IE41636B1 - Penicillin-type antibiotic and process for producing same - Google Patents

Description

The present invention relates to the acetone adduct of the methoxymethyl ester of amoxicillin and to a method for the production thereof.

By the term acetone adduct as used herein is meant the product obtained by reacting an appropriate a-amino compound with a stoichiometric amount of acetone.

More particularly, the present invention provides a compound of the formula (I) -Or NH CH. yj-CH— (jH C-CH COOCH-OCH, (I) having the D-configuration at the carbon atom marked with an asterisk, or a pharmaceutically acceptable salt thereof. Compound (I), which may be named methoxymethyl D-6-[2,2-dimethyl-5oxo-4-(£-hydroxyphenyl)-1-imidazolidinyl] penicillanate, will for convenience be referred to hereinafter as £-hydroxy15 hetaeillin methoxymethyl ester.

The antibiotic compound of this invention is a derivative of £-hydroxy-hetacillin and amoxicillin. Amoxicillin is also known as D-6-(£-hydroxy-ct-aminophenylacetamido)-penicillanic acid. Hetaeillin, a penicillin derivative, is known in the acid form as D-6-(2,2-dimethyl-5-oxo-4-phenyl-l-imidazolidinyl) penicillanic acid.

The present invention also provides a process for preparing the methoxymethyl ester of £-hydroxyhetacillin, or a pharmaceutical ly acceptable salt thereof, which process comprises the consecutive steps of a) forming a penicillin ester of the formula xs\XH3 RCONH-CjH — CH C -CHj —N -C-COOCH2OCH3 wherein K is an organic radical, b) deacylating said penicillin ester to form me Ihoxymethy1 6-aminopenici lianate, c) reacylating said methoxymethyl 6-amino5 penicillanate with the acyl moiety of D-(-)-2-p-hydroxyphenylglycine to produce the methoxymethyl ester of amoxicillin, d) reacting said methoxymethyl ester of amoxicillin with acetone to produce the methoxymethyl ester of p-hydroxyhetacillin and; °) if desired, converting said methoxymethyl ester of p-hydroxyhetacillin into a pharmaceut ically acceptable salt thereof according to known methods. r is preferably a phenoxymethyl group. Step d) is preferably conducted at a pH in the range of 5.5 to 9.5, most preferably 7.5 to 9. 5.

In general, the methoxymethyl ester of hetacillin or of amoxicillin can be prepared by reacting a penicillin produced by fermentation,such as phenoxymethyl penicillin,with a suitable esterifying derivative of dimethyl ether, such as a halomethyl methyl ether. The phenoxymethyl penicillin ester so produced is then deacylated by known procedures to provide the corresponding methoxymethyl 3 ester of 6-amino-penicillanic acid. This 6-APA ester and a suitable acylating agent may then be reacted as shown herein.

The 6-APA ester can be acylated by known procedures to provide various penicillin esters according to the choice of acylating agents. The choice of -341636 acylating agent and conditions for acylation are not narrowly critical. Either the free acid, that is, D-(-)-2-p-hydroxyphenylglyclne, or its equivalent can be employed to acylate the free amino group of the 5 6-APA ester. Such acylating agents include the free acid and the corresponding carboxylic acid halides, e.g., the chlorides and .bromides; the acid anhydrides, including mixed anhydrides and particularly the mixed anhydrides prepared from acids such as the lower (C1~C4) 0 aliphatic monoesters of carbonic acid, of alkyl and aryl sulfonic acid and of more hindered acids, such as diphenylacetic acid. In addition, an acid azide or an active ester or thioester (e.g., with p-nitrophenol, 2,4-dinitrophenol, thiophenol, thloacetic acid) may be 5 used or the free acid itself may be coupled with 6aminopenicillanic ester after first reacting said free ' acid with Ν,Ν'-dimethylchloroformiminium chloride [cf.

