IES20090900A2 - Manufacture of beta blockers - Google Patents

Abstract

A process for preparing bisoprolol comprises reacting oxazolidinone sulphonate with 4-hydroxybenzylaldehyde to form oxazolidinone benzaldehyde, forming oxazolidone benzylalcohol from oxazolidone benzaldehyde, and subsequently reacting oxazolidinone benzylalcohol with isopropyl oxitol to form bisoprolol base.

Description

“Manufacture of beta blockers” This invention relates to the manufacture of Bisoprolol fumarate and intermediates used in the process.

The process described in DOS 2 645 710, describes a process wherein 2(isopropoxy)ethoxymethyl-phenol is reacted with epichlorhydrin and the β-amino alcohol moiety is formed by the addition of iso-propylamine. This synthetic route suffers from several disadvantages including the handling of epichlorohydrin which is a known carcinogen and can undergo violent reactions or exothermic polymerisation on contact with amines or alkoxides. In addition, the reaction between the epoxy intermediate and isopropylamine has ihe potential io undergoes side reactions leading to the formation of the known impurity F (as described in the European Pharmacopeia 6.1).

DOS3205457 describes a process wherein the 2-(isopropoxy)ethoxymethyl substituent is introduced in two stages. Initially the aromatic ring of 3-isopropyl5-phenoxymethyl-oxazolidin-2-one is chloromethylated using HCI and paraformaldehyde followed by a Williamson ether synthesis employing metallic sodium. The resultant oxazolidine ring is cleaved by alkaline hydrolysis.

MCI 3-lsop«opyl4> 'o· Beoprotol Fumarai? Dn»Si Sutbiam c Biioprok)· Funurait· Imp (' Btoprolol Fumar*te |j»p <.« Th is synthetic route suffers from several disadvantages including the handling of metallic sodium which can undergo violent reactions on contact with water or alcohols. In addition the chloromethylation of 3-isopropyl-5-phenoxymcthyloxazolidin-2-one with paraformaldehyde in the presence of HCI undergoes side reactions leading to the formation of the known impurities C and G. This process generates material of inferior quality as exemplified by a limit for impurity G of 0.5% (as described in the European Pharmacopeia 6.1).

Statements of Invention According to the invention there is provided a process for preparing bisoprolol comprising the steps of;reacting oxazolidinone sulphonate with 4-hydroxybenzylaldehyde to form oxazolidinone benzaldehyde; forming oxazolidone benzytalcohol from oxazolidone benzaldehyde; and 0 9 0 9 0 0 -3subsequently reacting oxazolidinone benzylalcohol with isopropyl oxitol to form bisoprolol base.

In one embodiment the oxazolidone sulphonate is formed by reacting isopropylaminopropanediol with dimethylcarbonate and reacting the intermediate product thus formed with benzenesulphonylchloride.

In one case oxazolidinone sulphonate is not isolated prior to reaction with 4hydroxybenzaldehyde.

In one embodiment methylisobutylketone is added to the intermediate product prior to the addition of benzenesulphonylchloride. In this case the reaction between the intermediate and benzenesuphonyl chloride may be performed under phase transfer conditions utilising water soluble bases such as sodium hydroxide.

Alternatively, the reaction between the intermediate and benzenesulphonyl chloride is performed in an organic solvent such as methylisobutylketone utilising bases soluble in organic solvents such as triethylamine.

I'he process may comprise the step of purifying bisoprolol base. The bisoprolol base may be purified by distillation. The bisoprolol base may be purified by crystallisation.

I'he process may comprise the step of forming bisoprolol fumarate by reacting bisoprolol base with fumaric acid.

In one embodiment the process comprises converting bisoprolol fumarate to bisoprolol base.

The invention also provides bisoprolol prepared by a process as described herein. « 0 9 0 9 00 -4The invention further provides bisoprolol fumarate prepared by a process as described herein.

The invention also provides a process for preparing oxazolidinone benzaldehyde by reacting oxazolidinone sulphonate with 4-hydroxybenzylaldehyde, The process for preparing oxazolidone benzylalcohol may comprise converting oxazolidone benzaldehyde to oxazolidone benzylalcohol.

