3-Substituted-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid
BACKGROUND OF THE INVENTION 
     This is a continuation-in-part of U.S. Ser. No. 119,065 filed Feb. 6, 1980 now abandoned which is a continuation of U.S. Ser. No. 843,373 filed Oct. 19, 1977, now abandoned. 
    
    
     This invention relates to 3-substituted-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acids (I) and to their pharmaceutically acceptable salt, ester and amide derivatives, which compounds are useful as antibiotics: ##STR2## wherein R is, inter alia, acyl, alkyl, and aralkyl. R is additionally defined below. 
     This invention also relates to processes for the preparation of such compounds (I); pharmaceutical compositions comprising such compounds; and to methods of treatment comprising administering such compounds and compositions when an antibiotic effect is indicated. 
     There is a continuing need for new antibiotics. For unfortunately there is no static effectiveness of any given antibiotic because continued wide scale usage selectively gives rise to resistant strains of pathogens. In addition, the known antibiotics suffer from the disadvantage of being effective only against certain types of microorganisms. Accordingly the search for new antibiotics continues. 
     Thus, it is an object of the present invention to provide a novel class of antibiotics which are useful in animal and human therapy and in inanimate systems. These antibiotics are active against a broad range of pathogens which representatively include both gram positive bacteria such as S. auerus, Strep. pyogenes, and B. subtilis, and gram negative bacteria such as E. coli, Proteus morganii, Pseudomonas, Serratia and Klebsiella. Further objects of this invention are to provide chemical processes for the preparation of such antibiotics and their non-toxic pharmaceutically acceptable salts; pharmaceutical compositions comprising such antibiotics; and to provide methods of treatment comprising administering such antibiotics and compositions when an antibiotic effect is indicated. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the generic description of the compounds of the present invention (I): ##STR3## R is selected from the group consisting of substituted and unsubstituted: alkyl, having 1-6 carbon atoms, cycloalkyl and cycloalkylalkyl wherein the ring moiety comprises 3-6 carbon atoms and the alkyl moiety comprises 1-4 carbon atoms, aralkyl having from 7-16 carbon atoms, and acyl; wherein the substituent or substituents on the radical R are selected from: amino; mono-, di- and trialkylamino wherein the alkyl has 1-6 carbon atoms; alkoxyl having 1-6 carbon atoms; chloro, bromo; amidino; guanidino; and carboxyl. Generically, the term &#34;acyl&#34; as it relates to the definition of R is inclusive of the alkanoyls including derivatives and analogues thereof such as thio analogues wherein the carbonyl oxygen is replaced by sulphur; as well as sulphur and phosphorous acyl analogues such as substituted sulfonyl, sulfinyl-, and sulfenyl-radicals, and substituted P (III and V) radicals such as substituted phosphorous-, phosphoric-, phosphonous- and phosphonic-radicals, respectively. Such acyl radicals of the present invention are further defined below. 
     Representative of such acyl radicals, R, are: ##STR4## wherein X is O or S and R&#39; is: R&#34;, OR&#34;, NR 2  &#34;, or SR&#34;, wherein R&#34; is substituted or unsubstituted alkyl having 1-6 carbon atoms, aryl such as phenyl, aralkyl such as benzyl or phenethyl, or heterocycle wherein the hetero atom or atoms are selected from oxygen, sulfur and nitrogen. More specifically, suitable acyl radicals, R, are: ##STR5## R&#34; is defined above). The radical R may also be ##STR6## wherein R&#39; is as defined above; ##STR7## is as defined above; and ##STR8## wherein R&#39; is --OR&#34; or --NR&#34; 2 . 
     Relative to the definition of the compounds of the present invention (I) the most preferred values for the radical R are those selected from the group consisting of loweralkyl having from 1-6 carbon atoms such as methyl, ethyl, propyl and the like, aralkyl such as benzyl, diphenylmethyl and the like, substituted alkyl such as 2-aminoethyl, 3-aminopropyl, 2-formamidoylaminoethyl and the like and substituted aralkyl such as p-carboxybenzyl, p-aminobenzyl, p-hydroxybenzyl, pyridylmethyl, and the like; and acyl, ##STR9## wherein R&#39; is selected from the above-defined unsubstituted or substituted: alkyl, aralkyl, aryl; for example: ##STR10## wherein R&#39; is selected from the above-defined unsubstituted or substituted: alkyl or aryl, for example: ##STR11## 
     The preparation of the compounds (I) of the present invention may conveniently be summarized by the following reaction diagram: ##STR12## 
     In words relative to the above reaction diagram starting materials 4 and 8 and the reaction sequence 1→→8 are disclosed in co-pending, commonly assigned U.S. Patent Application Ser. No. 792,071 filed Apr. 28, 1977; this application, as it relates to these starting materials, is incorporated herein by reference. This application is now abandoned, and was refiled and issued as U.S. Pat. No. 4,234,596. Basically, however, the 4-(2-substituted-vinyl)azetidine-2-one, 4, starting material is prepared by reacting an R 1  -oxybutadiene, 1, with chlorosulfonylisocyanate 2. The reaction is conducted without solvent or may be run in solvent such as diethyl ether, ethyl acetate, chloroform, methylene chloride, or the like, at a temperature of from -78° C. to 25° C. for from a few minutes to 1 hour to provide 3. The radical R 1  is an easily removable acyl blocking group such as an alkanoyl or aralkanoyl which bears no functional group or groups which might interfere with the desired course of reaction (1+2→3→4). Intermediate species 3 is converted to the sulfinamide by reduction which is then hydrolyzed to 4 at pH 6-8. Typically the reaction solution comprising 3 is contacted (5-30 minutes) with an aqueous solution (at 0°-25° C.) of a reducing agent such as sodium sulfite, thiophenol, or the like, at pH 6-8 to provide 4. 
     The reaction 4→5 is a reduction, and is preferably achieved by hydrogenation in a solvent such as ethyl acetate, ether, dioxane, tetrahydrofuran (THF), ethanol or the like at 0° to 25° C. for from 5 minutes to 2 hours under 1 to 10 atmospheres of hydrogen in the presence of a hydrogenation catalyst such as a platinum metal or oxide thereof such as 10% Pd/C or the like. 
     The reaction 5→7 establishes, if desired, the N-protecting group R 2 , which preferably is a cyclic ether such as 2-tetrahydropyranyl or a triorganosilyl radical, such as trimethylsilyl or t-butyl-dimethylsilyl. Alternatively, R 2  may be hydrogen. Typically, when the protecting group R 2  is a triroganosilyl radical, such as t-butyldimethylsilyl, species 5 in a solvent such as DMF, dioxane, THF, Et 2  O or the like in the presence of a base such as triethylamine, imidazole, pyridine, hexamethyldisilazane or the like is contacted with the desired silylating agent such as t-butyldimethylsilylchloride, trimethylsilylchloride, isopropyldimethylsilylchloride, or the like at a temperature of from -10° to 40° C. for from 10 mins to 8 hours. Suitable reagents for the establishment of R 2  when R 2  is a cyclic ether such as 2-tetrahydropyranyl, 2-methoxy-2-tetrahydropyranyl, 4-methoxy-4-tetrahydropyranyl or the like are: 2,3-dihydro-4H-pyran, 6-methoxy-2,3-dihydro-4H-pyran, 4-methoxy-5,6-dihydro-2H-pyran and the like. The establishment of such cyclic ether protecting groups is typically conducted in a solvent such as Et 2  O, EtOAc, dioxane, DMF, and the like in the presence of an acid, such as HCl, p-toluenesulfonic acid, or phosphoryl chloride at a temperature of from 0° to 25° C. for from 10 mins to 3 hrs. 
     The deblocking reaction 6Z→7 is preferably accomplished by alcoholysis wherein the solvent is a loweralkanol such as methanol, ethanol or the like in the presence of the corresponding alkali metal alkoxide, such as sodium methoxide. Typically, the reaction is conducted for from 5 minutes to 3 hours at a temperature of from -10° to 25° C. 
     The aldehyde intermediate 8 is prepared by treating 7 with an oxidizing agent such as CrO 3 .2(pyridine) in CH 2  Cl 2 , 1:1 mixture of dimethylsulfoxide (DMSO) and acetic anhydride, pyridinium chlorochromate in CH 2  Cl 2 , dicyclohexylcarbodiimide in DMSO, methylene chloride or the like at a temperature of from 0°-25° C. for from 5 minutes to 8 hours. 
     The alkylation of the aldehyde to provide species 9 (8→9) is accomplished by treating 8 in a solvent such as Et 2  O (diethyl ether), THF (tetraydrofuran), HMPA (hexamethyl phosphoramide), DMF (dimethylformamide), or the like at a temperature of from -78° to 0° for from 1 min to 1 hour in the presence of a base such as lithium diisopropylamide, KH, or the like with an ester of acetic acid (CH 3  CO 2  R 3  ; wherein R 3  is a readily removably carboxyl protecting group or a pharmaceutically acceptable ester moiety; suitable values for R 3  are defined below). 
     Intermediate ketone species 10 is obtained by oxidation of 9 following the previously described oxidation procedure 7→8. The N-protecting group R 2  is easily removed by mild acid hydrolysis such as acetic acid in water at a temperature of from 25° to 100° C. for from 1 to 20 hours to provide species 11 (10→11). 
     The diazo species 12 is prepared from 11 by treating 11 in a solvent such as CH 3  CN, CH 2  Cl 2  THF and the like with an azide such as p-carboxy benzenesulfonylazide, toluene sulfonylazide, methanesulfonylazide and the like in the presence of base such as triethylamine, pyridine, (C 2  H 5 ) 2  NH and the like for from 1 to 50 hours at 0° to 25° C. 
     Cyclization of the diazo compound to provide 13 (12→13) is preferably accomplished by irradiating through a pyrex filter (λ greater than 300 nm) in a solvent such as benzene, CCl 4 , Et 2  O, or the like at a temperature of from 0° to 25° C. for from 0.5 to 2 hours. Alternatively, cyclization of the diazo compound is accomplished by heating in a solvent such as φH, φMe, THF or the like at a temperature of from 50° to 110° for 1-5 hrs in the presence of a catalyst such as bis(acetylacetonato)Cu (II) [Cu(acac) 2  ], CuSO 4 , Cu powder, Rh(OAc) 2 , or Pd(OAc) 2 . The 3-keto species 13 serves as a common intermediate for the preparation of ester (R is acyl) and ether (R is, inter alia, alkyl) embodiments of the present invention. Species 13 may also be prepared according to the disclosure found in European Patent Application Number 79101307.1 (filed May  1, 1979), publication 007973/A1, which is incorporated herein by reference, when the procedure disclosed omits the alkylation schemes which establish the hydroxyethyl moiety, step 7→8. 
