CHEMICAL INTERMEDIATES

This invention relates to a class of intermediates useful for the preparation of antibactierially active penicillin derivatives, in particular 6oE-methoxy penicillin having a carboxylic acid function at the 2-position in the side-chain. The invention also relates to a process for the preparation of the novel intermediates and to a process for their conversion to the penicillin.

British Patent Specification No. 1,463,468 discloses a process for the preparation of 6-alkoxy penicillins which comprises reacting a 2-hydroxyor 2-halo-penìciïlinwith a halogenating agent to form a 2,3-dihaloimine and subsequently reacting this with an alkali metal alkoxide to give a 6-alkoxyketenimine which is hydrated to give the required product. One disadvantage of this process is that the 2-hydroxyor 2-halo-penicillin starting material must be prepared by acylation of 6-amino penicillanic acid with the corresponding side-chain.

The process does not provide a method for the introduction of a 6¢-alkoxy substituent directly into a 6-acylaminopenicillin.

Furthermore in the above process the 2,3-dihaloimine intermediate must be isolated in order to remove excess halogenating agent (such as phosphorus pentachloride) therefroeprior to treatment with the alkali metal alkoxide.

However in the case of a penicillin derivative having a carboxylic acid function at the 2-position, the dihaloimine is thermally unstable and the process is therefore unsuitable for that class of penicillins 10S0698 The present invention is concerned with a process which enables 2-carboxy acetamido penicillin derivatives to be converted into their 6oE-methoxy analogues. The key intermediates for this process are novel ketenimines.

Accordingly the present invention provides a ketenimine of formula (1):

H_ CH3 R0 ct !o 2RI O2112 (I) i0 wherein R represents a furyl, thienyl, cycloalkyl, cycloalkenyl or phenyl group, or a phenyl group substituted with ' Zrom 1 to 3 hydroxy, halogen, nitro, CI-C6 alkyl, C1-C6 alkoxy, amino or carboxy groups:

RI represents on ester-forming radical: and R2 represents an i nyivohydrolysable ester forming radical or a carbonyl-blocking group.

Suitable groups R include 2and 3f ryl, 2and 3-thienyl, cyclopropyl, cyclobutyl, Cyclopentyl, cyclohexyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, 3-chloro-4-hydroxyphenyl, 3,4-hydroxyphenyl.

Most suitably R is 2or 3-thienyl, phenyl or 4-hydroxyphenyl: preferably phenyl.

I..nnvivo hydrolysable pharmaceutically acceptable ester forming radicals for the group R2 are those which, when attached at that position on a penicillin nucleus, i0 10S069S hydrolyse readily in the human body to produce the parent acid. It is well esta 51ished that simple alkyl and aryl esters of penicillins fail to meet this requirement as they are resistant to hydrolysis by human tissues.

Examples of suitable in vivo hydrolysable ester radicals for the group R2 include acyloxyalkyl groups such as acetoxymethyl, pivaloyloxymethyl, OE-acetoxyethyl, OE-acetoxybenzyl and =-pivaloyloxyethyl groups: alkoxycarbonyloxyalkyl g oup s c as 9th0xycarbonylgxymethyl and =-ethoxycarbonyloxyethyl: and lactone, thiolactone and dithiolactone groups, i.e. ester groups of formula:

- CO.O. - CH - Z' I I X' - C = Y' i wherein X' and Y' are oxygen or sulphur and Z' is an ethylene group or a 1,2-phenylene group optionally substituted by lower-alkoxy, halogen or nitro.

Preferred ester groups are the phthalide and 5,6d met yphthalide esters.

Suitable carbonyl-blocking derivatives for the group R2 in formula (I), include salts, ester, and anhydride derivatives of the carboxylic acid. The derivative Should be one which may readily be cleaved at a later stage of the reaction. Suitable salts include tertiary amine salts, such as those with tri-loweralkylamines. N-ethyl-piperidine, 2,6-1utidine, pyridine, N-methylpyrrolidine, dimethylpiparazine. A preferred sali is with triethylamine.

Suitable carbonyl-blocked groups of formula C02 2 include the following:

(i} -C00CRcRdRe wherein at least one of Rc, Rd i0 and R is an electron-donor e.g. p-methoxye phenyl, 2,4 ° 6-trìmethylphenyl, 9-anthryl, methoxy, acetoxy, methoxymethyl, benzyl or fur-2-yl. The remaining Rc, Rd and Re groups may be hydrogen or organic substituting groups. Suitable ester groups of this type include -methoxybenzyloxy-carbonyl, 2,4,5trimethylbenzyloxy carbonyl, bis- ( -methoxyphenyl)methoxycarbonyl, 3,5-di-t-butyl-4hydroxybenzyloxycarbonyl, methoxymethoxycarbonyl and benzyloxycarbonyl.

(it} -C00CRcRdRe wherein at least one of Rc, Rd and R is an election-attracting group e.g.

e benzoyl, p-nitrophenyl, 4-pyridyl, trichloromethyl, tribromomethyl, iodomethyl, cyanomethyl, ethoxycarbonylmethyl, arylsulphonylmethyl, 2dimethylsulphoniumethyl, o-nitrophenyl or cyano.

The remaining Rc, Rd and Re groups may be hydrogen or organic substituting groups.