The invention also provides oxazolidinone sulphonate having the formula: ch3 CH^N I he invention further provides oxazolidinone benzaldehyde having the formula: CHO fhe process described in this invention is superior to the conventional processes as the process consistently produces material of high quality suitable for use as a drug substance. Specifically product purity of greater than 99.5% is achieved with no single impurity present above a threshold of 0.10%, as described in ICH guidance Q3A(R2) for impurities in new drug substances.

Brief Description of the Drawings I’he invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is an infra-red spectrum (kBr disc) of oxazolidinone sulphonate; IE Ο 9Ο 9 00 -5Fig. 2 is a ιΗ NMR spectrum (CDCI3, 300 MHz) of oxazolidinone benzaldehyde; Fig. 3 is a l3H NMR spectrum (CDCI3. 75 MHz) of oxazolidinone 5 benzaldehyde; Fig. 4 is an infra-red spectrum (kBr disc) of oxazolidinone benzaldehyde; Fig. 5 is a 'Η NMR spectrum (CDCI3, 300 MHz) of oxazolidinone benzyl 10 alcohol; Fig. 6 is a l3H NMR spectrum (CDCI3, 75 MHz) of oxazolidinone benzyl alcohol; and Fig. 7 is an infra-red spectrum (kBr disc) of oxazolidinone benzyl alcohol.

Detailed Description The process for preparing bisoprolol according to the invention can be 20 summarised as follows: IE 0 9 0 9 00 Oxazolidincne Sulphonate 4-Hjrcfrtayberizaktehyrle Oxazolidaxme Benzaldehyde Iscprcp/I CH Oxazohcwre Benzytalcohol (API Starting Material? OK BrsoproSol Ease crude Example 1 - Stage 1: Synthesis of Oxazolidinone Sulphonate (Step 1) 7CH, Λ CH3 Ν ΟΗ ΟΗ Me0H , ο CHfiNa CH] CH, N OH Isopropylaminopropanediol M.W.:1332 DimeHiylcarbonale M.W.:90 1 (Intermediate not isolated) The following details describe the manufacture of a typical batch 5 A reactor is charged with 392 kg of isopropylaminopropanediol, approximately 240 L of methanol, 6 to 7L of sodium methoxide (30%) and 270 I. of dimethylcarbonate. The contents were heated up to allow reaction to occur. Solvent is removed by distillation. 200 L water and ca 450 L of methylisobutylketone (MIBK) are then charged to the reactor. The reactor contents are then cooled down to <25°C. Tctrabutylammoniumhydrogensulphate (ca 2.5kg) and 520 kg of benzenesulphonylchloride are then added to the vessel under cooling. 30% sodium hydroxide is added to the reactor The reactor contents are heated and phase separation performed, removing the aqueous layer. Solvent is distilled and the product oxazolidone sulphonate is isolated from methyl-zerr-butylether (MTBE).

Fig. 1 illustrates the infra red spectrum of oxazolidinone sulphate.

Purity HPLC >98% -8IE Ο 9 0 9 OO Stationary phase: octadecylsilyl silica gel for chromatography Mobile phase: a mixture of methanol water buffered with potassium hydrogen phosphate and triethylamine Oxazolidinone sulphonate is a novel intermediate and may used for the manufacture of (3-blockers such as Acebutolol, Alprenolol, Atenolol, Betaxolol, Bisoprolol, Esmolol and Metoprolol.

Example 2 - Synthesis of Oxazolidinone benzaldehyde (Step 2) Oxazolidinone Sulphonate 4-Hydroxybenzaldehyde Oxazolidinone Benzaldehyde M.W. 299.3 M.W.1221 Mol. Wt 263 29 A reaction vessel is charged with 154.5kg of 4-hydroxybenzaldehyde. 600 L of dimethylformamide (DMF), 100 kg of potassium carbonate and 475 kg of oxazolidinone sulphonate, The mixture is agitated and heated and held until reaction completion.

I he reactor contents are then cooled down and vacuum is applied, solvent is distilled off and discarded. Water is added to the reactor to facilitate crystallisation and product isolation.

NMR. spectra of oxazolidinone benzaldehyde are illustrated in Figs. 2 and 3. An infra-red spectrum for the product is illustrated in Fig. 4.

