbesartan of formula (I).

The chemical name of Irbesartan is 2-Butyl-3-[[2'-(lH-tetrazol-5-yl)[l,l'-biphenyl]-4- yl]methyl]-l,3-diazaspiro[4,4]non-l-en-4-one and formula is C₂SH₂SN₆O and molecular weight is 428.53. The current pharmaceutical product containing this drug is being sold by Sanofi Synthelabo using the tradename AVAPRO, in the form of tablets. Irbesartan is useful in the treatment of diabetic neuropathy, heart failure therapy and hypertension. Irbesartan is angiotension II type I (AΙIi)-receptor antagonist. Angiotension II is the principal pressor agent of the rennin-angiotension system and also stimulates aldosterone synthesis and secretion by adrenal cortex, cardiac contraction, renal resorption of sodium, activity of the sympathetic nervous system and smooth muscle cell growth. Irbesartan blocks the vasoconstrictor and aldosterone- secreting effects of angiotension II by selectively binding to the ATi angiotension II receptor. U.S. Pat. Nos. 5,270,317 and 5,559,233 describes a process for the preparation of N- substituted heterocyclic derivatives which involves reacting a heterocyclic compound of the formula

with a (biphenyl-4-yl)methyl derivative of the formula

wherein R₁, R₂, R₃, R₄, R₅, and t, z and Hal have the meanings given in said U.S. Pat. No.
5,270,317, in the presence of an inert solvent such as DMF, DMSO or THF, with a basic reagent, for example KOH, a metal alcoholate, a metal hydride, calcium carbonate or triethylamine. The products of the reaction were purified by chromatography.
U.S. Pat. Nos. 5,352,788, and 5,559,233, and WO 91/14679 also describe identical alkylation of the nitrogen atom of the heterocyclic compound with the halo-biphenyl compound using the same inert solvent and the same basic reagents.

• US5629331 describes a process for the preparation of irbesartan from 1-[(2'-cyanobiphenyl)4-yl)methyl]-2-n-butyl-4-spirocyclopentane-2-imidazolin-5-one using sodium azide, TEA.HCl in N-methylpyrrolidone. The product is isolated from the alkaline reaction mass after acidification to pH 4.7 to 5.8 and the crude product is recrystallised from IPA/water to get Form A and ethanol/water to get Form B.
• 
  
  WO 2005/051943 A1 describes a process for the preparing irbesartan wherein 1-[(2'-cyanobiphenyl-4-yl)methyl]-2-n-butyl-4-spirocyclopentane-2-imidazolin-5-one is reacted with tributyltin chloride, sodium azide and TBAB in toluene at reflux temperature for 20 hours. Product is isolated from the reaction mass as trityl irbesartan and then deprotected in methanol and formic acid to get irbesartan.
• 
  
  WO 2006/023889 describes a method for preparing irbesartan, wherein 1-(2'-cyanobiphenyl-4-yl)methyl)-2-n-butyl-4-spirocyclopentane-2-imidazolin-5-one is reacted with sodium azide and triethylamine hydrochloride in N-methyl-2-pyrrolidone to give irbesartan.
• 
  
  WO 2005/113518 describes a process for preparing irbesartan wherein cyano irbesartan in xylene, is reacted with tributyltin chloride and sodium azide at reflux temperature till reaction is completed followed by aqueous work-up and recrystallization to give irbesartaN
• The process involving use of zinc salt for the transformation of nitrile to tetrazole is a safe and efficient process as reported in JOC (2001) 66, 7945-50. The use of zinc salt for transforming nitrile to tetrazole has also been published in WO9637481 and US5502191 

Also Canadian Patent No. 2050769 describes the alkylation of the nitrogen atom of the heterocycle of the formula

with a compound of the formula

wherein X, R₁, Z₁ and Z₆ have the meanings given therein, in the presence of N,N- dimethylformamide and a basic reagent, such as alkali metal hydrides for example sodium or potassium hydride.
All of the above identified patents describe alkylation in solvents, such as N₅N- dimethylformamide or DMSO, etc. in the presence of a basic reagent, for example, a metal hydride or a metal alcoholate etc. The strong bases, such as metal hydride or a metal alcoholate require anhydrous reaction conditions. Since N,N-dimethylformamide is used as a solvent, its removal requires high temperature concentration by distillation, which can result in degradation of the final product. The product intermediate is also purified by chromatography which is commercially not feasible and cumbersome on large scale. Another process given in Canadian Patent No. 2050769 provides synthetic scheme as herein given below.

