Penem derivatives, and composition containing them

Compounds of formula (I): ##STR1## (wherein R.sup.1 represents a C.sub.1 -C.sub.4 alkyl or C.sub.1 -C.sub.3 alpha-hydroxyalkyl group; PA0 R.sup.2 represents a hydrogen atom, a substituted or unsubstituted alkyl group or a cycloalkyl group; PA0 R.sup.3 represents a hydrogen atom or an alkyl group; and n is 1 or 2) and their salts and esters have valuable antibiotic activity and can be used for the treatment of diseases caused by a wide range of pathogenic microorganisms.

BACKGROUND TO THE INVENTION 
The present invention relates to a series of new penem compounds exhibiting 
valuable antibiotic activity, to a process for preparing these compounds 
and to antibiotic compositions containing the compounds as the active 
agent. 
The penicillins form a well known class of antibiotics, which have found 
considerable use in human and animal therapy for years. Chemically, the 
penicillins have in common a beta-lactam structure, commonly referred to 
as "penam", which may be represented by the following formula 
##STR2## 
The structure of many valuable penicillin derivatives has a double bond 
between the 2- and 3-positions and the resulting structure is known as 
"penem" and forms the basis for the semi-systematic nomenclature of the 
penicillins. This semi-systematic system of nomenclature is employed 
herein. 
The basic "penem" structure contains atoms or groups of atoms attached to 
the carbon atoms at the 2- and 6-positions and will normally contain a 
carboxy group or derivative thereof (e.g. salt or ester) attached to the 
carbon atom at the 3-position. Differences in the activities, potencies 
and other properties of the various penicillin derivatives are dictated by 
the various groups attached to these positions, but the way in which such 
groups affect the penicillin derivatives has not been elucidated. 
U.S. Pat. No. 4,260,618 discloses a series of penem derivatives having a 
heterocyclic-substituted thio group at the 2-position. 
We have now discovered a series of novel penem derivatives having, at the 
2-position, a heterocyclic-substituted thio group in which the 
heterocyclic ring has two nitrogen atoms, i.e. differing substantially in 
structure from those disclosed in U.S. Pat. No. 4,260,618. These penem 
derivatives have been found to have comparable antibacterial activities 
with and better biological and chemical stability tnan, for example, 
thienamycin which is one of the most potent and valuable beta-lactam 
antibiotics currently available. 
BRIEF SUMMARY OF INVENTION 
The novel compounds of the present invention may be represented by the 
formula (I); 
##STR3## 
(in which: R.sup.1 represents a C.sub.1 -C.sub.4 alkyl group or a C.sub.1 
-C.sub.3 alpha-hydroxyalkyl group; 
R.sup.2 represents a hydrogen atom, an alkyl group, a cycloalkyl group or 
an alkyl group having one or more C.sub.1 -C.sub.4 alkoxy, cyano, 
alkoxycarbonyl or halogen substituents; 
R.sup.3 represents a hydrogen atom or an alkyl group; and n is 1 or 2) 
and pharmaceutically acceptable salts and esters thereof. 
The invention also provides an antibiotic composition comprising an 
antibiotic in admixture with a pharmaceutically acceptable carrier or 
diluent, wherein the antibiotic comprises at least one compound of formula 
(I) or salt or ester thereof. 
DETAILED DESCRIPTION OF INVENTION 
Where R.sup.1 presents a C.sub.1 -C.sub.4 alkyl group, this may be a 
straight or branched chain group, i.e. a methyl, ethyl, propyl, isopropyl, 
butyl, isobutyl, sec-butyl or t-butyl group. Where R.sup.1 represents a 
C.sub.1 -C.sub.3 alpha-hydroxyalkyl group, this may be a hydroxymethyl, 
1-hydroxyethyl, 1-hydroxypropyl or 1-hydroxy-1-methylethyl group; it is 
preferably a C.sub.2 or C.sub.3 alpha-hydroxyalkyl group and is most 
preferably a 1-hydroxyethyl group. 
Where R.sup.2 represents an alkyl group, this is preferably a lower alkyl 
group having from 1 to 4 carbon atoms, i.e. a methyl, ethyl, propyl, 
isopropyl, butyl, isobutyl, sec-butyl or t-butyl group. Where R.sup.2 
represents a cycloalkyl group, it is preferably a cyclopropyl, cyclobutyl, 
cyclopentyl, cyclohexyl or cycloheptyl group. Where R.sup.2 represents a 
C.sub.1 -C.sub.4 alkoxy-substituted alkyl group, it is preferably a 
methoxymetnyl, ethoxymethyl, propoxymethyl, isopropoxymethyl, 
1-methoxyethyl or 2-methoxyethyl group. Where it is a cyano-substituted 
alkyl group, it is preferably a cyanometnyl, 1-cyanoethyl, 2-cyanoethyl, 
2-cyanopropyl or 1-methyl-2-cyanoethyl group. Where R.sup.2 represents an 
alkoxycarbonyl-substituted alkyl group, the alkoxy and alkyl groups 
thereof are preferably C.sub.1 -C.sub.4 groups and it is preferably a 
methoxycarbonylmethyl, ethoxycarbonylmethyl, 2-methoxycarbonylethyl or 
2-ethoxycarbonylpropyl group. Where R.sup.2 represents a 
halogen-substituted alkyl group, it is preferably a C.sub.1 -C.sub.4 
group, e.g. a 2-fluoroethyl, 2-fluoropropyl, 2-fluoro-1-metnylethyl, 
trifluoromethyl or 2,2,2-trifluoroethyl group. 
