PREPARATION OF beta -LACTAM ANTIBIOTICS IN THE PRESENCE OF UREA OR AMIDE

Abstract: A process to prepare a crystalline beta -lactam compound by the addition of a base to an acidic solution of a beta -lactam compound obtained by the addition of an acid to a solution or suspension of a beta -lactam compound obtained by (a) an acylation reaction of 6-amino-penicillanic acid, 7-amino-cephalosporanic acid, 7-amino-3'-desacetoxycephalosporanic acid or 3-chloro-7-aminodesacetoxydesmethylcephalosporanic acid or derivatives thereof with a mixed-anhydride of the Dane salt of any one of the compound comprising D-phenyl-glycine, D-p-hydroxyphenyl-glycine, D-2(1,4-cyclohexadien-1-yl)glycine or (2-aminothiazol-4-yl)-(2-methoxy-imino-acetic acid) in one or more organic solvents, or (b) dissolving or suspending a crude beta -lactam compound in a solution comprising water and/or one or more organic solvents, wherein, to the solution or suspension of a beta -lactam compound, urea or derivatives thereof and/or amide or derivatives thereof are added.

Description: PREPARATION OF β-LACTAM ANTIBIOTICS IN THE PRESENCE OF UREA OR AMIDE The present invention relates to an improved process for the preparation of β-lactam antibiotic compounds in the presence of urea or derivatives thereof and/or amide or derivatives thereof. It is commonly accepted that the most economical approach for the isolation of compounds such as β-lactam antibiotics or their intermediates from their solutions comprising the same is crystallization. Various processes have been proposed for the preparation of the semi-synthetic β-lactam antibiotic compounds such as penicillins and cephalospoπns . These proposals generally involve the acylation of 6- ammopenicillanic acid (6-APA) or 7-ammocephalosporanιc acid (7-ACA) or a protective derivative thereof using, for example, an acyl halide serving to introduce the desired acyl group. For example in European patent application EP 0011513, a process has been described for the preparation of zwitterionic antibiotics, for instance, ampicillm, amoxicillm or cephalexm through acylation of silylated 6-ammopenιcιllanιc acid or 7- aminocephalosporanic acid with a phenylglycyl halide or p-hydroxyphenylglycyl halide the presence of N- alkylpyrrolidone as an acid acceptor. Similarly United States patent US 4,248,780 for example, describes the preparation of zwitterionic antibiotic ampicillm through acylation of silylated 6-ammopenιcιllanιc acid with a phenylglycylchloπde hydrochloπde by using urea as a base . Furthermore, a number of patent applications and patents disclose preparation method of α- ammoacylpenicillanic acid derivatives by acylatmg 6- APA with mixed anhydrides derived from modified Dane salts of D-2 -ammo- (p-hydroxyphenyl) -acetic acid, such as described m German patent Applications Ser. No. 1,302,847, No. 2,020,133 and No. 2,065,879 and British Patents No. 1,327,270 and No. 1,347,979. United States patent US 4,358,588 describes an improved process for the preparation of D-α-ammo-p- hydroxyphenyl-acetamide-penicillanic acid and cephalosporamc acid derivatives by reacting an appropriate mixed anhydride of a Dane salt with a protected derivative, for example 6-APA or 7-ACA m the presence of a tertiary am e . This type of acylation is referred to as Dane salt coupling reaction. Thereafter, the β-lactam antibiotic compounds are isolated from an acidic aqueous solution, obtained by acidic hydrolysis of the reaction mixture after the Dane salt coupling reaction, by adding a base and followed by filtration. A manor drawback of the processes for the preparation of β-lactam antibiotic compounds is the crystallization of unwanted by-products, among which the hydrochloric acid salts of the β-lactam antibiotic compounds are the most notorious one. These unwanted crystallization of by-products can occur at any stage of the hydrolysis or crystallization procedure. The formation of acid salts of the β-lactam antibiotic compounds is strongly dependent upon temperature, pH and time during the acidic hydrolysis of the Dane salt coupling reaction. Lower temperatures, a lower pH and prolonged time during the hydrolysis of the Dane salt coupling reaction result the production of an increased amount of acid salt of the corresponding β- lactam antibiotic compound. At