1-[3-(2-dimethylaminoethyl)-1H-indol-5-yl]- N-methyl-methanesulfonamide
Mol. mass295.402 g/mol
CAS number103628-46-2 
Melting point: mp 169-171°
Therap-Cat: Antimigraine.
Keywords: Antimigraine; Serotonin Receptor Agonist.
NDA 020626,GSK, IMITREX, 1997
Avanir Pharmaceuticals has filed a new drug application (NDA) with the US Food and Drug Administration (FDA) for approval of its new breath-powered investigational drug-device combination product, 'AVP-825', for the acute treatment of migraines.  click on title  Avanir files new drug application for migraine drug 

Sumatriptan moleculeSUMATRIPTAN

CAS Registry Number:
103628-48-4 ((1:1) salt), 103628-47-3 ((2:1) salt), 103628-46-2 (free base)
GlaxoSmithKline (Originator), Atrix (Formulation), Nastech (Formulation), NovaDel Pharma (Formulation)
Manufacturers' Codes: GR-43175C
Trademarks: Imigran (GSK); Imitrex (GSK); Imiject (GSK)
Molecular Formula: C14H21N3O2S.C4H6O4
Molecular Weight: 413.49
Percent Composition: C 52.28%, H 6.58%, N 10.16%, O 23.22%, S 7.75%
Properties: mp 165-166°.
Melting point: mp 165-166°
Launched-1991, Acute Attacks of Migraine, Treatment of, Analgesic and Anesthetic Drugs, Antimigraine Drugs, 5-HT1B Agonists, 5-HT1D Agonists
AVP-825 is an investigational drug-device combination product consisting of low-dose sumatriptan powder delivered intranasally utilizing a novel Breath Powered delivery technology. If approved, AVP-825 would be the first and only fast-acting, dry-powder intranasal form of sumatriptan for the treatment of migraine.
The Breath Powered delivery technology is activated by user's breath to propel medications deep into the nasal cavity where absorption is more efficient and consistent than through most other routes. A user exhales into the device, automatically closing the soft palate and sealing off the nasal cavity completely. Through a sealing nosepiece placed into the nostril, the exhaled breath carries medication from the device directly into one side of the nose. Narrow nasal passages are gently expanded and medication is dispersed deep into the nasal cavity reaching areas where it can be rapidly absorbed. As the medication is delivered, the air flows around to the opposite side of the nasal cavity and exits through the other nostril. Closure of the soft palate helps prevent swallowing or inhalation of sumatriptan powder into the lungs.
Canada2469019APPROVED 2005-09-13EXP 2022-12-04
United States6135979                 1997-03-21       2017-03-21
United States5705520                 1994-12-10       2011-12-10
Canada2098302                 2001-10-16       2011-12-10
Patent NoPatentExpiryuse code
5307953Dec 2, 2012
5307953*PEDJun 2, 2013
5554639Sep 10, 2013U-232...METHOD OF TREATING MIGRAINE
5554639*PEDMar 10, 2014
Sumatriptan is a synthetic drug belonging to the triptan class, used for the treatment of migraine headaches. Structurally, it is an analog of the naturally occurring neuro-active alkaloids dimethyltryptamine (DMT), bufotenine, and 5-methoxy-dimethyltryptamine, with an N-methyl sulfonamidomethyl- group at position C-5 on the indole ring.[1]
Sumatriptan is produced and marketed by various drug manufacturers with many different trade names such as Sumatriptan, Imitrex, Treximet, Imigran, Imigran recovery.
Large doses of sumatriptan can cause sulfhemoglobinemia, a rare condition in which the blood changes from red to greenish-black, due to the integration of sulfur into the hemoglobin molecule.[2] If sumatriptan is discontinued, the condition reverses within a few weeks.
Serious cardiac events, including some that have been fatal, have occurred following the use of sumatriptan injection or tablets. Events reported have included coronary artery vasospasm, transient myocardial ischemia, myocardial infarctionventricular tachycardia, and ventricular fibrillation.
The most common side-effects[3] reported by at least 2% of patients in controlled trials of sumatriptan (25, 50, and 100 mg tablets) for migraine are atypical sensations (paresthesias and warm/cold sensations) reported by 4% in the placebo group and 5–6% in the sumatriptan groups, pain and other pressure sensations (including chest pain) reported by 4% in the placebo group and 6–8% in the sumatriptan groups, neurological events (vertigo) reported by less than 1% in the placebo group and less than 1% to 2% in the sumatriptan groups. Malaise/fatigue occurred in less than 1% of the placebo group and 2–3% of the sumatriptan groups. Sleep disturbance occurred in less than 1% in the placebo group to 2% in the sumatriptan group.


