USRE43844E1 - Process for preparing isomers of salbutamol - Google Patents

Process for preparing isomers of salbutamol Download PDF

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Publication number
USRE43844E1
USRE43844E1 US12/026,790 US2679003A USRE43844E US RE43844 E1 USRE43844 E1 US RE43844E1 US 2679003 A US2679003 A US 2679003A US RE43844 E USRE43844 E US RE43844E
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Prior art keywords
optically
salbutamol
pure
precursor
tartaric acid
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Yusuf Khwaja Hamied
Rajendra Narayanrao Kankan
Dharmaraj Ramachandra Rao
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Cipla Ltd
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Cipla Ltd
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Priority to US12/026,790 priority Critical patent/USRE43844E1/en
Priority to US12/402,752 priority patent/USRE43984E1/en
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C213/00—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
    • C07C213/10—Separation; Purification; Stabilisation; Use of additives
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C227/00—Preparation of compounds containing amino and carboxyl groups bound to the same carbon skeleton
    • C07C227/30—Preparation of optical isomers
    • C07C227/34—Preparation of optical isomers by separation of optical isomers
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07B—GENERAL METHODS OF ORGANIC CHEMISTRY; APPARATUS THEREFOR
    • C07B2200/00—Indexing scheme relating to specific properties of organic compounds
    • C07B2200/07—Optical isomers

