CA1129773A - PENICILLANIC ACID 1,1-DIOXIDES AS .beta.-LACTAMASE INHIBITORS - Google Patents

Abstract

Abstract of the Disclosure Penicillanic acid 1,1-dioxide, and esters thereof readily hydrolyzable in vivo, are useful for enhancing the effectiveness of several .beta.-lactam antibiotics against many .beta.-lactamase producing bacteria. The invention thus relates to penicillanic acid 1,1-dioxide or an ester thereof in combination with a .beta.-lactam antibiotic as a new pharmaceutical composition.

Description

One of the most well-known and widely used class of an~ibacterial agents are the so-called ~-lactam antibiotics. These compounds are characterized in that they have a nucleus consisting of a 2-azetidinone (~-lactam) ring fused to either a thiazolidine or a dihydro-1,3-thiazine ring. When the nucleus contains a thiazolidine ring, -the compounds are usually referred to generically as penicillins, whereas when the nucleus contains a dihydrothiazine ring, the compounds are referred to as cephalos-porins. Typical examples of penicillins which are commonly used in clinical practice are benzylpenicillin (penicillin G), phenoxymethylpenicillin (penicillin V), ampicillin and carbenicillin; typical examples of common cephalosporins are cephalothin, cephalexin and cefazolin.
However, desplte the wide use and wide acceptance of the ~-lactam antibiotics as valuable chemotherapeutic agents, they suffer from the major drawback that certain members are not active against certain microorganisms.
It is thought that in many instances this resistance of a particular micro organism to a given ~-lactam antibiotic results because the microorganism ~roduces a ~-lactamase. The latter substances are enzymes which cleave the ~-lactam ring of penicillins and cephalosporins to give products which are devoid of antibacterial activity. However, certain substances have the ability to inhibit ~-lactamases, and when a ~-lactamase inhibitor is used in combina-tion with a penicillin or cephalosporin it can increase or enhance the anti-bacterial ef:fectiveness of the penicillin or cephalosporin against certain microorganisms. It is considered that there is an enhancement of antibacterial effectiveness when the antibacterial activity of a combination of a ~-lacta-mase inhibiting substance and a ~-lactam antibiotic is significantly greater than the sum of the antibacterial activities of the individual components.
l,l-Dioxides of benzylpenicillin, phenoxymethylpenicillin and certain .
'.

~' ' ~?f~f7~73 esters ~hereof have been disclosed in United S~ates Patents 3~197,466 and 3,536,698, and in an article by Guddal et al. J in T~tlahedron Letters, No. 9, 381 (1962). Harrison et al., in the Journal of the Chemical Society ~London), Perkin I, 1772 (1~763, have disclosed a variety of penicillin l~l-dioxides and l-oxides, including methyl phthalimidopenicillanale l,l-dioxide, methyl 6,6-dibromopenicillanate l,l-dioxide, methyl penicillcmate la-oxide~ methyl penicillanate l~-oxide, 6,6-dibromopenicillanic acid l~-oxide and 6,6-dibromo-penicillanic acid l~-oxide.
According to the invention there are provided novel pharmaceutical compositions comprising a cornpound of the formula O /o ~C113 ` ---~I) N COOR

or a pharmaceutically-acceptable base salt thereof, wherein Rl is selected from the group consisting of hydrogen and ester-forming residues readily hydrolyzable _ vivo, together with a ~-lactam antibiotic.
The term "ester-forming residues readily hydrolyzable in v "
is here intended to refer to non-toxic ester residues which are rapidly cleaved in m = alian blood or tissue, to release the corresponding free acid (i.e. the compound of formula I, wherein Rl is hydrogen). Typical examples of such readily hydrolyzable ester-forming resldues which can be used for Rl are alkanoyloxymethyl having from 3 to ~ carbon atoms, l-(alkanoyloxy)ethyl having from 4 to 9 carbon atoms, l-methyl-l-~alkanoyloxy)ethyl having from 5 to 10 - carbon atoms, alkoxycarbonyloxymethyl having from 3 to 6 carbon atoms, l-~alkoxycarbonyloxy)ethyl having from 4 to 7 carbon atoms, l-me~hyl-l-~alkoxy-carbonyloxy)ethyl having from 5 to 8 carbon atoms, 3-phthalidylJ 4-crotono-lactonyl and y-butyrolacton-4-yl.
The compounds of the formula I, wherein Rl is hydrogen or an ester-forming residue readily hydrolyzable in vivo, enhance the antibacterial activity of ~-lactam antibiotics.
The specification refers also to the compounds of the formula S ~CH3 / ~ N ---(II) and o ~ ~ CH3 ---~III) COOR

and the salts thereof, wherein Rl is as defined previously. Said compounds of the formulas II and III are intermediates to said compounds of the formula I.
Throughout this specification, the compounds of formula I, are referred to as derivatives of penicillanic acid, which is represented by the structural formula S i~ 3 CH3 ---(IV) COOH

In formula IV, broken line attachment of a subs'ituent to the bicyclic nucleus indicates that the substituent is below the plane of the bicyclic nucleus.
Such a substituent is said to be in the ~-configuration. Conversely, solid .: .

:: :
' ' line attachment of a substituent to the bicyclic nucleus indicates that the substituent is attached above the plane of the nucleus. This latter config-uration is referred to as the ~-configuration.
Also in this specification reference is made to certain derivatives of cepnalosporanic acid, which has the formula ~S~
o ~ V) O ~ ~ C}~2-o-C-CH3 COOII

In formula V, the hydrogen at C-6 is below the plane of the bicyclic nucleus The derived terms desacetoxycephalosporanic acid and 3-desacetoxymethylcephalo-sporanic acid are used to refer to the structures VI and VII, respectively.

.~1 ..

~ C~13 ~ ~

COOH COO~l VI VII
4-Crotonolactonyl and y-butyrolacton-4-yl refer to structures VIII and IXJ
respectively. The wavy lines are intended to denote each of the two epimers and mixtures thereof.

O O
VIII IX

~ en Kl is an ester-forming residue readily hydrolyzable in vivo in a compowld of formula I, it is a grouping which is notionally derived from an alcohol of the formula R1-0~l7 such that the moi.ety COORl in such a compound of formula I represents an ester grouping. Moreover, Rl is of such a nature that the grouping COORl is readily cleaved in in vivo to liberate a free car-boxy group (COOII). That is to say, Kl is a group of the type that when a compound of formula I, wherein Rl is an ester-forming residue readily hydrol-yzed in vivo, is exposed to mammalian blood or tissue, the compound of formula I, wherein Rl is hydrogen, is readily produced. The groups Rl are well-known in the penicillin art. In most instances they improve the absorp~ion character.istics of the penicillin compound. Additionally, Rl should be of such a nature that it imparts pharmaceutically-acceptable properties to a compound of formula I, and it liberates pharn~aceutically-acceptable fragments when cleaved in vivo.
~s indicate~ above, the groups Rl are well-known and are readily iden~ified by those skilled in the penicillin art. See, for example, West German Offenlegungsschrift No. 2,517,316. Typical groups for Rl are 3-phthalidyl, 4-crotonolactonyl, y-butyrolacton-4-yl and groups of the formula - C-o c R5 and -C-O-C-O-R

X XI
wherein R3 and K4 are each selected from the group consisting of hydrogen and alkyl having from 1 to 2 carbon atoms7 and R5 is alkyl having from l to 6 car-bon atoms. However, preferred groups for Rl are alkanoyloxymethyl having from3 to 8 carbon atoms, l-(alkanoyloxy)ethyl having from 4 to 9 carbon atoms, l-methyl-l-(alkanoyloxy)ethyl having from 5 to lO carbon a~oms, alkoxycarbonyloxy-37~3 me~hyl having from 3 to 6 carbon atoms, l-(alkoxycarbonyloxy)ethyl having ~rom to 7 carbon atoms, l-methyl-l-(alkoxycarbonyloxy)ethyl havlng from 5 to 8 carbon atoms, 3-phthalidyl, ~-crotonolactonyl and y-butyrolacton-4-yl.
rhe compounds of formula I, wherein Rl is as defined previously can be prepared by oxidation of either of the compouncls of formula II or III, wherein Rl is as deEined previously. A wide variety of oxidants known in the art for the oxidation of sulfoxides to sulfones can be used for this process.
~owever, particularly convenient reagents are metal permanganates, such as the alkali metal permanganates and the alkaline earth metal permanganates, and organic peroxy acids, such as organic peroxycarbo,cylic acids. Convenient individual reagents are sodium permanganate, potassium permanganate, 3-chloroperbenzoic acid and peracetic acid.
; ~en a compound of the Formula II or III, wherein Rl is as defined previously, is oxiclized to the corresponding compound of the :Eormula I using a metal permanganate, the reaction is usually carried oùt by treating the compound of the formula II or III with from about 0.5 to about 5 molar equivalents of the permanganate, and preferably about 1 molar equivalent of the permanganate, in an appropriate solvent system. An appropriate solvent system is one that does not adversely interact with either the starting materials or the product, and water is commonly used. If desired, a co-solvent which is miscible with water but will not interact with the permanganatel such as tetrahydrofuran, can be added. The reaction is normally carried out at a temperature in the range from about -20 to about 50 &., and preEerably at about 0C. At about 0C. the reaction is normally substantially complete within a short period, e.g. within one hour. Although the reaction can be carried ou~ under neutral, basic or acid conditions, it is preferably to operate under substantially neutral conditions in order to avoid decomposition 77~

