QSAR studies for the analgesic activity of heterocycles derivatives

Modification of the structure of a known drug is one way to develop new drugs. For this purpose, we have optimized the pyrimidobenzimidazole derivatives using molecular modeling studies. QSAR analysis has been carried out on a series of pyrimidobenzimidazole derivatives using the physicochemical parameter and molecular descriptors. The database was subjected to QSAR studies using Chemsketch software version 10.0 and all the parameter & descriptors were calculated using TSAR 3D version 3.3 for windows. The regression analysis has shown that SFI (Shape flexibility index), R (Randic index), B (Balaban index) and W (Wiener index) in combination with atom indices TA (Total atom), THA (Total hetero atom) HD (H-donar) and HA (H- acceptor) gives significant improvement in the statistics. On the basis of MLR analysis the possible position and substituent on the lead molecule have been predicted for the good analgesic activity. The output of present research work is very interesting, the result of QSAR study suggested that molecule must contain at least one substituent on R1 and R2 position should be NO2 for good analgesic activity.