[Advances in the development of new antitubercular agents from a group of 5-membered heterocyclic compounds containing various heteroatoms]

Tuberculosis and other antimycobacterial diseases are considered to be one of the most important problems of the health service at present. Since 1985, and in particular in the 1990s, a search for new structures of antimycobacterial substances has ranked among the prior fields of chemotherapeutic research. The present review paper links up with the previous communications, and surveys the studies carried out in the field of five-membered heterocyclic compounds containing more heteroatoms since 1984. The most frequently investigated field is thiazole derivatives but the most successful papers originated in the group of oxazoles, where effective antituberculotics for clinical use can be expected in the future. The present research is based on the journal Chemical Abstracts and original papers.

[Advances in the development of new antitubercular agents from a group of 5-membered heterocyclic compounds containing one type of heteroatom]

Tuberculosis and other mycobacterial diseases are considered at present to be one of the prominent problems of health services. Since 1985, and in particular in the 1990s, a search for new structures of antimycobacterial drugs is one of the first and foremost fields of chemotherapeutic research. The present review paper surveys the studies carried out in the field of five-membered heterocyclic compounds containing one species of the heteroatom (furan, thiophene, pyrrol, diazoles, triazoles, tetrazoles, indol, carbazol, and other more complex cyclic compounds of nitrogen and sulfur) since 1984, making use of the journal Chemical Abstracts and original papers.

Fused 1,2-dithioles, V: Carbenoid anions as intermediates in reactions of pyrrothines and their heteroanalogues

Pyrrothines like thiolutine and other bicyclic 1,2-dithioles of type 1 when unsubstituted in 3-position are marked by their CH acidity. In the presence of weak bases such as triethylamine the pyrrothine 4 degraded via its anion to a thioketene trapped as the 1,3-dithietane 5. The carbenoid anions of several compounds 1 reacted with elemental sulphur forming enthiolates whose alkylation led to the corresponding thioethers or, in the case of the thiolactam 9, to the bicyclic trithiones 10 and 11. In the same manner selenides can be obtained via intermediate selenolate ions. Introduction of an aryl- or heteroarylmercapto group into compounds 1 was achieved directly by reaction of the corresponding anions with suitable disulphides. Though there may be structural limitations, this sulphurization reaction can be extended to 3-unsubstituted trithiones. The new compounds exhibited significant activity against Mycobacterium tuberculosis in the primary screening.

Substituent Effects on Conformational Equilibria: Substituted Thiobenzanilides

Infrared absorption spectra of 38 thiobenzanilides in tetrachloromethane solutions were recorded in the ν(N-H) region. From the integrated absorption intensity of the computer-resolved N-H bands, the abundance of the Z and E conformations was calculated. The values of pertinent log KC depend on substitution in an unexpected way which cannot be described by the Hammett equation or by any other known type of modified constants σ. The only regularity observed is that the substituent effects from the two benzene rings of thioanilide are additive with a remarkable precision. The ν(N-H) frequencies are not much sensitive to substitution and the dependence is not simple: only ν(N-H) of the E conformer depend on substitution in a regular way.

Relationships Between the Chemical Structure of Substances and Their Antimycobacterial Activity Against Atypical Strains. Part 18. 3-Phenyl-2H-1,3-benzoxazine-2,4(3H)-diones and Isosteric 3-Phenylquinazoline-2,4(1H,3H)-diones

A series of 3-phenyl-2H-1,3-benzoxazine-2,4(3H)-diones 2 and 3-phenylquinazoline-2,4(1H,3H)-diones 5 substituted on the phenyl rings were synthesized. The target compounds as well as the intermediates were tested against Mycobacterium tuberculosis, M. kansasii, and M. avium. The replacement of the oxygen atom by nitrogen resulted in a decrease or loss of antimycobacterial activity. 2-[(Ethoxycarbonyl)amino]benzanilides 4 appeared to be inactive. Salicylanilides 1 and 3-phenyl-2H-1,3-benzoxazine-2,4(3H)-diones 2 exhibit significant activity against both M. tuberculosis and nontuberculous mycobacteria (the MICs within the range of 4-250 μmol/l for all compounds). The antimycobacterial activity of the compounds increases with increasing both electron-withdrawing properties and hydrophobicity of the substituent(s) on the phenyl moiety. The antimycobacterial profile of the compounds was analyzed according to the criteria based on vector algebra, such as cosine coefficients. Moreover, salicylanilides 1 exhibit activity against other microorganisms tested by the agar diffusion method.

