Disclosed is the antibiotic 5-methyl-2-(1-carboxyl-2-methyl-propen-1-yl)-3-oxo-6-thia-2-azabicyclo [2.2.0] hexane (I): ##STR1## Also disclosed are processes for preparing I and its pharmaceutically acceptable salts and esters; pharmaceutical compositions comprising such compounds; and methods of treatment comprising administering such compounds and compositions when an antibiotic effect is indicated.

BACKGROUND OF THE INVENTION 
This invention relates to 
5-methyl-2-(1-carboxyl-2-methyl-propen-1-yl)-3-oxo-6-thia-2-azabicyclo 
[2.2.0] hexane (I) and its pharmaceutically acceptable salts and esters 
which are useful as antibiotics: 
##STR2## 
This invention also relates to processes for preparing I; pharmaceutical 
compositions comprising I and methods of treatment comprising 
administering I 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 
antibiotic and the pharmaceutically acceptable salts and esters thereof 
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. aureus, 
Strep. pyogenes and B. subtilis, and gram negative bacteria such as E. 
coli, Proteus morganii, 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 
The compounds of the present invention (I) are prepared according to the 
following scheme: 
##STR3## 
In words relative to the above diagram, the starting material 1 
[R.dbd.benzyl; benzyl-6.alpha.-bromo-6.beta.-[1-hydroxyethyl] 
penicillinate; F. Di Ninno, et al., J. Org. Chem. 42 2960 (1977)] in a 
solvent such as tetrahydrofuran, diethyl ether, dichloromethane, or the 
like is treated with a triorganophosphine such as triphenylphosphine, 
tri-n-butylphosphine, hexamethylphosphorous triamide or the like and an 
azodicarboxylate such as diethylazodiazodicarboxylate, 
dimethylazidodicarboxylate, di-t-butylazodicarboxylate, or the like at a 
temperature of from -78.degree. C. to 25.degree. C. for from 0.5 to 48 
hours to provide 2, which upon reductive debromination in a solvent such 
as methanol, methanol-acetic acid, tetrahydrofuran or the like in the 
presence of a reducing agent such as zinc-silver couple, zinc-copper 
couple, tri-n-butyltin hydride, or the like at a temperature of from 
0.degree. C. to 80.degree. C. for from 0.5 to 24 hours yields 3. 
Relative to structure 1, 2, and 3, in the above diagram the radical R may 
be any conventional, readily removable carboxyl blocking group such as 
benzyl, p-nitrobenzyl, trichloroethyl, methyl, or the like. The 
de-blocking reaction is illustrated above, and discussed below. 
Alternatively, R may be a pharmaceutically acceptable ester moiety, such 
as pivaloyloxymethyl, 3-buten-1-yl, (2-methylthio)-ethyl or the like. 
The de-blocking procedure may be accomplished by any of a variety of 
well-known procedures such as hydrolysis or hydrogenation. Preferably the 
carboxyl blocking group R is removed by hydrogenation in a solvent such as 
a loweralkanol, for example, ethanol in the presence of a hydrogenation 
catalyst such as palladium, platinum or oxides thereof under 1-40 
atmospheres of hydrogen at from 0.degree. to 50.degree. C. for from 1 to 
10 hours. Salts of the free acid are easily prepared by treatment of the 
free acid dissolved in an organic solvent such as ethyl acetate, acetone, 
chloroform, or the like with an equivalent amount of an inorganic base 
such as sodium bicarbonate, sodium hydroxide, calcium carbonate or the 
like, evaporating the organic solvent and lyophilizing the aqueous phase. 
The products of this invention (I) form a wide variety of pharmacologically 
acceptable salts with inorganic and organic bases; these include, for 
example, metal salts derived from alkali metal or alkaline earth metal 
hydroxides, carbonates or bicarbonates and salts derived from primary, 
secondary or tertiary amines such as monoalkylamines, dialkylamines, 
trialkylamines, lower alkanolamines, di-loweralkanolamines, lower 
alkylenediamines, N,N-diaralkyl lower alkylenediamines, aralkylamines, 
amino substituted lower alkanols, N,N-di-lower alkylamino substituted 
lower alkanols, amino-, polyamino-and guanidino-substituted lower alkanoic 
acids and nitrogen containing heterocyclic amines. Representative examples 
include salts derived from sodium hydroxide, sodium carbonate, sodium 
bicarbonate, potassium carbonate, potassium hydroxide, calcium carbonate, 
trimethylamine, triethylamine, piperidine, morpholine, quinine, lysine, 
protamine, arginine, procaine, ethanolamine, morphine, benzylamine, 
ethylenediamine, N,N'-dibenzylethylenediamine, diethanolamine, piperazine, 
dimethylaminoethanol, 2-amino-2-methyl-1-propanol, theophylline, 
N-methylglucamine and the like. 