Sumatriptan is structurally similar to serotonin (5HT), and is a 5-HT (types 5-HT1D and 5-HT1B[4]agonist. The specific receptor subtypes it activates are present on the cranial arteries and veins. Acting as an agonist at these receptors, sumatriptan reduces the vascular inflammation associated with migraines.
The specific receptor subtype it activates is present in the cranial and basilar arteries. Activation of these receptors causes vasoconstriction of those dilated arteries. Sumatriptan is also shown to decrease the activity of the trigeminal nerve, which, it is presumed, accounts for sumatriptan's efficacy in treating cluster headaches. The injectable form of the drug has been shown to abort a cluster headache within fifteen minutes in 96% of cases.[5]

Sumatriptan is administered in several forms; tablets, subcutaneous injection, and nasal spray. Oral administration (as succinate) suffers from poorbioavailability, partly due to presystemic metabolism—some of it gets broken down in the stomach and bloodstream before it reaches the target arteries. A new rapid-release tablet formulation has the same bioavailability, but the maximum concentration is achieved on average 10–15 minutes earlier. When injected, sumatriptan is faster-acting (usually within 10 minutes), but the effect lasts for a shorter time. Sumatriptan is metabolised primarily by monoamine oxidase A into an indole acetic acid analogue, part of which is further conjugated with glucuronic acid. These metabolites are excreted in the urine and bile. Only about 3% of the active drug may be recovered unchanged.
There is no simple, direct relationship between sumatriptan concentration (pharmacokinetics) per se in the blood and its anti-migraine effect (pharmacodynamics). This paradox has, to some extent, been resolved by comparing the rates of absorption of the various sumatriptan formulations, rather than the absolute amounts of drug that they deliver.[6][7]

Sumatriptan was the first clinically available triptan (in 1991). In the United States, it is available only by medical prescription. However, it can be bought over the counter in the UK and Sweden in 50 mg dosage. Several dosage forms for sumatriptan have been approved, including tablets, solution for injection, and nasal inhalers.
On April 15, 2008, the US FDA approved Treximet, a combination of sumatriptan and naproxen, an NSAID.[8] This combination has shown a benefit over either medicine used separately.[9]
In July 2009, the US FDA approved a single-use jet injector formulation of sumatriptan. The device delivers a subcutaneous injection of 6 mg sumatriptan, without the use of a needle.Autoinjectors with needles have been previously available in Europe and North America for several years.[10]
Phase III studies with a iontophoretic transdermal patch (Zelrix/Zecuity) started in July 2008.[11] This patch uses low voltage controlled by a pre-programmed microchip to deliver a single dose of sumatriptan through the skin within 30 minutes.[12][13]Zecuity was approved by the US FDA in January 2013.[14]

Sumatriptan vials 100 5509
On November 6, 2008, Par Pharmaceutical announced that it would begin shipping generic versions of sumatriptan injection (sumatriptan succinate injection) 4 mg and 6 mg starter kits and 4 mg and 6 mg pre-filled syringe cartridges to the trade immediately. In addition, Par anticipates launching the 6 mg vials early in 2009.[15]
Mylan Laboratories Inc., Ranbaxy, Sandoz, Dr. Reddy's Pharmaceuticals and other companies have received FDA approval for generic versions of Imitrex tablets in 25-, 50-, and 100-milligram doses since 2009. The drug is available in U.S. and European markets, since Glaxo's patent protections have expired in those jurisdictions. However, sales of a generic delivered via nasal spray are still restricted in the United States.
See also Sumavel DosePro (above).[10]


hydrogenation of nitrile with pd/c in presence of dimethyl amine
Sumatriptan synth.png
The diazotation of 4-amino-N-methylbenzenemethanesulfonamide (I) with NaNO2-HCl followed by reduction with SnCl2 gives the 4-hydrazino compound (II), which is condensed with (phenylthio)acetaldehyde (III) in ethanol yielding the ethylideneamino compound (IV). The cyclization of (IV) with HCl in ethanol affords N-methyl-3-(phenylthio)-1H-indole-5-methansulfonamide (V), which is desulfurized with RaNi in refluxing ethanol-water to give N-methyl-1H-indole-5-methanesulfonamide (VI). The reaction of (VI) with oxalyl chloride and dimethylamine yields the oxalyl derivative (VII), which is finally reduced with LiAlH4 in refluxing THF.
The condensation of hydrazine (II) with 4,4-dimethoxy-N,N-dimethylbutylamine (VIII) by means of HCl in water gives the butylidenehydrazino compound (IX), which is cyclized with polyphosphate ester (PPE) in CHCl3.
Beilstein J. Org. Chem. 2011, 7, 442–495.
ref are below article