R.sup.2 preferably represents a hydrogen atom, a C.sub.1 -C.sub.3 alkyl 
group or a (C.sub.1 -C.sub.2 alkoxy)-(C.sub.1 -C.sub.2 alkyl) group, most 
preferably a hydrogen atom, a methyl group, an ethyl group or a 
methoxymethyl group. 
Where R.sup.3 represents an alkyl group, this is preferably a lower alkyl 
group having from 1 to 4 carbon atoms and may be a straight or branched 
chain group, i.e. a methyl, ethyl, propyl, isopropyl, butyl, isobutyl, 
sec-butyl or t-butyl group. R.sup.3 preferably represents a hydrogen atom 
or a methyl group. 
The integer represented by n may be 1 or 2 and is preferably 1. 
The compounds of the invention, being acids, will, of course, form salts 
and the pharmaceutically acceptable salts form part of the present 
invention. Suitable salts include salts with metals, such as lithium, 
sodium, potassium, calcium or magnesium, the ammonium salts and salts with 
organic amines, such as the cyclohexylammonium, diisopropylammonium or 
triethylammonium salts. The sodium and potassium salts are preferred. 
The compounds also form esters and pharmaceutically acceptable esters form 
part of the present invention. The esters are preferably lower aliphatic 
acyloxymethyl, lower 1-alkoxycarbonyloxyethyl or (5-methyl-2-oxo 
1,3-dioxolen-4-yl)methyl esters. The lower aliphatic acyloxymethyl groups 
preferably have from 2 to 5 carbon atoms in tne acyl moiety and examples 
of such groups include the acetoxymethyl, propionyloxymethyl, 
butyryloxymethyl, isobutyryloxymethyl and pivaloyloxymethyl groups, of 
which the pivaloyloxymethyl group is preferred. The lower 
1-alkoxycarbonyloxyethyl groups preferably have from 1 to 4 carbon atoms 
in the lower alkoxy moiety and examples include the 
1-methoxycarbonyloxyethyl, 1-ethoxycarbonyloxyethyl, 
1-propoxycarbonyloxyethyl, 1-isopropoxycarbonyloxyethyl, 
1-butoxycarbonyloxyethyl and 1-isobutoxycarbonyloxyethyl groups. The 
esters employed are preferably physiologically active; specifically, we 
prefer esters which undergo hydrolysis in the body of the patient 
(normally human) to liberate the free acid, which then serves as the 
effective and active therapeutic substance. It is for this reason that the 
lower aliphatic acyloxymethyl, lower 1-alkoxycarbonyloxyethyl and 
(5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl esters are particularly 
preferred, as these are well known to hydrolyze in the human body to 
liberate the free acid. 
However, the free acid or a pharmaceutically acceptable salt thereof is 
preferred. 
Examples of preferred compounds of the present invention appear in the 
following list: 
1. 2-(2-cyanomethyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-6-( 
1-hydroxyethyl)-2-penem-3-carboxylic acid 
2. 
6-isopropyl-2-(2-methyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-2-penem-3-ca 
rboxylic acid 
3. 
6-(1-hydroxyethyl)-2-(3,4,5,6-tetrahydropyrimidin-5-ylthio)-2-penem-3-carb 
oxylic acid 
4. 
6-(1-hydroxyethyl)-2-(2-methyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-2-pen 
em-3-carboxylic acid 
5. 
6-(1-hydroxyethyl)-2-(2-methoxymethyl-3-4,5,6-tetrahydropyrimidin-5-ylthio 
)-2-penem-3-carboxylic acid 
6. 6-(1-hydroxyethyl)-2-(4,5,6,7-tetrahydro-2H-1,3- 
diazepin-5-ylthio)-2-penem-3-carboxylic acid 
7. 6-(1-hydroxyethyl)-2-(2-methyl-4,5,6,7-tetrahydro-2H- 
1,3-diazepin-5-ylthio)-2-penem-3-carboxylic acid 
8. Pivaloyloxymethyl 
6-(1-hydroxyethyl)-2-(2-methyl-3,4,5,6-tetrahydropyridimidin-5-ylthio)-2-p 
enem-3-carboxylate 
9. 
6-(1-hydroxyethyl)-2-(2-methoxycarbonylmethyl-3,4,5,6-tetrahydropyrimidin- 
5-ylthio)-2-penem-3-carboxylic acid 
10. 
6-(1-hydroxyethyl)-2-(2-trifluoromethyl-3,4,5,6-tetrahydropyrimidin-5-ylth 
io)-2-penem-3-carboxylic acid 
11. 
2-[2-(2-fluoroethyl)-3,4,5,6-tetrahydropyrimidin-5-ylthio)-6-(1-hydroxyeth 
yl)]-2-penem-3-carboxylic acid 
12. 
2-(2-ethyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-6-(1-hydroxyethyl)-2-pene 
m-3-carboxylic acid 
13. 
6-(1-hydroxyethyl)-2-(2-isopropyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-2- 
penem-3-carboxylic acid 
14. 2-(2-cyclopentyl-3,4,5,6-tetrahydropyrimidin-5 
-ylthio)-6-(1-hydroxyethyl)-2-penem-3-carboxylic acid 
15. 
6-ethyl-2-(2-methoxymethyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-2-penem-3 
-carboxylic acid 
16. 
