WO1992020689A1

WO1992020689A1 - Antibacterial penem derivatives

Info

Publication number: WO1992020689A1
Application number: PCT/GB1992/000849
Authority: WO
Inventors: Neal Frederick Osborne
Original assignee: Smithkline Beecham P.L.C.
Priority date: 1991-05-15
Filing date: 1992-05-12
Publication date: 1992-11-26
Also published as: AU1740892A; GB9110507D0; PT100480A; ZA923458B; IE921546A1; MX9202250A

Abstract

Penem compounds of formula (I) or esters or pharmaceutically acceptable salts thereof, in which one of R?1, R2 or R3¿ is a heterocyclic group having up to 5 ring atoms, the remainder of R?1, R2 and R3¿ being hydrogen, optionally substituted alkyl or halogen; R4 is C¿1-6?alkyl; R?5¿ is hydrogen or a hydroxy-protecting group; R6 is hydrogen or a salt-forming cation or ester-forming group. The compounds are useful as antibacterial agents.

Description

ANTIBACTERIAL PENEM DERIVATIVES

This invention relates to novel chemical compounds, in particular to 2-heterocyclylvinyl-5-hyclroxyalkyl substituted penems, and derivatives thereof, having antibacterial properties. The invention also relates to methods for the preparation of such compounds, to pharmaceutical compositions containing them, and to uses thereof.

Compounds of this general type are disclosed in GB 2206113A

(Farmitalia), EP 0275002A (Hoechst), EP 0070204A and JP 59046289A (both Sumitomo). In the latter two, penems of formula:

wherein X is hydrogen or methyl and the 6-membered N-heterocyclyl ring is piperidine or tetrahydropyridine are disclosed.

According to the present invention, novel penems of formula I are provided:

or an ester or pharmaceutically acceptable salt thereof in which: one of R¹, R² or R³ is an unsubstituted or substituted heterocyclic group containing up to 5 ring atoms, at least one of which is selected from N, S or O, the remainder of R¹, R² and R³ being independently selected from H, optionally substituted C_1-6 alkyl or halogen,

R⁴ is C_1-6 alkyl,

R₅ is H or a hydroxy-protecting group,

R⁶ is H, or salt-forming cation or an ester-forming group.

The heterocyclic group denoted by R¹, R² or R³ may be saturated or unsaturated, aliphatic or aromatic, monocyclic or fused bicyclic connected to the vinyl system by a ring carbon and may contain 3, 4 or 5 ring atoms. The heterocyclic group may contain a single heteroatom, and when there is more than one heteroatom in the ring the heteroatoms may all be of one type, e.g. 2, 3 or 4 N, S or O atoms in a ring, or there may be two different types of heteroatom, e.g. 1 or more N atoms together with 1 or more S or O atoms in a ring.

Suitable 5-membered heterocyclic groups include all isomeric forms of pyrrolyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, pyrrolidinyl, thienyl, thiolanyl, thiolenyl, dithiolyl, furyl, dihyctrofuranyl, tetrahydrofuranyl, thiazolyl, isothiazolyl, thiadiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, and partly or wholly reduced (where appropriate) forms of these.

Suitable 4-membered heterocyclic groups include all isomeric forms of azetidinyl, azetidonyl, diazetidinyl, thietanyl, and oxetanyl.

Suitable 3-membered heterocyclic groups include all isomeric forms of thiiranyl, aziridinyl and oxiranyl.

When the heterocyclic group denoted by R¹, R² or R³ is substituted, substituents may be carried on a ring carbon or on a ring nitrogen atom when present. Ring sulphur atoms may be present as sulphoxide or sulphone groups.

Examples of suitable substituents which may be present on the

heterocyclic ring R¹, R² or R³ include (C_1-5)alkanoyl, (C_1-5)alkanoyloxy, heterocyclyl, amino, sulphonylamino (ie - NHSO₂R where ϊ. is alkyl or aryl), (C_1-6)alkanoylamino, (mono or di)-(C_1-6)alkylamino, hydroxy, (C_1- ₆)alkoxy, sulpho, mercapto, (C_1-6)alkylthio, (C_1-6)alkylsulphinyl, (C_1- ₆)alkyl-sulphonyl, heterocyclylthio, arylthio, sulphamoyl, carbamoyl, amidino, guanidino, nitro, halogen, carboxy, carboxy salts, carboxy esters, arylcarbonyl, and heterocyclylcarbonyl and carbonyloxy groups, and also unsubstituted or substituted (C_1-6)alkyl, (C_2-6)alkenyl, (C_2-6) alkynyl, aryl, and aryl(C_1-6)alkyl groups. Examples of suitable optional substituents for the above-mentioned (C_1- g.alkyl, (C_2-6)alkenyl, (C_2-6)alkynyl, aryl and aryl(C_1-6)alkyl (i.e.

"hydrocarbon") substitutents include (C_1-6)alkanoyl, (C_1-6)alkanoyloxy, heterocyclyl, amino, sulphonylamino, (C_1-6)alkanoylamino, (mono or di)-(C_1-6)alkylamino, hydroxy, (C_1-6)alkylsulphinyl, (C_1- ₆)alkylsulphonyl, heterocyclylthio, arylthio, sulphamoyl, carbamoyl, amidino, guanidino, nitro, halogen, carboxy, carboxy salts, carboxy esters,arylcarbonyl and heterocyclylcarbonyl and carbonyloxy groups.

When the heterocyclic group R¹, R² or R³ includes a carboxy salt or carboxy ester substituent, that substituent is suitably a pharmaceutically acceptable salt or pharmaceutically acceptable ester.

The term 'heterocyclyl' as used herein with reference to substituents includes aromatic and non-aromatic, single and fused, rings containing up to 7 suitably 4-6 atoms in each ring and containing up to four

hetero-atoms in each ring selected from oxygen, nitrogen and sulphur, which rings may be unsubstituted or substituted by up to three groups selected from halogen, (C_1-6)alkyl, (C_1-6)alkoxy, halo(C_1-6)alkyl, hydroxy, amino, carboxy, (C_1-6)alkoxycarbonyl, (C_1-6)alkoxycarbonyl(C_1- ₆ )alkyl, aryl, (C_1-6)alkylthio, arylthio, mercapto and oxo groups.

Examples of suitable heterocyclyl substituent groups on the heterocyclic group denoted by R¹, R² or R³ include the above-mentioned 4- and 5- membered heterocyclic groups and the 6-membered heterocyclyl groups pyridyl, pyrimidyl, pyridazinyl, triazinyl, thiapyranyl, pyranyl, dioxanyl, morpholinyl and reduced forms of these.

The term 'aryl' as used herein includes phenyl and naphthyl, which may be unsubstituted or substituted by up to five, preferably up to three, groups selected from halogen, (C_1-6)alkyl, phenyl, (C_1-6)alkoxy, halo(C_1- ₆)alkyl, hydroxy, amino, nitro, carboxy, (C_1-6)alkoxycarbonyl, (C_1- ₆)alkoxycarbonyl(C_1-6)alkyl, (C_1-6)alkylcarbonyloxy, (C_1-6)alkylcarbonyl (C_1-6)alkylthio, arylthio, and mercapto groups. Suitable heterocyclic groups for R¹, R² and R³ include triazolyl, furyl, thienyl, thiazolyl, isothiazolyl, and pyrazolyl, which may be substituted, for example by C_1-6 alkyl. Examples of such heterocyclic groups are 1,2,3- triazol-4-yl, 2-furyl, 2-thisnyl, isothiazol-5-yl, thiazol-5-yl and pyrazol-4- yl.

Suitably those of R¹, R² and R³ which are not the heterocyclic group are selected from H, methyl or halogen.

A suitable halogen for R¹, R² or R³ is chlorine.

R⁴ is preferably methyl.

R⁵ is preferably H, or when R⁵ is a hydroxy-protecting group it may be a conventional protecting group such as an alkanoic ester group such as a C_1-4 alkoxy carbonyl group such as tert-butyloxycarbonyl. a C_1-4

halogenoalkoxycarbonyl group such as 2-iodoethyloxycarbonyl or 2,2,2- trichloro- ethyloxycarbonyl, an aralkyloxycarbonyl group such as

benzyloxycarbonyl, a tri(C_1-4)alkylsilyl group such as tert-butyldimethylsilyl or trimethylsilyl, a C_4-10 tert-alkyl group such as tert-butyl and a substituted or unsubstituted mono-, di or tri-phenylmethyl group such as benzyl, p-methoxybenzyl, diphenylmethyl, di(p-anisyl)methyl or trityl.

The compound of formula I, its salts and esters, may exist in a number of isomeric forms, all of which, including racemic and diastereoisomeric forms are encompassed within the scope of the present invention. A preferred isomeric form is the (5R, 6S) form, having position 8 in the (R) configuration. The orientation of the 2-position vinyl side chain having one of R¹, R² or R³ or a heterocyclic group may be E or Z and the present invention includes both such forms or mixtures of these isomers in a 1:1 ratio or in which one such isomer predominates, although an isomerically pure compound is preferred.

Suitable pharmaceutically acceptable salts of the 3-carboxylic acid group of the compound of formula I or of other carboxylic acid groups which may be present as optional substituents include those in which R⁶ is a metal ion e.g. aluminium salts, alkali metal salts (e.g. sodium, lithium or potassium salts), alkaline earth metal salts (e.g. calcium or magnesium salts), ammonium salts, and substituted ammonium salts, for example those with lower alkylamines (e.g.triethylamine), hydroxy-lower alkylamines (e.g. 2-hydroxyethylamine), di(2-hydroxyethyl)amine tri(2-hydroxyethyl)amine), bis-(2-hydroxyethyl)amine, tris-(2-hydroxyethyl)amine, lower-alkylamines (e.g. dicyclohexyl- amine), or with procaine, dibenzylamine, N,N-dibenzyl- ethylenediamine, 1-ephenamine, N-methylmorpholine, N-ethylpiperidine, N-benzyl-β-phenethylamine, dehydroabietylamine, ethylenediamine,

N,N'-bishydroabietylethylenediamine, bases of the pyridine type (e.g. pyridine, collidine and quinoline), and other amines which have been or can be used to form quaternary ammonium salts with penicillins.

Pharmaceutically acceptable salts may also be acid addition salts of any amino or substituted amino group(s) that may be present as optional substituents on the compound of formula I, or of any heterocyclic group ring nitrogen atoms. Suitable salts include for example hy drochlorides, sulphates, acetates, phosphates etc. and other pharmaceutically

acceptable salts will be apparent to those skilled in the art. Preferred addition salts are the hydrochlorides.

When R⁶ is an ester-forming group the compound of formula I may be a pharmaceutically acceptable in vivo hydrolysable ester, being an ester which hydrolyses in the human body to produce the parent acid or its salt. Such esters may be identified by the test process of oral or intravenous administration to a test animal, and subsequent examination of the test animal's body fluids for the presence of the compound of the formula I or a salt thereof.

In some cases, the in vivo hydrolysable ester moiety may constitute a link between two different active ingredient moieties, one of which is a compound according to the invention and the other of which may be another therapeutically active compound, such that on in vivo hydrolysis of the ester moiety, the ester link breaks to give the two separate active compounds. The linked entity may be referred to as a 'mutual pro-drug'.

Examples of suitable pharmaceutically acceptable in vivo hydrolysable ester groups include those which break down readily in the human body to leave the parent acid or its salt. Suitable ester groups of this type include those in which R⁶ has the formula (i), (ii), (iii) or (iv):

wherein R^a is hydrogen, C_1-6 alkyl, C_3-7 cycloalkyl, methyl, or phenyl, R^b is C_1-6 alkyl, C_1-6 alkoxy, phenyl, benzyl, C_3-7 cycloalkyl, C_1-6 alkyl C_3- ₇ cycloalkyl, 1-amino C_1-6 alkyl, or 1-(C_1-6 alkyl)amino C_1-6 alkyl; or R^a and R^b together form a 1,2-phenylene group optionally substituted by one or two methoxy phenyl, benzyl, C_3-7 cycloalkyl, C_1-6 alkyl C3.7

cycloalkyl, 1-amino C_1-6 alkyl, or 1-(C_1-6 alkyl)amino C_1-6 alkyl; or R^a and R^b together form a 1,2-phenylene group optionally substituted by one or two methoxy groups; R^c represents C_1-6 alkylene optionally substituted with a methyl or ethyl group and R^d and R^e independently represent C_1-6 alkyl; R^f represents C_1-6 alkyl; R^g represents hydrogen or phenyl optionally substituted by up to three groups selected from halogen, C_1-6 alkyl, or C_1-6 alkoxy; and Q is oxygen or NH.

Examples of suitable in vivo hydrolysable ester groups include, for example, acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, α-acetoxyethyl, α-pivaloyloxyethyl, 1-(cyclohexylcarbonyloxy)prop-1-yl, and (1-aminoethyl)carbonyloxymethyl; alkoxycarbonyloxyalkyl groups, such as ethoxycarbonyloxymethyl and α-ethoxycarbonyloxyethyl;

dialkylaminoalkyl especially di-loweralkylamino alkyl groups such as dimethylaminomethyl, dimethylaminoethyl, diethylaminomethyl or diethylaminoethyl; lactone groups such as phthalidyl and

dimethoxyphthalidyl; and esters linked to a second β-lactam antibiotic or to a β-lactamase inhibitor.

A further suitable pharmaceutically acceptable in vivo hydrolysable ester group is that in which R⁶ has the formula:

wherein R¹⁰ is hydrogen, C_1-6 alkyl or phenyl.

R⁶ may also be a readily removeable carboxy protecting ester group, other than a pharmaceutically acceptable in vivo hydrolysable ester group, or a non-pharmaceutically acceptable salt-forming cation. Such compounds of formula I are primarily useful as intermediates in the preparation of compounds of formula I and pharmaceutically acceptable salts and esters thereof.

Suitable ester-forming carboxyl-protecting groups from which R⁶ may be selected include those which may be removed under conventional conditions. Such groups for R⁶ include benzyl, p-methoxybenzyl, benzoylmethyl, p-nitrobenzyl, 4-pyridylmethyl, 2,2,2-tιichloroethyl, 2,2,2-tribromoethyl, t-butyl, t-amyl, allyl, diphenylmethyl,

triphenylmethyl, adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl, tetrahydrofur-2-yl, tetrahydropyran-2-yl, pentachlorophenyl, acetonyl, p-toluenesulphonylethyl, methoxymethyl, a silyl, stannyl or phosphorus-containing group, an oxime radical of formula -N=CHR⁹ where R⁹ is aryl or heterocyclyl.

A CO₂R⁶ group in which R⁶ is hydrogen may be regenerated from any of the above-mentioned esters by usual methods appropriate to the

particular R⁶ group, for example, acld- and base- catalysed hydrolysis, or by enzymically-catalysed hydrolysis, or by hydrogenolysis under

conditions wherein the remainder of the molecule is substantially unaffected. It will be appreclated that also included within the scope of the invention are salts and carboxy-protected derivatives, including in vivo hydrolysable esters, of any carboxy groups that may be present as optional substituents in compounds of formula I.

Certain compounds of formula I may include an amino group which may be protected. Suitable amino protecting groups are those well known in the art which may be removed under conventional conditions if required without disruption of the remainder of the molecule.

Examples of amino protecting groups include C_1-6 alkanoyl; benzoyl; benzyl optionally substituted in the phenyl ring by one or two substituents selected from C_1-4 alkyl, C_1-4 alkoxy, trifluoromethyl, halogen, or nitro; C_1-4 alkoxycarbonyl; benzyloxycarbonyl or trityl substituted as for benzyl above; allyloxycarbonyl, trichloroethoxycarbonyl or chloroacetyl.

From the foregoing it will be seen that one preferred subclass of

compounds of formula I is that of formula IA or pharmaceutically acceptable salts or pharmaceutically acceptable in vivo hydrolysable esters thereof:

wherein R¹, R² and R³ are as defined in formula I, with R⁶ being H, or R⁶ being a pharmaceutically acceptable salt cation or in vivo hydrolysable ester forming group.