of the ~-lactam ring system of the compound of the formula L, Indeed, it is often advantageous to buffer the p}l of the reaction medium in the vicinity of neutrality. The product is recovered by conventional techniques. Any excess permanganate is usually decomposed using sodium bisulfite~ and then if the product is out of solution, it is recovered by filtration. It is separated from manganese dioxide by extracting it into an organic solvent and removing the solvent by evaporation. ~lternatively, if the product is not out of solution at the end of the reaction, it is isolated by the usual procedure of solvent extraction.
When a compound of the formula II or III, wherein R is as previously defined, is oxidized to the corresponding compound of the formula I, using an organic peroxy acid, e.g., a peroxycarboxylic acid, the reaction is usually carried out by treating the compound of the formula II or III with from about 1 to about 4 molar equivalents, and preferably about 1.2 equivalents o~ the oxidant in a reaction-inert organic solvent. Typical solvents are chlorinated hydrocarbons, such as dichloromethane, chloroform and 1,2-dichloroethane;
and ethers, such as diethyl ether, tetrahydrofuran and 1,2-dimethoxyethane.
The reaction is normally carried out at a temperature of from about -20 to about 50C., and preferably at about 25C. At about 25C. reaction times of about 2 to about 16 hours are commonly used. The product is normally isolated by removal of the solvent by evaporation in vacuo. The product can be purified by conventional methods, well-known in the art.
When oxidizing a compound of the formula II or III to a compound of the formula I using an organic peroxy acid, it is sometimes advantageous to add a catalyst such as a manganese salt, e.g. manganic acetylacetonate.
The compound of the formula I, wherein ~1 is hydrogen, can also be obtained by removal of the protecting group Rl from a compound of the formula I, wherein Rl is a penicillin carboxy protecting group. In this context, Rl can be any carboxy protecting group conventionally used in the penicillin art to protect carboxy groups at the 3-position. The identity of the carboxy protecting group is not critical. The only requirements for the carboxy protecting group Rl are that: (i) it must be stable during oxidation of the compound of formula II or III; and (ii) it must be removable from the compound of formula I, using conditions under which the ~-lactam re-mains substantially intact. Typical examples which can be used are the tetra-hydropyranyl group, the benzyl group, substituted benzyl groups (e.g. 4-nitro-benzyl), the ben~ylhydryl group, the 2,2,2-trichloroethyl group, the t-butyl group and the phenacyl group. See further: United States Patents 3,632,850 and 3,197,~66; British Patent No. 1~0~1,985, Woodward et al., Journal of the hmerican C emical Society, 88, 852 (1966); Chauvette, Journal of ~
Chemistry, 36, 1259 (1971); Sheehan et al., Journal of Organic Chemistry, 29J
2006 (196~); and "Cephalosporin and Penicillins, Chemistry and Biology", edited by H. E. Flynn, Academic Press, Inc., 1972. The penicillin carboxy protecting groups is removed in conventional manner, having due regard for the lability of the ~-lactam ring ~ystem.
In like manner, compounds of the formula I, wherein Rl is as previously defined, can be prepared by oxidation of a compound of the formula C}13 '"C~l N ~
"'COORl wherein R is as previously defined. This is carried out in exactly the same manner as described hereinbefore for oxidation of a compound of the formula II
or III, except that twice as much oxidant is usually used.

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:

Compounds of the formula IJ wherein R1 is an ester-forming residue readily hydrolyzable in vivo, can be prepared directly from the com-pound of formula I, wherein X is hydrogen, by esterification. The specific method chosen will depend naturally upon the precise structure of the ester-forming residue, but an appropriate method will be readily selected by one skilled in the art. In the case wherein Rl is selected from the group consisting of 3-phthalidyl,4-crotonolactonyl, y-butyrolacton-4-yl and groups of the formula X and XI, wherein R3, R4 and R5 are as defined previously, they can be prepared by alkylation of the compound of formula I, wherein is hydrogen,with a 3-phthalidyl halide~ a 4-crotonolactonyl halide, a y-butyrolacton-4-yl halide or a compound of the formula " c 1 1 Q-C-0-C-R~ and Q-l-0-C-0-R~
R4 1~4 XII XIII

wherein Q is halo~ and R3, R4 and R5 are as previously defined. The terms "halide" and "halo" are intended to mean derivatives or chlorine, bromine and iodine. The reaction is conveniently carried out by dissolving a salt of the compound of formula I, wherein Rl is hydrogen, in a suitable, polar, organic solvent, such as N,N-dimethylformamide, and then adding about one molar equivalent o~ the halide. When the reaction has proceeded essentially to completion, the product is isolated by standard techniques. It is often suf~icient simply to dilute the reaction medium with an excess of water, and then extract the product into a water-immiscible organic solvent and then recover same by solvent evaporation. Salts of the starting material which are commonly used are alkali metal salts, such as sodium and potassium salt, ,f~7~f ;3 and tertiary amine salts, such as triethylamine, N-ethylpiperidine, N,N-dimethylaniline and N-methylmorpholine salts. The reaction is run at a temperature in the range from about 0 to 100C., and usually at about 25C.
The length of time needed to reach completion varies according to a variety of factors, such as the concentration of the reactants and the reactivity of the reagents. Thus, when considering the halo compound, the iodide reacts faster than the bromide, which in turn reacts faster than the chloride.
In fact, it is sometimes advantageous, when utilizing a chloro compound, to add up to one molar equivalent of an alkali metal iodide. This has the effect of speeding up the reaction. With full regard for the foregoing factors, reaction times of from about 1 to about 24 hours are commonly used.
Penicillanic acid lc~-oxide, the compound of the formula II, wherein Rl is hydrogen, can be prepared by debromination of 6,6-dibromopenicillc~nic acicl lc~-oxide. 'I'he debromination can be carried out using a conventional hydrogenolysis technique. Thus, a solution of 6,6-dibromopenicillanic acid 1~-oxide is stirred or shaken under an atomosphere of hydrogen, or hydrogen mixed with an inert diluent such as nitrogen or argon, in the presence of a catalytic amount of palladium-on-calcium carbonate catalyst. Convenient solvents for this debromination are lower-alkanols, such as methanol; ethers, such as tetra-hydrofuran and dioxan; low molecular weight esters, such as ethyl acetate and butyl acetate; water; and mixtures of these solvents. However, it is usual to choose conditions under which the dibromo compound is soluble. The hydro-genolysis is usually carried out at room temperature and at a pressure from about atmospheric pressure to about 50 p.s.i. The catalyst is usually present in an amount from about 10 percent by weight based on the dibromo compound, up to an amount equal in weight to the dibromo compound, although larger amounts can be used. The reaction commonly takes about one hour, after which ~2~73 the compound of the formula lI, wherein Rl is hydrogen, is recovered simply by filtration followed by removal of the solvent in vacuo.
6~ ibromopenicillanic acid la-oxide is prepared by oxidation of 6,6-dibromopencillanic acid with 1 e~uivalent of 3-chloroperbenzoic acid in tetrahydrofuran at 0-25C. for ca. 1 hour, according to the procedure of ~arrison et al., Journal of the Chemical Society ~London) Perkin I, 1772 ~1976).
6,6-Dibromopenicillanic acid is prepared by ~he method of Clayton, Journal of the Chemical Society ~London), (C) 2123 ~1969).

-Penicillanic acid l~-oxide, the compound of the formula III, wherein R is hydrogen, can be prepared by controlled oxidation of penicillanic acid.
Thus, it can be prepared by treating penicillanic acid with one molar equiva-lent of 3-chloroperbenzoic acid in an inert solvent at about 0C. for about one hour. Typical solvents which can be used include chlorinated hydrocarbons, such as chloroform and clichloromethane; ethers, such as diethyl ether cmd tetrahydrofuran; and low molecular weight esters such as ethyl acetate and butyl acetate. The product is recovered by conventional techniques.
Penicillanic acid is prepared as described in British patent No.
1,072,108.
Compounds of the formula II and III, wherein Rl is an ester-forming residue readily hydrolyzable in ViVO, can be prepared directly from the compound of formula II or III, wherein Rl is hydrogen, by esterification, using standard procedures. In the case wherein Rl is selected from the group consisting of 3-phthalidyl, 4-crotonolactonyl, y-butyrolacton-4-yl and groups of the formula X, and XI, wherein R3, R4 and R5 are as defined previously, they can be prepared by alkylation of the appropriate compound of the formula II or III, wherein Rl is hydrogen, with a 3-phthalidyl halide, 4-crotonolactonyl halide, a y-butyrolacton-4-yl halide, or a compound of the :L~?t~773 formula XII or ~III. The reactlon is carried out in exactly the same manner as described previously for esterification of penicillanic acid l,l-dioxide with a 3-phthalidyl halide, a 4-crotonolactonyl halide, a ~-butyrolacton-4-yl halide, or a compound of the formula XII or XIII.
Alternatively, the compounds of the formula II, wherein R is an ester-forming residue readily hydrolyzable in vivo, can be prepared by oxida-tion of the appropriate ester of 6,6-dibromopenicillanic acid, followed by debromination. The esters of 6,6-dibromopenicillanic acid are prepared from 6,6-dibromopenicillanic acid by standard methods. The oxidation is carried out, for example, by oxidation with one molar equivalent of 3-chloroperbenzoic acid, as described previously for the oxidation of 6,6-dibromopenicillanic acid to 6,6-dibromopenicillanic acid l~-oxide; and the debromination is carried out as described previously for the debromination of 6,6-dibromopenicillanic acid l~-vxide.
In like manner, the compounds o the formula III, wherein Rl is an ester-forming residue readily hydrolyzable in vivo can be prepared by oxidation of the appropriate ester of penicillanic acid. The latter compounds are readily prepared by esterification of penicillanic acid using standard methods. The oxidation is carried out, for example, by oxidation with one molar equivalent of 3-chloroperbenzoic acid, as described previously for the oxidation of penicillanic acid to penicillanic acid l~-oxide.
The compounds of the formula II, wherein Rl is a carboxy protecting group can be obtained in one of two ways. They can be obtained simply by taking penicillanic acid l~-oxide and attaching a carboxy protecting group thereto. Alternatively, they can be obtained by : (a) attaching a carboxy protecting group ~o 6,6-dibromopenicillanic acid; (b) oxidizing the protected 6,6-dibromopenicillanic acid to a protected 6,6-dibromopenicillanic acid lu-: .~