2-(2,3-dimethyl-3,4,5,6-tetrahydropryimidin-5-ylthio)-6-(1-hydroxyethyl)-2 
-penem-3-carboxylic acid 
Of the above, the most preferred are compounds No. 3, 4, 5, and 12 and 
their salts. 
The compounds of the present invention may exist in the form of various 
optical isomers, because of the presence of various asymmetric carbon 
atoms, and may also exist in the form of various geometric isomers. All of 
the isomers are represented by a single, plane formula in the 
specification and claims; however, the present invention contemplates the 
use of either the individual isomers or of mixtures, e.g. racemates, 
thereof. The preferred compounds are those having the (5R,6S) 
configuration and, where R.sup.1 represents an alpha-hydroxyalkyl group, 
the hydroxy group is preferably in the R-configuration 
The compounds of the present invention may be prepared by either of the 
following Methods; 
Method A 
Compounds of the invention may be prepared as illustrated by the following 
reaction scheme; 
##STR4## 
In the above formulae, R.sup.1, R.sup.2, R.sup.3 and n are as defined 
above. R.sup.4 represents a hydrogen atom or an ester group, preferably a 
lower aliphatic acyloxymethyl group, a lower 1-alkoxycarbonyloxyethyl 
group or a (5-methyl-2-oxo-1,3-dioxolen-4-yl)methyl group. R.sup.5 
represents an alkyl group, a C.sub.1 -C.sub.3 alpha-hydroxyalkyl group or 
a C.sub.1 -C.sub.3 alpha-hydroxyalkyl group in which the hydroxy group has 
been protected (for example an alpha-acyloxyalkyl, 
alpna-alkylsulphonyloxyalkyl, alpha-arylsulphonyl-oxyalkyl or 
alphatrialkylsilyloxyalkyl group). R.sup.6 represents a hydrogen atom or a 
carboxy-protecting group, which may or may not be the same as any ester 
group represented by R.sup.4, but which will normally be different. 
R.sup.7 and R.sup.8 represent amino-protecting groups. R.sup.9 represents 
a lower, preferably C.sub.1 -C.sub.4, alkyl group. 
In step (a) of this reaction, tne compound of formula (II) is first 
subjected to a reaction to eliminate the amino-protecting groups 
represented by R.sup.7 and R.sup.8. This reaction may be carried out by 
conventional means and the nature of the reaction employed will, of 
course, depend upon the particular amino-protecting groups chosen. For 
example, where the protecting groups are aralkyloxycarbonyl groups (for 
example benzyloxycarbonyl or p-nitrobenzyloxycarbonyl), this elimination 
is preferably effected by catalytic reduction using platinum or 
palladium-on-charcoal as a catalyst; occasionally, this reaction may also 
lead to elimination of the hydroxy-protecting group if R.sup.5 represents 
a protected alpha-hydroxyalkyl group and/or elimination of the 
carboxy-protecting group represented by R.sup.6. The resulting product may 
then be reacted, without any intermediate isolation, with the iminoether 
of formula HN.dbd.C(R.sup.2)--OR.sup.9. In the iminoether, R.sup.9 
represents a lower alkyl group, preferably a methyl group, and the 
iminoether may be employed as such or in the form of an acid addition 
salt. 
Both parts of step (a) are preferably effected in the presence of an 
aqueous solvent, the nature of which is not critical to the process of the 
invention, although we prefer to employ an aqueous phosphate buffer 
maintained at a pH value of from 7 to 9, particularly about 8. The 
reaction is preferably effected at a relatively low temperature e.g., from 
0.degree. C. to ambient temperature and the time required for the reaction 
will vary, depending upon the reaction temperature, but it will usually be 
from 10 minutes to 2 hours. 
After completion of the reactions of step (a), the desired compound (III) 
may be recovered from the reaction mixture by conventional means and, if 
necessary, further purified by such conventional techniques as 
recrystallization, preparative thin layer chromatography or column 
chromatography. 
Where, in the compound of formula (II), R.sup.5 represents an alkyl group 
or an alpha-hydroxyalkyl group and R.sup.7 represents a hydrogen atom or a 
desired ester group, or where the reaction employed to eliminate the 
amino-protecting groups represented by R.sup.7 and R.sup.8 also had the 
effect of eliminating any hydroxy-protecting group in a protected 
alpha-hydroxyalkyl group represented by R.sup.5 or had the effect of 
eliminating any carboxy-protecting group represented by R.sup.6, then the 
resulting compound of formula (III) may be the desired final product. 
However, where R.sup.5 in the compound of formula (III) represents a 
protected alpha-hydroxyalkyl group and/or R.sup.6 represents a 
carboxy-protecting group, tnen it will be desired to effect step (b) to 
eliminate the unwanted protecting group or groups. The nature of the 
reaction or reactions employed to remove undesired protecting groups will, 
of course, vary depending upon the nature of the protecting group in 
question and, in some cases, it may be possible to eliminate two 
protecting groups simultaneously by a single reaction whereas, in other 
cases, it may be desired to eliminate two protecting groups separately by 
means of two separate reactions. 