This process comprises the steps of protecting carboxylic group present on cyclopentane ring which is deprotected in consecutive step by vigourous hydrogenation condition in autoclave which is operationally difficult at a large scale.
US Patent No. 2004242894 also discloses the process of preparation of lrbesartan from 4- bromomethyl biphenyl 2'-(lH-tetrazol (2-triphenylmethyl) 5-yl) and Ethyl ester of 1- Valeramido cyclopentanecarboxylic acid in toluene in presence of base and PTC, and then hydrolyzing the protecting group. However this requires chromatographic purification.
This patent also discloses the process of preparation of tetrazolyl protected lrbesartan using 2,6 lutidine and oxalylchloride in toluene. However in this process the yield is as low as 30%.
US Patent No. 2004192713 discloses the process of preparation of lrbesartan by condensing the two intermediates via Suzuki coupling reaction. The reaction scheme is as given herein below.

However, this process has several disadvantages such as use of the reagents like butyl lithium and triisobutyl borate at low temp such as -20 to -30°C under Argon atmosphere condition which is difficult to maintain at commercial scale.
WO2005113518 discloses the process of preparation of Irbesartan by condensing n- pentanoyl cycloleucine (V) with 2-(4-aminomethyl phenyl) benzonitrile (VI) using dicyclocarbodiimide (DCC) and 1 -hydroxy benzotriazole as catalyst to give an open chain intermediate of formula (VIII) which is then cyclized in the presence of an acid, preferably trifluoro acetic acid to give cyano derivative of formula (VII) and which in turn is converted to Irbesartan by treating it with tributyl tin chloride and sodium azide.

In this application further describes another process comprising the steps of reacting 2- butyl-l,3-diazasρiro[4,4]non-l-en-4-one monohydrochloride (A) with 4-bromobenzyl bromide (B) in presence of base and solvent to give 3-[4-bromobenzyl]-2-butyl-l,3- diazaspiro[4,4]non-l-en-4-one (C) which is condensed with 2-[2'-(triphenylmethyl-2'H- tetrazol-5'-yl)phenyl boronic acid in the presence of tetrakis triphenyl phosphine palladium and base to give lrbesartan (I). However these processes suffer with several disadvantages such as it uses trifluoroacetic acid for the cyclization step which is highly corrosive material. The process requires an additional step of activation by DCC. This step not only increases number of steps but also create problem in handling DCC at an industrial scale as it is highly prone to hazard which makes the process least preferred on a large scale production of lrbesartan. Further it uses phenyl boronic acid derivative and triphenyl phosphine complex which are harmful for the skin and eye tissue and also harmful for respiratory system. Tetrakis triphenyl phosphine palladium is also a costly material which increases overall cost for the production of lrbesartan. Moreover the yield is as low as 22%. All the above patents/applications are incorporated herein as reference. In summary, prior art relating to the process for the preparation of lrbesartan suffers with several drawbacks such as i) It requires chromatographic purification of intermediates at various stages. ii) It requires specific autoclave conditions for a deprotection of protecting group. iii) It requires maintaining low temperature conditions such as -30⁰C and requires special handling care and air and moisture tight condition with the reagents such as butyl lithium and triisobutyl borate. iv) It uses hazardous and highly corrosive reagents, v) It suffers low yield problem. vi) All the process is having more number of reaction steps.

• Irbesartan is described in Bernhart et al., U.S. Patent No. 5,270,317 
• Irbesartan, is a potent, long-acting angiotensin II receptor antagonist which is particularly useful in the treatment of cardiovascular ailments such as hypertension and heart failure. Its chemical name is2-n-butyl-4-spirocyclopentane-1-[(2'-(tetrazol-5-yl)biphenyl-4-yl)methyl]-2-imidazolin-5-one.