higher temperatures, however, the formation of the corresponding acid salt of the β-lactam during hydrolysis of the Dane salt coupling reaction is reduced but on the other hand the cleavage of the β-lactam is enhanced. Also, the presence of seeding crystals corresponding to acid salt of the β- lactam compound, produced during the hydrolysis of the Dane salt coupling reaction, facilitate the formation of the acid salts of the β-lactam antibiotic compounds. Especially the formation of the seeding material during the hydrolysis of Dane coupling reaction is enhanced on an industrial scale process compared to a laboratory scale process. Thus, the crystalline products resulting from the Dane salt coupling reaction often contain unacceptable levels of impurities . It was found surprisingly that β-lactam antibiotic compounds free of acid salts of the corresponding β-lactams can be prepared under addition of urea or derivatives thereof and/or amide or derivatives thereof after the Dane salt coupling reaction at low temperature. Urea or derivatives thereof and/or amide or derivatives thereof can also be added during the purification of crude β-lactam antibiotic compounds during the crystallization phase. Besides the lower content of the hvdrochloric acid salt of the β- lactam produced, these processes also result in a higher yield of the end product . This method has nowhere been described or suggested for β-lactam compounds until now. Summary of the invention The present invention provides an improved process for the preparation of β-lactam antibiotic compounds the presence of urea or derivatives thereof and/or amide or derivatives thereof. The β-lactam compounds are crystallized by the addition of a base to an acidic solution of a β-lactam compound obtained by the addition of an acid to a solution or suspension of a β-lactam compound obtained by (a) an acylation reaction of 6-ammo-penιcιllamc acid, 7-ammo-cephalosporanιc acid, 7-ammo-3'- desacetoxycephalosporamc acid or 3-chloro-7- ammodesacetoxydesmethylcephalosporanic acid or derivatives thereof with a mixed-anhydride of the Dane salt of any one of the compounds comprising D-phenyl- glycine, D-p-hydroxyphenyl-glycme, D-2(l,4- cyclohexadιen-1-yl) glycme or (2-ammothιazol-4-yl) - (2- methoxy-im o-acetic acid) in one or more organic solvents, or (b) dissolving or suspending a crude β-lactam compound m a solution comprising water and/or one or more organic solvents, characterised by the addition, to the solution or suspension of a β-lactam compound, of urea or derivatives thereof and/or amide or derivatives thereof. Before starting the crystallization process through the addition of a base, the pH of the solution - 5 - or suspension of a β-lactam compound is maintained at the desired pH by the addition of an acid. Normally, the pH is maintained between 0.1 and 3.5 and preferably between 0.3 and 2.5 depending on the type of β-lactam compound to be produced. When the solution of the β- lactam compound is obtained by (a) , the acid that is added may assist m the acid hydrolysis of the reaction mixture from the acylation reaction. The temperature at which the acid is added is preferably between -50°C and 10°C, preferably between -5°C and 5°C and most preferably between -5°C and 0°C. The acid may be any acid, preferably an inorganic acid, for example hydrochloric acid, nitric acid or sulphuric acid. Preferably, the acid is hydrochloric acid. The temperature during the crystallization may vary. Suitably, the crystallization temperature is between -10°C and 50°C, preferably between -5°C and 35°C. It will be clear for the skilled the art that the preferred conditions will depend on the β-lactam compound to be prepared. The β-lactam antibiotic compounds can be isolated n a conventional manner, by adjusting the pH to the lsoelectπc point of the corresponding β-lactam compounds . The β-lactam compounds are for instance penicillins and cephalosporms. Examples of penicillins are amoxicillm, ampicillm and epicillm. Examples of cephalosporms are cefaclor, cefadroxil, cefetamet, cefotaxim, cephalex , cephaloglyc , cephradme and cefroxadine. - 6 - Detailed description of the invention The process for the preparation of crystalline β-lactam antibiotic compounds according to the present invention comprises the