For example, where R.sup.6 represents a protecting group which can be 
removed by reduction, for example, a halogenated alkyl group, an aralkyl 
group or a benzhydryl group, the compound of formula (III) is contacted 
with a reducing agent; different reducing agents are preferred, depending 
upon the nature of tne protecting group. Where the carboxy-protecting 
group is a halogenated alkyl group (e.g. a 2,2-dibromoethyl or 
2,2,2-trichloroethyl group), a preferred reducing agent is zinc with 
acetic acid. When the protecting group is an aralkyl group (for example a 
benzyl or p-nitrobenzyl group) or a benzhydryl group, the reduction is 
preferably effected using a catalyst (such as palladium-on-charcoal) or 
using an alkali metal sulphide (such as sodium sulphide or potassium 
sulphide). These reactions are preferably effected in the presence of a 
solvent, the nature of which is not critical, provided that it does not 
adversely affect the reaction. Preferred solvents include: alcohols, such 
as methanol or ethanol; ethers, such as tetrahydrofuran or dioxane; fatty 
acids, such as acetic acid; and mixtures of one or more of these organic 
solvents with water. The reaction is preferably effected at a relatively 
low temperature, for example, from 0 .degree. C. to ambient temperature. 
The time required for the reaction will vary, depending upon the nature of 
the starting materials and the reducing agents, but usually a period of 
from 5 minutes to 12 hours will suffice. 
After completion of the reaction, the desired compound may be recovered 
from the reaction mixture by conventional means. For example, one suitable 
recovery procedure comprises filtering off insolubles, washing the 
remaining aqueous phase with a water-immiscible organic solvent and 
finally distilling off the water to give the desired product. This product 
may, if necessary, be further purified by such conventional techniques as 
recrystallization, preparative thin layer chromatography or column 
chromatography. 
Where R.sup.5 represents a protected alpha-hydroxyalkyl group, the 
protecting group may be removed prior to, simultaneously with or after 
removal of any carboxy-protecting group represented by R.sup.6 and the 
nature and sequence of any elimination reaction or reactions will depend 
upon the nature of the respective protecting groups. 
Where the group represented by R.sup.5 is a lower aliphatic acyloxyalkyl 
group, such as an acetoxyalkyl group, the acyl group can be removed by 
contacting the compound with a base in the presence of an aqueous solvent. 
The nature of the solvent employed is not critical and any solvent 
commonly used for hydrolysis reactions may equally be used for this 
reaction. We prefer to use water or a mixture of water with an organic 
solvent, such as an alcohol (e.g. methanol, ethanol or propanol) or an 
ether (e.g. tetrahydrofuran or dioxane). The base employed is not 
particularly critical, although care should be taken to use a compound 
which does not affect other parts of the compound, particularly the 
beta-lactam ring. Preferred bases are alkali metal carbonates, 
particularly sodium carbonate or potassium carbonate. The reaction 
temperature is not critical, although a relatively low temperature, e.g. 
from 0.degree. C. to ambient temperature, is preferred, in order to 
control side reactions. The time required for the reaction will vary, 
depending upon the nature of the starting materials and upon the reaction 
temperature, but a period of from 1 to 6 hours will normally suffice. 
Where the group represented by R.sup.5 is an 
alpha-aralkyloxycarbonyloxyalkyl group, such as a 
benzyloxycarbonyloxyalkyl or p-nitrobenzyloxycarbonyloxyalkyl group, the 
aralkyloxycarbonyl protecting group may be eliminated by contacting the 
compound with a reducing agent. Examples of reducing agents and reaction 
conditions which may be employed for this reaction are the same as those 
given above for the removal of a carboxy- protecting group R.sup.6, where 
that group is an aralkyl group; accordingly, where R.sup.6 represents an 
aralkyl group and R.sup.5 represents an aralkyloxycarbonyloxyalkyl group, 
the two protecting groups may be removed simultaneously by this reaction. 
Where the group represented by R.sup.5 is a trialkylsilyloxyalkyl group, 
for example a t-butyldimethylsilyloxyalkyl group, the trialkylsilyl 
protecting group can be removed by treating the compound with 
tetrabutylammonium fluoride. The reaction is preferably effected in the 
presence of a solvent, the nature of which is not critical, provided that 
it has no adverse effect upon the reaction; suitable solvents are ethers 
such as tetrahydrofuran or dioxane. The reaction is preferably effected at 
aoout ambient temperature and will normally require from 10 to 18 hours. 
Other protecting groups may similarly be removed by reactions well known in 
the art. 
After completion of these reactions, the desired product may be recovered 
from the reaction mixture by conventional means and, if necessary, may be 
further purified by such conventional techniques as recrystallization, 
preparative thin layer chromatography or column chromatography. 
The compound of formula (II) used as a starting material in the above 
reaction scheme is a novel compound and may be prepared from known 
compounds by either of the following Preparative methods 
Preparative Method (i) 
As illustrated by the following reaction scheme: 
##STR5## 
In the above formulae, R.sup.5, R.sup.6, R.sup.7, and R.sup.8 and n are as 
defined above, whilst Ac represents an acetyl group and Ph represents a 
phenyl group. 
Step (a) comprises reacting a mercaptane of formula (V) with an equimolar 
amount of sodium methoxide in methanol, reacting the resulting product 
with carbon disulphide and then reacting the product of this reaction with 
the compound of formula (IV). 
Step (b) comprises reacting the resulting compound of formula (VI) with 
glyoxylic acid or an ester thereof, to give the compound of formula (VII). 
This reaction may be effected in a solvent in a conventional manner. 
Step (c) comprises reacting the resulting compound of formula (VII) with 
thionyl chloride or thionyl bromide in the presence of a base and then 
reacting the product with triphenylphosphine; again, this reaction is 
carried out in the presence of a solvent in a conventional matter. 