Irbesartan is an antihypertensive agent known from EP 454511. From EP 708103, which discloses their X-ray spectra, two polymorphs are known where form A can be produced form a solvent system containing less than 10% of water, while Form B from a system with more than 10% of water. The specific morphological variant of form A can be prepared having properties as disclosed in EP 1089994. Additional form has been disclosed in WO 04089938. Amorphous irbesartan is known from WO 03050110. It is said that Irbesartan produced as taught in EP 454511 is a fluffy material with relatively low bulk and tap densities and undesirable flow characteristics, which consequently has unadvantageous electrostatic properties, among them a high chargeability as measured by tribugeneration between -30 and -40 nanocoulomb/g (10^'9As/g). Alternativelyirbesartan could be prepared by complex process using sonifications and/or temperature oscillations according to EP 1089994 to exhibit a chargeability as measured by tribugeneration between -0 and -10 nanocoulomb/g.
According to EP 454511 a solid composition in form of tablets is prepared by mixing the active ingredient with a vehicle such as gelatine, starch, lactose, magnesium stearate, talc, gum Arabic or the like and can be optionally coated. The compositions containing from 20% to 70% by weight of irbesartan are known from EP 747050.
WO 04/007482 teaches the acidification to pH 2 - 3,5 of trityl irbesartan, which is sufficient to remove the protecting group, but not to convert into an acid addition salt; WO 04/065383 is likewise silent on hydrohalide acid addition salts. WO
06/011859 relates to the preparation of a hydrochloride salt of irbesartan in order to incorporate it into a pharmaceutical formulation. W099/38847 mentions optional conversion of irbesartan into hydrochloride, hydrobromide or hydrogen sulfate salts
...................................................

.....................

WO2006023889A2
Example 1Preparation of Compounds of formula IVa and IVb:

• 
  
  
• 
  
  A jacketed 1,000 mL 3-neck flask was charged with 4'-methylbiphenyl-2-carbonitrile (Compound 1, 100.0 g) and CH₂CI₂ (500 mL) under nitrogen. To a 500 mL Erlenmeyer flask with magnetic stirrer, sodium bromate (NaBrO₃; 31.2 g) was dissolved in water (170 mL). The NaBrO₃ solution was transferred to the 1,000 mL flask and the reaction mixture was cooled to about 5 °C or less. Aqueous HBr solution (48 %, 105.0 g) was added to the 1,000 mL flask and the resulting reaction mixture was recycled though a UV lamp reactor. The reaction mixture was kept at 0-20 °C and the recycling was continued until the reaction was deemed complete by HPLC. Optionally, additional sodium bromate and hydrogen bromide may be added. The relative amounts of Compound 2 and Compound 3 were about 80-90% and about 10-20% respectively. Aqueous sodium metabisulfite solution (2.0 g of in 10 mL water) was added to the reaction mixture. Allow the phases to settle and the methylene chloride phase was washed with water and used in the next step without further purification.

Example 2Preparation of Compound II:

• 
  
  
• 
  
  A 1L 3-neck flask was charged with Compound V (134.0 g), MTBAC (5.0 g) and CH₂Cl₂ (170 mL) and cool to -5 to 5 °C. An aqueous solution of KOH (182.6 g in 212 mL water) was added slowly to the 1L flask and the reaction temperature was kept at ≤ 5 °C. The methylene chloride solution of Compound IVa and Compound IVb from Example 1 was added to the reaction mixture slowly, while maintaining the temperature at 0-10 °C. Diethyl phosphite (39.66g) was added drop wise at 0-10 °C. Check the reaction mixture for completion of the reduction reaction, and additional diethyl phosphite may be added.
• 
  
  The reaction mixture was allowed to warm to ambient (20-30 °C) and agitated until the reaction was deemed complete by HPLC. Water (150 mL) was added and the phases were separated. The organic layer was extracted with water (230 mL) and polish filtered.
• 
  
