Karel Waisser

Quinazoline derivatives with antitubercular activity

4-Quinazolinol was prepared by the reaction of anthranilic acid and formamide. The hydroxy group was converted into the thiol function by treatment with phosphorus(V)sulfide, and the subsequent alkylation of the thiol group was carried out with alkylhalides under the conditions of phase-transfer catalysis. The structure of the substances was confirmed by 1H, 13C NMR, IR, and MS. Most of the synthesized compounds exhibited antimycobacterial activity against the strains of Mycobacterium tuberculosis, Mycobacerium avium, Mycobacterium fortuitum, Mycobacterium kansasii and Mycobacterium intracellulare. 4-(S-Butylthio)quinazoline (3c) was even more active than isoniazide against atypical strains of mycobacteria.

Heterocyclic benzazole derivatives with antimycobacterial in vitro activity.

The series of 2-benzylsulfanyl derivatives of benzoxazole and benzothiazole were synthesized, evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis and non-tuberculous mycobacteria, and the activity expressed as the minimum inhibitory concentration (MIC) in micromol/L. The substances bearing two nitro groups (4e, 4f, 5e, 5f) or a thioamide group (4i, 4j, 5i, 5j) exhibited appreciable activity particularly against non-tuberculous strains. The most active compounds were subjected to the toxicity assay and were evaluated as moderately cytotoxic.

Influence of the replacement of the oxo function with the thioxo group on the antimycobacterial activity of 3-aryl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones.

Series of 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithiones, 3-arylquinazoline-2,4(1H,3H)-diones and 3-arylquinazoline-2,4(1H,3H)-dithiones were synthesized, and the antimycobacterial activities of the derivatives evaluated in vitro. The compounds were active against Mycobacterium tuberculosis and conditionally pathogenic mycobacteria (Mycobacterium kansasii and Mycobacterium avium). The replacement of oxygen by sulfur in 3-phenyl-6,8-dichloro-2H-1,3-benzoxazine-2.4(3H)-diones and 3-arylquinazoline-2,4(1H,3H)-diones gave rise to an increase of antimycobacterial activity. The most active compound was 3-(3-chlorophenyl)-6,8-dichloro-2H-1,3-benzoxazine-2,4(3H)-dithione.

Synthesis and preliminary evaluation of benzimidazole derivatives as antimicrobial agents

A series of 2-alkylsulphanylbenzimidazoles was synthesised and the compounds were evaluated for their in vitro antimicrobial activity. The structures of the compounds were confirmed by 1H-NMR and IR data, and their purity by elemental analysis. Antimycobacterial activities against Mycobacterium tuberculosis and non-tuberculous mycobacteria as well as antifungal activities against Candida albicans, Candida tropicalis, Candida krusei, Candida glabrata, Trichosporon beigelii, Trichophyton mentagrophytes and Aspergillus fumigatus were expressed as the corresponding MIC values. The substances exhibited appreciable antimycobacterial activity, in particular, against non-tuberculous mycobacteria. The activity of the most active compound in the set, 3,5-dinitro derivative 4t, exceeded that of the standard isoniazide against M. kansasii and M. avium. The antifungal activities of the compounds were relatively low. A weak antifungal effect was observed against the dermatophyte Trichophyton mentagrophytes. None of the compounds showed significant inhibitory activity against yeasts.

New benzimidazole derivatives as antimycobacterial agents

A set of 2-alkylsulfanyl derivatives of 5-methylbenzimidazole was synthesized and evaluated for antimycobacterial activity. The structures of the compounds were confirmed by 1H NMR and IR data, and their purity by elemental analysis. Antimycobacterial activities against Mycobacterium tuberculosis and nontuberculous mycobacteria were expressed as the minimum inhibitory concentration. The substances exhibited significant antimycobacterial activity, in particular against both strains of Mycobacterium kansasii. The effect of the most active compound in the set, 3,5-dinitro derivative 3t, exceeded that of the standard isoniazide against M. kansasii and Mycobacterium avium.

New pyridine derivatives as potential antimicrobial agents.

