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The synthesis of new 3-heteroaryl-8-chloropyrazolo[5,1-c][1,2, 4]benzotriazine 5-oxides and their binding activities at the central benzodiazepine receptor (BZR) are reported. The derivatives substituted at the 3-position with electron-rich five-membered rings, such as pyrrole 11, 2-thiophene 13c, or 3-thiophene 13d, showed good affinity values for BZR. In in vivo tests the 3-(thien-3-yl)-8-chloropyrazolo[5,1-c][1,2,4] benzotriazine 5-oxide (13d) showed selective anticonvulsant activity.

A new series of pyrazolo[5,1-c][1,2,4]benzotriazine 5-oxide 8-alkyloxy-/aryloxy-/arylalkyloxy and 8-aryl-/arylalkylderivatives variously substituted at the 3-position were synthesized and binding studies at the benzodiazepine site on GABA(A) receptor were carried out. The pharmacological profile was identified for compounds 10, 11, 16(+), 16(-), and 17 by considering six potential benzodiazepine actions: motor coordination, anticonvulsant action, spontaneous motility and explorative activity, potential anxiolytic-like effects, mouse learning and memory modulation, and finally, ethanol-potentiating action. Compound 17 stands out as the compound that improves mouse memory processes selectively, safely, and in a statistically significant manner. From a ligand-based pharmacophoric model, we identified a hydrogen bond interaction area HBp-3 near the lipophilic area. This new pharmacophoric model allowed us to identify four structural compound typologies and thus to rationalize the affinity data of all compounds.

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We report the synthesis and biological evaluation of a new series of 3- or 4-(substituted)phenylisoxazolones as HNE inhibitors. Due to tautomerism of the isoxazolone nucleus, two isomers were obtained as final compounds (2-NCO and 5-OCO) and the 2-NCO derivatives were the most potent with IC50 values in the nanomolar range (20–70 nM). Kinetic experiments indicated that 2-NCO 7d and 5-OCO 8d are both competitive HNE inhibitors. Molecular modelling on 7d and 8d suggests for the latter a more crowded region about the site of the nucleophilic attack, which could explain its lowered activity. In addition molecular dynamics (MD) simulations showed that the isomer 8d appears more prone to form H-bond interactions which, however, keep the reactive sites quite distant for the attack by Ser195. By contrast the amide 7d appears more mobile within the active pocket, since it makes single H-bond interactions affording a favourable orientation for the nucleophilic attack.

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