~ ~ ?d~

oxide using 1 molar equivalent of 3-chloroperbenzoic acid; and (c~ debromina-ting the protected 6,6-dibromopenicillanic acid l~-oxide by hydrogenolysis.
The compounds of the formula III, wherein R is a carboxy protecting group can be obtained simply by attaching a protecting group to penicillanic acid l~-oxide. Alternatively, they can be obtained by: (a) attaching a car-boxy protecting group to penicillanic acid; and (b) oxidizing the protected penicillanic acid using 1 molar equivalent of 3-chloroperbenzoic acid as pre-viously described.
The compounds of formulas I, II and III, wherein R is hydrogen, are acidic and will form salts with basic agents. Such salts are considered to be within the scope of this invention. These salts can be prepared by standard techniques, such as contacting the acidic and basic components, usually in a 1:1 molar ratio, in an aqueous, non-aqueous or partially aqueous medium, as appropriate. They are then recovered by filtration, by precipitation with a non-solvent followed by filtration, by evaporation oE the solvent, or in the case of aqueous solutions, by lyophilization, as appropriate. Basic agents which are suitably employed in salt formation belong to both the organic and inorganic types, and they include ammonia, organic amines, alkali metal hy-droxides, carbonates, bicarbonates, hydrides and alkoxides, as well as alkaline earth metal hydroxides, carbonates, hydrides and alkoxides. Representative examples of such bases are primary amines, such as n-propylamine, n-butylamine~
anilirle~ cyclohexylamine, benzylamine and octylamine; secondary amines, such as diethylamine, morpholine, pyrrolidine and piperidine; tertiary amines, such as triethylamine, N-ethylpiperidine, N-methylmorpholine and 1,5-diazabicyclo (4.3.0)non-5-ene; hydroxides, such as sodium hydroxide, potassium hydroxideJ
ammonium hydroxide and barium hydroxide; alkoxides, such as sodium ethoxide and potassium ethoxide; hydrides, such as calcium hydride and sodium hydride;

carbonates, such as potassium carbonate and sodium carbonate; bicarbonates, such as sodium bicarbonate and potassium bicarbonate; and alkali metal salts of long-chain fatty acids, such as sodium 2-ethylhexanoate.
Preferred salts of the compounds of the formulas I, II and III are sodium, potassium ~nd triethylamine salts.
The compounds of formula I, wherein R~ is hydrogen or an ester-forming residue readily hydrolyzable in vivo, are antibacterial agents of medium potency. The in vitro activity of the compound of the formula I, wherein Rl is hydrogen, can be demonstrated by measuring its minimum inhibitory concentrations (MIC's) in mcg/ml against a variety of microorganisms. The procedure which is followed is the one recommended by the International Collaborative Study on Antibiotic Sensitivity Testing (Ericcson and Sherris Acta. Pathologica et Microbiolo~ia Scandinav, Supp. 217, Sections A and B:
__ l-'J0 (1'~70)), and employs brain heart infusion (B~II) agar and the inoc~llar replication device. Overnight growth tubes are diluted 100 fold for use as the standard inoculum (20,000-10,000 cells in approximately 0.002 ml. are placed on the agar surface; 20 ml. of BHI agar/dish). Twelve 2 fold dilutions of the test compound are employed, with initial concentration of the test drug being 200 mcg./ml. Single colonies are disregarded when reading plates after 18 hrs. at 37C. The susceptivility ~MIC) of the test organism is accepted as the lowest concentration of compound capable of producing complete inhibit-ion of growth as judged by the naked eye. MIC values for penicillanic acid, l,l-dioxide against several microorganisms are shown in Table I.

. . :

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d~ 7 7 3 TABLE I
In Vitro Antibacterial Activity of Penicillanic Acid 1 l-Dioxide_ Microorganism MIC (mcg./~l.) Staphylococcus aureus 100 Streptococcus faecalis~200 Streptococcus pyogenes100 Escherichia coli 50 Pseudomonas aeruginosa200 Klebsiella pneumoniae 50 Proteus mirabilis 100 Proteus morgani 100 Salmonella typhimllrium 50 Pasteurella multocida 50 Serratia marcescens 100 ~nterobacter aerogenes25 ~nterobac~er clocae 100 ~itrobacter freundii 50 Providencia 100 Staphylococcus epidermis 200 Pseudomonas putida ~200 Hemophilus influenzae~ 50 Neisseria gonorrhoeae0.312 d~7~

The compounds of the formula I, wherein Rl ls hydrogen or an ester-forming residue readily hydrolyzable in ViVO, are active as antibacterial agents in vivo. In determining such activity, acute experimental infections are produced in mice by the intraperi~oneal inoculation of the mice with a s~andardized culture of the test organism suspencled in 5 percent hog gastric mucin. Infection severity is standardized so that the mice receive one to ten times the LDloo dose of the organism (LDloo: the minimum inoculum of organism required to consistently kill 100 percent of the infec~ed, non-treated control mice). The test compound is administered to the infected mice using a multiple dosage regimen. At the end of the test, the activity of a compound is assessed by counting the number of survivors among the treatecl animals and expressing the activity of a compound as the percentage of animals which sur-vive.
'I'he in vitro antibacterial activity of the compound of the formula I
wherein Kl is hydrogen makes it useful as an industrial antimicrobial, for example in water treatment, slime control, paint preservation and wood preservation, as well as for topical application as a disinfectant. In the case of use of this compound for topical application, it is often convenient to admix the active ingredient with a non-toxic carrier, such as vegetable or mineral oil or an emollient cream. Similarly, it can be dissolved or dispersed in liquid diluents or solvents such as water, alkanols, glycols or mixtures thereof. In most instances it is appropriate to employ concentrations of the active ingredient of from about 0.1 percent to about 10 percent by weight, based on total composition.
The in vivo activity of the compounds of formula I, wherein Rl is hydrogen or an ester-forming residue readily hydrolyzable in vivo, makes them suitable for the control of bacterial infections in mammals, including ;
. ' , ' ' ' .

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man, by both the oral and parenteral modes of administration~ The compounds will find use in the control of infections caused by susceptible bacteria in human subjects, e.g. infections caused by s~rains of Neisseria ~__orrhoeae.
As indicated hereinbefore, the compounds of the formula I, wherein Rl is hydrogen or an ester-forming residue readily hydrolyzable in vivo~ are potent inhibitors of microbial ~-lactamases~ and they increase the antibacterial effec-tiveness of ~lactam antibiotics ~penicillins and cephalosporins) against many microorganisms, particularly those which produce a ~-lactamase The manner in which the said compounds of the formula I increase the effectiveness of a ~-lactam antibiotic can be appreciated by reference to experiments in which the MIC of a given antibiotic alone, and a compound of the formula I alone, are measured. These MIC's are then compared with the MIC values obtained with a combination of the given antibiotic and the compound of the formula I. When the antibacterial potency of the combination is significantly greater than would have been predicted from the potenc:ies of the individual compounds, this is considered to constitute enhancement of activity. The MIC values of combinations are measured using the metho~ described by Barry and Sabath in "Manual of Clinical Microbiology", edited by Lenette~ Spaulding and Truant, 2nd edition, 1974, American Society for Microbiology.
Results of experiments illustrating that penicillanic acid 1,1-dioxide enhances the effectiveness o ampicillin are reported in Table II.
From Table II, it can be seen that against 19 ampicillin-resistant strains of Staphylococcus aureus, the mode MIC of ampicillin, and of penicillanic acid l,l-dioxide, is 200 mcg./ml. However, the mode MIC's of ampicillin and penicillanic acid l,l-dioxide in combination are 1.56 and 3.12 mcg./ml., respectively. Looked at another way, this means that whereas ampicillin alone has a mode MIC of 200 mcg./ml. against the lg strains of Staphylococcus *~ 773 aureus~ its mode MlC is reduced to 1.56 mcg./ml. in the presence of 3.12 mcg.lml.
of penicillanic acid l,l-dioxide. The other entries in Table II show enhance-ment of the antibacterial effec~iveness of ampiciLlin against 26 ampicillin resistant strains of Haemophilus influenzae, 18 ampicillin resistant strains of Klebsiella pneumoniae, and 15 strains of the anerobe Bacteroides fragilis.
____ Table III, I~ and V show enhancement of the antibacterial potency of benzyl-penicillin (penicillin G) carbenicillin (a-carboxybenzylpenicillin) and cefazolin, respectively, against strains of S. aureus, Il. influ~nzae, K. p~u~oniae and Baceroides fragilis.

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g x a o ."
~1 ~: r-l Il~ O U~ ~
O ~ ¢ ~ `1 4 ~ ~ ~ . n~ _ ~ H O .~ N 11~ U) a o N r~ N
~ ~ r-l 4-1 O ~) ~4 ~D
a ~8~ ~ .
r1 o~ a>
H ~
~1~ rl ~rl O ~
x ~ ~
a ~ ~ ~ g o o o o P' l o 9 ~ u~

' h 4~
~j r~ t~
~1 ~ r~~ ~ 00 ~rl ~ ~ ~ ~
~1 0 N g O
t~ ¢ ~I N
~H ., ~~0~
Z N N ~-1 ' ~J~773 Thus the compounds of the formula I, wherei.n Rl is hydrogen or an ester-forming residue readily hydrolyzable ]n vivo, enhance the antibacterial effectiveness of ~-lactam antibiotics in vivo. That is, they lower the amount of the antibiotic which is needed to protect mice against an otherwise lethal inoculum of certain ~--lactamase producing bacteria.
The ability of the compounds of the formula I, wherein Rl is hydrogen or an ester-forming residue readily hydrolyzable in vivo, to enhance the effectiveness of a ~ lactam antibiotic against ~-lactamase-producing bacteria makes then valuable for co-adminstration with ~-lactam antibiotics in the treatment of bacterial infections in mannals, particularly man. In the treat-ment of a bacterial infection, the said compound of the formula I can be comingled with the ~-lactam antibiotic, and the two agents thereby adminstered simultaneously. Alternatively, the said compownd of the formula I can be administered as a separate agent during a course of treatment with a ~-lactam antibiotic. In some instances it will be advantageous to pre-dose the subject with the compound of the formula I before initiating treatment with a ~-lactam antibiotic.
~ortherapeutic useof compositions according to theinvention in a mammal, particularly man, the compositions can be administered alone, or they can be mixed with pharmaceutically acceptable carriers or diluents.
They can be administered orally or parenterally, i.e. intramuscularly, sub-cutaneously or intraperitwleally. The carrier or diluent is chosen on the basis of the intended mode of administration. For example, when considering the oral mode of administration, an antibacterial penam compound of this in-vention can be used in the form of tablets, capsules, lozenges, troches, powders, syrups, elixirs, aqueous solutions and suspensions~ and the like, in accordance with standard pharmaceutical practice. The proportional ratio of active in-~ ~ ?,~7~3 :

