Discovery and biological profile of 4-(1-aryltriazol-4-yl)-tetrahydropyridines as an orally active new class of metabotropic glutamate receptor 1 antagonist

A copper-catalysed one-pot hydroboration/azidation/cycloaddition reaction of alkynes

Herein we report our study on the development of a catalytic one-pot process, showing the challenges and advantages encountered all over the way. At the end, we developed a regioselective, environmentally friendly, and operationally simple method to explore the reactivity of functionalized propargylic alkynes through three copper-catalysed reactions in a single reaction vessel. The sequence consisted of a hydroboration, azidation, and 1,3-dipolar cycloaddition and led to the regioselective formation of vinyl 1,2,3-triazoles in good yields.

Design and synthesis of 3,3'-triazolyl biisoquinoline N,N'-dioxides via Hiyama cross-coupling of 4-trimethylsilyl-1,2,3-triazoles

A new strategy to effectively lock the conformation of substituents at the 3,3'-positions of axial-chiral biisoquinoline N,N'-dioxides was developed based on the strong dipole-dipole interaction between 1,2,3-triazole and pyridine N-oxide rings. The crystal structure and the DFT calculations of 3,3'-bis(1-benzyl-1H-1,2,3-triazole-4-yl)-1,1'-biisoquinoline N,N'-dioxide (3a) provided strong support for this strategy. Furthermore, we successfully demonstrated that readily available 4-trimethylsilyl-1,2,3-triazoles are viable nucleophiles for Hiyama cross-coupling.

Organocatalytic enone-azide [3 + 2]-cycloaddition: synthesis of functionally rich C/N-double vinyl 1,2,3-triazoles

An enolate-mediated organocatalytic [3 + 2]-cycloaddition of enones with less reactive vinyl/alkyl/aryl azides is reported at room temperature for short reaction times. The metal-free amine-mediated catalytic conditions of this [3 + 2]-cycloaddition allowed us to synthesize a collection of C/N-double vinyl-1,2,3-triazoles and C-vinyl-1,2,3-triazoles through functionalized enones as quality azidophiles with various azides. It is an efficient catalytic [3 + 2]-cycloaddition for the synthesis of biologically important fully decorated C/N-double vinyl-1,2,3-triazoles with excellent outcomes with reference to the reaction rate, selectivity, operation simplicity, substrate scope, yields, and synthetic applications as demonstrated in the paper. Herein, we illustrated the importance of enolate reactivity with azides compared to enamines by correlation with previous enamine-mediated click reactions in the reaction mechanism section.

Regioselective Synthesis of Diverse Thio-, Seleno-substituted 1,2,3-Triazoles

:

Thio-, seleno-substituted triazoles are useful scaffolds employed in the fields of organic synthesis, medicinal chemistry, and material science. A number of synthetic approaches to efficient formation of thio- and seleno-triazoles have been disclosed, including the interception of copper(I) triazolides generated in-situ, cycloaddition of internal alkynes (thio-, halo-, and metalated alkynes) to azides, and the coupling of azides and nonalkyne substrates. This mini-review intends to summarize the synthetic methods toward thio-, seleno-1,2,3-triazoles and the relative reaction mechanisms.

Discovery and Development of Non-Dopaminergic Agents for the Treatment of Schizophrenia: Overview of the Preclinical and Early Clinical Studies

Schizophrenia is a chronic psychiatric disorder that affects about 1 in 100 people around the world and results in persistent emotional and cognitive impairments. Untreated schizophrenia leads to deterioration in quality of life and premature death. Although the clinical efficacy of dopamine D2 receptor antagonists against positive symptoms of schizophrenia supports the dopamine hypothesis of the disease, the resistance of negative and cognitive symptoms to these drugs implicates other systems in its pathophysiology. Many studies suggest that abnormalities in glutamate homeostasis may contribute to all three groups of schizophrenia symptoms. Scientific considerations also include disorders of gamma-aminobutyric acid-ergic and serotonergic neurotransmissions as well as the role of the immune system. The purpose of this review is to update the most recent reports on the discovery and development of non-dopaminergic agents that may reduce positive, negative, and cognitive symptoms of schizophrenia, and may be alternative to currently used antipsychotics. This review collects the chemical structures of representative compounds targeting metabotropic glutamate receptor, gamma-aminobutyric acid type A receptor, alpha 7 nicotinic acetylcholine receptor, glycine transporter type 1 and glycogen synthase kinase 3 as well as results of in vitro and in vivo studies indicating their efficacy in schizophrenia. Results of clinical trials assessing the safety and efficacy of the tested compounds have also been presented. Finally, attention has been paid to multifunctional ligands with serotonin receptor affinity or phosphodiesterase inhibitory activity as novel strategies in the search for dedicated medicines for patients with schizophrenia.