Purity HPLC >98%, <1% 4-hydroxybenzaldhyde Stationary phase: octadecylsilyl silica gel for chromatography IE Ο 9 ο 9 00 -9Mobile phase: a mixture of methanol water buffered with potassium hydrogen phosphate and triethylamine Example 3 - Alternative Synthesis of Oxazolidinone benzaldehyde (Step 2) CK3 CH3 ch3 CH CHj γ CH, MeOH CHj Ν'Ζ*'Ύ'~%Η Λ° ZHffjNa sopropylamirrapropanediol MW :133.2 Dlmelhytearbonate M W 90 1 (Intermediate - not isolated! M.W.176.6 Mol. Wt.:263.29 MW: 122 1 '1 Oxazolidinone Sulpnonale [intermediate not isolated) A vessel is charged with 100 g ol'isopropylami nopropanediol, methanol, 3-4 g of sodium methoxide 30% and 70 ml of dimethylcarbonate. The vessel contents are heated up to allow reaction to occur. Solvent is removed by distillation. 100 ml water and methylisobutylketone are then charged to the reaction. The reaction mixture is then cooled down to <25°C. Tctrabutylammomumhydrogensulphate (ca 0.5g) and 145g of benzcnesulphonylchloride are then added to the reaction mixture under cooling. 30% sodium hydroxide is added to the reaction mixture.

I Tie reactor contents are heated and phase separation performed, removing the aqueous layer. Solvent is distilled and the product dissolved in 380 ml dimethylforamide.

IE Ο 9 Ο 9 00 -10Το the reaction vessel is charged 55 g of potassium carbonate and 85 g ot' 4hydroxybenzaldehyde, The mixture is agitated, heated, and held until reaction completion.

The reactor contents are then cooled down and vacuum is applied, solvent is distilled off and discarded. Water is added to the reaction mixture to facilitate crystallisation and the product is isolated.

Purity HPLC >98%, <1 % 4-hydroxybenzaldhyde Stationary phase: octadecylsilyl silica gel for chromatography Mobile phase: a mixture of methanol water buffered with potassium hydrogen phosphate and triethylamine In the specific case of bisoprolol manufacture the key oxazolidinone benzaldehyde intermediate may also be prepared in a ‘'telescoped process described in this example 3. this process is more efficient as the use of MTBE for the isolation of oxazolidinone sulphonate is eliminated. This results in reduced waste disposal costs and a 50% reduction in the requirement for solids separations equipment.

Example 4 - Alternative Synthesis of Oxazolidinone benzaldehyde (Step 2) CH3 H OH H | CHS 'γ' CH; Ms OH + II 0 CH-,QN& CHj N OH OH Isopropylaminopropanediol Dimelhyicerbonale o M W.133.2 M W 9O 1 [Intermediate - not isolated) 4· Hydroxy benzaldehyde MW: 122 1 Oxazolidinone Benzaldehyde Mol Wt 263 29 Oxazolidinone Sulphonate [intermediate not isolated) ΙΕ ο 9 0 9 0 ο - 11 A vessel is charged with 100 g of isopropylaminopropanediol, methanol, 3-4 g ot sodium methoxide 30% and 70 ml of dimethylcarbonate. The vessel contents arc heated up to allow' reaction to occur. Solvent is removed by distillation and ca 400 ml methylisobutylketone is then charged to the reaction, fhe reaction mixture is then cooled and 80g of triethylamine and 145g of bcnzenesulphonylchloride are added.

Water is added and the reaction mixture is heated and phase separation performed, removing the aqueous layer. Solvent is distilled and the product dissolved in 380 ml dimethyl foramide.

To the reaction vessel is charged 55 g of potassium carbonate and 85 g of 4hydroxybenzaldehyde. The mixture is agitated, heated, and held until reaction completion. fhe reactor contents are then cooled down and vacuum is applied, solvent is distilled off and discarded. Water is added to the reaction mixture to facilitate crystallisation and the product is isolated.

