GB1568542A - 2-(amino or acylamino)-1-(2-thiazolin-2-yl)benzimidazoles - Google Patents

Description

(54) 2-(AMINO OR ACYLAMINO)-1-(2-THIAZOLIN-2-YL) BENZYIMIDAZOLES (71) We, ELI LILLY AND COM P, a corporation of the State of Indiana, United States of America, having a principal place of business at 307 East McCarty Street, City of Indianapolis, State of Indiana, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The incidence of viral upper respiratory disease is immense. It has been estimated that neerly a billion cases annually appear in the United States alone. Studies performed in England (Tyrell and Bynoe, 1966) indicated that 74 percent of persons having colds were infected with rhinoviruses. Because more than 80 strains of rhinoviruses are already identified, the development of a practical rhinovirus vaccine is not feasible. In this, chemotherapy appears to be the more desirable approach.

The ability of chemical compounds to suppress the growth of viruses in vitro is readily demonstrated by using a virus plaque suppression test similar to that described by Siminoff, Applied Microbiology, 9(1), 66 (1961).

Certain thiazolinyl benzimidazole compounds are disclosed in the following references: U.S. Patent Specification 3,749,717 discloses 1 - thiazolinyl - 2 - (heretocyclic J benzimid- azoles useful as anthelmintic and anti-inflammatory agents.

U.S. Patent Specification 3,825,537 discloses 1 - thiazolinyl - 2 - aminobenzimidazoles useful as anthelmintic and antiinflammatory agents.

U.S. Patent Specification 3,833,574 discloses a method of preparing 1 - thiazolinylbenzimidazolin - 2 - ones which are antiinflammatory agents.

Derwent 26199W/16 discloses 1 - thiazolinyl - 2 - phenylbenzimidazoles useful as anthelmintic agents.

There is no known prior art reference to antiviral activity of thiazolinyl benzimidazoles.

It is an object of this invention to provide novel thioazolinyl benzimidazole compounds which are useful for suppressing the growth of viruses, particularly rhinoviruses, polio viruses, Coxackie viruses, echo virus, Mengo. virus, and influenza.

This invention concems the pharmacologically useful benzimidazole compounds of the general formula

wherein R is hydrogen, or C1-C4 acyl; R@ is

wherein R2 is C1-C, alkyl, C3C6 cycloalkyl (as herein defined), (C,-C6 cycloalkyl) methyl, 1 - (Cs-C, cycloalkyl)ethyl, thienyl, or phenyl; R, is C1-C7 alkyl; R4 is C,---C, alkylidene; and R1 is at the 5 or 6 position.

The compounds of formula (I) are prepared by reacting a benzimidazole compound of the general formula

wherein R2 is defined as before, with a C,- C, alkyl magnesium halide or C,-C7 alkyl lithium followed by hydrolysis to form the compounds of formula (I) wherein R1 is

optionally followed by dehydration to form the compounds of formula (I) wherein R1

and/or followed by acylation to obtain the compounds of formula (I) wherein R is C1- C4 acyl.

A preferred group of compounds are the compounds of formula (I) wherein R is hydrogen; and R2 is phenyl.

Illustrative of the preferred thiazolinyl benzimidazole compounds included in the scope of formula (I) are the following: 1 - (2 - thiazolin - 2 - yl) - 2 - amino5(6) - (a - hydroxy - ez - methylbenzyl)- benzimidazole, 1 - (2 - thiazolin - 2 - yl) - 2 - amino5(6) - (a - methylene - benzyl)benzimidazole.

1 - (2 - thiazolin - 2 - yl) - 2 - amino5(6) - (a - ethylidene - benzyl)benzimidazole.

