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A quantitative structure-activity relationship (QSAR) study is suggested for the prediction of anti-HIV activity of tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepinone (TIBO) derivatives. The model was produced by using the support vector machine (SVM) technique to develop quantitative relationships between the anti-HIV activity and ten molecular descriptors of 89 TIBO derivatives. The performance and predictive capability of the SVM method were investigated and compared with other techniques such as artificial neural networks and multiple linear regression. The results obtained indicate that the SVM model with the kernel radial basis function can be successfully used to predict the anti-HIV activity of TIBO derivatives with only ten molecular descriptors that can be calculated directly from only molecular structure. The contribution of each descriptor to the structure-activity relationships was evaluated. Hydrophobicity of the molecule was thus found to take the most relevant part in the molecular description.

Human Immunodeficiency Virus type 1 reverse transcriptase is an important target for chemotherapeutic agents against the AIDS disease. 1-[2-Hydroxyethoxy-methyl]-6-(phenylthio) thymine] derivatives are potent nonnucleoside reverse transcriptase inhibitors. In the present work, quantitative structure-activity relationship analysis for a set of 79 HEPT derivatives has been investigated by means of support vector machines. The relationships between structure and activity were examined quantitatively using descriptors encoding the steric, hydrophobic, electronic and structural features of 1-[2-hydroxyethoxy-methyl]-6-(phenylthio) thymine] derivatives. The performance and predictive capability of support vector machines method are investigated and compared with other methods such as artificial neural network and multiple linear regression methods. The obtained results indicate that the support vector machines model with the kernel radial basis function can be employed as a forceful tool for quantitative structureactivity relationship studies. The contribution of each descriptor to the structure-activity relationships was evaluated.

The tautomeric equilibrium of benzimidazolone and benzimidazolthione have been studied by the density functional theory method using the CAM-B3LYP functional together with the 6-311G(d,p) basis set. Two separate mechanisms have been investigated: a direct intramolecular transfer using the polarizable continuum model and an indirect proton transfer assisted by a molecule of solvent (C6H12, H2O, CH3OH, and H2O2). In both cases, the results obtained indicate that ketone and thione are the most stable forms. However, the enhanced height of the activation barrier for the four-center mechanisms describing the tautomerism reaction as a direct intramolecular transfer implicates a relatively disadvantaged process. The participation of a polar protic solvent molecule allows the lowering of the activation energy barrier. Potential energy profiles of keto-enol and thio-enol tautomerism assisted by methanol and water are very different. The former one describes a concerted mechanism but the latter does not because it is associated with asynchronous processes that take place during the thio-enol tautomerism.

In this work, we study simples phosphazenes models, such as R-[R 2 P=N] n -X, with (X = H, F, OH), (R= H, F) and (n = 1, 2 and 3) with an attempt to answer the type of Natural Hybrid Orbital (NHO) able to form this -bond in the phosphazene-Na + complex and the Na + effect on the geometry and the electronic distribution of the studied molecules by using the HF and DFT studies of electronics, molecular structures and Natural Bond Orbital (NBO) analysis. The substituent effect of the fluorine atom acceptor and the OH group donor is studied. The phosphazene polymers doped by Na + cation, linearize all the PNP bond angles.The geometries of all the systems were optimized using Berny algorithm [33] within higher accuracy (keyword opt=