Reaction engineering and photophysical studies of fully enriched C-vinyl-1,2,3-triazoles

A library of fluorogenic C-vinyl-1,2,3-triazoles were synthesized in very good yields with excellent selectivity by using an organocatalytic formal [3 + 2]-cycloaddition. One of the coumarin-triazoles 4ba has shown excellent fluorescence properties (λ_em = 533 nm).

Base free regioselective synthesis of α-triazolylazine derivatives

A regioselective α-heteroarylation followed by deoxygenation towards the synthesis of variety of azine triazole from simple azine N-oxides derivatives and N-tosyl-1,2,3-triazoles has been described.

One-pot synthesis of fused benzoxazino[1,2,3]triazolyl[4,5-c]quinolinone derivatives and their anticancer activity

Cu/Pd catalyzed one pot synthesis of fused benzoxazino[1,2,3]triazolyl[4,5-c]quinolinone hybrids and their cytotoxic activity against human cancer cell lines MCF-7, HeLa and A-549 is described.

Azide–acetonitrile “click” reaction triggered by Cs2CO3: the atom-economic, high-yielding synthesis of 5-amino-1,2,3-triazoles

Medicinally important 5-amino-1,2,3-triazoles were synthesized using a novel Cs₂CO₃-catalyzed azide–acetonitrile [3 + 2]-cycloaddition. Aryl azides and aryl acetonitriles were employed in this transformation resulting in excellent yields with high regioselectivity.

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0(2,7)]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product.

Triazole Appending Agent (TAAG): A New Synthon for Preparing Iodine-Based Molecular Imaging and Radiotherapy Agents

A new prosthetic group referred to as the triazole appending agent (TAAG) was developed as a means to prepare targeted radioiodine-based molecular imaging and therapy agents. Tributyltin-TAAG and the fluorous analogue were synthesized in high yield using simple click chemistry and the products labeled in greater than 95% RCY with (123)I. A TAAG derivative of an inhibitor of prostate-specific membrane antigen was prepared and radiolabeled with (123)I in 85% yield where biodistribution studies in LNCap prostate cancer tumor models showed rapid clearance of the agent from nontarget tissues and tumor accumulation of 20% injected dose g(-1) at 1 h. The results presented demonstrate that the TAAG group promotes minimal nonspecific binding and that labeled conjugates can achieve high tumor uptake and exquisite target-to-nontarget ratios.

Recent advances in the medicinal chemistry of the metabotropic glutamate receptor 1 (mGlu₁)

This Review summarizes the medicinal chemistry found in publications on both orthosteric and allosteric modulators of the metabotropic glutamate receptor 1 (mGlu(1)) from 2005 to the present. The time period covered by the scope of this current review has been particularly rich in mGlu(1)-related publications with numbers quadrupling when compared to the preceding five year period of 2000-2005. Publications in the field peaked in 2007 with over 35 articles appearing in the peer reviewed literature in the course of that year. Given that glutamate is one of the primary excitatory neurotransmitters in the mammalian central nervous system (CNS), it is unsurprising that it acts upon several receptors that are considered to be of potential therapeutic interest for many indications. Orthosteric and allosteric modulation of the receptor is possible, with a logical extrapolation to the chemotypes used for each strategy. The last five years of publications have yielded many mGlu(1) selective antagonist chemotypyes, most of which have shown efficacy in pain in vivo models. However, the primary impact of these compounds has been to highlight the mechanistic safety risks of mGlu(1) antagonism, independent of chemotype. As a review in medicinal chemistry, the primary focus of this paper will be on the design and, to a lesser degree, synthetic strategies for the delivery of subtype selective, CNS penetrant, druglike compounds through a "medchem" program, targeting modulators of the mGlu(1) receptor.