gredients to carrier will naturally depend on the chemical nature~ solubility and stability of the active in~redient, as well as the dosage conternplated.
In the case of tablets for oral use, carriers which are commonly used include lactose, sodium citrate and salts of phosphoric acid. Various disintegrants such as sta~ch, and lubricating agents, such as magnesium stearate, sodium lauryl sulfate and talc, are commonly used in tablets. For oral administration in capsule form, useful diluents are lactose and high molecular weight poly-ethylene glycols. When aqueous suspensions are required for oral use, the active ingredient is combined with emulsifying and suspending agents. If 10 desired, certain sweetening and/or flavoring agents can be added. For paren-teral administration, which includes intramuscular, intraperitoneal, sub-cutaneous and intravenous use, sterile solutions of the active ingredient are usually prepared, and the p~l of the solutions are suitably acljusted and bu~ered. ~or intravenous use, the total concentation of so:Lutes should be controlled to render the preparation isotonic.
A pharmaceutical composition comprising a pharmaceutically-acceptable carrier, a ~-lactam antibiotic and penicillanic acid l,l-dioxide or a readily hydrolyzable ester thereof will normally contain from about 5 to about 80 percent of the pharmaceutically acceptable carrier by weight.
When using penicillanic acid l,l-dioxide or an ester thereof readily hydrolyzable _ vivo in combination with another ~-lactam antibiotic, the sulfone can be administered orally or parenterally, i.e. intramuscularly, sub-cutaneously or intraperitoneally. Although the prescribing physician will ultimately decide the dosage to be used in a human subject, the ratio of the daily dosages of the penicillanic acid l,l-dioxide or ester thereof and the ~-lactam antibiotic will normally be in the range from about 1:3 to 3:1.
Additionally, when using penicillanic acid l,l-dioxide or an ester thereof : . .
. . ' .

readily hydrolyzable in vivo in combinat:ion wlth another ~-lactam antibiotic, the daily oral dosage of each component will normally be in the range from about 10 to about 200 mg. per kilogram of body weight and the daily parenteral dosage of each component will normally be about 10 to about 400 mg. per kilogram of body weight. These figures are illustrative only, however, and in some cases it may be necessary to use dosages outside these limits.
Typical ~-lactam antibiotics with which penicillanic acid l,l-dioxide and its esters readily hydrolyzable in vivo can be co-administered are:
6-(2-phenylacetamido)penicillanic acid, 6-~2-phenoxyacetamido)penicillanic acid, 6-(2-phenylpropionamido)penicillanic acid, 6-(D-2-amino-2-phenylacetamido)penicillanic acid, 6-(D-2-amino-2-[4-hydroxyphenyl]acetamido)penicillanic acid, 6-(D-2-amino-2-[1,4-cyclohexadienyl]acetamido)penicillanic acid, 6-(1-aminocyclohexanecarboxamido)penic:illanic acid, 6-~2-carboxy-2-phenylacetamido)penicillanic acid, 6-(2-carboxy-2-[3-thienyl]acetamido)penicillanic acid, 6-(D-2-C4-ethylpiperazin-2,3-dione-l-carboxamido]-2-phenylacetamido)penicillanic acid, 6-(D-2-[4-hydroxy-1,5-naphthyridine-3-carboxamido]-2-phenylacetamido)penicillanic acid, 6-(D-2-sulfo-2-phenylacetamido)penicillanic acid, 6-(D-2-sulfoamino-2-phenylacetamido)penicillanic acid, 6-(D-2-[imidazolidin-2-one-1-carboxamido]-2-phenylacetamido)-penicillanic acid, 6-(D-L3-methylsulfonylimidazolidin-2 one-1-carboxamido]-2-phenylacetamido)-penicillanic acid, 6-~[hexahydro-lH-azepin-l-yl]methyleneamino)penicillanic acid, acetoxymethyl 6-(2-phenylacetamido)penicillanate, - ~773 acetoxymethyl 6-(D-2-amino-2-phenylacetamido)penicillanate, acetoxymethyl 6-~D-2-amino-2-[4-hydroxyphenyllacetamido)penicillanate, pivaloyloxymethyl 6-(2-phenylacetamido)penicillanate, pivaloyloxymethyl 6-(D-2-amino-2-phenylacetamido)penicillanate, pivaloyloxymethyl 6-(D-2-amino-2-[4-hydroxyphenyl]acetamido)penicillanate, l-~ethoxycarbonyloxy)ethyl 6-~2-phenylacetamido)penicillanate, l-~ethoxycarbonyloxy)ethyl 6-~D-2-amino-2-phenylacetamido)penicillanate, l-~ethoxycarbonyloxy)ethyl 6-(D-2-amino-2-[4-hydroxyphenyl)acetamido)penicil-lanate, 3-phthalidyl 6-~2-phenylacetamido)penicillanate, 3-phthalidyl 6-~D-2-amino-2-phenylacetamido)penicillanate, 3-phthalidyl 6-~D-2-amino-2-[~-hydroxyphenyl]acetamido)penicillanate, 6-(2-phenoxycarbonyl-2-phenylacetamido)penicillanic acid, 6-~2-tolyloxycarbonyl-2-phenylacetamido)penicillanlc acid, 6-~2-[5-indanyloxycarbonyl]-2-phenylacetamido)penic:illanic acid, 6-(2-phenoxycarbonyl-2-[3-thienyllacetamido)penicillanic acid, 6-(2-tolyloxycarbonyl-2-[3-thienylJacetamido)penicillanic acid, 6-~2-[5-indanyloxycarbonyl]-2-[3-thienyl]acetamido)penicillanic acid, 6-(2,2-dimethyl-5-oxo-4-phenyl-1-imidazolidinyl)penicillanic acid, 7-(2-[2-thienylJacetamido)cephalosporanic acid, 7-~2-[1-tetrazolyl]acetamido-3-(2-[5-methyl-1,3,4-thiadiazolyl]thiomethyl)-3-desacetoxymethylcephalosporanic acid, 7-(D-2-amino-2-phenylacetamido)desacetoxycephalosporanic acid, 7-~-methoxy-7-(2-[2-thienyl]acetamido)-3-carbamoyloxymethyl-3-desacetoxymethyl-cephalosporanic acid, 7-(2-cyanoace~amido)cephalosporanic acid, 7-~D-2-hydroxy-2-phenylacetamido)-3-(5-[1-methyltetra~olyl]thiomethyl)-3-desacetoxymethylcephalosporanic acid, .
' ~ ' : . , 7~3 7-(2-[~-pyridylthio]acetamido)cephalosporanic acid, 7-(D-2-amino-2-[l~4-cyclohexadienyl] ~c~tam~ c~phal~s~o~ani~ ~cid 9 7-(D-2-amino-2-phenylacetamido)cephalosporanic acid, and the pharmaceutically-acceptable salts thereof.
As will be appreciated by one skilled in the art, some of the above ~-lactam compounds are effective when administered orally or parenterally, while others are effective only when administered by the parenteral route. When penicillanic acid l,l-dioxide or an ester thereof readily hydrolyzable in vivo is to be used simultaneously (i.e. co-mingled) with a ~-lactam antibiotic which is effective only on parenteral administration, a combination formulation suit-able for parenteral use will be required. When the penicillanic acid l,l-dioxide or ester thereo is to be used simultaneously (co-mingled) with a ~-lactam cmtibiotic which is effective orally or parenterally, combinations suitable for either oral or parenteral administration can be prepared. Additionally, it is possible to administer preparations of the penicillanic acid l,l-dioxide or ester thereof orally, while at the same time administering a further ~-lactam antibiotic parenterally; and it is also possible to administer preparations of the penicillanic acid l,l-dioxide or ester thereof parenterally,w~lle at the same time administering the further ~-lactam antibiotic orally.
The following examples are provided solely for the purpose of further illustration. Infrared (IR) spectra were measured as potassium bromide discs ~KBr discs) or as Nujol mulls, and diagnostic absorption bands are reported in wave numbers (cm 1). Nuclear magnetic resonance spectra (NMR) were measured at 60 MHz for solutions in deuterochloroform (CDC13), perdeutero dimethyl sul-foxide (DMS0-d6) or deuterium oxide (D20), and peak positions are expressed in parts per million (PPM) downfield from tetramethylsilane or sodium 2,2-dimethyl-2-silapentane-5-sulfonate. The following abbreviations for peak *

Trademark `

shapes are used: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet.
EXA~IPLE I
Penicillanic Acid 1,1-Dioxide To a solution of 6.51 g. (41 mmole) of potassium permanganate in 130 ml. of water and 4.95 ml. o~ glacial acetic acid~ cooled to ca. 5C., was added a cold (ca. 5C.) solution of 4.58 g. ~21 mmole) of the sodiu~
salt of penicillanic acid in 50 ml. of water. The mixture was stirred at ca.
5C. for 20 minutes and then the cooling bath was removed. Solid sodium bisulfite was added until the color of the potassium permanganate had been discharged, and then the mixture was filtered. To the aqueous filtrate was added half its volume of saturated sodium chloride solution, and then the pH was adjusted to 1.7. The acidic solution was extracted with ethyl acetate. The extracts were dried, and then evaporatecl in vacuo, to give 3.47 g. of the title product. The aqueous mother liquor was saturated with sodium chloride, and further extracted with ethyl acetate. The ethyl acetate solution was dried and evaporated in vacuo, to give a further 0.28 g. of product. The total yleld was therefore 3.75 g. (78% yield). The NMR spectrum (DMS0-d6) o~ the product showed absorptions at 1.40 (s,3H), 1.50 ~s,3H), 3.13 ~d of d's, lH, Jl = 16Hæ, J2 = 2Hz), 3.63 (d of d's, lH, Jl = 16 Hz, J2 = 4Hz), 4.22 (s, lH) and 5.03 (d of dts, lH, Jl Z 4Hz, J2 Z 2Hz) ppm.