1 - (2 - thiazolin - 2 - yl) - 2 - amino5(6) - (a - hydroxy - a - n - hexylbenzyl)benzimidazole, 1 - (2 - thiazolin - 2 - yl) - 2 - amino S(6) - (e - n - hexylidene - benzyl)benzimidazole, I - (2 - thiazolin - 2 - yl) - 2 - amino5(6) - [α - hydroxy - α - (2,4 - dimethyl3 - pentyl)benzyl]benzimidazole, 1 - (2 - thiazolin -2 - yl) 2 - amino5(6) - [α - (2,4 - dimethyl - 3 - pentylidene)benzyl]benzimidazole.

Benzimidazole forms a tautomeric mixture in which either nitrogen atom has a hydrogen attached to it. The benzimidazole reactant bearing a substituent group at the 5-position of the benzene moiety therefore has a corresponding tautomeric form with which it is in equilibrium, wherein the substituent resides alternatively at the 6-position. On replacing the hydrogen on the nitrogen atom with a substituent group, an isomer mixture is obtained. This is indicated herein by the designation 5(6) in the resulting compound.

The following definitions refer to the various terms used throughout this disclosure.

The term "6--C, alkyl" refers to methyl, ethyl, propyl and isopropyl. The term C1- C3 alkyl includes within its definition the terms "C1-C2 alkyl". The term "C1-C7 alkyl" refers to the straight and branched aliphatic radicals of one to seven carbon atoms including methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, pentyl, isopentyl, hexyl, isohexyl, heptyl, isoheptyl, 2,4-dimethyl-3 -pentyl, t-butyl, and neopentyl.

The term "thienyl" refers to the thiophene radical attached at the 2 or 3 position.

The term "C,-C4 acyl" refers to the straight and branched chain aliphatic acyl radicals of one to four carbon atoms such as formyl, acetyl, propionyl, butyryl, and 2 methylpropionyl.

The terms "Cl-C, alkylidene" refers to straight and branched radicals of one to seven carbon atoms such as methylene, ethylidene, propylidene, isopropylidene, butylidene, isobutylidene, 3 - methyl - 2 - butylidene, 2,4dimethyl - 3 - pentlidene, and n-hexylidene.

The term "C3-C6 cycloalkyl" refers to the optionally substituted saturated alicyclic rings of three to six carbon atoms such as cyclopropyl, methylcyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The term "(C,-C6 cycloalkyl)methyl" refers to a methyl radical substituted with saturated alicyclic rings of three to six carbon atoms as exemplified above in the term "C3-C6 cycloalkyl". The term "1-(C3-C6 cycloalkyl)ethyl" refers to ethyl radicals substituted on the carbon atom in the 1 position with saturated alicyclic rings of three to six carbon atoms as described above.

In the above process suitable dehydration agents are strong acids such as p-toluenesulfonic acid, sulfuric acid, trifluoroacetic acid, methanesulfonic acid, or trifluoromethanesulfonic acid. The C,--C, alkyl magnesium halide is an appropriate Grignard reagent. C,-C7 alkyl lithium also results in a product in a similar fashion to the Grignard reagent. The preferred solvents for the alkylation process are inert organic solvents such as tetrahydrofuran; aromatics, such as benzene or toluene; and ethers, such as diethyl ether.

The preferred solvents for the dehydration process are alkanes, such as hexane; aromatics such as benzene or toluene; chlorinated alkanes, such as methylene chloride or chloroform. The temperature range usually employed for the reaction is from 25 C. to the reflux temperature of the solvent.

The starting materials of formula (II) are prepared as described in our pending application No. 35134/76 (Serial No. 1562823).

The thiazolinyl benzimidazole products are isolated by conventional methods such as filtration and concentration of the filtrate to induce crystallization. Alternatively the reaction mixture can be evaporated to dryness and the residue treated with a suitable solvent such as acetone or methanol to separate and remove any insoluble material.

The solution containing the product is concentrated to crystallize the product or is evaporated to give a second residue, which residue is recrystallized from methanol for example. The benzimidazole compound is recovered by filtration or centrifuging.

The 5(6)-isomers are separable by fractional crystallization or by column chromatography. Usually the 6-isomer crystallizes first from a solution of the mixture.