Purity HPLC >98%, <1% 4-hydroxybenzaldhyde Stationary phase: octadecylsilyl silica gel for chromatography Mobile phase: a mixture of methanol water buffered with potassium hydrogen phosphate and triethylamine In the specific case of bisoprolol manufacture the key oxazolidinone benzaldehyde intermediate may also be prepared in a ‘'telescoped*' process described in this example 4. This process is more efficient than the process described in examples 2 and 3, as the use of triethylamine under non aqeous reaction conditions for the coupling reaction between oxazolidinone sulphonate and benzenesulphonyl chloride is more efficient. This results from a reduction in side reactions under aqueous conditions which lead to the formation of sodium benzenesulphonate as a by-product.

.CH,OH 090900 -12Example 5 - Step 3 - Conversion of Benzaldehyde to Benzylalcohol ch3 CH^N )-° .CHO Oxazolidinone Benzaldehyde M.W.:263 3 K2CO3, DIW NaBHi n-Butanot Oxazolidinone Benzylalcohol M.W.; 265.3 Sodium borohydride (llKg) in a mixture of water (71L) and sodium hydroxide (0.3L), to n-butanol (300L). Water (150L) potassium carbonate and oxazolidinone benzaldehyde (271 Kg) are charged to a vessel.

The vessel contents are heated up to 100°C, cooled and ethyl acetate (100L) is charged to the vessel. Water or brine is used for washing and solvent is distilled off and the product is isolated from ethyl acetate.

NMR spectra of oxazolidinone benzaldehyde are illustrated in Figs. 5 and 6. An infra-red spectrum for the product is illustrated in Fig. 7.

Purity HPLC >99% Stationary phase: octadecylsilyl silica gel for chromatography Mobile phase: a mixture of methanol water buffered with potassium hydrogen phosphate and triethylamine Example 6: Purification of Bisoprolol Base Bisoprolol base is formed from the oxazolidinone benzyl alcohol by an acid catalysed coupling with isopropyl oxitol, followed by alkaline hydrolysis of the oxazolidinone ring. The resultant bisoprolol base maybe furlher purified either by distillation or crystallation.

Example 7: Salt Formation IE 0 9 0 9 00 -13The purified bisoprolol base is converted to Pharmacopoeia grade bisoprolol fumarate by addition of fumaric acid to bisoprolol base in acetone.

Example 8: Bisoprolol Base for use as a drug substance Charge bisoprolol fumarate (30Kg) in a mixture of water (30IL) and sodium methyl-zcrz-butylether (I05L), add aqueous sodium hydroxide to alkaline pH. Split the lower aqeous layer to waste and wash the product layer with water. Bisoprolol base is isolated following solvent removal by distillation.

Patches are routinely used for the controlled release of drugs via the trans dermal route, the approach is advantageous over oral administration which can result in irregular and unpredictable blood plasma levels. Bisoprolol is normally administered in oral solid dose form as the fumarate salt, but is not suitable for controlled release from transdermal patch formulations. It has been found that Bisoprolol base prepared as described in this application is particularly suited to controlled release from transdermal patch formulations.

The invention is not limited to the embodiment hereinbefore described, with reference to the accompanying drawings, which may be varied in and detail.

Claims (3)

1. Clairns
1. I. A process for preparing bisoprolol comprising the steps of> reacting oxazolidinone sulphonate with 4-hydroxybenzylaldehyde to form oxazolidinone benzaldehyde; forming oxazolidone benzylalcohol from oxazolidone benzaldehyde; and subsequently reacting oxazolidinone benzylalcohol with isopropyl oxitol to form bisoprolol base. A process as claimed in claim l wherein the oxazolidone sulphonate is formed by reacting isopropylaminopropanediol with dimethylcarbonate and reacting the intermediate product thus formed with benzenesul phony lch I or ide. A process as claimed in claim 1 or 2 wherein oxazolidinone sulphonate is not isolated prior to reaction with 4-hydroxybenzaldehyde.
2. 2. 4, A process as claimed in claim 2 or 3 wherein methylisobutylketone is added to the intermediate product prior to the addition of benzenesulphonylchloride, the reaction between the intermediate and benzenesuphonyl chloride is preferably performed under phase transfer conditions utilising water soluble bases such as sodium hydroxide, the reaction between the intermediate and benzenesulphonyl chloride may be performed in an organic solvent such as methylisobutylketone utilising bases soluble in organic solvents such as triethylamine.
3. 3. 5. A process as claimed in any of claims 1 to 4 comprising purifying bisoprolol base such as by distillation, or by crystallisation.