Note: Descriptions are shown in the official language in which they were submitted.
3~
This application is a division of Canadian Patent Application
Serial No. 308,302, filed July 27, 1978.
The present invention relates to a process for the preparation
of certain ethers of clavulanic acid, to chemical intermediates in
the process, to a process for the preparation of these inter-
mediates, and to pharmaceutical compositions containing them.
Ethers of clavulanic acid are disclosed in Belgian Patent No:
847045, Japanese Patent Application No: 122725/76 and U.S. Patent
Application Serial No: 786345. U.S~ Application Serial No. 786345
corresponds to Canadian Patent Applications Nos. 263105 and 298622.
It has been found that ethyl and propyl ethers of clavulanic acid
and derivatives thereof can conveniently be prepared via the vinyl
and propenyl ethers of clavulanic acid.
Accordingly, the present invention provides a process for the
preparation of the compounds of the formula (I):
H
-- ~CH20R1
~ _N ~ (I)
`CO2H
and salts and esters thereof wherein Rl is a CH2CH3 or CH2CH2CH3
group, which process comprises the reduction of an ester o~
a compound of the formula (II):
3~
-- 2 --
` r ` CH OR (II)
` C02H
wherein R2 is a CH-CH2 or CH=CH-CH3 group and there-
after or simultaneously if desired converting the
thus-formed ester of the compound of the formula (I~
to the corresponding acid or a sal-t thereof.
Most suitably, -the reaction is performed on an ester
of the compound of the formula (II) wherein R2 is a
CH=CH2 group.
The reduction reaction is normally effected by hydro-
genation in -the presence of a catalys-t such as a trans-
ition metal catalyst, such as platinium oxide, pallad-
ium or the like. An approximately atmospheri.c pressure
of hydrogen is generally most convenient for laboratory
use, but sub-atmospheric pressures may also be employed,
so long as ex-treme conditions are avoided.
If a compound of the formula (I) ~er se or a salt
thereof is required, this may be obtained by de-esteri-
fying a suitable ester of the compound, for example, by
the hydrolysis of a methoxymethyl or like ester or by
the hydrogenation of a benzyl, p-methoxybenzyl or like
ester optionally in the presence of a base, for example,
as described in Belgian Patent No: 847045.
If desired, the hy~rogenation o~ the vinyl or propenyl
group and hydrogenolysis of the ester may occur at the
same time, by selecting a suitable catalyst and solvent,
- 3 -
for example, by using a tetrahyd-rofuran - containing
solvent sys-tem and by using a palladium or mixed platin-
ium oxide/palladium catalyst.
The compounds oE the Eormula (Il) and salts and esters
thereof form the invention of the aforementioned parent
patent application.
Preferably, R2 i~ a CH-CH2 group.
Suitable es-ters of the compounds of the formula (II)
include those wherein the esterifying moiety is a
group A1 or CHA2A3 wherein A1 is an allcyl group of
1 8 carbon atoms optionally substituted by halogen or
by a group of the formula oA4, oCoA4, SA4, So2A4
herein A4 i,5 a hydrocarbon group o~ up to 6 carbon
atoms; A is a hydrogen atom, an alkyl group of up to
4 carbon atoms or a phenyl group optionally substituted
by halogen or by a group A5 or oA5 where A5 is an alkyl
group of up to 6 carbon atoms; and A3 is a phenyl group
optionally substituted by halogen or nitro or by a
group A5 or oA5 where A5 is an alkyl group.
Preferably, the ester of the compound of the formula
(II) is such that the corresponding ester of the compound
of the formula (I) is a readily hydrolysable or hydro-
genolysable ester. Suitable esters of this type include
the methoxymethyl~ ethoxymethyl, benzyl, methoxybenzyl,
nitrobenzyl and the like esters.
A particularly preferred ester of the compounds of the
formula (II) is the p~nitrobenzyl ester.
Suitable salts of the compounds of the formula (II)
include alkali metal~ alkaline earth metal and ammonium
and substitu~ed ammonium salts.
- 4 -
Preferably, the salt is a pharmaceu-tically aeceptable
salt.
The above novel compounds possess useful
~-lactamase inhibi-tory proper-ties whlch allow them to be
utilised in antibaeterial compositions. Aeeordingly,
there is provided a pharmaceu-tical composition
whieh eomprises a compound of the formula (II) or a
pharmaeeutieally accep-table salt or ester thereof and
a pharmaceutically acceptable carrier.