The thiazolinyl benzimidazole compounds, wherein R is C,--C, acyl, can be prepared by reacting the 1 - thiazolinyl - 2 - amino5(6) - substituted - benzimidazoles prepared as above with the anhydrides of acetic propionic or butyric acid or the mixed anhydride of formic acid and acetic, propionic or butyric acid; or when R is formyl by reaction with the mixed anhydride of formic acid and acetic acid.

The following examples further illustrate the preparation of the compounds of formula (I). The term "m/e" used in characterizing the products refers to the mass-to-charge ratio of ions which appear in the mass spectra of the products. In general, the values correspond to molecular weights of the major peaks.

Example 1.

Four grams (12.4 mmole) of 1 - ( 2 (thiazolin - 2 - yl) - 2 - amino - 6 - benzoylbenzimidazole was added to 1,000 ml. of tetrahydrofuran under nitrogen at a temperature of - 10 C. To the solution was added dropwise, under nitrogen, 50 ml. (1.6 M) of n-butyl lithium in hexane. The temperature rose to - 5 C. The temperature of the solution was maintained from --59 to -10"C. for 1 hour. The solution was allowed to warm to 25"C. and maintained there for 3 hours.

The solution was poured into 1 1. of water, evaporated, washed with tetrahydrofuran, and filtered to yield, as a white solid, 4.56 g. of 1 - (thiazolin - 2 - yl) - 2 - amino - 6 (a - hydroxy - a - n - butylbenzyl)benzimidazole, m.p. 206--209"C.

Example 2.

Two grams (5.26 mmole) of 1 - (2 thiazolin - 2 - yl) - 2 - amino - 6 - (ahydroxy - a - n - butylbenzyl)benzimidazole were dissolved in 250 ml. of chloroform. To the solution was added 1.3 g. of p-toluenesulfonic acid. The mixture was refluxed for 1.5 hours. The mixture was cooled to 25"C., washed twice with saturated aqueous sodium carbonate, dried, and evaporated to yield 900 mg. of 1 - (thiazolin - 2 - yl) - 2 - amino6 - (a - n - butylidenebenzyl)benzimidazole, m.p. 177-1790C.

Example 3.

When the procedure of Example 1 was repeated using 5.0 g. (15.5 mmole) of 1 - (2 thiazolin - 2 - yl) - 2 - amino - 6 - benzoylbenzimidazole, 500 ml. of tetrahydrofuran, and 50 ml. (2.1 M in diethyl ether) of isopropyl magnesium bromide, there was obtained 1.24 g of 1 - (2 - thiazolin - 2 -yl)2 - amino - 6 - (a - hydroxy - a - isopropylbenzyl) benzimidazole, m.p. 212--215"C.

Example 4.

When the procedure of Example 2 was repeated using 1.2 g of 1 - (2 - thiazolin2 yl) - 2 - amino - 6 - (a - hydroxy - aisopropylbenzyl)benzimidazole, 250 ml. of chloroform, and 1.3 g. of p-toluenesulfonic acid, there was obtained 280 mg of 1 - (2 (thiazolin - 2 - yl) - 2 - amino - 6 - (aisopropylidenebenzyl) - benzimidazole, m.p.

242-2450C. (dec.).

Example 5.

When the procedure of Example 1 was repeated using 2.0 g. (6.22 mmole) of 1 (2 - (thiazolin - 2 - yl) - 2 - amino - 6benzoylbenzimidazole, 23 ml. (1.25 M in benzene) of ethyl lithium, and 500 ml. of tetrahydrofuran, there was obtained 2.5 g. of 1 - (2 - thiazolin - 2 - yl) - 2 - amino - 6- (a - hydroxy - a - ethylbenzyl)benzimidazole, m.p. 206--2080C. m/e 352.

Example 6.