  The methylene chloride (which contained the crude Compound II) was distilled off and exchanged with about 400 mL of methyl tert-butyl ether (MTBE) (optionally, the MTBE recycled from washing below can be used here). Upon cooling, crystallization occurred (optionally seeds were added) and after further cooling to below 25°C, crystals of Compound II were isolated, washed with MTBE and dried in vacuum at a temperature of less than 60°C. HPLC retention time: 18.126 min. Typically, the yield was about 85 to about 88%. Alternatively, IPA could be used as the crystallization and washing solvent
• 
  
  Optionally, the solvent (i.e., MTBE or IPA) used to wash the crystals of Compound II above can be recycled and used to crystallize the crude Compound II in the next batch. Since the washed solvent contains Compound II as well as impurities, it was surprisingly found that the washed solvent can be recovered and used again in crystallizing the crude compound of formula II in the next batch without sacrificing its purity while increasing its yield.

Example 3Preparation of Compound I:

• 
  
  
• 
  
  A reactor was charged with Compound II (1 kg), triethylamine chlorhydrate (0.713 kg), sodium azide (0.337 kg) and N-methyl pyrrolidinone (2.07 kg), and the reaction mixture was heated to about 122°C under stirring. After completion of the reaction as determined by HPLC, the reaction mixture was cooled to about 45°C, and an aqueous solution of sodium hydroxide (35%, 5.99 kg) and water (3.0 kg) were added, the resulting mixture was stirred at a temperature between about 20 and about 40°C for about 0.5 hours. The aqueous phase was discarded and the organic phase was treated with toluene (1.73 kg) and water (5.0 kg), and stirred for about 0.5 hours at about 20 - about 30°C. The toluene phase was discarded and the aqueous phase was washed with ethyl acetate (1.8 kg) and treated with aqueous HCl until pH was adjusted to about 4.8 - about 5.2. Precipitation occurred and the resulting suspension was stirred for about 1 hour at about 20 - about 25°C. The precipitation was collected and washed with water three times (1.0 kg x 3). The crude wet product was recrystallized using a mixture of iso-propanol (0.393 kg) and water (4.5 kg). HPLC retention time: 11.725 min. The yield for Compound I was about 87%.

....................................................
SPECTRAL DATA
The ESI mass spectrum of irbesartan showed a protonated molecular ion peak at m/z 429.3 confirming the molecular weight 428. The fragmentation pattern of parent ion 429.3 showed the fragment ions at m/z 385.9, 235.1, 207, 195.4, 192.1, 180.2 and 84

The FT-IR spectrum exhibited a characteristic stretching absorption band at 1732 cm-1 for the carbonyl group of amide functionality. The presence of this band at higher frequency was due to the ring stretching due to five member ring system. Another band at 1614cm-1 was due to C=N stretching vibrations

1H and 13C- NMR were recorded using DMSO-d6 as a solvent. In 1H-NMR the signal due to tetrazole NH proton was not detected may probably due to the tautomerism.




DP 1 IS IMPURITY

.................................................
NMR
WO2007049293A1
¹H-NMR (DMSO d6): δppm 0.78 (t, 3H); 1.17-1.30 (sex, 2H); 1.40-1.50 (quent, 2H); 1.64-1.66 (m, 2H); 1.80-1.82 (m, 6H); 2.22-2.29 (t, 2H); 4.67 (s, 2H); 7.07 (s, 4H); 7.50- 7.68 (m, 4H) M⁺: 429.6
,.......................
m.p:181-182oC,
IR (KBr, cm-1) 1732 (C=O), 1616 (C=N); 1H NMR (DMSO-d6): δ 7.95–7.32 (m, 8 H), 4.80 –4.60 (s, 2 H), 3.60– 3.00 (br s, 1 H), 2.40– 2.20 (t, 2 H , J = 6.04 Hz), 2.00– 1.60 (m, 8 H),1.60–1.45 (quint, 2 H), 1.40– 1.20 (sext, 2 H), 0.91–0.70 (t, 3H, J = 7.41 Hz);
13C-NMR (DMSOd6): δ 186.5, 162.0,155.9, 141.9, 139.2, 137.2. 131.9, 131.4, 130.1, 128.7, 127.1, 124.3, 76.7, 43.1,
37.7, 28.3, 27.4, 26.3, 22.4, 14.5;
MS: m/z= 429 [M+1];
Anal. Calcd for C25H28N6O : C, 70.07; H,
6.59; N, 19.61. Found: C, 70.04; H, 6.57; N, 19.58.
http://www.acgpubs.org/OC/2011/Volume%204/Issue%201/13-OC-1106-199.pdf
............................

