Antituberculosis activity of several 5-(4-aminophenyl)-4-alkyl/aryl-2,4-dihydro-3H-1,2,4-triazole-3-thiones (1-9) and their thiourea derivatives (10-31) were screened for their antimycobacterial activities against Mycobacterium tuberculosis H37Rv using the BACTEC 460 radiometric system. Of the synthesized compounds, 10-12, 30 were the most active derivatives exhibiting more than 90 % inhibition of mycobacterial growth at 12.5 microg/mL. Structure-activity relationships study was performed for the given series by using the Electronic-Topological Method combined with Neural Networks (ETM-NN). A system of prognosis was developed as the result of training associative neural network (ASNN) using weights of pharmacophoric fragments as descriptors. Descriptors were calculated by the projection of ETM compound and pharmacophoric fragments on the elements of Kohonen's self-organizing maps (SOM). From the detailed analysis of all compounds under study, the necessary requirements for a compound to possess antituberculosis activity were formulated. The analysis have shown that any requirements violation for a molecule implies a considerable decrease or even complete loss of its activity.

Diazonium salts derived from amines 1 (sulfanilic acid, 4-nitroaniline, 4-aminosalicylic acid, sulfanilamide, sulfamethoxazole, sulfathiazole, sulfapyridine, sulfamerazine) were coupled with N-(2,4-dimethylphenyl)-3-oxobutanamide (2) resulting in the formation of hydrazones 3a-h.

2-Propylamino-5-[4-(2-hydroxy-3,5-dichlorobenzylideneamino) phenyl]-1,3,4-thiadiazole, formulated as C 18 H 16 Cl 2 N 4 OS (I), was synthesized. The crystal and molecular structure of (I) have been determined by 1 H-NMR, IR, and X-ray single crystal diffraction. The compound (I) crystallizes in the monoclinic, space group P2(1)/c with unit cell parameters a = 9.0576(2) Å , b = 24.3382(8) Å , c = 9.0585(2) Å , M r = 407.31, V = 1851.13(9) Å 3 , Z = 4, R 1 = 0.036, and wR 2 = 0.096. Molecular geometry from X-ray experiment of (I) in the ground state has been compared using the density functional method (B3LYP) with 6-31G(d) basis set. To determine conformational flexibility, molecular energy profile of (I) was obtained by semi-empirical (PM3) calculations with respect to selected degree of torsional freedom, which was varied from -180°to ?180°in steps of 10°. The results are indicative that the Schiff base, which contains a thiadiazole ring, prefers to be in E-configuration. In addition, molecular electrostatic potential, frontier molecular orbitals, and natural bond orbitals analysis were performed by the B3LYP/ 6-31G(d) method.

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