Synthesis and Antimicrobial Activity of New 4-(Benzylsulfanyl)pyridine Derivatives

A series of 4-(benzylsulfanyl)pyridine-2-carbonitriles 2 and 4-(benzylsulfanyl)pyridine-2- carbothioamides 3 was synthesized and their antimycobacterial and antifungal activities were tested. The prepared compounds exhibit significant activity both against M. tuberculosis and nontuberculous mycobacteria. The most active compounds show the MICs of 4 μmol/l. The antifungal activities of 2 are very weak, compounds 3 are inactive against all the tested fungi.

Antimycobacterial activity of 3'- and 4'-fluorothiobenzanilides

On the basis of a preliminary study of the antimycobacterial activity of thiobenzanilides, a group of 3'-fluoro- and 4'-fluorothiobenzanilides has been synthesized and tested against Mycobacterium tuberculosis, M. kansasii, M. avium and M. fortuitum. The results of this study demonstrate that electron withdrawing groups increase the activity of thiobenzanilides and fluoro benzothioanilides against atypical strains which is higher then that of INH.

[Relation between chemical structure and antimycobacterial activity against atypical strains. XIII. Thiosalicylanilides]

On the basis of a preliminary study of antimycobacterial activity of thiobenzanilides a series of eight thiosalicylanilides have been prepared. Synthetized compounds have been examined in vitro against Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium avium and Mycobacterium fortuitum. All compounds have been found very active. The values of minimal inhibitory concentrations are summarized in Table 1. 3',4'-Salicylanilide was selected for the following research. The compound have been found inactive in vivo (on experimental murine tuberculosis).

Relationships between the chemical structure of antimycobacterial substances and their activity against atypical strains. Part 14: 3-Aryl-6,8-dihalogeno-2H-1,3-benzoxazine-2,4(3H)-diones

A set of eight derivatives of 6,8-dichloro-3-phenyl-2H-benzoxazine-2,4(3H)-dione and nine derivatives of 6,8-dibromo-3-phenyl-2H-1, 3-benzoxazine-2,4(3H)-dione, substituted on the phenyl ring, was prepared by the reaction of the corresponding salicylanilides with ethyl chloroformate. The compounds were evaluated in vitro for antimycobacterial activity against Mycobacterium tuberculosis, Mycobacterium kansasii, and Mycobacterium avium. Their activity increases with increasing hydrophobicity and electron-withdrawing ability of the substituents on the phenyl ring.

Antimycobacterial activity of some 2,3-dianilinoquinoxaline derivatives

The antimycobacterial activity of 2,3-dianilinoquinoxaline derivatives was studied and the substances were found to be mostly wide-spectrum antimycobacterial agents. Replacement of one nitrogen atom in the heterocycle for oxygen or sulfur was usually accompanied by loss of activity. The model structure for the study was the wide-spectrum antimycobacterial drug clofazimine.

[Biological effects of substances similar to salicylanilides benzanilides]

The present review paper is the first collected communication about biological activity of benzanilides. The substances of the above-mentioned structures show a number of activities (antibacterial, ref. 1-22; antituberculous, ref. 23-25; antimycotic, ref. 26-95; antiviral, ref. 96-98, antiprotozoan, ref. 97; anthelmintic, ref. 37, 99-100; insecticidal, ref. 31, 37, 101-104; herbicidal, ref. 106-130, antitumour, ref. 131-137; immunosuppressive, ref. 134, 138; hypnotic, ref. 140; anticonvulsive, ref. 141-151, anti-inflammatory, ref. 152; local-anaesthetic, ref. 155-156; antiarrhythmic, ref. 155, 158; vasodilating, ref. 159; antiulcerative, ref. 160; anti-androgenic, ref. 161; hypoglycemic ref. 162). Only very few of them have been hitherto introduced into practice. Papers investigating biological activity of benzanilides can be encountered also at present.