Step (d) comprises heating the resulting compound of formula (VIII) to give 
the desired compound of formula (II). This reaction may be carried out in 
the presence of a solvent under conditions conventional for Wittig 
reactions. 
Preparative Method (ii) 
Compounds of formula (II) may also be prepared by reacting a compound of 
formula (IX) with a compound of formula (X), as illustrated below: 
##STR6## 
In the above formulae, R.sup.3, R.sup.5, R.sup.6, R.sup.7, R.sup.8 and n 
are as defined above. 
The reaction is preferably effected in the presence of triphenylphosphine 
and of diethyl azodicarboxylate in the presence of a solvent in a 
conventional manner. 
Method B 
The compounds of the invention may also be prepared as illustrated by the 
following reaction: 
##STR7## 
In the above formulae, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and n 
are as defined above: R.sup.10 represents a carboxy-protecting group; and 
R.sup.11 represents an alkyl group or an amino-protecting group. 
Examples of amino-protecting groups which may be represented by R.sup.11 
are as illustrated in relation to the groups represented by R.sup.7 and 
R.sup.8 and the methods employed for removing this group are as described 
for the first part of step (a) of Method A. Similarly, examples of 
carboxy-protecting groups which may be represented by R.sup.10 have been 
given in relation to the group represented by R.sup.6 and methods of 
removing such groups have been given in step (b) of Method A. 
The compound of formula (XI) is a novel compound and may be prepared, for 
example, by Preparative Method (iii). 
Preparative Method (iii) 
The compound of formula (XI) may be prepared as illustrated by the 
following reaction scheme: 
##STR8## 
In the above formulae, R.sup.2, R.sup.5, R.sup.10, R.sup.11, n, Ac and Ph 
are as hereinbefore defined. Steps (a) to (d) of this reaction scheme 
correspond to and may be carried out under the same conditions as (a) to 
(d) of Preparative Method (i). 
The compounds of the invention have been found to exhibit excellent 
antibacterial activity, comparable with that of the well known and 
extremely potent antiobiotic, thienamycin. The compounds exhibit their 
activity against both gram-positive microorganisms, such as Staphylococcus 
aureus or Bacillus subtilis, and gram-negative microorganisms, such as 
Escherichia coli, Shigella flexneri, Klebsiella pneumoniae, Proteus 
vulgaris, Pseudomonas aeruginosa and species of Serratia and Enterobacter. 
The activities of certain of the compounds of the invention against various 
bacteria, in terms of their minimal inhibitory concentrations (microg/ml), 
determined by the agar plate dilution method, are shown in the following 
Table. The compounds of the invention are identified as follows: 
Compound A: (5R, 
6S)-6-[1-(R)-hydroxyethyl]-2-(3,4,5,6-tetrahydropyrimidin-5-ylthio)penem-3 
-carboxylic acid: 
Compound B: 
(5R,6S)-6-[1-(R)-hydroxyethyl]-2-(2-methyl-3,4,5,6-tetrahydropyrimidin-5-y 
lthio)penem-3-carboxylic acid. 
As a control, similar tests were carried out against the known antibiotic, 
thienamycin, and the results of these tests are also shown in the 
following Table. 
TABLE 
______________________________________ 
Microorganism A B thienamycin 
______________________________________ 
Staphylococcus aureus 209 P 
.ltoreq.0.01 
.ltoreq.0.01 
.ltoreq.0.01 
Staphylococcus aureus 56 
.ltoreq.0.01 
.ltoreq.0.01 
.ltoreq.0.01 
Escherichia coli NIHJ 
0.2 0.2 0.1 
Escherichia coli 609 
0.2 0.2 0.1 
Shigella flexneri 2a 
0.2 0.2 0.1 
Psuedomonas aeruginosa 
3.1 6.2 6.2 
Klebsiella pneumoniae 806 
0.4 0.2 0.1 
Klebsiella pneumoniae 846 
0.4 0.2 0.1 
Proteus vulgaris 
6.2 3.1 3.1 
Salmonella enteritidis G 
0.4 0.2 0.2 
______________________________________ 
Accordingly, the compounds of the invention are useful for the treatment of 
diseases caused by these pathogenic microorganisms. They can be 
administered for this purpose orally, for example in the form of tablets, 
capsules, granules, powders or syrups, or parenterally, for example 
through intervenous or intramuscular injections. The dose will vary, 
depending upon the age, body weight and condition of the patient and on 
the form and times of administration; however, in general, the adult daily 
dose would be from 200 to 3000 mg of the compound, which may be 
administered in a single dose or in divided doses.

The preparation of certain of the compounds of the invention is further 
illustrated by the following Examples, whilst tne preparation of certain 
starting materials is illustrated in the following Preparations. 
