IL35801A - 3-hydroxy-3-methyl cepham-4-carboxylic acid compounds - Google Patents

Description

-HYDROXY - 3 -ME THYL C EPHAM -4 -C ARBOXYLIC ACID COMPOUNDS 35801/2 This invention provides new compounds of the formula wherei R is hydrogen, thienylacetyl, or an acyl group of the formula wherein m is an integer of from O to 4 inclusive, n is an integer of from O to 4 inclusive, z is O or 1, and when Z is O, the methylene groups in m and n are connected by a chemical bond, and such acyl groups substitued on phenyl carbon atoms thereof with fluorine, chlorine, bromine, iodine, nitro, to Cg alkyl, C^ to Cg alkyloxy, or trifluoro-methyl, and R is an ester group selected from the group consisting of 2, 2, 2-trichloroethyl C to Cg ,-tert -alkyl Cg to C^-tert alkenyl Benzyl nitrobenzyl or methoxybenzyl, hydrogen or a salt-forming cation Further this invention provides a new process for preparing the 3 -hydroxy-3 -methyl- 7amino-cepham acid and ester compounds from the corresponding penicillin sulfoxide acid or ester.

The semi- synthetic production of 7-acylamido-desacetoxy-cephalosporin antibiotics from penicillin starting materials has become of importance recently, due to the process invention of Morin and Jackson (US Patent 3, 275, 626) who describes a process for converting penicillin sulfoxide esters to desacetoxycephalosporanic acid esters and to the improvements on that Morin- Jackson process by Chauvette and Flynn who in the process in that they were more easily cleaved than those employed by Morin and Jackson. Further improvements of the Morin-Jackson process were found by Robin D.G.

Cooper who found that the use of certain tertiary carbox-amide, urea, or sulfonamide solvents directed the heat rearrangement of the penicillin sulfoxide esters more specifically toward production of the corresponding des-acetoxycephalosporin esters. Some of the 7-acylamidodes-acetoxycephalosporanic acid compounds have been found to haye unique properties as antibiotics in their own right. For example, cephalexin, 7- 5"-alpha-aminophenylacetamid£7-3-methyl cephem- -carboxylic acids zwitterion and pharmaceutically acceptable cationic and anionic salt forms thereof, are useful as oral antibiotics in combatting infections caused, e.g., by penicillin resistant strains of Staphylococcus aureus, and many other Gram positive and Gram negative microorganisms.

One of the unique advantages of -desacetoxy cephalosporin compounds, that is, compounds of the general formula wherein R is the residue of the acylamido group in the 7-position, and R 1 is hydrogen, a salt forming cation, an ester group, or an anionic charge when the COO- forms a salt with a cation either within or outside of the molecule, is that such compounds can now be prepared from penicillin sulfoxide esters by the Jtorin-Jackson process, especially as Improved by the Chauvette-Flynn and R.D.G. Cooper improvements.

Lowell D. Hatfield disclosed his invention for an improved process for the direct preparation of a des— acetoxycephalosporin ester by the patented Morln-Jackson process as improved by the Cooper solvent systems.

Hatfield discovered that by using a combination of a sulfonic acid and a water removal means during the step of heating the penicillin sulfoxide ester starting material, higher yields of the desired desacetpxycephalosporin esters were obtained. However, small yields of previously unidentified residues were also prepared.

In the practice, the penicillin sulfoxide acid, salt or ester is heated in the presence of sulfuric acid, sulfamic acid, or a salt or ester thereof to a temperature of from about 80°C. to about 150°C. dissolved in a solvent medium containing at least about 10, percent by volume of a tertiary carboxamide until an optimum yield of the 3-hydroxy-3-methyl-7-amino-cepham- -carboxylic acid or ester is formed. Generally, the reaction is completed withi about 24 hours. With preferred solvents and reactants good yields of product have been obtained after heating the mixture for from 5 to 14 hours. Under the preferred conditions,- the penicillin sulfoxide acid or ester is dissolved to ,a concentration of from about, 1 to about 20 percent by weight in a solvent mixture containing the tertiary carboxamide and organic inert liquid in the optimum proportions of from about 3:5 to about 5:3 parts of volume of the tertiary carboxamide; organic inert 3S801/2 liquid. The proportions of solvent components and concentration of penicillin sulfoxide will vary somewhat, however, with the choice of tertiary carboxamide, any organic inert liquid,, and the selected temperature and time of reaction. It has been found that with the preferred tertiary carboxamide, Ν,Ν-dimethylacetamide (DMA) , as the proportion of the organic inert liquid cosolvent is varied from the proportions given above, the yield and nature of the reaction mixture is changed.