British Patent Specification No. 1,008,170 and Novak and Weichet,Experien tla XXI/6, .360 (1965)] or by the use of enzymes or of 5 an Η,Ν'-carbonyldiimidazole or an Ν,Ν'-carbonylditriazole [cf. South African Patent Specification 65/268^] or of a carbodiimide reagent [especially N,N-dlcyclohexylcarbodiimide, Ν,Ν'-dlisopropylcarbodilmide or N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide; cf. Sheehan and Hess, J. Amer, Chem. Soc.. 77. 1067 (1955)1, or of alkynylamine reagent [cf. R. Buijle and H. G. Viehe, Anvew. Chem. International Edition, jj, 582 (1964)], or of a ketenimine reagent [cf. C. L. Stevens and Μ. E. Monk, -441636 J. Amer. Chew, Soc.. 80. 4065 (195θ)1 or of an isoxazolium salt reagent [cf. R. B. Woodward, R. A. Olofson and It. Mayer, J, Amer, Chem, Soc,. 83. 1010 (1961)] or of hexachlorocyclotriphosphatriazine or hexabromocyclo5 triphosphatriazine (U.S. 3,651.050) or of dlphenyIphosphoryl azide [DPPA; J, Amor. Cf'iem.. Soc.. 94. 6203-6205 (1972)] or of diethylphosphor^l cyanide [DFPC; Tetrahedron Letters No. 18, pp. 1595-1598 (1973)1 or of diphenyl phosphite [Tetrahedron Letters No. 49, pp. 5047-5050 (1972)] and it is also convenient and efficient to utilize as the coupling agent phosphonitrllie chloride trlmer (JL. Opp:. Chem.. 33(7). 29798l, 1968) or N-ethoxy1,2-dihydroquinoline (EEDQ) as described in J. Amer. Chem, Soc.. 90.. 823-824 and 1652-1653 (1968).

Another equivalent of the acid i3 a corresponding azolide, i.e., an amide of the acid the amide nitrogen of which is a member of a quasi-aromatic five-membered ring containing at least two nitrogen atoms, i.e,, imidazole, pyrazole, the triazoles, behzimld9 azole, benzotriazole, and their substituted derivatives.

As an example of the general method for the preparation of an azolide, Ν,Ν'-carbonyldiimidazole ls reacted with a carboxylic acid in equimolar proportions at room temperature ln tetrahydrofuran, chloroform, dimethyl> formamide or a similar inert solvent to form the carboxylic acid imidazolide ln practically quantitative yield with liberation of carbon dioxide and one mole of imidazole. Dicarboxylic acids yield diimldazolides. The by-product, imidazole, precipitates and may be separated and the -541633 lmldazolide Isolated, but this Is not essential. The methods for carrying out these reactions to produce a · χ penicillin and the methods used to isolate the penicillin so produced are well known ln the art iof. U.S. Patent Nos. 3,079,314, 3,117,126, 3,129,224 and British Patent Nos. 932,644, 957,570 and 959,054).

/ Mention was made, Shove of the use of enzymes to couple the free acid,.with methoxymethyl 6-aminopeniclllanate. Included in the scope of such processes are the use of an ester, e.g. the methyl ester, of that free acid with enzymes provided by various microorganisms, e.g. those described by T, Takahashi et al,, J. Amer.

' Chem. Sjc^, 94(11), 4035-4037 (1972) and by T. Nara et al., J. Antibiotics (Japan) 24(¾). 321-323 (1971) and in.U.S. 3,632,777.

In a case such as this where the acylating *' agent contains a free amino group, it may be desirable to protect it with a suitable blocking agent. Such protecting 2θ groups include those of the general formula ROCO—in which R is an allyl, benzyl,, substituted benzyl, phenyl, .-.'ibstituted phenyl, or trityl group. It is usually preferred, however, to use D-(-)-2-p-hydroxyphenylglycyl chloride hydrochloride as the acylating agent.

Another preferred process consists of a) acylating the methoxymethyl ester of 6-aminopenicillanic acid with an acid in the D- configuration of the formula -641636 ι 2 wherein R is an alkyl, aralkyl or aryl group, R is a hydrogen □ atom, an alkyl, aralkyl or aryl group and R is an alkyl, aralkyl aryl, alkoxy, aralkoxy or aryloxy group, or the group - N. wherein R^ and R^ are each a hydrogen atom, an alkyl, aralkyl or aryl group or, when taken together with the nitrogen atom, represent a piperidino or morpholino group, or an acylating derivative thereof in an inert solvent at a temperature below 0°C, and (b) removing the α-amino-protecting group.

In this process it is preferred that there is also present during step (a) a compound of the formula ,CH2X CH3-N, 'ch2y wherein X is a hydrogen atom or an alkyl or phenyl group, Y is a hydrogen atom or a lower (C^-C^) alkyl group, or X and Y together represent an ethylene, substituted ethylene, trimethylene, -CH2OCH2- or -CH2N(CH^)CJJ2- group. Examples of such catalysts are 416 3 6 N-methylmorpholine and Ν,Ν-dimethylbenzyln-nine. j. It is preferred that the inert solvent be acetone or aqueous acetone or tetrahydrofuran and that the acylating derivative be a mixed anhydride formed from an alkvl chlorocarbonate. / It is further preferred that, in the en-amine 1 2 amino-protecting group, R is methyl, R ic hydrogen and R is methoxy, ethoxy or methyl· This requires the use of methyl acetoacetate, ethyl acetoacetate lo ' or acetylacetone.