1H NMR in DMSO-D₆ : 7.68 (d. 2H, Ar-H), 7.52 (d, 2 H, Ar-H), 7.08 (s, 4 H, Ar-H), 4.68(s, 2H, -CH2), 2.69(t,2H,-CH2),2.18(m,2H,-CH2),1.83(m,2H,-CH2),1.81 (t, 2H, -CH2), 1.65 (t, 2H, -CH2), 1.45 (m, 2 H, -CH2), 1.24(m , 2H, -CH2), 0.77 (t, 3H, -CH3),

IR (KBR): 3061 (Aromatic C-H stretching), 2960 (Aliphatic C-H stretching), 3443 (N-H stretching), 1733 (C=0 stretching), 1617(CN stretching), 1337.99(CN stretching), 1407(N=N stretching) cm^"1.

WO2013171643



...................................................................
HPLC condition:
Column: Alltima C18 (Alltech 88050) 15.0cm in length x 4.6mm in internal diameter and 5 micron particle size;
Column temperature: 40 C;
Solvent A: Buffer solution A 1.1 g of heptanesulfonic acid in 1 liter of water and adjust the pH to 2.5;
Solvent B: Methanol Flow rate: 1.2mL/min;
Gradient Elution Condition:
Time% A % %B
0 min 50 50
35 min 15 85
Detector: 240 nm;
Injection volume: 10 uL.
The chromatographic purity of
the compounds was analyzed using Agilent 1200 series HPLC instrument under the following conditions:
Column : Symmetry C18, 4.6 × 75 mm, 3.5 µm
Mobile phase : Eluent A: Deionized water, Eluent B: HPLC grade Methanol
Chromatographic Conditions
a. Column temperature : Ambient
b. Sample compartment : Ambient
c. Detector : 225 nm
d. Injection volume : 10 µL
e. Run time : 45 minutes
f. Flow rate :1.0 mL/min
g. Injector :Auto sampler with variable volume injector
h. Diluent : HPLC grade Acetonitrile

DOXOFYLLINE SPECTRAL DATA

DOXOFYLLINE

69975-86-6  CAS NO

7-(1,3-dioxolan-2-ylmethyl)-1,3-dimethylpurine-2,6-dione

Formula	C11H14N4O4
Mol. mass	266.25 g/mol

Doxofylline (INN), (also known as doxophylline) is a xanthine derivative drug used in the treatment of asthma.^[1]

It has antitussive and bronchodilator^[2] effects, and acts as aphosphodiesterase inhibitor.^[3]

In animal and human studies, it has shown similar efficacy to theophylline but with significantly fewer side effects.^[4]

Unlike other xanthines, doxofylline lacks any significant affinity for adenosine receptorsand does not produce stimulant effects. This suggests that its antiasthmatic effects are mediated by another mechanism, perhaps its actions on phosphodiesterase.^[1]

Doxofylline, [7-(1, 3-dioxolan-2-ylmethyl)-3, 7-dihydro-1, 3-dimethyl-1H-purine-2, 6-dione] is a new bronchodilator xanthine based drug which differs from theophylline by the presence of dioxalane group at position 7. It is used in the treatment of bronchial asthma, chronic obstructive pulmonary disease (COPD), and chronic bronchitis . The mechanism of action is similar to that of theophylline in that it inhibits phosphodiesterase (PDE-IV), thereby preventing breakdown of cyclic adenosine monophosphate (cAMP). Increase in cAMP inhibits activation of inflammatory cells resulting in bronchodilating effect [52]. In contrast to theophylline, doxofylline has very low affinity towards adenosine A1 and A2 receptors which explain its better safety profile

Doxofylline (7-(l,3-dioxalan-2-ylmethyl)-theophylline) is a drug derived from theophylline which is used in therapy as a bronchodilator, with anti-inflammatory action, in reversible airway obstruction. It is commonly administered in doses ranging from 800 to 1200 mg per day, orally, according to a dosage which provides for the intake of two to three dosage units per day in order to maintain therapeutically effective haematic levels. The doxofylline tablets commercially available generally contain 400 mg of active ingredient and release almost all the drug within one hour from intake. The half- life of the drug is around 6-7 hours and for this reason several administrations are required during the 24-hour period.