Any prior art penicillin, or 6-(N-protected-amino)-2,2-dimethylpenam-3-carboxylic acid compound which is not otherwise converted under the conditions of acidit and elevated temperature employed herein, can be used as a starting material to prepare compounds within the scope of this invention. The penicillin or penam must be oxidized to the sulfoxide state prior to treatment. It can also be esterified to protect the carboxyl group in subsequent reactions, but need not be esterified for preparing the compounds of this invention. Alternatively, the penicillin or penam can be esterified and then oxidized to the penicillin sulfoxide ester. A wide range of penicillins and penam compounds can be treated to obtain the 3-hydroxy-3-methyl-cepham compounds of this invention. Penicillins sulfoxide salts with alkali metals particularly sodium, potassium, ammonium, and amine salts can also be used but are not necessary. 35801/2 when the nitrogen.i the 7-position is in the free amino state, the yields of the desired product are substantially lower. The..R group can be an acyl group. Many. acyl groups suitable. for this purpose are already known in the penicillin and cephalosporin antibiotic literature. The. acyl group has the formula wherein m is an integer of from 0 to 4 inclusive, n is an integer of from 1 to 4 inclusive, z is 0 or 1, and when Z is O, the methylene groups in m and ί are connected by a chemical bond, and such acyl groups substituted on phenyl carbon atoms with fluorine, chlorine, bromine, iodine, nitro to Cj-alkyl, to C2-alkyloxy, or trifluoromethyl groups.

The acyl groups can also have methyl groups in place of 1 or 2 of the hydrogens on the carbon atoms i the m or n groups. A few representative examples of such preferred acyl groups include: phenylacetyl phenoxyacetyl phenylheptanoyl phenoxyisopropionyl benzyloxyacetyl phenylpropionyl phenylbutyr^l 3- methylphenylbutyryl 4- propylbenzylacetyl benzyloxyacetyl phenylethoxypropionyl phenylbutoxybutyryl 3-f luorophenoxyacetyl 3- hydroxyphenylacetyl 4- bromopheny,lpropionyl 4-iodophenylacetyl 2-chlorobenzyloxypropionyl, phenyl-2 -2 -dimethylacetyl 4-nltrophenylacetyl 3 - cyanophenylpropiony 1 4- trif luoromethylphenoxyacetyl, and the like.

Numerous other compounds which form amino protecting groups which can be used in the R position are known in the prior art, e.g., those ; disclosed in the Behrens et al U.S. Patents 2, 79,295 to 2,479,297 and 2,562,407 to 2,562,411, and 2,623,876.

The R4 symbol in the general formula describing the Compounds of this invention can be hydrogen, a water soiubilizing salt such as an alkali metal, or quaternary amine, or the residue of an ester. The ester group should be one which is removable by known methods such as by dilute aqueous base or by the use of trif luoroacetic acid, acetic acid, and zinc dust, hydrogenatlon in the presence of an appropriate catalyst such as palladium, platinum, or rhodium on a suitable carrier such as carbon, barium sulfate, or alumina so that the cephalosporin compound is not degraded. The preferred ester groups are 35801/2 C4 to Cg-tert-alkyl, C5 to C7-tert-alkenyl, Cg to C7-tert-alkynyl, such as tert-butyl , tert-pentyl, .1 ,l-dimethylr-2-propenyl', lyl-dimethyl^2-pentynyl, 2,2,2-trichlbroethyl, benzyl, 3- or 4--m^¾hoxybenzyl,; 3-. or.4-nitrobenzylj and. -Cfi^R" groups where R" is i to C^-alkanoyl, benzoyl , toliioyl, thenoyl or furoyl, as set forth in U.S.Patent. ,3,284,451, or benzhydryl and the like.

Compounds of this invention where R is hydrogen, can be obtained after the penicillin sulfoxide rearrangement reaction has been complete and are formed by subect-ing. the 3-hydroxy-3-methyl.-7racylamido-cepham-4-carboxylic acid or ester to the action of phosphorus pentachloride in the presence of. an equivalent amount of a tertiary amine such as pyridine, followed by a lower alkanol, e.g., methanol, and then by water to cleave the 7-acyl group.

Examples of such a product are 3-hydroxy-S-methyl-7-amino-cepham-4-carboxylic acid and tert-butyl 3-hydroxy-3-methyl-7-amino-cepham-4-carboxylate.. Such compounds can be recovered from their reaction mixtures by conventional methods, e.g. as a salt with a to -hydrocarbon^ sul onic acid which salt precipitates from most organic solvents . Such compounds also form salts with strong acids having a pKa of less than 4 such as hydrochloric, sulfuric, orthophosphoric, nitric, iodic, perchloric acids and the like. If desired 6-aminopenam- 3-carboxylic acid such as 6-aminopenicillanic acid (6-APA) , and esters thereof such as 2, 2 ,2-trichloroethyl 6-amlno-2,2-dimethylpenam-3-carboxylate can be converted by the process of this invention to the corresponding 7-amino 3-hydroxy-3-methylcepham-4-carboxylate acid, or ester, but it is preferred to use a penam in which the amino group is protected as indicated above.