In the removal of the a-amino-protecting group it is preferred that use be made of a strong mineral acid such as hydrochloric acid or of formic acid. < -841636 The resulting penicillin ester, e.g., the methoxymethyl ester of amoxicillin, is then reacted with acetone to form the acetone adduct ester, e.g., phydroxy-hetaclllin ester, in accordance with the pro5 cedure disclosed in the United States Patent 3,198,804.

Thus in performing this reaction the proportions of each reactant are not critidal- some reaction will occur regardless of the proportions of reactants. It is preferred, however, to use at least a one mole excess of acetone in order to obtain, maximum yields, larger molar excesses of acetone may be used and indeed the acetone may comprise the reaction medium as well as being a reactant. The reaction medium may be anhydrous or aqueous. The reaction is an Ί C equilibrium reaction during which water is split off and it is therefore preferred not to have a major amount of water present in the reaction medium.

The pH of the reaction mixture during the formation of this p-hydroxyhetacillin ester should be from 5.5 to 9.5 and is preferably from 7.5 to 9.5. The pH may be adjusted to within thi3 range, if necessary, by the addition of an alkaline material, for example, sodium hydroxide, sodium carbonate, potassium hydroxide, potassium :5 carbonate, ammonium hydroxide, ammonium carbonate or organic amines, e.g., triethylamine.

The temperature during the reaction is· not critical. The reaction will proceed satisfactorily at room temperature and may be hastened by heating. -941636 Broadly, this process involves esterification of a natural penicillin of the structure RCONH-CH-CH CH, II Ί 3 C — N-CCOOH II ' H 0 wherein R Is an organic radical of which many are well known In the penicillin art. The acyl group of any of the well known natural penicillins can be employed. A particularly suitable side chain is the phenoxymethyl group.

OCH2 Illustrative organic radicals include benzyl, furylmethyl, and thienylmethyl. As is well known, the various organic radicals can be substituted. -io41636 More particularly, in the process of this invention a salt of phenoxymethyl penicillin in a suitable reaction medium ls reacted with chloromethyl methyl ether or bromomethyl methyl ether at a temperature '> between about 0° C. and 50° C. and preferably between 0° C. and 30° C. A preferred reaction medium is / methylene chloride to which may be added some dimethylformamide generally in a ratio of about 1 to 2 ml. per 150 ml. of methylene chloride. Dimethylformamide can 10 also be used as a reaction medium. The reaction product can be recovered by conventional methods.

The recovered ester of phenoxymethyl penicillin is then deacylated, either enzymatically or chemically. EnZvmatic production of 6-amino penicillanic acid (6-APA) hy deacvlation of a penicillin is disclosed in United States Patent 3,014,846.

The preferred method of chemical cleavage is carried out by forming an imino halide by reaction with a halogenating agent, such as phosphorous pentachloride. The ester is dissolved in a non-aqueous solvent, such as methylene :'J chloride, bensene or chloroform, to which there has been added a suitable amount of an acid-binding agent, such as dimethylaniline, pyridine, quinoline, or lutidine. The amount of acid-binding agent should be sufficient to take up the acid formed by the cleavage reaction. The J chlorination reaction temperature should be maintained between about -50° C, to Q° c. to provide complete chlorination of the ester. The imino chloride is then treated with an alcohol under acid conditions whereby -114 i S 3 6 an imino ether is formed under anhydrous conditions.

Water is then added to the reaction mixture to hydrolyze the ether. The imino ether can conveniently be formed at temperatures of from -70° C. to -3O°C.

The general procedure for this series of reactions is disclosed ln United States Patent 3,499,909, along with various halogenati^g agents, acid-binding agents, alcohols, and solvents all of which are generally applicable to the herein disclosed methoxymethyl esters. lo Thus, the 6-APA ester can be isolated from the reaction mixture as the free base or as an acid addition salt such as the p-toluene-sulfonate salt.

Acylation of the 6-APA ester to provide the methoxymethyl ester of amoxicillin can be achieved 15 following known procedures, such as those disclosed in United States Patents 2,985,648 and 3,140,282.