Obviously a drop in haematic concentration of the drug in an asthmatic patient or patient suffering from COPD (chronic obstructive pulmonary disease) can result in serious consequences, in which case the patient must have recourse to rescue medication, such as salbutamol inhalers.

Pharmaceutical techniques for obtaining the modified release of drugs have been known for some time, but no modified release formulation of doxofylline is known. In fact the present inventors have observed that there are significant difficulties in the production of a doxofylline formula that can be administered only once a day and in particular have encountered problems correlated with bioequivalence.

Various attempts to formulate doxofylline in modified release systems, with different known polymers, have not provided the desired results, i.e. a composition that can be administered once a day, bio equivalent to the plasmatic concentration obtained with the traditional compositions currently on sale. In fact currently, dosage units containing 400 mg of active ingredient are currently administered two/three times a day for a daily average of approximately 1000 mg of active ingredient, a dosage considered necessary to maintain the therapeutic haematic levels of doxofylline.

Such a dosage unit is currently marketed by Dr. Reddy's Laboratories Ltd as DOXOBID and has the following quali-quantitative composition: doxofylline (400 mg), colloidal silicon dioxide (13 mg), corn starch (63 mg), mannitol (40 mg), povidone (7 mg), microcrystalline cellulose (64 mg), talc (30 mg), magnesium stearate (3 mg) and water (0.08 ml).

1.  Cirillo R, Barone D, Franzone JS (1988). "Doxofylline, an antiasthmatic drug lacking affinity for adenosine receptors". Arch Int Pharmacodyn Ther 295: 221–37.PMID 3245738.
2. Poggi R, Brandolese R, Bernasconi M, Manzin E, Rossi A (October 1989). "Doxofylline and respiratory mechanics. Short-term effects in mechanically ventilated patients with airflow obstruction and respiratory failure". Chest 96 (4): 772–8.doi:10.1378/chest.96.4.772. PMID 2791671.
3.  Dini FL, Cogo R (2001). "Doxofylline: a new generation xanthine bronchodilator devoid of major cardiovascular adverse effects". Curr Med Res Opin 16 (4): 258–68.doi:10.1185/030079901750120196. PMID 11268710.
4. Sankar J, Lodha R, Kabra SK (March 2008). "Doxofylline: The next generation methylxanthine". Indian J Pediatr 75 (3): 251–4. doi:10.1007/s12098-008-0054-1.PMID 18376093.

• Dali Shukla, Subhashis Chakraborty, Sanjay Singh & Brahmeshwar Mishra. Doxofylline: a promising methylxanthine derivative for the treatment of asthma and chronic obstructive pulmonary disease. Expert Opinion on Pharmacotherapy. 2009; 10(14): 2343-2356, DOI 10.1517/14656560903200667, PMID 19678793

At present, domestic synthetic Doxofylline composed of two main methods: one is by the condensation of theophylline prepared from acetaldehyde and ethylene glycol, but this method is more complex synthesis of acetaldehyde theophylline, require high periodate oxidation operation. Another is a halogenated acetaldehyde theophylline and ethylene glycol is prepared by reaction of an organic solvent, the method were carried out in an organic solvent, whereby the product Theophylline caused some pollution, conducive to patients taking.

current domestic Doxofylline synthetic methods reported in the literature are: 1, CN Application No. 94113971.9, the name "synthetic drugs Doxofyllinemethod" patents, the patent is determined by theophylline with a 2 - (halomethyl) -1,3 - dimethoxy-dioxolane in a polar solvent, with a base made acid absorbent,Doxofylline reaction step. 2,  CN Application No. 97100911.2, entitled "Synthesis of Theophylline," the patent, the patent is obtained from 7 - (2,2 - dialkoxy-ethyl) theophylline with ethylene glycol in N, N-dimethylformamide solvent with an alkali metal carbonate to make the condensing agent, p-toluenesulfonic acid catalyst in the condensation Doxofylline.

