CA1194470A

CA1194470A - PROCESS FOR PREPARING DERIVATIVES OF .beta.-LACTAM ANTI- BIOTICS

Info

Publication number: CA1194470A
Application number: CA000396796A
Authority: CA
Inventors: Junichi Nakazawa; Masanao Kaneko; Takeo Miyaoka
Original assignee: Sankyo Co Ltd
Current assignee: Sankyo Co Ltd
Priority date: 1981-02-23
Filing date: 1982-02-23
Publication date: 1985-10-01
Also published as: ES509837A0; DK162603B; FI72521B; FI72521C; IT1157951B; FI820582L; NL8200708A; CH646977A5; DK75582A; ES8305362A1; SE8201087L; DK162603C; IT8267194A0; SE452620B

Abstract

ABSTRACT

B-Lactam antibiotics particularly cephamycin and cephalosporin derivatives, having the formula (I):

(I) (wherein R1 represents an acyl group, R2 represents a hydrogen atom or a methoxy group, R3 represents an amidinothio group or a heterocyclkylthio group and X
represents a sulphur atom, an oxygen atom or a methylene group) may be prepared in high yields, with a minimum of side reactions by reacting a compound of formula (II):

(II) (wherein R4 represents a hydrogen or halogen atom and R5 represents an amino group protected by an electron-attractive group) with an acyl halide of Formula R1-Y
(wherein Y represents d halogen atom), in the presence of a halogenated aliphatic hydrocarbon solvent, to give a compound of formula (IV):

Description

fl ~7~3 1. , The present i nventi on relates to a process for preparing derivatives of ~-lactam antibiotics~ especially cephalosporin and cephamycin derivatives, including rnany which are valuable antibiotics~

The cephalosporin and cephamycin derivatives considered to be of most interesk as antibiotics are still most com~only prepared by isolating a naturally produced cephalosporin or cephamycin ~i.e. a compound anal ogous to the cephal ospori ns but containing a methoxy group, instead of a hydrogen atom3 a~ the 7~-position) from a fermentation broth and then subjecting the r~sulting compounds to chemical modification to give the desired cephalosporin or cephamycin antibiotic. The most common chemical modifications to which these starting materials are subjected comprise replacement of the group at the 3-position of the starting ma~erial or transacylation in which the acyl substituent on the amino group at -the 7~-position of the starting material is replaced by a different acyl group. The present invention is concerned with this transacylation reaction.

The acyl group on the 7~~amino group of the cephalosporin and cephamycin starting materials is generally a complex group containing amino and carboxy groups which need to be protected before any chemi cal modification of ~he starting matcrial can be carried 4~3 out. These compounds also have a carboxy group at the 4-position and this, likewise, needs protection.
For example~ the principal starting material for the preparation of ~he cephamycin antibiotics is cephamycin S C~ which is 7~-(D~5-amino-5-carboxyvaleramidol-3-carbam~
oyloxymethyl-7~-methoxy-3-cephem-4-carboxylic aci do In order to transform this compound into some particularly useful antibiotics, it is necessary to convert the carbamoyloxymethyl group at the 3-position to a hetero cyclylthiome~hyl or amidinothiomethyl group and to replace the S-amino 5 carboxyvaleryl group at the 7~-position by a variety of other acyl groups. In generalZ
such a process is effected by means of the following s~eps:

(i ) protec~ing the amino group on ~he 7B side chain;

(ii ) converting the carbamoyloxy group on the side chain at the 3-position to the chosen thiomethyl grou p;

..
(iii) esterifying the carboxy groups at the 4-position and on the 7~ side chain;

(iv) subjecting the product to a transacylation reaction to replace ~he thus-protected 5-amino 5-carboxy-valeryl group on the 7B side chain by any o~her desired acyl group; and 3~

(v) removing the protecting group from the carboxy group at the 4-position.

The present invention is concerned primarily with steps (iii) (v~ and with step (i) insofar as the cholce of protecting group is concerned.

When c~rrying out any chemical process on a oonlmercial scale9 yields are a particular1y crucial factor in assessing the economic viability of the process and this applies particularly when the starting material 10 is itself a natural product, which may only be produced in relatively low yield. The acylation reaction, which is step ~iv~ of the process sequence outlined above, is particularly susceptible to low yields and can be a serious hinderance to the commercialization of compounds which are known to be of considerable therapeutic valueO

We have found that the yields depend very much upon the nature of the amino-protecting group on the ~ substituent at the 7~-position, on the substituent 20 at thP 3-position and on the protecting group chosen for the 4-carboxy group and~ her,ce~ if the rlght combi-nation is chosen from all the multitude of groups avail-able for these different positions9 ~ery high yields can be achieved~ hle have now found that d combination of an elec~ron-attrac~ive group protecting the amino group on the 7~- side chain, a heterocyclylthiomethyl or amidinothiomethyl (particularly heterocyclylthio-methyl) group as the 3-substituent and an optionally substituted phenacyl group as the carboxy~protecting group for the carboxy groups in the 7~- side chain and at the 4-position, is capable of allowing the trans aoylation reaction to proceed in very high yield.

