CA1047484A - Penicillins - Google Patents

Abstract

ABSTRACT: The p-tolyl monoester of .alpha.-carboxy-3-thienylmethyl penicillin demonstrates a high degree of oral absorption in man.

Description

This invention relates to l)enicillins, and more particularly to the p-tolyl ester of an ~-carboxy penici]lin.
The penicillin and its salts are active against Gram-positive and Gram-negative bacteria which makes them useful as therapeutic and prophylactic agents against bacterial infections in animals, including man and poultry.
U.S. Patent No. 3,853,849 claims a penicillin monoester of the - formula (I):
,.', .
'' C~ :
R.CH.CO - NH ~ S ~ CH~
I ~ N - (I~
CO.OR' o CO.O~I

or a non-toxic pharmaceutically acceptable salt thereof, wherein R is phenyl, or 3-thienyl and R' is phenyl or methylphenyl.
Such mono-esters have the advantage that they are orally absorbed in animal species, including man, where they undergo in vivo hydrolysis to produce a degree of blood level antibiotic activity due ' to the free ~-carboxy-penicillin that is not attained when thec~-carboxy-penicillin itself is orally administered tc the animal species.
The present invention is based on the discovery that the p-tolyl monoester of ~-carboxy-3-thienylmethyl penicillin demonstrates a high degree of oral absorbtion iD man, unpredictable from the dis-closure in the above mentioned patent.

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: -Yk .~ ' ~ . :. ,:
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" ' . ' 7~34 Accordingly this inventioll provides ~-(tolyloxycarbonyl) 3-thienylmethyl penicillin of formula (II):

Cri~

C~ - CO ~ li~ CH3 CO O CO.OH
,, I
O

(II) .:
or a non-toxic pharmaceutically acceytable salt thereof.
Suitable non-toxic sa]ts include metallic salts such as sodium potassium, calcium, and aluminium, ammonium and substituted ammonium salts, e.g. salts of such non-toxic amines as trialkylamines (including triethylamine), procaine, l-ephenamine, N,N'-dibenzylethylene-diamine, dehydroabietylamine, N,N'bis-dehydroabietylethylenediamine and other amines which have been used to form salts with benzylpenicillin.
The penicillin of formula (II) may be prepared by acylating 6-amino penici]lanic acid with a reactive acylating derivative of formula (III):
., ' , . . . . . . .

' ' ' ~ ' :
. - :
:

~ 74~4 .-:
., ~ ~ CH.CO.

.'" CO
. . I (III) . :
`. O

~'' ';:, .
,~ ~
. wherein Q in a functional group of the type used for acylatillg primary ~ amines such as a chlorine or bromine atom (i.e. III is an acyl halide), an azido group, an acyloxy or a l-imidazo].yl or N,N'-disubstituted ' isoureido group (i.e. III is an intermediate formed from mono-p-tolyl-. 3-thienylmalonate and a condensing agent such as carbonyldiimidazole or . a N,N'-disubsti.tuted carbodiimidesuch as dicyclohexylcarbodiimide).
Some of these acylating agents of formula (III) are unstable substances which are preferably freshly prepared in a suitable solvent below room . temperature and used in situ.
The penicillin of formula (II) contains one asymmetric carbon ~j .
atom and so may exist in-different spatial configurations. However, si.nce ,. all of the compounds of the formula are merely epimers or stereoisomers of each other it is to be understood they they are all covered by the definition of formula (II); thus the invention covers the D and L forms as we].l as the DL mixtures.
- The penicillin of formula (II) may be presented for biological .
use in the form of its free acid or as a non-toxic salt and this may be presented alone or in association with a suitable pharmaceutical carrier, :

, ~

'.

~47484 . . .
which term is to be interpreted in the widest sense to include such carriers as foodstuffs as well as diluents, binders, solvents, flavouring agents, colouring agents, and other conventional vehicles and additives and capsules and other carriers in the fcrm of unit dose containers. Other therapeutic agents may also be included.
It has been stated that the penicillin mono-ester of formula (II), although covered generically by the claims of U.S. patent no.