     Embodiments of the present invention (I) wherein R is acyl are prepared by reacting species 13 in a solvent such as benzene, CH 2  Cl 2 , THF, DMF, and the like in the presence of a base such as triethylamine (Et 3  N), pyridine, 4-dimethylaminopyridine, propylene oxide and the like at a temperature of from 0°-25° with a reagent calculated to introduce the acyl radical of choice. Generically, such acylating reagents may be selected from the following list of reagents: acid chloride, acid anhydride, ketene, activated acid esters and the like. Representative examples of such reagents are: 
     ketene, 
     acetic anhydride, 
     acetyl chloride, 
     azido acetyl chloride, 
     phenyl acetyl chloride, 
     benzoic anhydride, 
     benzoyl chloride, 
     propionic anhydride, 
     diphenyl ketene, 
     chloroacetyl chloride, 
     p-nitrophenyl chloroacetate, 
     N-benzyloxycarbonyl glycyl chloride, 
     methane sulfonic anhydride, 
     p-toluenesulfonic anhydride, 
     methanesulfonyl chloride, 
     p-toluenesulfonyl chloride. 
     Embodiments of the present invention (I) wherein R is other than acyl which generically may be classified as ethers and conveniently prepared from the 3-keto intermediate species 13 by treating 13 with a diazo reagent calculated to provide the radical R in a solvent such as Et 2  O, CH 2  Cl 2 , CH 3  OH, benzene, CH 3  CN and the like at a temperature of from 0° to 80° C. for from 15 mins to 2 hours. Representative examples of such diazo reagents are: 
     diazomethane, 
     1-diazobutane, 
     3-propyl-1-p-tolyltriazene, 
     3-ethyl-1-p-tolyltriazene, 
     3-benzyl-1-p-tolyltriazene, 
     phenyl diazomethane, 
     diphenyldiazomethane, 
     In addition, the ether embodiments may be obtained by alkylating the keto ester intermediate 13 with a reagent RX in the presence of base. Suitable reagents RX may be CH 3  SO 3  F, (CH 3 ) 2  SO 4 , CF 3  SO 3  CH 2  CH 2  N 3 , or TsOCH 2  CH 2  N 3  (X is a leaving group, and Ts=tosyl); suitable solvents for the reaction include acetone, hexamethylphosphoramide (HMPA), DMF, THF, dioxane or the like in the presence of base such as potassium carbonate, potassium tertiary butoxide, sodium hydride, or the like at a temperature of from -20° to 40° C. for from 0.5 to 3 hours. 
     Species 14 may be deblocked if desired to provide I by mild aqueous hydrolysis or hydrogenolysis. 
     The compounds of the present invention may generically be represented by the following structural formula: ##STR13## wherein X&#39; is oxygen, sulfur or NR&#39; (R&#39; is hydrogen or loweralkyl having from 1 to 6 carbon atoms); and R 3&#39;  is representatively selected to provide the pharmaceutically acceptable salt, ester, anhydride (R 3&#39;  is acyl) and amide moieties known in the bicyclic β-lactam antibiotic art. 
     Identification of the Radical --COX&#39;R 3&#39;   
     In the generic representation of the compounds of the present invention (Ia, above), the radical represented by --COX&#39;R 3&#39;  is, inter alia, --COOH (X&#39; is oxygen and R 3&#39;  is hydrogen) and all radicals known to be effective as pharmaceutically acceptable ester, anhydride (R 3&#39;  is acyl) and amide radicals in the bicyclic β-lactam antibiotic art, such as the cephalosporins and penicillins and the nuclear analogues thereof. 
     Suitable radicals (R 3&#39; ) include conventional protecting or carboxyl blocking groups. The term &#34;blocking group&#34; as utilized herein is employed in the same manner and in accordance with the teaching of U.S. Pat. No. 3,697,515 which is incorporated herein by reference. Suitable blocking esters thus include those selected from the following list which is representative and not intended to be an exhaustive list of possible ester groups, wherein X&#39;=O and R 3&#39;  is given: 
     (i) R 3&#39;  =CR a  R b  R c  wherein at least one of R a ,R b  and R c  is an electron-donor, e.g., p-methoxyphenyl, 2,4,6-trimethylphenyl, 9-anthryl, methoxy, CH 2  SCH 3 , tetrahydrofur-2-yl, tetrahydropyran-2-yl or fur-2-yl. The remaining R a , R b  and R c  groups may be hydrogen or organic substituting groups. Suitable ester groups of this type include p-methoxybenzyloxycarbonyl and 2,4,6-trimethylbenzyloxycarbonyl. 
     (ii) R 3&#39;  =CR a  R b  R c  wherein at least one of R a , R b  and R c  is an electron-attracting group, e.g., benzoyl, p-nitrophenyl, 4-pyridyl, trichloromethyl, tribromomethyl, iodomethyl, cyanomethyl, ethoxycarbonylmethyl, arylsulphonylmethyl, 2-dimethylsulphoniummethyl, o-nitrophenyl or cyano. Suitable esters of this type include benzoylmethoxycarbonyl, p-nitrobenzyloxycarbonyl, 4-pyridylmethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl and 2,2,2-tribromoethoxycarbonyl. 
     (iii) R 3&#39;  =CR a  R b  R c  wherein at least two of R a , R b  and R c  are hydrocarbon such as alkyl, e.g., methyl or ethyl, or aryl, e.g, phenyl and the remaining R a , R b  and R c  group, if there is one, is hydrogen. Suitable esters of this type include t-butyloxycarbonyl, t-amyloxycarbonyl, diphenylmethoxycarbonyl and triphenylmethoxycarbonyl. 
     (iv) R 3&#39;  =R d , wherein R d  is adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl or tetrahydropyran-2-yl. 
     Silyl esters, under this category of blocking groups, may conveniently be prepared from a halosilane or a silazane of the formula: 
     R 4   3  SiX&#39;; R 4   2  SiX&#39; 2  ; R 4   3  Si NR 4   2  ; R 4   3  Si NH COR 4  ; R 4   3  Si NH CO NH SiR 4   3  ; R 4  NH CO NH SiR 4   3  ; or R 4  C(OSiR 4   3 ); HN(SiR 4   3 ) 2  wherein X&#39; is a halogen such as chloro or bromo and the various groups R 4 , which can be the same or different, represent hydrogen atoms or alkyl, e.g., methyl, ethyl, n-propyl, iso-propyl; aryl, e.g., phenyl; or aralkyl, e.g., benzyl groups. 
     More generally stated, pharmaceutically acceptable carboxyl derivatives of the present invention are those derived by reacting I with alcohols, phenols, mercaptans, thiophenols, acylating reagents and the like. For example, esters and amides of interest are the above-listed starting materials and final products having the following group at the 2-position the nucleus: --COX&#39;R 3&#39;  wherein X&#39; is oxygen, sulfur, or NR&#39; (R&#39; is H or R 3&#39; ), and R 3&#39;  is alkyl having 1-10 carbon atoms, straight or branched, such as methyl, ethyl, t-butyl, pentyl, decyl and the like; carbonylmethyl, including phenacyl, p-bromophenacyl, p-t-butylphenacyl, acetoxyacetylmethyl, pivaloxyacetylmethyl, carboxymethyl, and its alkyl and aryl esters, α-carboxy-α-isopropyl; aminoalkyl including 2-methylaminoethyl, 2-diethylaminoethyl, 2-acetamidoethyl, phthalimidomethyl, succinimidomethyl; alkoxyalkyl wherein the alkoxy portion has 1-10 and preferably 1-6 carbon atoms; but can be branched, straight or cyclic, and the alkyl portion has 1-6 carbon atoms, such as methoxymethyl, ethoxymethyl, isopropoxymethyl, decyloxymethyl, ethoxypropyl, decyloxypentyl, cyclohexyloxymethyl and the like; alkanoyloxyalkyl wherein the alkanoyloxy portion is straight or branched and has 1-6 carbon atoms and the alkyl portion has 16 carbon atoms, such as acetoxymethyl, pivaloyloxymethyl, acetoxyethyl, propionyloxyethyl, acetoxypropyl, and the like; haloalkyl wherein halo is chloro, bromo, fluoro, or iodo, and the alkyl portion is straight or branched having 1-6 carbon atoms, e.e., 2,2,2-trichloroethyl, trifluoroethyl, 2-bromopropyl, diiodomethyl, 2-chloroethyl, 2-bromoethyl, and the like; alkenyl having 1-10 carbon atoms, either straight or branched, e.g., allyl, 2-propenyl, 3-butenyl, 4-butenyl, 4-pentenyl, 2-butenyl, 3-pentenyl, 3-methyl-3-butenyl, metallyl, 1,4-cyclohexadien-1-yl-methyl, and the like alkynyl having 1-10 carbon atoms, either straight or branched e.g., 3-pentenyl, propargyl, ethynyl, 3-butyn-1-yl, and the like; alkanoyl, either straight or branched, having 1-10 carbon atoms, such as pivaloyl, acetyl, propionyl, and the like; aralkyl or heteroaralkyl wherein alkyl has 1-3 carbon atoms, and hetero means 1-4 hetero atoms being selected from the group consisting of O, S, or N, such as benzyl, benzhydryl, and substituted benzyl, benzhydryl, or e.g., benzyl or benzhydryl substituted with 1-3 substituents such as benzyl, phenoxy, halo, loweralkyl, loweralkanoyloxy of 1-5 carbon atoms, lower alkoxy, hydroxy, nitro, blocked carboxy, or combinations thereof, e.g., p-chlorobenzyl, o-nitrobenzyl, 3,5-dinitrobenzyl, p-methoxybenzyl, m-benzoylbenzyl, p-t-butylbenzyl, m-phenoxybenzyl, p-benzoylbenzyl, p-nitrobenzyl, 3,5-dichloro-4-hydroxybenzyl, p-methoxycarbonylbenzyl, p-methoxybenzhydryl, p-carboxybenzyl, the latter being either the free acid, ester or the sodium salt, 2,4,6-trimethylbenzyl, p-pivaloyloxybenzyl, p-t-butoxycarbonyl benzyl, p-methylbenzyl, p-benzoyloxybenzyl, p-acetoxybenzyl, p-2-ethylhexanoylbenzyl, p-ethoxycarbonylbenzyl, p-benzoylthiobenzyl, p-benzamidobenzyl, o-pivaloyloxybenzyl, m-pivaloyloxybenzyl, p-isopropoxybenzyl, p-t-butoxybenzyl, as well as the cyclic analogues thereof, 2,2-dimethyl-5-coumaranmethyl, 5-indanylmethyl, p-trimethylsilylbenzyl, 3,5-bis-t-butoxy-4-hydroxybenzyl; 2-thienylmethyl, 2-furylmethyl, 3-t-butyl-5-isothiazolmethyl, 6-pivaloyloxy-3-pyridazinylethyl, 5-phenylthio-1-tetrazolylmethyl, or the like (the use of the terms lower alkyl or lower alkoxy in this context means 1-4 carbon atoms chain); or phthalidyl; or phenylethyl, 2-(p-methylphenyl)ethyl, and the arylthioalkyl analogues, aryloxyalkyl wherein aryl is preferably a phenyl ring having 0-3 substituents preferably 0 or 1 substituents in the ortho or para positions and alkyl is 1-6 carbon atoms, e.g., (4-methoxy)phenoxymethyl, phenoxymethyl, (4-chloro)phenoxymethyl, (4-nitro)phenoxymethyl, (4-benzyloxy)phenoxymethyl, (4-methyl)phenoxymethyl, (4-benzyloxy)phenoxymethyl, (4-methyl)phenoxymethyl, (2-methoxy)phenoxymethyl, (1-phenoxy)ethyl, (4-amino)phenoxymethyl, (4-methoxy)phenylthiomethyl, (4-chloro)phenylthiomethyl, phenylthioethyl; aryl wherein aryl is phenyl, 5-indanyl, or substituted phenyl having 0-3 substituents, preferably 0 or 1 substituent in the ortho or para position, e.g., (4-methyl)phenyl, (4-hydroxy)phenyl, (4-t-butyl)phenyl, p-nitrophenyl, 3,5-dinitrophenyl, or p-carboxyphenyl, the latter having either the free acid or the sodium salt form; aralkenyl wherein aryl is phenyl and alkenyl has 1-6 carbon atoms, such as 3-phenyl-2-propenyl; aralkoxyalkyl wherein aralkoxy is benzyloxy, and alkyl has 1-3 carbon atoms, such as benzyloxymethyl, (4-nitro)benzyloxymethyl, (4-chloro)benzyloxymethyl; alkylthioalkyl wherein the alkylthio portion has 1-10 and preferably 1-6 carbon atoms, but can be branched, straight or cyclic, and the alkyl portion has 1-6 carbon atoms, such as methylthioethyl, ethylthioethyl, cyclohexylthiomethyl, decylthiobutyl, methylthiopropyl, isopropylthioethyl, methylthiobutyl and the like. 