Suitable esters of this type include nzoylmethoxycarbonyl, p-nitrobenzyloxycarbonyl, 4-pyridylmeth0xycarb0nyl, 2,2,2-trichloroethoxycarbonyl and 2,2,2-tribromoethoxycarbonyl.

(iii) -C00CRCR e wherein at least two of Rc» Rd and R are hydrocarbooe such as alkyl e.g. methyl e or ethyl, aryl, e.g. phenyl and the remaining Rc, Rand Re group, if there is one, is hydrogen.

Suitable esters of this type include t-butyli0 oxycarbonée, t-am¥1ŒExycarbonyl. diphenylmethoxycarbonyl and triphenylmethoxycarbonyl.

(iv) -C00CRf wherein Rf is adamantyl, 2-benzyloxyphenyl, 4-methylthiophenyl, tetrahydrofur-2-yltetrahydropyran-2-yl æ pentachlorophenyl (v) Silyloxycarbonyl groups obtained by reaction of a silylating agent as described above with the carboxylic acid group (vi) COcP°Ra wherein Ra is an alkyl, haloalkyl, aryl, aralkyl, alkoxy, haloalkoxy, aryloxy, aralkyloxy or dialkylamino group, is the same as Ra or is halogen or Ra and together forma ring.

The carbonyl group may be regenerated from any of the above esters by usual methods for example, acid - and base - catalysed hydrolysis, or by enzymically - catalysed hydrolysis'. Alternative methods of cleavage include:

reaction with Lewis acids, such as trifluoroacetÆc acid, formic acid, hydrochloric acid in acetic acid, zinc br0mi-de-in benzene.and aqueous .sõlutionaì0r suspensions of" mercuric compounds. (The reaction with the Lewis acid may be facilitated by addition of a nucleophile such as anisole) reduction with agents such as zinc/acetic acidæ zlnc/formic acid, zinc/lower alcohol, zinc/pyridine, palladised-charcoal and hydrogen, and sodium and liquid amnonia7 attack by nucleophiles, such as those containing a nucleophilic oxygen or sulphur atom for example alcohols, mercaptans and water oxidative methods, i0 for example, those which involve the use of hydrogen peroxide and acetic acid: and irradiation.

The group R1 may be any ester-forming radical as hydrolysis to the free acid at that position is not essential for the activity of the eventually produced penicillin derivative. The group R1 may therefore be any of the radicals described above as being i_.nnvivo hydrolysable when present at the 3-position of the penicillin nucleus: or it be any of the above-mentioned carbonyl-blocking groups.

In addition the group R1 may be an alkyl, cycloalkyl, alkenyl, alkynyl, aryl, or heterocyclic group any of which maybe substituted. Suitable such groupsimclude:

(a) alkyl especially CI_6 alkyl such as methyl, ethyl, - andiso-propyl, -, sec-, is0and t ert-butyl, and pentyl:

(b) substituted C1 _6 alkyl wherein the substituent is at least one of: chloro, bromo, fluoro, nitro, carbon (CI_6 alkoxy), CI_6 alkanoyl, CI_6 aiko il cyano, CI_6 alkylmer?apto< (CI_6 alkyîsulfinyl, CI 6 alkylsulph nyl,l-indanyl;-2-ïndany1, furyl, pyridyl,., 4-imldäZ01rl, phthalimido, azetïdïnõl aziridino, ....

pyrroli no, piperidino, morpholino, thi0morPholino, N-(C1_6Ne-(Cl_6ïalkyl)p0, çyrrolo,. imidazolo, 2" imida glino, 2,5-dimethylpyrrolidino, 1,4,5,6.• tetrahydropyrimidino, 4-methylpiperidino, 2,6d!methylpiperidino, alkylamino, dialkylamìno, alkanoylamino, N-alkylanilino, of substituted Nalkylanilino wherein the substituent is chloro, 2S bromo, CI_6 alkyl or C1 _6 alkoxy:

(c) cycloalkyl and (CI_6 alkyl) substituted cycloalkyl having from 3 to 7 carbon atoms in the cycloalkyl moiety:

(d) alkenyl having up to 8 carbon atoms:

(e) alkynyl having up to 8 carbon atoms:

(f) phenyl and substituted phenyl wherein the substituent is at least one of chloro, bromo, fluoro, C1_6 alkoxy, C1 _6 alkanoyl, carbo-(C1 _6 )alkoxy, nitro, or di(C1 _6 )alkyl amino:

(g) bénzyl or substituted benzyl wherein the substituent is chloro, promo, fluoro, CI_6 alkyl, C1 _6 alkoxy,C1 alkanoyl carbo(C1_6)a koxy, nitro, or di(C1 _6 )alkyamino:

(h) heterocyclic groups such as: furyl, quinolyl, methyl-substituted quinolyl, phenazinyl, 1,3benzodioxolyl, 3- ( 2-methyl-e-pyr0 ny1 ), 3pyronyÆ) or methylpyridyl (i) other hydrocarbyl groups such as: ac - indanyl and substituted derivatives thereof wherein the substituent is methyl, chloro or bromo: ac - tetrahydronaphthyl and substituted derivatives thereof wherein the substituent is methyl, c hloro or promo: benzohydryl, trityl, cholesteryl, or' bicyclo[4.4.0]decyl.