A set of pyridine derivatives bearing a substituted alkylthio chain or a piperidyl ring in position 2 or 4 were synthesized, and their antimycobacterial and antifugal activities were evaluated. Chemical structures were confirmed by IR and NMR data, and by elemental analysis. Minimum inhibitory concentrations (MIC) were used for the evaluation of microbiological activity in vitro. The compounds were moderately active against both Mycobacterium tuberculosis and nontuberculous mycobacteria. The most active compound was 2-cyanomethylthiopyridine-4-carbonitrile (7) with MIC against Mycobacterium kansasii in the range of 8-4 mumol/l. The antifungal activities of the compounds were relatively low.

New groups of antimycobacterial agents: 6-chloro-3-phenyl-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones and 6-chloro-3-phenyl-2H-1,3-benzoxazine-2,4(3H)-dithiones.

A series of 6-chloro-3-phenyl-4-thioxo-2H-1,3-benzoxazine-2(3H)-ones 3 and a series of 6-chloro-3-phenyl-2H-1,3-benzoxazine-2, 4(3H)-dithiones 4 were synthesized by melting 6-chloro-3-phenyl-2H-1, 3-benzoxazine-2,4(3H)-dione and its derivatives substituted on the phenyl ring 2 with tetraphosphorus decasulfide. Compounds 2c-e, 3 and 4 exhibited in vitro activity against Mycobacterium tuberculosis, M. kansasii (two strains) and M. avium better than or comparable to that of isoniazid. Replacement of the oxo group by a thioxo group at position 4 led to improvement in activity against M. tuberculosis and M. kansasii. The Free-Wilson method and procedure developed by the authors were used to analyse the structure-activity and structure-antimycobacterial profile relationships, respectively.

Preparation and in vitro evaluation of benzylsulfanyl benzoxazole derivatives as potential antituberculosis agents.

A set of 2-benzylsulfanyl derivatives of benzoxazole was synthesized and evaluated for their in vitro antimycobacterial activity against Mycobacterium tuberculosis, non-tuberculous mycobacteria and multidrug-resistant M. tuberculosis. The activities were expressed as the minimum inhibitory concentration (MIC) in mmol/L. The substances showed similar activity against all tested strains. The lead compounds in the set, dinitro derivatives exhibited significant activity against both sensitive and resistant strains of M. tuberculosis and also against non-tuberculous mycobacteria. To facilitate drug design of benzoxazole as potential antituberculosis agent, we have explored the quantitative structure-activity relationship (QSAR). We demonstrated that lower lipophilicity has significant contribution to activity. Dinitrobenzylsulfanyl derivative of benzoxazole represents the promising small-molecule synthetic antimycobacterials.

SYNTHESIS OF 2-BENZYLTHIOPYRIDINE-4-CARBOTHIOAMIDE DERIVATIVES AND THEIR ANTIMYCOBACTERIAL, ANTIFUNGAL AND PHOTOSYNTHESIS-INHIBITING ACTIVITY

Abstract Aseries of 2-benzylthiopyridine-4-carbonitriles 4 and a series of 2-benzylthiopyridine-4-carbothioamides 5 were prepared. Their chemical structures were proved by IR and 1H NMR data and by elemental analysis. The MIC assessment was used for the estimation of their potential antimycobacterial and antifungal activity in vitro. The compounds were shown to be more active against mycobacterial strains than the tested fungi. Their antimycobacterial activity appears to be related mainly to the benzylthio moiety, while the antifungal activity appears to be related to the carbothioamide group. Substituents on the benzylthio moiety of derivatives 5 modified antifungal activity, whereas they did not play any significant role in antimycobacterial activity. The inhibiting effect of 4 and 5 on the photochemical activity of spinach chloroplasts was determined by IC50 values. The compounds exhibited a moderate photosynthesis-inhibiting activity.

3-Phenyl-5-methyl-2H,5H-furan-2-ones: tuning antifungal activity by varying substituents on the phenyl ring.

A series of racemic 3-phenyl-5-methyl-2H,5H-furan-2-ones related to a natural product, (-)incrustoporine, was synthesized, and their antifungal activity evaluated. The key structural feature, furanone ring, was closed via H2SO4-mediated cyclization of 2-phenylpent-4-enoic acids. The compounds displayed antifungal activity, especially against filamentous fungi. Expressed as the minimum inhibition concentration (MIC) in micromol/L, the activity of the most promising derivative against Absidia corymbifera matched that of ketoconazole (31.25 micromol/L). In terms of microg/mL, the substance was more active (7.6 microg/mL) than this standard antifungal drug (16.6 microg/mL).