The above-mentioned p-toluenesulfonate salt of the methoxymethyl ester of 6-APA is then contacted with an acylating agent, 3uch as D-(-)-2-p-hydroxyphenyl20 glycyl chloride hydrochloride, in either anhydrous methylene chloride or in an acidic aqueous medium at low temperature. Broadly, the acylating agent ia employed in amounts of about 1 to 3 moles per mole of 6-APA, and the temperature should be between -10° c. and + 20° C. The pH of the reaction medium should be below 4 and preferably from 1.5 to 3.0, usually between 2.0 and 2.8. The reaction medium is often a mixture of water and organic solvents such as acetone, methylene chloride, or tetrahydrofuran. The -1241636 acylated ester is recovered by raising the pH of the reaction medium to about 4 or above, e.g., between 4 and 7. Any solids are removed by filtration to provide a solution of the amoxicillin, ester. / > In a preferred procedure, the ester is dissolved in methylene chloride-acetone mixture at ice bath temperatures generally between o°c. and 5° c. Λ small amount of water, about 2.5/ based on the volume of the organic solvent, is then added, preferably in J , about stoichiometric amounts. The resulting admixture is maintained at about 0° C. until the acid chloride has dissolved. The reaction product can then be recovered by standard methods. This reaction can be run under anhydrous conditions.

The amoxicillin methoxymethyl ester is then converted to the corresponding p-hydroxy-hetacillin ester by reaction with aqueous acetone at a pH of from about 6.5 to 9,5. In general, this step of the process ls carried out at a temperature between -10® C. and 15° C., although it is generally preferred to employ temperatures of 0°C. to 5°c.

The pH and temperature should be maintained for a period of time which is sufficient to provide substantial conversion to p-hydroxy-hetacillin, e.g,, from 12 to 170 hours, depending on the other conditions.

After the reaction period, the p-hydroxy-hetacillin methoxymethyl ester is recovered by adjusting the pH of the reaction mixture to between 1,5 and 2,0 with -1 j4163® . an acid suclj as hydrochloric acid and extracting with a suitable solvent such as methylene chloride, lhe phydroxy-hetacillin ester Is recovered from the organic phase In the usual manner, A useful embodiment of the process of this invention is a continuous series of reactions carried out without isolation or recovery of intermediates. For example, the potassium salt of phenoxymethyl penicillin is esterified with bromo- or chloro-methyl methyl ether in methylene chloride at a temperature between 0° C. and ° C. The methylene chloride solution of the ester is then successively treated with phosphorus pentachloride, methyl alcohol, and water to complete removal of the phenoxymethyl side chain and provide a methylene 15 chloride solution containing the methoxymethyl ester of 6-APA, This solution is then carried forward and used in the acylation reaction in which D-(-)-2-phydroxyphenylglycyl chloride hydrochloride is added to the solution to give a methylene chloride solution of the amoxicillin ester. In the final step, the solution of amoxicillin ester is treated with acetone at pH 7.5 to 8.5 and held until p-hydroxy-hetacillin ester formation has proceeded.

The following examples are given in illustration of, but not In limitation of, the present invention.

Methyl isobu-fcyl ketone is represented as MIBK. -1441636 Example 1 Methoxymethyl Ester of Penicillin V. 38.8 grams potassium phenoxymethylpenicillinate were slurried in 150 ml. of methylene chloride and the mixture cooled to about 5° C. by means of a cooling bath. 9.5 grams (0.118 mole) of chloromethyl methyl ether and 0.5 ml. of dimethylformamide were added. The cooling bath was removed and the mixture was stirred for about 1.5 hours while allowing it to come to room temperature. The methylene chloride solution was washed four times with 200 ml. portions of water and then dried and stripped of solvent by distillation in vacuo to give 33.5 grams of methoxymethyl ester of penicillin V as a yellowish oil. The yield was about 84%.

Example 2 1 ’’ Preparation of Pen V Methoxymethyl Ester. 32.12 q. (0.257 mole) of bromomethyl methyl ether in ml. dichloromethane were added over a period of about ten minutes to 100 g. (0.257 mole) of K Pen V (potassium phenoxymethylpenicillin) slurried in 300 ml. of dry dichloromethane and cooled to 0-5° C. After the addition, 1 ml. of DMF (dimethylformamide) was added and the reaction was allowed to proceed for 3 hours at a temperature of 0-5° C. TLC (thin layer chromatography) (50/50 acetone/benzene) showed a major zone for product, Rf about 0.7.

The reaction mixture was washed with 3 x 100 ml. portions of water, dried over MgSO^ and concentrated to an oil under reduced pressure and at a temperature of about 40° C.

The oil was taken up in 300 ml. of 2-propanol at about 25° C., seeded and crystallized for 12 hours at 0-5° C. The white 0 crystals were collected by filtration, washed with 2-propanol followed by heptane, and dried in a vacuum oven at a temperature -1541S3S of about 25° C. and for about 4 hrs. 68 g. (about 67¾ yield) of Pen V methoxymethyl ester were obtained. This product was homogeneous on TLC and showed consistent and clean IR (infrared) and NMR (nuclear magnetic resonance) spectra.

