NO146397B - ANALOGY PROCEDURE FOR THE PREPARATION OF THERAPEUTIC ACTIVE NITROIMIDAZOLYLVINYLTIADIAZOLES - Google Patents

Description

The object of the invention is the production of nitroimidazolylvinylthiadiazoles, which are used as chemotherapeutics for the treatment of microbial infections in humans and animals.

It is known that nitroheterocyclic compounds, such as nitrofurans, nitrothiazoles or nitroimidazoles, are effective

some agents against bacteria, fungi and protozoa. The minimum concentrations that have an inhibitory effect in known preparations, for example "Metronidazole" or "Tinidazole", are in the order of magnitude between 0.1 and 2 µg/ml. Their effect and conciliatory

however, it is not always satisfactory. It pre-

there is therefore a desire to synthesize new substances with better effects.

It was now found that compounds of the formula I

where R 2 means hydrogen or methyl, and R 3 means hydrogen,

methyl, ethyl, phenyl or pyridyl, exhibit valuable pharmacological properties.

The compounds are produced according to the invention by

in a manner known per se reacts 2-substituted 1,3,4-thiadiazoles with the general formula II

2 3 where R and R have the same meaning as above, with 1-methyl-5-nitroimidazole-2-carboxaldehyde of the general formula III

or its acetal or acylal, in the usual way using elevated temperatures and optionally carrying out the reaction in the presence of an acidic condensation catalyst and optionally a solvent. Aldehydes of the formula III can also be used as acetals or acylals, in particular such acetals which are obtained by reaction with methanol and ethanol, and the acetal which is formed by reaction with acetic acid.

The reaction can be illustrated by the following reaction equation:

The 1,3,4-thiadiazoles of formula II used

as starting compounds, are in part known compounds, or they can be prepared without further ado, for example according to that of R. Stollé, Ber. dtsch. chem. Ges. 32, 797 (1899) described method. N,N'-diacylhydrazines are then reacted with & 2S5 in an aromatic hydrocarbon, such as xylene, at an elevated temperature.

The method according to the invention for the preparation of the compounds I can conveniently be carried out by combining a compound of the formula II with a compound of the formula III or acetal or acyl thereof at temperatures between 50

and 220°C, suitably in the presence of an acidic condensation catalyst, for example a Lewis acid, a mineral acid or an acidic ion exchanger, and optionally in the presence of a solvent.

The preferred temperature range lies when using a solvent between 90 and 150°C, in the absence of solvent at 150-200°C.

As catalysts, it can be used for aldehyde condensations in per se known acid condensation catalysts,

which are used in amounts of 0.005-1 mol, preferably 0.05 -

0.2 mol of catalyst per moles of starting material II. Acidic condensation catalysts are, for example, polyphosphoric acid, boron fluoride or zinc chloride. The preferred catalyst is zinc chloride.

The starting materials are generally used in stoichiometric ratios, but an excess of one of the compounds can also be used. The reaction generally takes place at normal pressure, but overpressure or underpressure can in special cases be advantageous. The reaction can be carried out with or without a solvent. As a solvent, lower carboxylic acids, such as acetic acid or propionic acid, their anhydrides and mixtures of a lower carboxylic acid and the corresponding anhydride proved to be well suited. When using mixtures of carboxylic acid and carboxylic anhydride, the ratio is suitably between 9:1 and 1:9.

In general, the reaction will be complete in a few hours. The work-up does not cause any difficulties? it can be done, for example, by adding a trapping agent, weathered water or acetone, to the reaction mixture, the reaction product is precipitated, filtered off, washed with water and alcohol and recrystallized from a suitable solvent.

The compounds I show a good effect against micro-organisms. They show an outstanding effect in the treatment of infections caused by flagellates, especially trichomonads and trypanosomes, and Entamoaba histolytica in humans and animals.

They can also act very well antibacterially in limit concentrations <10 5 , for example the compounds according to examples 6 and 7.

A number of experiments, including comparison experiments, have been carried out, in vitro and in vivo, which show the effectiveness of the compounds I. The experiments are described in more detail below, and the results of the comparison experiments are compiled in Table 1, where the compound I used is indicated by reference to the examples given later. (Results from experiments in vivo cannot be easily compared with results in vitro, and these two groups of experiments must be considered separately).