The aforementioned compositions may be utilized as
deseribed in the aforementioned pa-tent speeifieations
and may advantageously contain a penicillin or
cephalosporin.
3~
~W
There is also provided a process for the prepara-
tion of the compounds of -the formula (II) and salts
and esters thereof which process comprises the reaction
of an ester of clavulanic acid with a compound of the
formula (III) or (IV):
R3 - 0 - CH = CH2 (III)
R~ - 0 - CH = CH - CH3 (IV)
wherein R3 is an alkyl group of up to 6 carbon atoms, in
the presence of mercuric ions as catalyst, and thereafter~
if desired, de-esterifying the resulting ester of the
compound of the formula (II).
Most sui-tably, R3 in formulae (III) and (IV) is an ethyl
group.
Most suitably, -the catalyst is mercuric acetate or
mercuric trifluoroacetateO
The reaction may take pl.ace in an inert organic solvent,
or if a large excess of the compound of the formula (III)
or (IV) is used, this may act as solvent.
The reaction may be effected at a non~e~treme temperature
such as about -10 to 60C, for example from about 0 to
30C.Low temperatures in this range are preferred when
using a compound of the fromula (IV).
Compounds of the formula (II) and salts thereof may ~e
formed by cleavage of the corresponding p-nitrobenzyl
ester. This cleavage may be effected using a reducing
agent which reduces the nitro group to an amino group,
for example, as described in Dutch Patent Application
No: 7702027. An example of a suitable reducing agent
* correspvnds to Belgian Patent Mo. 851821.
L3~
_ 6 _
is iron powder/ammonium chloride solution.
The follo~ing Examples illustrate this invention~
7 ~
Example 1
Benzyl 9-0-vinylclavulanate
H H
F I-- ~ ~2H~~
Co2cH2c6H5 C02CH2C6H5
Mercuric acetate (50 mg) was added to a solution of
benzyl clavulanate (1g) in ethyl vinyl ether (10 ml).
The solution was refluxed for 6 hours, then allowed
to stand at room tempera-ture for 72 hours. The solvent
was removed under vacuum and the product purified by
colwnn chromatography (Kieselgel G, cyclohexane:e-thyl
acetate 3:1). Yield 0.676g. I.r:~ max (film) 1805,
1750, 1700, 1638, 1620 cm 1. N.m.r.: ~ (CDCl3) 3.00
(1H, d, J 17Hz), 3.43 (1H, dd, J 3Hz and 17 Hz), 3.95
(1H, dd, J 7Hz and 3Hz), 4.13 (1H, dd, J 3 and 14Hz),
4.26 (2H, d, J 7Hz), 4.81 (1H, broad t~ J 7Hz), 5.05
(1H, s), 5.13 (2H, s), 5.64 (1H, d? J 3Hz), 6-33 (1H~
dd, J 14 and 7Hz), 7.27 (5H, s).
. , .;
:: :
3L~ 3e:~
_ 8 -
Example 2
Benzyl 9-0-ethylclavulanate
H H
~ C~ 6~5 ~o~2c r~
A solu-tion of benzyl 9-0-vinylclavulana-te (81 mg)
in ethy]. acetate (10 ml) was hydrogena-ted over Adams
catalyst (10 mg) for 2 hours at room temperature and
pressure. The solution was filtered and the ~iltrate
evaporated, and the product separated from starting
material by column chromatography (Kieselgel, cyclo-
hexane:ethyl acetate 3:1). Yield 54.8 mg~
I.r~rmax(film) 1805, 1750, 1700cm 1.
N.m.r.~(CDCl3) 1.16 (3H, t, J 7Hz), 2.98 (1H, d9 J
17Hz), 3.37 (2H, q, J 7Hz), 3.41 (1H, dd, J 3 and
17Hz), 4.00 (2H, d, J 7Hz), 4.79 (1H, t, J 7Hz),
5.04 (1H, s), 5.14 (2H, s) 5.62 (1H, d, J 3Hz), 7.29
(5H, s).
- 9 -
Exa~le 3
.