The concentration of the sulfuric acid, sulfamic acid, or equivalent salt, or ester will vary depending upon the nature of the acid substance, the concentration of the penicillin or penam sulfoxide ester, the solvent system used, the desired time of reaction, and the like. In general, the molar ratio of penicillin sulfoxide, to acid ranges from about 1: 1 to about 50: 1. Preferably a molar ratio of penicillin sulfoxide ester to acid ranges fr»om about 5 : 1 to about 15 : 1. The concentration of the penicillin sulfoxide ester in the total solvent system can vary extensively but ^preferably constitutes from about 1 to about 20 percent by weight of the reaction mixture .

The penicillin or penam sulfoxide acid, salt, or ester in the acidified solvent system is heated to from about 80°C. to about 150°C. to direct the rearrangement of the penicillin sulfoxide ester to the 3-hydroxy -3-methy 1-7-amino-cepham compound. In the preferred tertiary car-boxamide containing solvents, or solvent mixtures, the preferred heating temperature is from about 90°C. to about 130°C., for from about 2 to about 24 hours. Lower temperatures require more time, while at higher temperatures the reaction mixture tends to produce a more complex reaction product mixture.

In preparing the compounds of this invention, the tertiary carboxamlde can be used as the only solvent system, but for optimum yields, it will often be desirable to dilute the tertiary carboxamlde with an inert organic liquid. In preparing these compounds it is not necessary to choose the inert organic liquid on the basis, of whether or not it forms an easily removed azeotrope with water, as was desirable in the Hatfield process, mentioned above. However, those same organic liquids can be used as diluents for the tertiary carboxamlde solvent in the process of preparing these new compounds.

Thus, the inert organic liquids can be exemplified by hydrocarbons, especially to Cg-alkanes and Cg to CQ-aromatic hydrocarbons, halogenated hydrocarbons, particularly those containing from 1 to 6 carbon atoms and from 1 to 4 chlorine or bromine atoms, as well as ethers,-esters, nitrlles, and the like, as set forth in various chemistry handbooks, e.g., Handbdok of Chemistry, edited by N.A. Lange, Ninth Edition (1956), pμblished,by Handbook publishers, Inc., Sandusky, Ohio, pp. 1484 to to i486, and 1493, and in the Chemical Rubber Co., Handbook of Chemistry and Physics, 45th Edition, pp. D-l to D-18 (1964-65).. Examples of suitable diluents include pentane, hexane,, heptane, benzene, toluene, xylene, methylene chloride, chloroform, carbon tetrachloride, 1,2-dichloroethane, methyl, ethyl ketone, methyl isobutyl ketone, ethyl acetate, isopropyl acetate, n-propyl acetate, propylene glycol diacetate, acetonitrile, proplo-nitrile, dioxane,. diglyrae, and the like. The tertiary carboxamlde :·. should constitute at least about 10 percent 4» by volume of the reaction mixture . The diluting organic liquid or liquids forms the remainder of the solvent sys tem .

The general types of tertiary carboxamides which can be used have the structural f ormula 0 Ri -C-N-Rp I ... .. R3 wherein (1) R^ is hydrogen, and each of R2 and R^ Is alkyl, phenyl, tolyl, or xylyl such as R2 and R^ together contain up to about 14 carbon atoms j (2) at least one of R^, R2 and R^ is alkyl, and riot more than two of R^, R2 and R^ are phenyl, tolyl, xylyl, and R R≥ and R^ together contain up to about 18 carbon atoms ; (3 ) Rj_ is hydrogen or alkyl, R2 and R^ are taken together with the nitrogen to which they are bonded to form a saturated monocyclic ring which contains from 4 t o, 6 carbon atoms in the ring, which ring can also contain an oxygen ring member, gamma to the ring nitrogen, and R^, R2 , and R3 together contain not more than 12 carbon atoms ; and /or (4 ) R^ and R2 are taken together with the amide 0 II grouping (-C-N-) . to which they are bonded to form a sat urated carbonyl containing monocyclic ring having from 4 to 6 ring, carbon atoms, R^ is alkyl, phenyl, tolyl, or xylyl, and R^, R2 , and ^ together c ontain not more than 14 carbon atoms .