The compounds of the present invention, I, and salts thereof are valuable 
antimicrobial substances which are active against various gram-positive 
and gram-negative pathogens. Thus, the free acid and especially the salts 
thereof such as amine and metal salts, particularly the alkali metal and 
alkaline earth metal salts, are useful bactericides and can be used for 
removing susceptible pathogens from dental and medical equipment, for 
separating microorganisms, and for therapeutic use in humans and animals. 
For this latter purpose pharmacologically acceptable salts with inorganic 
and organic bases such as those known in the art and used for the 
administration of penicillins and cephalosporins can be utilized. For 
example, salts such as alkali metal and alkaline earth metal salts, and 
primary, secondary and tertiary amine salts can be used for this purpose. 
These salts can be combined with pharmaceutically acceptable liquid and 
solid vehicles to form suitable dosage unit forms such as pills, tablets, 
capsules suppositories, syrups, elixirs and the like which can be prepared 
in accordance with procedures well known in this art. 
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, Bacillus 
subtilis, Salmonella typhosa, Pseudomonas and Bacterium proteus. The 
antibacterials of the invention may further be utilized as additives to 
animal feedingstuffs, for preserving footstuffs 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 pesentation 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 prepartions 
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 oil 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 veterinary medicine the composition may, for example, be formulated as 
an intromammary preparation in either long acting 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 15 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 80 to 120 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 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 250 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. All 
temperatures are in .degree.C. 
EXAMPLE I 
Preparation of Sodium-5-methyl-3-oxo-6-thia-2-azabicyclo[2.2.0]-hexane 
carboxylate (4) 
##STR4## 
Preparation of 
2-[1-benzyloxycarbonyl-2-methylprop-1-enyl]-4.alpha.-bromo-5.alpha.-methyl 
-6-thia-2-azabicyclo[2.2.0]hexane (2) 
To a stirred solution of 46.3 mg (0.1 mmol) of 
benzyl-6.alpha.-bromo-6.beta.-[1-hydroxyethyl]penicillanate and 78 mg (0.3 
mmol) triphenylphosphine in 5 ml. dry tetrahydrofuran at room temperature 
(25.degree. C.) under a nitrogen atmosphere is added dropwise 36 .mu.l 
(0.22 mmole) of neat diethylazodicarboxylate. The resulting mixture is 
stirred for 20 minutes and evaporated under reduced pressure. The residue 
is purified by plate layer chromatography [3 developments 
.phi.H--CHCl.sub.3 (2:1)] to give 13.8 mg (31%) of 2: IR (CHCl.sub.3) 1770 
and 1724 cm.sup.-1 ; NMR (CDCl.sub.3); .delta. 1.64 (d, J=7 Hz, CH.sub.3), 
2.14 (s, CH.sub.3), 2.3 (s, CH.sub.3), 3.94 (qd, J=0.8 and 7.0 Hz, H-5), 
5.21 (ABq, J=12 Hz, CO.sub.2 CH.sub.2 Ph), 5.28 (d, J=0.8 Hz, H-1), and 
7.39 (s, ArH); mass spectrum m/e 397, 395 (M.sup.+) [Calc. for C.sub.17 
H.sub.18 NO.sub.3 SBr: 395.0188; Found: 395.0187], 316, 256, 231, 166, 
164, 91. 
Preparation of 
2-[1-benzyloxycarbonyl-2-methylprop-1-enyl]-5.alpha.-methyl-6-thia-2-azabi 
cyclo[2.2.0]hexane (3) 
To a stirred suspension of 53 mg. of zinc-silver couple in 0.4 ml methanol 
at room temperature is added in rapid succession 41 mg (0.7 mmol) of 
glacial acetic acid and a solution of 85 mg (0.2 mmol) of 2 in 0.5 ml 
methanol. The mixture is stirred under a nitrogen atmosphere for 1.5 hours 
and is then filtered. The filtrate is diluted with ethyl acetate and 
washed successively with dilute, aqueous hydrochloric acid, aqueous sodium 
bicarbonate, and saturated sodium chloride. The organic phase is dried 
with magnesium sulfate, filtered, and evaporated. Purification by plate 
layer chromatography [2 developments CHCl.sub.3 ] provides 39.2 mg (60%) 
of 3: IR (CHCl.sub.3) 1754 and 1718 cm.sup.-1 ; NMR (CDCl.sub.3) .delta. 