Me-thoxvmethyl 9-0-vinylclavulanate
H H
~ OH 2 5 ~ O--CH=CH2
`C02CH20CH3 C02CH20CH3
A mixture of methoxymethyl clavulanate (972 mg), e-thyl
vinyl ether (10 ml) and mercuric ace-tate (50 mg) was
heated at reflux, with stirring, for 3~ hours. The
mixture was allowed to stand at room temperature
5 overnight, a further portion oP methyl vinyl ether (3ml)
was added, and the mixture was refluxed for a fur-ther
hour. The solvent was removed under vacuum, and the
product was isolated using column chromatography-
(Kieselgel 60, cyclohexane:ethyl acetate 3~1) Yield
10 550 mg as a pale yellow oil.
I.r:~ max (film) 1810, 1755, 1700, 1635, 1620 cm 1
N-m-r- ~ (CDCl3) 3.05 (1H, d, J 17Hz), 3.44 (3H, s),
3.48 (1H, dd, J 3 and 17Hz), 4.97 (1H, dd, J 2 and
7Hz), 4.16 (1H, dd, J 2 and 14Hz), 4.31 (2H, d, J 7Hz),
15 4.90 (1H, broad t, J 7Hz), 5.06 (1H, broad s), 5.22
(1H, d, J 5Hz), 5.33 (1H, d, J 5Hz), 5.68 (1H, d, J
3Hz), 6.36 (1H, dd, J 7 and 14 Hz).
(i
... .
' ~ '
~z~3~3~
- 10-
.
Example 4
.
Benzyl 9-0-pro~en~Icla~ulanate
H~ H
~ ~ t ~ _ r~l ~ 0 _ CH=CHCH3
0 ~`` C N
C02CH2C6H5 H3 "C02CH2C6H5
A stirred solution of benzyl cla~ulanate (578 mg) in
ethyl propenyl ether (5 ml) was cooled to 0C and treat-
ed with mercuric trifluoroacetate (20 mg). After 2
hours at 0C, -the mixture was allowed to warm to room
temperature for 16 hours. The solvent was remcved
under reduced pressure and -the product was isolated
by column chroma-tography (Kieselgel 60, cyclohexane:
ethyl acetate 4:1) Yield 246 mg as a pale yellow
oil.
I.r:~ max (film) 1800, 1750, 1695, 1670 cm 1.
N.m.r : ~ (CDCl3) 1.45 - 1.65 (3H, m), 2.99 (1H, d, J
17HZ), 3.44 (1H, dd, J 3 and 17Hz), 4.1 - 4.5 and 4.6 -
4.95 (4H, m), 5 05 (1H, s), 5.13 (2H, s), 5.62 (1H, d,
J 3Hz), 5.8 - 6.2 (1H, m)~ 7.28 (5H, s).
(`~! )
3~
.
.
Benzyl 9-0-propy~ clavulanate
H~ H
~ ~ 3 F 1- ~ -CH2CH2CH3
`C02CH2C6H5 C02CH2C6H5
A solution of benzyl 9-0-propenylclavulanate (42.2 mg)
in ethyl acetate (3ml) was hydrogenated over Adams
catalyst (10 mg~ for 3 hours at room tempera-ture and
pressure. The solution was filtered and evaporated to
yield the title compound (40.9 mg).
1 spot by t.l.c (cyclohexaneoethyl ace-ta-te 3:1)
I-R- max(film) 1805, 1755 and 1700cm~1
N.m.rO (CDCl3) 0.88 (3H, t, J 7Hz) 1.55 (2H, sextet
J 7Hz). 2.99 (1H9 d, J 17Hz), 3.27 (2H, t, J 7Hz), 3.42
(1H, dd, J 3 and 17Hz), 3.99 (2H, d, J 7Hz), 4.78 ~1H,
broad t, 7Hz), 5.04 (1H, s), 5.14 (2H, s), 5.62 (1H, d,
J 3Hz), 7.78 (5H, s).
3~
12 _
Example 6
.
Sodium 9-0-propyl clavulanate
H H
,O ~
_ CH,= CHCH3 ~)~0 -CH2CH2CH~5
~0 CH C H 0 ~
2 2 6 5 ` C02IJa
A solution of benzyl 9-0-propenylclavulanate (117 mg)
in tetrahydrofuran (4 ml) was hydrogenated over 10%
palladium on charcoal (40 mg) at room temperature and
presssure for 10 minutes. The solution was filtered
5 through celite and the residue washed with tetrahydro-
furan. The combined filtrates were treated with a
solution of sodium bicarbonate (29.9 mg) in distilled
water (4 ml). The tetrahydrofuran was then removed
on a rotary evaporator. The residual aqueous solution
10 was extracted twice with ethyl acetate and filtered
through celite. The solution was evaporated on a rotary
evaporator and the residue dried over phosporus pent-
oxide to yield the title compound (77.5 mg).