Preferred groups for R1 include C1 _6 alkyl, benzyl, phthalidyl, indanyl, phenyl, mono-, di-, and tri- (CI.C6 )- alkyl substitútedphenyl such as o_-, m or - methylphenyl, ethylphenyl, n_or isopropylphenyl, n_-, sec-, isoor tbutyiphenyl.

î080698 The intermediates of formula (I) may be prepared by reacting a 6-acylaminopenÆcillin of formula (II):

R.CH.CO.NH O2RI H 2R2 (II) wherein R, RI and R2 , are as defined with respect to formula (I) above: with an acid halide.

Suitably the reaction with acid halide is carried out in the presence of an acid binding agent such as a tertary amine, e.g. pyridine, triethylamine or N,Ndimethylaniline.

Examples of suitable acid halides are phosphorus pentachloride, phosgene, phosphorous pentabromìde, phosphorus oxychloride, oxalyl chloride and p-toluene sulphonic acid chloride. Phosphorus pentachloride and phosphorus oxychloride are preferred. The reaction may be conducted under cooling, preferably at temperatures from +5°C to -30€ (preferably about 0°C) when phosphorus pentachloride is employed. The amount of the tertiary amine is preferably 3-5 mols per mol of phosphorus pentachloride. If is also preferable to use the phosphorus halide in an amount in excess of that of the starting material.

The value of the ketenimine compounds of formula (i) derives from their use in the preparation of 6-methoxypenicillins.

. L .

i % î080698 Thus in a further aspect, the present invention provides a process for preparing a compound of formula (III):

R.CH.CO.NH O2R3 OCH N'02 R4 (III) i0 wherein R is as defined above with respect to formula (I) above:

R3 represents hydrogen, a pharmaceutically acceptably salt forming ion or a pharmaceutically acceptable ester-forming radical: and R4 represents hydrogen, a pharmaceutically acceptable salt-forming ion or in vivo hydrolysable ester-forming radical; which process comprises:

(a) reactíng a ketenimine of formula (I) with a double-bond addition reagent:

(b) reacting the resulting product with a compound Of formula CH3 OM, wherein M is an alkali metal or thallium:

(c) hydrolysing the resulting product:

(d) removing any carbonyl-blõcking groups: and (e) optionally salifying or esterifying any free carboxylic acid group.

Suitable salt-forming ions for the groups R3 and R4 include metal ions e.g. aluminium, alkali metal ions such as sodium or potassium, alkaline earth metal ions such as calcium or magnesium, and ammonium or î08069 substituted ammonium ions for example those from lower alkylamines, such as triethylamine, hydroxy-lower alkylamines such as 2-hydroxyethylamine, bis-(2hydroxyethyl )-amine or tri-( 2-hydroxyethyl )-amoEne, cycloalkyamines such as dicyclohexylamine, or from procaine, dibenzylamine, N,N-dibenzylethylenediamine, l-ephenamine, N-ethylpiperidine, N-benzyl-8-phenethylamine, dehydroabi etyl nê' N, N'-bi s-dehydro abi etyl ethyl enedi amine, or bases of the pyridine type such as pyridine, collidine or quinoline, or other amines which have been used to form salts with benzylpenicillin.

The double bond addition reagent is a difunctional moiety where each of the groups can be displaced by nucleophiles.

Suitable double bond addition reagents for the above process include diatomic halogen molecules or a compound of formula Er.N3 ° If the double-bond addition reagent is designated X-Y, the adduct formed has the formula (IV):

X Y I I R - Ci - C1 = N ------'/f'Sx4--- / O CO2R 2R2 (zv) Suitably both X and Y are halogen, preferably chlorine, as the reaction proceeds more smoothly.

The reaction is suitably carried out in an inert solvent, such as tetrahydrofuran or a halogenated -Iii0 hydrocarbon e.g. chloroform, at low temperatures such as +20 °C to -1 O0 °C preferably -50 °C to -80 °C, e.g.

at about -70 °C.

The compound of formula (IV) is thenreacted with an alkali metal or thallium methoxide of formula CH3 OM.

Suitably M may be sodium or potassium, but is preferably lithium. The reaction is generally carried out in a polar aprotic solvent, preferably methanol, preferably in the presence of another inert solvent, such as tetrahydrofuran as long as it as it does not freeze ãt the temperature of the reaction. The reaction is suitably carried out at low temperature, preferably in the range -40 °C to80°C, preferably about-75°C. Thereagent CH3 0M may be formed in situ by the use of methanol together with a base such as butyl lithium, lithium diisopropylamide, lithium or sodium hydride or preferably butyl lithium. Preferably the steps (a) and (b) above are carried out without the isolation of the compound (IV).

The thus produced 6 -methoxy ketenimine of formula (V) : .0CH3 : S R " i" " C" = "" ïj02 R1 ,N" (V) is then hydrolyse.

Preferably this hydrolysis is carried out at a pH in the range 1 to 5 preferably pH2 to 4, at ambient temperature. Suitable solvents inclüde tetrahydrofuran or acetone. -12 ' v B Ketenimines of formulae (I) and (V) are novel compounds and the preferred group of these compounds has the general formula Z R - C = C = N O NI 1 CO2R N wherein Z is hydrogen or -OCH3 ; R represents 2-thienyl, 3-thienyl, phenyl or 4-hydroxyphenyl; -COR1 represents an esterifÆed ŒE-earboxy group but when Z is -OCH3 , R1 is not alkyl; and R2 represents an in vivo hydrolysable ester-forming radical or a carboxy-blocking group. The methods of preparation of these novel intermediates have already been described.