The neuroamine transmitter serotonin contains an indole ring, so it is not surprising that indoles are a recurring theme in many drugs affecting central nervous system (CNS) function including antidepressants, antipsychotics, anxiolytics and antimigraine drugs, as well as psychedelic agents. Indole is also one of the best represented heterocyclic motifs present in the top selling pharmaceuticals, being found in eight of the top 200 drugs, with five of these belonging to the triptan family of antimigraine treatments. The classical Fischer indole synthesis is usually reported as one of the first choice routes to prepare these scaffolds. Drugs such as GSK’s serotonin receptor modulators sumatriptan (49, Imitrex) and zolmitriptan (50, Zomig) use the Fischer indole synthesis at a late stage in order to form the desired compound albeit in only low to moderate yields (Scheme 9).
Scheme 9: Key steps in the syntheses of sumatriptan and zolmitriptan.
However, in sumatriptan the indole product resulting from the Fischer synthesis can still react further which leads to the formation of by-products and significantly reduced yields. One way to minimise this was to protect the nitrogen of the sulfonamide group prior to indole formation [11]. This leads not only to an increased yield in the indole forming step (to 50%) but also facilitates chromatographic purification. The dimethylamino group can be present from the beginning of the synthesis or can be introduced via displacement of chloride or reduction of a cyano moiety. Alternatively, the dimethyl ethylene amine side chain can be introduced in position 3 via a Friedel–Crafts-type acylation. The resulting acid chloride is transformed in situ to the corresponding amide which on reduction with lithium aluminium hydride affords sumatriptan (Scheme 10) [12].
Scheme 10: Introduction of the N,N-dimethylaminoethyl side chain.
In the standard Fischer indole synthesis a hydrazine, which is most commonly derived from the corresponding diazonium salt, is reacted with a suitable carbonyl compound. Alternatively, the Japp–Klingemann reaction can be used to directly couple the diazonium salt with a β-ketoester to obtain a hydrazone which can then undergo indole ring formation (Scheme 11) [13].
Scheme 11: Japp–Klingemann reaction in the synthesis of sumatriptan.
As can be seen from Scheme 11 the indole 59 prepared via the Japp–Klingemann reaction is substituted at position 2 by an ester group which prevents reaction with electrophiles, thereby reducing the amount of undesired by-products. A simple sequence of hydrolysis and decarboxylation then affords sumatriptan [14].
All the reported methods for the synthesis of sumatriptan begin with the sulfonamide group already present on the aromatic ring and several routes are possible to introduce this functional group. The scalable route to the sulfonamides inevitably involves the preparation of the sulfonyl chloride intermediate which is then trapped with the desired amine. The sulfonyl chloride can also be prepared from the corresponding hemithioacetal 61 by treatment with NCS in wet acetic acid (Scheme 12). This efficient oxidation produces only methanol and formaldehyde as by-products [15].
Scheme 12: Synthesis of the intermediate sulfonyl chlorides 62 and 63.
  1. 11. Pete, B.; Bitter, I.; Szántay, C., Jr.; Schön, I.; Töke, L. Heterocycles 1998, 48, 1139–1149. doi:10.3987/COM-97-8087
  2. 12...Oxford, A. W. Indole Derivative. U.S. Patent 5,037,845, Aug 6, 1991.
  3. 13...Japp, F. R.; Klingemann, F. Chem. Ber. 1887, 20, 2942–2944. doi:10.1002/cber.188702002165
  4. Pete, B.; Bitter, I.; Harsányi, K.; Töke, L. Heterocycles 2000, 53, 665–673. doi:10.3987/COM-99-8815
  5. Kim, D.-W.; Ko, Y. K.; Kim, S. H. Synthesis 1992, 12, 1203–1204. doi:10.1055/s-1992-26333