When the procedure of Example 2 was repeated using 1 g. of 1 - (2 - thiazolin - 2 yl) - 2 - amino - 6 - (a - hydroxy - a - ethylbenzylbenzimidazole, 0.7 g. of p-toluenesulfonic acid, and 100 ml. of chloroform, there was obtained 700 mg. of crude product. The crude product was recrystallized from ethyl acetate to yield 300 mg. of 1 - (2 - thiazolin 2 - yl) - 2 - amino - 6 - (a - ethylidene benzyl)benzimidazole, m.p. 186--187"C. then resolidifies and melts at 211"C. m/e 352.

Test Methods.

African green monkey kidney cells (BSC- 1) or Hela cells (5-3) were grown in 25 cc. Falcon flasks at 37"C. in medium 199 with 5 percent inactivated fetal bovine serum (FBS), penicillin (150 units 1 ml.) and streptomycin (150 mcg./ml.). When confluent monolayers were formed, the supernatant growth medium was removed and 0.3 ml. of an appropriate dilution of virus (echo, Mengo, Coxsackie, polio, or rhinovirus) was added to each flack. After absorption for one hour at room temperature, the virus infected cell sheet was overlaid with a medium comprising one part of 1 percent "Ionagar" No. 2 (Registered Trade Mark) and one part double strength medium 199 with FBS, penicillin, and streptomycin which contains the test drug at concentrations of 100, 50, 25, 12, 6, 3 and 0 micrograms per milliliter (mcg./ml.). The flask containing no drug served as the control for the test. The stock solutions of thiazolinyl benzimidazole compounds of formula (I) were made up in dimethylsulfoxide at a concentration of 10' mcg./ml. The flasks were incubated for 72 hours at 37"C. for polio, Coxsackie, echo, and Mengo virus and 120 hours at 32"C. for rhinovirus. The influenza viruses, Ann Arbor, Maryland B, Massachusetts B, Hong Kong A, Pr-8a, and Taylor C (types A, B), were incubated for 72 hours at 370C using MDCK cells (Madin-Darby canine kidney cells). Plaques were seen in those areas where the virus infected and reproduced in the cells. A solution of 10 percent formalin and 2 percent sodium acetate was added to each flask to inactivate the virus and fix the cell sheet to the surface of the flask.

The virus plaques, irrespective of size, were counted after staining the surrounding cell areas with crystal violet. The plaque count was compared to the control count at each drug concentration. The activity of the test compound was expressed as percentage plaque reduction, or percent inhibition. Alternatively, the drug concentration which inhibits plaque formation by 50 percent indicated by the symbol 1u can be used as a measure of activity.

Test results are expressed in terms of Polio virus type I inhibition because the virus is easy to grow and consistent test results are obtained. However, the activity of the compounds of formula (I) was confirmed against other virus cultures such as Coxsackie (A9, A21, B5), echo virus (strains 14), Mengo, rhinovirus (25 strains) Polio (type I, II, III), and influenza viruses such as Ann Arbor, Maryland B, Massachusetts B, Hong Kong A, Pr-8A and Taylor C (types A, B). Test results for various thiazolinyl benzimidazole compounds are summarized in Table I below: In the table, column 1 gives the Example number from the previous chemical examples, column 2 gives the isomer position, and columns 3-10 indicate the percent virus plaque reduction at drug dilutions from 0.75 -100 micrograms per milliliter (mcg/ml).

TABLE I.

Polio I Plaque Reduction of 1-(Thiazolin-2-yl)-2-amino-5(6)-substituted-benzimidazoles

Drug Concentration (mcg/ml)* Example No. Isomer** 100 50 25 12 6 3 1.5 0.75 5 6 toxic toxic sl.**** 86 43 19 0 0 toxic 1 6 toxic toxic toxic toxic 74 26 7 0 3 6 toxic toxic mod.*** 87 0 0 0 0 toxic 4 6 toxic toxic mod. mod 100 100 78 22 toxic toxic 2 6 33 0 0 0 0 0 0 0 * Drug concentration in micrograms per milliliter ** Number 5 or 6 indicates respective isomer *** moderate toxicity observed **** slight toxicity observed The 1-thiazolinylbenzimidazole compounds were tested both as pure compounds and as isomer mixtures. Both isomers inhibit virus growth, the 6-isomer generally being more active than the 5-isomer.