The ketenimine compounds of formula (I) are also useful intermediates for the preparation of other 6-substituted penicillins.

k -12aThus a compound of formula (VI):

SCH3 (vi) [wherein R, RI and R2 , are as defined with respect to formula (I)] may be prepared by:

(a) reacting a ketenimine of formula (I) with a compound of formula MeS-Z, wherein Z is a readily displaceable group: to produce a compound of formula (VII):

S-CH3 CO2R2 (VII): and (b) hydrolysing the compound offormula (VII) to produce a 6-methylthio penicillin, of formula (VI).

A suitable readily displaceable group Z is the group -SO2 CH3 , and the reaction of compound (I) with compound MeS-z is generally carried out at low temperature, suitably in the».range +5°C to -30°C, preferably about 0°C.

The thiomethyl penicillins of formula (VI) are themselves useful intermediates for the preparation of other 6-substituted penicillins, including the methoxysubstituted compounds (III), by methods known in the X080698 art, for example by treatment with mercuric chloride and methanol.

The following examples illustrate the preparation of a ketenìmine intermediate of this invention and its use in preparing antibacterially active penicillins.

"Carfecillin" is the penicillin of formula:

Ph - CH - I C02Ph CO.NH SS Examp!el Preparation of p-nitrobenzyl 6 -(2'-phgnyl-2'-phenoxYcarbony1)Ketenimino penicillanate.

p-Nitrobenzyl 6 -(2'-phenyl-2'-phenoxycarbonyl)acetamido penicillanate (l.50g., 2.54mmoi) in benzene (6ml) was treated with pyridine (1.68ml), added at0°C. Phosphorus pentachloride (1.32g., 6.36mmoi) in benzene (30ml) was slowly added, with stirring at 0°C. After three hours at 0°C, the solution was filtered. The solids were washed with ether, and the combíned organic layers washed successively with water and sodium bicarbonate solution, dried (Na2 S04 ) and evaporated to give almost pure title compound (1.23., 85%), max (CHC13 ) 2030, 1790, 1740, 1600, 1530, 1350cm-I.

8 (CDC13 ) 1.36, 1.42, (6H, 2s, (CH3 )2 C), 4.56 (IH,s,C3proton), 5.43 (2H,s,,CH2 -), 5.77 (2H,s,C5 and C6 -protons), 7.1-7.9 (12H, complex, aryl protons), 8.37 (2H,d,J. 8Hz., -CH-CNO2-).

[Hydrolysis of the title Ketenimine (aqueous T.H.F.:

phosphoric acid) at pH 4 over 24 hours, followed by addition of ethyl acetate, which was washed with water dried (Na2 SO4) and evaporated, afforded starting p-nitrobenzyl 6 -(2'-phenyl-2'-phenoxycarbonyl)acetàmido penicillanate only with no trace of the 6a-epimer.] Example 2.

Preparation of p-nitrobenzyl 6oE-methoxy-6Ç-(2'-phenyl-2'- phenoxycarbonyl) Ketenimino penicillanate.

Method (i) (a) p-Nitrobenzyl-6Ç-(l',2', dichloro-2'-pheny!-2'- phenoxycarbonyl)ethylid@neamino penicillanate.

The Ketenimine from example 1 (0.17g., 0.3mmol) in chloroform (3ml) at O°C was treated dropwise over 30 minutes with chlorine in chloroform until disappearance of max (CHC13) 2030cm-1, concomitant with appearance of max (CHC13) 1670cm-I. After evaporation, the title product was obtained.

i i (b) p-Nitrobenzyl 6oErmçthoxv-68-(2'-Dhenv1-2'-DhenoxvÇar ny!)Ketenimino penicillanate.

The imino chloride from(a) above was intermediately used in (b) because of its instability at room temperature. Thus the imino chloride was dissolved in tetrahydrofuran (T.H.F.) (2ml) and thís solution added to lithium methoxide (51mg) in methanol (lml): T.H.F. (12ml) at -75°C. After stirring for twenty minutes, acetic acid (0.Sml) was added, and the mixture warmed to room temperature. Ether was added and washed with sodium bicarbonate solution and water, dried and evaporated to give a residue which was chromatographed on silica (petrol/ethyl acetate), thus affording the desired title compound (0.045g., 25% for (a) and (b) overall), max (CHCl3 ) 2030, 1790, 1730, 1600, 1530, 1500, 1350cm-1.

Æ080698 8 (CDCI3) 1.28 (6H,s,(CH3 )2 C), 3.58 (3H,s,CH3 0-), 4.33 (1H,s,C3-proton), 5.25 (2H,s,-CH2 Ar), 5.50 (iH,s,C5 -proton), 7.1-7.6 (12H,complex, aryl protons), 8.15 (2H,d,J 8Hz., -CH-CNO2-).

Method (ii) (This method avoids isolation of unstable intermediates. ) i0 :5 The Ketenimine from Example 1 (0.25g., 0.44mmol) in T.H.F.