Benzyl Penicillanate l,l-Dioxide To a stirred solution of 6.85 g. (24 mmole) of benzyl penicillanate in 75 ml. of ethanol-free chloroform, under nitrogen, in an ice-bath, was added in two portions, several minutes apart, 4.78 g. of 85% pure 3-chloro-perbenzQic acid. Stirring was continued for 30 minutes in the ice-bath, and then for 45 minutes without external cooling. The reaction mixture was 7~3 washed with aqueous alkali (pll 8.5), followed by saturated sodium chloride~
and then it was dried and evaporated in vacuo to give 7.05 g. of residue.
Examination of this residue showed it to be a 5.5 1 mixture of benzyl penicil-lanate l-oxide and benzyl penicillanate l,l-dioxide.
To a stirred solution of 4.85 g. of the above 5.5:1 sulfoxide-sulfone mixture in 50 ml. of ethanol-free chloroform, under nitrogen, was added 3.2 g. of 85% pure 3-chloroperbenzoic acid at room temperature. The reaction mixture was stirred for 2.5 hours, and then it was dilutecl with ethyl acetate. The resultant mixture was added to water at pH 8.0, and then 10 the layers were separated. The organic phase was washed with water at pH 8.0, followéd by saturated sodium chloride, and then it was dried using sodium sulfate. Evaporation of the solvent in vacuo afforded 3.59 g. of the title compound. The NMR spectrum of the product (in CDC13) showed absorptions at 1.28 (s, 3~1), 1.58 (s,311), 3.42 ~m,2~1), 4.37 (s,lll), 4,55 (m,l~l), 5.18 (q,2~1, J = 12 llz) and 7.35 (s,51l) ppm.
~XAMPLE3 3 Penicillanic Acid l,l-Dioxide To a stirred solution of 8.27 g. of benzyl penicillanate l,l-dioxide in a mixture of 40 ml. of methanol and lO ml. of ethyl acetate was slowly added lO ml. of water, followed by 12 g. of 5% palladium-on-calcium carbonate. The mixture was shaken under an atmosphere of hydrogen, at 52 psi, for 40 minutes, and then it was filtered through supercel (a diatomaceous earth). The filter cake was washed with methanol, and with aqueous methanol, and the washings were added to the filtrate. The combined solution was evaporated in vacuo to remove the majority of the organic solvents and then the residue was partitioned between ethyl acetate and water at a pH of 2.8. The ethyl acetate layer was removed and the aqueous phase 7;3 was further extractecI with ethyl acetate. The combined ethyl acetate solutions were washed with saturated sod:ium chloride solution, dried using sodium sul-fate and then evaporated in vacuo. The residue was slurried in a 1:2 mixture of ethyl acetate-ether, to give 2.37 g. of the title product having a melting point of 148-51C. The ethyl acetate-ether mixture was evaporated giving a further 2.17 g. of product.

Pivaloyloxymethyl Penicillanate _ l,l-Dioxide To 0.615 g. (241 mmole) of penicillanic acid l,l-dioxide in

2 ml. of N,N-dimethylformamide was added 0.215 g. (2.50 mmole) of diiso-propylethylamine followed by 0.365 ml. of chloromethyl pivalate. The reaction mixture was stirred at room temperature for 24 hours, and then it was diluted with ethyl acetate and water. The ethyl acetate layer was separated and washed three times with water and once with saturated sodium chloride solution.
The ethyl acetate solution was then dried using anhydrous sodium sulfate, and evaporated in vacuo to give 0.700 g. of the title product as a solid, mp 103-4C. The NhIR spectrum of the product (in CDC13) showed absorptions at 1.27 (s, 9H), 1.47 (s, 3H), 1.62 (SJ 3H), 3.52 ~m, 211)7 4.47 (s, lH), 4.70 (m, lH), 5.73 (d, lH, J = 6.0 Hz) and 5.98 (d, lH, J = 6.0 H~) The procedure of Example 4 is repeated, except that the pivaloyloxy methyl chloride used therein is replaced by an equimolar amount of acetoxy-methyl chloride, propionyloxymethyl chloride and hexanoyloxy~ethyl chloride, respectively, to give:
acetoxymethyl penicillanate l,l-dioxide, propionyloxymethyl penicillanate l,l-dioxide and hexanoyloxymethyl penicillanate l,l-dioxide, respectively.

~..?~7'7~

EXA~IPLE ~

3-Phthalidyl Penicillanate l,l-Dioxide .
To 0.783 g. (3.36 mmole) of penicillanic acid l,l-dioxide in 5 ml.
of N,N-dimethylformamide was added 0.47 ml. of ~riethylamine followed by 0.715 g. of 3-bromophthalide. The reaction mixture was stirred for 2 hours at room temperature and then it was diluted with ethyl acetate and water.
The pH of the aqueous phase was raised to 7.0 and the layers were separated.
The ethyl acetate layer was washed successively with water and saturated sodium chloride solution, and then it was dried using sodium sulfate. The ethyl acetate solution was evaporated ln vacuo leaving the title product as a white foam. The NMR spectrum of the product (in CDC13) showed absorptions at 1.47 (s, 6H), 3.43 (m. lH), 4.45 (s, lH), 4.62 (m, lH), 7.40 and 7.41 (2s's, ltl) and 7.73 (m, 4H) ppm.
When the above procedure is repeated, except that the 3-bromophthalide is replaced by 4-bromocrotonolactone and 4-bromo-y-butyrolactone, respectively, this affords: 4-crotonolactonyl penicillanate l,l-dioxide and y-butyrolacton-

4-yl penicillanate, respectively.
EXAMP~E 7 l-(Ethoxycarbonyloxy)ethyl Penicillanate l,l-Dioxide A mixture of 0.654 g. of penicillanic acid l,l-dioxide, 0.42 ml.
of triethylamine, 0.412 g. of l-chloroethyl ethyl carbonate, 0.300 g. of sodium bromide and 3 ml. of -N,N-dimethylfo~amide was stirred at room temperature for 6 days. It was then worked up by diluting it with ethyl acetate and water, and then the pH was adjusted to 8.5. The ethyl acetate layer was separated, washed three times with water, washed once with saturated sodium chloride, and then it was dried using anhydrous sodium sulfate. The ethyl acetate was removed by evaporation in vacuo leaving 0.390 g. of the title ' 37~;3 product as an oil.
The above product was combined with an approximately equal amount of similar material from a similar experiment. The combined product was dissolved in chloroform and 1 ml~ of pyridine was added. The mixture was stirred at room temperature overnight and then the chloroform was removed by evaporation in vacuo. The residue was partitioned between ethyl acetate and water at p~ 8. The separated and dried ethyl acetate was then evaporated in vacuo to give 150 mg. of the ti~le product ~yield ca 7%). The IR spectrum (film) of the product showed absorptions at 1805 and 1763 cm 1. The ~MR
spectrum (CDC13) showed absorptions at 1.43 (m, 12H), 3 47 (m, 2H), 3.9 (q, 2H, J = 7.5 Hz), 4.37~m, lH), 4.63 (m, lH) and 6.77 ~m, lH) ppm.
~XAMPLE ~
The procedure of ~xample 7 is repeated, except that the l-chloroeth-yl ethyl carbonate is replaced by an equimolar amount of the appropriate 1-chloroalkyl alkyl carbonate, l-(alkanoyloxy)ethyl chloride or l-methyl-l-(alkanoyloxy)ethyl chloride, to produce the following compounds:
methoxycarbonyloxymethyl penicillanate l~l-dioxide, ethoxycarbonyloxymethyl penicillanate l,l-dioxide, isobutoxycarbonyloxymethyl penicillanate l,l-dioxide, l-(methoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(butoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(acetoxy)ethyl penicillanate l,l-dioxide, l-(butyryloxy)ethyl penicillanate l,l-dioxide, l-~pivaloyloxy)ethyl penicillanate l,l-dioxide, l-(hexanoyloxy)ethyl penicillanate l,l-dioxide, l-methyl-l-(acetoxy)ethyl penicillanate l,l-dioxide and l~methyl-l-(isobutyryloxy)ethyl penicillanate l,l-dioxide, respectively.

7~3 ~:X~M~LE 9 The procedure of Example 4 is repeated, except that the chloromethyl pivalate is replaced by an equimolar amount of benzl bromide and 4-nitrobenzyl bromide, respectively~ to produce benzyl penicillanate l,l-dioxide and 4-nitro-benzyl penicillanate l,l-dioxide, respectively.
EXA~IPLE 10 Penicillanic Acid l~-Oxide To 1.4 g. of prehydrogenated 5% palladium-on-calcium carbonate in 50 ml. of water was added a solution of 1.39 g. of benzyl 6,6-dibromopenicilla-nate l~-oxide in 50 ml. of tetrahydrofuran. The mixture was shaken under an atmosphere of hydrogen at ca. 45 p.s.i. and 25C. for 1 hour, and then it was filtered. The filtrate was evaporated in vacuo to remove the bulk of the tetrahydrofuran, and then the aqueous pIIase was extracted with ether. 'I'he flther extracts were evaporated ln vacuo to give 0.5 g. of material W}IiC}I ap-peared to be largely benzyl psnicillanate l~-oxide.
l'he above benzyl penicillanate l~-oxide was combined with a further 2.0 g. of benzyl 6,6-dibromopenicillanate l~-oxide and dissolved in 50 ml. of tetrahydrofuran. The solution was added to 4.0 g. of 5% palladium-on-calcium carbonate, in 50 ml. of water, and the resulting mixture was shaken under an atmosphere of hydrogen, at ca. 45 p.s.i. and 25C. overnight. The mixture was filtered, and the filtrate was extracted with ether. The extracts were evaporated in vacuo, and the residue was purified by chromatography on silica gel, eluting with chloroform. This afforded 0.50 g. of material.
The latter material was hydrogenated at ca. 45 p.s.i. at 25C.
in water-methanol (1:1) with 0.50 g. of 5% palladium-on-calcium carbonate for 2 hours. At this point, an additional 0.50 g. of 5% palladium-on-calcium car-bonate was added and the hydrogenation was continued at 45 p.s.i. and 25C.

~ f~'~7~

overnight. I`he reaction mixture was filteredJ extracted with ether and the ex-tracts were discarded. The residual aqueous phase was adjusted to p~I 1.5 and then extracted with ethyl acetate. The ethyl acetate extracts were dried (Na2SO4) and then eva~orated in vacuo to give 0.14 g. of penicillanic acid la-oxide. The NMR spectrum (CDC13/DMSO-d6) showed absorptions at 1.4 (s, 3H), 1.64 (s, 3H~, 3.60 (m, 2BI), 4.3 (s, lH) and 4.54 {m, lH)ppm. The IR spectrum of the product ~KBr disc) showed absorptions at 1795 and 1745 cm 1 ; Penicillanic Acid l~-Oxide To l.O g. of prehydrogenated 5% palladiurn-on-calcium carbonate in 30 ml. of water is added a solution of 1.0 g. of 6,6-dibromopenicillanic acid l~-oxide. The mixture is shaken under an atmosphere of hydrogen, at ca. 45 p.s.i. and 25C. J for 1 hour. The reaction mixture is then filtered and the filtrate is concentrated in vacuo to remove the methanol. The residual aqueous phase is diluted with an equal volume of waterJ adjusted to pll 7J and washed with ether. The aqueous phase is then acidified to pll 2 with dilute hydro-chloric acid and extracted with ethyl acetate. The ethyl acetate extracts are dried (Na2SO4) and evaporated in vacuo to give penicillanic acid l~-oxide.