References for full article

  1.  The presence of the sulfonamide group in the molecule does not make sumatriptan a "sulfa drug", since it does not have any anti-microbial properties.
  2.  "Patient bleeds dark green blood"BBC News. 8 June 2007. Retrieved 6 March 2010.
  3.  Tablets
  4.  Razzaque Z, Heald MA, Pickard JD, et al. (1999). "Vasoconstriction in human isolated middle meningeal arteries: determining the contribution of 5-HT1B- and 5-HT1F-receptor activation".Br J Clin Pharmacol 47 (1): 75–82. doi:10.1046/j.1365-2125.1999.00851.xPMC 2014192.PMID 10073743.
  5.  Treatment of acute cluster headache with sumatriptan. The Sumatriptan Cluster Headache Study Group. N Engl J Med 1991;325:322-6.
  6.  Fox, A. W. (2004). "Onset of effect of 5-HT1B/1D agonists: a model with pharmacokinetic validation". Headache 44 (2): 142–147. doi:10.1111/j.1526-4610.2004.04030.x.PMID 14756852edit
  7.  Freidank-Mueschenborn, E.; Fox, A. (2005). "Resolution of concentration-response differences in onset of effect between subcutaneous and oral sumatriptan". Headache 45 (6): 632–637. doi:10.1111/j.1526-4610.2005.05129a.xPMID 15953294edit
  8.  GSK press release – Treximet (sumatriptan and naproxen sodium) tablets approved by FDA for acute treatment of migraine
  9.  Brandes JL, Kudrow D, Stark SR, et al. (April 2007). "Sumatriptan-naproxen for acute treatment of migraine: a randomized trial"JAMA 297 (13): 1443–54.doi:10.1001/jama.297.13.1443PMID 17405970.
  10.  Brandes, J.; Cady, R.; Freitag, F.; Smith, T.; Chandler, P.; Fox, A.; Linn, L.; Farr, S. (2009). "Needle-free subcutaneous sumatriptan (Sumavel DosePro): bioequivalence and ease of use.". Headache 49 (10): 1435–1444. doi:10.1111/j.1526-4610.2009.01530.x.PMID 19849720edit
  11. NCT00724815 The Efficacy and Tolerability of NP101 Patch in the Treatment of Acute Migraine (NP101-007)
  12.  SmartRelief -electronically assisted drug delivery (iontophoresis)
  13.  Pierce, M; Marbury, T; O'Neill, C; Siegel, S; Du, W; Sebree, T (2009). "Zelrix: a novel transdermal formulation of sumatriptan". Headache 49 (6): 817–25. doi:10.1111/j.1526-4610.2009.01437.xPMID 19438727.
  14.  Zecuity Approved by the FDA for the Acute Treatment of Migraine
  15.  "PAR PHARMACEUTICAL BEGINS SHIPMENT OF SUMATRIPTAN INJECTION"Par Pharmaceutical. 2008-11-06. Retrieved 2008-11-25.
  16. Serotonin 5HT1-receptor agonist. Prepn: M. D. Dowle, I. H. Coates, DE 3320521eidem, US 4816470; A. W. Oxford, GB 2162522 (1983, 1989, 1986 all to Glaxo).
  17. Receptor binding studies: P. P. A. Humphrey et al., Br. J. Pharmacol.94, 1123 (1988); P. Schoeffter, D. Hoyer, Arch. Pharmacol. 340, 135 (1989).
  18. LC-MS determn in plasma: J. Oxford, M. S. Lant, J. Chromatogr. 496, 137 (1989).
  19. Clinical evaluations in migraine: A. Doenicke et al., Lancet 1, 1309 (1988);
  20. Subcutaneous Sumatriptan International Study Group, N. Engl. J. Med. 325, 316 (1991); in acute cluster headache: Sumatriptan Cluster Headache Study Group, ibid. 322.
  21. Review of pharmacology and clinical experience: S. J. Peroutka, Headache 30 (Suppl. 2), 554-560 (1990).
  22. Drugs Fut 1989,14(1),35
US80889181-4-2012Noncardiotoxic pharmaceutical compounds
US20100163631-22-2010Fixed Combination Dosage Forms for the Treatment of Migraine
EP08406305-7-2009Patient controlled drug delivery device
US20090682623-13-2009Rapid dissolution of combination products
US50378458-7-1991Indole derivative
US49389677-4-1990Pharmaceutical formulations
US44637088-8-1984Fuel and water homogenizer
Avanir Pharmaceuticals, Inc. is a biopharmaceutical company focused on bringing innovative medicines to patients with central nervous system disorders of high unmet medical need. As part of our commitment, we have extensively invested in our pipeline and are dedicated to advancing medicines that can substantially improve the lives of patients and their loved ones. For more information about Avanir, please visit
AVANIR® is a trademark or registered trademark of Avanir Pharmaceuticals, Inc. in the United States and other countries. All other trademarks are the property of their respective owners.
Avanir Pharmaceuticals, Inc. licensed exclusive rights for the development and commercialization of AVP-825, a novel Breath Powered intranasal system containing a low-dose sumatriptan powder from OptiNose Inc. of Yardley, PA.
IMITREX Tablets contain sumatriptan succinate, a selective 5-HT1B/1D receptor agonist. Sumatriptan succinate is chemically designated as 3-[2-(dimethylamino)ethyl]-N-methyl-indole- 5-methanesulfonamide succinate (1:1), and it has the following structure:
IMITREX Tablets contain sumatriptan succinate, a selective 5-HT1B/1Dreceptor agonist. Sumatriptan succinate is chemically designated as 3-[2-(dimethylamino)ethyl]-N-methyl-indole- 5-methanesulfonamide succinate (1:1), and it has the following structure:
IMITREX (sumatriptan succinate) Structural Formula Illustration
The empirical formula is C14H21N3O2S•C4H6O4, representing a molecular weight of 413.5. Sumatriptan succinate is a white to off-white powder that is readily soluble in water and in saline.
Each IMITREX Tablet for oral administration contains 35, 70, or 140 mg of sumatriptan succinate equivalent to 25, 50, or 100 mg of sumatriptan, respectively. Each tablet also contains the inactive ingredients croscarmellose sodium, dibasic calcium phosphate, magnesium stearate, microcrystalline cellulose, and sodium bicarbonate. Each 100-mg tablet also contains hypromellose, iron oxide, titanium dioxide, and triacetin.