N.m.r. (D20) 0.84 (3H, t, J 7Hz), 1.53 (2H, sextet~
J 7Hz), 3.05 (1H, d, J 17Hz), 3.41 (2H, t, J 7Hz), 3.54
(1H, dd, J 3 and 17Hz), 4.07 (2H, d, J 7Hz), 4.86 (1H,
broad t, J 7Hz), 4.91 (1H, s), 5.69 (1H, d, J 3Hz).
3~
.
Example 7
.
Pivaloylox~meth~l 9-0-vin~lclavulanate
H` H
OH ~ O-CH=CH2
N ~
~02CH20-CO-c(c~3)3 " C02CH20-CO-c(cH~3
A mixture of pivaloyloxymethyl clavulana-te (700 mg
of crude material) ethyl vinyl ether (5 ml) and mercuric
acetate (50 mg) was refluxed for 6 hours and left to
stand at room temperature overnight. The solvent was
removed under vacuum and the product isolated by column
chromatography (Kieselgel 60~ cyclohexane:ethyl acetate
3:1). Yield 19 mg.
I.r:~ max (film) 1810, 1760, 1700, 1635, 1620 cm 1
N.m.r.~ ~ (CDCl3) 1.19 (9H, s), 3.02 (1H, d, J 17Hz),
3.46 (1H, dd, J 3 and 17Hz), 3.96 (1H, dd, J 2.5 and
7Hz), 4.05 - 4.35 (3H, m), 4.84 (1H, broad t, J 7Hz),
~5.04 (1H, broad s), 5.66 (1H, d, J 3Hz)~ 5.71 (1H, d,
J 5Hz), 5.78 (1H, d, J 5Hz)~ 6.35 (1H, dd, J 7 and 14Hz).
3~0
q~ - 1 L~ - .
Example 8
Methyl 9-0-vin~clavulanate
H C2H5~ H
~OH + ¦ ¦ ~ yO~ CH=CH2
` C02CH3 ' C2CH3
A mixture of methyl clavulanate (426 mg), ethyl vinyl
ether (5 ml) and mercuric acetate (25 mg) was heated at
reflux for 4 hours. The solvent was removed on a rotary
evaporator and the produc-t purified by column chromato-
5 graphy. (Kieselgel, cyclohexane:ethyl acetate 1:1)
Yield 168 mg.
I.r.:~ ma~ (film) 1800, 1750~ 1700~ 1632~ 1618 cm 1.
N.m.r: ~ (CDCl3) 3.02 (1H~ d, J 17Hz) ~ 3.46 (1H~ dd, J
3 and 17Hz) ~ 3.74 (3H~ s) ~ 3.97 (1H~ dd, J 3 and 7Hz)
4.16 (1H~ dd~ J 3 and 14Hz) ~ 4.28 (2H~ d~ J 8Hz)
4.85 (1H, broad t9 J 8Hz), 5.04 (1H, s~ ~ 5.66 (1H, d~
J 3Hz) ~ 6.36 (1H~ dd, J 7 and 14Hz) .
Analysis: Found C 55.19, H5.70, N 5. 93%
C11H13N05 requires C 55.23~ H 5.48~ N 5.860/o.
j',,,',
(
.
~1 ~13~0
Example 9
-Nitrobenzyl 9-0-vinyl-clavulanate
p-Nitrobenzyl clavulana-te (3.34g) was dis-
solved in dry tetrahydrofuran (30ml). Ethyl vinyl
ether (50ml) and mercuric acetate (0.5g) were added
to this solution and the resulting mixture was stirred
and refluxed (bath temperature 40-50) with exclusion
of moisture for 24 hours. The mixture was filtered and
the solvent was evaporated from the filtrate to yield
a bright yellow gum. The gum was chromatographed on
silica gel (25 g) using ethyl acetate/petroleum ether
(b.p. 60-80). The appropriate fractions, which were
recognised using -t.l.c., were combined and the solvent
was evaporated to give the title compound as a pale
yellow gum (270mg). [~]20 = + 31.6 (c 1.09 CHC13).