addition of a base to an acidic solution of a β-lactam compound obtained by the addition of an acid to a solution or suspension of a β-lactam compound obtained by (a) an acylation reaction of 6-ammo-penιcιllanιc acid (6-APA) , 7-ammo-cephalosporanιc acid (7-ACA) , 7 -amino- 3 ' -desacetoxycephalosporanic acid (7-ADCA) or 3-chloro- 7-ammodesacetoxydesmethylcephalosporanιc acid (7-ACCA) or derivatives thereof with a mixed-anhydride of the Dane salt of any one of the compounds comprising D- phenyl -glycme, D-p-hydroxyphenyl -glycme, D-2(l,4- cyclohexadιen-1-yl) glycme or (2-ammothιazol-4-yl) - (2- methoxy-immo-acetic acid) in one or more organic solvents, or (b) dissolving or suspending a crude β-lactam compound m a solution comprising water and/or one or more organic solvents, characterised by the addition, to the solution or suspension of a β-lactam compound, of urea or derivatives thereof and/or amide or derivatives thereof with the formula (A) and (B) respectively, R^N-CO- R^ R 3 -CO-NR 1 R 2 (A) (B) wherein R 1( R 2 , R 3 and R 4 are each independently chosen from the group consisting of hydrogen, lower alkyl and allyl, or - 7 - Ri . and R 3 form -CH 2 -CH 2 -, -CH 2 -CH 2 -CH 2 - , -CH 2 -CO- and - CH=CH-CO- resulting together with -N-CO-N- in a five or six membered cyclic ring, (C x - C 6 )alkanol esters of (C λ - C 6 ) carboxylic acid. Preferably, R x , R 2 , R 3 and R 4 in formula (A) are each chosen from hydrogen or methyl , and more preferably R l r R 2 , R 3 and R 4 are each hydrogen. The amount of urea or derivatives thereof and/or amide or derivatives thereof present during the crystallization process may vary, and preferably is between 0.001 mol/mol β-lactam and 7.5 mol/mol β-lactam, more preferably between 0.1 mol/mol β-lactam and 5.25 mol/mol β-lactam. By derivatives of 6-APA, 7-ACA, 7-ADCA and 7-ACCA have been meant salts and esters thereof. Preferably, a small amount of a (C x - C 6 )alkanol, specifically methanol , ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2 -methyl -1-propanol , or a ketone, specifically acetone, methylethylketone, methylisobutylketone or an ester, specifically methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate or an ester of {C λ - C s ) carboxylates with a (C x - C 6 )alkanol or a mixture thereof is added as a co-solvent to the solution or suspension of a β-lactam compound. The Dane salt coupling reaction is carried out in a dry water-insoluble organic solvent, for instance dichloromethane . When the solution or suspension of a β-lactam compound is obtained by (a) , the co-solvent is preferably added after the Dane salt coupling reaction. The concentration of the co-solvent is between 0.1% and 60%, preferably between 25% and 60% depending on the type of the β-lactam compound to be prepared. The pH of the acidic solution is maintained between 0.1 and 3.5, preferably between 0.3 and 2.5, by using an acid. The temperature of the solution during the addition of the acid may vary, and is usually between -50°C and 10°C, preferably between -5°C and 5°C and more preferably between -5°C and 0°C. At higher temperatures, the cleavage of the sensitive β-lactam ring of the antibiotic compound is enhanced. The acid is an inorganic acid, for example hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid or an organic acid, for example formic acid and suitable acetic acid or derivatives thereof. Preferably, hydrochloric acid is used. The β-lactam antibiotic compound is isolated m conventional manner, by adjusting the pH between 2.0 and 7.0, preferably to the isoelectric point of the said β-lactam antibiotic compound by addition of a base. Furthermore, seeding material is optionally added to the crystallization solution before the addition of the base. The base is an inorganic base, preferably sodium hydroxide, potassium hydroxide, ammonium hydroxide or an organic base, preferably an amme . Accordingly, after filtration and drying crystalline products substantially free of impurities such as the acid salt of the same, β-lactam compounds are obtained whereas known procedures without application of urea or derivatives thereof and/or amide - 9 - or derivatives thereof give higher levels of impurity, especially when the crystallization is performed at a lower temperature. The process of the present