     In addition to the esters (and thio esters) listed above, amides are also embraced by the present invention, i.e., wherein X&#39; is the ##STR14## Representative of such amides are those wherein R&#39; is selected from the group consisting of hydrogen, methyl, ethyl, phenyl, p-methoxyphenyl, benzyl, carboxymethyl, methylthioethyl, and heteroaryl; also embraced by --COX&#39;R 3&#39;  are anhydrides wherein R 3&#39;  is acyl, for example, benzyloxycarbonyl, ethoxycarbonyl, benzoyl, and pivaloyl. 
     The most preferred --COX&#39;R 3&#39;  radicals of the present invention are those wherein (relative to Structure Ia above X&#39; is oxygen, sulphur or NR&#39; (R&#39; is selected from the group consisting of hydrogen and lower alkyl); and R 3&#39;  is selected from the group consisting of: loweralkyl, lower alkenyl, such as methallyl, 3-methylbutenyl, 3-butenyl, and the like; methylthioethyl, benzyl and substituted benzyl such as p-t-butylbenzyl, m-phenoxybenzyl, p-pivaloyloxybenzyl, p-nitrobenzyl and the like; pivaloyloxymethyl, 3-phthalidyl and acetoxymethyl, propionyloxymethyl, acetylthiomethyl, pivaloylthiomethyl, allyl, 4-butenyl, 2-butenyl, 3-methyl-2-butenyl, phenacyl, acetoxyacetylmethyl, methoxymethyl, p-acetoxybenzyl, p-pivaloyloxybenzyl, p-isopropoxybenzyl, 5-indanylmethyl, 5-indanyl, benzyloxymethyl, ethylthioethyl, methylthiopropyl, methoxycarbonyloxymethyl, ethoxycarbonyloxymethyl, dimethylaminoacetoxymethyl, crotonolacton-3-yl, and acetamidomethyl. 
     The preferred carboxylic acid salts of I are alkali and alkaline metal salts such as sodium, potassium, and calcium salts; amine salts such as benzhydrylamine, N-benzyl-2-phenethylamine, N,N&#39;-dibenzylethylenediamine, and procaine salts. The salts of this invention are pharmacologically acceptable, non-toxic derivatives which can be used as the active ingredient in suitable unit dosage pharmaceutical forms. Also, they may be combined with other drugs to provide compositions having a broad spectrum of activity. 
     The novel compounds are valuable antibiotics active against various gram-positive and gram-negative bacteria and, accordingly, find utility in human and veterinary medicine. The compounds of this invention can therefore be used as antibacterial drugs for treating infections caused by gram-positive or gram-negative bacteria, for example, against Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Serratia, Salmonella typhosa, Pseudomonas and Bacterium proteus. The antibacterials of the invention may further be utilized as additives to animal feeding stuffs, for preserving foodstuffs and as disinfectants. For example, they may be employed in aqueous compositions in concentrations ranging from 0.1 to 100 parts of antibiotic per million parts of solution in order to destroy and inhibit the growth of harmful bacteria on medical and dental equipment and as bactericides in industrial applications, for example, in waterbased paints and in the white water of paper mills to inhibit the growth of harmful bacteria. 
     The products of this invention may be used alone or in combination as an active ingredient in any one of a variety of pharmaceutical preparations. These antibiotics and their corresponding salts may be employed in capsule form or as tablets, powders or liquid solutions or as suspensions or elixirs. They may be administered orally, intravenously or intramuscularly. 
     The compositions are preferably presented in a form suitable for absorption by the gastro-intestinal tract. Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example, syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrrolidone; fillers for example, lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; lubricants, for example, magnesium stearate, talc, polyethylene glycol, silica; disintegrants, for example, potato starch or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in the art. Oral liquid preparations may be in the form of aqueous or oily suspension, solution, emulsions, syrups, elixirs, etc. or may be presented as a dry product, for reconstitution with water or other suitable vehicles before use. Such liquid preparations may contain conventional additives such as suspending agents, for example, sorbitol syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxyethylcellulose, carboxymethyl cellulose, aluminum stearate gel or hydrogenated edible oils, for example almond oil, fractionated coconut oil, oily esters, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoates or sorbic acid. Suppositories will contain conventional suppository bases, e.g. cocoa butter or other glyceride. 
     Compositions for injection may be presented in unit dose form in ampules, or in multidose containers with an added preservative. The compositions may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient may be in powder form for reconstitution with a suitable vehicle, e.g. sterile, pyrogen-free water, before use. 
     The compositions may also be prepared in suitable forms for absorption through the mucous membranes of the nose and throat or bronchial tissues and may conveniently take the form of powder or liquid sprays or inhalants, lozenges, throat paints, etc. For medication of the eyes or ears, the preparations may be presented as individual capsules, in liquid or semi-solid form, or may be used as drops etc. Topical applications may be formulated in hydrophobic or hydrophilic bases as ointments, creams, lotions, paints, powders, etc. 
     Also, in addition to a carrier, the instant compositions may include other ingredients such as stabilizers, binders, antioxidants, preservatives lubricators, suspending agents, viscosity agents or flavoring agents and the like. In addition, there may also be included in the composition other active ingredients to provide a broader spectrum of antibiotic activity. 
     For verterinary medicine the composition may, for example, be formulated as an intramammary preparation in either long or quick-release bases. 
     The dosage to be administered depends to a large extent upon the condition of the subject being treated and the weight of the host, the route and frequency of administration, the parenteral route being preferred for generalized infections and the oral route for intestinal infections. In general, a daily oral dosage consists of from about 2 to about 600 mg. of active ingredient per kg. of body weight of the subject in one or more applications per day. A preferred daily dosage for adult humans lies in the range of from about 15 to 150 mg. of active ingredient per kg. of body weight. 
     The instant compositions may be administered in several unit dosage forms as, for example, in solid or liquid orally ingestible dosage form. The compositions per unit dosage, whether liquid or solid may contain from 0.1% to 99% of active material, the preferred range being from about 10-60%. The composition will generally contain from about 15 mg. to about 1500 mg. of the active ingredient; however, in general, it is preferable to employ a dosage amount in the range of from about 100 mg. to 1000 mg. In parenteral administration the unit dosage is usually the pure compound in a slightly acidified sterile water solution or in the form of a soluble powder intended for solution. 
     The following Examples, illustrate but do not limit the product, process, compositional or method of treatment aspects of the present invention. 
    
    
     EXAMPLE 1 
     Preparation of 4-(2-Acetoxyethyl)-azetidin-2-one ##STR15## 
     A mixture of 4-(2-acetoxyvinyl)-azetidin-2-one (3.00 g), 10% Pd/C (0.15 g) and ethylacetate(EtOAc) (120 ml) is hydrogenated in a 500 ml glass bomb on a Parr shaker at an initial pressure of 39 psi. After shaking 10 mins (final pressure of 20 psi), the mixture is filtered through a pad of MgSO 4  to remove the catalyst. The filtrate is concentrated in vacuo and the residue stripped with anhydrous benzene to provide 4-(2-acetoxyethyl)-azetidin-2-one (3.098 g) as a clear oil: ir(neat) 3.01, 5.66, 5.75, 7.28, 8.05, and 9.61 cm -1  ; nmr(CDCl 3 ) δ 1.95 (m, 2), 2.07 (s,3), 2.60 (m, 1), 3.12 (m, 1), 3.70 (m, 1), 4.15 (m, 2), and 6.77 (br s, 1). 