Example 3 6-APA Methoxymethyl Ester as its p-Toluenesulfonate. ml. of Ν,Ν-dimethylaniline, followed by 33.1 g. of phosphorous pentachloride were added to 57 g. (0.145 mole) of Pen V methoxymethyl ester dissolved in 500 ml. CHjC^ and cooled to -30° C. The mixture was stirred at -30° C. for 90 minutes. TLC showed almost no residual methoxymethyl ester of Pen V. The mixture was cooled to about -60° C. and 150 ml. of precooled (-50° C.) methanol were added in one portion. The temperature was then held at about -40° C. for 2 hours. The solution was then added rapidly to 150 ml. of 0-5° C. water and held for 10 min. at 0-5° C. The pH was about 0.8.

While maintaining this temperature range, 10% NaOH solution was used to adjust the pH to 6.9. The layers were separated and the dichloromethane layer washed with 3 x 100 ml. portions of cold water. After drying over magnesium sulfate, the CH2CI2 layer was concentrated under vacuum to about half volume and 54 g. (0.284 mole) of p-toluenesulfonic acid dissolved in 120 ml. of acetone were added. Seed crystals of product were added and the mixture crystallized at 0 to 5° C. for 2 hrs.

After collecting by filtration, washing with 100 ml. of 50/50 CH2Cl2/heptane and drying for 4-6 hrs. in a circulating air oven at a temperature of about 30° C., 23.7 g. (37.8% yield) of the p-toluenesulfonic acid salt of 6-APA methoxymethyl ester were obtained. -160 Example 4 6-Aminopenicillanic Acid Methoxymethyl Ester. 4.8 ml. (4.6 grams, 0.038 mole) of dimethylaniline, followed directly by 7.0 grams (0.0337 mole) of phosphorous pentachloride dissolved in 100 ml. of methylene chloride, were added to a solution of 12 grams (0.0304 mole) of penicillin V methoxymethyl ester in 100 ml. of methylene chloride cooled to -55° C.

The mixture was held at -40° C. to -50° C. for about 10 2 hours. Thin layer chromatography indicated complete chlorination of the Pen V ester. The mixture was then cooled to -70° C. and 47 ml. of methanol, precooled to -50° C., were added rapidly. The mixture was then held for 2 hours at -50° C. to -40° C.

To the resulting yellow solution, 100 ml. of water were added with vigorous agitation. The temperature of the reaction mixture rose to about 0° C., and the pH of the mixture was about 0.6 to 1.0. After holding the mixture for about 10 to 15 minutes at this temperature and pH range, the pH was brought to 6.5 to.6.8 with dilute sodium hydroxide. The layers were separated and the methylene chloride layer was washed with water, carbon treated, and dried to yield the desired methoxymethyl 6-aminopenicillinate. Thin layer chromatography showed that this solution contained dimethylaniline, methyl phenoxyacetate, and 6-APA methoxymethyl ester.

Example 5 Amoxicillin Methoxymethyl Ester. 2.16 g. (0.005 mole) of the p-toluenesulfonic acid salt of methoxymethyl 6-aminopenicillanate, followed by 0.7 ml. (0.005 mole) of triethylamine, were added to 30 ml. of dry CH2C12 ii) at 0 to 5° C. To the resulting clear solution was added 0.64 ml. (0.005 mole) of dimethylaniline, followed by 1.33 g. (0.005 0i@36 mole) of D-(-)-p-hydroxyphenylglycyl chloride hydrochloride hemidioxane solvate added in about 5 min. After about 1 to 1.5 hr., when nearly all the solid acid chloride had dissolved, the reaction mixture was quenched into 30 ml. of cold water.

The pH was brought to 3.0 using sodium bicarbonate solution and the layers separated. While maintaining a pH of 3.0 and a temperature of 0 to 5° C., the water layer was further washed with 4 x 30 ml. of CH2C12· This served to remove most of the dimethylaniline and left the product in the H2O. Using NaHCC>3, the water layer was then adjusted to pH 7.5 and extracted with 2 x 30 ml. CH2CI2· The combined CH2CI2 layers were washed with 2 x 20 ml. H2O, dried over MgSC>4 and concentrated under reduced pressure at /40° C. to give amoxicillin methoxymethyl ester as a friable, foamy solid weighing 1.82 g. (about 88% yield), homogeneous on TLC, and having infrared and 100 MHz NMR spectra consistent for the methoxymethyl ester of amoxicillin.

NMR: CD2C12+ CD3OD solvent /l.58 (6H, d, <^3 ), 3.5 (3H, s, OCH3), 4.5 (2H, overlapping singlets, C-3 and phenyl glycyl H), 5.35 (3H AB quartet, O-CH2-O plus some CH2Cl2 in solvent), 5.6 (2H, AB quartet, β-lactam H2, 6.9 (4H, AB quartet, aromatic H).