Some compounds of formula I and IA may be crystallised or recrystallised from solvents such as organic solvents. In such cases solvates may be formed. This invention includes within its scope stoichiometric solvates including hydrates as well as compounds containing variable amounts of solvents such as water that may be produced by processes such as lyophilisation. Since the compounds of formula I and IA are antibiotics and are intended for use in pharmaceutical compositions it will readily be understood that they are preferably each provided in substantially pure form, for example at least 60% pure, more suitably at least 75% pure and preferably at least 85% pure, especially at least 95% pure particularly at least 98% pure (% are on a weight for weight basis). Impure preparations of the compounds may be used for preparing the more pure forms used in the

pharmaceutical compositions; these less pure preparations of the compounds should contain at least 1%, more suitably at least 5% and preferably from 10 to 59% of a compound of the formula I or IA or ester or salt thereof.

Accordingly, specific compounds of formula I include the following acids, and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof:

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(1-methyl-1,2,3-triazol-4- yl)ethenyl]penem-3-carboxylic acid.

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(4-methylthiazol-5-yl)ethenyl]penem- 3-carboxylic acid.

(5R,6S)-2-[2-(2-furyl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylic acid. (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(isothiazol-5yl)-ethenyl]penem-3-carboxylic acid.

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)ethenyl]-penem-3-carboxylic acid. (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-methylpyrazol-4-yl)ethenyl]penem-3- carboxylic acid.

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E)-1-(1-methyl-1,2,3-triazol-4-yl)prop-1- en-2-yl]penem-3-carboxylic acid.

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)-prop-1-en-1-yl]penem-3- carboxylic acid. (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(2-thienyl)prop-1-en-1-yl]penem-3- carboxylic acid.

(5R,6S)-2-[1-(Z)-chloro-2-(2-thienyl)ethenyl]-6-[1-(R)hydroxyethyl]penem- 3-carboxylic acid. (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(tetrahydrofuran-2-yl)ethenyl]penem- 3-carboxylic acid (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(isoxazol-3-yl)prop-1-en-1-yl]penem-3- carboxylic acid (5R,6S) 6-[1-(R)-hydroxyethyl]-2-[1-(2-methylthiazol-4-yl)prop-1-en-1-ylpenem-3-carboxylic acid (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(thiazol-2-yl)prop-1-en-1-yl]penem-3-carboxylic acid (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(5-methylisoxazol-3-yl)prop-1-en-1-yl]penem-3-carboxylic acid (5R,6S) 2-[2-(2-furyl)prop-1-en-1-yl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylic acid (5R,6S) 2-[1-chloro-2-(1-methyl-1,2,3-triazol-4-yl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylic acid (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E-2-(1,2,3-thiadizaol-4- yl)ethenyl]penem-3-carboxylic acid

The present invention provides a first process for the preparation of a compound of formula I as defined above, from a compound of formula IB:

wherein R¹, R², R³ and R⁴ are as defined in formula I, wherein either R⁷ is a group R⁵ and R⁸ is a carboxy-protecting group or R⁸ is a group R⁶ and R⁷ is a hydroxy-protecting group, which process comprises removing protecting groups R⁷ and/or R⁸ and replacing them respectively with groups R⁵ and/or R⁶ which are different to protecting groups R⁷ and R⁸; and thereafter if necessary or desired, carrying out one or more of the following steps:

(i) removing any further protecting groups,

(ii) converting the group CO₂R⁶ into a different group CO₂R⁶,

(iii) converting the group OR⁵ into a different group OR⁵.

(iv) converting the compound into a pharmaceutically acceptable salt or ester.

Suitable hydroxy-protecting groups R⁷ are those mentioned above with respect to R⁵, a particular group R⁷ being t-butyldimethylsilyl. Suitable (carboxy-protecting group R⁸ are those mentioned above with respect to R⁶, particular groups R⁸ being p-nitrobenzyl and p-methoxybenzyl (abbreviated respectively herein to "pNB" and "pMB"). Such protecting groups can be removed by any one of the procedures conventionally employed for deprotection of a protecting group of carboxylic acids or alcohols as appropriate. For example, the deprotection of OR⁷ can be accomplished by treatment of the penem compound of formula IB with tetrabutylammoniumfluoride, this being preferred when R⁷ is t-butyldimethylsilyl. Deprotection of CO₂R⁸ when R⁸ is pNB for example can be achieved by a reduction method such as catalytic hydrogenation. The catalytic hydrogenation can be performed by reacting the compound IB with H₂ in the presence of a catalyst such as Pd-C

(palladium on carbon) or PtO (platinum oxide) in an inert solvent such as an alcohol (e.g. ethanol), an ether (e.g. tetrahydrofuran or dioxan), an aliphatic acid (e.g. acetic acid), an aqueous liquid (e.g. water alone or aqueous phosphate buffer) or a mixture thereof. The hydrogenation can be conducted under atmospheric pressure or pressurized conditions and at a temperature ranging around ambient, e.g. 0°C - 50°C. Deprotection of CO₂R⁸ when R⁸ is pMB can be achieved by treatment with a Lewis Acid such as aluminium chloride. The invention also provides a second process for the preparation of a compound of formula I in which a compound of formula II:

is reacted with a compound of formula (III):

wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as defined with respect to formula I, Y is oxygen or sulphur and X is a group or atom which together with the group or atom Y may be eliminated as XY, to form a compound of formula I by elimination of XY; and thereafter if necessary or desired, carrying out one or more of the following steps:

(i) removing any protecting groups,

(ii) converting the group CO₂R⁶ into a different group CO₂R⁶,

(iii) converting the group OR⁵ into a different group OR⁵, (iv) converting the product into a pharmaceutically acceptable salt or ester.

Compounds of formula (II) may be prepared by reaction of compounds of formula (IIA):

where X is as-defined in formula (II), and Z- is a counter anion such as halide, e.g. chloride or iodide, with a base such as sodium carbonate or a tertiary amine base such as diisopropylethylamine. When compounds of formula (II) are prepared in this way it may not be necessary to isolate then and they may be used in situ in a single step process. Preferably X in formula II is a phosphorane group of the general formula PR₃ where R is an organic group especially aryl such as phenyl, or alkoxy.

In such a case the group X⁺ in formula IIA will be a phosphonium cation which can be combined with a suitable counter-anion Z- which may be a simple inorganic anion such as halide, for example iodide. Y is preferably oxygen, so that in the preferred case the reaction of the compounds of formulae II and III proceeeds via a Wittig type reaction to form the side chain ethenyl group with elimination of OPR₃. The Wittig reaction is well known and suitable conditions for the above process will be apparent to those skilled in the art, as will other alternative processes for the introduction of the ethenyl side group.

Compounds of formula IIA ay be prepared from corresponding known (J.

Antibiot., 36,938, (1983)) compounds such as the corresponding

2-hydroxymethyl penems in which X is OH, for example, by firstly replacement of the OH group with a halogen, especially Cl, using

conventional procedures such as treatment with SOCI₂, PCI₃ etc. in the presence of a base, followed by treatment of the halide with PR₃.

Compounds of formula III are known compounds. An overall reaction scheme for this second process is shown as Route A in which "R" is the heterocyclic group denoted by R¹, R² or R³ in formula I above. Although shown for specific groups R¹, R², R³, R⁴, R⁵, and R⁶ it will be understood that Route A is of general applicability. If in this process it is necessary to remove protecting groups such as R⁵ and/or R⁶ they may be removed by conventional procedures as discussed above.

The invention also provides a third process for the preparation of a compound of formula I, in which an azetidinone compound of formula IV:

(IV) is cyclised, wherein;

R¹, R², R³, R⁴, R⁵ and R⁶ are as defined with respect to formula I;

R⁹ denotes an O or S atom or a group PR₃ (where R is as defined above),

R¹⁰ denotes a phosphoranylidene group (e.g. a triarylphosphoranylidene group or a trialkoxyphosphoranylidene group), =C(CH₃)₂, or O; and thereafter if necessary or desired carrying out one or more of the following steps:

(i) removing any protecting groups, (ii) converting the group CO₂R⁶ into a different group CO₂R⁶,

(iii) converting the group OR⁵ into a different group OR⁵,

(iv) converting the product into a pharmaceutically acceptable salt or ester.

Preferably R⁹ is O or S, and R¹⁰ is a triarylphosphoranylidene group such as PPh₃, or O, so that cyclisation can take place via a Wittig type reaction.

The cyclisation may then be carried out in a generally known manner, for example in an oiganic solvent, optionally in the presence of a trivalent phosphorus compoτmd (especially when R¹⁰ is O). General methods by which cyclisation can be carried out are described in EP 0232966, with reference to Routes A to F on page 13-25 thereof. For example when R⁹ is O and R¹⁰ is a phosphoranylidene group cyclisation may occur spontaneously or on heating, e.g. at around 100°C under reflux preferably in an inert atmosphere such as argon.

Compounds of formula IV for example may be prepared by reaction of a compound of formula V: wherein R⁴, R⁵, R⁶ and R¹⁰ are as defined with respect to formula IV, M denotes a metal atom or ion of valency or ionic charge q with an acid of formula VI or an acylating derivative thereof:

wherein R¹, R² and R³ are as defined with respect to formula I.

Suitable metals M are Ag or Hg, preferably Ag.

Acids of formula (VI) are known and may be prepared from literature methods.

Suitable acylating derivatives of the acid of formula (VI) include, an acid halide, preferably the acid chloride or bromide. Acylation with an acid halide may be effected in the presence of an acid binding agent for example, tertiary amine (such as pyridine or dimethylaniline), molecular sieves, an inorganic base (such as calcium carbonate or sodium

bicarbonate) or an oxirane. The oxirane is preferably a (C_1-6)- 1,2-alkylene oxide - such as ethylene oxide or propylene oxide. The acylation reaction using an acid halide may be carried out at a

temperature in the range -50°C to +50°C, preferably -20°C to +20°c, in aqueous or non-aqueous media such as water, acetone, tetrahydrofuran, ethyl acetate, dimethylacetamide, dimethylformamide, acetonitrile, dichloromethane, 1,2-dichloroethane, or mixtures thereof. Alternatively, the reaction may be carried out in an unstable emulsion of

water-immiscible solvent, especially an aliphatic ester or ketone, such as methyl isobutyl ketone or butyl acetate.

The acid halide may be prepared by reacting the acid (VI) or a salt or a reactive derivative thereof with a halogenating (eg chlorinating or brominating) agent such as phosphorus pentachloride, thionyl chloride, oxalyl chloride or phosgene.

Alternatively, the N-acylating derivative of the acid (VI) may be a symmetrical or mixed anhydride. Suitable mixed anhydrides are anhydrides with, for example, carbonic acid monoesters, trimethyl acetic acid, thioacetic acid, diphenylacetic acid, benzoic acid, phosphorus acids (such as phosphoric, phosphorous, and phosphinic acids) or aromatic or aliphatic sulphonic acids (such as p-toluenes ulphonic acid or

methanesulphonic acid). When a symmetrical or mixed anhydride is employed, the reaction maybe carried out in the presence of a weak base such as pyridine or 2,6-lutidine as catalyst.

Alternative acylating derivatives of acid (VI) are the acid azide, or activated esters such as esters with 2-mercaptopyridine, cyanomethanol, p-nitrophenol, 2,4-dinitrophenol, thinhenol, halophenols, including pentachlorophenol, monomethoxyphe. ol, N-hydroxy succinimide,

N-hydroxybenzotiiazole, or 8-hydroxyquinoline; or amides such as

N-acylsaccharins, N-acylthiazolidin-2-thione or N-acylphthalimides; or an alkylidene iminoester prepared by reaction of the acid (VI) with an oxime. Other reactive acylating derivatives of the acid (VI) include the reactive intermediates formed by reaction in situ with a condensing agent such as a carbodiimide, for example, N,N'-diethyl-, dipropyl- or diisopropylcarbodiimide, N,N'-di-cyciohexylcarbodiimide, or N-ethyl- N'-[3-(dimethylamino)propyl]-carbodiimide; a suitable carbonyl compound, for example, N,N'-carbonyldiimidazole or N,N'--carbonylditriazole; an isoxazolinium salt, for example, N-ethyl-

5-phenylisexazolinium-3-sulphonate or N-t-butyl-5- methylisoxazohnium perchlorate; or an N-alkoxycarbonyl 2-alkoxy-1,2-dihydroquinoline, such as N-ethoxycarbonyl 2-ethoxy-1,2-dihydroquinoline, or a phosphoric acid condensing agent such as diethylphosphoryl- cyanide. Other suitable derivatives will be apparent to those skilled in the art. The condensation reaction is preferably carried out in an organic reaction medium, for example, methylene chloride, dimethylformamide, acetonitrile, ethanol, benzene, dioxan or tetrahydrofiiran.

A further method of forming the acylating derivative of the acid of formula (VI) is to treat the acid of formula (VI) with a solution or suspension preformed by addition of a carbonyl halide, preferably oxalyl chloride, or a phosphoryl halide such as phosphorus oxychloride, to a halogenated hydrocarbon solvent, preferably dichloromethane, containing a lower acyl tertiary amide, preferably N,N-dimethyl- formamide. The acylating derivative of the acid of formula (VI) so derived may then be caused to react with a compound of formula (V). The acylation reaction may conveniently be carried out at -40° to +30°C, if desired in the presence of an acid binding agent. A catalyst such as 4-dimethylamino- pyridine may optionally also be added. Preferred solvents for the above acylation reaction are dichloromethane, and acetonitrile.

Compounds of formula (V) may be prepared from compounds of formula (VII).

by reaction with a metal salt. This reaction is generally known, see for example EP 0232966A Route A page 21 and example 3 thereof, or EP 015132A preparation 1(e). Compounds of formula (VII) may be prepared from compounds of formula (VIII)

by reaction sequentially with (a) (OH)₂CHCO₂R⁶ (i.e glyoxylic acid with its carboxylic acid function protected by a protecting group R⁶, (b) SOCI₂ in the presence of a base, (c) PPh₃ in the presence of a base. This reaction is generally known, see for example EP 0232966 Route A page 21, or EP 0154132 preparation 1(d).

Compounds of formula (VIII) may be prepared from known starting compounds of formula (IX).

by reaction with NaSCPh₃, which can be prepared by reaction betweeen NaH and HS.CPh₃. The reaction between (VIII and NaSCPh₃ may be carried out by mixing in an organic solvent, suitably methanol. As the NaSCPh₃ may also be prepared in methanol by the above mentioned reaction it may be used in situ. Both reactions are conveniently carried out at around 0°C, preferably under an inert atmosphere.

An overall reaction scheme for this third process is shown as Route B. Although shown for specific groups R⁴, R⁵, R⁶, R⁹, R¹⁰ and R¹¹ it will be understood that Route B is of general applicability and in particular other protecting groups may be used. Also, although 2 routes are shown in Route B for the preparation of acids and acylating derivatives of formula (VI) it will be understood that alternative routes to compounds of formula (VI) may be used and will be apparent to those skilled in the art.

The intermediate compounds of formula (II) where X is a phosphorane salt, ie where X is =PR₃, and of formula (IIA) when X⁺ is a phosphonium salt PR⁺ ₃, and formula (IV), are believed to be novel compounds, and as such are a further aspect of the present invention.

In the reaction schemes of Routes A and B the abbreviations Me = methyl, Bu^t - tertiarybutyl, Ac = acetyl, Ph = phenyl, pNB = para-nitrobenzyl, pMB = para-methoxybenzyl are used.

The present invention also provides a pharmaceutical composition which comprises a compound of formula I, particularly IA or a pharmaceutically acceptable salt or in _vivo hydrolysable ester thereof and a

pharmaceutically acceptable carrier. The compositions of the invention include those in a form adapted for oral, topical or parenteral use and may be used for the treatment of bacterial infection in mammals including humans.

The antibiotic compounds according to the invention may be formulated for administration in any convenient way for use in human or veterinary medicine, by analogy with other antibiotics.

The composition may be formulated for administration by any route, such as oral, topical or parenteral. The compositions may be in the form of tablets, capsules, powders, granules, lozenges, creams or liquid

preparations, such as oral or sterile parenteral solutions or suspensions.

The topical formulations of the present invention may be presented as, for instance, ointments, creams or lotions, eye ointments and eye or ear drops, impregnated dressings and aerosols, and may contain appropriate conventional additives such as preservatives, solvents to assist drug penetration and emollients in ointments and creams.