Penicillanic Acid l~-Oxide To a stirred solution of 2.65 g. (12.7 mmole) of penicillanic acid in chloroform at 0C. was added 2.58 g. of 85% pure 3-chloroperbenzoic acid.
After 1 hourJ the reaction mixture was filtered and the filtrate was evaporated in vacuo. The residue was dissolved in a small amount of chloroform. The solution was concentrated slowly until a precipitate began to appear. At this point the evaporation was stopped and the mixture was diluted with ether. The precipitate was removed by filtration, wa~hed with ether and dried, to give 0.615 g. o penicillanic acid l~-oxide, m.p. 140-3C. The IR spectrwn of the ~ ~ ~J'~ 7 ~ ~

product (C~IC13 solution}showed absorptions at 1775 and 1720 cm 1. The NMR
spectrum (CDC13/~hI~O-d6) showed absorptions at 1.35 (s, 3~I}, 1.76 (s, 3~I~, 3.36 (m, 2~1), 4.50 (s, l~I) and 5.05 (III, lII)ppm. Frvm t;he N~ spectrum, the product appeared to be ca. 90% pure.
Examination of the chloroform-ether mother li4uor revealed that it contained further penicillanic acid l~-oxide, and also some penicillanic acid l~-oxide.

Esterification o~ penicillanic acid l~-oxide or penicil:Lanic acid l~-oxide, as appropriate, with the requisite alkanoyloxy chloride, according to Example 5, provides the following compounds:
acetoxymetllyl penicillanate l~-oxide, propionyloxymethyl pen^cillanate l~-oxide, pivaloyloxymethyl peniclllanatel~-oXide, acetox~lethyl penicillanate 1~-oxide, propionyloxymethyl penicillanate l~-oxide and pivaloyloxymethyl penicillanate l~-oxide, respectively.

Reaction of penicillanic acid l~-oxide or penicillanic acid l~-oxide with 3-bromophthalide, ~-bromocrotonolactOne or 4-bromo-y-butyrolactone, as appropriate, affords the following compounds:
3-phthalidyl penicillanate l~-oxide 4-crotonolactonyl penicillanate l~-oxide, 3-phthalidyl penicillanate l~-oxide, ~-crotonolactonyl penicillanate l~-oxide and y-butyrolacton-4-yl penicillanate l~-oxide, respectively.

-' ~

~?~

E~PLE 15 Reaction of penicillanic acid la-oxide or pcnicillanic acid l~-oxide, as appropriate, with the requisite l-chloroalkyl alkyl carbonate or l-(alkanoyl-oxy)ethyl chloride, according to the procedure of Example 7, provides the ~ol-lowing compounds.
l-(ethoxycarbonyloxy~ethyl penicillanate la-oxide, methoxycarbonyloxymethyl penicillanate la-oxide, ethoxycarbonyloxymethyl penicillanate la-oxide, isobutoxycarbonyloxymethyl penicillanate la-oxide, l-(methoxycarbonyloxy)ethyl penicillanate la-oxide, l-(butoxycarbonyloxy)ethyl penicillanate la-oxide, ; l-(acetoxy)ethyl penicillanate la-oxide, l-Ibutyryloxy)ethyl penicillanate la-oxide, l-(pivaloyloxy)ethyl penicillanate la-oxide, l-(ethoxycarbonyloxy)ethyl penicillanate l~-oxide, methoxycarbonyloxymethyl penicillanate l~-oxide, ethoxycarbonyloxymethyl penicillanate l~-oxide, isobutoxycarbonyloxymethyl penicillanate l~-oxide, l-(methoxycarbonyloxy)ethyl penicillanate l~-oxide, l-(butoxycarbonyloxy)ethyl penicillanate l~-oxide, l-(acetoxy)ethyl penicillanate 1~ oxide, l-(butyryloxy)ethyl penicillanate l~-oxide and l-(pivaloyloxy)ethyl penicillanate l~-oxide, respectively.

Reaction of penicillanic acid la-oxide and penicillanic acid l~-oxide with benzyl bromideJ according to the procedure of Example 4, produces benzyl :

. .

penicillanate l~-oxide and benzyl penicillanate l~-oxide, respectively.
In like manner, reaction of penicillanic acid l~-oxide and penicillan-ic acid l~-oxide wi~h 4-nitrobenzyl bromide, according to the procedure of Example 4, produces 4-nitrobenzyl penicillanate l~-oxide and 4-nitrobenzyl penicillanate l~-oxide, respectively.

Penicillanic Acid l,l-Dioxide To 2.17 g. (10 m~ole) of penicillanic acid l~-oxide in 30 ml. of ethanol-free chloroform at ca. 0C. is added 1.73 g. (10 mmole) of 3-chloroper-benzoic acid~ The mixture is stirred for 1 hour at ca. 0C. and then for an additional 24 hours at 25C. The filtered reaction mixture is evaporated in vacuo to give penicillanic acid l,l-dioxide.

The procedure of ~xample 17 is repeated, except that the penicillanic acid l~-oxide used therein is replaced by:
penicillanic acid l~-oxide7 acetoxymethyl penicillanate l~-oxide, - propionyloxymethyl penicillanate l~-oxide, pivaloyloxymQthylpeniGillanate l~-oxide, acetoxymethyl penicillanate l~-oxideJ
propionyloxymethyl penicillanate l~-oxide, pivaloyloxymethyl penicillanate l~-oxide, 3-phthalidyl penicillanate l~-oxide, 3-phthalidyl penicillanate l~-oxide, l-~ethoxycarbonyloxy)ethyl penicillanate l~-oxide, methoxycarbonyloxymethyl penicillanate l~-oxide, ethoxycarbonyloxymethyl penicillanate l~-oxide, ~?J,~7~3 isobutoxycarbonyloxymethyl penicillanate l~-oxide, l-(methoxycarbonyloxy)ethyl penicillanate l~-oxide, l-~butoxycarbonyloxy)ethyl penicillanate la-oxide, l-(acetoxy)ethyl penicillanate l~-oxide, l-(butyryloxy)ethyl penicillanate la-oxide, l-(pivaloyloxy)ethyl penicillanate l~-oxide, l-(ethoxycarbonyloxy)ethyl penicillanate l~-oxide, methoxycarbonyloxymethyl penicillanate l~-oxide, ethoxycarbonyloxymethyl penicillanate l~oxide, isobutoxycarbonyloxymethyl penicillanate l~-oxide, l-(methoxycarbonyloxy)ethyl penicillanate l~-oxide, l-(butoxycarbonyloxyjethyl penicillanate l~-oxide, l-(acetoxyjetilyl penicillanate l~-oxide, l-(butyryloxy)ethyl penicillanate l~-oxide and l-(pivaloyloxy)ethyl penicillE~nate l~-oxide, respectively. This affords:
penicillanic acid l,l-dioxide, acetoxymethyl penicillanate l,l-dioxide, propionyloxymethyl penicillanate l,l-dioxide, pivaloyloxymethyl.penicillanatel,l-dioxide, acetoxymethyl penicillanate l,l-dioxide, propionyloxymethyl penicillanate l,l-dioxide, pivaloyloxymethyl penicillanate l,l-dioxide, 3-phthalidyl penicillanate l,l-dioxide, 3-phthalidyl penicillanate l,l-dioxide, l-(ethoxycarbonyloxy)ethyl penicillanate l,l-dioxide, methoxycarbonyloxymethyl penicillanate l,l-dioxide, . ~

7~3 ethoxycarbonyloxymethyl penicillanate l,l-dioxide~
isobutoxycarbonyloxymethyl penicillanate l,l-diox:ide, l-(methoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(butoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(acetoxy)ethyl penicillanate l,l-dioxide, l-(butyryloxy)ethyl penicillanate lgl-dioxide, l-~pivaloyloxy)ethyl penicillanate l,l-dioxide, l-(ethoxycarbonyloxy)ethyl penicillanate l,l-dioxide, methoxycarbonyloxymethyl penicillanate l,l-dioxide, ethoxycarbonyloxymethyl penicillanate l,l-dioxide, isobutoxycarbonyloxymethyl penicillanate l,l--dioxide, l-(methoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(butoxycarbonyloxy)ethyl penicillanate l,l-dioxide, l-(acetoxy)ethyl penicillanate l,l--dioxide, l-tbutyryloxy)ethyl penicillanate l,l-dioxide and l-(pivaloyloxy)ethyl penicillanate l,l-dioxide, respectively.
EXA~PLE 19 Oxidation of benzyl penicillanate l~-oxide and benzyl penicillanate l~-oxide with 3-chloroperbenzoic acid, according to the procedure of Example 17, produces, in each case, benzyl penicillanate l,l-dioxide.
In like manner, oxidation of 4-nitrobenzyl penicillanate l~-oxide and 4-nitrobenæyl penicillanate l~-oxide with 3-chloroperbenzoic acid, accord-ing to the procedure of Example 17, produces 4-nitrobenzyl penicillanate 1,1-dioxide.
EXAMPLE 2~
Penicillanic Acid l,I-Dioxide Hydrogenolysis of 4-nitrobenzyl penicillanate l,l-dioxide, according ~L3L;~37~3 to the procedure of Example 3, affords penicillanic acid l,l-dioxide.