A 20 mg. sample of the ester was dissolved in 10 ml. of 50/50 acetone/pH 7.0 buffer and showed a bioassay of 1968 meg./ml. of amoxicillin (about 110% of theory).

Example 5A p-Hydroxyhetacillin Methoxymethyl Ester 500 mg. of amoxicillin methoxymethyl ester were dissolved in ml. of 50/50 acetone/^O, the pH was raised to 9.2 with 10% NaHCOg and the clear, solution was aged at 0°-5°C. for 16 hours. Thin layer chrome tography (50/50 CgHg/acetone){det. KMnO^) showed complete conversion to ρ-hydroxyhetacillin methoxymethyl ester. The acetone was removed under vacuum and the aqueous phase then extracted with 3 x 30 ml portions of CHgClg. The combined extracts were washed with 2 χ 20 ml. of H20, dried and stripped to foamy solid. Yield: 420 mg. 77% recovery. NMR (100 MHz) showed hydroxyhetacillin methoxymethyl ester and dimethylaniline The NMR spectra was generally consistent, showing approximately 80% pure p-hydroxyhetacillin methoxymethyl ester. - 18 41636 Example 6. p-llydroxylitft ac11 11 n Met hoxymetliyl Ester llydrochlor tele g. methoxymethyl p-hydroxyhetacillin were dissolved in 80 ml. of dry acetone and 6 ml. of 13% hydrogen chloride in 2-propanol were added. The resultant solution was then poured rapidly into 1,000 ml. of well stirred diethyl ether.

After 5 minutes of vigorous agitation, the resulting solid was filtered and washed with 100 ml. of ether. After drying 3 hours at a temperature of 30° C to 35°C. there were obtained 10 g. (93% yield) of the title compound having consistent IR and NMR spectra.

Example 7.

Amoxicillin Methoxymethyl Ester Hydrochloride. g. of amoxicillin, 20 g. of Linde type 4A molecular sieves and 6.6 ml. of triethylamine were slurried in 200 ml. of dichloromethane. After stirring for about 1 hour at a temperature of 0°C to 5°C., the mixture was treated with 3.8 ml. of chloromethyl methyl ether, and stirred an additional 2 hours at 0°C. to 5°C. The mixture was filtered and the clear filtrate washed with two 100 ml. portions of water at pH 7.0 to 7.5. The organic layer was then dried, treated with about 1 g. of decolorizing carbon, filtered, then concentrated to a foamy solid, under reduced pressure and at a temperature of 30°C.to 40°C. IR and NMR spectra indicated about 10 to 15% of unchanged starting amoxicillin and a slight excess of methoxymethyl groups suggesting some over-alkylation at the phenolic hydroxyl group or the amino group. 6 g. of the product were dissolved in 60 ml. of dry acetone, cooled to a temperature of 0°C. to 5°C. and 6 ml. of 13% HCl in 2propanol were added. The resultant solution was rapidly added to 600 ml. of well stirred ether and after 5 minutes the resulting solid was filtered, washed with ether and dried for 3 hours at a temperature of 25°C. to 30°C. 6 g. (91.5% yield) of amoxicillin methoxymethyl ester hydrochloride were obtained as an amorphous solid with IR and NMR spectra consistent with the structure and showing a small amount of acetone. - 19 Example 8 Preparation of Crystalline Methoxymethyl 6-[D-(-)-2,2-Dimethyl4-(4-hydroxyphenyl)-5-oxo-l-imidazolyl]penicillanate. 6.72 ml. (0.054 mole) of triethylamine, followed by g. of Linde 4A molecular sieves, were added to a stirred suspension of 24.3 g. (0.06 mole) of 6-[D-(-)-2,2-dimethyl-4-(hydroxyphenyl) -5-oxo-l-imidazolyl]penicillanic acid (p-hydroxyhetacillin) in 400 ml. of CH2CI2. The resultant mixture was stirred for one hour and then filtered. The filtrate was stirred and cooled at -15° C. while 0.054 mole of bromomethyl methyl ether was added dropwise over a 5 minute period. After stirring for 30 minutes at a temperature of -15° C., the solution was extracted with six 100 ml. portions of H2O. The CH2CI2 solution was then dried for ten minutes over Na2SC>4 and filtered. The filtrate was evaporated under reduced pressure and at a temperature below 20° C. to give an oil which began to crystallize. The partially crystalline mass was dissolved in 50 ml. of CH2CI2 and diluted to the cloud point with n-heptane. Scratching induced crystallization and after one hour at 22° C. the crystals were filtered off and discarded. The filtrate (mother liquor) was then diluted with 400 ml. of n-heptane and cooled in an ice bath. The oil which separated was then triturated with Skellysolve B (trademark of Skelly Oil Co.) which is a petroleum ether fraction of b.p. 60-68° C. consisting essentially of n-hexane. This left a gummy material which was dissolved in a minimum amount of CH2CI2. Almost immediately crystallization began. About two thirds of the CH2CI2 was removed in vacuo and after standing for two hours the crystals were collected by filtration and air dried to give 3.3 g. of product. A total of 3 g. of this material were recrystallized by dissolving it in 20 ml. of acetone, filtering and carefully diluting to the cloud point -2041636 with n-heptane. Tho product, crystalline methoxymethy 1 (>-|P(-)-2,2-dimethy1-4-(4-hydroxypheny1)-5-oxo-l-imidazolyl]penicillanate, was allowed to crystallize in large needles for two hours at 22° C., then two hours at 13° C., (cold room) and two hours at about 4° C. (ice bath). The crystals were then collected by filtration, washed with 3:2 n-heptane:acetone, then Θ n-heptane and air dried. 2.03 g. of product having m.p. 112113° C. were obtained. The IR and NMR were consistent with the desired structure indicating a purity of at least 90%.