Effect of 2-Alkylthio-4-pyridinecarbothiamides on Photosynthetic Electron Transport in Spinach Chloroplasts

2-Alkylthio-4-pyridinecarbothiamides (1) inhibit photosynthetic electron transport in spinach chloroplasts. The dependence of photosynthesis-inhibiting activity upon the lipophilicity of 2-alkylthio substituent shows quasi-parabolic course with maximum effectiveness at 2-octyl derivative. The site of action of 1 is the intermediate D+, corresponding to tyrosine radical, which is situated in D2 protein on the donor side of photosystem 2.

Combination of the Topliss Approach with the Free-Wilson Analysis in the Study of Antimycobacterial Activityof 4-Alkylthiobenzanilides

On the basis of a preliminary study of the antimycobacterial activity of thiobenzanilides, a group of 4'-isopropyl- and 4'-butylthiobenzanilides have been synthesized and tested against Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium avium and Mycobacterium fortuitum. The effect of the substituents on minimum inhibitory concentrations was calculated by the Free-Wilson method. The separated values were analyzed by the Topliss approach. The substitution of the thiobenzanilide in position 4' by the isopropyl group or butyl group increased the antimycobacterial activity less than the cyclohexyl group. The substitution in position 4 decreased the activity by the steric effect.

Research on antifungal and antimycobacterial agents. Synthesis and activity of 4-alkylthiopyridine-2-carbothioamides

A series of 4-alkylthiopyridine-2-carbothioamides have been prepared and evaluated in vitro for antimicrobial activity. Chemical structures have been demonstrated by IR and 1H NMR data and by elemental analysis. The antimycobacterial activity of these compounds against Mycobacterium tuberculosis, Mycobacterium kansasii, Mycobacterium avium, and Mycobacterium fortuitum, and the antifungal activity against Candida albicans, Candida tropicalis, Candida krusei, Candida glabrata, Trichosporon beigelii, Trichophyton mentagrophytes, Aspergillus fumigatus, and Absidia corymbifera were determined by the MIC values. Compounds 3 exhibit good antimycobacterial activity compared to isoniazide. A moderate antifungal activity was observed against T. mentagrophytes. Activity is influenced by hydrophobicity of the alkyl group.

New Groups of Potential Antituberculotics: 5-Alkylthio-1-aryltetrazoles

A series of 5-alkylthio-1-aryltetrazoles 1-14 was prepared by alkylation of the corresponding 1-aryltetrazole-5-thiols with alkyl bromides in the cyclohexane-aqueous potassium hydroxide system. The new compounds were evaluated for their activity against Mycobacterium tuberculosis, M. kansasii, M. avium and M. fortuitum. The effects of aryl and alkyl fragments on minimum inhibitory concentrations (MIC) against M. tuberculosis and M. kansasii were analyzed by Free-Wilson method. On basis of calculated fragment contributions, 5-butylthio-1-(3,4-dimethylphenyl)tetrazole (15) was predicted to be the most antimycobacterially active derivative in the present series studied and its activity was verified experimentally. MIC values of 30 μmol l-1 and 61 μmol l-1 were obtained for its activity against M. tuberculosis and M. kansasii, respectively.

New Groups of Potential Antituberculotics: Bis(1-aryltetrazol-5-yl) Disulfides. Structure Activity Relationship

Oxidation of 1-aryltetrazole-5-thiols afforded bis(1-aryltetrazol-5-yl) disulfides. The compounds were tested for antimycobacterial activity against Mycobacterium tuberculosis, M. kansasii, M. avium and M. fortuitum. In the case of M. tuberculosis, the logarithm of minimum inhibitory concentration showed a parabolic dependence on hydrophobic substituent constants. Although the compounds exhibited low to medium activity, the most active derivative, bis(4-chlorophenyltetrazol-5-yl) disulfide (III) was more effective against atypical strains than are the commercial tuberculostatics used as standards.