Doxofylline of xanthine asthma drugs, and its scientific name is 7 - (1,3 - dioxolan - ethyl methyl) -3,7 - dihydro-1,3 - dimethyl-1H - purine-2 ,6 - dione. The drug developed by the Italian Roberts & Co. in 1988, listed its tablet tradename Ansimar. This product is compared with similar asthma drugs, high efficacy, low toxicity, oral LD50 in mice is 1.5 times aminophylline, non-addictive. Adenosine and its non-blocking agents, it does not produce bronchial pulmonary side effects, no aminophylline like central and cardiovascular system. U.S. patent (US4187308) reported the synthesis of doxofylline, theophylline and acetaldehyde from ethylene glycol p-toluenesulfonic acid catalyst in the reaction of benzene as a solvent Doxofylline. Theophylline acetaldehyde by the method dyphylline derived reaction with a peroxy periodate or 7 - (2,2 - dialkoxy-ethyl) ammonium chloride aqueous solution in the decomposition of theophylline converted to acetaldehyde theophylline . Former method is relatively complex, and the high cost of using periodic acid peroxide, low yield after France. And theophylline acetaldehyde and ethylene glycol solvent used in the reaction of benzene toxicity, harm to health, and the yield is low, with an average around 70%, not suitable for industrial production.

Theophylline-7-acetaldehyde (I) could react with ethylene glycol (II) in the presence of p-toluenesulfonic acid in refluxing benzene to produce Doxofylline.

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CN102936248A

https://www.google.co.in/patents/CN102936248A?cl=en&dq=doxofylline&hl=en&sa=X&ei=prmeUp_yKMqClQXlj4DYDw&ved=0CIABEOgBMAg

the reaction is:

a, anhydrous theophylline and bromoacetaldehyde ethylene glycol as the basic raw material, purified water as a solvent with anhydrous sodium carbonate as acid-binding agent;

NMR

UV (95% C2H5OH, nm) λmax273 (ε9230); λmin244 (ε2190)

IR (KBr, cm-1) 1134 (CO); 1233 (CN) ; 1547 (C = N); 1656 (C = C); 1700 (C = O); 2993 (CH)

1H-NMR [CDCl3, δ (ppm)] 3.399 (s, 3H, N-CH3); 3.586 (S, 3H, N-CH3); 3.815-3.885 (m, 4H, OCH2 × 2); 4.581 (d, 2H, CH2); 5.211 (t, 1H, CH ); 7.652 (S, 1H, CH = N)

13C-NMR [CDCL3, δ (ppm)] 27.88 (CH3); 29.69 (CH3); 47.87 (CH2); 65.37 ( OCH2); 100.76 (CH); 107.26 (C = C); 142.16 (CH = N); 148.22 (C = C); 151.59 (C = O); 155.25 ( C

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Spectral data of doxofylline
The ESI mass spectrum exhibited a protonated molecular ion peak at m/z 267 in positive ion mode indicating the molecular weight of 266. The tandem mass spectrum showed the fragment ions m/z 223, 181.2, 166.2, 138.1, 124.1 and 87.1.

The FT-IR spectrum, two strong peaks at 1697cm-1 and 1658cm-1 indicated presence of two carbonyl groups. A strong peak at frequency 1546cm-1 indicated presence of C=N stretch. A medium peak at 1232cm-1 was due to C-O stretch

FT IR

1H and 13C-NMR spectra of doxofylline and its degradation products were recorded by using Bruker NMR 300MHz instrument with a dual broad band probe and z-axis gradients. Spectra were recorded using DMSO-d6 as a solvent and tetramethylsilane as an internal standard.

1H NMR

13 C NMR

COMPARISONS