6-Sulfonylchromenes as highly potent K(ATP)-channel openers

Detection and Identification of Nitrile Compounds via Recognition-Enabled Chromatographic 19F NMR

The surge in applications of nitrile compounds across diverse fields, such as pharmaceuticals, agrochemicals, dyes, and functional materials, necessitates the development of rapid and efficient detection and identification methods. In this study, we introduce a chemosensing strategy employing a novel 19F-labeled probe, facilitating swift and accurate analysis of a broad spectrum of nitrile-containing analytes. This approach leverages the reversible interaction between the 19F-labeled probe and the analytes to produce chromatogram-like outputs, ensuring the precise identification of various pharmaceuticals and pesticides within complex matrices. Additionally, this dynamic system offers a versatile platform to investigate through-space 19F-19F interactions, showcasing its potential for future applications in mechanistic studies.

Activated Inositol Phosphate, Substrate for Synthesis of Prostaglandylinositol Cyclic Phosphate (Cyclic PIP)-The Key for the Effectiveness of Inositol-Feeding

The natural cyclic AMP antagonist, prostaglandylinositol cyclic phosphate (cyclic PIP), is biosynthesized from prostaglandin E (PGE) and activated inositol phosphate (n-Ins-P), which is synthesized by a particulate rat-liver-enzyme from GTP and a precursor named inositol phosphate (pr-Ins-P), whose 5-ring phosphodiester structure is essential for n-Ins-P synthesis. Aortic myocytes, preincubated with [3H] myo-inositol, synthesize after angiotensin II stimulation (30 s) [3H] pr-Ins-P (65% yield), which is converted to [3H] n-Ins-P and [3H] cyclic PIP. Acid-treated (1 min) [3H] pr-Ins-P co-elutes with inositol (1,4)-bisphosphate in high performance ion chromatography, indicating that pr-Ins-P is inositol (1:2-cyclic,4)-bisphosphate. Incubation of [3H]-GTP with unlabeled pr-Ins-P gave [3H]-guanosine-labeled n-Ins-P. Cyclic PIP synthase binds the inositol (1:2-cyclic)-phosphate part of n-Ins-P to PGE and releases the [3H]-labeled guanosine as [3H]-GDP. Thus, n-Ins-P is most likely guanosine diphospho-4-inositol (1:2-cyclic)-phosphate. Inositol feeding helps patients with metabolic conditions related to insulin resistance, but explanations for this finding are missing. Cyclic PIP appears to be the key for explaining the curative effect of inositol supplementation: (1) inositol is a molecular constituent of cyclic PIP; (2) cyclic PIP triggers many of insulin's actions intracellularly; and (3) the synthesis of cyclic PIP is decreased in diabetes as shown in rodents.

Nitrile-containing pharmaceuticals: target, mechanism of action, and their SAR studies

The nitrile group is an important functional group widely found in both pharmaceutical agents and natural products. More than 30 nitrile-containing pharmaceuticals have been approved by the FDA for the management of a broad range of clinical conditions in the last few decades. Incorporation of a nitrile group into lead compounds has gradually become a promising strategy in rational drug design as it can bring additional benefits including enhanced binding affinity to the target, improved pharmacokinetic profile of parent drugs, and reduced drug resistance. This paper reviews the existing drugs with a nitrile moiety that have been approved or in clinical trials, involving their targets, molecular mechanism of pharmacology and SAR studies, and classifies them into different categories based on their clinical usages.

The expression of ATP-sensitive potassium channels in human umbilical arteries with severe pre-eclampsia

The aim of this study is to establish the expression of ATP-sensitive potassium channels(KATP) in human umbilical arteries with severe pre-eclampsia. Real-time quantitative PCR and western blotting were used to detect the mRNA and protein expression levels of KATP channel subunits Kir6.1 and SUR2B in human umbilical arteries from normal pregnant and those with severe pre-eclampsia, early onset severe pre-eclampsia and late onset severe pre-eclampsia. The mRNA and protein levels of SUR2B in the severe pre-eclampsia group were lower than those in the normal group (P < 0.001), and the expression of Kir6.1 was not statistically significant between the two groups (P > 0.05). The mRNA and protein levels of SUR2B in early onset severe pre-eclampsia group were lower than those in late onset severe pre-eclampsia group (P < 0.001). There was no significant difference in expression of Kir6.1 between the two groups (P > 0.05). The mRNA and protein expression levels of SUR2B in pregnant women with severe pre-eclampsia were lower than those in normal pregnant women, suggesting that the expression of the SUR2B of the KATP channel may be related to the occurrence and development of severe pre-eclampsia. Compared with late onset severe pre-eclampsia, the mRNA and protein expression levels of SUR2B were lower in the umbilical arteries of women with early onset severe pre-eclampsia, suggesting that the occurrence time of severe pre-eclampsia may be related to the extent reduced expression of the SUR2B of the KATP channel.

