Note: Descriptions are shown in the official language in which they were submitted.
Novel intermediates for use in ~_duction of ~halosporin
antibi_ lcs
This invention relates to novel intermediates
for the production of known 2-oximinoacetamido-3-cephem-
4-carboxylic derivatives and is a divisional of Canadian
applicat:ion Seri2l1 No. 374,191, filed March 30, 1981.
That application describes a process for the
production of ~yn-isomers of formula I,
~ORl
N
R -C-CO-NH ~ S~ I
~ N ~ CH2R4
OOR2
in which Rl is hydrogen, alkyl, phenalkyl, carbalk-
oxyalkyl, acyl or carboxyalkyl,
R2 :is hydrogen, pivaloyloxymethyl or a
carboxy protecting group,
R3 :is a 5-membered oxygen- or sulphur-
containing heterocyclic ring, which
may be substituted by amino or azido,
and
R4 is hydrogen, acetoxy, carbamoyloxy of
-S-Y, in which Y is a heterocyclic
ring which may be substituted.
~¢~
- 2 - 970-9688
The compounds of formula I represent a known
class of valuable cephalosporin antibiotics disclosed
for example in W. German DOS 2,223,375; 2,556,736;
2,702,501; 2,707,565; 2,715,385; 2,992,036; as well
as numerous other patent and other publications. This
class of antibiotics is characterised by the presence
of an oximino group in the 7-acylamido side-chain
attached to the cephalosporin nucleus. It is known
that this oximino group may have the syn of anti con-
figuration but that the syn isomers are preferred.
The heterocyclj.c ring in R3 contains, asindicated, one or more oxygen and/or sulphur atoms
as heteroatom(s). It may, however, additionally con-
tain one or more nitrogen hetero atoms. Suitable
heterocyclic rings inclucle furyl, thienyl, thiazolyl,
thiadiazolyl, oxazolyl and oxadiazolyl. The hetero-
cyclic ring may as indicated be unsubstituted or sub-
stituted by amino or azido, preferably amino. Prefer-
ably the heterocyclic ring of R3is thiazolyl and this
is preferably substituted by amino.
A particular preferred group of ~ isomers
is that of formula Ia,
- 3 - 970-9688
ORl
2 ~ \ ~ -C-CONH ~ S ~ Ia
N N ~--~CH2~4
O~R2
Rl~ R2 and R4 are as defined above
In ~hese structures 9 the radical R4 can be
hydrogen. Ik may also be carba~oyloxy. I~ is, how-
e~er, prleferably, acetoxy or -S-Y. Su~table het~ro-
cycllc g:roups which Y may represent are well-known, for
example from the numerous publications referred to
above. ~Preferred Iheterocyclic rings include thiad~az-
olyl, diazolyl, tr;iazolyl, tetra~olyl, thiazolyl,
thiatriazolyl, oxa~olyl, oxadia~olyl, triazolylpyridyl,
purinyl, pyridyl, pyrimidinyl, pyridaæinyl, pyrazolyl
or tr.iazi.nyl. Thec;e heterocyclic rings may be unsub-
stituted or substituted, for example up to three times.
Suitable substituents include Cl_4alkyl, Cl 4alkoxy,
halogen, trihalo-Cl 4 alkyl, hydroxy, oxo, mercapto,
amino, carboxyl, carbamoyl, di-(Cl 4)alkylamino,
carboxymethyl, carb,amoylmethyl, sulphomethyl and
methoxycarbonylamino. Heterocyclic moieties indlcated
in the pr.ior art to be particularly prefPrred include
tetrazoly.L, in partl.cular l-rnethyl-l~-tetra~ol-5-yl,
2l) and triazilnyl, in pa~ticular 1,2,5,6-tetrahydro-2-
- 4 - 9~0~9688
methyl-5,6-dioxo-as-triazin-3-yl, 2,5-dihydro-6-
hydroxy-2-methyl-5-oxo-as-triazin-3-yl or 1,4,5,6-
tetrahydro-~-lnethyl-5,6--dioxo-as-triazin-3-yl. Pref-
erably R~ is acetoxy, l-meth~l-lH-tetrazol-5-yl, or
2,5-dihydro-6--hydroxy-2-methyl-5-oxo-as-triazin-3-yl.