O Anal. Calcd. for C21H27N3O6S: C, 56.04; H, 6.00; N, 9.33.

Pound: C, 55.49; II, 5.96; N, 9.18; (uncorrected for 1.567, HoO as determined by the Karl Fischer method). -21The following data is provided to further illustrate the present invention: Table I, below, shows minimum inhibitory concentrations, in micrograms per ml., for the acetone adduct of the methoxymethyl ester of phydroxyamplclllin (also called the methoxymethyl ester of p-hydroxyhetacillin; Cpd. B) against various organisms as compared to the minimum inhibitory concentratioft of ampicillin (Cpd , A).

TABLE I Organism Compounds A B D. pneumoniae + 5$ serum .004 .004 Str. pyogenes + 5$ serum .004 .004 S. aureus Smith .05 .06 S. aureus Smith + 50$ serum .06 .06 S. aureus BXl6?? 125 125 S. aureus BXl6?? >125 >125 S. aureus 125 125 S. aureus 125 125 S. aureus >125 >125 Sal. enteritidis 0.1? 0.1? E. coli Juhl 1 1 E. coli 52 52 K. pneumoniae 0.5 0.16 K. pneumoniae 125 >125 Pr. mirabilis 0:16 0.16 Pr. morganii >125 ?2 Ps. aeruginosa >125 >125 Ser. marcescens 52 ?2 -2241636 Table II, below, shows some illustrative blood level data for the methoxymethyl ester of p-hydroxy-hetacillin (compound 1) after oral administration to mice as compared to ampicillin (compound 2) and hetacillin (compound 3).

TABLE II Blood Levels after Oral Administration to Mice Compound Dose (mg./kg.) Blood Levels (ug/ml) 0.5 Hours 1 after 5-5 Administration 1 50 4.8 5.5- 1.7 • 7 2 50 5-5 2.1 0-9 • 5 '3 50 2.0 1.8 1.1 • 5 In the treatment of bacterial infections in mammals, e.g. man, the compound of this invention is administered orally or parenterally, in accordance with conventional procedures for antibiotic administration, in an amount of from 5 to 200 mg./kg. of body weight/day and preferably 5 to 20 mg./kg. of body weight/day, in divided dosage, e.g., three - to four times a day. It is administered in dosage units containing, for example, 125 or 250 or 500 mg. of active ingredient with suitable physiologically acceptable carriers or excipients. The dosage units are preferably in the form of liquid preparations such as solutions or suspensions or as solids in tablets or capsules.

The present invention thus includes within its scope a pharmaceutical or veterinary composition which comprises as active ingredient a compound of Formula I, or a pharmaceutically acceptable salt thereof, together with a physiologically acceptable carrier or excipient.

The present invention also includes within its scope a method for treating bacterial infection in a nonhuman mammal which comprises administering to the mammal a compound of formula I, or a pharmaceutically . acceptable salt thereof, or a composition containing as active ingredient a compound of formula I, or a pharmaceutically acceptable salt thereof, together with a physiologically acceptable carrier or excipient, in an amount sufficient to . combat the infection.

Claims (26)

1. A compound of the formula (I) having the D-configuration at the carbon atom marked 5 with an asterisk.

• 2. A pharmaceutically acceptable salt of a compound as claimed in claim 1.