However, one element in this other~ise desirable combination is itself a noteworthy source of difficulty, namely the phenacyl or substituted phenacyl group used as protection for the carboxy groups. This difficulty arises when the phenacyl or substituted phenacyl group is re~oved in the deprotec~ing step (v) of the aboYe reaction sequence. One of the advantages of phenacyl groups as protection for carboxy groups is that the resulting phenacyl esters are especially stablP under acid conditionsO This means, however, that quite strong methods have to be employed to remove them~

One known method of eliminating phenacyl pro~ecting groups is by the use of zinc with acetic acid or ~ormic acid. As has been repor~ed in J, Orgu ChemO 389 No. 17, p2994-2996 (1973), this reaction, when employed with a compound havlng an amidinothiomethyl or heterocyclyl thiomethyl group a~ the 3-position~ is accompanied ~ 7 by a reac~ion giving rise to the corresponding 3-exo~
methylene compound in high yields, tog~ther with a small amount of the 3-methyl compound. This results in a substantial reduction in the yield of the desired compound.

Another method of removing the phenacyl protecting groups is by the use of the sodium or potassium sal~
of thiophenol. However, when there is a heterocyclyl-thiomethyl group at the 3-position o-f the compound being thus treated, this elimination reaction leads to a ~hift in the position of the double bond of the cephem system~ giYing ris2 to a very high proportion o~ 20c phem isomers in the final product. Again;
yields of the desired compound are very significantly ~5 reduced.

We have now surprising1y found that the phenacyl protecting group can be selectively eliminated~ without the disadvantages mentioned above~ by reacting the starting material 9 in th2 presence of an inert solvent~
~ with zinc and an acid selected from inorganic acidsg monoesters of dibasic inor~anic acids ard sulphonic aci dsO

Thus~ the present invention consists in a process ~O'f preparing a compound of formula (I):

6~

C~O~

(wherei n R represents an acyl group;

R2 represenl;s a hydrogen atom or a methoxy group, R3 represents an amidinothio group or a he~ero-cyclyl thi o group; and X represen~s a sul phur atom, an oxygen atom or a methyl ene group) and pharmaceutieally acceptable salts thereof, llhich process compri ses ~he steps o (a) reacting a compound of formula (II):

7.

~5 B2 ~ ~J
H~3~ H~ ~I
~OC~ H2 ~3 ~ COOCH~-C~Q.

(wherei n: .
~29 R3 and X are as defined above;

R4 represents a hydrogen atom or a hal ogen atom;

and RS represents an ami no group protected by an el ect ron-attract i ve group ) with a compound of formul a ( I I I 3:

Rl ~ y ~III) (in which Rl is as defined above and Y represents a halogen atom) in a haloyenated aliphatic hydrocarbon solvent, to gi ve a compound of formul a ( IV ~:

The OCR engine was not able to convert this image.

(in which R13 R2, R3~ R4 and X are as defined above);

(b) reacting said compound of formula ~IV) with zinc and an acid selected from the group consist;ng of inorganic acids, monoesters of dibasic inorganic acid and sulphonic acids, in an inert solvent, to g1 Ye sai d compound of formula ~I); and (c~ if necessary9 salifying said compound oF formula (I) to give a pharmaceutically acceptable salt thereof.

This particular combination of reagents and protecting groups surprisingly allows the process of the invention to be carried out with good yields of the final product, these yields being exceptiorlally good when the process is carried out under the preferred conditions described in more detail helowO

:~3~

9.

The invention is of especial value in the pre-paration of cephamycin derivatives, that is to say compounds of formula (I) in which R2 represents a methoxy group and X represents a sulphur atom. The invention will, accordi ngly ? be described hereinafter with particular reference to the preparation of such der1vativesO It will~ however, be appreciated that it can equally be applied and advantages will equally be achieved in relation to the preparation of cephalospori n derivatives ~R~ represents a hydrogen atom and X represents a sulphur atom) as well as ~o the preparation of ~-lactam anti-biotics analogous to the cephamycins or cephalosporins wherein X represents an oxygen atom or a methylene group. The compounds of formula (II) used as starting ma~erials will be chosen ac ordingly~