The formulations may also contain compatible conventional carriers, such as cream or ointment bases and ethanol or oleyl alcohol for lotions. Such carriers may be present as from about 1% up to about 98% of the formulation. More usually they will form up to about 80% of the formulation. 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 polyvinylpyrollidone; fillers, for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine; tabletting lubricants, for example magnesium stearate, talc, polyethylene glycol or 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 normal pharmaceutical practice. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives, such as suspending agents, for example sorbitol, methyl cellulose, glucose syrup, gelatin, hydroxyethyl cellulose, carboxymethyl cellulose, aluminium stearate gel or

hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia; non-aqueous vehicles (which may include edible oils), for example almond oil, oily esters such as glycerine, propylene glycol, or ethyl alcohol; preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and, if desired, conventional flavouring or colouring agents.

Suppositories will contain conventional suppository bases, e.g.

cocoa-butter or other glyceride. For parenteral administration, fluid unit dosage forms are prepared utilizing the compound and a sterile vehicle, water being preferred. The compound, depending on the vehicle and concentration used, can be either suspended or dissolved in the vehicle. In preparing solutions the compound can be dissolved in water for injection and filter sterilised before filling into a suitable vial or ampoule and sealing.

Advantageously, agents such as a local anaesthetic, preservative and buffering agents can be dissolved in the vehicle. To enhance the stability, the composition can be frozen after filling into the vial and the water removed under vacuum. The dry lyophilized powder is then sealed in the vial and an accompanying vial of water for injection may be supplied to reconstitute the liquid prior to use. Parenteral suspensions are prepared in substantially the same manner except that the compound is suspended in the vehicle instead of being dissolved and sterilization cannot be accomplished by filtration. The compound can be sterilised by exposure to ethylene oxide before suspending in the sterile vehicle. Advantageously, a surfactant or wetting agent is included in the composition to facilitate uniform distribution of the compound. The compositions may contain from 0.1% by weight, preferably from

10-60% by weight, of the active material, depending on the method of administration. Where the compositions comprise dosage units, each unit will preferably contain from 50-500 mg of the active ingredient. The dosage as employed for adult human treatment will preferably range from 100 to 3000 mg per day, for instance 1500 mg per day depending on the route and frequency of administration. Such a dosage corresponds to 1.5 to 50 mg/kg per day. Suitably the dosage is from 5 to 20 mg/kg per day.

No lexicological effects are indicated when a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof is administered in the above-mentioned dosage range.

The compound of formula (I) may be the sole therapeutic agent in the compositions of the invention or a combination with other antibiotics or with a β-lactamase inhibitor may be employed. Advantageously, the compositions also comprise a compound of formula (X) or a pharmaceutically acceptable salt or ester thereof:

wherein

A is hydroxyl, substituted hydroxyl, thiol, substituted thiol, amino, mono- or di-hydrocarbyl-substituted amino, or mono- or di-acylamino; an optionally substituted triazolyl group; or an optionally substituted tetrazolyl group as described in EP O 053 893.

A further advantageous composition comprises an antibiotic compound of formula I or IA according to the invention and a pharmaceutically acceptable carrier or excipient together with a β-lactamase inhibitor of formula (XI) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof:

wherein B is hydrogen, halogen (especially chlorine) or a group of formula:

in which R¹² and R¹³ are the same or different and each is hydrogen, C_1-6 alkoxycarbonyl, or carboxy or a pharmaceutically acceptable salt thereof.

Further suitable β-lactamase inhibitors include 6-alkylidene penems of formula XII below:

or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, wherein R¹⁴ and R¹⁵ are the same or different and each represents hydrogen, or a C_1-10 hydrocarbon or heterocyclic group optionally substituted with a functional group; and R¹⁶ represents hydrogen or a group of formula R^a or -SR^a where R^a is an optionally substituted C_1-10 hydrocarbon or heterocyclic group, as described in EP 041 768A.

Further suitable β-lactamase inhibitors include 6β-bromopenicillanic acid and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof and 6β-iodopenicillanic acid and pharmaceutically acceptable salts and in vivo hydrolysable esters thereof described in, for example, EP-A-0 410 768 and EP-A-0 154 132 (both Beecham Group).

Such compositions of this invention which include a β-lactamase inhibitory amount of a β-lactamase inhibitor are formulated in a conventional manner using techniques and procedures per se known in the art.

The present invention provides a compound of formula (I) or a

pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use as a therapeutic agent.

The present invention further provides a compound of formula (I) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use in the treatment of bacterial infections.

The present invention also includes a method of treating bacterial infections in humans and animals which comprises the administration of a therapeutically effective amount of an antibiotic compound of this invention of the formula (I) or a pharmaceutically acceptable in vivo hydrolysable ester thereof.

In addition, the present invention includes the use of a compound of formula (la) or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, in the manufacture of a medicament for the treatment of bacterial infections.

The antibiotic compounds of the present invention are active against a wide range of organisms including both Gram-negative organisms and Gram-positive organisms.

The following Examples illustrate compounds of the present invention. Route steps are identified with reference to Routes A and 3. Examples 1-5 illustrate Route A, and Examples 6-10 illustrate Route B.

Route B

Example 1(a)

Steps A1, A2, A3 4-Nitrobenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[2-(1-methyl-1,2,3-triazol-4-yl)ethenyl]penem- 3-carboxylate

Step A1 A stirred solution of 4-nitrobenzyl (5R,6S)-6-[1-(R)- t-butyldimethylsilyloxyethyl]-2-hydroxymethylpenem-3carboxylate [J. Antibiot., 36, 938 (1983)] (247mg) in dry tetrahydrofuran (THP) (3ml) was cooled in an ice bath and treated with 2,6-lutidine (0.064ml) and thionyl chloride (0.040ml). The ice bath was removed and the mixture was stirred for a further 30 minutes. The mixture was diluted with dry toluene 3ml, filtered, and the and the residue was washed with dry toluene (2ml). The combined filtrates were evaporated and the residue re-evaporated from dry toluene (2ml) to give 4-nitrobenzyl (5R,6S)-2-chloromethyl-6-[1-(R)-t-butyldimethylsilyloxyethyl]penem-3-carboxylate as a gum; !_max (CHCI₃) 1790, 1710cm^-1.

Step A2

The 2-chloromethylpenem from step A1 was redissolved in dry acetonitrile (3ml) and treated with triphenylphosphine (131mg) and sodium iodide (dried, 75mg). After stirring at room temperature for 1 hour the mixture was evaporated to give [5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-3-(4-nitrobenzyloxycarbonyl)penem-2-ylmethyltriphenylphosphonium iodide as a crude amorphous solid; γ_max(CH₂Cl₂) 1790, 1700, 1630, 1605cm^-1.

Step A3

The phosphonium salt from step A2 was dissolved in dichloromethane (5ml) and treated with 1-methyl-1,2,3-triazole-4- carbaldehyde (Liebigs Ann.Chem., 558, 34, 1947) (56mg). The mixture was partitioned with 2% aqueous sodium carbonate solution (3ml) and stirred at room temperature for 3 hours. The mixture was diluted with ethyl acetate (20ml), washed with brine (3 × 3ml), dried (MgSO₄), and evaporated. The crude product was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 3:2 mixture of Z and E isomers of the title penem as a yellow amorphous solid (102mg); γ_{ma x}(CHCl₃) 1790, 1705cm^-1; δppm (CDCI₃) 0.03, 0.05, 0.07, and 0.08 (6H, each s), 0.82 and 0.84 (9H, each s),

1.23 (d, J 6.3Hz) and 1.28 (d, J 6.4Hz) together 3H, 3.74-3.75 (1H, m), 4.12 and 4.13 (3H, each s), 4.23-4.34 (1H, m), 5.22 and 5.42 (ABq, J 13.7Hz) and 5.26 and 5.44 (ABq, J13.7Hz) together 2H, 5.58 (poorly resolved d, J 1Hz) and 5.61 (d, J1.2Hz) together 1H, 6.8 (⅗ H, d, J12.4Hz), 6.92 (⅖ H, d, J 16.2Hz), 7.12 (⅗ H, d, J 12.4Hz), 7.61 and 7.72 (3H, m) 8.00 (⅖ H, d, J 16.2Hz), 8.22 and 8.23 (2H, each d, J8.7Hz). [Pound: MH⁺, 572

(thioglycerol FAB)].

Example 1(b)

Step A4 4-Nitrobenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(1- methyl-1,2,3-triazol-4-yl)ethenyl]penem-3-carboxylate

A mixture of the penem from step A3 (Z:E ratio 3:2, 100mg),

tetra-n-butylammonium fluoride trihydrate (165mg), glacial acetic acid (0.10ml), and dry THF (2ml) wasstirred at room temperature for 28 hours. The mixture was diluted with ethyl acetate (15ml) and was washed with brine (1ml), sat^d NaHCO₃ (1ml), and brine (3 × 1ml). The dried (MgSO₄) organic layer was evaporated and the residue chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 3:2 mixture of Z and E isomers of the title penem as a solid (52mg); γ_max (Nujol)

3600-3100, 1780, 1700cm^-1; δppm (CDCI₃) 1.37 and 1.41 (3H, each d,

J 6.3Hz), 3.78-3.80 (1H, m), 4.12 and 4.13 (3H, each s), 4.22-4.37 (1H, m), 5.24 and 5.46 (ABq, J 13.7Hz) plus 5.29 and 5.51 (ABq, J 13.7Hz) together 2H, 5.60 (d, J 1.6Hz) and 5.63 (d, J 1.5Hz) together 1H, 6.81 (⅗ H, d, J 12.4Hz), 6.92 (⅖ H, d, J16.4Hz), 7.06 (⅗ H, d, J 12.4Hz), 7.60-7.70 (3H, m), 8.00 (⅖ H, d, J 16.2Hz), 8.22 and 8.24 (2H, each d, J 8.7Hz). [Found: MNa⁺ 480 (3-nitrobenzyl alcohol/Na FAB)]. Example 1(c) Step A5

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(1-methyl-1,2,3-triazol-4-yl)ethenvl]penem-3-carboxylate

The penem from example 1(b)(Z:E ratio 3:2, 50mg) was dissolved in a mixture of dioxan (16ml) and water (4ml) and was hydrogenated over 5% palladium/carbon (50mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate (0.92ml) was added and the mixture was filtered through Kieselguhr, the residue being washed with a little dioxan/water

(1/1). The combined filtrates were evaporated and the residue was chromatographed on HP20SS eluting with water/THF mixtures. The appropriate fractions were concentrated and freeze-dried to give a 3:2 mixture of E and Z isomers of the title penem (6, 17mg); γ_max(KBr) 3393,

1762, 1595cm^-1 δppm (D₂O) 1.25 (d, J 6.4Hz) and 1.29 (d, J 6.5Hz) together

3H, 3.84-3.89 (1H, m), 4.06 and 4.08 (3H, each s), 4.15-4.30 (1H, m), 5.58 and 5.60 (1H, each slightly broadened s), 6.63 (d, J 12.2Hz) and 6.66 (d, J 16.3Hz) together 1H, 6.89 (⅖ H, d, J 12.2Hz), 7.89 (⅗ H, d, J 16.3Hz), 7.95 (⅖ H, s), 8.06 (⅗ H, s).

Example 2(a)

Steps A1, A2, A3 4-Nitrobenzyl(5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[2-(4-methylthiazoI-5-yl)ethenyl]penem-3- carboxylate

Step A1 A stirred solution of the 2-hydroxymethylpenem as used in example 1(a) (247mg) in dry THF (3ml) was cooled in an ice bath and treated with 2,6-lutidine (0.087ml) and thionyl chloride (0.055ml). The ice bath was removed and the mixtue was stirred for a further 30 minutes. The mixture was diluted with dry toluene (3ml), filted, and the residue was washed with dry toluene (2ml). The combined filtrates were evaporated and the residue was re-evaporated from dry toluene (2ml) to give the 2-chloromethylpenem as a gum.

Step A2

The 2-chloromethylpenem from Step Al was redissolved in dry

acetonitrile (3ml) and treated with triphenylphosphine (131mg) and dried sodium iodide (75mg). After stirring at room temperature for 1 hour the mixture was evaporated to give the phosphonium salt.

Step A3

A mixture of the phosphonium salt from Step A2, 4-methylthiazole-5-carbaldehyde (J. A m.Chem.Soc, 104, 4934, 1982) (64mg),

dichloromethane (5ml), and 2% aqueuos sodium carbonate solution (3ml) was stirred for 3 hours at room temperature. The mixture was diluted with ethyl acetate (20ml) and washed with brine (3ml), 2% sodium metabisulphite (3ml), brine (3ml), sat^d NaHCO₃ solution (3ml), and brine (3 × 3ml). The dried (MgSO₄) organic layer was evaporated and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 1:1 mixture of E and Z isomers of the title penem as a gum, (61mg); γ_max (CHCI₃) 1790, 1700cm^-1; δppm

[(CD₃)₂CO]. inter alia, 2.39 and 2.53 (3H, each s), 3.68 (½ H, dd, J 3.6 and

1.6Hz), 3.75 (½H, dd, J 4.4 and 1.6Hz), 4.20-4.33 (1H, m), 5.22, 5.26, 5.41 and 5.46 (2H, 2ABq, J13.6Hz),5.53 (½ H, d, J 1.6Hz), 5.60 (½ H, d, J 1.6Hz), 6.76 (½ H, d, J 11.4Hz), 6.91 (½ H, d, J15.6Hz), 7.20 (½ H, d, J 11.4Hz), 7.72 (½ H, d, J 15.βHz), 8.66 (½ H, s), 8.76 (½ H, s), other signals indicated the presence of approximately 10% of the 2-hydroxymethylpenem (1). Example 2(b)

Step A4

4-Nitrobenzyl(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(4-methylthiazol-5-yl)ethenyl]penem-3-carboxylate

A mixture of the penem from step A3 (E:Z ratio 1:1, 50mg),

tetra-n-butylammonium fluoride trihydrate (80mg), glacial acetic acid

(0.049ml), and dry THF (1ml) was stirred at room temperature for 48 hours. The mixture was worked up as for Example Kb) to give a 4:3 mixture of E and Z isomers of title penem as an amorphous solid (25mg); δppm [(CD₃)₂CO], inter alia 1.28 and 1.33 (3H, each d, J 6.3Hz), 2.34 and

2.50 (3H, each s, ratio 4:3), 3.85 (dd, J 6.2 and 1.7Hz) and 3.89 (dd, J 6.2 and 1.5Hz) together 1H, 4.13-4.30 (1H, m), 4.42 and 4.49 (1H, each d, J 4.9Hz), 5.71 (4/7 H, d, J 1.7Hz), 5.76 (3/7 H, d, J 1.5Hz), 6.91 (4/7H, d,

J12.8Hz), 7.05 (d, J 14,1Hz) and 7.06 (d, J 12.8Hz) together 1H, 7.82 (3/₇H, J 14.1Hz), 8.91 and 8.96 (1H, each s, ratio 3:4), other signals indicated the presence of 10-15% of 4-nitrobenzyl

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-hydroxy- methylpenem-3-carboxylate [Chem. Pharm. Bull., 34, 999 (1986)].