(15ml) at-75 °C was treated, with stirring, with bromine (0.024mi' 0.44mmol). After i0 minutes, lithium methoxide (99.88% purity) 65mg.) in methanol (lml) was added, dropwise. After l0 minutes stirring at -75 0C acetic acid (o.5ml) was added, and the reaction solution worked up as in method (i) (b), thus affording the title Compound (0.08g.

3oe ), Example 3 Preparation of 2'-epimers of p-nitrobenzyl 6 -methoxy-6 - (2'-phenyl)-2'-PheDo carbonyl)acetamido penicillanate.

method (i) The Ketenimine from Example 2 (0.05g) in T.H.F.: H2 0 (20:1) (iml) was left at room temperature for 42 hours at pH 2.0 (H3PO4). Ethyl acetate was added, and the organic layer washed with water, dried and evaporated to give the title compound (0.05g), max (CHC13 ) 3360, 1790, 1750, 1700, 1530, 1500, 1355cm-1. 8 (CDCI3 ) 1.23, 1o29 (6H,2s (CH3 )2 C), 3.31, 3.36 (3H,2s,CH3 0-), 4.29, 4.32 (1H,2s,C3 -proton(, I0806 }8 7.0-7.8 (13H, complex, aryl and amide protons) 8.15 (2H, d,J 8Hz» -CH-NO2-).

Method (iÆ) The Ketenimine from Example 2 (0.05g) in aqueous acetone was stood at room temperature for 42 hours at pH 3.1 (p-toluenesulphonic acid added to give the required acidité). Ethyl acetate was added, and the organic layer washed with sodium bicarbonate solution and water. Drying and evaporation gave the title compound (0.05g).

lO Example 4.

Preparation of p-nitrobenzyl-6Ç-(2'-phenyl-2'-phenoxycarbonyl)Ketenimino-6oE-methylthio penicillanate.

Method 1 The Ketenimine from Example I (0.15g., 0.28mmol) and methyl methanethi0su1ph0nate (0.034mi, 0.29mmol) in dimethylformamide (iml) were added to potassium carbonate (0.04g, 0.29mmol) at O°C, and the mixture stirred for 45 minutes.

Ether and ammonium chloride solution were added, and the organic layer was further washed with water, dried (Na2 SO4) and evaporated to give a residue which was chromatographed on silica (ethyl acetate/petrol). Collection of the mobile main component gave the title compound (0.05g, 31%), max(CHCl3) 2010, 1785, 1730, 1525, 1350, ll90cm-1. 8 (CDC13 ) 1.34, 1.38 (6H, 2s, (CH3 )2 C), 2.39 (3H,s,CH3 S-), 4.43 (iH,s,C3 -proton), 5.35 (2H,s, -CH2 -), 5.53 (IH, s,C5 -proton), 7.2-7.8 (12H, complex, aryl protons), 8.27 (2H,d,J 8.5Hz., -CH02 ).

Method 2.

if i0 The Ketenimine from Example 1 (0.15g., 0.29mmol) in DMF (iml) at -15O was added rg_ sodium hydride (ca 55Ydnineral oil suspension 0.018g., ca. 0.37mmol) in DMF (3ml) at -20°. Methyl methanolsulphonate (0.034ml, 0.29mmol) was added, and the mixture stirred at -i0° for 70 minutes. Work up and chromatography as in Method 1 gave the title compound (0.04g., 29%).

Method 3 The Ketenimine from Example 1 (0.15g., 0.29mmol) in DMF (2ml) at -35° was added with stirring to potassium t_-butoxide (31mg., 0.29n oi) in DMF (4ml) at -35°. Methyl methanoithiosulphonate (0.034mi, 0.29mmol) was immediately added, and the solution stirred for 1 hour at -35°. Work up and chromatography as in Method 1 gave the title compound (0.04g, 29 ).

°r *- ....

Example Preparation of 2'-epimers of p-nitrobenzyl 6Ç-( 2'-pheny1-2'- phenoxycarl Dnyl) acetamido-6oE-methylthio penicillanate.

i0 The methylthio Ketenimine from Example 4 (0.07g) was dissolved in aqueous T.H.F. (5ml), the pH of which had been lowered to 1.0 by the addition of phosphoric acid. After 72 hours at room temperature, ethyl acetate was added, and the organic phase washed with water, dried (Na2 SO4) and evaporated to give the title compound (0.06g). max(CHCl3 ) 3300, 1780, 1745, 1685, 1525, 1350cm-1. 8 (CDCI3) 1.26, 1.34, 1.41, (6H,3s,(CH3 )2 C),- 2 19, 2.26 (3H,2s, CH3 S-), 4.36, 4.40 (iH,2s,C3 -proton), 4.92 (IH,s,-CH-CON), 5.36 (2H,s,-CH2 Ar), 5.61-5.64 (IH,2s,C5proton), 7.0-7.9 (13H, complex, aryl and amide protons), 8.30 (2H,d,J 8Hz, -CH-CNO2 -).

Example6.