Compounds coming within the scope of formula (I) are able to suppress the growth of several viruses when added to a medium im which the virus is growing. The compounds of formula (I) can therefore be used in aqueous solution, preferably with a surfactant, to decontaminate surfaces on which polio, Coxsackie, rhinovirus, and influenza viruses are present, such surfaces including hospital glassware, hospital working surfaces and similar areas used for the preparation of food.

Furthermore, the compounds can be orally administered to warm-blooded animals and humans in a dose of 1 to 300 mg./kg. of animal body weight. The administration can be repeated periodically as needed. In accordance with general practice, the antiviral compound can be administered every four to six hours.

Preferably, the compounds of formula (I) are used in combination with one or more adjuvants suited to the particular route of administration. Thus, in the case of oral administration, the compound is modified with pharmaceutical diluents or carriers such as lactose, sucrose, starch powder, cellulose, talc, magnesium stearate, magnesium oxide, cal- cium sulfate, acacia powder, gelatin, sodium alginate, sodium benzoate and stearic acid.

Such compositions can be formulated as tablets or enclosed in capsules for convenient administration. In addition, the compounds can be administered parenterafly.

The compounds can also be mixed with a liquid and administered as nose drops or intranasal spray.

Claims (8)

WHAT WE CLAIM IS:

1. A compound of the general folmula

wherein R is hydrogen, or C,---C4 acyl; Rl is

wherein R2 is C1-C8 alkyl, Ca-C6 cycloalkyl (as herein defined), (Ca-C6 cycloalkyl) methyl, 1 - (C,-C6 cycloalkyl)ethyl, thienyl, or phenyl; Rs is C1--C, alkyl; R4 is C1-C, alkylidene; and R1 is at the 5 or 6 position.

2. A compound of claim 1 wherein R is hydrogen; and Ra is phenyl.

3. Any one of the following compounds of claim 1: 1 - (2 - (thiazolin - 2 - yl) - 2 - amino 6 - (a - hydroxy - a - n - butylbenzyl)benzimidazole, 1 - (2 - (thiazolin - 2 - yl) - 2 - amino6 - (a - n butylidene - benzyl)benzimidazole, 1 - (2 - thiazolin - 2 - yl) - 2 - amino6 - (a - hydroxy - a - isopropylbenzyl)benzimidazole, 1 - (2 - (thiazolin - 2 - yl) - 2 - amino6 - (a - isopropylidene - benzyl(benzimidazole, 1 -(2 - thiazolin - 2 - yl) - 2 - amino 6 - (α - hydroxy - α -ethylbenzyl)benzimidazole, 1 - (2 - thiazolin - 2 - yl) - 2 - amino - 6 (a - ethylidenebenzyl) benzimidazole.

4. A process for preparing the compounds of claim 1 which comprises reacting a compound of the general formula

wherein Ra is defined as in claim 1, with a C1C7 alkyl magnesium halide or Ca-C, alkyl lithium followed by hydrolysis to form the compounds of formula (I) wherein Ra is

optionally followed by dehydration to form the compounds of formula (I) wherein R, is

and/or followed by acylation to obtain the compounds of formula (I) wherein R is C, C4 acyl.

5. A compound as claimed in claim 1, substantially as hereinbefore described with particular reference to any one of the Examples.

6. A process as claimed in claim 4, substantially as hereinbefore described with particular reference to any one of the Examples.

7. A compound of formula I wherever prepared by a process according to claim 4 or 6.

8. A pharmaceutical formulation containing as an active ingredient a compound of formula I as claimed in any one of claims 1 to 3, 5 or 7.