3,853,849, is unpredictably superior to the remaining esters in that patent. To support this statement, table I shows the serum concentra-tion and urinary excretion of ~-carboxy-3-thieny]methylpenicillin (hereinafter called ticarcillin) produced when the phenyl, p-tolyl, and m-tolyl esters of ticarcillin were admiDistered oral]y to a panel of human volunteers.
To obtain the resu]ts shown in table I, the three esters of ticarcillin were each given to a panel of fasting human volunteers in a syrup formulation in an amount equiva]ent to provide 400 mg. of the free ticarcillin after the expected in vivo hydrolysis. Periodic blood samples were taken from the volunteers and each assayed for ticarcillin content by a standard bio-assay technique. The urine excreted by each volunteer within the 6 hours fol]owing administration was also collected and assayed for the free ticarcillin. Both the urinary excretion level and the peak serum concentration achieved are indication of the minimum degree to which the penici]lin ester has been absorbed after oral administration and then hydrolysed in vivo.
The results achieved were as follows:

: ' ' ' ' . ~ . - . .. ..
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~7~E~-4 TABLE 1 - Ticarcil~in Esters .':
(Administration as syrup containing equivalent of 400 mg. ticarcillin) Mean serum Conccntrltion (~ l.) ~enk Urinnry ~ono- _ _ ~ serum .- ~roup20 ~0 1 hr. 1.5 2 hr. ~ hr~ conccn- ~xcrctlon min. min. hr. ()~ l-) (;J) ~. - l ~
phenyl 5.4 7.5 5.2 j~6 2~1 <~ c6 705 23 p-tolyl 5.9 ~. 6 6 ~~ ~ 9 3 ~7 <~ o 6 ~ o G 30 m-tolyl 5.6 7.~ 5.~1~,~1 2 . 6 <1~ 6 7 ~ 3 23 :
, The results show that from the esters of ticarcillin tested ! it is the p-tolyl ester which is shown to be absorbed in vivo to the si,gnifi,cantly greatest extent, as shown by the combination of the highest noted peak serum concentration and the highest noted mean urine excretion of ticarcillin produced by in vi,vo hydrolysis after absorption following oral administration.
, In order to demonstrate that the p-tolyl ester would not be predicted to be the best absorbed ester in any series of ~-carboxy penicillins, table II shows results obtained similarly to table I
for the same esters of<-carboxyben~ylpenicillin (hereinafter called carbenicillin).
[Carbenicillin is the other penicillin, the mono-esters of which are claimed in U.S. patent 3,853,849.]
~ or the results given in table (II) the mono-esters of carbenicillin were administered in the form of crystalline solids con-tai,ned in a gelatine capsu]e in an amount equivalent to provide 500 mg.
~, -6-.:

~V474~4 of the free carbenicillin. The results, obtained as for table I were as follows:

TABLE II - Carbenicillin Esters (Administration in gelatine capsule) ~ liean serum concentration (~./ml.) Pc-ik Urin~ry - mono- scruln cxcrction cater 0.5 hr. 1 hr. 2 hr. 3 hr. ~ hr. (~ l / _ phenylcl.0 7.1 3.8 0.8 <1.0 7.1 31 p-tolyl2.6 3. 3.6 1.8 ~loO 3.6 20 m-tolyl _ 5.8 4.1 _ <1.5 5.8 32 ,; .
': :

Ihe results of table II show that, in the carbenicillin ~ series, the p-tolyl ester is the least well absorbed producing only - approximately one half the peak serum concentrations of carbenicillin produced from the phenyl ester.
It is to be noted that, in any case, the carbeniclllin and ticarcillin series of esters are not comparab]e inter se in view of the different antibiotic activities as such of free carbenicillin and ticarcillin.
The invention is illustrated by the following example.

- ' - , - . :