Example 2(c)

Step A 5 Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(4-methylthiazol-5-yl)ethenyl]penem-3-carboxylate

The penem ester from example 2(b)(E:Z ratio 4:3, 47mg) was dissolved in a mixture of dioxan (8ml) and water (2ml) and was hydrogenated over 5% palladium/carbon (47mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogcarbonate solution (0.84ml) was added and the mixture was worked up as for Example 1(c) to give a 1:1 mixture of the E and Z isomers of the title penem as a yellow solid (24mg); γ_max(KBr) 3388br, 1762, 1691cm^-1; δppm (D₂O) 1.21 and 1.27 (3H, each d, J 6.4Hz), 2.29 and 2.38 (3H, each s), 3.80 (dd, 15.9 and 1.3Hz) and 3.85 (dd, J6.0 and 1.2Hz) together 1H, 4.10-4.28 (1H, m), 5.54 (½ H, d, J1.3Hz), 5.57 (½H, d, J1.2Hz), 6.69, 6.76 and 6.81 (1½H, eachd, J11.6, 15.6, and 11.6Hz respectively), 7.63 (½H, d,

J 15.6Hz), 8.73 (½ H, s), 8.86 (½ H, s). Example 3 (a)

Step A3 4-Nitrobenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[2-(2-furyl)ethenyl]penem-3-carboxylate

A mixture of the phosphonium salt [prepared as described in Example

2(a)], 2-fuxaldehyde (48mg), dichloromethane (5ml), and 2% aqueous sodium, carbonate (3ml) was stirred at room temperature for 2½ hours. The mixture was worked up as for Example 2(a) to give a 4:1 mixture of the E. and Z isomers of the title penem as a yellow foam (91 mg); γ_max(CHCl₃)

178δ, 1706cm^-1; δppm (CDCl₃) 0.04, 0.05, 0.07, 0.08 (6H, each s), 0.83 and

0.84 (9H, each s), 1.24-1.29 (3H, m), 3.72 (dd, J 4.3 and 1.4Hz) and 3.76 (dd, J 4.0 and 1.4Hz) together 1H, 4.22-4.3δ (1H, m), 5.18-5.48 (2H, m), 5.58 and 5.60 (1H, each br.s), 6.44-6.46 (1H, m), 6.50-6.δδ

(1⅕H, m), 6.61 (⅘H, d, J 15.8Hz), 6.81 (⅕H, d, J 12.7Hz), 7.46-7.48 (1H, m), 7.62 (d, J 8.8Hz) and 7.67 (d, J 8.6Hz) together 2H, 7.86 (⅘H, d,

J 15.8Hz), 8.19-8.25 (2H, m). [Found: MNa⁺, 579 (3-nitrobenzyl alcohol/Na FAB)].

Example 3(b) Step A4

4-Nitrobenzyl (5R,6S)-2-[2-(2-furyl)ethenyl]-6-[1-(R)-hydroxyethylpenem-3-carboxylate A mixture of the penem from example 3(a)(E:Z ratio 4:1, 85mg),

tetra-n-butylammonium fluoride trihydrate (144mg), glacial acetic acid (0.087ml), and dry THF (2ml) was stirred at room temperature for 48 hours. The mixture was worked up as for Example Kb) to give a 4:1 mixtue of E and Z isomers of the title penem as a solid (50mg);

γ_max(CHCl₃) 3650-3100 br, 1785, 1705cm^-1; δppm [(CD₃)₂CO], inter alia

1.30 and 1.33 (3H, each d, J 6.3Hz), 3.79 (⅕ H, dd, J 6.5 and 1.7Hz), 3.86 (⅘ H, dd, J 6.4 and 1.7Hz), 4.14-4.30 (1H, m), 4.49 (1H, d, J 4.8Hz), 2.71 (⅘ H, d, J 1.7Hz), 5.74 (⅘ H, d, J 1.7Hz), 6.78 (⅘ H, d, J 16.0Hz), 7.90 (⅘ H, d, J 16.0Hz). [Found: M⁺ 442, (E.I.)]. Example 3_(c)

Step A5 Sodium (5R,6S)-2-[2-(2-furyl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylate

The penem ester from example 3(b)(E:Z ratio 4:1, 48mg) was dissolved in a mixture of dioxan (8ml) and water (2ml) and hydrogenated over 5% palladium/carbon (48mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate solution (0.91ml) was added and the mixtue was worked up as for Example 1(c) to give a 6:1 mixture of E and Z isomers of the title penem as a yellow solid (16mg); γ_max (KBr) 3397 br, 1762, 1594,

1527cm^-1; δppm (D₂O), E-isomer, 1.28 (3H, d, J 6.4Hz), 3.85 (1H, d, J6.2 and 1.3Hz), 4.23 (1H, dq, J6.4 and 6.2Hz), 5.57 (1H, d, J 1.3Hz), 6.47-6.63 (4H, m), 7.52 (1H, br.s), 7.70 (1H, d, J 15.9Hz).

Example 4(a)

Route A: Step A3

4-Nitrobenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[2-(isothiazol-5-yl)ethenyl]penem-3-carboxylate

A mixture of the phosphonium salt [prepared as described in Example 2(a)], 5-formylisothiazole (57mg),dichloromethane (5ml), and 2% aqueous sodium carbonate (3ml) was stirred at room temperature for 2 ½ hours. The mixture was worked up as for Example 2(a) to give a 6:1 mixture of E and Z isomers of the title penem as a yellow amorphous solid (147mg);

γ_max(CHCl₃) 1795, 1710cm^-1; δppm (CDCI₃) 0.03, 0.05, 0.06 and 0.08 (6H, each s), 0.82 and 0.83 (9H, each s), 1.22 (d, J 6.8Hz) and 1.28 (d,

J 6.2Hz) together 3H, 3.75-3.80 (1H, m), 4.24-4.37 (1H, m), 5.22 and 5.41 (ABq, J13.3Hz) plus 5.27 and 5.46 (ABq, J 13.5Hz) together 2H, 5.61 and 5.64 (1H, each br.s), 6.87 (1/7 H, d, J 12.0Hz), 6.92 (6/7H, d, J15.9Hz), 7.09

(1/7 H, d, J 12.0Hz), 7.26 (1H, br.s), 7.60-7.68 (2H, m), 7.99 (6/7H, d,

J 15.9Hz), 8.20-8.26 (2H, m), 8.46 (1H, br.s). [Found: MNa⁺, 596

(3-nitrobenzyl alcohol/Na FAB)]. Example 4(b)

Step A4

4-Nitrobenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(isothiazol-5-yl)ethenyl]-penem-3-carboxylate A mixture of the penem from example 4(a)(E:Z ratio 6:1, 145mg),

tetra-n-butylammonium fluoride trihydrate (240mg), glacial acetic acid (0.15ml), and dry THF (2ml) was stirred at room temperature for 24 hours. The mixtue was worked up as for Example 1(b) to give a 9:1 mixture of E and Z isomers of the title penem as a solid (50mg); γ_max (Nujol) 3440, 1775, 1705cm^-1; δppm [(CD₃)₂CO] E-isomer 1.33 (3H, d, J 6.3Hz), 3.93 (1H, dd, J6.2 and 1.7Hz), 4.19-4.31 (1H, m), 4.49 (1H, d, J 4.7Hz), 5.40 and 5.60 (2H, ABq, J 13.9Hz), 5.80 (1H, d, J 1.7Hz), 7.20 (1H, d, J16.0Hz), 7.52 (1H, d, J1.7Hz), 7.85 (2H, d, J 8.8Hz), 8.02 (1H, d,

J 16.0Hz), 8.28 (2H, d, J 8.8Hz), 8.60 (1H, d, J 1.7Hz). Other signals including 6.92 and 7.08 (each d, J11.8Hz) indicated the presence of appoximately 10% Z-isomer. Example 4(c)

Step A5

Sodium (5R,6S)-2-[2-(isothiazol-5-yl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylate

The penem ester from example 4(b)(E:Z ratio 9:1, 46mg) was dissolved in a mixtue of dioxan (8ml) and water (2ml) and was hydrogenated over 5% palladium/carbon (46mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate (0.84ml) was added and the mixture was worked up as for Example 1(c) to give an approximately 20:1 mixture of the E and Z isomers of the title penem as a yellow amorphous solid (26mg); γ_max (KBr) 3401 br, 1762, 1608, 1642cm^-1; δppm (D₂O) E-isomer 1.28 (3H, d, J6.3Hz), 3.90 (1H, d, J 5.9Hz), 4.18-4.30 (1H, m), 6.62 (1H, s), 6.90 (1H, d, J 16.1Hz), 7.36 (1H, s), 7.91 (1H, d, J 16.1Hz), 8.39 (1H, s).

Example 5(a)

Steps A2 and A3

4-Nitrobenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxvethyl]-2-[2-(2-thienyl)ethenyl]penem-3-carboxylate

Step A2 A mixture of the 2-chloromethylpenem [prepared as in Example 1(a)], triphenylphosphine (131mg), dried sodium iodide (75mg), and dry acetonitrile (3ml) was stirred for 2 hours at room temperature.

Step A3

The mixture was treated with 2-thiophenecarboxaldehyde (56mg) and diisopropylethylamine (0.088ml). After stirring for a further 20hours at room temperature the mixture was diluted with ethyl acetate (20ml) and was washed with 5% citric acid (3ml), brine (3ml), 5% sodium

metabisulphite solution (2×3ml), brine (3ml), saturated NaHCO₃ solution (3ml), and brine (3×3ml). The dried (MgSO₄) organic layer was

evaproateci and the residue chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 4:1 mixture of the E and Z isomers of the title penem as a yellow amorphous solid (65mg); γ_max (CHCI₃)

1790, 1705cm^-1; δppm (CDCI₃) inter alia 1.17 and 1.23 (3H, each d, J

6.3Hz), 3.67 (1H, dd, J 4.2 and 1.3Hz), 4.23 (1H, dq, J 6.3 and 4.2Hz), 5.53 (1H, d, J 1.3Hz), 6.73 and 6.79 (0.4H, each d, J 12.0Hz), 6.90 (0.8H, d, J 15.8Hz), 6.97 (1H, dd, J 5.0 and 3.4Hz), 7.11 (1H, d, J 3.4Hz), 7.28 (1H, d, J 5.0Hz), 7.76 (0.8H, d, J 15.8Hz). Example 5(b)

Step A4

4-Nitrobenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(2- thienyl)ethenyl]penem-3-carboxylate A mixture of the penem from example 5(a)(E:Z ratio 4:1, 125mg)

tetra-n-butylammonium fluoride trihydrate (207mg), glacial acetic acid (0.125ml), and dry THF (2ml) was stirred for 24 hours at room

temperature. The mixture was worked up as for Example 1(b) to give a 3:1 mixture of the E and Z isomers of the title penem as an amorphous solid (69mg); α_max (CHCI₃) 3650-3150, 1790, 1705cm^-1; δppm [(CD₃)₂CO] inter alia 5.74 (0.75H, d, J 1.6Hz), 5.76 (0.25, d, J 1.6Hz), 6.64 (0.25H, d, J 12.0Hz), 6.95 (0.25H, d, J 12.0Hz), 7.14 (0.75H, d, J 15.5Hz), 7.8δ (0.75H, d, J 15.5Hz). [Found: M+, 458 (EI)]. Example 5(c)

Step A5

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)-ethenyl]penem-3-carboxylate The penem ester from example 5(b)(E:Z ratio 3:1, 66mg) was dissolved in a mixture of dioxan (8ml) and water (2ml) and was hydrogenated over 5% palladium/carbon (66mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate solution (1.21ml) was added and the mixture was worked up as for Example 1(c) to give a 3:2 mixture of the E and Z isomers of the title penem as a yellow amorphous solid (25mg); γ_max (KBr) 3405,

1758, 1590cm^-1; δppm (D₂O) 1.26-1.31 (3H, m), 3.86 (0.6H, dd, J 6.0 and

1.4Hz), 3.89 (0.4H, dd, J 5.9 and 1.4Hz), 4.17-4.30 (1H, m), 5.58 (0.6H, d, J 1.4Hz). 5.66 (0.4H, d, J 1.4Hz), 6.34 (0.4H, d, J 11.8Hz), 6.81 (0.4Hz, d, J 11.8Hz), 6.94 (0.6H, d, J 15.8Hz), 7.03-7.07 (1H, m), 7.12 (0.4H, d, J

3.3Hz), 7.20 (0.6H, d, J 3.5Hz), 7.41 (0.6H, d, J 5.0Hz), 7.48 (0.4H, d, J 5.0Hz), 7.73 (0.6H, d, J 15.8Hz). Example 6(a)

Step B1

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-4-(tri¬phenylmethylthio)azetidin-2-one

Sodium hydride (0.96g of a 50% dispersion in oil) was added, portionwise over 5 minutes, to a stirred suspension of triphenylmethyl mercaptan (5.52g) in methanol (100ml) under dry argon at ice bath temperature. After stirring at ice bath temperature for 15 minutes the mixture was treated, dropwise of 15 minutes with a solution of (3R,4R)-4-acetoxy-3-[1-(R)-t-butyldimethylsilyloxyethyl]-azetidin-2-one (5.74g) in methanol (25ml). After stirring at ice bath temperature for 30 minutes the mixture was evaporated to low volume, diluted with ethyl acetate

(400ml), and washed with 5% citric acid (50ml), brine (50ml), saturated NaHCO₃ (50ml), and brine (3×50ml). The dried (MgSO₄) organic layer was evaporated and the residue was triturated with n-h]xane to give the title azetidinone as a solid (8.08g); δppm (CDCI₃) inter alia 0.78 (9H, d), 1.32 (3H, d, J 6.3Hz), 3.16 (1H, dd, J 1.7 and 2.1Hz), 4.27 (1H, dq, J 6.3 and 2.1Hz), 4.39 (1H, brs), 4.59 (1H, d, J 1.7Hz), 7.26-7.55 (15H, m). Example 6(b)

Step B2

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-1-[1- (4-nitrobenzyloxycarbonyl)-1-triphenylphosphoranylidene)methyl]-4-(triphenylmethylthio)azetidin-2-one

A mixture of the azetidinone from example 6(a)(8.08g) and 4-nitrobenzyl glyoxylate monohydrate (3.65g) was heated in refluxing benzene (160ml) with provision for azeotropic removal of water (Dean and Stark

apparatus) for 1 hour. The mixture was cooled to room temperature and treated with triethylamine (0.22ml). After stirring at room temperature for 3 hours the mixture was evaporated to give an amorphous solid. This material was redissolved in dry THF (100ml), cooled to -20°C, and treated with 2,6-lutidine (2.80ml) and thionyl chloride (1.76ml). After stirring at -20°C for 15 minutes the mixture was diluted with dry toluene (50ml), filtered, and the residue was washed with dry toluene (20ml). The combined filtrates were evaporated and the residue was re-evaproated from dry toluee (2×20ml) to give a gum. This material was dissolved in dry dioxan (50ml) and treated with triphenylphosphine (16.8g). The mixture was stirred until homogenous and evaporated to low volume

(approximately 20ml). The mixture was treated with 2,6-lutidine (2.24ml) and stirred under dry argon for 2½ days at room temperature followed by

24 hours at 40°C. The mixture was diluted with ethyl acetate (200ml) and washed with 5% citric acid (50ml), brine (50ml), satd. NaHCO₃ (50ml), and brine (3×50ml). The Tied (MgS04) organic layer was evaporated and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give the title phosphorane as an amorphous solid (9.53g); γ_max (CHCI₃) 1745, 1615cm^-1. Example 6(c)

Step B3

Silyer (3S,4R) 3-[1-(R)-t-butyldimethylsilyloxyethyl]- 1-[1-(4-nitrobenzyloxycarbonyl)-1-(triphenylphosphoranylidene)methyl]azetidin-2-one-4-thiolate

Silver nitrate (8.67ml of 0.15M solution in methanol) was added to a stirred solution of the phosphorane from example 6(b)(966mg) and pyridine (0.105ml) in methanol (8ml) at room temperature. After stirring at room temperature for 30 minutes the mixture was evaporated and the residue was re-evaporated from dry toluene (2ml) to give the crude silver thiolate as a foam.

Example 6(d)

Step B4

Methvl 3(1-methylpyrazol-4-yl)propenoate

A mixture of 1-methylpyrazole-4-carboxaldehyde (J. Chem. Soc, 1957, 3314) (1.10g), carbomethoxymethylene- triphenylphosphorane (3.34g), and dry dichloromethane (50ml) was stirred at room temperature for 20 hours and evaporated. The residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give the E isomer of the title ester as a solid (1.43g); γ_max (CHCI₃) 1700, 1640cm^-1; δppm (CDCI₃) 3.62 (3H, s), 3.86 (3H, s), 6.12 (1H, d, J 16Hz), 7.51 (1H, d, J 16Hz), 7.54 (1H, s), 7.65 (1H, s).