Definitions

  • This invention relates to an improved method of making optically pure (R) and (S) salbutamol, also known as (R) and (S) albuterol.
  • the chemical name for salbutamol is ⁇ -[[(1,1-dimethyl-ethyl)amino]methyl]-4-hydroxy-1,3-benzenedimethanol.
  • the (R) isomer of salbutamol (which is laevorotatory, denoted ( ⁇ ) or 1) is known to be very much more potent therapeutically than the dextrorotatory (S) isomer.
  • the R isomers of salbutamol is also known as levalbuterol.
  • One method of preparing the (R) and (S) isomers of salbutamol in optically pure form is disclosed in U.S. Pat. No. 5,545,745. In this method, either of two precursor compounds for salbutamol is resolved using a substituted tartaric acid derivative. Specifically the resolving compound used in U.S. Pat. No.
  • 5,545,745 is chosen from ( ⁇ )-di-toluoyl-L-tartaric acid, (+)-di-toluoyl-D-tartaric acid, ( ⁇ )-di-benzoyl-L-tartaric acid and (+)-di-benzoyl-D-tartaric acid.
  • Another reference (Hartley et al, Journal of Medicinal Chemistry, 1971, Vol 14, No 9, pp 895–896) describes much the same thing as U.S. Pat. No. 5,545,745: the resolution is performed with either (+) or ( ⁇ ) di-para-toluoyl tartaric acid.
  • WO 99/42460 describes the resolution of a new ketal derivative of salbutamol (specifically 2-(N-t-butylamino)-1-(+2,2-dimethyl-1,2-benzodioxin-6-yl) ethanol).
  • the resolution is again performed with a chiral tartaric acid derivative, such as (+) or ( ⁇ ) di-para-toluoyl tartaric acid or (+) or ( ⁇ ) di-O-benzoyl tartaric acid.
  • Enantiomers of salbutamol can be produced if desired, via a complicated, multi-stage process involving resolution of the ketal derivative.
  • a process for making optically pure (R) and/or (S) salbutamol or pharmaceutically acceptable salts thereof comprises obtaining the (E) (R) or (S) isomer of either salbutamol or a salbutamol precursor in substantially optically pure form by resolving a racemic or optically impure mixture of enantiomers of salbutamol or of said precursor with either (L) or (D) tartaric acid, and where necessary converting said isomer of said precursor into either (R) or (S) salbutamol respectively; then optionally converting said optically pure (R) and/or (S) salbutamol into a pharmaceutically acceptable salt.
  • An advantage of the present method is its general applicability to different intermediates of salbutamol. It also enables chirally pure product to be obtained in a good yield.
  • the compound 4-benzyl albuterol (i) ( ⁇ -[[(1,1- dimethylethyl) amino]methyl]-4-(phenylmethoxy)-1,3-benzenedimethanol) is used as the salbutamol precursor.
  • a racemic or optically impure mixture of the compound is resolved to give the (R) and (S) isomers before conversion to the desired isomer of salbutamol takes place.
  • 4-benzyl albuterol is readily available commercially, for example from Cipla Limited.
  • the precursor 4-benzyl albuterol is typically prepared, for example, from the ester intermediate methyl-5-[2-[(1,1-dimethylethyl)amino]-1-hydroxyethyl]-2-(phenylmethoxy)-benzoate (II).
  • This compound (II) can also, if desired, serve as the “salbutamol precursor” which is itself resolved into its (R) and (S) isomers.
  • the invention provides a process for making optically pure (R) and/or (S) salbutamol or pharmaceutically acceptable salts thereof, which process comprises resolving racemic salbutamol, or an optically impure mixture of enantiomers of salbutamol, with either (L) or (D) tartaric acid, and optionally converting said optically pure (R) and/or (S) salbutamol into a pharmaceutically acceptable salt thereof.
  • the present invention thus provides several ways of producing (R) and/or (S) salbutamol: by resolution at the final stage, for example on racemic salbutamol, or by resolution at an intermediate stage—for example, by resolution of the alcohol intermediate 4-benzyl albuterol or by resolution of the ester intermediate (II) methyl-5-[2-[(1,1-dimethylethyl)amino]-1-hydroxyethyl]-2-(phenylmethoxy)-benzoate.
  • optically pure we mean an enantiomeric excess (e.e.) (which is a measure well known in the art) of about 95% or more.
  • optical impure refers to mixtures of enantiomers where the e.e. value is below about 95%, but where the mixture is not exactly racemic.
  • step (a) a suspension of racemic 4-benzyl albuterol is mixed with a solution of either (L) or (D) tartaric acid (as desired) in an organic solvent.
  • a solvent such as methanol, ethanol, isopropanol, acetone or ethyl acetate or a mixture of two or more thereof.
  • the mixture is then chilled to give crystals of the (L) or (D) tartrate salt of 4-benzyl albuterol, which are then separated and purified.
  • the yield of the chosen tartrate salt is generally above 30%, with an e.e. value of around 99%.
  • step (b) the optically pure isomer of either (R) or (S) 4-benzyl albuterol is obtained from a solution (typically aqueous) of the corresponding tartrate salt.
  • a solution typically aqueous
  • Other bases that can be used include potassium hydroxide, potassium carbonate, aqueous ammonia and sodium or potassium bicarbonate. Prolonged stirring of the alkali/salt mixture is usually necessary to precipitate the free base completely from the solution.
  • the yield of the (R) or (S) isomer of 4-benzyl albuterol is generally 40% or more based on the quantity of racemic starting material. The e.e. value remains high, typically at 99% or more.
  • step (c) (R) or (S) 4-benzyl albuterol free base is de-benzylated in order to give (R) or (S) salbutamol.
  • This is preferably carried out by suspending the isomer of 4-benzyl albuterol in an organic solvent such as ethanol, adding a palladium on carbon catalyst and hydrogenating the suspension under pressure in a hydrogenator. The resulting optically pure isomer of salbutamol is then filtered off.