Discovery of novel mGluR1 antagonists: a multistep virtual screening approach based on an SVM model and a pharmacophore hypothesis significantly increases the hit rate and enrichment factor

Development of glutamate non-competitive antagonists of mGluR1 (Metabotropic glutamate receptor subtype 1) has increasingly attracted much attention in recent years due to their potential therapeutic application for various nervous disorders. Since there is no crystal structure reported for mGluR1, ligand-based virtual screening (VS) methods, typically pharmacophore-based VS (PB-VS), are often used for the discovery of mGluR1 antagonists. Nevertheless, PB-VS usually suffers a lower hit rate and enrichment factor. In this investigation, we established a multistep ligand-based VS approach that is based on a support vector machine (SVM) classification model and a pharmacophore model. Performance evaluation of these methods in virtual screening against a large independent test set, M-MDDR, show that the multistep VS approach significantly increases the hit rate and enrichment factor compared with the individual SB-VS and PB-VS methods. The multistep VS approach was then used to screen several large chemical libraries including PubChem, Specs, and Enamine. Finally a total of 20 compounds were selected from the top ranking compounds, and shifted to the subsequent in vitro and in vivo studies, which results will be reported in the near future.

Development of a β-Lactamase Reporter Gene Assay for Metabotropic Glutamate Receptor 1 by Using Coexpression of Glutamate Transporter

mGluR1 antagonists have been postulated to be novel CNS drugs, including antipsychotics. Toward this end, the authors developed a β-lactamase reporter assay to identify mGluR1 antagonists. β-Lactamase has several interesting features for high-throughput screening, including very high sensitivity and less well-to-well variation than other reporter enzymes. mGluR1-expressing Chinese hamster ovary (CHO) cells with the β-lactamase gene under control of the nuclear factor of activated T cells (NFAT) promoter (CHO-NFAT-bla-hmGluR1b) exhibited very high basal activity, resulting in an inadequate signal-to-basal (S/B) ratio. Coexpression of glutamate/aspartate transporter (GLAST) with mGluR1 in the cell line (CHO-NFAT-bla-hmGluR1b-GLAST) dramatically decreased basal activity and improved the S/B ratio (from 2- to 20-fold). The contribution of GLAST to lowering basal activity and increasing the S/B ratio was validated by the expression level of GLAST mRNA and by a GLAST inhibitor. Antagonistic activities of known mGluR1 antagonists in the β-lactamase reporter assay were comparable with those in the conventional Ca2+ mobilization assay. The Z′ factor of the β-lactamase reporter assay was 0.89 under optimized conditions. Taken together, the β-lactamase reporter assay with CHO-NFAT-bla-hmGluR1b-GLAST could be a novel high-throughput assay for mGluR1 antagonist screening. This is the first description of a successful β-lactamase reporter assay among all mGluR subtypes.

Discovery and in vitro and in vivo profiles of 4-fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide as novel class of an orally active metabotropic glutamate receptor 1 (mGluR1) antagonist

We identified 4-fluoro-N-[4-[6-(isopropylamino)pyrimidin-4-yl]-1,3-thiazol-2-yl]-N-methylbenzamide 27 as a potent mGluR1 antagonist. The compound possessed excellent subtype selectivity and good PK profile in rats. It also demonstrated relatively potent antipsychotic-like effects in several animal models. Suitable for development as a PET tracer, compound 27 would have great potential for elucidation of mGluR1 functions in human.

Synergism of virtual screening and medicinal chemistry: identification and optimization of allosteric antagonists of metabotropic glutamate receptor 1

We report the identification of novel potent and selective metabotropic glutamate receptor 1 (mGluR1) antagonists by virtual screening and subsequent hit optimization. For ligand-based virtual screening, molecules were represented by a topological pharmacophore descriptor (CATS-2D) and clustered by a self-organizing map (SOM). The most promising compounds were tested in mGluR1 functional and binding assays. We identified a potent chemotype exhibiting selective antagonistic activity at mGluR1 (functional IC(50)=0.74+/-0.29 microM). Hit optimization yielded lead structure 16 with an affinity of K(i)=0.024+/-0.001 microM and greater than 1000-fold selectivity for mGluR1 versus mGluR5. Homology-based receptor modelling suggests a binding site compatible with previously reported mutation studies. Our study demonstrates the usefulness of ligand-based virtual screening for scaffold-hopping and rapid lead structure identification in early drug discovery projects.