Example 6(e)

Step B5

3-(1-Methylpyrazol-4-yl)propenoic acid

A mixture of the ester from example 6(d)(E isomer, 1.43g), dioxan (30ml), and aqueous sodium hydroxide (1M, 17.2ml) was stirred for 4 hours at room temperature. The mixture was evaporated to low volume and washed with ethyl acetate (δml). The pH of the aqueous layer was adjusted to 2.0 using 5M. hydrochloric acid. The precipitated solid was filtered off, washed with cold water (2×2ml), and dried under vacuum over P₂O₅ te give the title acid (0.57g); α_max (Nujol) 3300-2000, 1685,

1630cm^-1; δppm [(CD₃)₂CO + (CD₃)₂SO] 3.85 (3H, s), 5.0-6.9 (broad signal) and 6.14 (d, J 16Hz), together 2H, 7.49 (1H, d, J 16Hz), 7.72 (1H, s), 7.90 (1H, s). Evaporation of the combined filtrates to approximately half volume provided a second crop of the acid (22, 0.43g). Example 6(f)

Step B6

3-(1-Methylpyrazol-4-yl)propenoyl chloride hydrochloride

A stirred mixture of the acid from example 6(e)(152mg) and oxalyl chloride (0.13ml) in dry dichloromethane (3ml) was treated with dry dimethylformamide (1 drop). After stirring at room temperature for 3 hours the mixture was evaporated and the residue was re-evaporated from dry toluene (1ml) to give the title acid chloride (23) as a solid; γ_max

(Nujol) 2500br, 1690cm^-1. Example 6(g)

Step B7

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-4-[3- (1-methylpyrazol-4-yl)propenoylthiol-1-[1-(4-nitrobenzyloxycarbonyl)-1-(triphenylphosphoranylidene)methyl]-azetidin-2-one

The acid chloride [ex. Example 6(f)] was added, portionwise over 1 minute to a stirred solution of the silver thiolate [ex. Example 6(c)] and pyridine (0.162ml) in dry dichloromethane (10ml) at ice bath temperature. After stirring at ice bath temperature for 40 minutes the mixture was diluted with ethyl acetate (10ml), filtered through Kieselguhr, and the residue was washed with ethyl acetate (2×10ml). The combined filtrates were washed with 5% citric acid (5ml), brine (5ml), satd. NaHCO₃ (5ml), and brine (3×5ml). The dried (MgSO₄) organic layer was evaporated and the residue was chromatographed on silica gel eluting with ethyl

acetate/hexane mixtures to give the title phosphorane as an amorphous solid (623mg); γ_max (CHCI₃) 1745, 1660sh., 1610cm^-1.

Example 6(h)

Step B8

4-Nitrobenzyl (5R,6S)-6-[1-(R)-t-butyIdimethylsilyloxyethyl]-2-[2-(1-methylpyrazol-4-yl)ethenyl]penem-3-carboxylate

A solution of the phosphorane from example 6(g)(620mg) in dry toluene (310ml) was heated at reflux under dry argon for 12 hours. The mixture was cooled, evaporated, and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give an approximately 10:1 mixture of the E and Z isomers of the title penem as a yellow amorphous solid (284mg); γ_max (CHCI₃) 1785, 1700cm^-1; δppm (CDCI₃)

E-isomer 0.05 and 0.08 (6H, each s), 0.84 (9H, s), 1.28 (3H, d, J.6.3Hz), 3.70 (1H, dd, J 4.1 and 1.5Hz), 3.90 (3H, s), 4.36 (1H, dq, J 6.3 and 4.3Hz), 5.24 and 5.45 (2H, ABq, J 13.8Hz), 5.55 (1H, d, J 1.5Hz), 6.69 (1H, d, J 16.0Hz), 7.53 (1H, s), 7.63-7.73 (4H, m), 8.21-8.25 (2H, m); Z-isomer (inter alia) 0.03, 0.06 (each s), 0.82(s), 1.22 (d, J 6.3Hz), 5.22 and 5.43 (ABq, J 13.7Hz), 5.52 (d, J 1.5Hz), 6.63 and 6.93 (each d, J 12.0Hz), 7.40(s).

[Found; MH⁺, 571; MNa⁺, 593 (3-nitrobenzyl alcohol/Na FAB].

Example 6(i)

4-Nitrobepzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(1-methylpyrazol-4-yl)ethenyl]penem-3-carboxylate

A mixture of the penem from example 6 (h)(E:Z ratio approximately 10:1, 280mg), tetra-n-butylammonium fluoride trihydrate (465mg), glacial acetic acid (0.28ml), and dry THF (3ml) was stirred at room temperature for 24 hours. The mixture was worked up as for Example 1(b) to give, after chromatography on silica gel eluting with dichloromethane/ethyl acetate mixtures, an approximately 6:1 mixture of the E and Z isomers of the title penem as a solid (138mg); γ_max (Nujol) 3230br, 1796, 1700cm^-1; δppm [(CD₃)₃SO] E-isomer 1.20 (3H, d, J 6.1Hz), 3.81-3.86 (4H, m), 3.97-4.09 (1H, m), 5.35 and 5.49 (2H, ABq, J 13.9Hz), 5.63 (1H, d, J 1.4Hz), 6.83 (1H, d, J 16.0Hz), 7.57 (1H, d, J 16.0Hz), 7.67 (1H, s), 7.74 (2H, d, J 8.7Hz), 8.02 (1H, s), 8.25 (2H, d, J 8.7Hz); Z isomer (inter aha) 5.67 (1H, d, J 1.4Hz), 6.62 and 6.68 (2H, each d, J 12.2hz), 7.87 (1H, s). [Found: M+, 456 (El)]. Example 6(j)

Step B10

Sodium (5R,6S) 6-[1-(R)-hydroxyethyl]-2-[2-(1-methylpyrazol-4-yl)ethenyl]penem-3-carboxylate

The penem ester from example 6(i)(E:Z ratio approximately 6:1, 130mg) was dissolved in a m ixture of dioxan (32ml) and water (8ml) and was hydrogenated over 5% palladium/carbon (130mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate solution (2.39ml) was added and the mixture was worked up as for Example 1(c) to give a 3:2 mixture of the E and Z isomers of the title penem as a pale yellow amorphous solid (18mg); γ_max (KBr) 3373 br, 1757, 1594cm^-1; δppm (D₂O) 1.25 and 1.27

(3H, each d, J 6.6Hz), 3.81-3.84 (4H, m), 4.15-4.27 (1H, m), 5.54 (0.6H, d, J 1.1Hz), 5.56 (0.4H, d, J 1.3Hz), 6.50-6.55 (0.8H, each d, J 12.0Hz), 6.62 (0.6H, d, J 16.1Hz), 7.54 (0.4H, s), 7.61 (0.6H, d, J 16.1Hz), 7.63 (0.4H, s), 7.71 (0.6H, s), 7.76 (0.6H, s). Example 7(a)

Step B4

Ethyl (E)-2-methyl-3-(1-methyl-1,2,3-triazol-4-yl)prop2- enoate

A mixture of 1-methyl-1,2,3-triazole-4-carboxaldehyde (Liebigs Ann.

Chem., 558, 34, 1947) (1.11g) and

ethoxycarbonylethylidenetriphenylphosphorane (3.62g) in dry

dichloromethane (50ml) was stirred under dry argon for 1½ hours at room temperature. The mixture was evaporated and the residue

chromatographed on silica gel eluting with ethyl acetate/hexane to give the title ester, contaminated with a little triphenylphosphine oxide, as a solid (1.86g); γ_max (CHCI₃) 1695, 1645cm^-1; δppm (CDCI₃) inter alia 1.34 (3H, t, J 7.1Hz), 2.23 (3H, s), 4.15 (3H, s), 4.26 (2H, q, J 7.1Hz), 7.69 (1H, s), 7.71 (1H, s).

Example 7(b) (E)-2-Methyl-3-(1-methyl-1,2,3-triazol-4-yl)prop-2-enoic acid

A mixture of the ester from example 7(a)(780mg), dioxan (20ml), and aqueous sodium hydride (1M, 8.0ml) was stirred at room tempeature for 4½ hours. The mixture was evaporated to low volume and was washed with ethyl acetate (5ml). The pH ofthe stirred aqueous layer was adjusted to 2.0 using 5N. hydrochloric acid. The precipitated solid was filtered off, washed with cold water (2×1ml) and ether (2×1ml), and dried under vacuum over P₂O₅ to give the title acid as a solid (323mg), mp. 204-6°C; γ_max (Nujol) 3200-2000br, 1660, 1626cm^-1; δppm [(CD₃)₂SO] 2.13 (3H, d, J 0.9Hz), 2.8-3.1 (1H, brs), 4.09 (3H, s), 7.53 (1H, m), 8.41 (1H, s). (Found: C, 50.0; H, 5.3; N, 25.1. C₇H₉N₃O₂ requires C, 50.3; H, 5.4; N, 25.1%).

Example 7(c) (E)-2-Methyl-3-(1-methyl-1,2,3-triazol-4-yl)prop-2- enoyl chloride

A stirred suspension of the acid from example 7(b)(167mg) in dry

dichloromethane (2ml) was treated with oxalyl chloride (0.13ml) and dry dimethylformamide (1 drop). After stirring at room temperature for 4 hours the resulting solution was evaporated and the residue re-evaporated from dry toluene (1ml) to give the title acid chloride as a solid; γ_max

(CH₂CI₂) 1740, 1675, 1640cm^-1. Example 7(d)

Step B7

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-4-[2-methyl-3-(1-methyl-1,2,3-triazol-4-yl)prop-2-enoylthio]-1-[1-(4-nitrobenzyloxycarbonyl)-1-(triphenylphosphoranylidene)methyl]azetidin-2-one A solution of the acid chloride [ex. Example 7(c)] in dry dichloromethane (1ml) was added, dropwise over 1 minute, to a stirred solution of the silver thiolate [prepared as in Example 6(c)] and pyridine (0.081ml) in dry dichloromethane (10ml) at ice bath temperature. After stirring at ice bath temperature for 40 minutes the mixture was worked up as for example 6(g) to give the title phosphorane (395mg) as a foam; γ_max (CHCI₃) 1746,

1660, 1620cm^-1. Example 7(e)

Step B8

4-Nitrobepzyl (5R,6S)-6-[1-(R)-t-hutyldimethylsilyloxyethyl]-2-[(E)-1-(1-methyl-1,2,3-triazol-4-yl)prop-1-en- 2-yl]penem-3-carboxylate

A solution of the phosphorane from example 7 (d)(290mg) in dry xylene (150ml) was heated at reflux under dry argon for 6 hours. The mixture was worked up as for example 6(h) to give the title penem as a foam

(100mg); γ_max (CHCI₃) 1790, 1710cm^-1; δppm (CDCI₃) 0.05 (3H, s), 0.08 (3H, s), 0.84 (9H, s), 1.26 (3H, d, J 6.2Hz), 2.23 (3H, d, J 1.0Hz), 3.77 (1H, dd, J 4.1 and 1.5Hz), 4.12 (3H, s), 4.27 (1H, dq, J 6.2 and 4.1Hz), 5.18 and 5.35 (2H, ABq, J 13.7Hz), 5.65 (1H, d, J 1.5Hz), 6.82 (1H, m), 7.53 (1H, s), 7.56 (2H, d,J 8.8Hz), 8.14 (2H, d, J 8.8Hz). [Found: MH⁺, 586; MNa⁺ 608 (3-nitrobenzyl alcohol/Na FAB)].

Example 7(f)

Step B9

4-Nitrobenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E)-1-(1-methyl-1,2,3-triazol-4-yl)prop-1-en-2-yl]penem3-carboxylate

A mixture of the penem from example 7(e)(150mg),

tetra-n-butylammonium fluoride trihydrate (242mg), glacial acetic acid (0.15ml), and dry THF (2ml) was stirred at room temperature for 24 hours. The mixture was worked up as for Example 1(b) to give, after chromatography on silica gel eluting with dichloromethane/ethyl acetate mixtures, the title penem as a solid (95mg); γ_max (Nujol) 3500br, 1775,

1710cm^-1; δppm [(CD₃)₂CO] 1.34 (3H, d, J 6.3Hz), 2.26 (3H, d, J 0.9Hz),

3.90 (1H, dd, J 6.2 and 1.6Hz), 4.16 (3H, s), 4.17-4.28 (1H, m), 4.46 (1H, d, J 4.0Hz), 5.30 and 5.45 (2H, ABq, J 13.9Hz), 5.82 (1H, d, J 1.6Hz), 6.75 (1H, centre of m), 7.72 (2H, d, J 8.7Hz), 8.06 (1H, s), 8.15-8.19 (2H, m). [Found: MH⁺, 472; MNa+ 494 (3-nitrobenzylalcohol/Na FAB)].

Example 7(g)

Step B10

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E)-1-(1-methyl-1,2,3-triazol-4-yl)prop-1-en-2-yl]penem-3-carboxylate

The penem ester from example 7(f)(92mg) was dissolved in a mixture of dioxan (16ml) and water (4ml) and was hydrogenated over 5%

palladium/carbon (92mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate solution (1.64ml) was added and the mixture was worked up as for Example 1(c) to give the title penem as a pale yellow amorphous solid (48mg); λ_max (H₂O) 246.5-262.5 (εm 10,890) and

328.5nm (6011); γ_max (KBr) 3391, 1762, 1599cm^-1; δppm (D₂O) 1.29 (3H, d, J 6.4Hz), 2.10 (3H, s), 3.93 (1H, dd, J 5.9 and 1.2Hz), 4.09 (3H, s), 4.24

(1H, dq, J 5.9 and 6.4Hz), δ.68 (1H, d, J 1.2Hz), 6.62 (1H, s), 8.02 (1H, s).

Example 8(a)

Step B4

Methyl 3-(2-thienyl)but-2-enoate

A mixture of 2-acetylthiophene (1.26g), carbomethoxymethylenetriphenylphosphorane (3.34g); benzoic acid (122mg) and dry toluene (25ml) was stirred at 80°C under dry argon for 24 hours. The mixture was heated at reflux for a further 24 hours, cooled, evaporated, and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 1:1 mixture of E and Z isomers of the title ester as an oil (649mg); γ_max (Film) 1710, 1615cm^-1; δppm (CDCI₃) 2.22 (1.5H, d, J approx. 1Hz), 2.67 (1.5H, d, J 1Hz), 3.69 and 3.74 (3H, each s), 5.89-6.00 (0.5H, m), 6.30-6.41 (0.5H, m), 7.02-7.70 (3H, m).

Example 8(b)

Step B5

3-(2-Thienyl)but-2-enoic acid

A mixture of the ester from example 8(a)(E:Z ratio 1:1, 1.12g), dioxan

(20ml), and aqueous sodium hydroxide (1M, 12.3ml) was stirred at room temperature for 7 hours. The mixture was evaporated to low volume and washed with ethyl acetate (3ml). The pH ofthe stirred aqueous layer was adjusted to 2.0 using 5M hydrochloric acid and the oil which separated was extracted with ethyl acetate (2×5ml). The combined organic layers were washed with brine (2×2ml), dried (MgSO₄), and evaporated to give a

1:1 mixture of E and Z. isomers of the title acid as a solid (784mg); γ_max (CHCI₃) 3600-2200, 1685, 1610cm^-1; δppm (CDCI₃) 2.31 (1.5H, s), 2.60

(1.5H, s), 5.86 (0.5H, slightly broadened s), 6.27 (0.5H, slightly broadened s), 6.90-7.60 (3H, m). Example 8(c)

Step B6

3-(2-Thienyl)but-2-eneyl chloride

Dry dimethylformamide (1 drop) was added to a stirred mixture of the acid from example 8(b)(E:Z ratio 1:1, 168mg) and oxalyl chloride (0.13ml) in dry dichloromethane (3ml). After stirring at room temperature for 3 hours the mixture was worked up as for Example 7(c) to give the title acid chloride (37) as a gum; γ_max 1755, 1680cm^-1.

Example 8(d)

Step B7

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-1-[1- (4-nitrobenzyloxycarbonyl)-1-(triphenylphosphoranylidene)methyl]-4-[3-(2-thienyl)but-2-enoylthiolazetidin-2-one A solution of the acid chloride [ex Example 8(c)] in dry dichloromethane (1ml) was added, dropwise over 1 minute, to a stirred solution of the silver thiolate [prepared as in Example 6(c)] and pyridine (0.081ml) in dry dichloromethane (10ml) at ice bath temperature. After stirring at ice bath temperature for 40 minutes the mixture was worked up as for Example 6(g) to give the title phosphorane as a foam (647mg); γ_max (CHCI₃) 1745,

1685, 1605, 1585cm^-1.