EXAMPLE 1 
(5R,6S)-6-[1-(R)-Hydroxyethyl]-2-(3,4,5,6-tetrahydropyrimidin-5-ylthio)pene 
m-3-carboxylic acid 
30mg of p-nitrobenzyl 
(5R,6S)-2-[1,3-bis(p-nitrobenzyloxycarbonylamino)propan-2-ylthio]-6-[1-(R) 
-hydroxyethyl]penem-3-carboxylate were dissolved in 5 ml of 
tetrahydrofuran. To this solution were added 5 ml of a phosphate buffer 
having a pH of 7.1 and 60 mg of 10% w/w palladium-on-charcoal. The mixture 
was then stirred in a stream of hydrogen at room temperature for 3 hours, 
after which it was left to stand overnight at room temperature. The 
catalyst was filtered off using a Celite (trade mark) filter aid. The 
filtrate was washed twice with ethyl acetate and then concentrated to 
about 5 ml by evaporation under reduced pressure. This aqueous residue was 
ice-cooled and adjusted to a pH value of 8.5 by the addition of a 0.5N 
aqueous solution of sodium hydroxide. 17 mg of methyl formimidate 
hydrochloride were added to the resulting solution. The mixture was 
adjusted to a pH value of 8.5 by the addition of an aqueous solution of 
sodium hydroxide, stirred under ice-cooling for 10 minutes, adjusted to a 
pH value of 7.0 by the addition of 0.5N hydrochloric acid and subjected to 
column chromatography through Diaion (trade mark) HP20AG, eluted with 10% 
v/v aqueous acetone, to give 2.1 mg of the desired compound as a 
colourless powder. 
Infrared absorption spectrum.nu..sub.max (KBr) cm.sup.-1 : 3400, 1765, 
1670, 1590. 
Nuclear magnetic resonance spectrum (D.sub.2 O) .delta.ppm: 1.32 (3H, 
doublet, J=6.0 Hz); 3.2-3.8 (5H, multiplet); 3.95 (1H, doubled doublet, 
J=8.0 and 2.0 Hz); 4.1-4-4 (1H, multiplet); 5.72 (1H, doublet, J=2.0 Hz); 
8.00 (1H, singlet). 
EXAMPLE 2 
(5R,6S)-2-(2-Cyanometnyl-3,4,5,6-tetrahydropyrimidin-5-ylthio)-6-[1-(R)-hyd 
roxyethyl]penem-3-carboxylic acid 
Following the procedure of Example 1, the desired compound was obtained as 
a colourless powder from 30 mg of p-nitrobenzyl 
(5R,6S)-2-[1,3-bis-(p-nitrobenzyl-oxycarbonylamino)propan-2-ylthio]-6-[1-( 
R)-hydroxyethyl]penem-3-carboxylate and 25 mg of methyl cyanoacetoimidate. 
Infrared absorption spectrum .nu..sub.max (KBr) cm.sup.-1 : 3400, 2300, 
1760, 1660, 1600. 
EXAMPLE 3 
(5R,6S)-6-[1-(R)-Hydroxyethyl]-2-(2-methyl-3,4,5,6-tetrahydropyrimidin-5-yl 
thio)penem-3-carboxylic acid 
850 mg of p-nitrobenzyl 
(5R,6S)-2-[1,3-bis(p-nitrobenzyloxycarbonylamino)propan-2-ylthio]-6-[1-(R) 
-hydroxyethyl]penem-3-carboxylate were dissolved in 140 ml of 
tetrahydrofuran. To the resulting solution were added 140 ml of a 
phosphate buffer (pH 7.0) and 425 mg of platinum oxide. The mixture was 
stirred under a stream of hydrogen gas at room temperature for 3.5 hours. 
The catalyst was then filtered off under reduced pressure and the filtrate 
was concentrated to one-half of its original volume and washed twice with 
ethyl acetate. The aqueous solution was ice-cooled and adjusted to a pH 
value of 8.5 by the addition of a dilute aqueous solution of sodium 
hydroxide. 1.25 g of ethyl acetimidate hydrochloride were added and the 
resulting mixture was stirred under ice-cooling for 15 minutes, whilst the 
pH of the mixture was adjusted to a value of 8.5. The pH of the mixture 
was then adjusted to a value of 7.0 by the addition of dilute hydrochloric 
acid and the mixture was subjected to column chromatography through Diaion 
HP 20AG, eluted with 10% v/v aqueous acetone, to obtain 150 mg of the 
desired compound as a colourless powder. 
Ultraviolet absorption spectrum .lambda..sub.max (H.sub.2 O).sub.nm 
(.epsilon.): 257.9 (4920), 320.7 (6000). 
Infrared absorption spectrum .nu..sub.max (KBr)cm.sup.-1 : 3400, 1770, 
1660, 1590. 
Nuclear magnetic resonance spectrum (D.sub.2 O) .delta.ppm; 1.33 (3H, 
doublet, J=6.5 Hz); 2.24 (3H, singlet); 3.4-4.1 (6H,multiplet); 4.15-4.4 
(1H, multiplet); 5.76 (1H, doublet J=2.0 Hz). 
PREATION 1 
(3S,4R)-3-[1-(R)-t-butyldimethylsilyloxyethyl]-4-[[(1,3-bis(p-nitrobenzylox 
ycarbonylamino)propan-2-ylthio)thiocarbonyl]thio]azetidin-2-one 
5.3 g of 2-acetylthio-1,3-bis(p-nitrobenzyloxycarbonylamino)propane in a 
mixture of 161 ml of methanol and 40 ml of tetrahydrofuran were cooled to 
-20.degree. C. To the solution were added 9.95 ml of a methanolic solution 
of sodium methoxide containing 1 mM of sodium methoxide per 1 ml of 
methanol. The mixture was stirred at -10.degree. to -15.degree. C. for 30 
minutes, after which it was mixed with 0.961 ml of carbon disulphide and 
stirred at -20.degree. C. for 15 minutes. Then 20 ml of a methanolic 
solution containing 3.59 g of 
4-acetoxy-3-[1-(R)-t-butyldimethylsilyloxyethyl)-2-azetidinone was added 
to the above mixture and stirred at -20.degree. C. for 1 hour. The mixture 
was cooled to -50.degree. C. and then poured into a mixture of 20 ml of 
acetic acid and 200 ml of water. The mixture was extracted with ethyl 
acetate. The extract was washed with a saturated aqueous solution of 
sodium chloride and dried over anhydrous sodium sulphate. The solvent was 
distilled off and the residue was subjected to medium pressure column 
chromatography througn silica gel, eluted with 3:1-2:1 by volume mixtures 
of benzene and ethyl acetate, to give 6.1 g of the desired compound. 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm: 0.10 (6H, 
singlet); 0.90 (9H, singlet); 1.22 (3H, doublet, J=6.0 Hz); 3.1-3.8 (6H, 
multiplet); 4.1-4.5 (1H, multiplet); 5.21 (4H, singlet); 5.65 (1H, 
doublet, J=2.0 Hz); 5.98 (2H, broad singlet); 7.20 (1H, broad singlet); 
7.51, 8.19 (8H, A.sub.2 B.sub.2, J=9.0 Hz). 