~ max (CHCl3): 1802, 1750, 1700, 1620, 1615, 1525,
1350 cm 1 ~ (CDC13)~ 3.07 (1H, d, J 16Hz), 3 51 (1H, dd,
J 16 and 2Hz), 3.95-4.15 (2H, m) 4.32 (2H, d, J 8Hz),
4.88 (1H, t, J 8Hz), 5.15 (1H, br.s), 5.28 (2H, s),
5.70 (1H, d, J 2Hz), 6.39 (1H, dd, J 14 and 7Hz), 7.49
~2H, d, J 8.5Hz), 8.22 (2H, d, J 8.5Hz).
,
` ~ .
` ~ Z ~ 3
16 -
Example 10
Lithium 9-0-vinyl-clav~lanate
H H
0 - CH = ~~ ~ 0-CH=CH2
N ~ ~ N-~
C02CH~>No2 C02Li
p-Ni-trobenzyl 9-0-vinyl-clavulanate (190mg)
was dissolved in tetrahydrofuran (6ml~ and to the result-
ing stirred solution 1M ammonium chloride solution (6ml)
and iron powder (0.8g) were added. The mix-ture was
stirred for 20 minutes and then more iron powder (0.8g)
and 1M ammonium chloride solu-tion (0.5ml) were added.
The mixture was stirred for a further 15 minutes and was
then diluted with ethyl acetate (100ml). The resulting
mixture was stirred rapidly while hydrogen sulphide was
bubbled through it for 5 minutes. The mixture was
filtered and the solid was washed well with water. The
aqueous layer of the filtrate was saturated wi-th sodium
chloride and the mixture was filtered again. The filtrate
was treated wi-th 1N HCl (3ml), was shaken, and the layers
were separated. The organic layer was dried (sodium
sulphate) and filtered. The resulting solution was
extracted with 1/15 ~ phosphate buffer (pH 7; 3 x 30ml).
The combined extracts were overlayed with ethyl acetate
(50ml) and were treated with 1N HCl (5ml). The mixture
was shaken and the layers were separated. The organic
layer was dried (magnesium sulphate) and the solvent was
evaporated under reduced pressure. The resulting residue
was immediately dissolved in -tetrahydrofuran (5ml). This
1
.
. .~
~Z:~3~3
- 17 -
solution was diluted with water (5ml) and the pH wasadjusted to 7 by dropwise addition of 0.1M lithi~
hydroxide solution (ca 2ml). The neu-tralised solution
was ~iltered and the solvent was evaporated from the
filtrate under reduced pressure. The resulting residue
was stirred with a mix-ture of acetone (3ml) and ether
(6ml). The resulting solid was collected by filtration,
washed with ether, and dried in vacuo.
The title compound was thus obtained as a
very pale yellow powder which appeared to be 70-80%
pure as judged by t.l.c. and n.m.r.
~ max (KBr): 1770, 1690, 1610 cm 1. ~(D20); inter alia:
3.02 (1H, d, J 17Hz), 3.50 (1H) dd, J 17 and 2.5Hz),
4.00-4.25 (2H, m), 5.68 (1H, d, J 2.5Hz), 6.42 (1H, dd,
J 14 and 7Hz).
, . ~
~, ,
'~
3~6~
Demonstration of ~-Lactamase Inhibi'tory Activit~
The minimum inhibitory concentrations (MIC) of certain
compounds of this invention and of ampicillin, alone or in the
presence of compounds of the invention, were determined in vitro
for a range of micro-organisms.
The results are shown in Table 1.
- 18 -
. '
."~
3~
Table 1
Compound of Conc. MIC Ampicillin
Example No. ~g/m] ~g/ml
. ....................... _ l
. SAR KA PM EC
8 5 0.6 3.18 8
1 1.25 3.1 62.5 16
0 250 62.5500250
Compound alone 125500 250 500
0.08 3.12 2 4
1 0.3 3.12 8 8
_ 0 ~ 10001000 1 ~2000 2000
Compound alone 15.631.2 62.5 31.2
SAR : Staphylococcus aureus Russell
XA : Klebsiella aerogenes E70
PM : Proteus mirabilis C889
EC : E. coli JT39
-- 19 --