In these structures, Rlmay be hydrogen. It
may also be C] 4alkyl preferably Cl 2alkyl, in partic-
ular methyl. Suitable pnenalkyl groups include phen-
Cl 4-alkyl, particularly benzyl. Rl may also be carb--
alkoxyalkyl, for example carb~Cl_2)alkoxy(C1 4)alkyl,in particular carb(Cl ~)alkoxymethyl, e.g. carbethoxy-
methyl. Suitable acyl radicals include C2 5alkanyol or,
Cl ~alkoxycarbonyl. Rl rnay also be carboxyalkyl, in
particular carboxy-Cl_4a:Lkyl, e.g. carboxymethyl.
As is well known in the cephalosporin field,
the compound~ may be in theform of free acids (R2 = H)
or of salts, f~r example alkali or al~aline earth metal
salts, preferably alkali metal salts, such as sodium
salts. Alternatively, tile compounds may be in the
form of esters, e.g. the pivaloyloxymethyl ester.
(R2 = pivaloyloxymethyl). Other carboxy protecting
groups which R2 may represent are well-known and
include acetoxyrnethyl, :L-acetoxyethyl, l-ethoxycarbonyl-
oxyethyl, 5-indanoyl or, preferably, hexanoylmethyl,
phthalidyl, carbethoxymethoxymethyl or 3-carbethoxy~
- 5 - 970-96~8
l-acetonyl.
Particulnrly preferred compounds are ~y~
lsomers havin~ the formula Ib,
~ OCH3
}3~N~ C-CONH ~ ~ Ib
OOi~
in which R4 ls acetoxy, l-methyl-lH-tetrazol-S-yl,
or 2,5-dihydro-6-hydroxy-2-methyL-5-
oxo-as-triazin-3-yl,
and salts thereof.
The compounds of formula Ib are the products
known as Cefotax1m (R4 = acetoxy), SCE-1365 (R4 = 1-
methyl~ tetrazol-5-yl) and Ceftrlaxone (Rol3-9904)
(R4 - 2,5-dlhydro-6-hydroxy-2-~ethyl-5-oxo-as-triazin-
3-yl~, in the form c)f sodium salts (Cefotaxim and
SCE-1365) or the disodium salt (Ceftriaxone).
As indicated, the compounds of formula I are
generally known, ancl various methods for thelr produc-
tion have been proposed. One such method involves
acylatlon of the corresponding 7-aminocephalosporanic
acid derivative, which may be protected, wlth a
reactive deriva~ive of the acid of formula A,
f~
- 6 - 970-9688
N-O~l
R --C-COOH A
in which Rl and R3 are as defined above.
The various reactive derivatives that have
been proposed include activated esters. For the prod-
uc~ion of the ~y~-isomers of formula I the reactive
S derivatives of the acid of formula A should also be
in _y~-isomeric formin as high a purity as possible,
and the ~y~-configuration should as far as possible be
unaffected by the subsequent steps, in particular the
acylation step. Various reactive derivatives that
have previous:Ly been proposed, in particular activated
esters, suffer from the disadvantage that the ~y~-
configurationissomewhat unstable during production
or use thus le!ading to increased formation of the anti-
isomer and consequential reduction of the yields of the
lS desired syn-isomers.
A further difficulty that arises in the prod-
uction of the preferred compounds of formula Ia is
that in practice it is essential to protect the amino
su~stituent in the thia~olyl ring of the side-chain
prior to the acylation step. Otherwise competing
reactions canoccur leading to greatly reduced yields of
the final products. The introduction, however, of
~~
-- 7
suitable protecting groups prior to the acylation step,
and thei~ subsequent removal is in general accompanied by
redueed yield and purity of the desired final product and
not insubstantial addition reaction time, energy, effort
and cost.
Applicatîon Serial No. 374,191 provides a method
by which the desired syn-isomers may be obtained in high
purity and yield; in particular, the syn-isomers of
formula Ia may be obtained in high purity and yield
without the necessity to protect the amino substituent
in the thiazolyl ring of the side~chain.
More parti.cularly, it provides a process for the
production of syn-isomers of formula I and salts thereof,
eomprising reaeting a ~y~-isomer of formula II,
~ORl
N
R3-C-CO-S-C Het I II
in whieh Rl is as defined above,
R3 is a 5--membered oxygen- or sulphur-
eontaining heteroeyelie ring, which may be
substituted by amino, protected amino, or
azido, and
- 8 - 970-9688
-C Het~ represents a 5- or 6-membered
heterocyclic ring, which may contain in
addition to the nitrogen atom, one or
two further hetero atoms, seLected
S from oxygen, nltrogen and sulphur, and
which may be substituted or fused to a
benzene ring which may itself be sub-
stituted~
with a compound of formula III.