PREATION 2 
p-Nitrobenzyl 
2-[(3S,4R)-3-1-(R)-t-butyldimethylsilyloxyethyl]-4-[[(1,3-bis(p-nitrobenzy 
loxycarbonylamino)propan-2-ylthio)thiocarbonyl]thio-2-oxo-1- 
azetidinyl]-2-hydroxyacetate 
A mixture of 6.1 g of 
(3S,4R)-3-[1-(R)-t-butyldimethylsilyloxyethyl]-4-[(1,3-bis(p-nitrobenzylox 
ycarbonylamino)propan-2-ylthio)thiocarbonyl]-thio)azetidin-2-one and 2.7 g 
of p-nitrobenzyl glyoxylate hydrate in 180 ml of benzene was heated under 
reflux for 2.5 hours. After completion of the reaction, the solvent was 
distilled off and the residue was subjected to medium pressure column 
chromatography through silica gel, eluted with a 1:1 by volume mixture of 
benzene and ethyl acetate, to give 6.2 g of the desired compound (a 
mixture of configuration isomers due to the hydroxy group) as an amorphous 
powder. 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm: 0.05 (3H, 
singlet); 0.08 (3H, singlet); 0.87 (9H, singlet); 1.20 (3H, doublet, J=6.0 
Hz); 3.3-3.8 (5H, multiplet); 4.1-4.5 (3H, multiplet); 4.8 (1H,broad 
singlet); 5.22-5.20 (6H, multiplet); 5.68 (1H, multiplet); 5.80 (2H, broad 
singlet); 7.51, 8.19 (12H, A.sub.2 B.sub.2, J=8.4 Hz). 
PREATION 3 
p-Nitrobenzyl 2-[(3S,4R)-3-[1-(R)-t-butyldimethylsilyloxyethyl]-4- 
[[(1,3-bis(p-nitrobenzyloxycarbonylamino)propan-2-ylthio)thiocarbonyl]thio 
]-2-oxo-1-azetidinyl]-2-(tri-phenylphosphoranylidene)acetate 
6.1 of p-nitrobenzyl 
2-[3S,4R)-3-[(R)-1-t-butyldimethylsilyloxyethyl]-4-[[(1,3-bis(p-nitrobenzy 
loxycarbonylamino)propan-2-ylthio) 
thiocarbonyl]thio]-2-oxo-1-azetidinyl]-2-hydroxyacetate were dissolved in 
80 ml of tetrahydrofuran. To this solution were added successively 0.795 
ml of 2,6-lutidine and 0.474 ml of thionyl chloride at -20.degree. C. The 
mixture was then stirred at the same temperature for 15 minutes. A further 
1.44 ml of 2,6-lutidine and 3.27 g of triphenylphosphine were added to the 
mixture. The resulting mixture was then gently heated under reflux in a 
stream of nitrogen gas for 48 hours. After completion of the reaction, the 
reaction mixture was concentrated by evaporation under reduced pressure 
and the residue was extracted with ethyl acetate. The extract was washed 
successively with water, an aqueous solution of sodium bicarbonate and a 
saturated aqueous solution of sodium chloride and dried over anhydrous 
sodium sulphate. The solvent was distilled off and the residue was 
subjected to medium pressure column chromatography through silica gel, 
eluted with 4:1-1:1 by volume mixtures of benzene and ethyl acetate, to 
obtain 2.7 g (35.4%) of the desired compound. 
Infrared absorption spectrum .nu..sub.max (CHCl.sub.3) cm.sup.-1 : 1755, 
1705. 
PREATION 4 
p-Nitrobenzyl 
(5R,6S)-6-[1-(R)-t-butyldimethylsilyoxyethyl]-2-[1,3-bis(p-nitrobenzyloxyc 
arbonylamino)propan-2-ylthio]penem-3-carboxylate and its (5S) isomer 
A solution of 2.7 g of p-nitrobenzyl 
2-[(3S,4R)-3-[1-(R)-t-butyldimethylsilyloxyethyl]-4-[[(1,3-bis(p-nitrobenz 
yloxycarbonylamino)propan-2-ylthio)thiocarbonyl]thio]-2-oxo-1-azetidinyl]-2 
-(triphenylphosphoranylidene)acetate and 65 mg of hydroquinone in 125 ml of 
xylene was heated under a stream of nitrogen gas at 130.degree. C. for 20 
hours. After completion of the reaction, the solvent was distilled off 
under reduced pressure and the residue was subjected to Lobar column 
chromatography through silica gel eluted with a 1:1 by volume mixture of 
benzene and ethyl acetate, to give 1.50 g of the desired (5R) isomer and 
0.54 g of the (5S) isomer, quantitatively. 