Gas phase reaction between chromones and solvent in an electrospray ionization source

Chromones were measured by using electrospray ionization mass spectrometry in negative mode. Interestingly, in addition to the deprotonated ion ([M - H]^- ), unexpected [M + 17]^- and [M + 31]^- ions were observed in high intensity when water and methanol were used as the solvent. Chromones with different substitutes were tested. Compared with the deprotonated ion, [M + 17]^- and [M + 31]^- ions were observed with higher abundances when the C-3 site of chromones was substituted by electron withdrawing groups. Based on high performance liquid chromatography-mass spectrometry (LC-MS), deuterium-labeling and collisional-induced dissociation experiments, a covalent gas-phase nucleophilic addition reaction between chromone and water, and the formation of a noncovalent complex between chromone and methanol were proposed as the mechanism for the observed [M + 17]^- and [M + 31]^- ions, respectively. Understanding and using these unique gas phase reactions can avoid misannotation when analyzing chromones and their metabolites.

Biological importance of structurally diversified chromenes

Compounds incorporating the chromene scaffold are largely present in natural products and display a wide variety of biological activities. Their low toxicity combined to the broad pharmacological properties have inspired medicinal chemists in the search for new therapeutic agents. This review covers the literature between 1993 and on the biological activity of 2H- and 4H-chromenes, both from natural and synthetic origin. Includes a section that identifies a selection of chromene-based natural products, followed by recent literature on bioactive natural chromenes and the corresponding source, covering plants and fruits. Synthetic chromenes are equally important and a separate section addresses the use of these derivatives as new leads for drug discovery. Different biological targets were identified, namely those associated with anticancer, antimicrobial, anti-inflammatory, antithrombotic and antipsychotic activities.

Palladium-catalyzed arylation of 2H-chromene: a new entry to pyrano[2,3-c]carbazoles

Various pyrano[2,3-c]carbazoles are synthesized in high yields over five steps from commercially available resorcinol. Palladium-catalyzed arylation remains a key step in this novel strategy. The versatility of this protocol has been demonstrated by the first total synthesis of naturally occurring carbazole clauraila C.

Molecular disorder in (‒)-encecanescin

(‒)-Encecanescin (1) has been isolated from the leaves of Eupatorium aschembornianum. Two conformers are present in the crystal structure as a result of molecular disorder. The structure of 1 was established by ¹H- and ¹³C-NMR spectroscopy in CDCl₃ solution using 2D NMR techniques (gHSQC, gHMBC and NOESY). A Monte Carlo random search using molecular mechanics followed by the geometry optimization of each minimum energy structure using density functional theory (DFT) calculations at the B3LYP/6–31G* level and a Boltzmann analysis of the total energies generated accurate molecular models describing the conformational behavior of 1. The three most stable conformers 2–4 of compound 1 were reoptimized at the B3LYP/6-311++G(d,p) level of theory using CHCl₃ as a solvent. Correlations between the experimental ¹H- and ¹³C-NMR chemical shifts (δ_exp) have been found, and the GIAO/B3LYP/6-311++G(d,p) calculated magnetic isotropic shielding tensors (σ_calc) for conformers 2 and 3, δ_exp = a + b σ_calc, are reported. A good linear relationship between the experimental and calculated NMR data has been obtained for protons and carbon atoms.

Synthesis, characterization and in vitro biological evaluation of some novel diarylsulfonylureas as potential cytotoxic and antimicrobial agents

A series of novel diarylsulfonylureas (1-28) have been synthesized and characterized by FTIR, (1)H NMR, (13)C NMR and LC mass spectral analysis. All the synthesized compounds were evaluated for their in vitro cytotoxicity and antimicrobial activities. Among the tested compounds for cytotoxicity using Brine Shrimp Lethality assay, compounds 18 and 22 exhibited significant cytotoxicity at ED(50) values 3.96±0.21 and 4.02±0.19μg/mL, respectively. This level of activity was found comparable to that of the reference drug podophyllotoxin with ED(50) value 3.61±0.17μg/mL and it could be a remarkable starting point to develop new lead molecules with major cytotoxicity. Antimicrobial activity was screened using agar well diffusion assay method against selected Gram-positive, Gram-negative and fungal strains. Most of the compounds showed promising antibacterial and antifungal activity and the activity expressed as the minimum inhibitory concentration (MIC) in μg/mL.

