A new series of heteroaromatic receptors containing the 1,3-bis(6-oxopyridazin-1-yl)propane unit: their selective transport ability towards NH4 in relation to Na, K and Ca

The synthesis of a new series of heteroaromatic macrocycles 6-9 containing the 1,3-bis(6-oxopyridazin-1-yl)propane and pyridine units is reported. The acyclic compounds 11-15 had to be prepared as the intermediates in the synthetic sequence. Evaluation of the ionophoric properties of 6-9 and 11-15 shows that 8 and 13 behave as good ammonium ion carriers and exhibit a high selectivity for ammonium with respect to spherically symmetric metallic ions like Na⁺, K⁺, and Ca²⁺. Molecular modelling of the ammonium complexes suggests that the host's oxyimino groups play a more relevant part in effective complexation than the pyridine unit, and that the high complexating efficiency of 13 might be related to the formation of a pseudocavity by intramolecular hydrogen bonding.     

Large pKa shifts of alpha-carbon acids induced by copper(II) complexes

A series of synthetic receptors (4-6) incorporating metal ions, specifically copper(II), were examined for their ability to enhance the acidity of active methylene compounds. The copper(II) complexes were observed to reduce the pKa of 1,3-diketone carbon acids in acetonitrile by as much as 12 pKa units. The relatively large pKa reduction achieved by the complex is attributed to the electrostatic interaction between the anionic pi system of the enolate and the copper(II) ions. The cage structure and hydrogen bonding sites in receptors 4 and 5 lead to a very modest further enhancement of the acidity relative to that with 6. This study provides insight into the way in which metalloenzymes stabilize an enolate intermediate.     

Molecular dynamics simulation of the ligand binding domain of mGluR1 in response to agonist and antagonist binding

The interdomain movements of the ligand binding domain (LBD) of mGluR1 in response to agonist or antagonist binding are studied by 2 ns molecular dynamics (MD) simulations. Our results indicate that MD is able to reproduce many of the experimentally determined features of the open and closed conformations of LBD. Analysis of the ligand behavior over time allows to delineate some of the molecular determinants responsible for the agonist-induced or antagonist-blocked LBD responses.     

Synthesis and Pharmacological Evaluation of Chlorinated <Emphasis Type="Italic">N</Emphasis>-Alkyl-3- and -5-(2-hydroxyphenyl)pyrazoles as <Emphasis Type="Italic">CB</Emphasis><Subscript>1</Subscript> Cannabinoid Ligands

Summary. The syntheses of several new 3- and 5-(4-chloro-2-hydroxyphenyl)-5- and -3-(2,4-dichlorophenyl)-1-alkylpyrazoles are reported. These syntheses started from simple chlorophenols, 2,4-dichlorobenzaldehyde or ethyl 2,4-dichlorobenzoate in order to prepare pyrazoles bearing three and four chloro substituents in certain positions. The affinity of these compounds towards the CB ₁ type cannabinoids receptors was then evaluated in human brain tissues (frontal cortex). The results showed that some of the compounds exhibit affinity towards this kind of receptors in the micromolar range.     

Synthesis,anticancer activity and docking studies of pyrazoline and pyrimidine derivatives as potential epidermal growth factor receptor (EGFR) inhibitors

A search for anticancer agents has prompted the design and synthesis of new chalcone, pyrazoline and pyrimidine derivatives as potential epidermal growth factor receptor (EGFR) kinase inhibitors. These derivatives’ binding affinities were predicted by AutoDock, which showed that chalcone, pyrazoline and pyrimidine derivatives as EGFR-kinase inhibitors have good binding energies, ranging from ?10.91 to ?7.32 kcal/mol. These compounds were synthesized and characterized using elemental analysis (CHN analysis) and spectroscopic techniques (FTIR and NMR). Among the pyrazoline derivatives, 4Aiii has revealed a superior in vitro activity, inhibiting the EGFR kinase even at a low concentration of 0.19 μM compared to the pyrimidine derivative, 5Bii. In contrast, the cytotoxic effect of these derivatives was studied against hormonal and non-hormonal breast cancer cell lines. Most of the pyrazoline derivatives were able to express their cytotoxic effect efficiently against hormonal breast cancer but only one pyrimidine derivative managed to express its activity against hormonal breast cancer.     

