Synthesis, benzodiazepine receptor affinity and in vivo testing of 3-aryl-4,7-dihydro-6-(N(1)'-alkylpyrazol-3 '- or 5 '-yl)pyrazolo[1,5-a]pyrimidin-7-ones

The synthesis of a series of 3-aryl-4,7-dihydro-6-(N(1')-alkylpyrazol-3 or 5'-yl)pyrazolo[1,5-a]pyrimidin-7-ones and their in vitro biological evaluation as ligands for benzodiazepine receptor (BzR) are described. The in vitro activities, as determined by an analysis of GABA (gamma-aminobutyric acid) shift ratios, and binding affinities of these compounds to BzR are compared in terms of the electronic, lipophilic and steric effect changes of their substituents either at the 3-position or at the N(1') of 6-(pyrazol-3'(5')-yl) moiety. The most interesting compounds were tested in vivo.