Examples of tertiary carboxamides of the types described above, which may be used in the process include: (1) N,N-dimethylforman|ide (DMF), N,N-diethyl-f ormamide, Ν,Ν-diisopropylf ormamide, N, N-d ibuty If ormamide , N, N-d ipenty If ormamide, N-methyl-N-ethylf ormamide, N-methyl-N-pheny If ormamide, N-ethyl-N- (m-tolyl)f ormamide, N-propyl-N- (3,5-dimethylphenyl), N, N-d ipheny If ormamide, N,N-bls (4- . methylphenyl)f ormamide, N- (3, 5 -dimethyl) -N-met hy If ormamide, N,N-bls (2, 4-dimethylphenyl)f ormamide, and the like; (2) Ν,Ν-dimethylacetamide (DMA), N,N-diethyl-acetamide, N, N-d lis opropy lace t amide, N, -dibutylacet amide, N, N-dl-tert-butyl-acet amide, N,N-dimethylpropionamide, N, N-diethylpropionamide, Ν,Ν-dipentylpropionamide, N, N-dimethylbutanoamide, N,N-diethylbutanoamide, N, N-d ime thy 1-decanoamide, N, N-d imet hylbenzamine, N, N-diethylbenzamide, . N, N-dipropyl-m-t oluamide, N,N-dibutyl-p-toluamlde, N-phenyl-N-methylacetamlde, N- (p-tolyl) -N-ethylacetamide, N-(3,5-dimethylphenyl)-N-methylpropionamide, N,N-dimethyl-3,5-dlmethylbenzamide, N,N-dibutyl-4-ethylbenzamide, N, N-d ipheny lac etamide, N- (3 -met hy Ipheny l)-N-ethylbenzamide, Ν,Ν-bis (6-methylphenyl)propionamide, Ν,Ν-bls (3,5-dimethyl-phenyl)propionamide, and the like; (3) β-f ormylpiperidine, N-acetyi pyrrolidine, N-propionylmorphollne, N-acetyl-4, 5-dimethylpyrrolldine, N-butanoylpiperidine, N-aeetyl-6-methylpiperidine, and the like; and (4) 1 -met hy 1-2 -pyrr olid one, l-phenyl-2-pyrroli-d one, 1 -butyl -2 -piper id one, l-pentyl-2-piperidone, l-(m-tolyl)-2-piperidone, l-ethyl-2-piperidone, l-(3,5-di-methylphenyl) -2 -piper id one, l-methyl-2-piperidone, 1- phenyl-2-piperIdone, 1-propyl-2-piperIdone, 1-isopropyl-2-homopiperidone, N-ethyl-2-homopiperidone . However, we especially prefer to use dimethylacetamide, dimethylforrn-amlde, or N-methyl-2-pyrrolldone in this heating step.

The acids used in preparing the 3-hydroxy-3-methyl-7-amino-cepham compounds include sulfuric . acid or sulfamic acid. Salts, and esters of these acids may also be used in equivalent amounts. Examples of salts of these acids include the alkali metal salts, e.g., the lithium, sodium, potassium, and rubidium salts, although only the sodium and potassium salts are of practical econtbmlc significance. The magnesium, calcium, salts of these acids may also be used but are not preferred. Partial and complete esters of these acids with Cj_ to Cg-alkanols such as dimethylsulfate, d ethylsulfate, dimethylsulfamate, dipropylsulfamate, and the like can also be used. However, it is easier and more convenient to use the free acids in the reaction mixture.

The 3-hydroxy-3-methyl-7-amlno-cepham ester products can be recovered from the reaction mixture by conventional methods. Usually the reaction mixture is concentrated under vacuum to remove most of the reaction mixture solvents therefrom. The residue is dissolved in a suitable organic solvent such as a chlorinated hydrocarbon solvent such as methylene chloride, chloroform, carbon tetrachloride, a Cj_ to Cg-alkanol such as · methanol, lsopropanol, etc., or a hydrocarbon such as benzene, toluene, xylene, heptane, or the like, and extracted with dilute aqueous acid to remove residual tertiary carboxamide solvents. The organic solvent solution con- taining the product can be concentrated to obtain relatively pure product, sufficiently pure for further contemplated reactions, or further purified by conventional methods, e.g., re-crystallization.

Examples of compounds of this invention and the sulfoxides from which they can be obtained include the following: tert-Butyl 3-hydroxy-3-methyl-7- (phenylacet-amldo) cepham-4-carboxylate from the tert butyl ester of phenylmethylpenicillin sulfoxide. 1", l"-Dimethyl-2 "-propynyl 3-hydroxy-3-methyl 7- (4 ' -nitrophenylacetamido)cepham 4-carboxylate from the l",l'Vdimethyl-2 "-propynyl ester of 4-nitrophenylmethyl penicillin sulfoxide, 2",2",2"-trichloroethyl 3-hydroxy-3-methyl-7- (octanoylamido)cephem-4-carboxylate from the 2",2",2"-trichloroeth l ester of heptylpenicillin sulfoxide, 4 "-Nitrobenzyl 3-hydroxy-3-methyl-7- (21 ,2 ' -di-methylphenylacetamido-cepham-4-carboxylate from the 4"r- . nitrobenzyl ester of 21 ,21 -dimethylphenylmethylpenicillin sulfoxide, tert-Butyl 3-hydroxy-3-methyl-7- (5 '-butoxy-carbonylaminoadippylamldo)cepham-4-carboxylate from the tert-butyl ester of the N-butoxycarboxyl protected penicillin N sulfoxide, 3-Hydroxy-3-methyl-7- (phenoxyacetamido) cepham-4-carboxylic acid from phenoxymethylpenicillin sulfoxide, 3-Hydroxy-3-methyl-7- (2 · -thienylacetamido)cepham-4-carboxylic acid from thienylmethylpenicillln sulfoxide, . Salts of such compounds are made by treating the acids with an appropriate base or basic salt such as sodium hydroxide, pbtassium hydroxide, sodium acetate, sodium acetate, potassium carbonate and the like to form the sodium or potassium salts, or with ammonium hydroxide or a trialkylamlne such as trimethylamine or triethyl-amine to form the respective ammonium or amine salts.