Comparison between the compound in Example 1 in Norwegian patent no. 135,420, the commercial product "Metronidazole" and compound I according to Example 7 below.

Female albino mice (NMRJ strain) infected with Trichomonas vaginalis were used in the experiments. In each experiment, 10 mice were used, weight 18-22 g, and the infection was carried out with 2.5 million Trichomonas vaginalis in 0.5 ml of 0.5 percent tragacanth suspension.

From the third day after infection, the mice were treated once a day for 5 days with the relevant active substance per os. As a dose, 4 6.4 mg/kg of respectively "Metronidazole" and the compound in example 1 in patent 135,420 were used, while the dose was

21.5 mg/kg of compound I in Example 7 below.

Two days after the last medication, the experimental animals were examined: 1. By microscopic detection of trichomonads still present in the secretion from the infected abscess area. It was found that of the 10 mice that had been treated with the compound according to Example 1 in the patent, 5 were still positively attacked. Of the 10 experimental animals which were respectively treated with "Metronidazole" and the compound I according to Example 9, none were positively attacked (no longer

any infection).

2. When using cultures inoculated with secretions from the abscess area. This is a more important detection method. It was found that all 10 experimental animals that had been treated with the compound according to Example 1 in patent 135,420 were still attacked, while none of the animals that had been treated with respectively "Metronidazole" and the compound I according to Example 7 were positively attacked.

The above experiments in vivo show that the compound according to Example 1 in Norwegian patent no. 135,420 was less active than the commercial product "Metronidazole" at the same dosage, and that the compound I according to Example 7 used with a significantly lower dosage was as active as "Metronidazole".

It was surprising that the introduction of a thiadiazole residue attached via an ethylene bridge improves the effectiveness of known commercial products against trichomonad infections, for example "Metronidazole" and "Tinidazole", to a maximum of over 10-fold.

As regards the action against trichomonads, the compounds in examples 1, 3, 5 and 7 can be highlighted in particular.

The effect against infections by trypanosomes and Entamoeba histolytica can be shown by experiments with mice (NMRJ strains) using methods described in Handbuch fiir experi-mentelle Pharmakologie (mentioned above).

1. Trypanosoma brucei - infection in mice.

Different dosages are tested. Healing was confirmed microscopically and by means of cultures. In addition, a post-observation was carried out for 25 days after the end of treatment with the aim of finding any cases of relapse.

example 1 11 x 50 mg/kg peroral, acute 100% effect,

70% relapse,

example 2 11 x 50 mg/kg peroral, no effect example 3 11 x 50 mg/kg peroral, no effect example 7 11 x 25 mg/kg peroral, acute 100% effect,

no relapse, example n 11 x 50 mg/kg orally, no effect,

example 5 11 x 50 mg/kg per.oral, acute 100% effect,

30% relapse.

'Suramin" 7x 50 mg/kg intraperitoneally, acute 80% effect,

no relapse. "Metronidazole"lix 50 mg/kg orally, no effect.

"TLnidazole" 11 x 50 mg/kg orally, no effect.

2. Trypanosoma gambiense - infections in mice.

Methodology as for trypanosoma brucei.

example 1 11 x 50 mg/kg peroral, acute 100% effect,

80% relapse.

example 2 11 x 50 mg/kg orally, no effect.

example .3 11 x 50 mg/kg orally, no effect.

example 7 11 x 50 mg/kg orally, acute 100% effect, 60%

effect.

example i| 11 x 50 mg/kg orally, no effect,

example 5 11 x 50 mg/kg orally, no effect.

"Suramin" 7 x 50 mg/kg intraperitoneally, acute 50% effect,

no effect.

3. Trypanosoma congolense - infections in mice.

Methodology as for trypanosoma brucei.

example 1 11 x 50 mg/kg peroral, acute 100% effect,

20% relapse

example 2 11 x 50 mg/kg orally, no effect,

example 3 11 x 50 mg/kg orally, no effect,

example 7 11 x 50 mg/kg peroral, acute 100% effect,

no relapse.

example k 11 x 50 mg/kg orally, no effect,

example 5 11 x 50 mg/kg orally, no effect,

suramin 7 x 50 mg/kg intraperitoneally, acute 70% effect,

no relapse.

