SD-809 (deutetrabenazine)

(3RS,11Brs)-9,10-di((2H3)methoxy)-3-(2-methylpropyl)-1,3,4,6,7,11b-hexahydro-2H-benzo(a)quinolizin-2-one

2H-Benzo(a)quinolizin-2-one, 1,3,4,6,7,11b-hexahydro-9,10-di(methoxy-d3)-3-(2-methylpropyl)-, (3R,11bR)-rel-

2H-Benzo(a)quinolizin-2-one, 1,3,4,6,7,11b-hexahydro-9,10-di(methoxy-d3)-3-(2-methylpropyl)-, (3R,11bR)-rel-

class=”summary-title extra-long”>(3RS,11Brs)-9,10-di((2H3)methoxy)-3-(2-methylpropyl)-1,3,4,6,7,11b-hexahydro-2H-benzo(a)quinolizin-2-one
Treatment of Chorea Associated with Huntington Disease

SD-809 was granted Orphan Drug Designation for the treatment of HD by the FDA in November 2014 and became part of Teva’s CNS portfolio with the acquisition of Auspex Pharmaceuticals in May 2015.

Teva announced that the New Drug Application (NDA) for SD-809 (deutetrabenazine) has been accepted by the U.S. Food and Drug Administration (FDA) for the treatment of chorea associated with Huntington disease (HD), a rare and fatal neurodegenerative disorder caused by the progressive breakdown of nerve cells in the brain that affects about five to seven people per 100,000 in western countries, according to the World Health Organization.

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Patent for preparing tetrabenazine

http://www.google.com/patents/WO2012081031A1?cl=en

Chemically tetrabenazine is cis rac -1, 3, 4, 6, 7, 1 lb-hexahydro-9, 10-dimethoxy-3-(2- methylpropyl)-2Hbenzo[a]quinolizin-2-one and it is represented by compound of structural formula I.

Formula 1

The proprietary name of tetrabenazine is Xenazine and is marketed by Biovail Americas. Xenazine is indicated for the treatment of chorea associated with Huntington’s disease. U.S. patent no. 2,830,993 discloses a process for the preparation of tetrabenazine compound of structural formula I wherein 1 -carbethoxymethyl-6, 7-dimethoxy-l , 2, 3, 4- tetrahydroisoquinoline compound of structural formula IV is being reacted with mono- isobutylmalonic acid dimethyl ester compound of structural formula V and paraformaldehyde in methanol solvent to get l-carbethoxymethyl-2 (2, 2-dicarbomethoxy-4-methyl-n-pentyl)-6, 7- dimethoxy-1, 2, 3, 4-tetrahydroisoquinoline compound of structural formula VI. The 1- carbethoxymethyl-2(2,2-dicarbomethoxy-4-methyl-n-pentyl)-6,7-dimethoxy-l ,2,3,4- tetrahydroisoquinoline compound of structural formula VI is subjected to Dieckmann cyclization , hydrolysis and decarboxylation to get tetrabenazine compound of structural formula I, which is recrystallized from di-isopropyl ether solvent.

Formula I

Scheme I

U. S. patent no. 4,678,792 discloses a process for the preparation of 6, 7-dimethoxy-3, 4- dihydroisoquinoline compound of structural formula VII wherein 2-(3, 4-dimethoxyphenyl)- ethylamine compound of structural formula II is being reacted with chloral hydrate at 120°C to get N-formyl-2-(3, 4-dimethoxyphenyl)-ethylamine compound of structural formula III. The N- formyl-2-(3, 4-dimethoxyphenyl)-ethylamine compound of structural formula III is further reacted with polyphosphoric acid to get 6, 7-dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII. The 6, 7-dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII is being used as an intermediate for the preparation of tetrabenazine compound of structural formula I.

Formula III

Formula II

Polyphosphoric acid

Formula VII

Scheme II

Bull. Korean Chem. Soc. 2002 Volume (23). No. l , page no. 149 discloses N-formylation of various amines and alcohols with formic acid in toluene.

U.S. patent publication no. 2010/0130480 discloses a process for the preparation of 6, 7- dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII by reacting 2-(3, 4- dimethoxyphenyl)-ethylamine compound of structural formula II with hexamethylenetetramine in presence of acetic acid or trifluoroacetic acid.

