Silicomolybdic Acid Cluster as Biocompatible Catalyst for One-Pot Tandem Synthesis of Orthogonally Protected Glycosides.

The present paper describes a new and practical approach for the one-pot preparation of O-isopropylidene derivatives and also orthogonally protected S- and O-glycosides from the corresponding unprotected saccharides by employing 2 mol % of a silicomolybdic acid (SMA) cluster as a versatile and biocompatible catalyst. The present protocol is applicable to two-step one-pot tandem transformations, which include the O-isopropylidation, spiroketal functionalization, 4,6-O-arylidene acetalations, and arylidene acetylation processes under relatively mild reaction conditions. One-pot sequential transformations, low catalyst loading, rapid transformation, high to excellent reaction yields, mild reaction conditions, and a nontoxic biocompatible workup procedure are the notable advantages of devised protocol.

Organocatalyzed Regioselective Synthesis of 1,5-Disubstituted 1,2,3-Triazolyl Glycoconjugates.

A novel organocatalyzed [3+2] cycloaddition reaction of nitroolefins with glycosyl azides as well as organic azides has been developed for successful construction of 1,5-disubstituted triazolyl glycoconjugates. This metal-free and acid-free, regioselective synthetic protocol proceeds in the presence of only Schreiner thiourea organocatalysts, which enable the required activation of nitroolefins through double hydrogen bonding. The straightforward, operationally simple, and regioselectivity of this methodology, complementing to the classical RuAAC catalyzed synthesis of 1,5-disubstituted 1,2,3-triazoles. In the presence of catalytic amount of Schreiner thiourea organocatalyst, organic azides react with a broad array of nitroolefins producing a series of diverse 1,5-disubstituted 1,2,3- triazoles in good yields with excellent regioselectivity.

Growing Impact of Intramolecular Click Chemistry in Organic Synthesis.

Click Chemistry, a modular, rapid, and one of the most reliable tool for the regioselective 1,2,3-triazole forming [3+2] reaction of organic azide and terimal alkyne is widely explored in various emerging domains of research ranging from chemical biology to catalysis and medicinal chemistry to material science. This regioselective reaction from a diverse range of azido-alkyne scaffolds has been well performed in both intermolecular as well as intramolecular fashions. In comparison to the intermolecular metal (Cu/Ru/Ni) variant of 'Click Chemistry', the intramolecular click tool is little addressed. The intramolecular click chemistry is exemplified as a mordern tool of cyclization which involves metal-catalyzed (CuAAC/RuAAC) cyclization, organo-catalyzed cyclization, and thermal-induced topochemical reaction. Thus, we report herein the recent approaches on intramolecular azide-alkyne cycloaddition 'Click Chemistry' with their wide-spread emerging applications in the developement of a diverse range of molecules including fused-heterocycles, well-defined peptidomemics, and macrocyclic architectures of various notable features.

Triazole-Appended Glycohybrid/CuI-Catalyzed C-C Cross-Coupling of Aryl/Heteroaryl Halides with Alkynyl Sugars.

This report describes a convenient method for the Cu(I)-catalyzed Sonogashira cross-coupling reaction of aryl/heteroaryl halides and alkynyl sugars in the presence of a 1,2,3-triazole-appended glycohybrid as a biocompatible ligand. The Sonogashira cross-coupling products were exclusively formed without the Glaser-Hay homocoupling reaction in the presence of a glycosyl monotriazolyl ligand at 120 °C. However, the Glaser-Hay homocoupling products were obtained at 60-70 °C in the presence of bis-triazolyl-based macrocyclic glycohybrid ligand L8. The glycosyl triazole ligands were synthesized via the CuI/DIPEA-mediated regioselective CuAAC click reaction, and a series of glycohybrids of glucose, mannose, and galactose alkynes including glycosyl rods were developed in good yields. The developed glycohybrids have been well characterized by various spectroscopic techniques, such as nuclear magnetic resonance, high-resolution mass spectrometry, and single-crystal X-ray data of L3. The protocol works well with the heteroaryl and naphthyl halides, and the mechanistic approach leads to CuI/ligand-assisted oxidative coupling. The coupling protocol has notable features, including low catalytic loading, cost-effectiveness, biocompatible nature, and a wide substrate scope.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications.

