Discovery of fused heterocyclic carboxamide derivatives as novel α7-nAChR agonists: Synthesis, preliminary SAR and biological evaluation

Small molecule ligands for α9* and α7 nicotinic receptors: a survey and an update, respectively

The α9- and α7-containing nicotinic acetylcholine receptors (nAChRs) mediate numerous physiological and pathological processes by complex mechanisms that are currently the subject of intensive study and debate. In this regard, selective ligands serve as invaluable investigative tools and, in many cases, potential therapeutics for the treatment of various CNS disfunctions and diseases, neuropathic pain, inflammation, and cancer. However, the present scenario differs significantly between the two aforementioned nicotinic subtypes. Over the past few decades, a large number of selective α7-nAChR ligands, including full, partial and silent agonists, antagonists, and allosteric modulators, have been described and reviewed. Conversely, reports on selective α9-containing nAChR ligands are relatively scarce, also due to a more recent characterization of this receptor subtype, and hardly any focusing on small molecules. In this review, we focus on the latter, providing a comprehensive overview, while providing only an update over the last five years for α7-nAChR ligands.

Heterocyclic compounds derived from cyclohexane-1,4-dione: synthesis of tetrahydro-4H-chromene and tetrahydrobenzo[d]thiazole derivatives as target SARS-CoV-2 main protease (Mpro) and potential anti-Covid-19

Tetrahydro-4H-chromene-3-carbonitrile derivatives 4a-c where prepared from the reaction of 1,4-cyclohexane dione (1), malononitrile (2) and either of benzaldehyde (3a), 2-chlorobenzaldehyde (3b) or 4-methoxybenzaldehyde (3c) in ethanol containing triethylamine. Compound 4b was used to prepare pyrazole, pyrimidine and thiazole derivatives. Moreover, tetrahydrobenzo[d]thiazole derivative 18 was prepared from the reaction of 1,4-cyclohexane dione (1) with elemental sulfur followed by phenyl isothiocyanate (12) in absolute ethanol containing triethylamine. The latter compound reacted with ethyl orthoformate and either malononitrile or ethyl cyanoacetate in 1,4-dioxane in the presence of triethylamine to produce the 9-ethoxy-2H-chromeno[6,5-d]thiazole derivatives 20a,b. In addition, fused thiophene and pyran derivatives were synthesized starting from compound 18. The screened compounds were designed as mimics of the transition state of RNA2’-O-methylation were screened against several viral RNA 2’-OMTases from SARS-CoV (nsp10/nsp16 complex), Zika, West Nile, dengue, vaccinia (VP39) viruses. At the same time, the compounds were tested against human RNA N7-MTase (hRNMT) and selected viral N7-MTases such as SARS-CoV nsp14 and vaccinia D1-D12 complex to evaluate their specificity. Compounds 4a, 4b, 6b, 6c, 6e, 9a, 9b, 15, 16, 21b, and 23b showed high % inhibitions against SARs-Cov nsp 14 with values 93.42, 87.49, 98.23, 88.15, 89.24, 96.31, 93.28, 89.25, 89.20, 87.24, and 94.49, respectively.

An approach to pharmacological targets of pyrrole family from a medicinal chemistry viewpoint

Pyrrole is one of the most widely used heterocycles in the pharmaceutical industry. Due to the importance of pyrrole structure in drug design and development, herein, we tried to conduct an extensive review of the bioactive pyrrole based compounds reported recently. The bioactivity of pyrrole derivatives varies, so in the review, we categorized them based on their direct pharmacologic targets. Therefore, readers are able to find the variety of biologic targets for pyrrole containing compounds easily. This review explains around seventy different biologic targets for pyrrole based derivatives, so, it is helpful for medicinal chemists in design and development novel bioactive compounds for different diseases. This review presents an extensive meaningful structure activity relationship for each reported structure as much as possible. The review focuses on papers published between 2018 and 2020.

Therapeutic Targeting of α7 Nicotinic Acetylcholine Receptors

The α7-type nicotinic acetylcholine receptor is one of the most unique and interesting of all the members of the cys-loop superfamily of ligand-gated ion channels. Since it was first identified initially as a binding site for α-bungarotoxin in mammalian brain and later as a functional homomeric receptor with relatively high calcium permeability, it has been pursued as a potential therapeutic target for numerous indications, from Alzheimer disease to asthma. In this review, we discuss the history and state of the art for targeting α7 receptors, beginning with subtype-selective agonists and the basic pharmacophore for the selective activation of α7 receptors. A key feature of α7 receptors is their rapid desensitization by standard "orthosteric" agonist, and we discuss insights into the conformational landscape of α7 receptors that has been gained by the development of ligands binding to allosteric sites. Some of these sites are targeted by positive allosteric modulators that have a wide range of effects on the activation profile of the receptors. Other sites are targeted by direct allosteric agonist or antagonists. We include a perspective on the potential importance of α7 receptors for metabotropic as well as ionotropic signaling. We outline the challenges that exist for future development of drugs to target this important receptor and approaches that may be considered to address those challenges. SIGNIFICANCE STATEMENT: The α7-type nicotinic acetylcholine receptor (nAChR) is acknowledged as a potentially important therapeutic target with functional properties associated with both ionotropic and metabotropic signaling. The functional properties of α7 nAChR can be regulated in diverse ways with the variety of orthosteric and allosteric ligands described in this review.

Design, synthesis and biological activities of piperidine-spirooxadiazole derivatives as α7 nicotinic receptor antagonists

α: 7 nicotinic acetylcholine receptors (nAChRs) expressed in the nervous and immune systems have been suggested to play important roles in the control of inflammation. However, the lack of antagonist tools specifically inhibiting α7 nAChR impedes the validation of the channel as therapeutic target. To discover a selective α7 antagonist, we started a pharmacophore-based virtual screening and identified a piperidine-spirooxadiazole derivative T761-0184 that acts as a α7 antagonist. A series of novel piperidine-spirooxadiazole derivatives were subsequently synthesized and evaluated using two-electrode voltage clamp (TEVC) assay in Xenopus oocytes. Lead compounds from two series inhibited α7 with their IC₅₀ values ranging from 3.3 μM to 13.7 μM. Compound B10 exhibited α7 selectivity over other α4β2 and α3β4 nAChR subtypes. The analysis of structure-activity relationship (SAR) provides valuable insights for further development of selective α7 nAChR antagonists.