1 Vote

Eletriptan, UK-116044-04(HBr salt), UK-116044, Relpax
143322-58-1  CAS OF FREE BASE
143577-61-1 (hemisuccinate), 179041-30-6 (monofumarate), 177834-92-3 (monoHBr salt), 180637-87-0 (monosuccinate)
(R)-3-[(-1-methylpyrrolidin-2-yl)methyl]-5-(2-phenylsulfonylethyl)- 1H-indole
Eletriptan hydrobromide is a selective serotonin (5-HT1) agonist, used for the acute treatment of the headache phase of migraine attacks.
RELPAX (eletriptan hydrobromide) tablets contain eletriptan hydrobromide, which is a selective 5-hydroxytryptamine 1B/1D (5-HT1B/1D) receptor agonist. Eletriptan hydrobromide is chemically designated as (R)-3-[(1-Methyl-2-pyrrolidinyl)methyl]-5-[2-(phenylsulfonyl)ethyl]-1H-indole monohydrobromide, and it has the following chemical structure:
RELPAX® (eletriptan hydrobromide) Structural Formula Illustration
The empirical formula is C22H26N2O2S . HBr, representing a molecular weight of 462.43. Eletriptan hydrobromide is a white to light pale colored powder that is readily soluble in water.
Each RELPAX Tablet for oral administration contains 24.2 or 48.5 mg of eletriptan hydrobromide equivalent to 20 mg or 40 mg of eletriptan, respectively. Each tablet also contains the inactive ingredients microcrystalline cellulose NF, lactose monohydrate NF, croscarmellose sodium NF, magnesium stearate NF, titanium dioxide USP, hypromellose, triacetin USP and FD&C Yellow No. 6 aluminum lake.
United States61109401997-08-292017-08-29
United States55456441996-12-262016-12-26
EP 0592438; JP 1993507288; JP 1997003063; US 5545644; WO 9206973, EP 0776323; JP 1997512283; US 6110940; WO 9606842, EP 1088817
U.S. Pat. No. 5,545,644A1 describes a synthetic process for Eletriptan. 5-Bromoindole was acylated at the 3-position by reacting the magnesium salt of 5-bromoindole. This process results in a dimer formation in the final Pd/C reduction stage which poses problems in purification which further leads to decrease in yields.
U.S. Pat. No. 7,288,662B2 discloses methods to circumvent the problems associated with dimer formation described in U.S. Pat. No. 5,545,644A1. The indole-nitrogen was acetylated prior to hydrogenation and later deacetylated to give pure Eletriptan. However, this process introduced two additional steps into the synthesis which is time consuming and subsequently costly.
WO2005/103035A1 discloses Eletriptan synthesis by a Fischer Indole process. However, enantiomeric purity of the finished product depends on the purity of an acetal intermediate which might require asymmetric synthesis or optical resolution. Eletriptan obtained in the reported procedure had about 94% enantiomeric excess.
Eletriptan (trade name Relpax, used in the form of eletriptan hydrobromide) is a second generation triptandrug intended for treatment of migraineheadaches. It is used as an abortive medication, blocking a migraine attack which is already in progress. Eletriptan is marketed and manufactured by Pfizer Inc. It is sold in the US and Canada under the brand name Relpax, and in several other countries under the brand name Relert.
Eletriptan was approved by the U.S. Food and Drug Administration (FDA) on December 26, 2002, for the acute treatment of migraine with or without aura in adults.[1] It is available only by prescription in the United States and Canada. It is not intended for the prophylactic therapy of migraine or for use in the management of hemiplegic or basilar migraine. It is available in 20 mg, 40 mg and 80 mg strengths.
Eletriptan is covered by U.S. Patent no. 5545644[1][2] and U.S. Patent no. 6110940;[1][3] the FDA lists the patents as scheduled for expiration on December 26, 2016, and August 29, 2017, respectively.[1]