4. Entamoeba histolytica (serial dilution test).

The strains PN and Q were tested.

The minimal inhibitory concentrations were at

example 1 <0.01 µg/ml

example 2 0.1 ug/ml

example 3 <0.01 µg/ml

example 7 <0.01 µg/ml

example A <0.01 ug/ml

example '5 <0.01 µg/ml

"Metronidazole" 0.1 yg/ml

The experiments were carried out in a tube-row dilution test

in vitro according to P. Klein, Bacteriologische Grundlagen der chemotherapeutischen Laboratoriumpraxis, Springer-Verlag Berlin - Gottingen - Heidelberg 1957.

The results show that the compounds in examples 1 and 7 due to their effect and in comparison with suramin, which is a component in example da. known preparations germanine and naganol, must be highlighted in particular. The effect against Entamoeba histolytica must also be described as very good to good in vitro. As can be seen from the table, the effect here is more than ten times as good as for the well-known 'Metronidazole'•

5. Trichomonas vaginal - infections in mice.

Different dosages were tested. Healing was confirmed microscopically and by means of cultures.

example 1 100% healing at 5 x 25 mg/kg oral example 2 10% healing at 5 x 50 mg/kg oral example 3 100% healing at 5 x 25 mg/kg oral example 7 100% healing at 5 x 25 mg/ kg oral example 4 50% healing at 5 x 50 mg/kg oral example 5 100% healing at 5 x 50 mg/kg oral "Metronidazole" 100% healing at 5x 25 mg/kg oral "Tinidazole" 100% healing at 5 x 25 mg/kg orally.

The toxicity values LD 50 which were found in the experiments with mice, strain NMRJ, by oral administration and in an observation period of 1 week, are higher than 1,500 mg/kg for the compounds in examples 1, 5 and 7.

The compounds to be used according to the invention can consequently be used in the therapeutic treatment of humans and animals against trichomoniasis, trypanosomiasis and dysentery caused by amoebae. Furthermore, they come into consideration when treating leishmaniasis.

Of the preferred active compounds, the following are mentioned: 2-phenyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole

2-(4-pyridyl)-5-[ 2-(1-methyl-5-nitroimidazol-2.-yl)-vinyl]-1,3,4-thiadiazole

2-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole 2-ethyl-5-[2-(1-methyl-5-nitroimidazol-2-yl) )-vinyl]-1,3,4-thiadiazole.

Furthermore, the following compounds are among the particularly preferred: 2-methyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole, and

2-Ethyl-5-[1-methyl-2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

Example 1

Preparation of 2-methyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

In a stirring apparatus, 11.4 g of 2,5-dimethyl-1,3,4-thiadiazole, 15.5 g of 1-methyl-5-nitroimidazole-2-carboxaldehyde are heated under reflux together with 0.2 g of zinc chloride in a mixture of 50 ml glacial acetic acid and 20 ml acetic anhydride for 10 hours. After cooling, the precipitated solid is washed with glacial acetic acid and recrystallized from dimethylformamide. 15.6 g of colored crystals with a melting point of 248°C are obtained; this corresponds to 62% of the theoretical.

Example 2

2-Phenyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

17.6 g of 2-methyl-5-phenyl-1,3,4-thiadiazole, 15.5 g of 1-methyl-5-nitroimidazole-2-carboxaldehyde and 0.5 g of ZnCl2 are heated in 100 ml of acetic acid and 50 ml of acetic anhydride in 7 hours at reflux temperature. Water is added to the reaction mixture, and the precipitated solid is recrystallized from glacial acetic acid. 17.5 g of a product melting at 257°C is obtained; this corresponds to 56% of the theoretical.

Example 3.