Preparation of p-nitrobenzy1 6Ç-(2'(3"-thieny1)-2'-p-methylDhenoxycarbonyl)Ketenimino penicillanate.

p-Nitrobenzyl 6 -(2'-(3"-thienyl)-2'-R-methylphenoxycarbonyl) acetamido penicillanate (3.57g, 5.86mmoi) in benzene (18ml) was treated dropwise at 5° with pyridine (4.29ml) and subsequently with phosphorus pentachloride (3.72g) in benzene (75mi), at such a rate to keep the temperature at 5°C. After three hours stirring the solution was filtered, the solids washed with water and sodium bicarbonate solution. Drying and evaporation gave the Æ080698 title compound (3.35g, 97%), max (CHCI3) 2010, 1745, 1725, 1525, 1345cm-I. , 8 (CDCI3) 1.38, 1.49 (6H,2s,(CH3 )2 C), 2.26 (3H,s, CH3 Ar), 4.38 (iH,s, C3 -proton), 5.25 (2H,s,-OCH2 Ar), 5.52 (2H,s,C5 and C6 protons), 6.9-7.7 (9H,complex, aryl and thienyl protons), 8,15 (2H,d,J 8Hz, -CH-CNO2 -).

Example 7 Preparation of p-nitrobenzyl 6oE-methoxy-6Ç-(2'-(3"-thienyl)- 2,-p-methylphenoxycarb9nyl Ketenimino penicillanate.

Method 1 i0 The Ketenimine from Example 6 (2.50g., 4.21mmol) in T.H.F.

(80ml) at -70° was treated with chlorine (4,2m mol), and the solution stirred for 20 minutes. Lithium methoxide (0.44g., 11.5 mmol) in methanol (12ml)was added at such a rate (5 minutes) that the tem srature stayed below -67°C. After I0 minutes further, acetic acid (4ml) was added, and the solution was removed from the cooling bath. Ethyl acetate was added, and the organic layer washed with sodium bicarbonate and brine, dried and evaporated to give the crude title compound (2.42g.). Purification is achieved by chromatography on silica (petrol/ethyl acetate), giving 40% yield overall.

The title command possesses max HCI3) 2010, 1790, 1750, 1725, 1525, 1345cm-I. 8 (CDCI3) 1.34 (6H,s,(CH3 )2 C), 2.23 (3H,s,CH3Ar), 3.58 (3H,s,OCH3 ), 4.36 (IH,s,C3 -proton), 5.23 (2H,s,-CH2Ar) 5.53 (iH,s,C5 -proton), 6.8-7-7 (5H, complex, aryl and thienyl protons, 8.16 (2H,d,J 8Hz,-CH-CNO2 -).

Method 2.

Substitution of sodium for lithium methoxide (molar proportions as method i) as used in Method 1 gave the title compound in slightly lower yield than in Method i.

Method 3.

Substitution of bromine for chlorine (molar proportions as Method l) as used in Method 1 gave the title compound in lower yield than in Method l.

Example 8.

(a) Preparat$on of 2"-epimers of p-nitr0 benzy1 6oE-methoxy68-(2'-(3"-thienv1)-2'-P-methylphenoxycarb0nyl)- acetamido penicillanate.

The Ketenimine from Example 7 (1.67g., 2.69mmoi) was dissolved in T.H.F. (30ml) containing water (l ml) and a few drops of H3 PO4 to lower the pH to 2.6. After three days standing at room temperature, ethyl acetate was added, and washed with water. Drying and evaporation gave the title compound (1.51g., 88%). max (CHCl3 ) 3350, 1790, 1750, 1700, 1525, 1350cm-I. 8 (CDC13 ) 1.29, 1.33 (6H,2s,(CH3 )2 C), 2.27 (3H,s,CH3Ar), 3.33, 3.38 (3H,2s,CH3 0-), 4.31, 4.33 (IH,2s, C3-proton), 4.87 (IH,s,-CH-CON), 5.28 (2H,s,-OCH2 Ar), 5.57 (IH,s,C5-proton), 6.8-7.6 (10H, complex, aryl, thienyl and 10S069S amide protons), 8.17 (2H,d,J 8Hz, -CH-CNO2 -).

(b) 2'-epimers of 6oE-methoxy-6Ç-(2'(3"-thienyl)-2'-pmethylDhenoxycarbonyl)acetamido penicillanic acid.

i0 The p-nitrobenzyl ester from (a) above (l.0g., 2.59mmoi) in ethanol (15ml): T.J.F. (4ml): water (a few drops) was hydrogenated overPd/C (10%; ig) for four hours. The solution was filtered the solids washed with acetone, and the combined solutions evaporated to give the title compound and hydrogenolysed p-toluidene (total weight, 0.89g.) The latter material was removed by precipitation of the penicillin as the sodium salt from acetone, ether with sodium 2-ethyl hexanoate in methyl isobutyl ketone (2N., 0.73mi). (Overall yield from ester: 76%).

(c) 2'epimers of 6oE-methoxy-6Ç-(2'(3"-thienyl)-2'-carboxy acetamido penicillanic acid.

The monoester from (b) above (5.66g., 10.Smmol) in water (20ml) was stirred for 2 hours with Na2 B4 07 decahydrate (8.2g).

The pH was adjusted to 4, and the solution washed with ethyl acetate.