KATP channel openers of the benzopyran type reach their binding site via the cytosol

BACKGROUND AND PURPOSE

ATP-sensitive K+ (KATP) channels are composed of pore-forming subunits (Kir6.x) and of sulphonylurea receptors (SUR). Both sulphonylureas and K(ATP) channel openers act by binding to SUR. Sulphonylureas reach their binding site from the cytosol but it remains unknown whether this holds for openers too.

EXPERIMENTAL APPROACH

A poorly membrane-permeant sulphonic acid derivative of the benzopyran-type opener, bimakalim, was synthesized, descyano-bimakalim-6-sulphonic acid (BMSA). Binding of BMSA and bimakalim was compared in membranes and intact cells expressing the Kir6.2/SUR2B channel and channel opening was compared in inside-out patches and whole cells.

KEY RESULTS

In membranes, bimakalim and BMSA bound to Kir6.2/SUR2B with Ki values of 61 nM and 4.3 microM, showing that the negative charge decreased affinity 69-fold. In intact cells, however, binding of BMSA was much weaker than in membranes (75-fold) whereas that of bimakalim was unchanged. The Ki value of BMSA decreased with increasing incubation time. In inside-out patches, bimakalim (1 microM) and BMSA (100 microM) opened the Kir6.2/SUR2B channel closed by MgATP to a similar degree whereas in whole-cell experiments, only bimakalim was effective.

CONCLUSIONS AND IMPLICATIONS

Despite its negative charge, BMSA is an effective channel opener. The fact that BMSA binds and acts more effectively when applied to the inner side of the cell membrane shows that benzopyran openers reach their binding site at SUR from the cytosol. This suggests that the binding pocket of SUR is only open on the cytoplasmic side.

Binding studies and GRIND/ALMOND-based 3D QSAR analysis of benzothiazine type K(ATP)-channel openers

For seventeen 1,4-benzothiazine potassium channel openers, we performed binding studies in rat aortic smooth muscle cells and cardiomyocytes, compared their binding affinities with published relaxation data, and derived 3D-QSAR models using GRIND/ALMOND descriptors. Binding affinities in smooth muscle cells range from a pK(D) of 4.76 for compound 3e to 9.10 for compound 4c. Comparison of data for smooth muscle relaxation and binding shows preferentially higher pEC(50)s for the former. In cardiomyocytes, pK(D) values range from 4.21 for 3e to 8.16 for 4c. 3D-QSAR analysis resulted in PLS models of two latent variables for all three activities with determination coefficients of 0.97 (smooth muscle relaxation) and 0.94 (smooth muscle cells- and cardiomyocytes-binding). Internal validation yielded q(2) values of 0.69, 0.66, and 0.64. The carbonyl on the N-4 substituent, the hydrogen bond acceptor at C-6, the five-membered ring at N-4, and the gem-dimethyls mainly guide strong binding and strong smooth muscle relaxation.

Oxidation of Aromatic Lithium Thiolates into Sulfinate Salts: An Attractive Entry to Aryl Sulfones Labeled with Carbon-11

[reaction: see text] Aromatic 11C-sulfones were synthesized by S alkylation of lithium arenesulfinates, which are readily available from the corresponding thiols by an oxaziridine-mediated oxidation reaction with [11C]alkyl iodides in THF/H2O (4:1) at 150 degrees C. The radiosyntheses, including purification by HPLC, were completed in an average of 35 min from the end of the bombardment with 55-76% overall radiochemical yields (decay corrected). The described procedure extends the range of accessible labeling methods.

KATP channel openers: structure-activity relationships and therapeutic potential

ATP-sensitive potassium channels (K(ATP) channels) are heteromeric complexes of pore-forming inwardly rectifying potassium channel subunits and regulatory sulfonylurea receptor subunits. K(ATP) channels were identified in a variety of tissues including muscle cells, pancreatic beta-cells, and various neurons. They are regulated by the intracellular ATP/ADP ratio; ATP induces channel inhibition and MgADP induces channel opening. Functionally, K(ATP) channels provide a means of linking the electrical activity of a cell to its metabolic state. Shortening of the cardiac action potential, smooth muscle relaxation, inhibition of both insulin secretion, and neurotransmitter release are mediated via K(ATP) channels. Given their many physiological functions, K(ATP) channels represent promising drug targets. Sulfonylureas like glibenclamide block K(ATP) channels; they are used in the therapy of type 2 diabetes. Openers of K(ATP) channels (KCOs), for example, relax smooth muscle and induce hypotension. KCOs are chemically heterogeneous and include as different classes as the benzopyrans, cyanoguanidines, thioformamides, thiadiazines, and pyridyl nitrates. Examples for new chemical entities more recently developed as KCOs include cyclobutenediones, dihydropyridine related structures, and tertiary carbinols.