Abstract

A series consisting of imidazo[1,5-a]quinoxalin-4-ones and imidazo[1,5-a]quinoxaline ureas, with a substituted phenyl ring in each class of these compounds, was reported to have high affinity for benzodiazepine receptor complex. In order to establish the exact relationship between activity and various quantifying parameters, these compounds were subjected to quantitative structure-activity relationship (QSAR) analysis. The study reveals that for in vitro radioligand displacement activities of substituted imidazo[1,5-a]quinoxalin-4-ones, a chloro group at R6, a relatively smaller group such as fluoro at R7 the less hydrophobic and more electron-donating groups, respectively, In para- and meta-positions of phenyl ring at R3 are necessary. In a related class of imidazo[1,5-a]quinoxaline ureas, the bulky group such as a pyrrolidine ring at R5, a less hydrophobic para-substituent on phenyl ring, a fluoro group at R7 and the unsubstituted R6-position are advantageous. In the piperazine urea sub-series, which was reported to possess biophasic efficacy, it emerged that a methoxy group at R3, a 3,5-dimethyl piperazine moiety at R5 and a fluoro group at R7 are essential, whereas R6 is required to be unsubstituted.