In the acyl halide R1 - Y, used in step (a) of the process of the present invention~ the nature of the group represented by Rl will be dictated solely by the nature of the group R~ which it is desired to incorporate into the final produc~, the compound of ~ormula (I) or its salt. As suGhg the group represented by Rl may be chosen from the very wide range of such groups known to impart excellent antibiotic activity or other valuable properties to the final product.
Examples of groups which may be represented by R1 in the acyl halide R1 - Y~ and hence in the compound of 10~

formula (I), include the phenylacetyl, phenoxyacetyl, thienylacetylg monochloroacetyl, dichloroacetyl 9 mono-bromoacetyl, dibromoacetyl and cyanomethylthloacetyl groups, of whlch the thienylacetyl, monochloroacetyl, dichloroacetyl, monobromoacetyl, dibromoacetyl and cyanomethylthioacetyl groups are particularly preferred.
It must, however, be understood that these are given only as non-limiting examples of the many acyl groups which are possible and which would be immediately apparent to the man skilled in the art. Where ~he acyl group, represented by R1 in the compound of formula ~I)3 includes another reactive group (e g~ a hydroxy, amino or carboxy group), this other reactive group is preferably protected prior to reaction of the acyl halide R1 y with t`he compound of formula (II) and, in this case, a deprotecting step may be necessary at some stage in the reac~ion sequence, as is well-known in the art~

The halogen atom represented by Y in the acyl halide R1 - Y is preferably a chlorine or bromine atom.

The other starting ma~erial for the process of the invention is the compound of formula (II)o The nature of the preferred a~oms or groups represen~ed by R~ and X in this compound has been discussed above and is dictated by the nature of the compound of formula (I~

which it i~ desired to prepare~ Similarly~ the pre-ferred groups represented by R3 in the compound of ~ormula (II) are determined by what it is desired to have in the corresponding posi~ion of the compound of formula (X), Where R3 represents a heterocyclyl~
thio group a wide range of heterocyclic groups, bo~h substituted and unsubstituted9 are possible, Preferred heterocyclic groups which may form part 3f this heterocyclylthio group include the lH
tetrazol-5-yl, 19354-~hiadiazol-2 yl and 1,2,3-triazol-5-yl groups. These heterocyclic groups may be sub-stituted or unsubstituted and, where they are substituted, may haYe one or more9 preferably just oneS substituent.
The substituents ar preFerably selected from alkyl (preferably methyl) groups~ halogen atoms and dialkyl-a~ninoalkyl (preferably dimethylaminoethyl) groups.
Of the subs~ituted and unsubsti tuted heterocyclylthio groups which may be employed, we prefer the 1~me~hyl-lH~
tetr~zol-5-yl, 1 (~-dimethylaminoethyl)-1H-tPtrazol-5-yl 9 5-methyl-1,394-thiadiazol-2-yl and 1-methyl-1H-1~2,3 tri azol -5-yl groups.

Where R4 in the compounds of formulae (II) and (IV) represents a halogen atom9 this i5 pr~ferably a chlorine or bromine atom, ~.e. the protecting group for the carboxy groups on the 4- posi tion of the cephem 12.

system and for the carboxy group at ~he 5- posi~ion of the valeramido side-chain is preferably a phenacyl group, a chl orophenacyl group or a bromophenacyl group.

R5 in ~he compound of formula (II) represents an amino group having, as a substituent9 an electron attractiYe group. Sui~able electron-attractive groups inelude: substituted benzoyl groups having a nitro, chloro, cyano or ~Cl-C3 al koxy3carbonyl (e.g~ methoxy-carbonyl, ethoxycarbonyl or propoxycarbonyl ) substituent, preferably in ~he or~ho or para position, aryl sul phonyl groups, preferably ben2enesulphonyl j or phthaloyl groupsO Of these, the mos~ preferred electron-attractive group is the benzenesulphonyl groupO

The first step in the process uf ~he invention comprises the transacylation reaction be~ween the com-pound of formula (II) and the acyl halide R1 - Y in a halogenated aliphatic hydrocarbon solvent. Suitable halogenated aliphatic hydrocarbon solvents include 20 meEhylene chloride, chloroform, trichloroethylene, 1~2~dichloroethane, 1,1,1-trichloroe~hane and 1,1,2-tri~
chloroethane~ most preferably 172 ~ichloroethane.

The amount of acyl halide, R - Y, is preferably equirnolar or greater than eguimolar with respect to 13~

the compound of formula (II), for example the molar ratio of the acyl halide to the compound of -Formula (II~
is preferably from 1 : 1 ~o 10 : 1 and more preferably from 5 : 1 to 10 : 1. The temperature ak whish the reaction is effected may vary over a wide range but is most conveniently from 50C to 100C. The progress of the reaction can be traced by thin layer chromatographyO At a temperature within the preferred range, the time required for the rear,tion will normally vary from 10 minutes to lQ hours.

rhe transacyl ation reaction will proceed more smoothly if it is carried out in the presence of an acid-binding agent, for example propylene oxide~ butylene oxide, styrene oxide or phenyl glycidyl ether, The resulting compound of formula (IV) ub~ained in the First step of the reaction may be recovered and purified by distilling the solvent from the reaction mixture, adding diisopropyl ether to the residue and i~olating the powders thus produced. Alternatively~

2~ the product may be recovered and puri fi ed by chromato-graphy techniques or by any other method known in the art. Intermediate isolation and purification of the product may not be necessary prior ~o embarking upon the second stage oF the process of the inven~ionO

1~.