Example 8(e)

Step B8

4-Nitrohenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[2-(2-thienyl)prop-1-en-1-yl]penem-3-carboxylate

A solution of the phosphorane from example 8(d)(640mg) in dry toluene (320ml) was heated at reflux under dry argon for 9 hours. The mixture was worked up as for Example 6(h) to give a 1:1 mixture of the E and Z isomers of the title penem as a yellow foam (166mg); γ_max (CHCI₃) 1780,

1700cm^-1; δppm (CDCI₃) 0.01, 0.Oδ, 0.05, 0.08 (6H, each s), 0.81 and 0.84

(9H, each s), 1.18 (1.5H, d, _.6.3Hz), 1.28 (1.6H, d, J 6.3Hz), 2.27 (1.5H, d, J 1.5Hz), 2.41 (1.5H, d, J 1.1Hz), 3.60 (0.5H, dd, J 3.8 and 1.5Hz), 3.74 (0.5H, dd, J 4.3 and 1.5Hz), 4.17-4.33 (1H, m), 5.22 and 5.24 (1H, each d, J 13.7Hz), 5.39 (0.5H, d, J 1.5Hz), 5.45 (1H, d, J 13.7hz), 5.63 (0.5H, d, J 1.5Hz), 6.95-7.74 (6H, m), 8.18-8.24 (2H, m). [Found: MNa⁺, 609

(3-nitrobenzyl alcohol/Na FAB]. Also obtained was recovered

phosphorane (370mg). A solution of the recovered phosphorane (370mg) in dry toluene (175ml) was heated at reflux under dry argon for 20 hours. Work up as before gave a 2:1 mixture of isomers of the title penem

(150mg).

Example 8(f)

Step B9

4-Nitrobenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)prop-1-en-1-yl]penem-3-carboxylate

A mixture of the penem from example 8(e)(a mixture of E and Z isomers, 310mg), tetra-n-butylammonium fluoride trihydrate (500mg), glacial acetic acid (0.30ml) and dry THF (5ml) was stirred for 24 hours at room temperature. The mixture was worked up as for Example 1(b) to give a 1:1 mixture of E and Z isomers of the title penem as a foam (181mg); γ_max

(CHCl₃) 3700-3150, 1786, 1700cm^-1; δppm [(CD₃)₂CO] 1.27 and 1.33 (3H, each d, J 6.3Hz), 2.24 (1.5H, d, J 1.4Hz), 2.43 (1.5H, d, J 1.2Hz), 3.70

(0.5H, dd, J 6.5 and 1.6Hz), 3.88 (0.5H, dd, J 6.3 and 1.7Hz), 4.10 and 4.30 (1H, m), 4.40 (0.5H, br d, J 4.6Hz), 4.49 (0.5H, br s), 5.32, 5.33, 5.53, 5.54 (2H, 2ABq, J 14.0Hz), 5.53 (0.5H, d, J 1.7Hz), 5.78 (0.5H, d, J 1.6Hz), 7.06-7.10 (2H, m), 7.32-7.33 (0.5H, m), 7.47-7.49 (0.5H, m), 7.61-7.63 (0.5H, m), 7.77-7.82 (2.5H, m), 8.21-8.27 (2H, m). [Found: MNa+, 495 (3-nitrobenzyl alcohol/Na FAB].

Example 8(g)

Step B10

Sodium (5R,5S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)- prop-1-en-1-yl]penem-3-carboxylate

The penem ester from example 8 (f)(E:Z ratio 1:1, 175mg) was dissolved in a mixture of dioxan (8ml) and water (2ml) and was hydrogenated over 5% palladium/carbon (175mg) for 30 minutes at S.T.P. A 1% aqueous solution of sodium, hydrogencarbonate (3.11ml) was added and the mixture was worked up as for Example 1(c) to give two fractions. The first fraction containeci an 8:1 mixture of the geometric isomers of the title penem

(20mg). The second fraction contained a 3:1 mixture of the geometric isomers of the title penem (37mg); γ_max (KBr) 3404 br, 1762, 1588cm^-1; δppm (D₂O) 1.22 and 1.28 (3H, each d, J 6.4Hz), 2.19 (0.75CH₃, d, J

1.2Hz), 2.29 (0.25CH₃, s), 3.73 (0.75H, dd, 16.9 and 1.3hz), 3.87 (0.25H, dd, J 5.9 and 1.0hz), 4.12-4.25 (1H, m), 5.45 (0.75H, d, J 1.3Hz), 5.63 (0.25H, d, J 1.0Hz), 6.66 (0.75H, d, J 1.3Hz), 7.03-7.08 (1.75H, m),

7.24-7.25 (0.25H, m), 7.36-7.37 (0.25H, m), 7.45 (0.25H, br s), 7.50 (0.75H, dd, J4.9 and l.3Hz). Example9(a)

Steps B11 and B12

Ethyl 2-(2-thienyl)but-2-enoate Lithium bis(trimethylsilyl)amide (20.0ml of a 1M solution in THF) was added to a stirred solution of ethyl 2-thiophenacetate (known

compound)(3.40g) in dry THF (70ml) at -76°C under dry argon. After 15 minutes at -76° the mixture was treated with acetaldehyde (2.24ml), stirred for 15 minutes, and treated with acetic anhydride (3.77ml). The cooling bath was removed and the mixture was stirred for a further 1 hour. The mixture was diluted with ethyl acetate (150ml) and was washed with 5% citric acid (20ml), brine (20ml), satd NaHCO₃ solution, and brine (3×20ml). The dried (MgSO₄) organic layer was evaporated to give an oil. This product was redissolved in dry dichloromethane (50ml), cooled in an ice bath, and treated with a solution of 1,8-diazabicyclo [5.4.0] undec-7-ene (2.99ml) in dry dichloromethane (10ml) dropwise over 10 minutes. The ice bath was removed and the mixture was stirred for 2 hours. The mixture was washed with 5% citric acid (10ml), brine (10ml), satd NaHCO₃ (10ml), and brine (3×10ml). The dried (MgSO₄) organic layer was evaporated and the residue was chromatographed on silica gel eluting with hexane and hexane/ethyl acetate mixtures to give a 3:1 mixture of isomers of the title ester as an oil (2.54g); ʋ_max (film) 1710,

1630 cm^-1; δppm (CDCl₃) 1.18-1.41 (3H,m), 1.89 and 1.99 (3H, each d,J 7Hz), 4.10-4.43 (2H, m), 6.35 (VA H, q, J 7Hz), 6.85-7.40 (33/₄ H,m).

Example 9(b)

Step B13

2-(2-Thienyl)but-2-enoic acid A mixture of the ester product from example 9(a)(3:1 mixture of isomers, 2.50g), dioxan (50ml), and aqueous sodium hydroxide (1M, 26.5ml) was stirred at room temperature for 3 days. The mixture was evaporated to low volume and was washed with ethyl acetate (5ml). The pH of the stirred aqueous layer was adjusted to 2.0 using 5M hydrochloric acid. The precipitated oil, was extracted with ethyl acetate ( 2×10ml). The combined organic layers were washed with brine (2×3ml), dried (MgSO₄), and evaporated to give a 5:1 mixture of isomers of the title acid as a solid (1.75g); ʋ_max (CHCI₃) 3550-2200, 1690, 1630 cm^-1; δ ppm (CDCI₃) 1.91 and 2.11 (3H, each d, J 7Hz, ratio approximately 5:1), 6.68 (1/6H, q, J 7Hz), 6.90-7.60 (35⅚H,m).

Example 9(c)

Step B14

2-(2-Thienyl)but-2-enoyl chloride

Dry dimethylformamide (1 drop) was added to a stirred mixture of the acid (5:1 mixture of isomers, 168mg) and oxalyl chloride (0.13ml) in dry dichloromethane (3ml). After stirring at room temperature from 1½ hours the mixture was evaporated and the residue was re-evaporated from dry toluene to give the title acid chloride as a gum; ʋ_max (CH₂CI₂) 1750,

1675, 1620 cm^-1.

Example 9(d)

Sten B7

(3S, 4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-1-[1-(4- nitrobenzyloxycarbonyl)-1-(triphenylphosphoranylidene)

methyl]-4-[2-(2-thienyl) but-2-enoylthiolazetidin-2-one A solution of the acid chloride [ex Example 9(c)] in dry dichloromethane

(lml) was added, dropwise over 1 minute, to a stirred solution of the silver thiolate [prepared as in Example 6 (c)] and pyridine (0.081ml) in dry dichloromethane (10ml) at ice bath temperature. After stirring at ice bath temperature for 40 minutes the mixture was worked up as for example 6 (g) to give the title phosphorane (380mg) as a foam; ʋ_max (CHCI₃) 1745,

1665, 1620 cm^-1.

Example 9(e)

Step B8

4-Nitrobenzyl (5R, 6S)-6-[1-(R)-t-butyldimethylsilyloxy ethyl]-2-n-(2-thienyl) prop-1-en-1-yl] penem-3-carboxylate

A solution of the phosphorane from example 9(d)(380mg) in dry xylene

(190ml) was heated at reflux under dry argon for 12 hours. The mixture was worked up as for example 6(h) to give a 3:1 mixture of geometric isomers of the title penem as a foam (11. mg); ʋ_max (CHCI₃) 1790, 171δ cm^-1; δpp (CDCI₃) inter alia, Major isomer, 0.79 (9H,S), 1.20 (3H,d, J

6.3Hz), 1.73(3H, d, J 7.0Hz), 3.76 (1H, dd, J 4.6 and 1.6Hz), 4.13-4.26 (1H,m), 5.04 and 5.21 (2H, ABq, J14.8Hz), 5.67 (1H, d, J1.6Hz), 6.08 (1H, q, J7.0Hz); Minor isomer, 0.77 (9H,s), 1.86(3H, d, J7.3Hz), 3.70 (1H, dd, J4.5 and 1.7Hz), 5.58 (1H, d, J1.7Hz), 5.96 (1H, q, J7.3Hz); [Found:

MNa⁺, 609 (3-nitrobenzyl alcohol/Na FAB).

Example 9(f)

Step B9

4-Nitrohenzyl (5R, 6S)-6-[1-(R)-hydroxyethyl]-2-[1-(2-thienyl) prop-1-en-1-yl]penem-3-carboxylate A mixture of the penem from example 9(a)(140mg), tetra-n-butylammonium fluoride trihydrate (226mg), glacial acetic acid (0.14ml), and dry THF (2ml) was stirred at room temperature for 24 hours. The mixture was worked up as for Example Kb) to give a 3:1 mixture of geometric isomers of the title penem as a foam (83mg); ʋ_max (CHCI₃) 3700-3200 br, 1785, 1710 cm^-1; δppm[(CD₃)₂CO] inter alia, Major isomer,

1.33 (3H, d, J 6.2Hz), 1.81 (3H, d, J7.1Hz), 3.96 (1H, dd, J6.2 and 1.7Hz), 4.16-4.34 (1H,m), 4.45 (1H, d, J4.9Hz), 5.21 and 5.34 (2H, ABq, J14.0Hz), 5.94 (1H, d, J1.7Hz), 6.21 (1H, q, J7.1Hz); Minor isomer, 1.91 (3H, d, J7.3Hz), 3.88 (1H, dd, J6.3 and 1.6Hz), 4.42 (1H, d, J4.9Hz), 5.19 and 5.32 (2H, ABq, J13.9Hz), 5.82 (1H, d, J1.6Hz), 6.05 (1H, q, J7.3Hz). [Found: M+, 472 (E.I.)].

Example 9(g)

Step B10

Sodium (5R, 6S)-6-[1-(R)-hydroxyethyl]-2-[1-(2-thienyl) Example 9(g)

Step B10

Sodium (5R, 6S)-6-[1-(R)-hydroxyethyl]-2-[ 1-(2-thienyl)

prop-1-en-1-yl]penem-3-carboxylate

The penem ester from example 9(f)(80mg) was dissolved in a mixture of dioxan (8ml) and water (2ml) and was hydrogenated over 5%

palladium/carbon (80mg) for 30 minutes at S.T.P. A 1% aqueous sodium hydrogencarbonate solution (1.42ml) was added and the mixture was worked up as for Example 1(c) to give a 4:1 mixture of geometric isomers of the title penem (48) as an off white solid (21mg); ʋ_max (KBr) 3397,

1762, 1603, 1570 cm^-1; δppm (D₂O) 1.26-1.31 (3H, m), 1.79 (0.8 CH₃, d, J7.1Hz), 1.91 (0.2 CH₃, d, J7.3Hz), 3.89 (0.2H, dd, J5.9 and 1.1Hz), 3.95

(0.8H, dd, J6.0 and1.2Hz), 4 7.4.32 (1H, m), 5.68 (0.2H, d, J1.1Hz), 5.79 (0.8H, d, J1.2Hz), 6.03 (0.2E 4, J7.3Hz), 6.2 1 (0.8H, q, J7.1Hz), 6.98-7.47 (3H,m).

Example 10(a)

Step B2 (paramethoxybenzyl protecting group)

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-1-[1-(4- methoxybenzyloxycarbonyl)-1-triphenylphosphoranylidene)

methyl]-4-(triphenylmethylthio)azetidin-2-one

A mixture of the azetidinone from example 6(a)(31.9g) and 4- methoxybenzyl glyoxylate monohydrate (European Patent 0232 966, Beecham Group PLC) (14.8g) was heated in refluxing benzene (800ml) with provision for the azeotropic removal of water (Dean and Stark apparatus) for 1 hour. The mixture was cooled to room temperature and treated with triethylamine (1.7ml). After stirring at room temperature for 20 hours the mixture was evaporated to give a gum. This material was redissolved in dry THF (400ml), cooled to -10°C, and treated with 2,6-lutidine (10.3ml) followed by thionyl chloride (6.95ml), dropwise over 5minutes, After stirring for 15 minutes at -10°C the mixture was diluted with dry toluene (400ml), filtered, and the residue was washed with dry toluene (100ml). The combined filtrates were evaporated and the residue was re-evaporated from dry toluene to give a gum. This material was dissolved in dry dioxan (200ml) and treated with triphenylphosphine (66.5g). The mixture was stirred until homogenous and evaporated to low volume (c¼ volume). The mixture was treated with 2,6-lutidine (8.2ml) and stirred at 40°C for 24 hours followed by 3 days at room temperature. The mixture was worked up as for Example 6(b) to give the title phosphorane (49) as a foam (43.7g); ʋ_max (CHCI₃) 1740, 1616 cm^-1.

Example 10(b)

Step B3

Silver (3S,4R) 3-[1-(R)-t-butyldimethylsilyloxvethyl]-1-[1- (4-methoxybenzyloxycarbonyl)-1-(triphenylphosphoranyl

idene)methyl]azetidin-2-one Silver nitrate (8.67ml of a 0.15M solution in methanol) was added to a stirred solution of the phosphorane from example 10(a)(941mg) and pyridine (0.105ml) in methanol (8ml) at room temperature. After stirring for 30 minutes the mixture was evaporated and the residue was triturated with dry ether (10ml) to give the title silver thiolate as a buff coloured solid.

Example 10(c)

Step B4

Methyl (Z)-2-chloro-3-(2-thienyl)prop-2-enoate

A mixture of 2-thiophenecarboxaldehyde (0.56g), methyl 1-chloro-1-triphenylphosphoranylideneacetate (G. Märkl, Chem. Ber.94, 2996, 1961)(1.84g), and dry dichloromethane (20ml) was stirred at room

temperature under argon for 3 days. A second portion of the phosphorane (0.55g) was added and the mixture stirred for a further 24 hours. The mixture was evaporated and the residue chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give the title ester as a solid (921mg); ʋ_max (CHCI₃) 1715, 1610 cm^-1; δppm (CDCI₃) 3.90 (3H,s), 7.15

(1H, dd, J5.1 and 3.7Hz), 7.61 (1H, d, J3.7Hz), 7.62 (1H, d, J5.1Hz), 8.15 (1H,s), other signals indicated the presence of c 10% of the E-isomer. [Found: M+, 202 (E.I.)].

