Synthesis and Structure−Activity Relationship of Fluoro Analogues of 8-{2-[4-(4-Methoxyphenyl)piperazin-1yl]ethyl}-8-azaspiro[4.5]decane-7,9-dione as Selective α1d-Adrenergic Receptor Antagonists

Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a phenoxyethylamine group as highly potent and selective α1D adrenoceptor antagonists

A series of phenoxyethylamine derivatives was designed and synthesized to discover potent and selective human α_1D adrenoceptor (α_1D adrenergic receptor; α_1D-AR) antagonists. Compound 7 was taken from our internal compound collection as an attractive starting point and exhibited moderate binding affinity for α_1D-AR and high selectivity against α_1A- and α_1B-ARs. We focused on modifying the 2-methylsulfonylbenzyl group of 7 to discover novel compounds structurally distinct from other reported α₁-AR antagonists containing the phenoxyethylamine motif. Study of structure activity relationship guided by a targeted ligand-lipophilicity efficiency score led to the discovery of a novel scaffold of 3,4-dihydro-2H-thiochromene 1,1-dioxide for selective α_1D-AR antagonists. Further optimization studies resulted in the identification of (4S)-N⁴-[2-(2,5-difluorophenoxy)ethyl]-N⁶-methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)-41, as a novel, highly potent and selective α_1D-AR antagonist. Herein, we provide details of the structure activity relationship of the phenoxyethylamine analog for the potency and selectivity.

Synthesis and cytotoxic activity evaluation of novel arylpiperazine derivatives on human prostate cancer cell lines

A series of novel arylpiperazine derivatives was synthesized. The in vitro cytotoxic activities of all synthesized compounds against three human prostate cancer cell lines (PC-3, LNCaP, and DU145) were evaluated by a CCK-8 assay. Compounds 9 and 15 exhibited strong cytotoxic activities against LNCaP cells (IC₅₀ < 5 μM), and compound 8 (IC₅₀ = 8.25 μM) possessed the most potent activity against DU145 cells. However, these compounds also exhibited cytotoxicity towards human epithelial prostate normal cells RWPE-1. The structure–activity relationship (SAR) of these arylpiperazine derivatives was also discussed based on the obtained experimental data.

6-methoxy-7-benzofuranoxy and 6-methoxy-7-indolyloxy analogues of 2-[2-(2,6-Dimethoxyphenoxy)ethyl]aminomethyl-1,4-benzodioxane (WB4101):1 discovery of a potent and selective α1D-adrenoceptor antagonist

Previous results have shown that replacement of one of the two o-methoxy groups at the phenoxy residue of the potent, but not subtype-selective, α1-AR antagonist (S)-WB4101 [(S)-1] by phenyl, or by ortho,meta-fused cyclohexane, or especially by ortho,meta-fused benzene preferentially elicits α1D-AR antagonist affinity. Such observations inspired the design of four new analogues of 1 bearing, in lieu of the 2,6-dimethoxyphenoxy residue, a 6-methoxy-substituted 7-benzofuranoxy or 7-indolyloxy group or, alternatively, their corresponding 2,3-dihydro form. Of these new compounds, which maintain, rigidified, the characteristic ortho heterodisubstituted phenoxy substructure of 1, the S enantiomer of the dihydrobenzofuranoxy derivative exhibited the highest α1D-AR antagonist affinity (pA2 9.58) with significant α1D/α1A and α1D/α1B selectivity. In addition, compared both to α1D-AR antagonists structurally related to 1 and to the well-known α1D-AR antagonist BMY7378, this derivative had modest 5-HT1A affinity and neutral α1-AR antagonist behavior.

New pyrimido[5,4-b]indoles and [1]benzothieno[3,2-d]pyrimidines: High affinity ligands for the α1-adrenoceptor subtypes

A number of new pyrimido[5,4-b]indole and [1]benzothieno[3,2-d]pyrimidine derivatives were synthesized and evaluated for their binding and functional properties at alpha(1)-adrenergic receptor (alpha(1)-AR) subtypes. They behaved as potent alpha(1)-AR antagonists. In binding experiments, some of them (RC24 and RC23) showed very high affinity for the alpha(1D)-AR subtype.