The 3-hydroxy-3-methyl-7-amino-cepham compounds show some antibiotic activity against various Qram positive and Gram negative bacteria. However, they are of primary interest for use in preparing compounds having the cephalosporin nucleus. For example, stirring one of the 3-hydroxy-3-methyl cepham compounds of this invention in a mixture of acetic anhydride and N,N-dimethylacetamide in an oil bath for approximately 15 minutes at about 100-110°C. gives good yields of the corres onding 3-methyl- ephem compound. Fo example, tert -butyl 3-hydroxy-3-methyl-7-(phenoxyacetamido)cepham- -carboxylate will undergo an elimination reaction to form the corresponding ester, tert-butyl 3-methyl-7- (phen-oxyaeetamido) - -cephem- -carboxylate, which is useful in the overall process of making the known cephalosporin antibiotic cephalexin /f-D-a-aminophenylacetamido) -3-methyl-Δ -cephem- -carboxylic acid_7 from phenoxyjnethyl penicillin. In such process the phenoxyacetyl group is cleaved by treatment of the 3-methyl- -cephem ester with phosphorus pentachloride and pyridine, followed by treatmen of the chlorinated product with methanol, and then with water to form the 7-amino-3-niethyl-cephem nucleus ester, which can be recovered conveniently, for example, as the p-toluenesulfonate salt, followed by reacylation of the nucleus ester with an activated or reactive form of an N-protected a -aminophenylacetic acid, followed by removal of the N-protecting group and the .este r group to obtain cephalexin.

The invention is further exemplified by the following detailed examples which . illustrate how compounds of this invention can be made .

Example 1 -CHg-CgH^-NOg II III A solution of 500 mg . of penicillin-V-sulf oxide p-nltrobenzyl ester, 10 mg. p-toluene sulfonic acid-monohydrate and 142 mg . dimethylacetylenedicarboxylate in 10 ml . Ν, Ν-dimethylacetamide were stirred in an oil bath at 110-113 ° for 5 hours . The majority of solvents were removed In vacuo and the oily residue passed over 8 g . eluting with chloroform. The concentrated eluate was taken up in hot ethanol from which 90 mg . (17.2 percent ) of 4 "-nitrobenzyl 3-methyl 7τ- (2 ' -phenoxyacet-amidoJ -S-cephem^-carboxylat (III) were deposited upon cooling, rn. p. I90-I9I0. Mother liquors were evaporated and the residue triturated with hot methanol isobutyl ketone to afford a white solid, recrystallization of which from hot acetonitrile yields 64 mg. (12.8 percent) of the title compound (II), m.p. 214-215°.

During repetitions of this preparation yields of II varied between 10 and 22 percent.

The structure of compound II, 4 'ihitrobenzyl 3-hydroxy-3-methy1-7- (2 · -phenoxyacetamido) cepham-4-carboxylate was further characterized by preparation by known methods of (a) 3-hydroxy-3-methyl.-7- (2 "-phenoxyacetamido) cephem-4-carboxylic acid, (b) methyl 3-hydroxy-3-methyl-7- ^"-phenoxyacetamido) cephem-4-carboxylate, (c) 4"-nitrobenzyl 3- (trimethylsilyloxy)-3-. methy1-7- (21 -phenoxyacetamido)cephem-4- carboxylate, (d) 4"-nitrobenzyl 3-acetoxy-3-methyl-7- (21 - phenoxyacetamido) cephem-4-carboxylate, (e) 4"-nitrobenzyl 3- (trifluoroacetoxy)-3- methy1-7- (2 ' -phenoxyacetamido)cepham-4- carboxylate, (f) 4"-nitrobenzyl 3-hydroxy-3-methyl-7- (2 · - phenoxyacetamido)cepham-4-carboxylate-1- oxide, (g) 4"-nitrobenzyl-3-acetoxy-3-methyl-7-(2 '- phenoxyacetamido)cepham-4-carboxylate-1- oxide, (h) 4"-nitrobenzyl-3-acetoxy-3-methyl-7-(N- acetyl-2 ' -phenoxyacetamido)cepham-4- carboxylate-l-oxide, (±) 4"-nitrobenzyl 3-hydroxy-3-methyl-7- (2 ' - phenoxyacetamido) cepham-4-carboxylate-l, 1- dioxide, (j) .4"-nltrobenzyl 3-acetoxy-3-methyl-7- (2 ' - phenoxyacetamido) cepham-4-carboxylate-l, 1- dioxide.