     EXAMPLE 2 
     Preparation of N-(t-Butyldimethylsilyl)-4-(2-acetoxyethyl)-azetidin-2-one ##STR16## 
     Triethylamine (Et 3  N) (2.96 ml, 21.2 mmol) and t-butyldimethylsilyl chloride (3.059 g, 20.3 mmol) are added to an ice-cold stirring solution of 4-(2-acetoxyethyl)-azetidin-2-one (3.098 g, 19.3 mmol) in anhydrous dimethylformamide (DMF) (20 ml). A white precipitate appears immediately. The cooling bath is removed and the mixture is stirred at 25° C. (room temperature) for 5 mins. The mixture is diluted with benzene (200 ml), washed with H 2  O (5×80 ml) and brine, dired with MgSO 4 , filtered, and evaporated under reduced presure to afford N-(t-butyldimethylsilyl)-4-(2-acetoxyethyl)-azetidin-2-one (5.078 g) as an off white solid: ir(neat) 5.75, 8.08, 8.41, 11.92, and 12.18 cm -1  ; nmr (CDCl 3 ) δ 0.25 (s, 6), 0.98 (s, 9), 1.97 (m, 2), 2.05 (s, 3), 2.67 (dd, 1), 3.20 (dd, 1) 3.62 (m, 1), and 4.12 (t,2); mass spectrum m/e 214 (M +  -57) and 172. 
     EXAMPLE 3 
     Preparation of N-(t-Butyldimethylsilyl)-4-(2-hydroxyethyl)-azetidin-2-one ##STR17## 
     A solution of N-(t-butyldimethylsilyl)-4-(2-acetoxyethyl)-azetidin-2-one (41.7 g, 0.154 mol) in anhydrous methanol (415 ml) is stirred under a N 2  atmosphere with ice-bath cooling. A solution of sodium methoxide (415 mg, 7.7 mmol) in anhydrous methanol (15 ml) is added and the resulting solution is stirred in the cold for 2 more hrs. Acetic acid (2.2 ml) is then added and the solvents are evaporated in vacuo (i.v.). The residue is taken up in EtOAc (300 ml), washed with H 2  O (4×75 ml), 5% NaHCO 3  (75 ml) and brine, dried with MgSO 4  and evaporated i.v. to a clear oil (21.3 g). This material is purified by chromatography on a Baker silica gel column (425 g, packed under EtOAc). After a 100 ml forefraction, 25 ml EtOAc fractions are collected every 2.5 mins. Fractions 41-49 yield starting material and fractions 51-90 afford N-(t-butyldimethylsilyl)-4-(2-hydroxyethyl)-azetidin-2-one (19.4 g) as a clear oil: ir (neat) 2.88, 5.73, 5.80, 7.52, 7.67, 7.99, 8.40, 11.95, and 12.18 cm -1  ; nmr (CDCl 3 ) δ 0.25 (s, 6), 0.98 (s, 9), 1.82 (m, 2), 2.67 (dd, 1), 3.17 (dd, 1), 3.67 (t, 2), and 3.67 (m,1); mass spectrum m/e 172. 
     EXAMPLE 4 
     Preparation of N-(t-Butyldimethylsilyl)-4-(2-oxoethyl)-azetidin-2-one ##STR18## 
     Anhydrous chromium trioxide (CrO 3 ) (1.94 g, 19.4 mmol) is added to a solution of anhydrous pyridine (3.07 g, 38.8 mmole) in anhydrous methylene chloride (CH 2  Cl 2 ) (50 ml). The resulting mixture is stirred at room temperature for 15 mins. A solution of N-(t-butyldimethylsilyl)-4-(2-hydroxyethyl)-azetidin-2-one (0.74 g, 3.23 mmol) in anhydrous CH 2  Cl 2  (5 ml) is added all at once. After stirring at room temperature for 5 mins, the mixture is decanted and the dark, gummy residue is washed with more CH 2  Cl 2 . The combined CH 2  Cl 2  supernatant is evaporated i.v. The residue is taken up in diethyl ether and filtered to remove chromium salts. The ethereal filtrate is washed with 5% NaHCO 3 , 5% HCl, 5% NaHCO 3  and brine, dried with MgSO 4 , filtered, and evaporated i.v. to yield N-(t-butyldimethylsilyl)-4-(2-oxoethyl)-azetidin-2-one (0.54 g) as an off-white solid: ir(CHCl 3 ) 5.77, 5.80, 7.36, 7.60, 7.99, 8.50 and 11.95 cm -1  ; nmr (CDCl 3 ) δ 0.23 (s,3), 0.27 (s,3), 0.98 (s, 9), 2.63 (ddd, 1), 2.65 (dd, 1), 3.07 (ddd, 1), 3.37 (dd), 3.97 (m, 1), and 9.78 (t, 1); mass spectrum m/e 170 and 128. 
     EXAMPLE 5 
     Preparation of N-(t-Butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one ##STR19## 
     To a flame dried, 50 ml, 3-neck flask fitted with a N 2  inlet, magnetic stirrer, addition funnel, and serum cap are added anhydrous tetrahydrofuran (THF) (10.5 ml) and diisopropyl amine (0.579 ml, 4.13 mmol). The solution is cooled in an ice-methanol bath under N 2  and treated with 2.4 N n-butyl lithium in hexane (1.72 ml). After being stirred at -10° for 15 mins, the solution is cooled to -78° and treated dropwise over 9 mins with a solution of benzyl acetate (0.620 g, 4.13 mmol) in anhydrous THF (3.5 ml). After stirring 15 more mins at -78° C. the reaction mixture is treated dropwise over 13 mins with a solution of N-(t-butyldimethylsilyl)-4-(2-oxoethyl)-azetidin-2-one (0.894 g, 3.93 mmol) in anhydrous THF (6 ml). The reaction mixture is stirred at -78° an additional 15 mins and then quenched with 2.5 N HCl (6 ml). EtOAc (100 ml) is added and the organic phase is separated, washed with H 2  O (2×20 ml), 5% NaHCO 3  (20 ml) and brine, dried with MgSO 4 , and filtered. The filtrate is evaporated i.v. and the residue stripped with φH (benzene) to yield N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one (1.432 g) as an oil: ir (neat) 2.87, 5.73, 5.79, 7.57, 7.96, 8.39, 11.92, and 12.16 cm -1  ; mass spectrum m/e 362, 320, 278, 170 and 128. 
     EXAMPLE 6 
     Preparation of N-(t-Butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one ##STR20## 
     Anhydrous CrO 3  (2.274 g, 22.74 mmol) is added to a solution of anhydrous pyridine (3.597 g, 45.48 mmol) in anhydrous CH 2  Cl 2  (60 ml). After stirring at room temperature (25° C.) for 15 mins, the reaction mixture is treated all at once with a solution of N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one (1.432 g, 3.79 mmol) in anhydrous CH 2  Cl 2  (25 ml). The resulting mixture is stirred at 25° C. for 5 mins. The CH 2  Cl 2  layer is decanted from the dark, gummy residue which is triturated with more CH 2  Cl 2 . The combined CH 2  Cl 2  phase is evaporated i.v. The residue is triturated with diethylether (Et 2  O) (100 ml) in several portions and the Et 2  O extracts are filtered to remove chromium salts. The ethereal filtrate is washed with 5% NaHCO 3 , 1 N HCl, 5% NaHCO 3  and brine, dried with MgSO 4 , filtered, and evaporated i.v. to yield N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one (1.042 g) as a pale yellow oil: ir (neat) 5.72 (3 poorly resolved peaks), 7.59 7.98, 8.42, and 11.93 cm -1  ; nmr (CDCl 3 ) δ 0.18 (s, 3), 0.22 (s, 3), 0.97 (s, 9), 2.53 (dd, 1), 2.63 (dd, 1), 3.13 (dd, 1), 3.28 (dd, 1), 3.47 (s,2), 3.88 (m, 1), 5.17 (s, 2), and 7.33 (s, 5); mass spectrum m/e 360, 318, and 2.76. 
     EXAMPLE 7 
     Preparation of 4-(3-Benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one ##STR21## 
     N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-oxo-propyl)-azetidin-2-one (302 mg, 0.80 mmol) is dissolved in acetic acid (4.0 ml) and the solution is diluted with H 2  O(2.0 ml). The resulting solution is stirred in a securely stoppered, 10 ml, round-bottom flask in an oil bath maintained at 73° C. for 7 hrs. After cooling to room temperature, the reaction mixture is diluted with EtOAc and toluene and evaporated i.v. The residue is stripped twice with toluene to yield a yellow oil (220 mg). The crude product is chromatographed on Baker silica gel (8.8 g, packed under EtOAc). The column is eluted with EtOAc; 3 ml fractions being collected every 2.25 mins. Fractions 14-30 are combined and evaporated i.v. to provide 4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one (114 mg) as a clear oil: ir (neat) 3.04, 5.68, 5.72 and 5.83 cm -1  ; nmr (CDCl 3 ) δ 2.52 (ddd, 1), 2.67 (dd, 1), 3.02 (dd, 1), 3.12 (ddd, 1), 3.48 (s, 2), 3.88 (m, 1), 5.18 (s, 2), 6.17 (m, 1), and 7.37 (s, 5); mass spectrum m/e 261 (M + ), 233, 219, 192, 127 and 91. 
     EXAMPLE 8 
     Preparation of 4-(3-Benzyloxycarbonyl-3-diazo-2-oxopropyl)-azetidin-2-one ##STR22## 
     Freshly recrystallized p-carboxy benzene sulfonylazide (241 mg, 1.06 mmol) is added to a solution of 4-(3-benzyloxycarbonyl-2-oxopropyl)-azetidin-2-one (276 mg, 1.06 mmol) in anhydrous acetonitrile (6.6 ml). The resulting suspension is cooled in an ice-bath and stirred while Et 3  N (443 μl, 3.18 mmol) is added. The resulting yellow solution is stirred at room temperature. A precipitate forms quickly. After 90 mins, the mixture is diluted with EtOAc (50 ml) and filtered. The filtrate is washed with H 2  O (2×10 ml), 0.5 N NaOH (2×10 ml), H 2  O (4×10 ml) and brine, dried with MgSO 4 , filtered, and evaporated i.v. to an off-white solid (273 mg). This is triturated with Et 2  O to provide 4-(3-benzyloxycarbonyl-3-diazo-2-oxopropyl)-azetidin-2-one (227 mg) as a cream colored powder: ir (film from CHCl 3 ) 3.0, 4.65, 5.66, 5.82, 6.05, 7.21, 7.70 and 8.23 cm -  1 ; nmr (CDCl 3 ) δ 2.63 (ddd,1), 2.97 (dd, 1), 3.15 (ddd, 1), 3.40(dd, 1), 3.98 (m, 1), 5.27 (s, 2), 6.13 (m, 1), and 7.38 (s, 5); mass spectrum m/e 259, 245, 231, and 218. 