2-(4-pyridyl)-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

8.8 g of 2-methyl-5-(4-pyridyl)-1,3,4-thiadiazole and

7.7 g of 1-methyl-5-nitroimidazole-2-carboxaldehyde are heated together with 0.2 g of ZnCl in a mixture of 50 ml of glacial acetic acid and 25 ml of acetic anhydride for 6 hours at reflux temperature. After cooling, the precipitated solid is filtered off with suction, washed with concentrated ammonium hydroxide and recrystallized from DMF, melting point 240-241°C.

Example k

2-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

To 10 g of 2-methyl-1,3,4-thiadiazole dissolved in a mixture of 100 ml of acetic acid and 50 ml of acetic anhydride, after the addition of 0.3 g of zinc chloride, 15.5 g of 1-methyl-5-nitroimidazole- 2-carboxaldehyde, dissolved in 100 ml of acetic acid and 50 ml of acetic anhydride, during 5 hours at reflux temperature. After 24, the reaction mixture is freed from solvent by evaporation, and ether is added. After washing with water, the crude product is recrystallized from xylene. 9.3 g is obtained, corresponding to 39% of the theoretical amount. The compound melts at 214°C.

Example 5

2-Ethyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

To 12.8 g of 5-ethyl-2-methyl-1,3,4-thiadiazole and 0.5 g of ZnCl2 dissolved in 100 ml of glacial acetic acid and 50 ml of acetic anhydride is added at reflux temperature during 10 hours a solution of 15.5 g 1-methyl-5-nitroimidazole-2-carboxaldehyde in 50 ml glacial acetic acid and 25 ml acetic anhydride. The mixture is kept for a further 20 hours at reflux temperature, after which the solvent is evaporated. The residue is washed with acetone and purified in a silicic acid finished column (type A from the company Merck); it is eluted with CHCl^/-CH^OH=98: 2. 5.6 g of the above reaction product are obtained, melting point 165°C; this corresponds to 21% of the theoretical.

Example 6

2-Methyl-5-[1-methyl-2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

The acetone solution from example 7 was evaporated, the residue is placed in a silicic acid ready-made column (type A from the company Merck) and eluted with CHCl3/CH3OH=98: 2. The yield was 5.4 g, melting point 249°C. In addition, 3.4 g of the stereoisomeric compound with a melting point of 155°C are obtained.

The total yield from examples 7 and 8 amounts to

54% of the theoretical.

Example 7

2-Ethyl-5-[1-methyl-2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole.

To 17.1 g of 2,5-diethyl-1,3,4-thiadiazole, dissolved in

a mixture of 60 ml of acetic acid, 25 ml of acetic anhydride and 0.5 g of zinc chloride is added dropwise to 4.6 5 g of l-methyl-5-nitroimidazole-2-carboxaldehyde dissolved in 80 ml of glacial acetic acid and 35 ml of acetic anhydride at reflux temperature during 5 hours. After 24 hours of heating at reflux temperature, the solvent is removed by evaporation, and water is added to the reaction mixture. The precipitated reaction product is then sublimated and recrystallized from propanol. 2.9 g is obtained, corresponding to 35% of the theoretical amount. The compound melts at 125°C.

Claims (3)

1. Analogous process for the preparation of therapeutically active nitroimidazolylvinylthiadiazoles of the general formula I where R 2 means hydrogen or methyl, and R 3 means hydrogen, methyl, ethyl, phenyl or pyridyl, characterized in that a 2-substituted 1,3,4-thiadiazole of the general formula II where R 2 and R 3 have the same meaning as above, in a manner known per se is reacted with 1-methyl-5-nitroimidazole-2-carboxaldehyde or its acetal or acylal, at higher temperatures, possibly in the presence of an acidic condensation catalyst and optionally a solvent. 2. Process according to claim 1 for the preparation of 2-ethyl-5-[2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole, characterized in that 5-ethyl-2-methyl -1,3,4-thiadiazole is reacted with 1-methyl-5-nitroimidazole-2-carboxaldehyde. 3. Process according to claim 1 for the production of 2-ethyl-5-[1-methyl-2-(1-methyl-5-nitroimidazol-2-yl)-vinyl]-1,3,4-thiadiazole, characterized in that 2 ,5-diethyl-1,3,4-thiadiazole is reacted with 1-methyl-5-nitroimidazole-2-carboxaldehyde.