(5R) Isomer 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm: 0.06 (3H, 
singlet); 0.09 (3H, singlet); 0.83 (9H, singlet); 1.24 (3H, doublet, J=6.0 
Hz); 3.3-3.7 (5H, multiplet); 3.75 (1H, doubled doublet, J=3.4 and 1.5 
Hz); 4.1-4.4 (1H, multiplet); 5.18 (4H, singlet); 5.13, 5.38 (2H, 
AB-quartet, J=13.2 Hz); 5.65 (1H, doublet J=1.5 Hz); 5.7-6.05 (2H, broad 
singlet; 7.45, 8.12 (8H, A.sub.2 B.sub.2, J=8.7 Hz); 7.56, 8.12 (4H, 
A.sub.2 B.sub.2, J=8.7 Hz). 
(5S) Isomer 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm: 0.12 (6H, 
singlet); 0.86 (9H, singlet); 1.30 (3H, doublet, J=6.0 Hz); 3.38-3.68 (2H, 
multiplet); 3.95-4.40 (5H, multiplet); 5.15 (4H, singlet); 5.13, 5.41 (2H, 
AB-quartet, J=14.4 Hz); 5.65 (1H, doublet, J=3.6 Hz); 7.10 (2H, broad 
singlet); 7.43, 8.15 (8H, A.sub.2 B.sub.2, J=9.0 Hz); 7.55, 8.15 (4H, 
A.sub.2 B.sub.2, J=8.7 Hz). 
PREATION 5 
p-Nitrobenzyl 
(5R,6S)-6-[1-(R)-hydroxyethyl])-2-[1,3-bis-(p-nitrobenzyloxycarbonylamino) 
propan-2-ylthio]penem-3-carboxylate 
To a solution of 113 mg of p-nitrobenzyl 
(5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[1,3-bis(p-nitrobenzyloxy 
carbonylamino)propan-2-ylthio]penem-3-carboxylate in 2 ml of 
tetrahydrofuran were added 0.074 ml of acetic acid and 162 mg of 
tetrabutylammonium fluoride. The mixture was left to stand at 28.degree. 
C. for 16 hours and tnen diluted with ethyl acetate and washed 
successively with a saturated aqueous solution of sodium chloride, a 5% 
w/v aqueous solution of sodium bicarbonate and a saturated aqueous 
solution of sodium chloride. The solvent was distilled off and the residue 
was subjected to medium pressure column chromatography through silica gel, 
eluted with ethyl acetate, to give 91 mg (91.9%) of the desired compound. 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm; 1.30 (3H, 
doublet, J=6.0 Hz); 3.3-3.7 (6H, multiplet); 4.0-4.4 (1H, multiplet); 5.15 
(4H, singlet); 5.11, 5.37 (2H, AB-quartet, J=13.5 Hz); 5.61 (1H, doublet, 
J=1.5 Hz); 5.7-6.0 (2H, broad singlet); 7.42, 8.10 (8H, A.sub.2 B.sub.2, 
J=8.7 Hz); 7.52, 8.10 (4H, A.sub.2 B.sub.2, J=8.10 Hz). 
PREATION 6 
p-Nitrobenzyl 
(5S,6S)-6-[1-(R)-t-butyldimethyl-silyloxyethyl)-2-[1,3-bis(p-nitrobenzylox 
ycarbonylamino)-propan-2-ylthio]penem-3-carboxylate 
To a solution of 396 mg of triphenylphosphine in 6 ml of tetrahydrofuran 
were added 0.238 ml of diethyl azodicarboxylate, after which the mixture 
was stirred for 10 minutes. Meanwhile, 678 mg of, 
1,3-bis(p-nitrobenzyloxycarbonylamino)-2-hydroxypropane and 500 mg of 
p-nitrobenzyl 
(5S,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl)-2-thioxopenam-3-carboxylate 
were dissolved in 10 ml of tetrahydrofuran. The solution thus obtained was 
added dropwise to the mixture obtained above, whilst ice-cooling. The 
resulting mixture was stirred at the same temperature for 15 minutes and 
then at room temperature for 4 hours, after which it was extracted with 
ethyl acetate. The extract was washed with a saturated aqueous solution of 
sodium chloride and then dried over anhydrous sodium sulphate. The solvent 
was distilled off and the residue was subjected to medium pressure column 
chromatography through silica gel, eluted with a 2:1 by volume mixture of 
benzene and ethyl acetate, to give 246 mg (26.3%) of the desired compound. 
Nuclear Magnetic Resonance spectrum (CDCl.sub.3) .delta.ppm: 0.12 (6H, 
singlet); 0.86 (9H, singlet); 1.30 (3H, doublet, J=6.0 Hz); 3.38-3.68 (2H, 
multiplet); 3.95-4.40 (5H, multiplet); 5.15 (4H, singlet); 5.13, 5.41 (2H, 
AB-quartet, J=14.4 Hz); 5.65 (1H, doublet, J=3.6 Hz); 7.10 (2H, broad 
singlet); 7.43, 8.15 (8H, A.sub.2 B.sub.2, J=9.0 Hz); 7.55, 8.15 (4H, 
A.sub.2 B.sub.2, J=8.7 Hz).