     EXAMPLE 9 
     Preparation of Benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate ##STR23## 
     A solution of 4-(3-benzyloxycarbonyl-3-diazo-2-oxopropyl)-azetidin-2-one (20 mg) in anhydrous benzene (5 ml) is irradiated for 60 mins at room temperature using a Hanovia 450 W medium-pressure mercury lamp and a Pyrex filter. Dry N 2  is bubbled through the solution prior to and during the photolysis. Evaporation of the solvent in vacuo gives an oil (17 mg) which is purified by chromatography on a 250μ×20×20 cm silica gel GF plate using 3:1 φH-EtOAc as developing solvent. The band at Rf 0.3 is removed and eluated with EtOAc to give a clear oil (2.4 mg). This material is further purified by tlc on a 250μ×7.5×8.5 cm silica gel GF plate. The cleanly resolved band at Rf 0.29 is removed and eluted with EtOAc to give benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (0.7 mg) as a clear oil: ir (CCl 4 ) 1783, 1773, and 1744 cm -1  ; ir (CHCl 3 ) 1767, 1741 cm -1  ; uv (Cy) 215 nm; nmr (CDCl 3 ) δ 2.36 (dd, J=8 and 18.5, 1), 2.90 (dd, J=6 and 18.5, 1), 2.92 (dd, J=2 and 16, 1), (3.63(dd, J=5 and 16, 1), 4.11 (m, 1), 4.71 (s, 1), 5.19 (s, 2) and 7.33 (s, 5); mass spectrum m/e 259 (M + ), 231 (M +  -28), 217 (M +  -42), 203, 187, 186, 168 (M +  -91), 124, and 91; high resolution mass spectrum m/e 259.0842 (C 14  H 13  NO 4 ). 
     EXAMPLE 10 
     Preparation of Benzyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR24## 
     Method A 
     A solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (13 mg, 0.05 mmol) in anhydrous CH 2  CL 2  (1 ml) is cooled in an ice-bath and treated with triethylamine (Et 3  N) (7 μl, 0.05 mmol). Ketene is passed through the resulting solution for 10 mins. The solvent and excess ketene are removed in vacuo to leave crude benzyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate 
     Method B 
     A solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (20 mg) in anhydrous pyridine (200 μl) and Ac 2  O (100 μl) is kept at 0° C. for 8 hrs. The mixture is evaporated in vacuo and the residue dissolved in EtOAc. This solution is washed with pH 2 phosphate buffer, 5% NaHCO 3 , and brine, dried with MgSO 4 , filtered, and evaporated i.v. to provide benzyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. By substituting Ac 2  O with ##STR25## in Method B, various 3-acyloxy derivatives are obtained. 
     EXAMPLE 11 
     Preparation of 3-acetoxy 1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic Acid ##STR26## 
     A mixture of benzyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (50 mg), 10% palladium on powdered charcoal (50 mg, prereduced in ethanol), and 1:2 dioxane-ethanol (5 ml) is hydrogenated at 40 psi for 1 hr. The catalyst is filtered off and washed with ethanol and ethyl acetate. The combined filtrate is evaporated to a residue which is dissolved in ethylacetate (5 ml) and water (5 ml). The pH is brought to 7 with 0.1 N sodium hydroxide. The aqueous phase is separated, washed with ethyl acetate, layered with ethyl acetate, and acidified to pH 2.5 with 0.1 N hydrochloric acid. The ethyl acetate layer is separated, washed with brine, dried with sodium sulfate, and evaporated in vacuo to afford 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid. 
     EXAMPLE 12 
     Preparation of the N,N&#39;-Dibenzylethylenediamine Salt of 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic Acid ##STR27## 
     A solution of N,N&#39;-dibenzylethylenediamine (24 mg) in dioxane (0.25 ml) is added dropwise to a solution of 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid (42 mg) in dioxane (0.5 ml). The resulting mixture is left in a refrigerator for several hours. The precipitate of N,N&#39;-dibenzylethylenediamine bis(3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid) is collected, washed with diethylether, and dried. 
     EXAMPLE 13 
     Preparation of Sodium 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR28## 
     3-Acetoxy-1-azabicyclo[3.2.0]-hept-2-en-7-one-2-carboxylic acid (17 mg) is dissolved in ethyl acetate (2 ml). The solution is layered with water (1 ml), stirred rapidly, and the pH brought to 7 with 0.1 N sodium hydroxide. The aqueous portion is separated, spun briefly on the rotary evaporator to remove dissolved ethyl acetate, and lyophilized to afford sodium 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 14 
     Preparation of Pivaloyloxymethyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR29## 
     A mixture of sodium 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (23 mg) and bromomethyl pivalate (29 mg) in hexamethylphosphoramide (0.5 ml) is stirred at room temperature and under a N 2  atmosphere for 2.5 hrs. The mixture is diluted with toluene (10 ml), washed with H 2  O (5×2 ml) and brine, dried with MgSO 4 , filtered, and evaporated in vacuo. The residue is purified by silica gel plc to afford pivaloyloxymethyl 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 15 
     Preparation of Benzyl 3-(α-azidoacetoxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR30## 
     Azidoacetyl chloride (21 μl) is added by syringe in an ice-cold, stirring solution of triethylamine (42 μl) and benzyl 1-azabicyclo[3.2.0]heptane-3,7-dione-2-carboxylate (52 mg) in anhydrous methylene chloride (2 ml). After stirring 30 mins in the cold, the reaction mixture is diluted with methylene chloride (5 ml), washed with H 2  O (2 ml), pH 3 phosphate buffer (2 ml), and 5% NaHCO 3  (2 ml), dried with MgSO 4 , filtered, and evaporated in vacuo. Chromatography of the residue on a silica gel GF plate gives benzyl 3-(α-azidoacetoxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 16 
     Preparation of 3-(α-aminoacetoxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid ##STR31## 
     A solution of benzyl 3-(α-azidoacetoxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid (25 mg) in dioxane (3 ml) is treated with 10% palladium on powdered charcoal (25 mg), ethanol (0.25 ml), 1 M dipotassium hydrogen phosphate (0.05 ml) and deionized H 2  O (1.75 ml). The resulting mixture is hydrogenated at 45 psi for 1 hr. The catalyst is filtered off and washed with 0.1 M pH 7 phosphate buffer (1 ml) and H 2  O (1 ml). The combined filtrate is washed with ethyl acetate, concentrated in vacuo to ca. 1 ml, and charged onto a Dowex 50-X4 (Na form) column. The product is eluted with deionized water and the desired fractions are concentrated in vacuo and lyophilized to afford 3-(α-aminoacetoxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid. 
     EXAMPLE 17 
     Following the procedure of Examples 10-16 the following species of the present invention are obtained. 
     
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 ##STR32##                                                                
Com-                                                                      
pound                                                                     
    R            X&#39;                                                       
                   R.sup.3&#39;   Remarks                                     
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(1.)                                                                      
     ##STR33##   O Na                                                     
(2.)                                                                      
     ##STR34##   O Na                                                     
(3.)                                                                      
     ##STR35##   O Na                                                     
(4.)                                                                      
     ##STR36##   O Na                                                     
(5.)                                                                      
     ##STR37##   O Na                                                     
(6.)                                                                      
     ##STR38##   O Na                                                     
(7.)                                                                      
     ##STR39##   O H                                                      
(8.)                                                                      
     ##STR40##   O H                                                      
(9.)                                                                      
     ##STR41##   O H                                                      
(10.)                                                                     
     ##STR42##   O H                                                      
(11.)                                                                     
     ##STR43##   O H          Me = methyl                                 
(12.)                                                                     
     ##STR44##   O H                                                      
(13.)                                                                     
     ##STR45##   O H          Obtained from product of Example 13 and     
                              MeOCHNH                                     
(14.)                                                                     
     ##STR46##   O H                                                      
(15.)                                                                     
     ##STR47##   O Na                                                     
(16.)                                                                     
     ##STR48##   O Na                                                     
(17.)                                                                     
     ##STR49##   O Na                                                     
(18.)                                                                     
     ##STR50##   O H                                                      
(19.)                                                                     
     ##STR51##   O H                                                      
(20.)                                                                     
     ##STR52##   O Na                                                     
(21.)                                                                     
     ##STR53##   O Na                                                     
(22.)                                                                     
     ##STR54##   O H                                                      
(23.)                                                                     
     ##STR55##   O H                                                      
(24.)                                                                     
     ##STR56##   O H                                                      
(25.)                                                                     
     ##STR57##   O H                                                      
(26.)                                                                     
     ##STR58##   O H                                                      
(27.)                                                                     
     ##STR59##   O Na                                                     
(28.)                                                                     
     ##STR60##   O Na                                                     
(29.)                                                                     
     ##STR61##   O Na                                                     
(30.)                                                                     
     ##STR62##   O Na                                                     
(31.)                                                                     
     ##STR63##   O Na                                                     
(32.)                                                                     
     ##STR64##   O                                                        
                    ##STR65##                                             
(33.)                                                                     
     ##STR66##   O CH.sub.2CHC(CH.sub.3).sub.2                            
(34.)                                                                     
     ##STR67##   O                                                        
                    ##STR68##                                             
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     EXAMPLE 18 
     Preparation of Benzyl 3-toluenesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR69## 
     p-Toluenesulfonic anhydride (33 mg, 0.1 mmol) and Et 3  N (17 μl, 0.12 mmol) are added to a solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (26 mg., 0.1 mmol) in anhydrous CH 2  Cl 2  (2 ml). The resulting solution is stirred at room temperature for 2 hours. The mixture is diluted with CH 2  Cl 2  (10 ml), washed with H 2  O (2×5 ml), pH 3 phosphate buffer (5 ml) and 5% NaHCO 3  (5 ml), dried with MgSO 4 , filtered and evarporated i.v. to provide benzyl 3-toluenesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 19 
     Preparation of sodium 3-toluenesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR70## 
     A mixture of benzyl 3-toluenesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (30 mg) and 10% palladium on powdered charcoal (25 mg) in dioxane (3 ml) and water (1 ml) containing sodium bicarbonate (7 mg) is hydrogenated at 40 psi for 30 mins. The mixture is filtered to remove the catalyst which is washed with several portions of H 2  O (3×3 ml). The combined filtrate is washed with ethyl acetate (3×2 ml), concentrated in vacuo to ca. 2 ml, and lyophilized to afford sodium 3-toluenesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 20 
     Preparation of sodium 3-methanesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR71## 
     By substituting an equivalent amount of methanesulfonic anhydride for p-toluenesulfonic anhydride of Example 18, benzyl 3-methanesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate is obtained. Hydrogenolysis of this material by the method described in Example 19 affords sodium 3-methanesulfonyloxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 21 
     Preparation of Benzyl 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR72## 
     A solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (26 mg) in anhydrous methanol (1 ml) at 0° C. is treated with ethereal CH 2  N 2  until a yellow color persists. The mixture is stirred 15 more minutes in the cold and then evaporated in vacuo. Chromatography of the residue on silica gel provides benzyl 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 22 
     Preparation of sodium 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR73## 
     A mixture of benzyl 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (50 mg) and 10% palladium on powdered charcoal (50 mg) in 1:1 dioxane-H 2  O (5 ml) containing sodium bicarbonate (12.5 ml) is hydrogenated at 40 psi for 30 mins. The mixture is filtered and the catalyst is washed with more water (5 ml). The combined filtrate is extracted with ethyl acetate, concentrated in vacuo to ca. 2 ml, and lyophilized to yield sodium 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 23 
     Following the procedures of Examples 21 and 22, the following species of the present invention are obtained when the reagent of Example 21 is substituted for another diazo reagent calculated to provide the species illustrated in the following table: 
     
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 ##STR74##                                                                
Com-                                                                      
pound    R            X&#39;      R.sup.3&#39;                                    
                                   Remarks                                
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(1.)     CH.sub.3     O       Na                                          
(2.)     CH.sub.2 CH.sub.3                                                
                      O       Na                                          
(3.)     CH.sub.2 CH.sub.2 CH.sub.3                                       
                      O       Na                                          
(4.)     CH.sub.2 CH.sub.2 CH.sub.2 CH.sub.3                              
                      O       Na                                          
(5.)     CH.sub.2 φ                                                   
                      O       Na                                          
(6.)     CHφ.sub.2                                                    
                      O       Na                                          
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     EXAMPLE 24 
     Preparation of Benzyl 3-(2-azidoethyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR75## 
     A mixture of benzyl 1-azabicyclo[3.2.0]heptane-3,7-dione-2-carboxylate (26 mg) and 2-azidoethyl trifluoromethyl sulfonate (26 mg) in anhydrous acetene (0.5 ml) containing powdered potassium carbonate (28 mg) is stirred at 25° C. in a capped flask for 2 hrs. The mixture is diluted with anhydrous ether (5 ml) and filtered. The filtrate is washed with water (2 ml) and brine, dried with MgSO 4 , filtered, and evaporated in vacuo. The residue is purified by plc on a silica gel GF plate to afford benzyl 3-(2-azidoethyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate. 