-~ ~xample :
~ cc-(4l-MethylphenGxycarbonyl) thien-3-ylmethy] penicillin ~, Preparation 1 ., .
(a) Mono-4'-methy]phenyl 3-thieny]ma]onate "
- CO~I C02~1 Cl t 2) OH ~ C = O
,, .... 1 0 Cl~
., C~
A 5 1 flask was set up for stirring, reflux and addition vla -dropping funnel. It was charged with 3-thienylmalonic acid (372 g, 2.0 mole), diisopropyl ether (3 1), p-cresol (216 g, 210 mole) and a catalytic amount of dimethylformamide (2 ml). The mixture was stirred at ambient temperature while a solution of thionyl chloride (160 ml, ~: 10 265 g, 2.22 mole) in diisopropylether (750 ml) was added in a steady stream over 30 min. The mixture was then refluxed for 2 hours, cooled to ambient temperature and transferred to a stirred 20 1 separator.
It was washed with water (2 x 2 1), the aqueous washes being rejected.
Water (10 1) was added fGllowed by solid sodium bicarbonate (~285 g) portionwise to give pH 7 after vigorous stirring. The aqueous solu-tion was separated and the ether solution further extracted with saturated sodium bicarbonate solution (2 x 500 ml). The combi~ed aqueous extracts were washed with diethyl ether (3 x 2 1) to remove ~ 47~84 colour. The aqueous so]ution was brought to pll 1 with hydrochloric acid (2 1, 11.6N) and the precipitated oil extracted into dichloro-methane (2 x ] 1; 1 x 500 ml). These organic extracts were combined, washed with water (3 x ] 1) and dried over magnesium sulphate (200 g).
The desiccant was removed and the solvent evaporated at reduced pressure to give an oil which was dissolved in boiling benzene (1 1).
Petroleum ether (2 1, 60-80 range) was added to the hot solution which was stood in a cold room (4) overnight to crystallize. The : .
product was filtered off, washed with a benzene/60-ôO petrol mix-~; 10 ture (1 : 2) and dried at 40, then slurry washed in water ( 3 1) for 30 min., and again dried at 40.
Eight batches of various sizes were made, yields fell in the range 42-52%; melting points 105-106 lowest, 118-119~ highest;
equiva]ent weights 272-276 (requires 276); water conteDt a]ways less than 0.3~.
N.m.r. (CDC13): ~ = 10.01 (lH, s, acid proton), 7.6-6.7 (7H, m, aromatic protons), 5.04 (lH, s, methine proton); 2.32 (3H, s, methyl protons).
(b) The mono-4'-methylphenyl-3-thienyl malonate may a]so be prepared in a similar yield to (a) above by the following process:
3-Thienylmalonic acid (93.1 g, 0.5 mole), dry ether (270 ml), dimethylformamide (0.5 ml) and thionyl chloride (36.4 ml, 0.51 mole) were refluxed for 2.5 hours. The solvent was stripped in vacuo and : p-cresol (54 g, 0.5 mole) in dry ether (270 ml) added and refluxed for 2.5 hours. After allowing to cool and stand overnight the solu-tion was washed with water and worked up as before.
Yield 65 g, (47%) _g _ , . .

. :~
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, ', . ,,~ : . ' ' ,

4~
E.W. 277.0 (requires 276) Moisture content ~ 0.08Z
Kr~
~' (c) ~-(4'-Methylphenoxycarbonyl) thien-3-y]methyl penici]lin l .

': ' C!

~ ~C O 1) sOCl? > [~ \ rlo ~----~
~ S 0 2) G-~P,~ 0 C02Na r CH3 3 ,. . .
~ 2 l flask set up for reflux w.ls charged with mono~'-methyl-phenyl 3-thieny]malonate (218 g, 0.79 mole), dichloromethane (1 1), thionyl chloride (63 ml, 105 g, 0.875 mole) and dimethylformamide (0.5 ml). The mixture was brought to gentle reflu~ and then refluxed for a further two hours. After cooling slightly solvent was distilled off initially at atmospheric pressure and later at water pump pressure, the liquid temperature not being allowed to exceed 46. A further 1 1 of dichloromethane was added and distillation continued, additional solvent being added to maintain the volume until no thionyl chloride was detected in the distillate. The solvent was then distilled off completely and the residue dissolved in acetone (1.3 I).
This solution could, if necessary, be stored overnight at 0.
6-APA (171 g, 0.79 mole) was suspended in water (800 ml) and ice (200 g) added. Sodium hydroxide solution (~2N, about 400 ml) was . - ~

; carefully added with vigorous stirring to just pro~uce a clear solution '? having pH~ 8.7. This solution was added to acetone (1.6 1) containing sodium bicarbonate (103 g, 1.25 moles) and the mixtures cooled to -10.
The above acid chloride solution, cooled to -20, was added in one portion to the 6-APA solution and the mixture stirred without cooling for 1 hour, then water (320 ml) was added. The mixture was ; transferred to a separating funnel, washed with diethyl ether (3 x 1.25 1) and methyl isobutyl ketone (800 ml). More methy] isobutyl ketGne (1 1) was added and then, with vigorous stirring, hydrochloric acid (2N) to give pH 1.5. The organic phase was separated and the aqueous phase re-extracted with methyl isobutyl ketone (300 ml). The combined organic extracts were washed with saturated brine (2 x 150 m]) and then stirred with charcoal and Celite at 0 for 1 hour. After filtra-tion and thorough washing of the filter pad with fresh solvent the solution was extracted with saturated sodium bicarbonate solution to give aqueous pH 6.8. The organic phase was extracted with water (100 ml) -~ which was combined with the previous extract and evaporated at reduced ; pressure and 25 to remove dissolved solvent.
The pH was checked and adjusted if necessary to ~7.0 and the solution freeze-dried.
: In the first series four experiments gave yields in the range 46-60% (calculated as anhydrous penicillin sodium salt).
Preparation 2 Sodium 2-ethyl hexoate precipitation method Mono-4'-methylphenyl 3-thienylmalonate (27.6 g, 0.1 mole) was dissolved in dichloromethane (300 ml) and 50 ml of solvent distilled off .