invention is particularly suitable for the preparation of β-lactam antibiotics m the form of a zwitterionic ammo acid. Examples of said antibiotics are amoxicillm, ampicillm, epicillm, cefaclor, cefadroxil, cefetamet, cefotaxim, cephalexm, cephaloglycm, cephradme and cefroxadme. According to a further aspect of the present invention the β-lactam compound is advantageously crystallized by simultaneous addition of the β-lactam solution and a base to a crystallization vessel as described in non-published European patent application No. 97203484.7. This crystallization process comprises simultaneous addition of the acidic solution of a β- lactam compound containing urea or derivatives thereof and/or amide or derivatives thereof and a titrant, namely the base, to a crystallization vessel. The process of crystallization of antibiotic compounds, according to the present invention, has a major advantage over the existing methods because better concordance results are possible. The concordance value related to the difference between titration with a strong acid and titration with a strong base has been defined according to the United States Pharmacopoeia, twenty- first revision, dated January 1, 1985. A small concordance value stands for a constant quality product. Ampicillin trihydrate, for instance isolated from crystallization of a solution containing ampicillm 10 - hydrochloride has a concordance value of less than 1 mol %, while crystallization through a prior art procedure of a number of experiments has given a concordance value between 4 and 8 mol %. The β-lactam antibiotic compounds with a small concordance value, i.e. comprising lower amounts of acid salt of the corresponding β-lactam antibiotics, are suitable for pharmaceutical formulation purposes . Furthermore, the bad effect of storage and temperature (higher than room temperature) on the stability of the β-lactam antibiotic compound is enhanced due to the presence of very small or negligible amounts of the corresponding acid salt of β-lactam antibiotic compound. These acid salts of the β-lactam antibiotic are usually hygroscopic in nature. Thus, the product obtained by the process according to the invention is new. The invention will now be described with reference to the following Example, which are not to be constructed as being limiting on the invention, and are provided purely for illustrative purposes. Example STEP A: Preparation of methoxycarbonyl D-α- (1- carbomethoxypropen-2-yl) amino-p-hydroxyphenyl -acetate . 85 ml of N, N-dimethylacetamide, 116.4 g of potassium D- α- [1- (carbomethoxypropen-2-yl) -amino] -p- hydroxyphenylacetate and 0.3 ml pyridine were added to 267 ml of dichloromethane and the resulting suspension was cooled to -40°C. Subsequently 46.3 g of pivaloylchloride was added to this solution. While - 11 - maintaining a temperature of -30°C the mixture was stirred for 90 minutes and then cooled to -50°C. STEP B: 63.8 g of tπethylamme was added to a suspension of 80.0 g of 6-ammopenιcιllanιc acid m 533 ml of dichloromethane at 20°C and the mixture was stirred for 90 minutes. The mixture should contain enough water for obtaining a clear solution. At 5°C, 78 g of 2-ethylhexanoιc acid was added and the solution was further cooled to -50°C. STEP C: Preparation of amoxicillme tπhydrate. The reaction mixture obtained in STEP A was added in about 3 minutes into the solution obtained m STEP B with vigorous stirring. In 3 hours the temperature was gradually increased from -40°C / -35°C to -10°C / -5°C. Subsequently, a solution of urea (100 g 800 ml of demmeralised water) was added. While maintaining the mixture at between -5°C and 0°C concentrated hydrochloric acid was added and hydrolysis was continued for 30 minutes at a pH between 1.4 and 1.5. The organic phase was separated and the product was crystallised from the aqueous layer by addition of approximately 45 ml of 8 N sodium hydroxide solution until pH between 4.8 and 5.0 at a temperature of between 2°C and 5°C. The suspension was kept over night under these conditions, filtered, washed with 100 ml of chilled, demmeralised water and 300 ml of chilled acetone. The cake was dried at 35°C till a constant weight was reached to obtain about 143 g of amoxicillm tπhydrate with a purity of 86.1% as amoxicillm anhydrous (HPLC) .