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Design, Synthesis, and Docking Study of Quinine-9-Triazolyl Conjugates.

To develop a better chemotherapeutically potential candidate for lung cancer treatment and cure with repurposed motifs, quinine has been linked with biocompatible CuAAC-inspired regioselective 1,2,3-triazole linker and a series of ten novel 1,2,3-triazolyl-9-quinine conjugates have been developed by utilizing click conjugation of glycosyl ether alkynes with 9-epi-9-azido-9-deoxy-quinine under standard click conditions. In parallel, the docking study indicated that the resulting conjugates have an overall appreciable interaction with ALK-5 macromolecules. Moreover, the mannose-triazolyl conjugate exhibited the highest binding interactions of -7.6 kcal/mol with H-bond interaction with the targeted macromolecular system and indicate the hope for future trials for anti-lung cancer candidates.

Pyridyl Glycosyl Triazole/CuI-Mediated Domino/Tandem Synthesis of Quinazolinones.

The glycosyl 1,2,3-triazoles are expediently accessible from readily available sugar-derived glycosyl azide by utilizing modular CuAAC "Click Chemistry", and the resulting glycohybrid skeleton possesses efficient metal-coordinating centers that support a wide range of metal-mediated efficient catalysis in various imperative organic transformations. Here, we designed and developed pyridyl glycosyl triazoles by employing the CuAAC reaction of d-glucose-derived glycosyl azides and alkynyl pyridines. These pyridyl glycosyl triazoles with Cu(I) salt were explored as an efficient catalyst to successfully assemble 2-amino-3-substituted and 3-substituted quinazolinones by the domino/tandem cross-coupling reaction of various N-substituted o-halobenzamides with cyanamide and formamide, respectively. The devised protocol has some notable features, including biocompatibility, low cost, easily accessible starting materials for the glycosyl ligands, high yield, broad spectrum, low catalytic loading, and mild reaction conditions.

Development of Diverse Range of Biologically Relevant Carbohydrate-Containing Molecules: Twenty Years of Our Journey*.

There is an increasing demand for significant amount of carbohydrate-containing molecules owing to their complete chemical, biological, and pharmacological investigations to better understand their role in many important biological events. Clinical studies of a wide range of simple carbohydrates or their derivatives, glycohybrids, glycoconjugates, and neoglycoconjugates have been conducted worldwide for the successful treatment of various frontline diseases. Herein, a brief perspective of carbohydrate-based molecular scaffolding and my experience during the last 20 years in the area of synthetic carbohydrate chemistry, mainly for their impact in drug discovery & development, is presented.

Glycosyl Triazole Ligand for Temperature-Dependent Competitive Reactions of Cu-Catalyzed Sonogashira Coupling and Glaser Coupling.

Glycosyl triazoles have been introduced as efficient ligands for the Cu-catalyzed Sonogashira reaction to overcome the challenges of sideways homocoupling reactions in Cu catalysis in this reaction. The atmospheric oxygen in a sealed tube did not affect the coupling, and no need of complete exclusion of oxygen was experienced in the presence of glycohybrid triazole ligand L3. High product yields were obtained at 130 °C for a variety of substrates including aliphatic and aromatic terminal alkynes and differently substituted aromatic halides including 9-bromo noscapine. In contrast, at room temperature, a very low loading of the L3-Cu catalytic system could produce excellent yields in Glaser coupling including homocoupling and heterocoupling of a variety of aliphatic and aromatic alkynes.

Synthesis of a Series of a Few Hydrosulfide Complexes of Cu(I). A µ3-SH-Bridged Rare Cubane-like Tetramer Showing Efficient Catalytic Activity toward Azide-Alkyne Cycloaddition.