R5-NE~- ~ S~ III
~ N ~ CH2R4
COOR2
10in whlch R2 and R4 are as defined above,
and R5 is hydrogen or an amino protecting
group,
where required, disprotecting the resulting product, and,
where required, converting a resulting product in which
E~2 is hydrogen into a salt thereof or vice versa.
The process is suitably carried out in an
inert organic solvent, such as a chlorinated hydro-
carbon, e.g. methylene dichloride, or an ether, e~g.
ethyl acetate,or in a mixture of such solvents with
water. The reaction temperature is suitably from -40
to ~60C, in particular -15 to +25C, espcially 0'to
- 9 ~ 97~-9688
20C, and the reaction time may typically vary from 1/2
to 48 hours. The reactants of formula II or III may
conveniently be employed in stoichiometric quantitLes.
Alternatively, an excess of up to 25~ of the compound
of formula II is conveniently employed.
As indicated, the production of compounds in
which R2 is hydrogen (as well as salts thereof), the
carboxyllc acid group in the starting material of
formula II, is conveniently protected. Suitable protec-
ting ~roups are well known and include not only thosereferred t:o above as possible significances for R2, but
also sily:L ester protecting groups, in particular the
trimethylsilyl protectlng groups, which may ~or example
be introduced by reaction of the free acid with N,O-
bis-trimethylsilylacetamide.
The 7-amino group of the starting material of
formula III may, as indicated, also be protected. Again,
suitable protecting groups are well-known and include
for exarnple the trimethylsilyl group, which may for
example be introduced simultaneously when protecting
the carboxylic acid group.
~ en R3 in the desired product contains an
amino substituent in the heterocyclic ring, the corres-
ponding startlng material of formula II may ha~e this
r~
~ 10 ~ 970-9688
amino subst:ituent in free or in protected form. As dls-
cussed, in general protection is not necessary. IE
protection :is nevertheless desired, this may be accom-
plished in conventional manner, suitable protecting
S groups being well-known.
Af,ter reaction of the compounds of formula II
and III, any subsequent disprotection steps rnay be
effected in conventional manner. Likewise, inter-
conversion of the free acid (R2 = H~ and salts thereof
may be accomplished in well-known manner.
The resultlng products may be isolated and
purified usiny conventional techniques.
The process of the invention thus employs as
reactive derivatives of the acid of formula A, hetero-
cyclic thioesters. It has been surprisingly foundthat these esters may be prepared and employed
with virtually complete control of the geometry
of the --C=N- syn-configuration. Furthermore, it has
surprisingly been found that,when there is an amino
group in the heterocycli.c ring of these esters, the
esters are not self-reacting. Accordingly, protection
of this amino group in the subsequent acylation is not
essential (although oE course not ruled out if for any
reason desired).
The ~ isomers o formula II are novel and
represent the present invention. The nature of the
/ ~
-C~et, ring therein is not critical, the preferred
compounds being determined by such factors as ease
S of formation and availability of starting materials.
Preferably, however, this signifies 2-pyridyl, or,
especially, 2-benzthiazolyl. It may also be pyrimi-
dinyl, triazolyl or thiazolyl, however. The preferred
compounds of formula II correspond to the preferred end
products, namely syn isomers of formula IIa and IIb,
~ORl
2 ~ ~ C-CO-S C / ` IIa
/OCH3
N __
2 ~ \ ~ C-CO-S-C Het
~ N--' IIb
in which Rl and C ~ ~ are as defined above.
~ N
In accordance with the invention, the syn-isomers
of formula II may be prepared by esterification of a
isomer of formula IV,
~ORl
N IV
l 11
R -C-COOH
in which Rl and R3 are as defined above.
The esterification may for example be accom-
- 12 - 970-96~8
plished by reaction wl-th a compound of formula V,
~Het C-S-S-C Het I V
`N~Y ~N-
\
in which the two groups ~let C are the same and
`~
are as defined above.