Hexamethylenetetramine

Formula II Formula VII

U.S. patent publication no. 2008/0167337 discloses a process for the preparation of tetrabenazine compound of structural formula I wherein 6, 7-dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII is reacted with 3-dimethylaminomethyl-5-methyl-hexan-2-one methiodide compound of structural formula VIII to get crude tetrabenazine compound. The crude tetrabenazine compound was purified by employing flash column chromatography technique and

Formula VIII Formula I

The prior-art processes for preparing N-formyl-2-(3, 4-dimethoxyphenyl)-ethylamine compound of structural formula III produces below mentioned compound of structural formula XVII, XVIII, XIX, XX, XXI and XXII as a by-product of the reaction due to the demethylation and formylation of resulting hydroxy compounds.

Formula XX Formula XXI Formula XXII

The compounds of structural formula XVII, XVIII, XIX, XX, XXI and XXII are being carry- forwarded into the further steps of reactions of preparing tetrabenazine compound of structural formula I and therefore there is a need in the art to develop an improved process of preparing 6, 7-dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII, which obviates the prior-art problems. Accordingly there is provided a process of preparing tetrabenazine compound of structural formula I wherein 6, 7-dimethoxy-3, 4-dihydroisoquinoline compound of structural formula VII is being formed without the formation of above mentioned compounds of structural formula XVII, XVIII, XIX, XX, XXI and XXII.

EXAMPLE: PROCESS FOR THE PREPARATION OF SUBSTANTIAL PURE CRYSTALLINE FORM A OF TETRABENAZINE

Stage A: Process for the preparation of 6, 7-dimethoxy-3, 4-dihydroisoquinoIine

Step 1 : Process for the preparation of N-formyl-2-(3, 4-dimethoxyphenyl)-ethylamine

A solution of 2-(3, 4-dimethoxyphenyl)-ethylamine (500gm) in toluene (2000ml) was added formic acid (150gm) at 25°C, the resulting reaction mixture was diluted with toluene (500ml) and heated up to 45°C. The reaction mixture was maintained at 40-45°C for 5 hours and then the resulting reaction mixture was concentrated under reduced pressure at 50°C to get the title compound

Yield: 570gm

Purity: 99.98% (By HPLC)

Step 2: Process for the preparation of 6, 7-dimethoxy-3, 4-dihydroisoquinoline

A solution of N-formyl-2-(3, 4-dimethoxyphenyl)-ethylamine (250gm) obtained from step 1 in toluene (500ml) and polyphosphoric acid (50gm) was heated at 110°C for 5 hours. The resulting reaction mixture was cooled to 50°C, quenched with water (500ml) and pH of the resulting solution was adjusted to about 8.3 with aqueous solution of sodium hydroxide [sodium hydroxide (690gm) + water (690ml)]. The resulting reaction mass was extracted by ethyl acetate (2 1250ml), dried over anhydrous sodium sulfate (50gm) and concentrated under reduced pressure to get 6, 7-dimethoxy-3, 4-dihydroisoquinoline (190gm).

Yield: 215gm

Purity: 99.67% (By HPLC)

Stage B: Process for the preparation of 3-((dimethylamino) methyi)-5-methylhexan-2-one methiodide

Step 1 : Process for the preparation of 3-((dimethylamino) methyl)-5-methylhexan-2-one Dimethylamine hydrochloride (180gm) and paraformaldehyde (lOOgm) were added to a solution of 5-methylhexan-2-one (900ml) in methanol (1600ml). The resulting reaction mass was heated at reflux for 12 hours, and then the pH was adjusted to about 8.75 with aqueous solution of sodium hydroxide [sodium hydroxide(90gm) + water (900ml)] at 25 °C. The resulting reaction solution was extracted by toluene (2x1234ml). The organic layer was dried over anhydrous sodium sulfate (50gm) and concentrated under reduced pressure to get title compound.

Yield: 900gm

Purity: 99.80% (By HPLC)

Step 2: Process for the preparation of 3-((dimethylamino) methyl)-5-methylhexan-2-one methiodide

Methyl iodide (323gm) was added dropwise to a solution of 3-((dimethylamino) methyl)-5- methylhexan-2-one (195gm) obtained from step 1 , in ethyl acetate (1650ml) at 25-30°C in 30 minutes. The resulting reaction mixture was stirred at 25 °C for 12 hours and then the resulting solids were filtered, washed with water (200ml) and suck-dried to get wet compound (400gm). The wet compound was slurried with water (1000ml) at 25°C for 1 hour and then it was again filtered, washed with water (200ml) and dried at 45-50°C to get title compound

Yield: 300gm

Purity: 99.86% (By HPLC)