     EXAMPLE 25 
     Preparation of 3-(2-aminoethyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid ##STR76## 
     Benzyl 3-(2-azidoethyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate is hydrogenalized as described in Example 16 to provide 3-(2-aminoethyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acid. 
     EXAMPLE 26 
     Following the procedures of Example 22 and 24, the following species of the present invention are representatively obtained when the alkylating agent of Example 24 is substituted, in equivalent amount, for another alkylating agent calculated to provide the species illustrated in the following table. 
     
         ______________________________________                                    
 ##STR77##                                                                
Com-                                                                      
pound       R              R.sup.3&#39;                                       
______________________________________                                    
(1.)                                                                      
             ##STR78##     Na                                             
(2.)                                                                      
             ##STR79##     Na                                             
(3.)                                                                      
             ##STR80##     Na                                             
(4.)                                                                      
             ##STR81##     Na                                             
(5.)                                                                      
             ##STR82##     Na                                             
(6.)                                                                      
             ##STR83##     Na                                             
______________________________________                                    
 
    
     EXAMPLE 27 
     BENZYL 1-AZABICYCLO[3.2.0]HEPTAN-3,7-DIONE-2-CARBOXYLATE ##STR84## 
     A mixture of 4-(3-benzyloxycarbonyl-3-diazo-2-oxopropyl)-azetidin-2-one (718 mg. 2.5 mMol), rhodium (II) acetate (5 mg) and anhydrous benzene (50 ml) is deoxygenated by bubbling nitrogen through it for 45 minutes. The mixture is then stirred and heated in an oil bath maintained at 80° C. for 70 minutes. After cooling to room temperature, the mixture is filtered and the filtrate is evaporated under vacuum to an oil. Crystallization from ethyl acetate (5 ml)-diethylether (20 ml) provides benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (502 mg, 77% yield) as small, white prisms: mp 100°-102°; IR (CH 2  Cl 2 ) 1770; 1741 cm -1  ; UV (dioxane) 220 nm; NMR (CDCl 3 , 300 MHz) α 2.43 (dd,1,J=8 and 19, H4a), 2.94 (dd,1,J=6.5 and 19, H4b), 2.99  (dd,1,J=2 and 16, H6B), 3.63 (dd,1,J=5 and 16, H6α), 4.18 (m,1,H5), 4.76 (S,1,H2), 5.23 (S,2,CH 2  φ), and 7.40 (S,5,ArH); MS m/e 259 (M+), 231 (M+-28), 217 (M+-42), 203, 187, 186, 168 (M+-91), 124, and 91. 
     Anal. Calculated for C 14  H 13  NO 4  : C, 64.86; H, 5.05; N, 5.40. 
     Found: C, 64.92; H, 5.01; N, 5.11. 
     EXAMPLE 28 
     DICYCLOHEXYLAMMONIUM 1-AZABICYCLO[3.2.0]HEPTAN-3,7-DIONE-2-CARBOXYLATE ##STR85## 
     A solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (25.9 mg, 0.1 mMol) in dioxane (1.5 ml) is added to a mixture of 10% palladium on charcoal (5 mg) and dioxane (1.0 ml) which had been equilibrated under an atmosphere of hydrogen for 10 minutes. The resulting mixture is stirred under 1 atmosphere of hydrogen at room temperature for 30 mins., during which time 2.6 ml of hydrogen are absorbed. The mixture is filtered and the catalyst is washed with more dioxane (0.5 ml). The filtrate, which contains 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylic acid, is divided into two equal 1.5 ml portions. 
     One portion of the dioxane filtrate is treated with a solution of dicyclohexylamine (9.1 mg, 0.05 mMol) in dioxane. The solvent is removed under vacuum and the residue is triturated with diethyl ether to yield dicyclohexylammonium 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate as a white powder: IR (Nujol) 1764, 1637 cm -1  ; NMR (D 2  O) α 1.1-2.2 (m,--CH 2  CH 2  CH 2  CH 2  CH 2  --), 2.64 (dd,J=7.8 and 19.0, H4a), 2.89 (dd, J=7.9 and 19.0, H4b), 3.08 (dd, J=2 and 16.6, H6β), 3.26 (m, N-CH), 3.61 (dd, J=4.7 and 16.6, H6α), 4.17 (m, H5), and 4.8 (br s, HOD, obscures H2 resonance). 
     EXAMPLE 29 
     Benzyl 3-(p-toluenesulfonyloxy)-1-azabicyclo[3.2.0]hept-2-2n-7-one-2-carboxylate ##STR86## 
     p-Toluenesulfonic anhydride (326 mg, 1 mμol) and N,N-diisopropylethylamine (192 μl, 1.1 mμol) are added to an ice-cold, stirring solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (259 mg, 1 mμol) in anhydrous methylene chloride (10 ml). The resulting solution is stirred in the cold and under a nitrogen atmosphere for 2.5 hours. The solution is diluted with methylene chloride (20 ml), washed with water (10 ml). 1 M pH 3 phosphate buffer (10 ml) and 5% aqueous sodium bicarbonate (2×10 ml) dried with magnesium sulfate, filtered, and evaporated under vacuum to a semi-solid. This material is triturated with ice-cold ethyl acetate (2×2 ml) and diethyl ether (2×5 ml) to provide benzyl 3-(p-toluenesulfonyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (276 mg, 67%) as a white powder. Recrystallization from methylene chloridediethyl ether gives analytically pure product as small white needles: mp 103°-105°; IR (CH 2  Cl 2 ) 1786, 1723, 1382, and 1190 cm -1  ; NMR (CDCl 3 ) 8 2.44 (s,3,ArCh 3 ) 3.03 (dd,1,J=3.0 and 17.0, HGβ), 3.16 (dd,1,J=8.5 and 18.7,H4a), 3.32 (dd,1,J=10.0 and 18.7,H46), 3.55 (dd,1,J=5.5 and 17.0,HG), 4.21 (m,1,H5), 5.14 (ABq,2,J=12,CH 2  Ar), 7.35 (S,5,ArHO, 7.26 and 7.75 (two d&#39;s,4, J=9,ArH); UV(dioxane) 283 (E6600) and 277 (E6500) nm. 
     Anal., Calculated for C 21  H 19  NO 6  S: C, 61.01; H, 4.63; N, 3.39. Found: C, 59.94; H, 4.47; N, 3.26. 
     EXAMPLE 30 
     Benzyl 3-(p-nitrobenzenesulfonyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR87## 
     An ice-cold solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (20 mg, 0.077 mmol) in methylene chloride (2 ml) is treated with p-nitrobenzenesulfonic anhydride (37.3 mg, 0.096 mmol) and N,N-diisopropylethylamine (18.3 μl, 0.015 mmol). After stirring in the cold for 20 minutes, the solution is diluted with cold methylene chloride (1 ml) and cold 0.1 M pH 7 phosphate buffer (2 ml) and shaken. The organic phase is separated, washed with cold 0.1 M pH 7 phosphate buffer (2×2 ml), water and brine, dried with magnesium sulfate, and filtered. The filtrate is diluted with cold methanol (0.5 ml) and quickly evaporated under vacuum to give a solid. The crude product is triturated with cold methanol and dried under vacuum to provide benzyl 3-(p-nitrobenzenesulfonyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (26 mg) as a white solid: mp 86°-88°; IR (CH 2  Cl 2 ) 1794, 1723, 1521, and 1344 cm -1  ; UV (CHCl 3 ) 257 (ε 10,600) and 280 (ε 7,600) nm; NMR (CDCl 3 ) δ 3.08 (dd, 1, J=3.6 and 17, H6β), 3.25 (dd, 1, J=8.8 and 18, H3a), 3.35 (dd, 1, J=9.8 and 18, H4b), 3.59 (dd, 1, J=5.4 and 17, H6α), 4.26(m,1,H5), 5.10 (ABq, 2, J=21.2, CH 2  φ), 7.32 (s, 5, C 6  H 5 ), 8.03 and 8.22 (two d&#39;s, 4, J=9.3, NO 2  C 6  H 4 ). 