Sodium Penicillanate l,l-Dioxide To a stirred solution of 32.75 g. ~0.14 mole) of penicillanic acid l,l-dioxide in 450 ml. of ethyl acetate was added a solution of 25.7 g. of sodium 2-ethylhexanoate (0.155 mole) in 200 ml. of ethyl acetate. The resulting solution was stirred for 1 hour and then an additional 10% excess of sodium 2-ethylhexanoate in a small volume of ethyl acetate was added. Product immedi-ately began to precipitate. Stirring was continued for 30 minutes and then the precipitate was removed by filtration. It was washed sequentially with ethyl acetate, with 1:1 ethyl acetate-ether and with ether. ~he solid was then dried over phosphorus pentoxide, at ca. 0.1 mm of Hg for 16 hours at 25C., giving 36.8 g. of the title sodium salt, contaminated with a snlall amount of ethyl acetate. The ethyl acetate content was reduced by heating to 100C. for 3 hours under vacuum. Thc IR spectrum oE this Einal product ~KBr disc) showed absorptions at 1786 and 1608 cm 1. The NMR spectrum (D20) showed absorptions at 1.48 (s, 3H), 1.62 (s, 3H), 3.35 (d of d's, l~E, Jl = 16Hz, J2=2Hz), 3.70 (d of d's, lH, Jl=16Hz, J2=4Hz), 4.25 ~s, lH) and

5.03 ~d of d's, lH, Jl=4Hz, J2=2Hz)ppm.
The title sodium salt can also be prepared using acetone in place of ethyl acetate.

F:XAMPLE 22 Penicillanic Acid l,l-Dioxide To a mixture of 7,600 ml. of water and 289 ml. of glacial acetic acid was added, portionwise, 379.5 g. of potassium permanganate. This mixture was ;~ stirred for 15 minutes, and then it was cooled to 0C. To it was then added, with stirring, a mixture which had been prepared from 270 g. of penicillanic acid, 260 ml. of 4N sodium hydroxide and 2,400 ml. of water ~pH 7.2), ' . :' and which had then been cooled to 8C. The tempera~ure rose to 15C. during this latter addition. The temperature of the resuLting mixture was reduced to 5C. and the stirring was continued for 30 minutes. To the reaction mixture was then added 142.1 g. of sodium bisulfite, in portions, during lO
minutes. The mixture was stirred for 10 minutes at lO~C., and then 100 g.
of supercel (a diatomaceous earth) was added. After a further 5 minutes of stirring, the mixture was filtered. To the filtrate was added 4.0 liters of ethyl acetate, and then the pH of ~he aqueous phase was lowered to 1.55 using 6N hydrochloric acid. The ethyl acetate layer was removed and combined with several further ethyl acetate extracts. The combined organic layer was washed with water, dried (MgS04) and evaporated almost to dryness ~n vacuo.
The slurry thus obtained was stirred with 700 ml. of ether at 10C., for 20 minutes, and then the solid was collected by filtration. This afforded 82.6 g. (26% yield) of the title compound having a melting point o 154-155.5 C. (dec.).

Pivaloyloxymethyl Penicillanate l,l-~ioxide To a solution of 1.25g. pivaloyloxymethyl penicillanate in 40 ml.
of chloroform, cooled to ca. -15C., was added 0.8 g. of 3-chloroperbenzoic acid. The mixture was stirred at CcL. -15C. for 20 minutes and then it was allowed to warm to room temperature. Analysis of the resulting solution by NMR illdicated that it contained both the 1~- and l~-oxide.
The chloroform solution was concentrated to about 20 ml. and a further 0.8 g. of 3-chloroperbenzoic acid was added. This mixture was stirred overnight at room temperature, and then all the solvent was removed by evaporation in vacuo. The residue was redissolved in ca 4 ml. of dichloro-methane and 0.4 g. of 3-chloroperbenzoic acid was added. The mixture was ~?~ 7~

stirred for 3 hours and then the solvent was removed by evaporation in vacuo.
The residue was partitioned between ethyl acetate and water at pH 6.0~ and sodium bisulfite was added until a test for the prPsence of peroxides was negative. The pH of the aqueous phase was raised to 8.0 and the layers were separated. The organic layer was washed with brine, dried using anhydrous sodium sulfate and evaporated in v cuo. The residue was dissolved in ether and reprecipitated by the addition of hexane. The resulting solid was recrystal-lized from ether to give 0.357 g. of the title compound.
The NMR spectrum of the product (CDC13) showed absorptions at 1.23 ~s,9H), 1.50(s,3H), 1.67 (s,3H), 3.28 (m,2H), 4.45(s,1~1), 5.25 (m,lH) and 5.78 (m,2~1)ppm.

3-Phthalidyl Penicillanate l,l-Dioxide To a solution of 7.3 mg. oE 3-phthalidyl penicillallate in 3 ml.
of chloroform was added 0.43~ g. of 3-chloroperbenzoic acid at ca. 10C.
The Inixture was stirred for 30 minutes and then a further 0.513 g. of 3-chloroperbenzoic acid was added. The mixture was stirred for 4 hours at room temperature, and then the solvent was removed by evaporation in vacuo.
The residue was partitioned between ethyl acetate and water at pH 6.0~ and sodium bisulfite was added to decompose any remaining peracid. The pH
of the aqueous phase was raised to 8.8. The layers were separated and the organic phase was evaporated in vacuo. This aEforded the title compound as a foam. The NMR spectrum (CDC13) sho~edabsorptions at 1.62 (m,6H), 3.3(m,2H)~
4.52 (p,lH), 5.23~m,1H) and 7.63 (m,5H)ppm.

2,2,2-T chIoroethyl Penicillanate l,l-Dioxide To 100 mg. of 2,2,2-trichloroethyl penicillanate in a small volume of chloroform was added 50 mg. of 3-chloroperbenæoic acid and the mixture was stirred for 30 minutes. Examination of the reaction product at this point revealed that it was mostly sulfoxide (The NMR spectrum ~CDG13) showed absorptions at 1.6 (s,3H), 1.77 (s,3H), 3.38(m,2H), 4.65 (s~lH), 4.85 (m,2H) and 5.37 (m,l~l)ppm.) A further lO0 mg. of 3-chloroperbenzoic acid was added and the mixture was stirred overnight. The solvent was then removed by evaporation in vacuo, and the residue was partitioned between ethyl acetate and water at pH 6Ø Sufficient sodium bisulfite was added to decompose the excess peracid and then the p~I was raised to 8.5. The organic phase was separated, washed with brine and dried. Lvaporation in vacuo afforded 65 mg.
of the title product. The NMR spectrum (CDC13) showedabsorptions at 1.53 (s,3H), 1.72(s,3H), 3.47(m,211), 4.5~s,111), 4.6 (m,lH) and 4.8 (m,2H)ppm.
EXA~IP E 26 4-Nitrobenz~l Penicillanate l,l-Di~xi(~e A solution of 4-nitrobenzyl penicillanate in chloroform was cooled to about 15C. and 1 equivalent of 3-chloroperbenzoic acid was added. The reaction mixture was stirred for 20 minutes. Examination for the reaction mixture at this point by nuclear magnetic resonance spectroscopy revealed that it contained 4-nitrobenzyl pen~cillanate l-oxide. A further 1 equivalent of 3-chloroperbenzoic acid was added and the reaction mixture was stirred for 4 hours. At this point a further 1 equivalent of 3-chloroperbenzoic acid was added and the reaction mixture was stirred overnight. The solvent was removed by evaporation, and the residue was partitioned between ethyl acetate and water at pll 8.5. The ethyl acetate layer was separated, washed with water, dried and evaporated to give the crude product. The crude product was purified by chromatography on silica gel, eluting with at 1:4 mixture of ethyl acetate/chloroform.

The NMR spectrum of the procluct (CDC13) showed absorptions at 1.35 ~s, 3}l), 1.58 (s, 3H), 3.45 (m, 2H), 4.42 (s) lH)~ 4.58 ~m, 11l), 5.30 (s, 21-l) and 7.83 ~q, 4ll)ppm.

Penicillanic Acid l,l-Dioxicle To 0.54 g. of 4-nitrobenzyl penicillanate lJl-dioxide in 30 ml.
of methanol and 10 ml. of ethyl acetate was added 0.54 g. of 10% palladium-on-carbon. The mixture was then shaken under an atmosphere of hydrogen at a pressure of about 50 psig. until hydrogen uptake ceased. The reaction mixture was filtered, and the solvent removed by evaporation. The residue was partitioned between ethyl acetate and water at pH 8.5, and the water layer was removed. Fresh ethyl acetate was added and the pH was adjusted to 1.5.
The ethyl acetate layer was removed, washed with watcr and dr:ied, and then it was evaporated in vacuo. '~'his aforded 0.168 g. of the title compound as a crystalline solid.

Penicillanic Acid l,l-~ioxide A stirred solution of 512 mg. of 4-nitrobenzyl penicillanate 1~1-dioxide in a mixture of 5 ml. of acetonitrile and 5 ml. of water was cooled to 0C. and then a solution of 484 mg. of sodium dithionite in 1.4 ml. of l.oN sodium hydroxide was added portionwise over several minutes. The reaction mixture was stirred for an additional 5 minutes and then it was diluted with ; ethyl acetate and water at pH 8.5. The ethyl acetate layer was removed and evaporated in vacuo giving 300 mg. of starting material. Fresh ethyl acetate ; was added to the aqueous phase and the pH was adjusted to 1.5. The ethyl acetate was removed, dried and evaporated ~n vacuo giVillg 50 mg. of the title compound.

~ , ' l=Methyl-l-(acètoxy)ethyl PenicilIanate l~l~Dioxide To 2.33 g. of penicillanic acid l,l-dioxide in 5 ml. of N,~-dimethyl-formamide was added 1.9 ml. o~ ethyldiisopropylamide followed by the dropwise addition of 1.37 g. of l-methyl-l-(acetoxy)ethyl chloride at ca 20C. The mixture was stirred at ambient temperature overnight and then the mixture was diluted with ethyl acetate and with water. The layers were separated and the 0thyl acetate layer was washed with water at pH 9. The ethyl acetate solution was then dried (Na2SO~) and evaporated in vacuo leaving 1.65 g. of crude product as an oil. The oil solidified on standing in the refrigerator, and it was then recrystallized from a mixture of chloroform and ether giving material having a melting point of 90-92C.
The NhlR spectrum of the crude product (CDCl3) showed absorbtions at l.S (s, 31t), 1.62 (s, ~1), 1.85 (s, 3~1), 1.93 (s, 311), 2.07 (s,311), 3.~3 (m, 2~1), 4.3 (s, lH) and 4.57 (m, lH)ppm.