3. The hydrochloride of the compound of claim 1.

4. A process for preparing a compound as claimed in 10 claim 1, or a pharmaceutically acceptable salt thereof, which process comprises the consecutive steps of a) forming a penicillin ester of the formula wherein R is an organic radical, 15 b) deacylating said penicillin ester to form methoxymethyl 6-aminopenicillanate, c) reacylating said methoxymethyl 6-aminopenicillanate with the acyl moiety of D-(-)-2-£-hydroxyphenylglycine to produce the methoxymethyl ester of amoxicillin, 20 d) reacting said methoxymethyl ester of amoxicillin with acetone to produce the methoxymethyl ester of phydroxyhetaoillin, and -- 26 41636 e) if desired, converting said methoxymethyl ester of £-hydroxyhetacillin into a pharmaceutically acceptable salt thereof according to known methods.

5. Λ process as claimed in claim 4 wherein R is a phenoxymethyl group.

6. A process as claimed in claim 4 or claim 5 wherein step d) is conducted at a pH in the range of 5 .5 to 9.5.

7. A process as claimed in claim 4 or claim 5 wherein step d) in conducted at a pH in the range of 7.5 to 9.5.

8. A process as claimed in claim 4 wherein the methoxymethyl ester of 6-aminopenicillanic acid is acylated with an acid in the D-configuration having the formula 1 2 wherein R is an alkyl, aralkyl or aryl group, R is a hydrogen atom, an alkyl, aralkyl or aryl group and R^ is an alkyl, aralkyl, aryl, alkoxy, aralkoxy or aryloxy group or the group -N Z R J X R 5 in which R^ and R^ are each a hydrogen atom, an alkyl, aralkyl or aryl group or, when taken together with the nitrogen atom, represent a piperidino or morpholino group, or an acylating derivative thereof, in an inert solvent, at a temperature below 0°C,. and then the α-amino-protecting group is removed.

9. A process as claimed in claim 8 wherein the acylation - 27 41636 of said methoxymethyl ester of 6-aminopenicillanic acid is carried out in the presence of a catalyst of the formula ^h 2 x wherein X is a hydrogen atom or an alkyl or phenyl group, Y is a hydrogen atom or a lower (C^-C^) alkyl group, or X and Y together represent an ethylene,substituted ethylene, trimethylene, -CH 2 OCH 2 ~ or -ch 2 n(ch 3 )ch 2 group.

10. A process as claimed in claim 9 wherein the catalyst is N-methylmorpholine or Ν,Ν-dimethy Ibenzy lamine.

11. A process ,as claimed in any one of claims 8 to 10 wherein the inert solvent is acetone, aqueous acetone or tetrahydrofuran.

12. A process as claimed in any one of claims 8 to 11 wherein the acylating derivative is a mixed anhydride formed from an alkyl chlorocarbonate.

13. A process as claimed in any one of claims 8 to 12 wherein in the en-amine amino-protecting group, R^ is a methyl group, 2. 3 R is a hydrogen atom and R is a methoxy,ethoxy or methyl group.

14. A process as claimed in any one of claims 8 to 13 wherein the α-amino-protecting group is removed by contact with a strong mineral acid.

15. A process as claimed in claim 14 wherein the strong mineral acid is hydrochloric acid or formic acid.

16. A process as claimed in any one of claims 8 to 15 wherein the reaction in step (d) is effected in the presence of at least a one nole excess of acetone.

17. A process for the preparation of a compound of formula X as claimed in claim 1 substantially as hereinbefore described.

18. A process for the preparation of a compound of Formula I as claimed in claim 1 substantially as,hereinbefore described with reference to any one of the specific Examples. - 28 41636

19. A compound of formula I as claimed in claim 1 when prepared by a process as claimed in any one of claims 4 to 18.

20. A pharmaceutical or veterinary composition which comprises as active ingredient a compound as claimed in claim 1 or claim 19, or a salt as claimed in claim 2 or claim 3 together with a physiologically acceptable carrier or excipient.

21. A pharmaceutical or veterinary composition as claimed in claim 20 which is in dosage unit form.

22. A pharmaceutical or veterinary composition as claimed in claim 21 wherein the dosage units contain 125 mg, 250 mg, or 500 mg of the active ingredient.

23. A pharmaceutical or veterinary composition as claimed in claim 21 or claim 22 wherein the dosage units are tablets or capsules.

24. A method for treating bacterial infection in a nonhuman mammal which comprises administering to the mammal a compound of formula I, or a pharmaceutically acceptable salt thereof, or a composition as claimed in claim 20 in an amount sufficient to combat the infection.

25. A method as claimed in claim 24 wherein the compound or salt is administered orally or parenterally in a total daily dose of from 5 to 200 mg per kg. of body weight of the mammal.

26. A method as claimed in claim 24 wherein the compound or salt is administered orally or parenterally in a total daily dose of 5 to 20 mg per kg. of body weight of the mammal.