Claims: - 12 - C L A I M S 1. A process to prepare a crystalline β-lactam compound by the addition of a base to an acidic solution of a β-lactam compound obtained by the addition of an acid to a solution or suspension of a β-lactam compound obtained by (a) an acylation reaction of 6-ammo-penιcιllanιc acid, 7-ammo-cephalosporanιc acid, 7-ammo-3'- desacetoxycephalosporanic acid or 3-chloro-7- aminodesacetoxydesmethylcephalosporanic acid or derivatives thereof with a mixed-anhydride of the Dane salt of any one of the compound comprising D- phenyl -glycme, D-p-hydroxyphenyl -glycme, D- 2 (1, 4-cyclohexadιen-l-yl) glycme or (2- ammothιazol-4-yl) - (2-methoxy-ιmmo-acetιc acid) m one or more organic solvents, or (b) dissolving or suspending a crude β-lactam compound in a solution comprising water and/or one or more organic solvents , characterised by the addition, to the solution or suspension of a β- lactam compound, of urea or derivatives thereof and/or amide or derivatives thereof with the formula (A) and (B) respectively, R^- J N-CO-NR J R J R 3 -CO-NR 1 R 2 (A) (B) wherein R 1# R 2 , R 3 and R 4 are each independently chosen from the group consisting of hydrogen, lower alkyl and allyl, or - 13 - R x and R 3 form -CH 2 -CH 2 -, -CH 2 -CH 2 -CH 2 - , -CH 2 -CO- and - CH=CH-CO- resulting together with -N-CO-N- in a five or six membered cyclic ring, (C x - C 6 )alkanol esters of (C x - C s ) carboxylic acid. 2. A process according to claim 1 wherein in the formula (A) , R , R , R and R 4 are each chosen from hydrogen or methyl . 3. A process according to any one of the claims 1-2, wherein when using the solution of a β-lactam compound obtained by (a) , the temperature at which the acid is added is maintained between -50°C and 10°C. 4. A process according to any one of the claims 1-3, wherein the amount of urea or derivatives thereof and/or amide or derivatives thereof is between 0.001 mol/mol β-lactam and 7.5 mol/mol β-lactam, preferably between 0.1 mol/mol β-lactam and 5.25 mol/mol β-lactam. 5. A process according to any one of the claims 1-4, wherein the solution of the β-lactam antibiotic compound comprises one or more co-solvents chosen from the group of {C λ - C 6 )alkanol or ketone or ester of a (Cj_ - C s ) carboxylate with a (C x - C s ) alkanol . 6. A process according to claim 5, wherein when using the solution of a β-lactam compound obtained by (a) , the co-solvent or solvents are added after the coupling reaction. 7. A process according to claim 5 or 6 , wherein the concentration of (C x - C s ) alkanol or ketone or ester is between 0.1% and 60%. - 14 - 8. A process according to any one of the claims 1-7, wherein the pH of the acidic solution before the addition of a base, has been maintained between 0.1 and 3.5, preferably between 0.3 and 2.5, by using an acid. 9. A process according to claim 8, wherein the acid is hydrochloric acid. 10. A process according to any one of the claims 1-9, wherein during crystallization, the pH is maintained between 2.0 and 7.0, preferably close to the isoelectric point of said β-lactam compound by addition of a base. 11. A process according to any one of the claims 1-10 wherein the base is an inorganic base, preferably sodium hydroxide, potassium hydroxide or ammonium hydroxide . 12. A process according to any one of the any one of the claims 1-11 wherein seeding crystals are added before the addition of the base. 13. A process according to any one of the claims 1-12 wherein the temperature during the crystallization is maintained between -10°C and 50°C, preferably between -5°C and 35°C. 14. A process according to any one of the claims 1-13 wherein the β-lactam compounds are penicillins and cephalosporins, preferably amoxicillm, ampicillin, epicillin, cefaclor, cefadroxil, cefetamet, cefotaxim, cephalexine, cephaloglycin, cephradine and cefroxadine. 5709 15 - 15. A process according to any one of the preceding claims, wherein the acidic solution of a β-lactam compound and a base are simultaneously added to a crystallization vessel. 16. A β-lactam compound obtainable by a method according to any of the preceding claims.

Inventors: EL SAYAD HASSAN ALY, LEENDERTS EVERARDUS JOHANNES A, WALRAVEN HUBERTUS GERARDUS MAR, WESSELING JOLANDA, EL SAYAD, HASSAN, ALY, LEENDERTS, EVERARDUS, JOHANNES, ANTHONIUS, MARIA, WALRAVEN, HUBERTUS, GERARDUS, MARIA, WESSELING, JOLANDA
Applicants: DSM NV, EL SAYAD HASSAN ALY, LEENDERTS EVERARDUS JOHANNES A, WALRAVEN HUBERTUS GERARDUS MAR, WESSELING JOLANDA, DSM N.V., EL SAYAD, HASSAN, ALY, LEENDERTS, EVERARDUS, JOHANNES, ANTHONIUS, MARIA, WALRAVEN, HUBERTUS, GERARDUS, MARIA, WESSELING, JOLANDA
Application year: 1999
Main classification: C07D499
IPC codes: C07D499, C07D501