The procedure of xample 29 is repeated, except that the l-methyl-l-(acetoxy)ethyl chloride is replaced by the appropriate l-methyl-l-(alkanolyl-oxy)-ethyl chloride, to produce the following compounds:
l-methyl-l-(propionyloxy)ethyl penicillanate l,l-dioxide, l-methyl-l-(pivaloyloxy)ethyl penicillanate l,l-dioxide and l-methyl-l-(hexanoyloxy)ethyl penicillanic acid l,l-dioxide, respectively.
EXAMP~ 3l Penicillanic Acid l,l-Dioxide ~ ~ = .. . .
To a stirred solution of l.78 g. of penicillanic acid in water, at pH 7.5, was added 1.46 ml. of 40% peracetic acid, followed by an additio~al ~?~t~3 2.9L~ ml. of 40% peracetic acid 30 minu~es later. The reaction mixture was stirred for 3 days at room temperature and then it was diluted with ethyl acetate and water. Solid sodium bisulfite was added to decompose excess peracid, and then the pH was adjusted to 1.5. The ethyl acetate layer was removed, dried (Na2S04) and evaporated in vacuo. The residue was a 3:2 mixture of penicillanic acid l,l-dioxide and penicillanic acid l-oxide.

Pivaloyloxymethyl Penicillanate l,l-Dioxide A stirred solution of 595 mg. of pivaloyloxymethyl penicillanate l-oxide in 5 ml. of ethyl acetate was cooled to ca -15~., and 5 mg. of manganic acetylacetonate was added. To the dark brown mixture thus obtained was added, during several minutes, 0.89 ml. of 40% peracetic acid in small amounts over several minutes. After ~0 m:inutes the cooling bath was removed, and the mixture was stirred at ambient temperature for 3 days. The mixture was diluted with ethyl acetate and water at pH 8.5, and the ethyl acetate layer was removed, dried and evaporated in vacuo. This afforded 178 mg.
of material which was shown by NMR spectroscopy to be a mixture of pivaloyloxy-methyl penicillanate l,l-dioxide and pivaloyloxymethyl penicillanate l-oxide.
The above material was redissolved in ethyl acetate and reoxidized using 0.9 ml. of peracetic acid and 5 mg. of manganic acetylacetonate, as described above, using a reaction time of 16 hours. The reaction mixture was worked up as described above. This afforded 186 mg. of pivaloyloxymethyl penicillanate l,l-dioxide.
PR~PARATION A

6,6-Dibromopenicillanic Acid l~-Oxide The title compound is prepared by oxidation o~ 6,6-dibromopenicillan-ic acid with 1 equivalent of 3-chloroperbenzoic acid in tetrahydrofuran at ~6 0-25VC. f~r ca. 1 hour, according to the procedure of Harrlson et al., Journal of the Chemical ~ (London) Perkin I, 177Z (1976).
_ PREPARATION B
-Beniyl 6,6--Dibromopenicillanate To a solution of 54 g. ~0.165 mole) of 6,6-dibromopenicillanic acid in 350 ml. of N,N-dimethylacetamide was added 22.9 ml. (0.165 mole) of triethyl-amine and the solution was stirred for 40 minutes. Benzyl bromide (19.6 ml., 0.165 mole) was added and the resulting mixture was stirred at room temperature for 48 hours. The precipitated triethylamine hydrobromide was filtered off, and the filtrate was added to 1,500 ml. of ice-water, adjusted to pH 2. The mixture was extracted with ether, and the extracts were washed successively with saturated sodium blcarbonateJ water and brine. The dried (MgS04) ether solution was evaporated in vacuo to give an off-white solid, which was recrys-tallized from isopropanol. lhis aforded 70.0 g. (95% yield) o the title compound m.p. 75-76C'. The IR spectrum (KBr disc) showed absorptions at 1795 and 1740 cm 1. Ihe NMR spectrum ~DC13) showed absorptions at 1.53 (s, 3H), 1.58 ~s, 3H), 4.50 (s, lH), 5.13 (s, 2H), 5.72 (s, lH) and 7.37 (s, 5H)ppm.
PREPARATION C
Benzyl 6,6-Dibromopenicillanate l~-Oxide To a stirred solution of 13.4 g. (0.03 mole) of benzyl 6,6-dibromo-penicillanate in 200 ml. of dichloromethane was added a solution of 6.12 g.
(0.03 mole) of 3-chloroperbenzoic acid in 100 ml. of dichloromethane, at ca.
0G. Stirring was continued for 1.5 hours at ca. 0C. and then the reaction mixture was filtered. The filtrate was washed successively with 5% sodium bicarbonate and water, and then it was dried (Na2S04). Removal of the solvent by evaporation in vacuo gave 12.5 g. of the title product as an oi. The oil was induced to solidify by trituration under ether. Filtration then afforded 10.5 g. of benæyl 6,6-dibromopenicillanate l~-oxide as a solid. The IR spec-trum (CHC13) showed absorptions at 1800 and 1750 cm 1. The NMR spectrum of the product ICDC13) showed absorptions at 1~3 (s, 3H), 1.~ ~s, 3H), 4.5 (s,lH) 5.18 (s, 2H) J 5.2 (s, lH) and 7.3 ~s, 5H)ppm.
PREPARATION D
_-Nitrobenzyl Penicillanate Reaction of the triethylamine salt of penicillanic acid with 4-nitro-benzyl bromide, according to the procedure of Preparation B, affords 4-nitro-benzyl penicillanate.
PREPARATION E
2,2,2-Trichloroethyl Penicillanate To 403 mg. of penicillanic acid in 10 ml. of dichloromethane was added 25 mg. of di:isopropylcarbodiimide followed by 0.19 ml. of 2,2,2-trichloro-ethanol, rhe mixture was stirred overnlght and then the solvent was removed by evapor~tion ln vacuo. Ihe crude product was purified by column chroma-tography using silica gel as the adsorbent and chloroform as the eluant.
PREPARATION F
3-Phthalidyl Penicillanate To a solution of 506 mg. of penicillanic acid in 2 ml. of N,N-dimethylformamide was added 0.476 ml. of diisopropylethylamine followed by536 mg. of 3-phthalidyl bromide. The mixture was stirred overnight and then it was diluted with ethyl acetate and water. The p~l was adjusted to 3.0 and the layers were separated. The organic layer was washed with water, and then with water at pH 8.0, and then it was dried using anhydrous sodium sulfate.
The dried ethyl acetate solution was evaporated in vacuo giving 713 mg. of the title ester as an oil. The NMR spectrum ICDC13) showed absorptions at 1.62 ~m,6H), 3.3 (m,2H), 4.52 (s,lH), 5.23 (m,lH) and 7.63 (m,5H).

~L~?~ 3 PREPARATION G
Pivaloyloxymethyl Penicillanate To 3.588 g. of 6.6-dibromopenicillanic acid in 10 ml. of N,N-dimetilylformamide was added 1.8 ml. of diisopropyLethylamine, follwed by 1.40 ml. of chloromethyl pivalate. The mixture was stirred overnight and then it was diluted with ethyl acetate and water. The organic layer was removed and washed successively with water at pH 3.0 and water at pH 8Ø The ethyl acetate solution was dried (Na2S04) and then evaporated in vacuo to give pivaloyloxymethyl 6,6-dibromopenicillanate as an amber oil (3.1 g.) which slowly crystallized.
The above ester was dissolved in lOO ml. of methanol, and then 3.1 g. of 10% palladium-on-carbon and 1.31 g. of potassium bicarbonate in 20 ml. of water were added. The mixture was shaken under hydrogen at atmospheric pressure until hydrogen uptake ceased. The reaction mixture was filtered and the methanol was removed by evaporation m vacuo. The residue was partitioned between water and ethyl acetate at pH 8, and then the organic layer was removed. The latter was dried ~Na2S04) and evaporated in vacuo to give 1.25 g. of the title compound. The NMR spectrum ~GD~13) showed absorptions at 1.23 ~s,9H), 1.5 ~s,3H), 1.67 ~s,3H), 3.28 ~m,2H), 4.45 ~s,lH), 5.25 ~m,lH) and 5.78 ~m,2H)ppm.
PREPARATION H
4-Nitrobenzyl Penicillanate To a stirred solution of 2.14 g. of penicillanic acid and 2.01 ml.
of ethyldiisopropylamine in 10 ml. of N,N-dimethylformamide was added dropwise 2.36 g. of 4-nitrobenzyl bromide, at ca. 20C. The mixture was stirred at ambient temperature overnight, and then it was diluted with ethyl acetate and water. The layers were separated and the ethyl acetate layer was washed 5t773 with water at pl-l 2.5, followed by water at pll 8.5. T1le ethyl acetate solution was then dried (Na2S04) and evaporated in vacuo leaving 3.36 g. of the title compound.
The NMR spectrum of the product ~in CDCl3) showed absorptions at 1.45 (s, 3H), 1.68 (s, 3H), 3.32 (m, 211), 4.50 (s, lH), 5.23 (m, lH), 5.25 (s, 2H) and 7.85 (q, 4H) ppm.

`

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pharmaceutical composition which comprises a compound of the formula or a pharmaceutically-acceptable base salt thereof, wherein R1 is selected from the group consisting of hydrogen and ester-forming residues readily hydrolyzable in vivo, together with a .beta.-lactam antibiotic.

2. A pharmaceutical composition according to claim 1, wherein R1 is hydrogen.

3. A pharmaceutical composition according to claim 1, wherein R1 is pivaloyloxymethyl.

4. A pharmaceutical composition according to claim 1, 2 or 3,wherein said .beta.-lactam antibiotic is 6-(2-phenylacetamido)penicillanic acid, 6-(2-phenoxyacetamido)penicillanic acid, 6-(D-2-amino-2-phenylacetamido)-penicillanic acid, 6-(D-2-amino-2-[4-hydroxyphenyl]acetamido) penicillanic acid or 1-(ethoxycarbonyloxy)ethyl 6-(D-2-amino-2-phenylacetamido)-penicillanate, or a pharmaceutically-acceptable salt thereof.

5. A pharmaceutical composition according to claim 1, 2 or 3, wherein said .beta.-lactam antibiotic is 6-(D-2-amino-2-phenylacetamido)- penicillanic acid or a pharmaceutically-acceptable salt thereof.