     Preparation of p-nitrobenzene sulfonic anhydride 
     A mixture of p-nitrobenzenesulfonic acid (20 g), phosphorous pentoxide (50 g) and 1,2-dichloroethylene (100 ml) is heated at reflux for 4 days. The hot supernatant is decanted from the gummy residue and allowed to cool to room temperature. The resulting crystalline precipitate of p-nitrobenzenesulfonic anhydride (1.5 g) is collected, washed with anhydrous diethylether, and dried under vacuum. The gummy residue is twice more refluxed overnight with 100 ml portions of dichloroethylene and worked up as above to provide additional p-nitrobenzenesulfonic anhydride (4.0 g). mp 171°-172°. 
     EXAMPLE 31 
     Benzyl 3-diphenylphosphoryl-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR88## 
     An ice-cold, stirring solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (13 mg, 0.05 mMol), 4-dimethylamine pyridine (1.2 mg, 0.01 mMol) and N,N-diisopropylethylamine (12.2 μl, 0.07 mMol) in anhydrous acetonitrile (0.5 ml) is treated with diphenyl chlorophosphate (12.4 μl, 0.06 mMol). The resulting solution is stirred in the cold and under a nitrogen atmosphere for 2 hours, then diluted with methylene chloride (5 ml), washed with water (2 ml), 0.1 M pH 7 phosphate buffer (2 ml) and brine, dried over magnesium sulfate, and filtered. Evaporation of the filtrate under vacuum leaves crude benzyl 3-diphenylphosphoryl-1-azabicyclo[3.2.0]-hept-2-en-7-one-2-carboxylate (22 mg) as an oil: UV (dioxane) 281 nm; NMR(CDCl 3 ) α2.90 (dd,l,J=3 and 17, H6β), 3.17 (m,2,H4a and H4b), 3.52  (dd,1,J=5.5 and 17, H6α), 4.13 (m,1,H5), 5.28 (S,2,CH 2  φ), and 7.30 (m,15,ArH). 
     EXAMPLE 32 
     N-(t-Butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-hydroxypropyl]-azetidin-2-one ##STR89## 
     A mixture of crude N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-hydroxypropyl)-azetidin-2-one (11.33 g, 30 mmol), ethanol (300 ml) and 10% palladium on charcoal (1.13 g) is hydrogenated at 50 psi for 1 hour. The mixture is filtered and the filtrate is treated with water (150 ml) containing sodium bicarbonate (2.52 g, 30 mmol) and concentrated under vacuum to ca 100 ml. The aqueous concentrate is washed with ethyl acetate (2×100 ml) and lyophilized to provide the sodium carboxylate (7.70 g) as a white powder. 
     The sodium salt and p-nitrobenzyl bromide (6.48 g, 30 mmol) are dissolved in anhydrous dimethyl formamide (150 ml) under a nitrogen atmosphere. After standing for 1 hour at room temperature, the solution is evaporated under vacuum to a semi-solid. The residue is taken up in ethyl acetate (200 ml), washed with water (2×200 ml) and brine, dried over magnesium sulfate, filtered, and evaporated under vacuum. The residual yellow oil is chromatographed on silica gel (250 g) using 1:1 toluene-ethyl acetate as eluting solvent to provide N-(t-butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-hydroxypropyl]-azetidin-2-one (8.92 g, 70%) as an oil which solidified on standing: IR (CH 2  Cl 2 ) 3585, 1733, 1527, and 1350 cm -1  ; NMR (CDCl 3 ) 8 0.22 (s,3,CH 3 ), 0.25 (s,3,CH 3 ), 0.93 (s,9,C(CH 3 ) 3 ), 1.16-2.33 (m,2,CH--CH 2  --CH), 2.40-3.47 (m,3,OH and H3  and H3β), 2.55 (d,2,J=6, CH 2  CO 2 ), 3.50-4.33 (m,2,H4 and CH--OH), 5.30 (s,2,CH 2  Ar), and 7.55, 8.27 (two d&#39;s,4,J=8.5, ArH). 
     EXAMPLE 33 
     N-(t-Butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-hydroxypropyl]-azetidin-2-one ##STR90## 
     A mixture of crude N-(t-butyldimethylsilyl)-4-(3-benzyloxycarbonyl-2-Hydroxypropyl)-azetidin-2-one (13.46 g, 35.6 mmol), 10% palladium on charcoa, and ethanol (200 ml) is hydrogenated at 40 psi for 30 mins. The mixture is filtered and the filtrate is evaporated under vacuum and stripped with toluene to give N-(t-butyldimethylsilyl)-4-(3-carboxy-2-hydroxypropyl)-azetidin-2-one (9.51 g) as an off-white solid: IR (neat film from Me 2  CO) 3200 (br), 1735, and 1700 (shifts to 1590 with Et 3  N) cm -1  ; NMR (Me 2  CO-d 6 ) 8 0.25 (s,6,2CH 3 ), 0.98 (s,9,C(CH 3 ) 3 ) 1.17-2.33 (m,2,CH--C CH 2  --CH), 2.50 (d,2,J=6.5, CH 2  CO 2 ), 2.50-3.40 (m,2,H3 and H3β), 3.97 (m,2,H4 and CHOH); MS on bistrimethylsilyl derivative m/e 431 (M+), 416  (M+-57) and 332 (374-42). 
     The crude carboxylic acid is suspended in anhydrous acetonitrite (150 ml) and treated with p-nitrobenzyl bromide (7.56 g, 35 mμol) and triethylamine (4.9 ml, 35 mμol). The resulting solution is kept at room temperature for 2 days and then in a refrigerator for 3 days. The reddish orange solution is evaporated under vacuum and the residue shaken with ethyl acetate (100 ml, 2×50 ml) and filtered to remove triethylammonium bromide. The ethyl acetate filtrate is washed with water (3×100 ml) and brine, dried with magnesium sulfate, filtered, and evaporated under vacuum to an amber oil (13.62 g). Crystallization from diethyl ether affords N-(t-butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-hydroxypropyl]azetidin-2-one (6.84 g) as an off-white powder. Chromatography of the mother liquors on a silica gel column using 1:1 toluene-ethyl acetate as eluting solvent affords addition product (3.14 g) as an oil which solidifies. 
     EXAMPLE 34 
     N-(t-Butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one ##STR91## 
     Anhydrous chromium trioxide (16.88 g 169 mmol) is added to a solution of anhydrous pyridine (27.3 ml, 338 mmol) in anhydrous methylene chloride (470 ml). The resulting mixture is stirred at room temperature for 30 minutes and then treated with a solution of N-(t-butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-hydroxypropyl]-azetidin-2-o one (8.92 g, 21.1 mmol) in methylene chloride (80 ml). The reaction mixture is stirred an additional 15 minutes at room temperature and then treated with 2-propanol (6.75 ml). The methylene chloride phase is decanted from the dark, tary residue and evaporated under vacuum. The residue from this operation is triturated with diethyl ether (350 ml) and filtered through a pad of magnesium sulfate which is washed with additional ether (150 ml). The ethereal filtrate is washed with water (200 ml), 5% aqueous sodium bicarbonate (200 ml) and brine, dried with magnesium sulfate, filtered, evaporated under vacuum, and stripped with toluene to afford the crude product (5.99 g) as an amber oil. Chromatigraphy on a silica gel column using 3:2 petroleum ether-ethyl acetate as eluting solvent yields N-(t-butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one (5.17 g, 58%) as a pale yellow, viscous oil which solidifies. Trituration with diethyl ether gives the product as small, white crystals: mp 65°-66.5° IR (CH 2  CL 2 ) 1732, 1522, and 1350 cm) NMR (CDCl 3 ) 8 0.20 (s,3,CH 3 ), 0.23 (s,3,CH 3 ), 0.93 (s,9,C(CH 3 ) 3 ), 2.58 (dd,1,J=2.7 and 15.7, H3β), 2.72 (dd,1, J=9.4 and 18.2, CH 2  COCH 2  CO 2 ), 3.19 (dd,1,J=4.0 and 18.2, CH 2  COCH 2  CO 2 ), 3.35 (dd,1,J=5.3 and 15.7,H3β), 3.55 (s,2, COCH 2  CO 2 ), 3.90 (m,1,H4), 5.30 (s,2,CH 2  Ar), 7.55 and 8.25 (two d 15 , 4,J-8.5, ArH); MS m/e 405 (M +  -15), 363 (M +  -57), 321 (363-42) and 136. 
     Anal. Calculated for C 20  H 28  N 2  O 6  Si: C,57.12; H,6.71; N,6.66. Found: C,57.28; H, 6.75; N, 6.60. 
     EXAMPLE 35 
     4-[3-(p-Nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one ##STR92## 
     A solution of N-(t-butyldimethylsilyl)-4-[3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one (5.17 g, 12.3 mMol) in methanol (55 ml) is treated with 1 N hydrochloric acid (6.2 ml) and then kept at room temperature for 200 mins. The solution is treated with 1 M dipotassium hydrogenphosphate (6.2 ml) and concentrated under vacuum. The residue is taken up in ethyl acetate (100 ml), washed with brine, dried over magnesium sulfate, filtered, and evaporated under vacuum. Triturating the resulting oil with diethyl ether yields 4-[3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one (3.42 g, 91%) as an off-white powder: mp 50°-52°; IR (CH 2  Cl 2 ) 3416, 1767, 1723, 1528, and 1352 cm -1  ; NMR (CDCl 3 ) α2.60 (ddd,1,J=1,2.7, and 15.1,H3β), 2.77 (dd,1,J=8.4 and 18.2, CHCH 2  CO), 3.13 (dd,1,J=5.1  and 18.2, CHCH 2  CO), 3.20 (ddd,1,J=2.4, 5.0, and 15.1, H3α), 3.57 (s,2,COCH 2  CO 2 ), 3.98 (m,1,H4); 5.27 (s,2,CH 2  Ar), 6.28 (br s,1,NH), 7.53 and 8.23 (two d&#39;s,4,J=8.5, ArH); mass spectrum m/e 306(M+), 264(M+-42), 237, 153, 125, 111, and 136. 
