Crystal structure and quantum electronic analyses of pitrazepin, a γ-aminobutyric acid (GABA) receptor antagonist

The crystal structure of pitrazepin has been solved by direct methods from single-crystal X-ray diffraction data and refined by full-matrix least squares: monoclinic, space group P21/c, a= 18.845(2), b= 15.424(5), c= 16.950(4)Å, β= 104.51(2)°, Z= 4, two pitrazepin and three water molecules per asymmetric unit, final R factor is 0.042. This compound binds with high affinity to pharmacological GABA-A receptors; it acts as an antagonist. Ab initio molecular orbital calculations for pitrazepin and GABA show that the piperazine and triazole rings of pitrazepin might be considered as the GABA-mimetic moieties.