[Biological effects of substances similar to salicylanilides. 3-aryl-2H, 4H-benz(e)(1,3)oxazine-2, 4-diones and thiosalicylanilides]

The review paper is the first collected communication about the biological activity of 3-aryl-2H,4H-benz(e)(1,3)oxazine-2,4-diones and thiosalicylanilides. The substances of the above mentioned structures show a number of biological activities (antibacterial, antituberculous, antimycotic, anthelmintic, molluscocidal, neuroleptic, analgesic and anti-inflammatory) which can be modelled by structural changes. Only very few of them have been hitherto introduced into practice as anthelmintic agents, or agents with a special purpose (destroying the sea lamprey in Canadian lakes). In the group of 3-aryl-2H,3H-benz(e)(1,3)-oxazine-2,4-diones, i.e. substances developed from salicylanilides by the action of alkyl-chloroformiates, antibacterial activity is reported in refs. 3-12, antituberculous activity in refs. 13, 14, antimycotic activity in refs. 5, 6, 9, 12, 15, 16, anthelmintic activity in refs. 6,917-20, molluscocidal activity in refs. 6, 21, analgesic and anti-inflammatory activity in refs. 22-24, herbicidal activity in refs. 25, 26, allergenic activity in ref. 27. In the group of salicylanilides, antibacterial activity is reported in refs. 28-37, antimycotic activity in refs. 28-36, antiprotozoal activity in ref. 35, anthelmintic activity in refs. 28-40, 49, molluscocidal activity in refs. 7, 28-36. The present paper furthermore sums up the papers concerned with the toxicities of the above-mentioned agents. Though the peak of research of the groups of the above-mentioned structure was in the 1960s and 1970s, papers investigating their biological activity can be encountered also at present.

Antituberculotic 4'-Cyclohexylthiobenzanilides: Combination of Free-Wilson Method in QSAR with Topliss Approach

On the basis of a preliminary study of antimycobacterial activity of thiobenzanilides against Mycobacterium kansasii, a group of 4'-cyclohexylthiobenzanilids have been prepared which exhibit a significant activity against the microorganism mentioned. The whole set of 35 thiobenzanilides was tested with Mycobacterium tuberculosis, and on the basis of QSAR analysis conclusions have been made with regard to prognostics of structures suitable for further studies. The problem was solved by the method by Free and Wilson combined with the Topliss approach and by a Hansch type analysis.

New Groups of Potential Antituberculotics: 3-Aryl-2H,4H-benz[e][1,3]oxazine-2,4-diones. Comparison of the Topliss Approach with Regression Analysis

3-Phenyl-2H,4H-benz[e][1,3]oxazine-2,4-dione (I) and its derivatives II - XI, substituted on the phenyl ring, can be regarded as a new group of potential antituberculotics. Their activity increases with increasing electron-accepting properties of the substituents. introduction of bromine into the position 6 also positively influences the activity. the compounds are active in vitro against Mycobacterium tuberculosis and M. kansasii. The activity of some of them (VIII, IX0 exceeds that of commercial tuberculostatics used as standards.

Relations between Structure and Antituberculotic Activity of 4-Alkoxybenzoic Acids

Antimycobacterial activity of a series of alkoxybenzoic acids including 4-methoxybenzoic acid (II), 4-ethoxybenzoic acid (III), 4-propoxybenzoic acid (IV), 4-butoxybenzoic acid (V), 4-pentoxybenzoic acid (VI), 4-allyloxybenzoic acid (IX), 4-isopropoxybenzoic acid (VII), 4-isobutoxybenzoic acid (VIII) and 4-benzyloxybenzoic acid (X) has been determined and found to increase with the lipophilicity of the compounds expressed by the corresponding HPLC capacity factors. Also determined were the pKa values of the compounds mentioned. The most active compound, 4-pentoxybenzoic acid (VI), is comparable with commercial antituberculotics when tested in vitro.