The reaction is suitably effected in the
presence of a tri-(lower alkyl~- or tri(aryl) phosphine
or phosphite, in particular triphenylphosphine. The
reaction temperature may for example be from -30 to
~50C, in particular -20 to +25C, preferably -5 to
~5C. The reaction is sultably effected in an inert,
non-hydroxy-containing-, organic solvent, for example a
chlorinated hydrocarbon, such as methylene chloride.
Where a compound of formula II in which R3 is a pro~
tected-amino-substituted heterocycle is desired, the
amino protecting group may of course be introduced
prior to or subsequent to the esterification reaction.
The syn-isomers of formula I are as indicated
in general known antibiotics. In particular they are in-
dicated for use as antibacterial agents as indicated in
vitroin the series dilution test,ata concentration for
example of 0.01 to S0 ~g/ml, and ln vlvo in the mouse
at a dosage of for example from 0.1 to 100 mg/kg of
animal body weight, against a wide variety of stralns,
- 13 - 970-9688
such as Staphy]ococcus aureus, Streptococcus pyogenes,
Streptococcus faecalls, E. coli, Proteus vulgarix,
Proteus mirabilis, Proteus morganii, Shigella dysent-
eria, Shigella sonnei, Shigella flexneri, Alcaligenes
faecalis, Klebsiella aerogenes, Klebsiella penumoniae,
Serrata marcescens, Salmonella Heidelberg, Salmonella
typhinuriurn, Salmonella enteritidis and Neuseria
gonorrhoae.
The compounds are therefore useful as bact-
erially active antibio~ics. For this usage, the
dosage will of course vary depending on the compound
employed, mode of administration and treatment desired.
Howev~r, in general, satisfactory results are obtained
when administered at a daily dosage of from 1 to 6 g
conveniently given in divided dosages of from about 0.25
to about 3 g of the compound two to four times daily, or
in sustained release form.
The compounds in which R2 is hydrogen may be
employed in free acid form or in the form of their
physiologically acceptable salts, which salt forms have
~ 9~0-9688
the same order of activity as the free aci.d forms.
Suitable salt forms include alkall metal and alkaline
earth metal salt ~Q~S~in particular alkali metal,
such as sodium salt forms. The compounds may be admixed
with conventîonal pharmaceutically acceptable diluents
and carriers and optionally other excipients and admin-
istered in such forms as capsules or injectable prep-
arations.
The followlng Examples in which all temper~
atures are in degrees Centigrade, illustrate the
i.nvention.
- 15 - 970-9688
EXAMPI.E 1: 7-t[2-(2-~ninothiazol-4-yl)-2-syn-methox-
imlno]acetamido~cephalosporanic acid
[Cefotaxim]
2.72 g of 7-Aminocephalosporanic acid are
suspended ln 50 ml of methylene dichloride. 3.5 ml of
N,O-bis-(-trimethylsilyl)acetamide are added and the
mixture is stirred at room temperature until a clear
solution is obtained. 3.5 g of 2-(2-aminothiazol-4-yl~-
2-syn-metho:cimino acetic acid 2-benthLazolyl thioester
are added and the mixture is stirred for 15 hours at
room temperature. The solution is then extracted with
2 cJ of ~HCO3 and 40 ml of water and the phases are
separated. The aqueous phase is extracted with a mix-
ture of ethyl acetate/n-butanol (8/2) at p~l 2 and
before phase separation, the aqueous phase is satur-
ated with (NH4)2SO4. The organic phase is washed twice
with 100 ml of NaCl solution and evaporated to dryness.
The crystalline residue is shaken with 100 ml of diethyl
ether, filtered and washed with ether. The title
product is obtained. M.P. 20~ (decomp.). Yield 4.2 cJ;
92~ of theory ~ased on pure ~X~ isomer.
EXAMPLE 2: 7-- [2-(2-~ninothiazol-~yl)-2=syn- ethox-
~ .
imino]acetamido ce~halosporanic acid
[Cefotaxim]
- 16 - 970-9688
2.72 g of 7-~minocephalospQranic acid are
suspended in 40 ml of methylene dichloride and 2.75 ml
of N,O-bis-(trimethylsilyl)acetamide are added, drop-
wise. The mixture is stirred until a clear solution is
obtained. 2.9 g of 2-(2-aminothiazol-4-yl)-2-~
methaminoacetic acid 2-pyridyl thioester are added, the
mixture is cooled to 10 D and stirred at this temper-
ature for 24 hours. 2 g of KHCO3 in 40 ml of water are
added and the mixture is stirred for 30 minutes and the
aqueous phase i6 separated. This is layered with a
mixture of n-butanol/ethyl acetate and the pH of the
mixture is adjusted to 2. The organic phase is evapor-
ated in vacuo and the residue is mixed with ether. The
precipitated crystalline heading compound is filtered
off, washed with ether and dried. ~.P. 205 (decom~.).