  • a pharmaceutically acceptable salt of the free base can be obtained by the addition of an acid (for example, dilute sulphuric or hydrochloric acid) in the usual way (see step (d)).
  • the resolving-step can if desired be carried out earlier in the process, for example, by resolving the ester intermediate (II).
  • (L) or (D) tartaric acid may be used for the resolution, although preferably (L) tartaric acid is employed so as to give the (R) form of the ester. This preferred route is shown in Scheme B below.
  • the reduction of the (R) isomer of the ester to (R) 4-benzyl albuterol can, for example, be carried out using lithium aluminium hydride, although any suitable reducing agent can be used.
  • the resolution is typically carried out in the same way as that described for 4-benzyl albuterol.
  • salbutamol precursors which can be usefully employed in the process of the invention include derivatives of 4-benzyl albuterol in which the ring of the benzyl group is variously substituted.
  • the benzyl group may, for example, be substituted with one or more halogen atoms (such as, chlorine, fluorine or bromine) or one or more alkoxy groups such as methoxy.
  • halogen atoms such as, chlorine, fluorine or bromine
  • alkoxy groups such as methoxy.
  • Other similar substitutions which have the purpose of protecting the phenolic group of the salbutamol precursor may also be used, as will be clear to those skilled in the art.
  • Racemic 4-benzyl albuterol (100 g, 0.30 mole) is suspended in methanol (500 ml) and heated to reflux. A solution of L-tartaric acid (50 g, 0.33 mole) in methanol (150) ml is introduced in about 15 minutes. The clear solution is then chilled to 0 to 5° C. and the crystals are filtered. The wet crystals are taken up in isopropanol (300 ml) and heated to reflux, cooled to room temperature and filtered to obtain the title compound as a white solid (65 g, 45% yield, 99% ee)
  • Example 2 The product from Example 1 (65 g, 0.13 mole) is dissolved in water (650 ml) and filtered over celite to remove insolubles. The clear filtrate is cooled to 10° C. and a solution of 10% sodium hydroxide (80 ml) is slowly introduced. The sticky solid precipitated becomes free on prolonged stirring for 4 hours. The solid is filtered, washed with water and dried to obtain the title compound as a white solid (40 g, 40% yield based on amount of racemic compound, 99% e.e.).
  • R-4-Benzyl Albuterol (40 g, 0.12 mole) is suspended in 500 ml ethanol, 5% palladium on carbon (2 g) is added and shaken in a 1 lit. Parr Hydrogenator at 30 psi for 2 hours. The catalyst is filtered off and the clear filtrate is cooled to 15° C. under stirring. Sulphuric acid (4.9 g, 0.05 mole) is introduced dropwise and the resulting mixture is stirred for 1 hour and filtered. The solids are washed with ethanol (20 ml) and dried at 45 to 50° C. in a vacuum oven to give pure R-salbutamol sulphate (30 g, 86% yield).
  • Racemic ester (100 g, 0.28 mole) is suspended in methanol (600 ml) and heated to reflux. A solution of L-tartaric acid (50 g, 0.33 mole) in methanol (150 ml) is introduced in about 30 minutes. The clear solution is then chilled to 0 to 5° C. and the crystals are filtered. The wet crystals are taken up in ethanol (400 ml) and heated to reflux, cooled to room temperature and filtered to obtain the R( ⁇ ) ester-L-tartrate as a white solid. This is then dissolved in water (500 ml) and filtered over celite to remove insolubles. The clear filtrate is then cooled to 0 to 5° C.
  • R( ⁇ )-ester 35.8 g, 0.1 mole is suspended in dry tetrahydrofuran (250 ml) and cooled to 0 to 5° C.
  • Lithium aluminium hydride (4 g; 0.33 mole) is introduced slowly and the reaction mass is further stirred for 3 hours.
  • a 15% sodium sulphate (20 ml) is then introduced and the precipitate is then filtered off.
  • the clear filtrate is then concentrated, taken up in ethyl acetate (100 ml), cooled to 5° C. and filtered to obtain the title compound (30 g; 91%; 99% e.e.).
  • Racemic 4-benzyl albuterol (100 g, 0.30 mole) is suspended in methanol (500 ml) and heated to reflux. A solution of (D-)tartaric acid in methanol (150 ml) is introduced in about 15 minutes. The clear solution is then chilled to 0 to 5° C. and the crystals filtered. The wet crystals are taken up in isopropanol (300 ml) and heated to reflux, cooled to room temperature and filtered to obtain the title compound as a white solid (65 g; 45%; 99% e.e.).
  • Example 6 The product from Example 6 (65 g; 0.13 mol) is dissolved in water (650 ml) and filtered over celite to remove insolubles. The clear filtrate is cooled to 10° C. and a solution of 10% sodium hydroxide (80 ml) is slowly introduced. The solids thus precipitated are filtered, washed with water and dried to obtain the title compound as a white solid (40 g; 40% based on racemic compound, 99% e.e.).
  • Salbutamol 100 g; 0.41 mole is dissolved in a 1:1 mixture of ethyl acetate and methanol (500 ml) at about 70° C.
  • L(+)tartaric acid 66 g; 0.44 mole
  • the contents are maintained at 70° C. for 2 hours.
  • the tatrate salt crystallises. This is filtered and recrystallised from ethanol to give 52 g of the pure R ( ⁇ ) salbutamol tartrate.
  • the salt is then suspended in methanol (200 ml) and a solution of sodium methoxide (15 g; 0.27 mole) in methanol is introduced.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Preparation Of Compounds By Using Micro-Organisms (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
  • Medicines Containing Material From Animals Or Micro-Organisms (AREA)
US12/026,790 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol Expired - Lifetime USRE43844E1 (en)