In the second stage of the process, the phenacyl group or halophenacyl group protecting the 4-carboxy group on the cephem system is removed by reacti ng the compound of formula (IV) with zinc and an acid. In accordance wîth the present invention, the acid is an inorganic acidg a monoester of a dibasic inorganic acid or a sulphonic acid. Suitable inorganic acids include sulphuric acid~ hydrochloric acid9 nitric acid and fluorosulphuric acid. Preferred monoesters of dibasic inorganîc acids are monoalkyl esters of sul-phuric acid9 preferably monoethylsulphuric acid.
Preferred sul phoni c aoids are al kanesul phonic acids and haloalkanesulphonic acids5 preferably methane sulphonic acid, ethanesulphonic acid or trifluoro methanesulphonic acidD The most preferred acids are methanesulphonic acid and monoethylsulphuric acid.

The reaction in the second stage of the process of the invention is effected in an înert solvent.
The nature of the solven~ employed is not critical g provided only that it is inert in the sense that it has no adverse effeot upon the reaction. In view of the use of acids in the process of the invention, the preferred solvents are aqueous organic solven~s, for example aqueous methanol 9 aqueous acetone9 aqueous 15.

acetonitrile or aqueous tetrahydrofuran~ of which aqueous acetone is most preferred from the point of view of solubility of the s~arting material and economy~
The zinc is preferably employed in an amount of 1 equivalent or more per equivalent of ester of formula (IV~3 more preferably from 1 to 2 equivalents of zinc per equivalent of said compound of formula (IV)o The temperature required for the reaction varies over a very wide range al~hough, in order ~o minimize side reactions, the temperature is preferably below ambient. A preferred temperature is within the range of from ~50C to +5C, more preferably from -Z0C
to -30C. The time required for the reaction will vary depending upon the reaction temperature and the reagents but the reaction will generally be complete within a period of from 10 minutes to 7 hours.

After the phenacyl or halophenacyl protecting group has been completely eliminatedg the resulting compound of formula (I) may be reeovered from the reaction mixture by conYentional means~ For example9 one suitable recovery procedure comprises: diluting the reaction mixture with water, fil~ering off insolubles; extracting the filtrate with a suitable organic solvent (e~9O
ethyl acetate)) and then distilling the solvent from the extract. The crude product thlJ3 obtained may then be further isolated (by conversion to a crystalline 16.

salt) by reacting it with a suitable base~ such as di cycl ohexyl ami ne, dimethylbenzyl ami ne, picoline or lutidine. Alternatively~ the crude product may be purified by chromatography techniques or by any other method well-known to those skilled in the art.

The resulting compound of formula (I~ may9 if desiredg be converted to a pharmaceutically acceptable salt by conventional means, the nature of the salt not being cri~ical 9 provided that the activity of the free base is not or is not unduly degraded. Suitable salts include: salts of metalsg such as lithium, sodium, potassium9 calcium or magnesium~ the ammonium salt;
and salts with organic amines, such as the cyclohexyl-ammonium or triethylammonium salts. The sodium and potassium salts are most preferred.

The oompound of formula (II) which is used asa ~tarting material in ~he process of ~he inven~ion may be obtained by pro~ecting the amino group in the 7~side chain of cephamycin C or a cephalosporin or other ~-lactam analogue thereof with a suitable electron-attractive group (as exemplified above)g converting the carbamoyloxymethyl group at the 3-position to a heterocyclylthiomethyl or amidinothiome~hyl ~roup and then acylating the carboxy groups in the 7~ side chain and at the 4-position with a phenacyl gro~p or a halo-r7 ~7~

phenacyl group. In the preferred embodiment o-F the process of the invention~ to prepare a cephamycin derivatiYe, the substituents at the 3- and 7- positions of cephamycin C, which may be obtained by cultivating various microorganisms, may be converted, in an essen-tially continuous fashion to desired groups, thereby preparing compounds having more potent antibacterial activity.