The pH was then lowered to 2, and the solution extracted with ethyl acetate. Drying and evaporation gave the title compound (3.5g.) which was precipitated as the di-sodium salt from acetone with sodium 2-ethyl hexanoate in methyl isobutyl ketone (2N, 9.0ml). (Overall yield from ester: 74%). The di-sodium salt possess max (nujol) 1760, 1670, 1600cm-I, 8(D2 0) 1.44 î080698 (6H,s,(CH3)2C), 3.51, 3.60 (3H,2s,-OCH3 ), 4.34 (IH,s,C3proton), 5.61 (IH,s,C5 -proton), 7.1-7.7 (3H, complex, thienyl protons).

Example 9.

Preparatiõn of p-bromophenacyl 6Ç-(2'(3"-thienyl)-2'-pmethylphenoxycarbonyl)Ketenimino penicillanate.

i0 p-Bromophenacyl 6 -(2'-(3"-thienyl)-2'-p-methylphenoxyoarbonyl) acetamido penicillanate (0.89g, 1.33mmol) in benzene (Sml) was treated successively at5°C with pyridine (1.02ml) and phosphorus pentachloride (0.84g) in benzene (20ml). After stirring for three hours, solids were filtered and washed with ethyl acetate, and the organic solution washed with water, sodium bicarbonate and brine. Drying and evaporation gave the title compound (0.87g., 95%). max (CHCI3 ) 2040, 1790, 1750, 1700cm-I . 8 (CDCI3) 1.64, 1.67 (6H,2s,(CH3 )2 C), 2.33 (3H,s,CH3 Ar), 4.64 (1H,s,C3 -proton), 5.37 (2H,ABq,J !7Hz, -OCH2COAr). 5.64 (2H,s,C6 -protons), 7.0-7.9 (llH, complex, thienyl and aryl protons).

Example i0.

Preparation of p-bromophenacy! 6e-methoxy-6 -(2'-(3"-thienyl)- 2'-p-methylphenoxycarbonyl)Ketenimino penicillanate.

Method 1 The Ketenimine from Example 9 (0.32g., 0.54mmol) in T.H.F.

1O8O698 (10ml) at -70 °C was treated wtih chlorine (0.54mmol) and stirred for i0 minutes. Sodium methoxide in methanol (IM. solution, 1.5ml) was added, and the solution stirred for a further I0 minutes at -70°. Acetic acid (0.5ml) was added, followed by ethyl acetate, and the organic solution was washed with sodium bicarbonate solution and brine to give the crude title compound (0.32g). Purified material was obtained by chromatgraphy on silica (petrol/ethyl acetate). The title -i compound possesses max (CHCI3 ) 2040, 1790, 1750, 1700cm .

8 (CDCI3 ) 1.52, 1.66 (õH,s,(CH3 )2 C), 2.38 (3H,s,CH3 Ar, 3.78 (3H,s,-OCH3), 4.68 (1H, s,C3 -proton), 5.48 (2H,s,-OCH2 COAr), 5.68 (iH,s,C5 -proton,), 7.1-8.0 (llH,complex, thienyl and aryl protons).

Method 2.

Substitution of bromine for chlorine as used in Method 1 (molar proportions as in l) gave a lower yield of title compound than Method l.

Method 3.

Substitution of lithium methoxide for sodium methoxide, and bromine for chlorine as used Method 1 (molar proportions as in I) gave a lower yield of title compound than Method i.

Method 4.

The Ketenimine from Example 9 (0.25g., 0.42nmioi) in T.H.F.

(2ml) at -70° was treated with bromine (0.023mi., 0.42n oi).

After i0 minutes the T.H.F. solution was mixed with thallium (I) methoxide (l.lmmol) suspension in methanol (iml) pre-cooled to -50°C, and the mixture vigorously stirred for minutes at -50°. Acetic acid (0.5ml) was then added, the precipitate filtered and ethyl acetate added. Washing with sodium bicarbonate solution and water, drying and evaporatìon gave the crude title compound (0.22g) in slightly lower purity than in Method i.

Example ll.

(a) Preparation of 2'-epimers of p-bromophenacyl 6oE-methoxy6 -(2'-(3"-thienyl)-2'p-methylphenoxycarbonyl)acetamido penicillanate.

i The purified Ketenimine from Example l0 (0.30g., 0.44mmol) was dissolved in T.H.F. (5ml) containing water (0.2ml) and phosphoric acid, sufficient to lower the pH to 2.6. After three days at room temperature, ethyl acetate was added, and washed with water. Drying and evaporation gave the title compound (0.26g., 84%). max (CHCI3 ), 3350, 1780, 1760, 1750, 1690cm-I. 8 (CDCI3 ), 1.40, 1.60 (6H,2s,(CH3 )2 C), 2.34 (3H,s,CH3Ar), 3.45, 3.49 (3H,2s,CH3 0-), 4.61 (IH, s, C3 _proton), 108O698 5.16 (IH,s,-CH-CON), 5.44 (2H,s,-OCH2 CO2 Ar), 5.71 (iH,s,C5-proton), 6.9-8.1 (12H,complex, thienyl, aryl, and amide protons).

(b) Preparation of 2ìepimers of 6oE-methoxy-,6 -(2'-(3"-thienyl)- 2'îp-methylphenoxyÇarbonyl)acetamido penicillanie acid.

Method i i0 The p-bromophenacyl ester from (a) above (0.26g) in dimethylformamide (6ml): acetic acid (3ml) was stirred with zinc dust (0.7g) for 75 minutes at room temperature. The solution was filtered and solids washed with ethyl acetate.