Example 10(d)

Step B5

(Z)-2-Chloro-3-(2-thienyl)prop-2-enoic acid

A mixture of the ester from example 10(c)(763mg), aqueous sodium hydroxide (7.53ml of 1M), and dioxan (16ml) was stirred for 1 hour at room temperature. The mixture was evaporated to low volume and the precipitated solid was redissolved by addition of water (15ml). The mixture was washed with ethyl acetate (2ml). The pH of the stirred aqueous layer was adjusted to 2.0 using 5M hydrochloric acid and the mixture was worked up as for Example 9(b) to give the title acid as a solid (646mg); ʋ_max (CHCI₃) 3600-2200br, 1690, 1600 cm^-1, δppm [(CD₃)₂CO] 7.26 (1H, dd, J5.1 and 3.2Hz), 7.74 (1H, d, J 3.2Hz), 7.89 (1H, d, J5.1Hz), 8.29 (1H,s).

Example 10(e)

Step B6

(Z)-2-Chloro-3-(2-thienyl)prop-2-enoyl chloride

Dry dimethylformamide (1 drop) was added to a stirred mixture of the acid from example 10(d)(189mg), oxalyl chloride (0.13ml), and dry dichloromethane (3ml). After stirring at room temperature for 1½ hours the mixture was evaporated and the residue was re-evaporated from dry toluene to give the title acid chloride as a gummy solid; ʋ_max (CH₂CI₂)

1740 cm^-1.

Example 10(f)

Step B7

(3S,4R) 3-[1-((R)-t-Butyldimethylsilyloxyethyl]-4-[(Z)-2-chloro-3-(2-thienyl) prop-2-enoylthio]-1-[1-(4-methoxybenzyloxycarbonyl)-1-(triphenylphosphoranylidene) methyl]-azetidin-2-one A solution of the acid chloride from Example 10 (e) in dry dichloromethane

(2ml) was added, dropwise over 1 minute, to a stirred, ice bath cooled, solution of the silver thiolate [50, ex Example 10 (b)] and pyridine

(0.081ml) in dry dichloromethane (10ml). After stirring at ice bath temperature for 30 minutes the mixture was worked up as for Example 6(g) to give the title phosphorane as a yellow foam (453mg); ʋ_max (CHCI₃)

1745, 1655, 1610 cm^-1.

Example 10(g)

Step B8

4-Methoxybenzyl (5R,6S)-6-[1-(R)-t-butyldimethylsilyloxyethyl]-2-[(Z)-1-chloro-2-(2-thienyl)ethenyl]penem-3-carboxylate A solution of the phosphorane from example 10(f)(450mg) in dry toluene (225ml) was heated at reflux under dry argon for IV. hours. The mixture was worked up as for example 6(h) to give the title penem as a yellow gum (268mg); ʋ_max (CHCI₃) 1790, 1710 cm^-1; δppm (CDCI₃) 0.05 (3H,s), 0.07

(3H,s), 0.85 (9H,s), 1.24 (3H, d, J6.3Hz), 3.75-3.82 (4H, s+m), 4.20-4.29 (1H,m), 5.13 (2H,s), 5.64 (1H, d, J1.5Hz), 6.71-6.77 (2H,m), 7.06 (1H, dd, J5.1 and 3.7Hz), 7.20-7.26 (4H,m), 7.47 (1H, d, J5.1Hz). [Found: M+, 591 (E.I )].

Example 10(h)

Step B9

4-Methoxybenzyl (5R,6S)-2-[(Z)-1-chloro-2-(2-thienyl)

ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylate A mixture of the penem (55, 255mg), tetra-n-butylammonium fluoride trihydrate (406mg), glarial acetic acid (0.25ml), and dry THF (5ml) was stirred at room temperature for 28 hours. The mixture was worked up as for Example 1(b) to give, after chromatography on silica gel eluting with dichloromethane/ethyl acetate mixtures, the title penem (56) as a yellow solid (125mg); λ_max (EtOH) 341.5 (εm11,607), 288.5 (12,844), 274 (13,442) and 226.5nm (17496) ʋ_max (CHCI₃) 3650-3100, 1790, 1710cm^-1; δppm [(CD₃)₂CO] 1.30 (3H, d, J 6.3Hz), 3.76 (3H,s), 3.91 (1H, dd, J 6.2 and

1.7Hz), 4.13-4.25 (1H,m), 4.44 (1H, d, J 4.9Hz), 5.09 and 5.14 (2H, AA'q, J 12.2Hz), 5.82 (1H, d, J 1.7Hz), 6.75-6.80 (2H,m), 7.17 (1H, dd, J 5.1 and 3.8Hz), 7.24-7.28 (2H,m), 7.42 (1H, d, J3.8Hz), 7.45 (1H,s), 7.72 (1H, dd, J 5.1Hz). [Found: MNa⁺, 600 (3-nitrobenzyl alcohol/Na FAB)].

Example 10(i)

Step B10

Sodium (5R,6S)-2-[(Z)-1-chloro-2-(2-thienyl)ethenyl]-6-[1- (R)-hydroxyethyl]penem-3-carboxylate

A solution of the penem ester from example 10(h)(119mg) in dry

dichlorometnane (4ml) was added to a stirred mixture of aluminium chloride (freshly ground, 83mg), anisole (1.5ml), and dry dichloromethane (0.5ml) at -40°C. After δ minutes the cooling bath was removed and the mixture was treated with aqueous trisodium citrate (8.0ml of 0.5M). After stirring for 15 minutes the mixture was diluted with water (15ml) and dichloromethane (5ml), filtered through Kieselguhr, and the residue washed with water (5ml). The aqueous layer was separated from the combined filtrates, washed with dichloromethane (2×2ml), evaporated to low volume, and chromatographed on HP20SS eluting with THF/water mixtures. The appropriate fractions were concentrated and freeze dried to give the title penem as a yellow amorphous solid (41mg); ʋ_max (KBr) 3420 br,1763, 1609 cm^-1; δppm (D₂O) 1.28 (3H, d, J 6.5Hz), 3.97 (1H, dd, J 5.9 and 1.5Hz), 4.23 (1H, dq, J 5.9 and 6.5Hz), 5.72 (1H,d, J 1.5Hz), 7.14 (1H, dd, J 3.3 and 5.2Hz), 7.24(1H,s), 7.39 (1H, d, J 3.3Hz), 7.58 (1H, d, J 5.2Hz).

EXAMPLE 11(a)

2-(Tetrahydrofuran-2-yl)prop-2-enoic acid

Methyl-2-(tetrahydrofuran-2-yl)prop-2-enoate (1.3g) [known compound] in dioxan (30ml) was treated with 1M sodium hydroxide (20ml) and the mixture stirred at room temperature for 1hr. The dioxan was removed by evaporation and the aqueous solution washed with ethyl acetate. The resulting aqueous solution was acidified to pH 1.5 using 5M hydrochloric acid and the mixture extracted with ethyl acetate. After drying over anhydrous magnesium sulphate the organic solvent was evaporated to give the title acid as a colourless oil (1.1g); ʋ_max (CHCI₃) 1700 and

1635cm^-1; δppm (CDCI₃) 1.63-2.36 (4H, m), 3.83-4.05 (2H, m), 4.72 (1H, brt, J 6.7Hz), δ.98 (1H, brs), 6.36 (1H, brs).

EXAMPLE 11(b)

2-Tetrahydrofuran-2-yl)prop-2-enoyl chloride

A solution of the acid from example 11(a) (640mg) in dry dichloromethane

(10ml) was treated with oxalyl chloride (0.4ml) and dry

dimethylformamide (1 drop). After stirring at room temperature for

1.5hrs the resulting solution was evaporated and the residue re-evaporated from dry toluene to give the title acid chloride. ʋ_max

(CH₂CI₂) 1750, 1700 and 1680cm^-1.

EXAMPLE 11(c)

Step B7

(3S,4R)-3-[4(R)-t-butyldimethylsilyloxyethyl]-4-[2-(tetrahydrofuran-2-yl)prop-2-enoylthio]-1-[1-(4-methoxybenzyloxycarbonyl)-1-triphenylphosphoranylidene)methyl]azetidin-2-one

A solution of the acid chloride [ex. Example 1Kb)] in dry acetonitrile (10ml) was added, in one portion, to a stirred solution of the silver thiolate

[prepared on a 4mmole scale as in Example 10(b)] and pyridine (1ml) in dry acetonitrile (20ml) at ice bath temperature. After stirring at the bath temperature for lhr, the mixture was worked up as for Example 6(g) to give the title phosphorane as a pale yellow foam (1.33g). ʋ_max (CHCI₃) 1745, 1660 and 1615cm^-1; [Found: MH⁺, 824; MNa⁺ 846 (3-nitrobenzylalcohol/Na FAB)].

Example 11(d)

Step B8

4-Methoxybenzyl (5R,6S)-6-[1(R)-t-butyldimethylsilyloxyethyl]-2-[1-(tetrahydrofuran-2-yl)ethenyl]penem-3-carboxylate A solution of the phosphorane from Example 11(c) (1.3g) in dry toluene (500ml) was heated at reflux under dry argon for 60 hours. The mixture was worked up as for Example 6(h) to give the title penem (an ~1:1 mixture of diastereoisomers) as a light brown gum (0.74g); ʋ_max (CHCI₃)

1790, 1710 and 1605cm^-1; δ ppm (CDCI₃) (inter alia) 1.23 (3H, d, J

6.2Hz), 4.18-4.28 (1H, m), 4.52 and 4.65 (1H, 2 × br t), 5.26 and 5.32 (1H, 2 × br s), 5.45 and 5.52 (1H, 2 × br s), 5.58-5.60 (1H, m). [Found: M+, 545 (E.I.)].

Example 11(e)

Step B9

4-Methoxybenzyl (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(tetrahydrofuran-2- yl)ethenyl]penem-3-carboxylate

A mixture of the penem from example 11(d) (740mg), glacial acetic acid

(1ml), tetra-n-butylammonium fluoride trihydrate (1.5g) and dry THF

(15ml) was stirred at room temperature for 24hr. The mixture was worked-up as for Example 1(b) to give an ~1:1 mixture of

disastereoisomers of the title penem as a pale brown solid (0.47g); ʋ_max

(CHCI₃) 1790 and 1710cm^-1; δ ppm (CDCI₃) (inter alia), 1.35 (3H, d, J

6.29Hz), 3.65-3.95 (6H, m), 4.15-4.3 (1H, m), 4.50 and 4.61 (1H, 2 × br t), 5.24 and 5.29 (1H, 2 × br s), 5.43 and 5.50 (1H, 2 × br s). [Found: MNa⁺+, 454 (3-nitrobenzyl alcohol/Na FAB)].

Example 11(f)

Step B10

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(tetrahydrofuran-2-yl)ethenyl]penem-3-carboxylate

A solution of the penem ester from Example 11(e) (427mg) in dry dichloromethane (10ml) was added to a stirred mixture of powdered aluminium trichloride (400mg), anisole (16ml) and dry dichloromethane (8ml) at -40°C. After 30 minutes the cooling bath was removed, the mixture was treated with a solution of sodium bicarbonate (1.2g) in a 0.1M pH 7 solution of sodium, phosphate buffer (22ml) and the mixture stirred vigorously for a further 30 minutes. The solution was filtered through a short pad of celite and the pad washed with water. The aqueous layer was separated from the combined filtrates, washed with dichloromethane (2 × 20ml), evaporated to a low volume and

chromatographed on HP20SS eluting with THF-water mixtures. The appropriate fractions were concentrated and freeze dried to give the title penem (an - 1:1 mixture of diastereoisomers) as a white amorphous solid (240mg); ʋ_max (KBr) 1762 and 1603cm^-1. δ ppm (D₂O) 1.2δ (3H, d, J

6.4Hz), 1.75-2.16 (4H, m), 3.61-3.96 (3H, m), 4.14-4.27 (1H, m), 5.27 and 5.30 (1H, 2 × s), 5.37 and 5.39 (1H, 2 × s), 5.63-5.65 (1H, m).

Example 12(a)

Steps B11 and B12

Methyl 2-(isoxazol-3-yl)but-2-enoate

Lithium bis(trimethylsilyl) amide (10.0ml of a 1M solution in THF) was added to a stirred solution of methyl isoxazol-3-ylacetate (1.41g) in dry THF (30ml) at -76°C under dry argon. After 15 minutes at -76°C the mixture was treated with acetaldehyde (1.12ml), stirred for 15 minutes, and treated with acetic anhydride (1.88ml). The cooling bath was removed and the mixture was stirred for lhr. The mixture was treated with 1,8-diazabicyclo [5.4.0] undec-7-ene (3.0ml) and stirred at room temperature for a further 1 hour. The mixture was diluted with ethyl acetate (100ml) and was washed with 5% citric acid (2 x 10ml), brine (10ml), sat.d. NaHCθ3 (10ml), and brine (3 x 10ml). The dried (MgSθ4) organic layer was evaporated and the residue was chromatographed on silica gel eluting with ethyl acetate/hexane mixtures to give a 7:1 mixture of isomers of the title ester as an oil (1.27g); ʋ_max (film) 1722, 1648cm^-1; δppm (CDCl₃) 2.00 (⅞ CH₃, d, J 7.3Hz), 2.18 (⅛ CH₃, d, J 7.4Hz), 3.79 (⅞ CH₃, s), 3.85 (⅛ CH₃, s), 6.46-6.49 (1H, m), 6.93 (⅛ H, q, J 7.4Hz), 7.44 (⅞ H, q, J 7.3Hz), 8.35 (⅛ H, d, J 1.6Hz), 8.45 (⅞ H, d, J 1.8Hz).

Example 12(b)

Step B13

2-(Isoxazol-3-yl)but-2-enoic acid A mixture of the product from Example 12(a) (7:1 mixture of isomers,

1.27g), dioxan (30ml), and aqueous sodium hydroxide (1M, 15.2ml) was stirred at room temperature for 1 hour. The mixture was evaporated to low volume and was washed with ethyl acetate (5ml). The aqueous layer was partitioned with ethyl acetate (10ml) and the pH of the stirred mixture was adjusted to 2.0 using 5M hydrochloric acid. The organic layer was separated and the aqueous layer was re-extracted with ethyl acetate (10ml). The combined organic layers were washed with brine (3 × 3ml), dried (MgSO₄) and evaporated to give a 20:1 mixture of isomers of the title acid as a solid (968mg). Crystallisation from ethyl acetate/hexane provided a single isomer of the title acid (454mg), mp 115-116°C (rods); ʋ_max (CHCl₃) 3500-2200, 1697, 1639cm^-1; δppm (CDCI₃) 2.07 (3H, d, J

7.3Hz), 6.52 (1H, d, J 1.7Hz), 7.60 (1H, q, J 7.3Hz), 8.46 (1H, d, J 1.7Hz), 9.3-11.1 (1H, br s). (Found: C, 54.7; H, 4.7; N, 9.2. C₇H₇NO₃ requires C, 54.9; H, 4.6; N, 9.2%).

EXAMPLE 12(c)

Step B14

2-(Isoxazol-3-yl)but-2-enoyl chloride

Dry dimethylformamide (1 drop) was added to a stirred mixture of the acid from Example 12(b) (single isomer, 184mg), oxalyl chloride (0.16ml), and dry dichloromethane (5ml). After stirring at room temperature for 1 hour the mixture was evaporated and the residue re-evaporated from dry toluene (1ml) to give the title acid chloride as an oil; ʋ_max (CH₂CI₂)

1754cm^-1.

EXAMPLE 12(d)

Step B7

(3S,4R) 3-[1-(R)-t-Butyldimethylsilyloxyethyl]-4-[2-(isoxazol-3-yl)but-2-enoylthio]-1-[1-(4-methoxybenzyloxycarbonyl)-1-(triphenylphosphoranylidene)methyl]azetidin-2-one

A solution of the acid chloride from Example 12(c) in dry dichloromethane (1ml) was added, dropwise over 1 minute, to a stirred solution of the silver thiolate [prepared as in Example 10(b)] and pyridine (0.097ml) in dry dichloromethane (10ml) at ice bath temperature. After stirring at ice bath temperature for 30 minutes the mixture was worked up as for Example 6(g) to give the title phosphorane (306mg) as a foam; ʋ_max (CHCI₃) 1749,

1666, 1614cm^-1.