Yield 4.1g; 90% of theory based on pure ~y~ isomer.
EXAMPLE 3: 7-~2--(2-Aminothia ~ )-2-syn-
methoximino]acetamido~3-~[(2~5-dihydro--6-
_y~oxy-2-methyl-5-oxo-a,s-triazin-3-yl)
thio]methyl}-3-ce~em-4-carboxylic acid
Ceftriaxon
3.71 g of 7-Amino-3-(2,5-dihydro-2-methyl-6-
hydroxy-5-oxo-a,s-triazin-3-yl)thiomethyl-3-cephem-4-
carboxylic acid are suspended in 50 ml oE dry methylene
chloride under an inert gas atmosphere. ~3 ml of N,O-
- 17 - 970-9688
bis (trimethylsllyl)acetamide are added, with stirring,
and the mixture is stirred for 30 minutes when a
clear solution is formed which is then cooled to +15C.
9 g of 2-(2-aminothiaz.ol-4-yl)-2-~-methoximino acetic
acid 2-benzthiazolyl thioester are added and the mix-
ture is stlrred for5hours a-t 15 to 20, whereupon a
clear solution is forrrled. The mixture is then cooled
to 0C and poured into a solution of 3 ml of methanol
in 120 ml of acetonitrile, pre-cooled to 0. From the
xesulting initially clear solution, a light precipitate
is formed on further stirring at 0 to 5 and this is
filtered off and washed with acetonitrile. After
drying in vacuum at 50C, 4.7 g (85%) of substantially
pure title compound are obtained, in the form of the
free acid, m.p. ~120C (decomp.).
EXAMPLE 4: 7-~[2-Amunothiazol-4-yl)-2-syn-methoxirnino]-
acetamido~-3-(1-methyl-lH-tetrazol-5-yl~-
thiometh~1-3-cephem-4-carbox~lic acid
[SCE 1365]
In manner analogous to that of any one of
Examples 1 to 3, employing appropriate starting mater-
ials in approximately equivalent amounts, the heading
compound may be obtained.
- 1~ - 970-9688
EXAMPLE 5: 2-(2-Aminothiazol-9-yl?-2-syn~methoxlmino-
acetic acid_2~yridyl thioester
~Compound II]
26 g of triphenylphosphine are dissolved in
130 ml of methylene dichloride and 22 g of 2,2-dithio-
pyridine are added. The mixture is stirred at room
temperature for lS minutes and then cooled to 0. lOg
of finely powdered 2-(2-aminothiazol-4-yl)-2-~y~-
methoximinoacetic acid are then added in portions over
1 hour. The mlxture is seeded and cooled for 3 hours
at 0, whereby the heading compound crystallises out.
This is filtered and washed with cold met~len~ chloride;
m.p. 112; yield 16.4 g - 98% of theory based on pure
syn isomer.
15 EXAMPLE 6: 2-(2-Aminothiaæol-4-Y1)-2-syn-methoximlno
. . _ . _ . _ . ~ . . _ = . _
acetio acid 2-benzothiazolyl_thioester
[Compound II]
3.93 g of Triphenylphosphine and 5 g of ~is-
[ben~thiazolyl-(2)]disulphide are suspended in 50 ml
of methylene dicl-loride and tl-e suspension is stirred
for 30 minutes at room temperature. A~ter cooling to
0, 2 g of 2-(2~aminothiazol-4-yl)-2-~y~-methoximino-
acetic acid are added and the mixture is stirred for 3
to 4 hours at 0. The insolubles are filtered off and
- 19 - 970-968~
washed with a little cold methylene dichloride. The
solid is suspended in 25 ml of ethyl acetate and the
suspension is stlrred ior 30 minutes at 0, filtered
and washed wlth ethyl acetate to obtain the heading
compound, m.p. 128-13() (from tetrahydrofuran/methyl-
ene dichloride).