The organic layer was washed with water and extracted with sodium bicarbonate solution. The aqueous layer was acidified to pH 1.8 and extracted with ethyl acetate. Drying and evaporation gave the title compound (40mg). max (CHCI3) 3400-2400 (br), 1775, 1740, 1695cm-I. 8(CDCI3) 1.39, 1.51 (6H,2s,(CH3)2C), 2.38 (3H,s,CH3 Ar), 3.50 (3H,s,-OCH3 ), 4.47 (1H,s,C3-proton), 5.10 (1H,s,-CH-CON), 5.67 (1H,s,C5 -proton), 7.0-8.2 (9H, complex, thienyl, aryl, acid and amide protons).

(c) The 2'-epimers of 6oE-methoxy'6- -(2'-(3"-thienyl)- 2'-carboxy) acetamido penicillanic acid were prepared as described in Éxample 8(c).

Example 12.

Preparation of p-bromophena9yl6 -I2'-benzyloxycarbonyl-2'- 3ì'-thienyl))Ketenimino penicillanate.

i0 p-Bromophenacyl 6 -(2'-benzyloxycarbonyl-2'-(3"-thienyl))- acetamìdo penicillanate (0.89g., 1.33nm ol) in benzene (Sml) was treated dropwise at 5° with pyridine (l.02ml), and subsequently with phosphorus pentachloride (0.84g) in benzene (20ml), at such a rate to keep the temperature at 5°C. After three hours stirring, thè solutíon was filtered the solids washed with ethyl acetate, and the organic solution washed with water and sodium bicarbonate solution. Treatment with charcoal, drying and evaporation gave the title compound (0.70g., 76%). max (CHCl3 ) 2030, 1790, 1760, 1750cm-1.

8 (CDC13 ) 1.59, 1.63, (6H,2s,(CH3 )2 C), 4.59 (1H,s,C3 -proton), 5.28 (2H,s,-CH2 Ph), 5.39 (2H,ABq, J 17Hz, -CH2 COAr), 5.55 (2H,ABq, J 4Hz, C5 and C6 protons), 6.9-7.7 (12H, complex, aryl and thienyl protons).

Example 13.

P reparation of p-bromoçhenacyl 6 -(2'-o-isoproDvlDh.enQxycarbonyl-2'-(3"-thienyl))Ketenimino penicillanate.

p-Bromophenacyl 68-(2'-o-isopropylphenoxycarbonyl-2'-(Y'- thienyl)) acetamido penicillanate )0.44g., 0.63mmol) in benzene (3ml) was treated with pyridine (0.48mi) and phosphorus pentachloride (0.40g)in benzene (10ml) under the same conditions as used in Example 12. Work up as in Example 12 gave title compound (0.35., 82%). max (CHCI3 ) 2000, 1785, 1750, 1700cm-1 8(CDCI3) 1 21 (6H d,J 7Hz (CH3)2CH), 1.65 (6H,s,(CH3 )2 C), 3.05, sept, J 7 Hz., -CÆe2 ), 4.63 (iH,s,C3 -proton), 5.44 (2H,ABq,J 17Hz., -CH2 COAr), 5.65 (2H,s,C5 and C6 -protons), 7.1-8.0 (IIH, complex, thienyl and aryl protons).

Example 14.

Preparation of p-bromophenacyl6 -(2'Lmethoxyçarbony1-2'-(3"- thieny!))Ketenimino penicillanate.

p-Bromophenacyl 6 -(2 'meth0 xycarb0 ny1 -2 '-(3 "-thieny1 ))acetamid0 penicillanate (0.49g., 0.82mmol) in benzene (5ml) was treated with pyridine (0 63mi) and phosphorus pentachloride (0.52g) in benzene (15ml) under the same conditions as used in Example 12. Work up as in Example 12 gave the title compound (0.35g., 74%). max (CHCl3) 2000, 1780, 1750, 1700cm-1.

8 (CDCI3) 1.67 (6H,s,(CH3 )2 C), 3.69 (3H,s,-OCH3 ), 4.67 (iH,s,C3-proton), 5.45 (2H,ABq, J 18Hz., -CH2 COAr), 5.66 (2H,ABq, superimposed as "t", "J" 5Hz., C5 and C6 -protons), 7.0-8.0 (7H, complex, thienyl and aryl Protons).

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

I. A process for the preparation of a compound of formula Z CH3 R - íO2RI= C = N _--r-/ CH3 O C02R2 wherein Z is hydrogen or -OCH3 ; R represents 2-thienyl, 3-thienyl, phenyl or 4-hydroxyphenyl; -CO2RI represents an esterifiedC -carboxy group but when Z is -OCH3 , R1 is not alkyl; and R2 represents an in vivo hydrolysable esterforming radical or a carboxy-blocking group; which comprises (i) when Z is hydrogen, reacting a 6-acylaminopenicillin of formula (II):

R.CH.CO.NH O2R1 H CH3 7----j" CH3 CO2R2 (II) wherein R, R1 and R2 are as defined, with an aoid halide and recovering the required compound, or (ii) when Z is -OCH3 , reacting a compound of formula (IV):

X Y CH3 R - C - C = N - CH3 !oi f of O2 R2 (IV) wherein R, R1 and R2 are as defined, but RI is not alkyl, and X and Y are the