Spectral data and elemental analyses were in agreement with the structures proposed for the above named compounds, and thus provides further evidence of the correctness of the named compound II, namely 4"-nitrobenzyl 3-hydr oxy-3-methyl-7- (21 -phenoxyacetamido) cepham-4-carboxylate . is a trademark of Florldin Company for their brand of an activated form of magnesium silicate used for chromatography, antibiotic processing, etc. See, United States Patent No. 2,393,625, or Merck Index, 8th Edition (1968) pp. 637-638 under 'magnesium silicate'. Example 2 This example illustrates the utility of the new compounds of this invention as intermediates in the preparation of the corresponding 3-methyl 3-cephem compounds.

A suitable vessel containing a mi ture of 100 mg. of 4"-nitrobenzyl 3 -hydroxy -3 -me hy 1-7- (2 ' -phenoxyacetamido) cepham- -car boxy late in 1 ml. of acetic anhydride and 0.2 ml. of Ν,.Ν-dimethylacetamlde (DMA) was immersed in an oil bath, and the mixture was stirred for approximately 15 minutes at 105°C. From the reaction mixture there is obtained 4 "-nitrobenzyl 3-methyl-7- (2 ' f phenoxyacetamido) -3-cephem-4-carboxy late, which upon ester group removal by known hydrogenation methods, can be converted to 3-methyl-7-(2 '-phenoxyacetamido)-3-cephem-4-carboxylate, a known antibiotic.

Example 3 This example illustrates the direct preparation of the 3 -hydrox -3 -methyl cepham compound in the acid form.

A solution containing 10.0 g. of penicillin V sulfoxide ^,2-dimethyl-6-phenoxyacetamido-penam-3-carboxyllc acid-l-oxide_7, 0.15 ml. of concentrated sulfuric acid, 100 ml. of benzene, and 75 ml. of N, N-dlmethylaeet-amide. (DMA) was refluxed 14 hours. The , dark red color reaction mixture was then concentrated under vacuum and the residue was dissolved in 200 ml. of met hylene chloride . After washing the dilute hydrochloric acid solution to remove residual N,N-dimethylacetamide, the methylene chloride solution was extracted with 5 percent disodlum hydrogen orthophosphate in water solution. Acidification of the aqueous phase, extraction with chloroform, and concentration of the chloroform solution left 4,7 g. (47 percent yield) of the acid, 3-?hydroxy-3-methyl-7- (phenoxy-acetamido)cepham-4 -carboxyllc acid. An analytical sample was obtained by recrystallization from chloroform, m.p.

I52 -153 °C. The acid product was also characterized by Infrared (IR), ultraviolet (UV), and nuclear magnetic resonance (NMR) spectra, elemental analysis, and nonaqueous titration.

Example 4 A 10.0 g. portion of 4"-nitrobenzyl penicillin V· sulfoxide ester was added to 80 ml. of benzene and 60 ml. of DMA containing 2 drops of concentrated sulfuric acid. The solution was refluxed for 12 hours and then concen- > trated to a residue weight of 23.2 g. Addition of 100 ml of isopropyl alcohol resulted in,direct crystallization of substantially pure 4-nitrobenzyl 3-hydroxy-3-methyl-7-phenoxyacetamido)cepham-4-carboxylate, A purified sample of this product had a melting point of 212-214 °C. It was further characterized by IR, UV, NM , spectral analyses,, as well as by elemental analysis and thin layer chromatographic (TLC) methods. All data were consistent with assigned structure for the named compound.

Example 5 The procedure of example 4 was repeated for employing an equivalent amount of dimethyl sulfate in place of sulfuric acid. The product, 4 "-nitrobenzyl 3-hydroxy-3-methyl-7- (phenoxyacetamido)cepham-4-carboxyl-ate had a melting point of 208-210°C.

Example 6 A mixture of 10.0 g. of penicillin V sulfoxide, 4-nitrobenzyl ester, 0.194 g. of sulfamic acid in 112 ml. of benzene and 88 ml. of dimethylacetamide was stirred and refluxed 14 hours and then allowed to stand at room temperature for three hours. The solvents were removed under vacuum. The residue was triturated with xylene and re-concentrated under vacuum. The product was triturated with chloroform and the crystalline product was filtered. It weighed 3.91 g. (40.5 percent yield) m.p. 211-212°C. witfcw decomposition, and was identical to compound II from example 1.

Example A mixture of 2.5 g. of 4-nitrobenzyl penicillin V sulfoxide ester,, 0.07 g. of potassium bisulfate, in 28 ml. of benzene and 22 ml. of dimethylacetamlde was reflux-ed until no starting material was present (about 18 hours). The mixture was concentrated In vacuo and re-concentrated after azeotroplng with xylene. The product 4 " - nit r obe nz 13 -hyd r ox -3 -me t hy 1 - 7 - ( he noxy a cetamido)-cepham-4-carboxylate, was crystallized after triturating with chloroform. The product weighed 1.02 g. (41 percent yield) m.p. 211-213°C. A mixed melting point with a known sample of the same product was 211-213°C.