Eletriptan is believed to reduce swelling of the blood vessels surrounding the brain. This swelling is associated with the head pain of a migraine attack. Eletriptan blocks the release of substances from nerve endings that cause more pain and other symptoms like nausea, and sensitivity to light and sound. It is thought that these actions contribute to relief of symptoms by eletriptan.
Eletriptan is a serotonin agonist. Specifically, it is a selective 5-hydroxytryptamine 1B/1D (5-HT1B) receptor agonist.
Eletriptan binds with high affinity to the 5-HT1B, 1D, 1F] receptors.
It has a modest affinity to the 5-HT[1A, 1E, 2B, 7] receptors.
And little to no affinity at the 5-HT[2A, 2C, 3, 4, 5A, 6] receptors.
Eletriptan has no significant affinity or pharmacological activity at adrenergic alpha1, alpha2, or beta; dopaminergic D1 or D2; muscarinic; or opioid receptors. Eletriptan could be efficiently co-administrated with nitric oxide synthase (NOS’s) inhibitors for the treatment of NOS-dependent diseases (US patent US 2007/0254940)
Two theories have been proposed to explain the efficacy of 5-HT receptor agonists in migraine. One theory suggests that activation of 5-HT1 receptors located on intracranial blood vessels, including those on the arteriovenous anastomoses, leads to vasoconstriction, which is correlated with the relief of migraine headache. The other hypothesis suggests that activation of 5-HT1 receptors on sensory nerve endings in the trigeminal system results in the inhibition of pro-inflammatory neuropeptide release.

Common side effects include hypertensiontachycardia, headache, dizzyness, and symptoms similar to angina pectoris. Severe allergic reactions are rare.[4]

Eletriptan is contraindicated in patients with various diseases of the heart and circulatory system, such as angina pectoris, severe hypertension, and heart failure, as well as in patients that have had a stroke or heart attack. It is also contraindicated in severe renal orhepatic impairment.[4]

The drug has a relatively low potential for interactions. Notably, it is unlikely to interact to a relevant extent with beta blockerstricyclic antidepressants and SSRI type antidepressants. Strong inhibitors of the liver enzyme CYP3A4, such as erythromycin and ketoconazole, significantly increase blood plasma concentrations and half life of eletriptan. Ergot alkaloids add to the drug’s hypertensive effect.[4]

  • Merck Index: 3-[[(2R)-1-Methyl-2-pyrrolidinyl]methyl]-5-[2-(phenylsulfonyl)ethyl]-1H-indole
  • 5-[2-(benzenesulfonyl)ethyl]-3-(1-methylpyrrolidin-2(R)-ylmethyl)-1H-indole
  • (R)-5-[2-(phenylsulfonyl)ethyl]-3-[(1-methyl-2-pyrrolidinyl)methyl]-1H-indole

  1.  FDA AccessData entry for Eletriptan Hydrobromide, accessed March 10, 2010.
  2.  U.S. Patent no. 5545644, John E. Macor & Martin J. Wythes, Indole Derivatives, August 13, 1996.
  3.  U.S. Patent no. 6110940, Valerie Denise Harding, et al.Salts of an anti-migraine indole derivative, August 29, 2000.
  4. Jasek, W, ed. (2007). Austria-Codex (in German) (62nd ed.). Vienna: Österreichischer Apothekerverlag. pp. 6984–8. ISBN 978-3-85200-181-4.

