1-Phenoxyalkyl-4-[(N,N-disubstitutedamino)alkyl]piperazine derivatives as non-imidazole histamine H3-antagonists

4-Oxypiperidine Ethers as Multiple Targeting Ligands at Histamine H3 Receptors and Cholinesterases

This study examines the properties of a novel series of 4-oxypiperidines designed and synthesized as histamine H3R antagonists/inverse agonists based on the structural modification of two lead compounds, viz., ADS003 and ADS009. The products are intended to maintain a high affinity for H3R while simultaneously inhibiting AChE or/and BuChE enzymes. Selected compounds were subjected to hH3R radioligand displacement and gpH3R functional assays. Some of the compounds showed nanomolar affinity. The most promising compound in the naphthalene series was ADS031, which contained a benzyl moiety at position 1 of the piperidine ring and displayed 12.5 nM affinity at the hH3R and the highest inhibitory activity against AChE (IC50 = 1.537 μM). Eight compounds showed over 60% eqBuChE inhibition and hence were qualified for the determination of the IC50 value at eqBuChE; their values ranged from 0.559 to 2.655 μM. Therapy based on a multitarget-directed ligand combining H3R antagonism with additional AChE/BuChE inhibitory properties might improve cognitive functions in multifactorial Alzheimer's disease.

4-Hydroxypiperidines and Their Flexible 3-(Amino)propyloxy Analogues as Non-Imidazole Histamine H₃ Receptor Antagonist: Further Structure⁻Activity Relationship Exploration and In Vitro and In Vivo Pharmacological Evaluation

Presynaptic histamine H₃ receptors (H₃R) act as auto- or heteroreceptors controlling, respectively, the release of histamine and of other neurotransmitters in the central nervous system (CNS). The extracellular levels of several neurotransmitters are enhanced by H₃R antagonists, and there is a great interest for potent, brain-penetrating H₃ receptor antagonists/inverse agonists to compensate for the neurotransmitter deficits present in various neurological disorders. We have shown that 1-[(benzylfuran-2-yl)methyl]piperidinyl-4-oxyl- and benzyl- derivatives of N-propylpentan-1-amines exhibit high in vitro potencies toward the guinea pig H₃ receptor (jejunum), with pA₂ = 8.47 and 7.79, respectively (the reference compound used was thioperamide with pA₂ = 8.67). Furthermore, following the replacement of 4-hydroxypiperidine with a 3-(methylamino)propyloxy chain, the pA₂ value for the first group decreased, whereas it increased for the second group. Here, we present data on the impact of elongating the aliphatic chain between the nitrogen of 4-hydroxypiperidine or 3-(methylamino)propan-1-ol and the lipophilic residue. Additionally, the most active compound in this series of non-imidazole H₃ receptor antagonists/inverse agonists, i.e., ADS-003, was evaluated for its affinity to the recombinant rat and human histamine H₃ receptors transiently expressed in HEK-293T cells. It was shown that ADS-003, given parenterally for 5 days, reduced the food intake of rats, as well as changed histamine and noradrenaline concentrations in the rats’ brain in a manner and degree similar to the reference H₃ antagonist Ciproxifan.

On-Water Reactivity and Regioselectivity of Quinones in C–N Coupling with Amines: Experimental and Theoretical Study

A study about the oxidative coupling of some representative carbo- and heterocyclic non-symmetrical quinones with aryl- and alkylamines, was carried out comparing dichloromethane and water as reaction mediums. We found that the on-water reactions gave better or, at worst, the same results as a conventional organic medium like dichloromethane. Descriptors derived from conceptual density functional theory and approaches of electrostatic nature, such as the molecular electrostatic potential, were used to explain the observed chemical reactivity and regioselectivity. Further, the on-water conditions were used to obtain 24 new aminoquinones with potential biological activity.