Example 8 The procedure of Example 4 is repeated using 2,2,2-trichloroethyl penicillin G sulfoxide ester in a mixture of benzene and dimethylacetamlde containing concentrated sulfuric acid as the acidifying agent. After refluxing, and work-up of the. reaction mixture there is obtained a product, 2",2",2"-trichloroethyl 3-hydroxy-3-methyl-7- (phenylacetamldo)eepham-4-carboxylate .

This ester is useful as an intermediate in the manufacture of desacetoxycephalosporin antibiotic sub-stances, e.g., cephalexin.

Example 9 The procedure of Example 4 is repeated except that tert-butyl 2,2-dimethyl-6- (2 ' ,2 ' -dlmethylphenyl-acetamido)penam-3-carboxylate-l-oxide is used as starting material in place of the 4-nitrobenzyl penicillin V sulfoxide ester. There is obtained as product the tert-* butyl 3.-hydroxy-3-methyl-7- (2 ' ,2 ' -dimethylphenylacetamido) -cepham-4-carboxylate.

This ester is useful as an intermediate in the production of desacetoxycephalosporin antibiotic sub- stances .

Example 10 The procedure of Example 4 is repeated except that l,I, l ,,-dimeth l-2 "-prop nyl 2,2-dimethyl-6- (2 ».-thieriylacetamido)penam-4-carboxylate-l-oxlde Is used In place of the penicillin V sulfoxide ester . There is obtained as product the l", l "-dimethyl-2 ,,-propynyl 3-hydroxy 3-methyl-7- (2 1 -thienylacetamido) cepham 4-carboxylate .

This ester is useful as an intermediate in the production of desacetoxycephalosporin antibiotic sub-stances such as 3-methyl-7- (2 ' -thienylacetamid ) -/y -cephem~: -car boxy lie acid,., a known antibiotic .

Example 11 In a solution of dry benzene containing 28 millimoles of dry pyridine there are dissolved 7.8 mllli-moles of 4 "-methoxybenzyl 3-hydroxy -3-methyl-7- (phenoxy-acetamido) cepham-4-carboxylate, which had been prepared by heating the 4 "-methoxybenzyl penicillin V sulfoxide ester in dime thy lacetamide to 90° -110°C . for about 6 hours with sulfuric acid catalysis . The resulting solu- . tion is warmed to 50° to 60°C . and then while stirring 28 millimoles of phosphorus pentachloride are added at one time . The mixture is stirred at this temperature under . a nitrogen atmosphere for about 1 hour. The resulting mixture is then cooled to 0° to 5°C . and treated with an excess of methanol. This methanol -treated mixture .is stored . for several hours at. room temperature . After removing most of the benzene and methanol solvents by evaporation below 50°C . under reduced pressure, the residue (having a pH of about 1.8) is taken up in a 1 : 1 by volume mixture of water and tetrahydrof uran. After 2 hours, the tetrahydrof uran is removed and the aqueous residue is stirred with ethyl acetate and adjusted to pH 6,5-7 with IN aqueous sodium hydroxide. The ethyl acetate layer containing the crude "-met hoxy -benzyl 3-hydroxy-3-methyl-7-aminocepham-4-carboxylate ester product is treated with about 8 millimoles 4"-toluene-• sulfonic acid to precipitate the 4 "-methpxybenzyJL 3-hydroxy-3-methyl-7-amlnocepham-4-carboxylate p-toluene sulfonate salt, which is separated from the reaction mixture by filtration. The separated salt can be stored in salt form or taken up in ethylacetate/water mixture and adjusted to near pH7, to separate the pure 4"-methoxy-benzyl 3-hydroxy-3-methyl-7-amino-cephem-4-carbox late .

This ester product can be used as an intermediate, e.g., to prepare cephalexin by acylating the amino-ester with N- (tert-butoxycarbonyl) -D-a-phenylgl cine by heating in the mixed anhydride, N, N-rdimethylacetamide, containing acetic anhydride to about 105°C., and then treating the resulting product with anhydrous trifluoro-acetic acid for about 15 minutes to obtain 3-methyl-7- (D-a-aminophenylacetamido)-Δ -cephem-4-carboxylic acid (cephalexin). This antibiotic compound can be administered topically, parent erally, or as is preferred, orally in doses of from about 50 mg. to about 500 mg. from 1 to 4 times per day depending upon the disease condition being treated .

Example 12 Following the procedure of Example 3, phenoxy- methyl penicillin sulfoxide acid is mixed in N,N-dimethyl- acetainlde and benzene solvent with an equivalent amount of sulfamic acid and heated for 14 hours. After concentration of the reaction mixture and purification according to the procedures described therein, there is obtained as product, 3-hydroxy-3-methyl-7- (phenoxyacetamido)cepham-4-carboxyllc acid.

