Design, synthesis, crystal structure, biological evaluation and molecular docking studies of carbazole-arylpiperazine derivatives.

Subtype-selective α1-adrenoceptor (AR) antagonists display optimum therapeutic efficacies for the treatment of benign prostatic hyperplasia (BPH). In this study, we designed and synthesized novel carbazole-arylpiperazines derivatives (1 and 2) on the basis of the proposed pharmacophore model for α1-AR antagonists. Structural properties were investigated using single-crystal X-ray diffraction analysis. Comparison of crystal structures with ligand-based pharmacophore models revealed that the two agents may possess antagonistic effects on α1D subtype. Tissue functional assay in vitro showed that compound 2 exerted strong antagonistic activity on α1B-AR (pA2 7.13) with a poor selectivity for α1A and α1D subtypes. Compound 1 exhibited enhanced antagonistic effect on α1D subtype (pA2 7.06) and excellent selectivity for α1D over α1B (α1D/α1B ratio=79.4). To illustrate the relationship between antagonistic activity and chemical structure, molecular docking studies were performed using the homology models of α1 receptors. Binding mechanism indicated that small hydrophobic substituents attached to the arylpiperazine moiety were essential for rational design of α1D-selective antagonists.

Synthesis, structure-activity relationship and biological evaluation of novel arylpiperzines as α1A/1D-AR subselective antagonists for BPH.

A series of novel arylpiperazine derivatives as α1A/1D-adrenergic receptors (AR) subtype selective antagonists were designed, synthesized and evaluated for their antagonistic activities towards α1-ARs (α1A, α1B, and α1D). Compounds 9, 12, 13, 15, 17, 18, 21, 22, 25 and 26 exerted strong antagonistic effects on α1A and/or α1D subtypes over α1B in vitro. SAR analysis indicated that chloride at the ortho-phenyl position for compound 17 was beneficial for the highest α1A/D-AR sub-selectivity. Moreover, molecular docking study of compound 17 with the homology-modeled α1-ARs (α1A, α1B, and α1D) structures exhibited differences of key amino resides in the docking pocket which may influence the subtype selectivity. ILE 193 of α1A was validated as the key residues for binding ligand. This work provides useful information for finding more new potential drugs in clinic in treating benign prostatic hyperplasia (BPH).

X-ray Crystallography, DFT Calculations and Molecular Docking of Indole-Arylpiperazine Derivatives as α1A-Adrenoceptor Antagonists.

Indole-arylpiperazine derivatives have exhibited good selectivity for the α1A-adrenoceptor, but the structure-activity-binding mechanism relationship remains unclear. In the current study, three compounds (1, 2 and 3) were investigated through single-crystal X-ray diffraction analysis, density functional theory (DFT) calculations and molecular docking using a homology model of the α1A receptor. Compounds 1 and 3 form H-bonds networks to stabilize their three-dimensional structures, while C-H···π interactions play a significant role in the packing of 2. Based on DFT-optimized conformations, the HOMO-LUMO energy gaps and molecular electrostatic potential (MEP) were theoretically calculated at the B3LYP/6-311G (d, p) level of theory. Chemical reactivity increases in the order of 3 < 2 < 1, and the maximum positive region of the MEP maps is mainly localized over the NH group. The binding mechanisms of ligand-α1A-adrenoceptor complexes were illustrated by molecular docking. Binding to Gln177 of the second extracellular loop region via hydrogen bonds is likely to be essential for α1A-selective antagonists. The present work sheds light on the studies of structure-activity-binding mechanism and aids in the design of α1A antagonists with high selectivity.