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US12/026,790 USRE43844E1 (en) 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol
US12/402,752 USRE43984E1 (en) 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
GB0030171.3 2000-12-11
GBGB0030171.3A GB0030171D0 (en) 2000-12-11 2000-12-11 Process for preparing isomers of salbutamol
US12/026,790 USRE43844E1 (en) 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol
US10/450,155 US6995286B2 (en) 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol
PCT/GB2001/005444 WO2002048090A1 (en) 2000-12-11 2001-12-10 Process for preparing isomers of salbutamol

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US (3) USRE43844E1 (de)
EP (1) EP1349828B1 (de)
AT (1) ATE291006T1 (de)
AU (1) AU2002220918A1 (de)
CA (1) CA2431400C (de)
DE (1) DE60109494T2 (de)
ES (1) ES2240335T3 (de)
GB (1) GB0030171D0 (de)
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Publication number Priority date Publication date Assignee Title
GB0030171D0 (en) 2000-12-11 2001-01-24 Cipla Ltd Process for preparing isomers of salbutamol
PT1572622E (pt) 2002-12-10 2006-08-31 Sepracor Inc Sal de levalbuterol
WO2005051092A2 (en) * 2003-11-20 2005-06-09 Alteragon Pty Ltd Method of decreasing fat deposits and body weight in mammals and birds
WO2005113483A2 (en) 2004-05-20 2005-12-01 Teva Pharmaceutical Fine Chemicals S.R.L. Levalbuterol hydrochloride polymorph a
EA200700600A1 (ru) * 2004-09-09 2008-02-28 Сипла Лимитед Фармацевтическая композиция, содержащая изомер бета-миметического агента и антихолинергический агент
EP2311793A1 (de) * 2004-12-17 2011-04-20 Cipla Ltd. Kristallines Levosalbutamol-sulphate (Form II)
RU2440972C2 (ru) * 2004-12-17 2012-01-27 Сипла Лимитед Кристаллический сульфат левосальбутамола, способ его получения и фармацевтическая композиция, содержащая его
TW200740779A (en) * 2005-07-22 2007-11-01 Mitsubishi Pharma Corp Intermediate compound for synthesizing pharmaceutical agent and production method thereof
PL2099740T3 (pl) 2006-08-02 2014-01-31 Aarti Healthcare Ltd Sposób wytwarzania optycznie czystego R(-) salbutamolu oraz ich farmaceutycznie dopuszczalnych soli
EP1935872A1 (de) * 2006-12-11 2008-06-25 Stirling Products Limited Verfahren zur Gewinnung des R-Enantiomers von Salbutamol
AU2009205720A1 (en) * 2008-01-15 2009-07-23 Targacept, Inc. Preparation and enantiomeric separation of 7-(3-pyridinyl)-1,7-diazaspiro[4.4] nonane and novel salt forms of the racemate and enantiomers
CN102260179A (zh) * 2010-05-24 2011-11-30 苏州睿克气雾医药有限公司 硫酸沙丁胺醇拆分新工艺
CN108947854B (zh) * 2018-06-30 2020-09-08 常州市阳光药业有限公司 重酒石酸间羟胺及其异构体的拆分方法