The invention is further illustrated by ~he following ExamplesO

XAMPLE

7~-~hloroacetamido-7a-methoxy-3~
methyl-1H-tetrazol-5-~l)thiomethyl-

3 cephem-4-carboxylic acid 15 ~a) Di(dicyclohexylamine) salt of 7~(D-5-benzene-sulphonylamino-5-carbox~valeramido~-7a-methoxy-3~ meth lH-tetrazol-5-~l)thiomethyl-3-cephem-4-carboxylic acid To 70 g of 7~-(D-5~benzenesulphonylamino-5-carboxy~
valeramido)-3~carbamoyloxymethyl-7a-methoxy-3~cephem-4-carboxylic acid (85% purity~ ~ere added 175 9 of 1 me~hyl-5-mercapto-1H-tetrazoleg 12 ml of water and 3 ml of ac2tone, and the resulting solution was then stirred r~ JF~ t7~3 18~ 1 at an internal temperature of 65 75C for 20 minutes, whilst water and acetone were distilled of f9 little by little, under reduced pressure. 200 ml of water and 500 ml of ethyl acetate were then added to the 5 reaction mixture and the agueous phase of khi s mixture was adjusted to a pH of 1.5 by the addition of hydro-ohloric acidO 50 9 of sodium chloride were added to the mixture9 which was then thoroughly stirred.
The ethyl acetate layer was separaked off and the aqueous layer was twice extracted, each time with 100 ml of ethyl acetate. The extracts were combined wi~h the separated ekhyl acetate layer and then the whole mixture was evaporated to dryness under reduced pressure.
1.6 litres of diisopropyl ether were added to ~he resulting residue and the mixture was well stirred until a powder was produced from the original viscous substance. This powder was collected by filtra~ion, washed with diiso-propyl ether9 and dissolved in 500 ml of ethanolO
43.2 9 oF dicyclohexylamine were added to the solu~ion ~o and then ttle resulking mixture was left to stand in an ice-bath for 1 hour ~o precipitate white crystals.
These crystals were collected by filtration9 washed wikh ethanol and dried ko afford 76.4 9 of the crude di(dicyclohexylamine~ sal~ of 7~(D-5-benzenesulphonyl-amino~5-carboxyvaleramido~-7a-methoxy-3-(l-me~hyl-lH-tetra ~ol-5-yl)thiomethyl-3-cephem-4-carboxylic acidO The ,19.

reduced pressure and a small amount of ethanol was added to the resulting residue, This mixture was left to stand for about 6 days to precipitate crystals, which were collected by filtration and dried to give a further 8.2 9 of crystals of the crude di(dicyclohexyl-amine3 salt (total yield 84r6 9~ 83~0% of theory).

1 9 of the rrystals thus obtained was dissolved in 5 ml of methanol and the solution was ~oncentrated by evaporation under reduced pressure, to give a syrupy substan5e~ 5 ml of ethanol were added to this syrupy substance and the mixture was left to stand to pre-cipitate a pure product melting at 143 - 145~C (with desomposition), Elemental Analysis:
Calculated for C23H27N70gS3~7~C12H23N) C~ 55O94%;; H9 7O45%; N9 12.3~%; S, 9~33%O
Found: C3 56~21%; H~ 7O33X; Ns 12.56%l S, 9058%.

(b) D~phenac~l ester of_7~-(D-5~benze~esulphon~1amino-5-c~ leramido)-7~ methox~y-3-(1-methyl~1H-tetrazol-5~ thiomethyl-3-cephem-4-carbox~ic acid To a solution of 4.4 g of phenacyl bromide in 50 ml of dimethylformamide was added, little by little, 10 9 of the di(dicyclohexylamine) sal~ oF 7~-(D-5-benzene-20.

sulphonylamino-5-carboxyvaleramido3-7~-methoxy-3-(1-methyl-1H-tetrazol-5-yl)thiomethyl~3-cephPm-4-carboxylic acid (purity 96%, determined by high pressure liquid chromatography) at a ~empera~ure of 0 5C3 over 10 minutesO The mixture was then stirred at ambient temperature for 30 minutes. At the end o~ this time9 200 ml of ethyl acetate were added, and insolubles (mainly dicyclohexylamine hydrobromide~ were coilected by fil~ration and washed with a small amount of ethyl acetate. The washings were combined with the original ethyl acetate soluticn and then the whole was washed twice3 each time with 50 ml of water. The solution was ~hen concentrated by evaporation under reduced pressure~
to afford 9.2 g of the title compound as a foamy solid~

Nuclear Magnetic Resonance Spectrum ~CDC13) ~ ppm:
l.S - 2.95 (7H, multiplet);
3.43 (3H, singlet~;
3 . 58 ( 2H 9 broad singlet~;
3.78 (3H, single~) 9

4.38 (2H, singlet);

5.00 (lH~ singlet)3 5.07 (2H, singlet);
5.45 ~2H~ broad singlet);
600 - 6.15 (lH3 doublet);
7922 ~ 8.02 (15H3 multiplet)~