~ ~ . . ' , ., . . .
~ ~' . . ..

,j~ ~
~0~7484 to ensure dryness. Dimet}ly]formamide (2 dro~s) nnd thiony~ chloride (11.9 g, 7.2 ml, 0.] mole) were added and the mixture gently refluxed for 1-1/2 hours. Solvent was distilled off at about 10 mm pressure, the internal temperature never exceeding 25. The residue was dis-solved in dry acetone (54 ml) and the solution cooled to -15.
Recrystallized 6-APA (21.6 g, 0.1 mole) was suspended in water (88 ml) and brought into solution by the careful addition of sodium hydroxide solution (~5N, about 19 ml) to give pH 8.0 to 8.5.
Acetone (89 ml) and sodium bicarbonate (23.5 g, 0.27 mole) were added, the mixture cooled to -15 and added rapidly to the above acid chloride solution.
The combined solutions were stirred for 45 minutes without further cooling and then water (150 ml) and methyl isobutyl ketone (125 ml) added. After filtration the phases were separated and the aqueous phase washed with methyl isobutyl ketone (50 ml).
The aqueous phase was covered with methyl isobutyl ketone (125 ml) and then brought to pH 1.5-2.0 by addition of hydrochloric acid (5N, about 47 ml). The phases were separated and the aqueous phase re-extracted with more methyl isobutyl ketone (50 ml). The com-bined organic phases were washed with saturated sodium chloride solution (2 x 50 ml) and then stirred for 10 minutes with anhydrous magnesium sulphate and decolorising charcoal (4 g). After filtration the solution was diluted with acetone (an equal volume) and then treated with sodium 2-etbylhexoate in ~ethyl isobutyl ketone (~2N, 50 ml). The solution was seeded, stirred gently for 2 hours and then stored at 4 for 18 hours.

.

~\
~'7~84 The precipitated product was filtered off, washed on the filter with acetone, s].urry washed with acetone, filtered and washed once more on the filter. The product was dried at 40 for 6 hours to give 32.8 g, 66% of the desired penicillin.

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.:
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Claims (10)

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

1. A process for the preparation of .alpha.-(p-tolyloxycarbonyl)-3-thienylmethyl penicillin and pharmaceutically acceptable salts thereof which process comprises acylating 6-aminopenicillanic acid with a reactive acylating derivative of formula (III):

(III) wherein Q is a functional group of the type used for acylating primary amines selected from halogen, azido, acyloxy, I-imidazolyl and N,N'-disubstituted isoureido groups and when required forming pharmaceutically acceptable salts thereof.

2. A process as claimed in claim 1 wherein the reactive acylating derivative is an acyl halide.

3. A process as claimed in claim 2 wherein the reactive acylating derivative is an acid anhydride or mixed anhydride.

4. A process as claimed in claim 1 wherein the reactive acylating derivative is an intermediate formed from mono-p-tolyl 3-thienyl-malonate and a carbonyldiimidazole or a N,N'-disubstituted carbodiimide.

5. .alpha.-(p-Tolyloxycarbonyl) 3-thienylmethyl penicillin and pharmaceutically acceptable salts thereof, whenever prepared by a process as claimed in claim 1, 2 or 3 or an obvious chemical equivalent thereof.

6. .alpha.-(p-Tolyloxycarbonyl) 3-thienylmethyl penicillin and pharmaceutically acceptable salts thereof whenever prepared by the process of claim 4 or an obvious chemical equivalent thereof.

7. A process as claimed in claim 1 wherein the pharmaceutically acceptable salts formed are selected from sodium, potassium, calcium, aluminium, ammonium, substituted ammonium and amine salts.

8. A process as claimed in claim 1 wherein the pharmaceutically acceptable salt formed is the sodium salt.

9. Pharmaceutically acceptable salts of .alpha.-(p-tolyloxycarbonyl)-3-thienylmethyl penicillin selected from sodium, potassium, calcium, aluminium, ammonium, substituted ammonium and amine salts whenever prepared by the process of claim 7 or an obvious chemical equivalent thereof.

10. The sodium salt of .alpha.-(p-tolyloxycarbonyl)-3-thienylmethyl penicillin whenever prepared by the process of claim 8 or an obvious chemical equivalent thereof.