Stage C: Preparation of substantial pure crystalline form A of Tetrabenazine

3-((Dimethylamino) methyl)-5-methylhexan-2-one methiodide (80gm) was added to the solution of 6, 7-dimethoxy-3, 4-dihydroisoquinoline (40gm) in isopropanol (288ml) at 25°C and the resulting reaction mass was heated at 40-45°C for 15 hours. The resulting insoluble material was filtered, washed with isopropanol (80ml) and filtrate was concentrated under reduced pressure up to the 150ml reaction volume. The reaction solution was diluted with methylene dichloride (1200ml) and water (1000ml) and pH was adjusted to 8.5 with sodium hydroxide solution [10%, 100ml]. The organic layer was separated, washed with water (3 x 1000ml) and concentrated under reduced pressure to obtain residue. The residue was dissolved in methanol (300ml) at 50°C, and resulting solution was treated with an activated carbon (20gm) at 50-60°C for 30minutes and then it was filtered and filtrate was further stirred at 20-25°C for 2 hours. The resulting solids were filtered, washed with methanol (150ml), dried at 50-55°C for 8 hours. The resulting solids were milled, sifted through 40 mesh sieve and micronized.

Yield: 65gm

Purity: 99.96% (By HPLC)

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PAPER

A concise synthesis of tetrabenazine and dihydrotetrabenazine is described. The key feature of this synthesis is the intramolecular aza-Prins-type cyclization of an amino allylsilane via oxidative C–H activation.

http://www.hgxb.com.cn/EN/abstract/abstract12047.shtml

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PAPER

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3126153/

The TBZ (4) for these reactions was prepared by reacting 3,4-dihydro-6,7-dimethoxyisoquinoline (3) and the Mannich base (2) as shown in Scheme 1.¹⁴ The α,β-unsaturated TBZ (5), which was the original substrate, was obtained by further treatment with chloranil in refluxing benzene.

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http://www.google.ga/patents/WO2008154243A1?cl=en

Example 10 Removal The Boc Protecting Group From First Intermediate 12 And Amino Cyclization Provide (+)-Tetrabenazine XVII

[0063] First intermediate 12 (1.0 eq) was dissolved in 10% Me₂S- dichloromethane to provide an 82 mM solution. The solution was cooled to 0 ⁰C and triisopropylsilane (1.1 eq.) followed by TFA (precooled to 0 ⁰C) was added to the reaction mixture to provide a final concentration of 41 mM. The reaction mixture was permitted to stir at 0 ⁰C for 1 h. Following the allotted time the reaction mixture was quenched at 0 ⁰C by the addition of saturated aqueous potassium carbonate solution and concentrated under reduced pressure to remove the majority of the dimethylsulfide. The mixture was extracted with five portions of dichloromethane, and the combined organic extracts were washed with brine, dried (MgSO₄), filtered and concentrated under reduced pressure to provide the crude product as a yellow solid. The crude product was recrystallized from 3.5% dimethoxyethane in hexanes. The resulting colorless crystals were washed with hexanes to provide pure (+)- tetrabenazine (XVII) 46%: mp 126.0 ⁰C (3.5% DME-hexanes) (a crystal polymorph was observed at 116 ⁰C); [α]²⁶ _D +37.2 (c 0.41, CH₂Cl₂); ¹H NMR (CD₂Cl₂) δ 0.89 (apparent t, J = 7.2 Hz, 6H), 0.98 (ddd, J = 12, 6.0, 4.0 Hz, IH), 1.59-1.68 (m, IH), 1.74 (ddd, J = 12, 5.9, 5.7 Hz, IH), 2.32 (apparent t, J = 11.7 Hz, IH), 2.46 (apparent t, J = 12.3 Hz, IH), 2.55 (ddd, J = 12, 10.0, 3.8 Hz, IH), 2.65-2.73 (m, 2H), 2.83 (dd, J = 5.5, 2.8Hz, IH), 2.97-3.07 (m, IH), 3.07-3.14 (m, IH), 3.25 (dd, J =9.7, 6.3 Hz, IH), 3.47 (apparent d, J = 12Hz, IH), 3.75 (s, 3H), 3.77 (s, 3H), 6.55 (s, IH), 6.60 (s, IH) ¹³C NMR (CD₂Cl₂) δ 21.98, 23.02, 25.51, 29.46, 35.16, 47.47, 47.63, 50.47, 55.87, 56.01, 61.47, 62.46, 108.46, 111.72, 126.37, 128.96, 147.65, 147.98, 209.72; HRMS-(ESI+) calcd for (C₁₉H₂₇NO₃ + H) ([M+H]⁺ 318.2069, found 318.2082.

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NMR PREDICT

Watch out will be updated……………….

Rob Koremans, MD, President and CEO of Global Specialty Medicines at Teva.

Michael Hayden, M.D., Ph.D., President of Global R&D and Chief Scientific Officer at Teva

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