1.64 (d, J=6.5 Hz, CH.sub.3), 2.17 (s, CH.sub.3), 2.28 (s, CH.sub.3), 3.84 
(m, SCHCH.sub.3), 3.96 (app. t, J=3 and 4 Hz, H-4), 5.12 (dd, J=1.5 and 4 
Hz, H-1), 5.2 (ABq, J=12 Hz, CO.sub.2 CH.sub.2 Ph), and 7.38 (s, ArH); m/e 
317 (M.sup.+). 
Preparation of sodium-5.alpha.-methyl-6-thia-2-aza-bicyclo[2.2.0]-hexane 
carboxylate (4) 
A mixture of 30 mg. 10% Pd/C, 2 ml methanol, 0.4 ml deionized water, and 
0.2 ml. 0.1 N pH 7 phosphate buffer is hydrogenated at room temperature 
and 50 psi for 25 minutes. To the reduction mixture is added a solution of 
20 mg (0.06 mmol) of 3 in 0.6 ml methanol. The resulting mixture is 
hydrogenated at room temperature and 50 psi for 0.5 hour. The catalyst is 
removed by filtration through celite and washed with methanol. The 
filtrate is concentrated under reduced pressure and diluted with deionized 
water. The pH of the solution is adjusted to 9.0 with 0.2M aqueous sodium 
bicarbonate and is thoroughly extracted with ethyl acetate. The aqueous 
phase is then acidified to pH 2.5 with 2.5N aqueous hydrochloric acid and 
is thoroughly extracted with ethyl acetate. The combined extracts are 
dried (MgSO.sub.4), filtered, and evaporated to provide free acid I. 
The free acid is converted to its sodium salt 4 by treating an acetone 
solution of I (5 mg) with an equivalent weight of sodium bicarbonate 
dissolved in water, removing the acetone under reduced pressure, and 
lyophilizing the remaining aqueous phase. 
EXAMPLE II 
Preparation of Pharmaceutical Compositions 
One such unit dosage form consists in mixing 120 mg. sodium 
5.alpha.-methyl-6-thia-2-azabicyclo[2.2.0]hexane 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 lactone, other dosage forms can be put 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: 
______________________________________ 
TABLET PER TABLET 
______________________________________ 
Sodium-5.alpha.-methyl-6-thia-2-azabicyclo- 
[2.2.0] hexane carboxylate 
125 mg 
Cornstarch, U.S.P. 6 mg 
Dicalcium Phosphate 192 mg 
Lactose, U.S.P. 190 mg 
______________________________________ 
The active ingredient is blended with the dicalcium phosphate, lactose and 
about half of the cornstarch. The mixture is then granulated with 15% 
cornstarch paste (6 mg) and rough-screened. It is dried at 45.degree. C. 
and screened again through No. 16 screens. The remaining cornstarch and 
magnesium stearate, being the balance, is added and the mixture is 
compressed into tablets, approximately 0.5 inch in diameter each weighing 
800 mg. 
______________________________________ 
ENTERAL SOLUTION 
Ampoule: 
Sodium 5.alpha.-methyl-6-thia-2-azabicyclo[2.2.0]- 
hexane carboxylate 500 mg 
diluent: sterile water for injection 
2 ml 
OPTHALMIC SOLUTION 
Ampoule: 
Sodium 5.alpha.-methyl-6-thia-2-azabicyclo[2.2.0]- 
hexane carboxylate 100 mg 
Hydroxypropylmethyl cellulose 
5 mg 
Sterile Water 1 ml 
OPTIC SOLUTION 
Ampoule: 
Sodium 5.alpha.-methyl-6-thia-2-azabicyclo[2.2.0]- 
hexane carboxylate 100 mg 
Benzalkonium Chloride 0.1 mg 
Sterile Water 1 ml 
TOPICAL OINTMENT 
Sodium 5.alpha.-methyl-6-thia-2-azabicyclo[2.2.0]- 
hexane carboxylate 100 mg 
Polyethylene Glycol 4000 U.S.P. 
400 mg 
Polyethylene Glycol 400 U.S.P. 
10 gram 
______________________________________ 
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.