21~

(c) Phenacyl 7~-chloroacetamido-7~-methoxy-3-(1-meth~l -ltl-tetrazol -5-yl)thiomethyl-3-ce~em-4-carbox~
late To the whole of the product obtained in step tb) were added 200 ml of 1,2-dichloroethane and 10 ml of monochloroacetyl chlorideg and then the mixture ~as s~irred under reflux for 4 hours. At the end of this time, the solvent was distilled of~ under reduced pressure and 100 ml of diisopropyl ether were added -to the resi dueO
The mixture was stirred sufficiently to precipitate a powder~ which was then collected by filtration, afford-ing 11004 9 of crude phenacyl 7~-chloroacetamido-7~-meth-oxy 3 (1-methyl-1H-tetrazol-5-yl)thiomethyl-3-cephem-4-carboxylate ~purity 44.7%, yield, cGrrected for impurities, 93% of theory~ This produc~ was purified by column chromatography through silica gel, eluted w;th a 3: 1 by volume mixture of benzene and ethyl ~cetate, to give a pure productO

Nuclear Magnetic Resonance Spectrum (CDCl3) ~ ppm-3.57 (3H9 singlet)~
3~68 (2H3 singlet), 30~2 ~3H, singlet);
4~13 ~2H~ singlet3;
4~50 (2H, broad singlet)~
5.08 (lH~ singlet);

22.

5.55 (2H, singlet);
7.25 - 8007 (5H, multiplet).

(d) 7~-Chloroacetamido-?~-methoxy-3-(1-methyl-1H~
tetrazol-5-yl)~hiome~hyl 3-cephem-4-carboxylic acid 1.0 9 of phenacyl 7~-chloroacetamido-7 me~hoxy-3-(1-methyl-1H-tetrazol-S-yl)thiomethyl-3-cephem-4-carboxylate (purity 90.1%, determined by high pressure liquid chromatography) was dissolved in a mixture of 20 ml of acetone and 1 ml of waterO The ~ixture was 1b then cooled to -30C3 after which 5.0 ml of monoe~hyl sulphuric acid and loO g of zinc powder were added.
The mixture was then s~irred a~ a temperature from 30C to -2SC for 2~5 hours. At the end of this time, the reaction ~ixture was filtered. Insoluble solid materials were washed with 50 ml of ethyl acetate and the washings were combined with the filtrate.
The mixture was then shaken and the ethyl acetate layer was separated. The aqueous layer w~s twice extracted, each time with 30 ml of ethyl acetate, and ~he extracts were combined with the separated ethyl aceta~e layer, The combined ethyl acetate solution was washed with a saturated aqueous solution of sodium chloride9 after which the solvent was distilled off under reduced pressure, to give 0.857 9 of the ~itle compound haviny a puri ~y of 70.3~. The yield, corrected for impurities, was 85% of theory.

23~

Nuclear Magnetic Resonance Spectrum (deuteroacetone) ~ ppm:
3.5 (3H, singlet);
3.67 (2H, singlet);
3~98 (3H, singlet), 4O42 (2H 3 broad singlet);
5.08 (lH, singlet), 3~ meth~l-1H-tetrazol-5-~yll~hiometh~
3-cephem-4-carbox~lic acid (a) Following the procedure described in skep (b~
of Example 1~ the corresponding diphenacyl ester was synthesized from 10 9 of the di~dicyclohexylamine) salt of 7~-(D-5-benzenesulphonylamino-5-carboxyvaler-amido)-7k-methoxy-3~ methyl-1H-tetrazol~5-yl)thiomcthyl-3-cephem-4-carboxylic acid. As in step (c) of Example 1, the resulting product was khen refluxed with 8.5 9 of cyanomethylth;oacetyl chloride ~in place of the monochloroacetyl chloride~ for 6 hoursa wi~h stirring, and then the reaction mixture was subjected to the treatment described in step (c) of Fxample 13 to give 12.1 9 of crude phenacyl 7~-cyanomethylthisacetamido-7~-methoxy-3-(1-methyl lH~tetra~ol~5~yl)thiomethyl~3~cephenl-24.

4-carboxylate (purity 38.0%, yield, corrected for impu-rities, 78.0% of theory). This product was purified by column chromatography through silica gel ~ eluted with a 2 : 1 by volume rnixture of chloroform and ethyl acetate.

Nuclear Magnetic Resonance Spectrum (deuteroacetone) ~ ppm:
3.53 (3H, singlet~;
3.60 (2H, singlet);
3.73 (4H, multiplet);
3.96 (3H, single~);
4050 (2H, broad singlet);
5015 (1H, slnglet);
5.63 ~ZH, singlet);
7.46 - 8.2 (5H, multiplet)9 8058 (lH, broad singlet).

