Synthesis of Heteroaryl ortho-Phenoxyethylamines via Suzuki Cross-Coupling: Easy Access to New Potential Scaffolds in Medicinal Chemistry

ATRP catalysts of tetradentate guanidine ligands - do guanidine donors induce a faster atom transfer?

Tripodal tetradentate N donor ligands stabilise the most active ATRP catalyst systems. Here, we set out to synthesise the new guanidine ligand TMG-4NMe2uns-penp, inspired by p-substituted tris(2-pyridylmethyl)amine (TPMA) ligands. The impact of changing pyridine against guanidine donors was examined through solid state and solution experiments and density functional theory (DFT) calculations. In the solid state, the molecular structures of copper complexes based on the ligands TMG-4NMe2uns-penp, TMG-uns-penp and TMG3tren were discussed concerning the influence of a NMe2 substituent at the pyridines and the guanidine donors. In solution, the TMG-4NMe2uns-penp system was investigated by several methods, including UV/Vis, EPR and NMR spectroscopy indicating similar properties to that of the highly active TPMANMe2 system. The redox potentials were determined and related to the catalytic activity. Besides the expected trends between these and the ligand structures, there is evidence that guanidine donors in tripodal ligand systems lead to a better deactivation and possibly a faster exchange within the ATRP equilibrium than TPMA systems. Supported by DFT calculations, it derives from an easier cleavable Cu-Br bond of the copper(II) deactivator species. The high activity was stated by a controlled initiator for continuous activator regeneration (ICAR) ATRP of styrene.

Identification of a Potent and Selective 5-HT1A Receptor Agonist with In Vitro and In Vivo Antinociceptive Activity

Opioids are the gold standard drugs for the treatment of acute and chronic severe pain, although their serious side effects constitute a big limitation. In the search for new and safer drugs, 5-HT_1AR agonists are emerging as potential candidates in pain relief therapy. In this work, we evaluated the affinity and activity of enantiomers of the two newly synthesized, potent 5-HT_1AR agonists N-[(2,2-diphenyl-1,3-dioxolan-4-yl)methyl]-2-[2-(pyridin-4-yl)phenoxy]ethan-1-ammonium hydrogenoxalate (rac-1) and N-((2,2-diphenyl-1,3-dioxolan-4-yl)methyl)-2-(2-(1-methyl-1H-imidazol-5-yl)phenoxy)ethan-1-ammonium hydrogenoxalate (rac-2) in vitro and in vivo. The role of chirality in the interaction with 5-HT_1AR was evaluated by molecular docking. The activity of the rac-1 was tested in mouse models of acute pain (hot plate) and severe tonic nociceptive stimulation (intraplantar formalin test). Rac-1 was active in the formalin test with a reduction in paw licking in both phases at 10 mg/kg, and its effect was abolished by the selective 5-HT_1AR antagonist, WAY-100635. The eutomer (S)-1, but not the racemate, was active during the hot plate test at 10 and 20 mg/kg, and this effect was abolished by 30 min treatment with WAY-100635 at 30 min. Similarly to 8-OH-DPAT, (S)-1 evoked a slow outward current and depressed spontaneous glutamatergic transmission in superficial dorsal horn neurons, more effectively than rac-1. The eutomer (S)-1 showed promising developability properties, such as high selectivity over 5-HT subtypes, no interaction with the μ receptors, and low hepato- and cardiotoxicity. Therefore, (S)-1 may represent a potential candidate for the treatment of acute and chronic pain without having the adverse effects that are commonly associated with the classic opioid drugs.

Synthesis and biological evaluation of 1,3-dioxolane-based 5-HT1A receptor agonists for CNS disorders and neuropathic pain

AIM

Targeting 5-HT_1A receptor (5-HT_1AR) as a strategy for CNS disorders and pain control.

METHODOLOGY

A series of 1,3-dioxolane-based 2-heteroaryl-phenoxyethylamines was synthesized by a convergent approach and evaluated at α₁-adrenoceptors and 5-HT_1AR by binding and functional experiments. Absorption, distribution, metabolism, excretion and toxicity prediction studies were performed to explore the drug-likeness of the compounds.

RESULTS & CONCLUSION

The most promising compound, the pyridin-4-yl derivative, emerged as a potent and selective 5-HT_1AR agonist (pKi = 9.2; pD2 = 8.83; 5-HT_1A/α1 = 135). In vitro it was able to permeate by passive diffusion MDCKII-MDR1 monolayer mimicking the blood-brain barrier and showed promising neuroprotective activity.