3,4-Disubstituted-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thiones: synthesis, antimicrobial evaluation and QSAR investigations using Hansch analysis

The 3,4-disubstituted-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thione derivatives were synthesized and characterized by physicochemical and spectral means, and the results of antimicrobial study of these compounds against Staphylococcus aureus, Escherichia coli, and Candida albicans by tube dilution method indicated that 4-(4-chlorophenyl)-3-(4-nitrophenylsulfonyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thione 6 and 4-(4-fluorophenyl)-3-(4-nitrophenylsulfonyl)-1,2,3,4,5,6,7,8-octahydroquinazoline-2-thione 12 were the most potential ones. Further, the QSAR studies by Hansch analysis applied to find out the correlation between physicochemical characteristics of synthesized compounds with antimicrobial activity demonstrated the contribution of electronic parameter, total energy (Te) and the topological parameter (valence second order molecular connectivity index (2 chi v). Excellent statistically significant models were developed by Hansch approach (r2 = 0.828-0.898) for the three microorganisms under study. The cross-validated r2 (q2), which is an indication of the predictive capability of the model for all cases was also very good (q2 = 0.776-0.875).