Computational modeling studies on anti-HIV-1 non-nucleoside reverse transcriptase inhibition by dihydroalkoxybenzyloxopyrimidines analogues: an electrotopological atomistic approach

For the first time we report quantitative structure activity relationship (QSAR) studies based on Kier-Hall Electrotopological State (E-State) Indices for Dihydroalkoxybenzyloxopyrimidines (DABO) derivatives acting as NNRTIs of HIV-1. A dataset of 74 compounds was compiled from published studies and randomly subdivided into training and test sets. To understand the pharmacophoric effect, Kier-Hall Electrotopological State descriptors namely SN1, SN3, SF, SAr, SS, SO, SNO2, SCl, SY (Y = S-alkyl and NH-alkyl), SX (X = Me) and biological activity were used as independent and dependent variable respectively. Statistical results were highly encouraging for the training set multiple linear regression [(MLR): r2 = 0.961, F = 100.41 and q2 = 0.926, neural networks (NN): r2 = 0.966, F = 115.594, degrees of freedom = 40 and k-nearest neighbour (k-NN): r2 = 0.770, q2 = 0.757, degrees of freedom = 40]. Results of validation using a test set showed the same trend as training set (NN > MLR > kNN). The above results suggest that of various functional groups present in DABO such as SN3, SO, SCl, SAr and SNO2 contribute more significantly towards activity. On the other hand SN1, SS, and SF do not play any role in enhancing the activity. The substitution of S-alkyl and NH-alkyl at C2 position is essential though it does not contribute much towards the activity. The substitution of methyl group at C5 position is unfavorable and exhibit negative impact on inhibitory activity. Therefore, it seems reasonable to choose E-state indices as suitable and significant descriptors for exploring the relationship between the pIC50 and the pharmacological properties of the compounds.