Differentiation of δ, μ, and κ opioid receptor agonists based on pharmacophore development and computed physicochemical properties

Compounds that bind with significant affinity to the opioid receptor types, , , and , with different combinations of activation and inhibition at these three receptors could be promising behaviorally selective agents. Working on this hypothesis, the chemical moieties common to three different sets of opioid receptor agonists with significant affinity for each of the three receptor types , , or were identified. Using a distance analysis approach, common geometric arrangements of these chemical moieties were found for selected , , or opioid agonists. The chemical and geometric commonalities among agonists at each opioid receptor type were then compared with a non-specific opioid recognition pharmacophore recently developed. The comparison provided identification of the additional requirements for activation of , , and opioid receptors. The distance analysis approach was able to clearly discriminate -agonists, while global molecular properties for all compounds were calculated to identify additional requirements for activation of and receptors. Comparisons of the combined geometric and physicochemical properties calculated for each of the three sets of agonists allowed the determination of unique requirements for activation of each of the three opioid receptors. These results can be used to improve the activation selectivity of known opioid agonists and as a guide for the identification of novel selective opioid ligands with potential therapeutic usefulness.     

Synthesis of acyclic nucleotide analogues possessing a difluoromethylene phosphonyl group at the side chain

A synthetic approach to a new type of acyclic nucleotide analogues 8 and 9 was examined. The design was based on acyclic modification of MRS 2179, a P2Y₁-antagonist, and replacement of one of two phosphate groups characterized by MRS 2179 with an isosteric difluoromethylenephosphonyl group. The nucleotide analogues 8 and 9 were enantio-divergently prepared as their ester-protecting derivatives from a highly differentiated 1,5-pentanediol derivative possessing a difluoromethylenephosphonyl group at the 3-position.     

Modelling of adrenoceptor ligand targets based on novel medium- or macro-sized fused nitrogen heterocyclic systems

Novel medium- and macro-sized heterocyclic compounds were assessed for their potential as subtype-selective adrenergic ligands. Their conformational flexibilities were investigated and their geometric shapes were compared to rigid lead compounds of known selectivity. In the case of 1A selective antagonists, interesting potential targets for synthesis and evaluation were identified by 'opening up' various rings of the fused-ring lead compound 1 by shared-bond cleavage. For 2 selective ligands, compound 6 was the lead compound and the possibility of mimicking the fused-ring system via intramolecular hydrogen bonding was investigated. None of the potential targets were closely enough related in this case to the lead compound to warrant synthesis.     

Thermodynamics of Hydrophobic Interactions: Entropic Recognition of a Hydrophobic Moiety by Poly(Ethylene Oxide)–Zinc Porphyrin Conjugates

The recognition of 4‐alkylpyridines by water‐soluble poly(ethylene oxide)–zinc porphyrin conjugates was studied with a focus on the thermodynamic parameters of binding. Microcalorimetric studies indicated that binding of the alkyl group of the guest in water is driven by the entropic term (δΔH⁰=ΔH⁰(4‐pentylpyridine)? ΔH⁰(4‐methylpyridine)=+1.7 kJ mol^?1, δTΔS⁰=TΔS⁰(4‐pentylpyridine)? TΔS⁰(4‐methylpyridine)=+11.8 kJ mol^?1 at 298 K), thus showing the significance of water reorganization during host–guest interaction. The enthalpy–entropy compensation temperature of binding of 4‐alkylpyridines was as low as 38 K; only below this temperature could the enthalpic term be a driving force. The binding affinity was modulated by the addition of cations and by varying the degree of polymerization of poly(ethylene oxide), which suggests that guest binding is coupled with polymer conformation.     

Soft functional polynuclear coordination compounds containing pyrimidine bridges

In this account, we describe the use of simple pyrimidine derivatives in combination with metal ions to build highly structured molecular architectures containing functional nanoenvironments, cavities and surfaces that can interact with additional species. The supramolecular structure of these systems can be rationally controlled by metal fragment geometry, reaction conditions and presence of templating agents. Thus, the use of transition metals with low coordination numbers or blocked bonding positions in combination with pyrimidines (e.g. 2-hydroxypyrimidine, 4-hydroxypyrimidine, 2,4-dihydroxypyrimidine, 2-aminopyrimidine) leads to the formation of either discrete assemblies, 1D polymers or helixes. When metal ions with higher coordination possibilities are applied instead, 2D and 3D networks are generated. Some of the assemblies built in this way possess functional cavities, pores and surfaces that can interact with additional species by means of hydrophobic, electrostatic, H-bonding interactions and coordinative bonds to give rise to recognition processes. The latter range from molecular recognition in homogeneous phase as well as clathrate formation, to heterogeneous solid-gas and solid-liquid adsorption phenomena. It should be noted that these materials are not rigid but able to undergo guest-induced reorganisation processes even in the solid state. Finally, some of these materials also combine additional interesting magneto-optical properties. Thus, dual systems can be envisaged in which two or more of these properties are present in the same material.