(b~ 1.0 9 o~ phenacyl 7~-cyanomethylthioacetamido-7~
methoxy-3-(1-rnethyl-1H te~razol-5-yl)thiome-thyl-3 cephem-4~carboxylate (purity 8807%9 determined by high pressure liquid chrornatography~ was dissolved in 20 ml of acetone and 2 ml of water, after which it was ~reated and the product purified as described in step (d) of Example 1, '7 25.

to give 0.847 9 of crude 7~-cyanomethylthioaçetamido-7a~methoxy-3-(1-methyl-lH-tetrazol~5-yl)thiomethyl-3-cephem-4-carboxy1ic acid (purity 73.7%, determined by high pressure liquid chr~matography 7 yi eld, corrected for impur~ties, 38.0%~.

Nuclear Magnetic Resonance Spectrum (deuteroacetone) ~ ppm:
3.50 (3H, singlet~;
3.60 (2H9 singlet), 305 307 (2H, quartet39 3.70 (2H3 singlet)~
3.90 (3H, singlet);
4.3 - 406 (2H, quartet)9 5,10 (lH, singlet3~

7a-Methoxy-3~ nethyl~lH-tetrazol-5-~llthiomethyl-7~-(2-thien~acetamido~-3-cephem-4-carboxylic acid Following the procedure described in steps (a) -(c) of xample 1, but using 2-thienylacetyl chloride in place of the monochloroace~yl chloride in step (c)9 phenacyl 7a-methoxy-3-(1-methyl-1H-tetrazolw5-yl~thio-- methyl-7~-(2-thienylacetamido)-3-cephem-4-carboxylate ~y~
2~.

was prepared. loO g of this compound was dissolved in 20 ml cf acetone and ~ ml of water7 to give a solution, which was then cooled to -30C~ To the solution were added 5.0 ml of methanesulphonic acid and 1.0 9 of zinc powder, and the resul~ing mixture was then stirred at -30C for 2.5 hours. The reaction mixture was then treated and the product separated as described in step (d) of Example 1, to give 0085 9 of the ti~le compound.

Nuclear Magnetic Resonance Spectrum (deuteroacetone3 ~ ppmO
3,42 ~3H, singlet);
3.53 and 3.76 (2H, ABTdoublet~ J = 18 Hz), 3.~2 (ZH, singlet);
3.96 (3H3 singlet~;
4~28 and 4050 (2H9 AB-doublet, J = 14 Hz);
5.04 (lH, singlet33 6g8 7~1 (2H, multiplet);
7,2 - 7.4 (lH, multiplet), 8.27 (lH, broad singlet).

7~-Dichloroacetamido-7a-methoxy-3 (l-methyl_lH-tetrazol-5~yl)thiomethyl-3-cephem ~-carboxylic acid p-Bromophenacyl 7~-dichloroacetamido-7a-methoxy-27~

3~ methyl-1H-te~razol-5-yl3thiomethyl-3 cephem-4-carboxyla~e ~as prepared following essentially the same procedure as described in steps (a) - (c) of Example 1, except that p-bromophenacyl bromide was used (instead of phenacyl bromide) in step (b) and dichloroacetyl chloride was used (in place of monochloroacetyl chloride) in step (c). 1~0 9 of this compound was dissolved in ~0 ml of acetone and 2 ml of water and the resulting solution was cooled ~o -30O. To this solution were 10. added 5.0 ml of monoethylsulphurie acid and 1~0 9 of zinc powder, and the resulting mixture was stirred at 30C for 2 hours. The reaction mixture was then treated and the product separated as described in step (d) of Example 1, to give 0.8 9 of the ti~le compound~

Nuclear ~agnetic Resonance Spectrum (deuteroacetone) ~ ppm:
3~43 ~3H, singlet);
3080 (2H~ broad sing7et);
3098 (3H~ single~);
4.40 (2H, broad singlet);
5005 (lH, singlet);

6,~6 (lH, singlet).

Claims

28.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing a compound of formula (I) (I) (wherein:
R1 represents an acyl group;

R2 represents a hydrogen atom or a methoxy group;

R3 represents an amidinothio group or a hetero-cyclylthio group; and X represents a sulphur atom, an oxygen atom or a methylene group) and pharmaceutically acceptable salts thereof, which process comprises the steps:

29.

(a) reacting a compound of formula (II):

(II) (wherein R2, R3 and X are as defined above;

R4 represents a hydrogen atom or a halogen atom, and R5 represents an amino group protected by an electron-attractive group) with a compound of formula (III):

R1 - Y (III) (in which R1 is as defined above and Y represents a halogen atom) in a halogenated aliphatic hydrocarbon solvent, to give a compound of formula (IV):

30.

(IV) (IN which R1, R2, R3, R4 and X are as defined above);
(b) reacting said compound of formula (IV) with zinc and an acid selected from the group consisting of inorganic acids, monoesters of dibasic inorganic acids and sulphonic acids, in an inert solvent, to give said compound of formula (I); and (c) if necessary, salifying said compound of formula (I) to give a pharmaceutically acceptable salt thereof.

2. A process as claimed in Claim 1, wherein R2 represents a methoxy group and X represents a sulphur atom.

31.

