Separation of substituted phenylpiperazine derivatives with immobilized polysaccharide-based chiral stationary phases by supercritical and subcritical fluid chromatography

Six newly synthesized racemic 1-（substituted phenyl）-4-[3-（indole-4-yl-oxy）-2-hydroxypropyl]-piperazine 1-6 were successfully resolved by carbon dioxide supercritical fluid chromatography （SFC） on an analytical scale column packed with immobilized polysaccharide-based chiral stationary phases （CSPs）. We found that separation on the Chiralpak IA CSP was superior to the other two immobilized CSPs （Chiralpak IB and Chiralpak IC）, and isopropanol （IPA） was a superior modifier compared to the other five solvents including ethanol, methanol, tetrahydrofuran, acetonitrile and dichloromethane. The effects of organic modifier composition, back pressure, and column temperature for enantioseparation of all six compounds were studied. Of the physical parameters studied, modifier composition had the greatest impact on retention. Changing temperature generally had less impact on retention but produced the greatest selectivity changes. The optimum condition was found as follows： Chiralpak IA column, column temperature 35 ~C, back pressure 120 bar, 35% IPA containing 0.1% diethylamine （v/v） in mobile phase, flow rate of mobile phase 3.0 mL/min, UV detection 283 nm. Separation of all six racemic compounds was completed within 10 rain and excellent resolution was obtained. Thus, SFC was found to be the methodology of choice for resolving the enantiomers of this class of compounds.

Discovery of an enantiopure N-[2-hydroxy-3-phenyl piperazine propyl]-aromatic carboxamide derivative as highly selectiveα_(1D/1A)-adrenoceptor antagonist and homology modelling

α_(1)-Adrenergic receptor(AR)blockers can be effective for the treatment of benign prostatic hyperplasia/lower urinary tract symptoms(BPH/LUTS),their usage is limited by cardiovascular-related side effects that are caused by the subtype nonselective nature or low selectivity of many current drugs.We previously reported that phenylpiperazine analogues with amide and propane linker were moderateα_(1D/1A)adrenoceptor antagonists and exhibited better anti-BPH effect than lead compound naftopidil(NAF)in vivo,however,with modestα_(1D/1A)-subtype selectivity.Herein,we replaced propane moiety with2-hydroxypropanol linker and synthesized twenty-seven racemic derivatives with modified aromatic and hetero aromatic groups.Of these new compounds,quinoline surrogate 17 exhibited extremely weak antagonistic affinity onα_(1B)in both cell-based calcium assay and tissue-based functional assay,so that elicited significantα_(1A/1B)andα_(1D/1B)selectivity.Intriguingly,the R enantiomer of 17 preferentially displayed superior anti-BPH effect in rat model compared with S-17,supporting ligand regulates the receptor in a highly stereospecific manner.Finally,the computer-aided modelling research was also performed in order to deeply understand the unique binding mode of R-17 in complex withα_(1A)and the subtype receptor selectivity for R-17 was also rationalized in this study.Taken together,our work enriched the diversity of phenylpiperazines for the treatment of BPH/LUTS,and provided a basis for discovery ofα_(1D/1A)-selective ligands.