Claims (12)

1. 35801/2 1, A 3-hydroxy-3-methyl-7-amino-cepham-4-carboxyl compound characterized by the formula i eooR wherein R is hydrogen, thienylacet^ikido, or an acyl group of the formula wherein m is an integer of from O to 4 inclusive, n is an integer of from O to 4 inclusive, z is O or 1, and when & is O, the methylene groups in m and n are connected by a chemical bond, and such acyl groups substituted on phenyl carbon atoms thereof with fluorine, chlorine, bromine, iodine, nitro, C1 to Cg a kyl, to Cg alkyloxy, or trifluorom ethyl, and R is an ester group selected from the group consisting of 2, 2, 2-trichloroethyl C . to C -tert-alkyl nitrobenzyl or methoxybenzyl hydrogen or a salt-forming cation. 35801/2

2. The compound of claim 1 characterized in that m is O, n is l.i z is 1, and R ; is 4"-nit,robenzyl.

3. The compound of claim 1 r-2, characterized in that the compound is 4" -nitrobenzyl 3"hydroxy-3-methyl-7-(2,*phenoxy-acetamido^cepham 4-carboxylatd, 3-hydroxy-3-methyl-7-(phenoxy-r acetaniido)cepham-4-carboxylic acid or 4M*methoxybenzyl 3-hydroxy-3 -m ethylr 7-amino-cepham-4-carboxylate.

4. A process for preparing a 3-hydroxy-3-methyl-7-amino-cepham-4-carboxyl compound characterized by the formula Wherein R* is hydrogen, , or a conventional amino protecting group, and R1 is hydrbgeriy a conventional ester group, or a salt forming cation, or ah anionic charge when R is HJ© / characterized by heating a penicillin1 sulfoxide acid or ester in the presence of sulfuric acid, sulfamic acid, or a soluble salt' or ester thereof to about 80°C, to about 150°C, in a reaction1 mixture containing at least about 10 percent by volume of 'a tertiary, carboxamide, said tertiary carboxamide being further defined as having the formula . '< - '■ ■ ■ o " " R -C-N-R 1 t 2 ■ .

5. R3 . wherein (1) R is hydrogen, and each of Rg and Rg is alkyl, phenyl,, tolyl, or xylyl such that g and Rg together contain up to about 14 carbon atoms; (2) at least one of R^, R^ and Rg is alkyl, and not more than two of R j, Rg, and Rg are phenyl, tolyl, xylyl, and R^, R^, and Rg together contain up to about 18 carbon atoms; (3) ¾ is hydrogen or alkyl, R2 and R^ are taken together with the nitrogen to which they are bonded to form a saturated monocyoliG ring which contains from to 6 carbon atoms in the ring, which ring oan also contain an oxygen ring member, gamma to the ring nitrogen, and R-j_, R2 and R^ together contain not more than 12 oarbon atoms; and/or (4) R^ and Rg are taken together with the amide grouping (-C(O)-N-) to whioh they are bonded to form a saturated oarbonyl containing monocyclic ring having from ^ to 6 ring carbon atoms, R^ is alkyl, phenyl, tolyl, or xylyl, and R^, R2, and R^ together contain not more than l^ carbon atoms; to form the oepham aoid or ester. process of claim 4 5· - >-r The -5 characterized in that a penicillin sulfoxide acid or ester is heated in the presence of sulfuric or sulfamic acid to from about o o 90 C. to about 120 C. in a reaction mixture containing a tertiary carboxamide wherein each of R^, R2 and R^ is alkyl, such that R^, R2, and R^ together contain up to about 18 carbon atoms. 4 6

6. The prooess of claim -5-or -6--characterized in that the carboxamide is N,N-dimethylacetamide.

7. --8-.- The process of claim characterized in that V-nitrobenzyl phenoxymethyl penicillin sulfoxide ester is heated in the presence of sulfuric acid in a mixture of N, N-dimethylacetamide and benzene to form -nitro-benzyl 3-hydroxy-3-methyl-7- (phenoxyaoetamido)cepham-^-carboxylate. 5

8. --9-.- The process as defined in claim -6 oharac- r terized in that V-nitrobenzyl phenoxymethyl penicillin sulfoxide ester is heated in the presence of sulfamic acid in solvent system containing N,N-dimethylacetamide.. 5

9. -1-0. The process of claim -^-characterized in that the phenoxymethyl penicillin sulfoxide acid is heated in the presence of sulfamic acid in a solven system containing N,N-dimethylacetamide. 4 9

10. -l-lr. The process of any one of claims 5- to -10-charaeterized by converting the oepham acid or ester into the desired salts or z itterions. 4

11. -1-3-. The process of claim -5 substantially as described in any one of examples 1 to 12.

12. -1-3-. The oepham compounds of claim 1 substantially as described in any one of examples 1 to 12. AGENTS FOR APPLICANTS