3-{[(2R)-1-methylpyrrolidin-2-yl]methyl}-5-[2-(phenylsulfonyl)ethyl]-1H-indole or Eletriptan, currently available in the market as a hydrobromide salt, is an agonist of the 5-hydroxytryptamine (5-HT1B/1D) receptor and it is used for treating migraine.
Various processes of synthesis of such molecule are known, but the one generally used is the synthesis shown in the diagram of FIG. 1, which provides for a Heck reaction (step 4 or 4b) between 5-bromo-3-{[(2R)-1-methylpyrrolidin-2-yl]methyl}-1H-indole and phenyl vinyl sulfone to obtain the 1-(3-{[(2R)-1-methylpyrrolidin-2-yl]methyl}-5-[(E)-2-(phenylsulfonyl)ethenyl]-1H-indole-1-yl)ethanone intermediate.
This reaction uses a palladium-based catalyst which is very sensitive to the impurities present in the reaction environment. It is thus essential that the 5-bromo-3{[(2R)-1-methylpyrrolidin-2-yl]methyl}-1H-indole intermediate be thoroughly purified before being reacted with phenyl vinyl sulfone.
In prior art documents (EP 0 592 438, U.S. Pat. No. 5,545,644 and U.S. Pat. No. 6,100,291) purification of the 5-bromo-3-{[(2R)-1-methylpyrrolidin-2-yl]methyl}-1H-indole intermediate is performed by means of chromatographic column, a process almost exclusively implementable in a laboratory or at a high cost in any case with long processing times alongside being ecologically unadvisable due to the large amount of solvents used.
Furthermore, it is known that the crystallisation of 5-bromo-3-{[(2R)-1-methylpyrrolidin-2-yl]methyl}-1H-indole intermediate (WO 2008/150500 and U.S. Pat. No. 5,545,644) provides a purified intermediate with assay not exceeding 98% (established through the HPLC analysis).
US5545644A1 describes a synthetic process for Eletriptan. 5-Bromoindole was acylated at the 3-position by reacting the magnesium salt of 5-bromoindole. This process results in a dimer formation in the final Pd/C reduction stage which poses problems in purification which further leads to decrease in yields.
US7288662B2 discloses methods to circumvent the problems associated with dimer formation described in US5545644A1. The indole-nitrogen was acetylated prior to hydrogenation and later deacetylated to give pure Eletriptan. However, this process introduced two additional steps into the synthesis which is time consuming and subsequently costly. WO2005/103035A1 discloses Eletriptan synthesis by a Fischer Indole process. However, enantiomeric purity of the finished product depends on the purity of an acetal intermediate which might require asymmetric synthesis or optical resolution. Eletriptan obtained in the reported procedure had about 94% enantiomeric excess.
Eletriptan and intermediates thereof, including 5-bromo-3-[(i?)-l-methyl- pyrrolidin-2-ylmethyl]-lH-indole (“BIP”) are described in US 5,545,644. Also disclosed is the synthesis of ELT, which is illustrated by the following scheme:
Figure imgf000003_0001
In the described process, intermediate I, BIP, is obtained by reacting intermediate II with lithium aluminium hydride (“LAH”). LAH spontaneously reacts with water, including atmospheric humidity, and the pure material is pyrophoric. The LAH is known as very unstable, and air-exposed samples are almost always contaminated with aluminium metal and or a mixture of lithium hydroxide and aluminium hydroxide, thus affecting the reactivity of the LAH powder. This leads to the use of a large excess of reagent in order to obtain moderate conversion. Furthermore, the described process requires heating to reflux for a long period of time (39 hours in total, according to example 29 in patent US 5,545,644) followed by a time consuming recovery process. The recovery process consists of diluting of the reaction mixture with ethyl acetate, filtering through cellulose filtration bar, as described in patent US 5,545,644 example 27, and purifying the obtained oily like residue by silica gel chromatography, wherein, dichloromethane, ethanol and concentrated aqueous ammonia are used as a mobile phase. This process provides BIP, which is then converted to ELT.
Anhydrous alpha-and beta-hydrobromide salt forms of eietriptan are disclosed in WO-A-96/06842.
Figure imgf000003_0001
5-Bromoindole under Heck reaction conditions is coupled with phenyl vinyl sulfone followed by acylation with Cbz-Proline acid chloride to obtain a compound of Formula IV which on reduction in presence of a hydride agent provide Eletriptan.
1H NMR CDCI3 δ= 8.10 (bs, NH), 7.92-7.99 5 (m, 2H), 7.62-7.69 (m, 1H), 7.53-7.61 (m, 2H), 7.30 (s, 1H), 7.22 (d, 1H), 7.03 (s, 1H), 6.93 (dd, 1 H), 3.38-3.45 (m, 2H), 3.09-3.21 (m, 4H), 2.45-2.55 (m, 2H), 2.45 (s, 3H), 2.20-2.30 (m, 1H), 1.50-1.90 (m, 4H).
ESI Mass (M+H) 383.69