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Publication number Priority date Publication date Assignee Title
US3644353A (en) 1966-09-23 1972-02-22 Allen & Hanburys Ltd 4 hydroxy-alpha'aminomethyl-m-xylene-alpha' alpha**3-diols
JPH0285247A (ja) 1988-09-22 1990-03-26 Kohjin Co Ltd 光学活性チオウレア誘導体
US5399765A (en) 1994-05-23 1995-03-21 Sepracor, Inc. Enantioselective preparation of optically pure albuterol
WO1995032178A1 (en) 1994-05-23 1995-11-30 Sepracor, Inc. Enantioselective preparation of optically pure albuterol
WO1999042460A1 (en) 1998-02-20 1999-08-26 Fine Chemicals Corporation (Proprietary) Limited Process for the production of optically enriched (r)- or (s)-albuterol
CN1273966A (zh) * 1999-10-19 2000-11-22 中国科学院成都有机化学研究所 光学纯的肾上腺素类β－激动剂的组合拆分制备法

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Publication number Priority date Publication date Assignee Title
GB0030171D0 (en) 2000-12-11 2001-01-24 Cipla Ltd Process for preparing isomers of salbutamol

Patent Citations (7)

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US3644353A (en) 1966-09-23 1972-02-22 Allen & Hanburys Ltd 4 hydroxy-alpha'aminomethyl-m-xylene-alpha' alpha**3-diols
JPH0285247A (ja) 1988-09-22 1990-03-26 Kohjin Co Ltd 光学活性チオウレア誘導体
US5399765A (en) 1994-05-23 1995-03-21 Sepracor, Inc. Enantioselective preparation of optically pure albuterol
WO1995032178A1 (en) 1994-05-23 1995-11-30 Sepracor, Inc. Enantioselective preparation of optically pure albuterol
US5545745A (en) * 1994-05-23 1996-08-13 Sepracor, Inc. Enantioselective preparation of optically pure albuterol
WO1999042460A1 (en) 1998-02-20 1999-08-26 Fine Chemicals Corporation (Proprietary) Limited Process for the production of optically enriched (r)- or (s)-albuterol
CN1273966A (zh) * 1999-10-19 2000-11-22 中国科学院成都有机化学研究所 光学纯的肾上腺素类β－激动剂的组合拆分制备法

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Patent Abstract of Japan, vol. 014, No. 280, Jun. 18, 1990.

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US6995286B2 (en) 2006-02-07
US20040054215A1 (en) 2004-03-18
HK1060345A1 (en) 2004-08-06
DE60109494D1 (de) 2005-04-21
CA2431400A1 (en) 2002-06-20
EP1349828B1 (de) 2005-03-16
USRE43984E1 (en) 2013-02-05
CA2431400C (en) 2008-01-22
WO2002048090A1 (en) 2002-06-20
AU2002220918A1 (en) 2002-06-24
PT1349828E (pt) 2005-07-29
GB0030171D0 (en) 2001-01-24
DE60109494T2 (de) 2005-08-04
EP1349828A1 (de) 2003-10-08
ATE291006T1 (de) 2005-04-15
ES2240335T3 (es) 2005-10-16

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