EXAMPLE 12(e)

Step B8

4-Methoxybenzyl (5R ,6S)-6-[1-(R )-t-butyldimethylsilyloxyethyl]-2-[1- (isoxazol-3-yl)prop-1-en-1-yl[penem-3-carboxylate

A solution of the phosphorane from Example 12(d) (306mg) in dry toluene (150ml) was heated at reflux under dry argon for 48 hours. The mixture was worked up as for Example 6(h) to give two fractions. The first fraction provided the less polar geometric isomer of the title penem (29mg) as a gum; ʋ_max (CHCI₃) 1786, 1708cm^-1; δppm (CDCI₃) 0.03 (3H, s), 0.06

(3H, s), 0.84 (9H, s), 1.24 (3H, d, J 7.3Hz), 1.96 (3H, d, J 7.3Hz), 3.75 (1H, dd, J4.8 and 1.5Hz), 3.79 (3H, s), 4.23 (1H, dq, J4.8 and 7.3Hz), 5.01 (2H, s), 5.62 (1H, d, J 1.5Hz), 6.29 (1H, d, J 1.5Hz), 6.32 (1H, q, J 7.3Hz), 6.80-6.87 (2H, m), 7.20-7.25 (2H, m), 8.34 (1H, d, J 1.5Hz); [Found: MNa⁺ 579 (3-nitrobenzyl alcohol/Na FAB)]. The second fraction provided the more polar geometric isomer of the title penem (102mg) as a gum; ʋ_max

(CHCI₃) 1788, 1711cm^-1; δppm (CDCI₃) 0.05 (3H, s), 0.07 (3H, s), 0.85

(9H, s), 1.25 (3H, d, J 6.2Hz), 1.85 (3H, d, J 7.0Hz), 3.80-3.82 (4H, m), 4.21-4.30 (1H, m), 5.04 (2H, s), 5.76 (1H, d, J 1.6Hz), 6.32 (1H, d, J

1.8Hz), 6.44 (1H, q, J 7.0Hz), 6.79-6.86 (2H, m), 7.17-7.23 (2H, m), 8.29 (1H, d, J 1.8Hz); [Found: MNa+ 579 (3-nitrobenzyl alcohol/Na FAB)].

EXAMPLE 12(f)

Step g9

4-Methoxybenzyl (5R,6S) 6-[1-(R)-hydroxyethyl]-2-[1-(isoxazol-3-yl)prop-1-en-1-yl]penem-3-carboxylate

A mixture of the more polar geometric isomer of the penem from Example 12(e) (196mg), glacial acetic acid (0.20ml), dry THF (3ml), and tetra-n-butylammonium fluoride trihydrate (332mg) was stirred at room

temperature for 19 hours. The mixture was worked up as for Example Kb) to give the title penem ester (128mg) as a foam; ʋ_max (CHCI₃) 3800- 3200, 1789, 1709cm^-1; δppm (CDCI₃) 1.36 (3H, d, J 6.3Hz), 1.82 (3H, d, J

7.0Hz), 2.1-2.6 (1H, br s), 3.79 (3H, s), 3.85 (1H, dd, J 6.5 and 1.6Hz), 4.26 (1H, dq, J 6.5 and 6.3Hz), 5.00 and 5.08 (2H, ABq, J 12.1Hz), 5.81 (1H, d, J 1.6Hz), 6.28 (1H, d, J 1.8Hz), 6.41 (1H, q, J 7.0Hz), 6.79-6.84 (2H, m), 7.14-7.19 (2H, m), 8.28 (1H, d, J 1.8Hz); [Found: MNa+ 465 (3- nitrobenzylalcohol/Na FAB)].

EXAMPLE 12(g)

Step B10

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(isoxazol-3-yl)prop-1-en-1- yl]penem-3-carboxylate

A solution of the penem ester from Example 12(f) (125mg) in dry

dichloromethane (2ml) was added to a stirred mixture of aluminium chloride (94mg), anisole (1.5ml), and dry dichloromethane (0.5ml) at -

40°C. After 15 minutes the cooling bath was removed and the mixture was treateci with aqueous trisodium citrate (8.0 and 0.5M). The mixture was worked up as for Example 10(i) to give the title penem (55mg) as an amorphous solid; λ _max (H₂O) 309mn (εm 4159); ʋ_max (KBr) 3398br,

1763, 1602, 1576cm^-1; δppm (D₂O) 1.29 (3H, d, J6.4Hz), 1.87 (3H, d, J

7.1Hz), 3.97 (1H, d, J 6.0Hz), 4.25 (1H, dq, J 6.0 and 6.4Hz), 5.80 (1H, s), 6.58 (1H, q, J 7.1Hz), 6.66 (1H, d, J 1.6Hz), 8.49 (1H, d, J 1.6Hz). EXAMPLE 13

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(2-methylthiazol-4-yl)prop-1-en-1-ylpenem-3-carboxylate Using the route and methods described in Examples 12(a) to 12(g) methyl 2-methylthiazol-4-ylacetate was converted to a geometric isomer of the title penem; λ _max (H₂O) 307 (εm 4085) and 248nm (9256); ʋ_max (KBr)

3405br, 1766, 1604, 1576cm^-1; δppm (D₂O) 1.29 (3H, d, J6.4Hz), 1.81 (3H, d, J 7.1Hz), 2.64 (3H, s), 3.94 (1H, dd, J 5.9 and 1.3Hz), 4.24 (1H, dq, J 6.4 and 5.9Hz), 5.78 (1H, d, J 1.3Hz), 6.50 (1H, q, J 7.1Hz), 7.13 (1H, s). EXAMPLE 14

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(thiazol-2-yl)prop-1-en-1-yl]penem-3-carboxylate

Using the routes and methods described in examples 8(a) to 8(c) and 12(d) to 12(g) 2-acetylthiazole was converted to a 3:2 mixture of geometric isomers of the title penem; λ_max (H₂O) 364 (3m 7760) and 295nm (8440); ʋ_max (KBr) 3384 br, 1763, 1696cm^-1; δppm (D₂0) 1.22 (1.2H, d, J 6.4Hz), 1.30 (1.8H, d, J 6.4Hz), 2.24 (1.2H, d, J 1.2Hz), 2.34 (1.8H, br s), 3.78 (0.4H, dd, J 5.9 and 1.3Hz), 3.94 (0.6H, dd, J 5.9 and 1.3Hz), 4.13-4.30 (1H, m), 5.60 (0.4H, d, J 1.3Hz), 5.69 (0.6H, d, J 1.3Hz), 6.94-6.95 (0.4H, m), 7.51 (0.6H, d, J 3.3Hz), 7.68 (0.4H, d, J 3.4Hz), 7.76 (0.6H, d, J 3.3Hz), 7.81-7.82 (1H, m).

E)(AMPLE 15

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(5-methylisoxazol-3-yl)prop-1-en-1-yl]penem-3-carboxylate

Using the route and methods described in Examples 12(a) to 12(g) methyl

5-methylthiazol-3-ylacetate was converted to a geometric isomer of the title penem; λ_max (H₂O) 307nm (εm 3692); ʋ_max (KBr) 3409, 1762, 1604,

1675cm^-1; δppm (D₂O) 1.28 (3H, d, J 6.4Hz), 1.84 (3H, d, J 7.1Hz), 2.36 (3H, s), 3.96 (1H, dd, J 6.0 and 1.1Hz), 4.24 (1H, dq, J 6.4 and 6.0Hz), 5.78 (1H, d, J 1.1Hz), 6.30 (1H, s), 6.50 (1H, q, J 7.1Hz).

EXAMPLE 16 Sodium (5R,6S) 2-[2-(2-furyl)prop-1-en-1-yl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylate

Using the routes and methods described in Examples 8(a) to 8(c) and 12(d) to 12(g) 2-acetylfuran was converted to a 1:1 mixture of (E) and (Z) isomers of the title penem; ʋ_max (KBr) 3409 br, 1762, 1589cm^-1; δppm (D₂O) 1.25 and 1.29 (3H, each d, J 6.4Hz), 2.10 (1.5H, d, J 1.4Hz), 2.17 (1.5H, d, J 1.3Hz), 3.79 (0.5H, dd, J 6.0 and 1.3Hz), 3.87 (0.5H, dd, J 5.9 and 1.4Hz), 4.15-4.29 (1H, m), 5.54 (0.5H, d, J 1.3Hz), 5.63 (0.5H, d, J 1.4Hz), 6.49 (2.5H, m), 7.48-7.56 (1.5H, m). EXAMPLE 17

Sodium (5R,6S) 2-[1-chloro-2-(1-methyl-1,2,3-triazol-4-yl)ethenyl]-6-[1- (R)-hydroxyethyl]penem-3-carboxylate

Using the route and methods described in Examples 10(c) to 10(i) 1- methyl-1,2,3-triazoIe-4-carbaldehyde was converted to a single geometric isomer of the title penem; λ_max (H ₂O) 335 (εm 3949), 276 sh (6319), and

254 nm (6919); ʋ_max (KBr) 3395 br, 1762, 1610cm^-1; δppm (D20) 1.28

(3H, d, J 6.4Hz), 4.01 (1H, dd, J 5.8 and 1.4Hz), 4.11 (3H, s), 4.24 (1H, dq, J 6.4 and 5.8Hz), 5.7δ (1H, d, J 1.4Hz), 7.02 (1H, s), 8.49 (1H, s).

EXAMPLE 18

Sodium (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E-2-(1,2,3-thiadizaol-4-yl)ethenynpenem-3-carboxylate

Using the route and methods described in Examples 5(a) to 5(c) 4-formyl-1,2,3-thiadiazole was converted to the title penem; δppm (D₂O) 1.31 (3H, d, J 6.4Hz), 3.94 (1H, dd, J 5.7 and 1.0Hz), 4.27 (1H, dq, J 6.4 and 5.7Hz), 5.67 (1H, d, J 1.0Hz), 7.08 (1H, d, J 16.2Hz), 8.24 (1H, d, J 16.2Hz), 9.00 (1H, s).

Claims

1. A penem compound having a formula (I):

R⁴ is C_1-6 alkyl,

R⁵ is H or a hydroxy-protecting group,

R⁶ is H, or salt-forming cation or an ester-forming group.

2. A penem compound according to claim 1 wherein the heterocyclic group R¹, R² or R³ is selected from unsubstituted or substituted triazolyl, furyl, thienyl, thiazolyl, isothiazolyl and pyrazolyl.

3. A penem compound according to claim 2 wherein the heterocyclic group R¹, R² or R³ is substituted with C_1-6 alkyl.

4. A penem compound according to any one of claims 1, 2 or 3 wherein those of R¹, R² or R³ which are not the heterocyclic group are selected from hydrogen, methyl or halogen.

5. A penem compound according to any one of claims 1 to 4 being a compound of formula IA, or pharmaceutically acceptable salts or pharmaceutically acceptable in vivo hydrolysable esters thereof:

6. A penem compound according to claim 5, being selected from the following acids, and pharmaceutically acceptable salts or

pharmaceutically acceptable in vivo hydrolysable esters thereof:

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(1-methyl-1,2,3-triazo-4- yl)ethenyl]penem-3-carboxylic acid,

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(4-methylthiazol-δ-yl)ethenyl]penem- 3-carboxyIic acid,

(5R,6S)-2-[2-(2-furyl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylic acid,

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(isothiazol-5yl)-ethenyl]penem-3- carboxylic acid, (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)ethenyl]-penem-3-carboxylic acid,

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(methylpyrazol-4-yI)ethenyl]penem-3-carboxylic acid,

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E)-1-(1-methyl-1,2,3-triazol-4-yl)prop-1-en-2-yl]penem-3-carboxylic acid, (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(2-thienyl)-prop-1-en-1-yl]penem-3-carboxylic acid,

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(2-thienyl)prop-1-en-1-yl]penem-3-carboxylic acid,

(5R,6S)-2-[1-(Z)-chloro-2-(2-thienyl)ethenyl]-6-[1-(R)hydroxyethyl]penem-3-carboxylic acid (5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(tetrahydrofuran-2-yl)ethenyl]penem-3-carboxylic acid

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(isoxazol-3-yl)prop-1-en-1-yl]penem-3-carboxylic acid

(5R,6S) 6-[1-(R)-hychoxyethyl]-2-[1-(2-methylthiazol-4-yl)prop-1-en-1-ylpenem-3-carboxylic acid

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[2-(thiazol-2-yl)prop-1-en-1-yl]penem-3-carboxylic acid

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[1-(6-methylisoxazol-3-yl)prop-1-en-1-yl]penem-3-carboxylic acid (5R,6S) 2-[2-(2-furyl)prop-1-en-1-yl]-6-[1-(β)-hydroxyethyl]penem-3-carboxylic acid

(5R,6S) 2-[1-chloro-2-(1-methyl-1,2,3-triazol-4-yl)ethenyl]-6-[1-(R)-hydroxyethyl]penem-3-carboxylic acid

(5R,6S)-6-[1-(R)-hydroxyethyl]-2-[(E-2-(l,2,3-thiadizaol-4-yl)ethenyl]penem-3-carboxylic acid

7. A penem compound according to claim 1 substantially as

hereinbefore described with reference to any one of the examples 1 to 10.

8. A process for the preparation of a compound of formula I as defined in claim 1 above, from a compound of formula IB:

(i) removing any further protecting groups,

(ii) converting the group CO₂R⁶ into a different group CO₂R⁶,

(hi) converting the group OR⁵ into a different group OR⁵. (iv) converting the compound into a pharmaceutically acceptable salt or ester.

9. A process for the preparation of a compound of formula (I) in which a compound of formula (II):

s reacted with a compound of formula (III):

(i) removing any protecting groups,

(ii) converting the group CO₂R⁶ into a different group CO₂R⁶, (in) converting the group OR⁵ into a different group OR⁵,

(iv) converting the product into a pharmaceutically acceptable salt or ester.

10. A process for the preparation of a compound of formula I, in which an azetidinone compound of formula IV:

is cyclised, wherein;

R¹, R², R³, R⁴, R⁵ and R⁶ are as defined with respect to formula I; R⁹ denotes an O or S atom or a group PR₃ where R is an organic group, R¹⁰ denotes a phosphoranylidene group, =C(CH₃)₂, or O; and thereafter if necessary or desired carrying out one or more of the following steps:

(i) removing any protecting groups,

(ii) converting the group CO₂R⁶ into a different group CO₂R⁶,

11. A compound of formula (II)) or (IIA):

wherein R³, R⁴, R⁵, and R⁶ are as defined with respect to formula (I), X is a phosphorane group of general formula PR₃ where R is an organic group, and Z- is a counter-anion.

12. A compound of formula (IV):

wherein;

R¹, R², R³ , R⁴, R⁵ and R⁶ are as defined with respect to formula I;

R⁹ denotes an O or S atom or a group PR₃ where R is an organic group, R¹⁰ denotes a phosphoranylidene group =C(CH₃)₂, or O.

13. A compound of formula (II), (IIA) or (IV) according to claim 11 or 12 in which R is aryl or alkoxy, and Z- is a halide anion.

14. A compound as claimed in any one of claims 11 or 12 or 13, substantially as hereinbefore described with reference to any one of examples 1 to 10.

15. A pharmaceutical composition which comprises a compound of formula (I) as defined in claim 1, and a pharmaceutical carrier.

16. A compound of formula (I) as defined in claim 1 or a

17. A compound of formula (I) as defined in claim 1 or a

pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, for use in the treatment of bacterial infections.

18. A method of treating bacterial infections in humans and animals which comprises the administration of a therapeutically effective amount of an antibiotic compound of the formula (I) as defined in claim 1 or a pharmaceutically acceptable in vivo hydrolysable ester thereof.

19. The use of a compound of formula (la) as defined in claim 5 or a pharmaceutically acceptable salt or in vivo hydrolysable ester thereof, in the manufacture of a medicament for the treatment of bacterial infections.