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

Marcus BaumannEmail of corresponding author, Ian R. BaxendaleEmail of corresponding author, Steven V. LeyEmail of corresponding author and Nikzad NikbinEmail of corresponding author
Innovative Technology Centre, Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW Cambridge, UK
Email of corresponding author Corresponding author email
Editor-in-Chief: J. Clayden
Beilstein J. Org. Chem. 2011, 7, 442–495.
Eletriptan (87, Relpax) is yet another indole-containing antimigraine drug. A process route for the synthesis of eletriptan published by Pfizer starts from a preformed bromo-indole 88 [28] (Scheme 20). In order to perform the acylation of the indole ring on larger scale, ethylmagnesium bromide and the corresponding acid chloride 89 are added concurrently from two different sides of the reactor to stop these reagents reacting with each other. This method of adding the reagents circumvents the necessity to isolate the magnesium salt of the indole and increases the yield from 50 to 82%. The carbonyl group of the proline side chain is then reduced simultaneously with the complete reduction of the Cbz-group to a methyl group with lithium aluminium hydride. Finally, the sulfonate side chain is introduced via a Heck-type coupling similar to that of naratriptan (Scheme 15), followed by hydrogenation of the double bond to afford eletriptan (Scheme 20).
A rather ingenious Mitsunobu coupling reaction has been used to create a highly functionalised substrate 96 for an intramolecular Heck reaction resulting in a very short and succinct synthesis of eletriptan and related analogues 97 [29] (Scheme 21).
Scheme 21: Heck coupling for the indole system in eletriptan.
Interestingly, it was found that the most obvious approach, the direct Fischer indole synthesis, to prepare the core of eletriptan as shown in Scheme 22 is not successful [30]. This is believed to be due to the instability of the phenyl hydrazine species 98 under the relatively harsh reaction conditions required to promote the cyclisation.
Scheme 22: Attempted Fischer indole synthesis of elatriptan.
However, this problem could be avoided by using an acid-labile oxalate protected hydrazine 104 as depicted in Scheme 23. The yield of this step can be further improved up to 84% if the corresponding calcium oxalate is used.
Scheme 23: Successful Fischer indole synthesis for eletriptan.
  • Macor, J. E.; Wythes, M. J. Indole Derivatives. U.S. Patent 5,545,644, Aug 13, 1996.
  • Perkins, J. F. Process for the Preparation of 3-Acylindoles. Eur. Patent 1088817A2, April 4, 2001.
  • Ashcroft, C. P. Modified Fischer Indole Synthesis for Eletriptan. WO Patent 2005/103035, Nov 3, 2005.
  • Bischler, A. Chem. Ber. 1892, 25, 2860–2879. doi:10.1002/cber.189202502123

Synthesis of compounds related to the anti-migraine drug eletriptan hydrobromide

Suri Babu Madasu1,2, Nagaji Ambabhai Vekariya1Email of corresponding author, M. N. V. D. Hari Kiran1, Badarinadh Gupta1, Aminul Islam1, Paul S. Douglas2 and Korupolu Raghu Babu2
1Chemical Research and Development, Aurobindo Pharma Ltd., Survey No. 71 & 72, Indrakaran (V), Sangareddy (M), Medak Dist-502329, Andhra Pradesh, India
2Engineering Chemistry Department, AU College of Engineering, Andhra University, Visakhapatnam-530003, Andhra Pradesh, India
Email of corresponding author Corresponding author email
Associate Editor: J. Aube
Synthetic route of eletriptan hydrobromide. Reagents and conditions: (i) Acetic anhydride, TEA, DMF, 90–100 °C; (ii) palladium acetate, tri-(o-tolyl)phosphine, TEA, DMF, 90–100 °C; (iii) methanol, K2CO3, acetonitrile, H2O, 5–10 °C; (iv) palladium on carbon, acetone, H2O, aqueous hydrobromic acid, IPA, 25–30 °C.
Org. Process Res. Dev., 2011, 15 (1), pp 98–103
DOI: 10.1021/op100251q
aReagents and conditions: (a) EtMgBr, Et2O. (b) 3, DCM, 50% from 1. (c) LiAlH4, THF, 72%. (d) Ac2O, TEA, DMF. (e) Phenyl vinyl sulfone (PVS), Pd(OAc)2, P(°Tol)3, TEA, DMF, 80% from 5. (f) H2, Pd/C, MeSO3H, acetone, 95%. (g) K2CO3, MeOH, 92%. (h) HBr, acetone 73%.
1H NMR (CDCl3): δ = 1.51−1.85 (m, 4H), 2.22−2.28 (m, 1H), 2.43−2.49 (m, 4H), 2.56−2.62 (m, 1H), 3.11−3.18 (m, 4H), 3.42−3.46 (m, 2H), 6.91−6.93 (s, 1H), 7.01 (s, 1H), 7.23−7.27 (d, 1H), 7.31 (s, 1H), 7.56−7.60 (m, 2H), 7.65−7.68 (m, 1H), 7.96−7.98 (d, 2H), 8.14 (s, 1H); LC/MS: Rt = 2.30 min; m/z 383 [MH]+
‘H-NMR (400MHz, ds-DMSO): delta = 10.90 (1H, d, J=2.2Hz), 9.35 (1 H, br s), 7.95 (2H, d, J=7.5Hz), 7.76 (1 H, t, J=7.5Hz), 7.66 (2H, t, J=7.5Hz), 7.38 (1 H, s), 7.24 (1 H, d, J=8.3Hz), 7.23 (1 H, d, J=2.2Hz), 6.92 (1 H, dd, J=8.3,1.4Hz), 3.63 (2H, m), 3.58 (2H, br m), 3.24 (1 H, m), 3.06 (1 H, m), 2.95 (2H, m), 2.86 (1 H, m), 2.83 (3H, s), 2.00 (1 H, m), 1.90 (2H, m), 1.70 (1 H, m).
Found: C, 54.85; H, 6.03; N, 5.76. C22H29N203SBr requires C, 54.87; H, 6.08; N, 5.82%.


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