     EXAMPLE 36 
     4-[3-(p-Nitrobenzylorycarbonyl)-3-diazo-2-oxopropyl]-azetidin-2-one ##STR93## 
     p-Carboxybenzyenesulfonylazide (2.67 g, 11.8 mMol) and triethylamine (4.68 ml, 33.6 mMol) are added to an ice-cold, stirring solution of 4-[3-(p-nitrobenzyloxycarbonyl)-2-oxopropyl]-azetidin-2-one (3.42 g, 11.2 mMol) in anhydrous acetonitrile (70 ml). The resulting mixture is stirred in the cold for 10 minutes and at room temperature for 60 minutes. The mixture is diluted with ethyl acetate (200 ml) and filtered. The filtrate is washed with water (2×100 ml), 1 M pH3 phosphate buffer (50 ml), 0.1 M pH7 phosphate buffer (100 ml), and brine, dried over magnesium sulfate, filtered, and evaporated under vacuum to a yellow foam (3.75 g). The crude product is taken up in methylene chloride (ca. 10 ml), heated briefly with activated charcoal, and filtered through a pad of magnesium sulfate. The filtrate is diluted with diethyl ether (ca. 40 ml) and scratched to yield a precipitate. The precipitate is collected, washed with ether, and dried under vacuum to provide 4-[3-(p-nitrobenzyloxycarbonyl)-3-diazo-2-oxopropyl]-azetidin-2-one (3.29 g, 88%) as a pale yellow powder: mp 114.5°-116.5°; IR (CH 2  Cl 2 ) 3413, 2142, 1767, 1724, 1657, 1530, and 1352 cm -1  ; NMR (CDCl 3 ) α2.68 (ddd,1,J=1.2, 2.7, and 14.8, H3β), 3.02 (dd,1,J=8.4 and 18.0, CHCH 2  CO), 3.22 (ddd,1,J=2.4, 4.8, and 14.8, H3α); 343 (dd,1,J=4.6 and 18.0, CHCH 2  CO), 4.00 (m,1,H4), 5.38 (s,2,CH 2  Ar), 6.30 (brs,1,NH), 7.57 and 8.27 (two d&#39;s,4, J=8.5, ArH); mass spectrum m/e 332(M+), 304(M+-28), 290(M+-42), 262, and 263. 
     Anal., calculated for C 14  H 12  N 4  O 6  : C,50.61; H,3.64; N,16.86. 
     Found: C,50.34; H,3.42; N,16.72. 
     EXAMPLE 37 
     p-Nitrobenzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate ##STR94## 
     A suspension of 4-[3-(p-nitrobenzylocycarbonyl)-3-diazo-2-oxopropyl]-azetidin-2-one (2.93 g) and rhodium (II) acetate (15 mg) in anhydrous toluene (300 ml) is degassed by bubbling nitrogen through it for 60 minutes. The mixture is then stirred and heated in an oil bath maintained at 80° C. After a few minutes, the diazo compound dissolves and gas evolution commences. The mixture is heated at 80° C. for 100 minutes, then allowed to stand at room temperature for 30 mins. before filtering through a pad of celite. The filtrate is evaporated under vacuum to an oily residue which is triturated with diethyl ether to afford p-nitrobenzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (2.53 g, 94%) as an off-white powder. Recrystallization from ether provides analytically pure product: mp 127°-128°: IR (CH 2  Cl 2 ) 1776, 1753, 1529, and 1352 cm -1  ; NMR (CDCl 3 ) α2.47 (dd,1,J=8.2 and 18.8, H4a), 2.98 (dd,1,J=6.8 and 18.8, H4b), 3.00 (dd,1,J=2.0 and 12.0, H6β), 3.70 (dd,1,J=4.8 and 12.0, H6α), 4.20 (m,1,H5), 4.80 (s,1,H2), 5.32 (s,2,CH 2  Ar), 7.57 and 8.25 (two d&#39;s,4, J=8,ArH); mass spectrum m/e 304(M+), 276(M+-28), 262 (M+-42), and 168(M+-136). 
     Anal., calculated for C 14  H 12  N 2  O6: C, 55.27; H, 3.98; N, 9.21. 
     Found: C,55.06; H,4.03; N,8.99. 
     EXAMPLE 38 
     P-Nitrobenzyl 3-(p-Toluenesulfonyloxy)-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR95## 
     p-toluenesulfonic anhydride (520 mg, 1.59 mμol) and N,N-diisopropylethylamine (300 μl, 1.72 mμol) are added to an ice-cold, stirring solution of p-nitrobenzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (484 mg, 1.59 mμol) in anhydrous methylene chloride (17 ml). The resulting solution is stirred in the cold for 2 hours, then diluted with more methylene chloride, washed with water, 1 μph 3.4 phosphate buffer and saturated aqueous sodium bicaronate, dried with magnesium sulfate, filtered, and evaporated under vacuum. Addition of cold ethyl acetate and a few seed crystals to the oily residue induces crystallization. The product is collected, washed with cold ethyl acetate, and dried under vacuum to afford p-nitrobenzyl 3-(p-toluenesulfonyloxy)-1-azabicyclo[3.200]hept-2-en-7-one-2-carboxylate (446 mg, 61%) as off-white crystals: mp 99°-102° (dec.); IR (neat) 1790, 1725, 1521, 1345, and 1172 cm -1  ; UV (CH 2  Cl 2 ) 272 nm; NMR (CDCl 3 ) 8 2.40 (s,3,ArCH 3 ), 3.06 (dd,1,J=3.0 and 17.2, HGβ), 3.16 (dd,1,J=9.0 and 9.0,H4a), 3.31 (dd,1,J=9.0 and 10.0, H46), 3.59 (dd,1,J=5.8 and 17.2, HG), 4.24 (m,1,H5), 5.20 and 5.32 (ABq,2,J=14.0,CH 2  Ar), 7.32 and 7.77 (two d&#39;s,4,J=8.0, p-MeC 6  H 4 ), 7.51 and 8.19 (two d&#39;s,4,J=8.0,p-NO 2  C 6  H 4 ). 
     EXAMPLE 39 
     Benzyl 3-methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate ##STR96## 
     A solution of benzyl 1-azabicyclo[3.2.0]heptan-3,7-dione-2-carboxylate (25.9 mg, 0.1 mMol) in anhydrous hexamethylphosphoramide (1.0 ml) is cooled in an ice-bath and stirred under a nitrogen atmosphere. Dimethyl sulfate (11.4 μl, 0.12 mMol) and 57% sodium hydride in mineral oil (5.0 mg, 0.12 mMol) are added to the solution. The cooling bath is removed and the resulting mixture is stirred at room temperature for 60 minutes. The mixture is diluted with ethyl acetate (10 ml) and water (20 ml), shaken, and the layers separated. The organic layer is washed with water (3×5 ml) and brine, dried with magnesium sulfate, diluted with toluene (10 ml), and evaporated under vacuum to an oil. This material is chromatographed on a 0.25 mm×10×20 cm silica gel GF plate using 3:1 toluene-ethyl acetate as developing solvent. The major UV visible band at R f  0.1 was removed and eluted with ethyl acetate to provide benzyl 3 -methoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate (5.6 mg) as a clear oil: IR (CH 2  Cl 2 ) 1775 and 1700 cm -1  ; UV (EtOAc) 288 nm; NMR (CDCl 3 ) δ2.87 (dd, 1, J=2.8 and 16, H6β), 3.03 (m, 2, H4a and H4b), 3.50 (dd, 1, J=5.5 and 16, H6α), 3.80 (m, 1, H5), 3.92 (s, 3, CH 3 ), 5.28 (s, 2, CH 2  φ), and 7.40 (m, 5, C 6  H 5 ); mass spectrum m/e 273 (M+) and 231 (M+-42). 
     This product is also obtained by treating the bicyclo keto ester with dimethyl sulfate and excess potassium carbonate in hexamethylphosphoramide or dimethylformamide. 
     EXAMPLE 40 
     Preparation of Pharmaceutical compositions 
     One such unit dosage form comprises 120 mg of sodium 3-acetoxy-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylate with 20 mg. of lactose and 5 mg of magnesium stearate and placing the 145 mg mixture into a No. 3 gelatin capsule. Similarly, by employing more of the active ingredient and less lactose, other dosage forms can be put up in No. 3 gelatin capsules and should it be necessary to mix more than 145 mg of ingredients together, larger capsules such as compressed tablets and pills can also be prepared. The following examples are illustrative of the preparation of pharmaceutical formulations: 
     
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TABLET                PER TABLET                                          
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Sodium 3-acetoxy-1-azabicyclo[3.2.0]-                                     
hept-2-en-7-one-2-carboxylate                                             
                      125 mg.                                             
Cornstarch, U.S.P.     6 mg.                                              
Dicalcium Phosphate   192 mg.                                             
Lactose, U.S.P.       190 mg.                                             
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     The active ingredient is blended with the dicalcium phosphate, lactose and about half of the cornstarch. The mixture is then granulated with a 15% cornstarch paste (6 mg) and rough-screened. It is dried at 45° C. and screened again through No. 16 screens. The balance of the cornstarch and the magnesium stearate is added and the mixture is compressed into tablets, approximately 0.5 inch in diameter each weighing 800 mg. 
     
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PARENTERAL SOLUTION                                                       
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Ampoule:                                                                  
Sodium 3-acetoxy-1-azabicyclo[3.2.0]-                                     
hept-2-en-7-one-2-carboxylate                                             
                         500    mg.                                       
OPTHALMIC SOLUTION                                                        
Sodium 3-acetoxy-1-azabicyclo[3.2.0]-                                     
hept-2-en-7-one-2-carboxylate                                             
                         100    mg.                                       
Hydroxypropylmethyl      5      mg.                                       
Sterile Water  to        1      ml.                                       
OTIC SOLUTION                                                             
Sodium 3-acetoxy-1-azabicyclo[3.2.0]-                                     
hept-2-en-7-one-2-carboxylate                                             
                         100    mg.                                       
Benzalkonium chloride    0.1    mg.                                       
Sterile Water  to        1      ml.                                       
TOPICAL SOLUTION                                                          
Sodium 3-acetoxy-1-azabicyclo[3.2.0]-                                     
hept-2-en-7-one-2-carboxylate                                             
                         100    mg.                                       
Polyethylene Glycol 4000 U.S.P.                                           
                         400    mg.                                       
Polyethylene Glycol 400 U.S.P.                                            
                         1.0    gram                                      
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     The active ingredient in the above formulations may be administered alone or in combination with other biologically active ingredients, as for example, with other antibacterial agents such as lincomycin, a penicillin, streptomycin, novobiocin, gentamicin, neomycin, colistin and kanamycin, or with other therapeutic agents such as probenecid.