3. A process as claimed in Claim 1, wherein R2 represents a hydrogen atom and X represents a sulphur atom.

4. A process as claimed in any one of Claims 1, 2 and 3, wherein R1 represents a phenylacetyl, phenoxy-acetyl, thienylacetyl, monochloroacetyl, dichloroacetyl, monobromoacecyl, dibromoacetyl or cyanomethylthioacetyl group.

5. A process as claimed in any one of Claims 1, 2 and 3, wherein R1 represents a thienylacetyl, mono-chloroacetyl, dichloroacetyl, monobromoacetyl, dibromo-acetyl or cyanomethylthioacetyl group.

6. A process as claimed in any one of Claims 1, 2 and 3 9 wherein Y represents a chlorine or bromine atom.

7. A process as claimed in any one of Claims 19 2 and 3, wherein R1 represents a thienylacetyl, mono-chloroacetyl, dichloroacetyl, monobromoacetyl, dibromo-acetyl or cyanomethylthioacetyl group and Y represents a chlorine or bromine atom.

8. A process as claimed in any one of Claims 1, 2 and 3, wherein R3 represents an amidinothio group 32.

or a substituted or unsubstituted 1H-tetrazol-5-ylthio, 1,3,4-thiadiazol-2-ylthio or 1,2,3-triazol-5-ylthio group.

9. A process as claimed in any one of Claims 1, 2 and 3, wherein R3 represents a 1-methyl-1H-tetrazol-5-ylthio, 1-(.beta.-dimethylaminoethyl)-1H-tetrazol-5-ylthio, 5-methyl-1,3,4-thiadiazol-2-ylthio or 1-methyl-1H-1,2,3-triazol-5-ylthio group.

10. A process as claimed in any one of Claims 1, 2 and 3, wherein R4 represents a hydrogen, chlorine or bromine atom.

11. A process as claimed in any one of Claims 1, 2 and 3, wherein said electron-attractive group in the group represented by R5 is: a substituted benzoyl group having a nitro, chloro, cyano or (C1-C3 alkoxy)-carbonyl substituent in the ortho or para position;
an arylsulphonyl group; or a phthaloyl group.

12. A process as claimed in any one of Claims 1, 2 and 3, wherein the electron-attractive group in the group represented by R5 is a p-nitrobenzoyl, benzene-sulphonyl or phthaloyl group.

13. A process as claimed in any one of Claims 1, 33.

2 and 3, wherein said electron-attractive group in the group represented by R5 is a benzenesulphonyl group,

14. A process as claimed in any one of Claims 1, 2 and 3, wherein step (a) is effected in the presence of a solvent selected from methylene chloride, chloro-form, trichloroethylene, 1,2-dichloroethane, 1,1,1-tri-chloroethane and 1,1,2-trichloroethane.

15. A process as claimed in any one of Claims 1, 2 and 3, wherein step (a) is effected in the presence, as solvent, of 1,2-dichloroethane.

16. A process as claimed in any one of Claims 1, 2 and 3, wherein the molar ratio of said compound of formula (III) to said compound of formula (II) in step (a) is from 1 : 1 to 10 : 1.

17. A process as claimed in any one of Claims 1, 2 and 3, wherein the molar ratio of said compound of formula (III) to said compound of formula (II) in step (a) is from 5 : 1 to 10 : 1.

18. A process as claimed in any one of Claims 1, 2 and 3, wherein step (a) is effected at a temperature of from 50°C to 100°C.

34.

19. A process as claimed in any one of Claims 1, 2 and 3, wherein the acid employed in step (b) is sul-phuric acid, hydrochloric acid, nitric acid, fluoro-sulphuric acid, monoethylsulphuric acid, methanesul-phonic acid, ethanesulphonic acid or trifluoromethane-sulphonic acid.

20. A process as claimed in any one of Claims 1, 2 and 3, wherein the acid employed in step (b) is methane sulphonic acid or monoethylsulphuric acid.

21. A process as claimed in any one of Claims 19 2 and 3, wherein step (b) is effected in, as solvent, aqueous methanol, aqueous acetone, aqueous acetonitrile or aqueous tetrahydrofuran.

22. A process as claimed in any one of Claims 1, 2 and 3, wherein said zinc is employed, in step (b) in an amount of 1 equivalent or more per equivalent of said compound of formula (IV).

23. A process as claimed in any one of Claims 1, 2 and 3, wherein said zinc is employed, in step (b), in an amount of from 1 to 2 equivalents per equivalent of said compound of formula (IV).

35.

24. A process as claimed in any one of Claims 1, 2 and 3, wherein step (b) is effected at a temperature of from -50°C to +5°C.

25. A process as claimed in any one of Claims 1, 2 and 3, wherein step (b) is effected at a temperature of from -20°C to -30°C.