A cubane-like tetranuclear hydrosulfido complex of Cu(I), [Cu4(SH)4(PPh3)4] (1), has been synthesized by the reaction of Cu(NO3)2·3H2O, NaSCOPh, and Cu(PPh3)2NO3 and characterized structurally. Complex 1 represents the first example of crystallographically characterized µ3-SH-bridged cubanoid hydrosulfide. By direct reactions of [(PPh3)2Cu(NO3)] and NaSH, neutral hydrosulfide complexes [Cu(SH)(PPh3)2]·C6H6 (2), [Cu2(SH)2(PPh3)3] (3), and [Cu2(SH)2(PPh3)4] (4) have also been synthesized and structurally characterized. Complex 2 is monomeric with a terminal hydrosulfide ligand. The other two, 3 and 4, are µ2-SH-bridged unsymmetrical and symmetrical dinuclear complexes, respectively. In the symmetric one (4), both Cu(I) ions are tetrahedrally coordinated while in the unsymmetric one (3), one Cu(I) ion is tetrahedral and the other one has a trigonal-planar coordination geometry. The catalytic activity of a hydrosulfido complex in a "click" azide-alkyne cycloaddition reaction has been explored for the first time, and complex 1 is found to be an efficient catalyst for the regioselective synthesis of glycoconjugate triazoles.

Cu-Catalyzed Click Reaction in Carbohydrate Chemistry.

Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC), popularly known as the "click reaction", serves as the most potent and highly dependable tool for facile construction of simple to complex architectures at the molecular level. Click-knitted threads of two exclusively different molecular entities have created some really interesting structures for more than 15 years with a broad spectrum of applicability, including in the fascinating fields of synthetic chemistry, medicinal science, biochemistry, pharmacology, material science, and catalysis. The unique properties of the carbohydrate moiety and the advantages of highly chemo- and regioselective click chemistry, such as mild reaction conditions, efficient performance with a wide range of solvents, and compatibility with different functionalities, together produce miraculous neoglycoconjugates and neoglycopolymers with various synthetic, biological, and pharmaceutical applications. In this review we highlight the successful advancement of Cu(I)-catalyzed click chemistry in glycoscience and its applications as well as future scope in different streams of applied sciences.

Click inspired synthesis of triazole-linked vanillin glycoconjugates.

The 1,3-dipolar cycloaddition of deoxy-azido sugars 1 with alkyne derivatives of p-vanillin, 3-methoxy-4-(prop-2-ynyloxy)benzaldehyde (2) and 2-methoxy-1-(prop-2-ynyloxy)-4-((prop-2-ynyloxy)methyl)benzene) (4) to afford regioselective triazole-linked vanillinglycoconjugates 5 and 6 was investigated in the presence of CuI/DIPEA in dichloromethane. All the developed glycoconjugates were characterized on the basis of IR, NMR, and MS. Graphical abstract Triazolyl vanillin glycoconjugates via click chemistry.

Click inspired synthesis of antileishmanial triazolyl O-benzylquercetin glycoconjugates.

The 1,3-dipolar cycloaddition of deoxy-azido sugars 1 with O-benzylquercetin alkynes (5-7) to afford regioselective triazole-linked O-benzylquercetin glycoconjugates (8-10) was investigated in the presence of CuI/DIPEA in dichloromethane. All the developed glycoconjugates (8-10) were evaluated for anti-leishmanial activity against the promastigotes and amastigotes of Leishmania donovani. Graphical Abstract Click Inspired Synthesis of Antileishmanial Triazolyl O-Benzylquercetin Glycoconjugates.

One-Pot Synthesis of Glycosyl-ß-azido Ester via Diazotransfer Reaction Toward Access of Glycosyl-ß-triazolyl Ester.

A concise and efficacious one-pot protocol for the synthesis of novel glycosyl-ß-azido ester 3 from glycosyl olefinic ester 1 under mild conditions has been devised. The ß-aminoester, formed by the conjugate addition of ammonia on olefinic ester, undergoes a metal-catalyzed diazotransfer reaction to furnish glycosyl-ß-azido ester. The optimized conditions for diazotransfer reaction indicate that imidazole-1-sulphonyl azide and K2CO3 give the best results in the presence of ZnCl2. A diverse range of novel regioselective triazolyl glycoconjugates 6a-u have been achieved in high yields via 1,3-dipolar cycloaddition of compound 3 with various alkynes in the presence of CuI/DIPEA. Structures of all the compounds have been elucidated using IR, NMR, MS, and elemental analysis, and four of them (3a, 3b, 4b, and 6a) have also been characterized by single crystal X-ray diffraction analysis.

Click chemistry inspired synthesis of morpholine-fused triazoles.

The synthesis of triazolyl azido alcohols from terminal alkyne via oxirane ring-opening of epichlorohydrin, followed by click reaction with alkynes, and subsequent azidation of chlorohydroxy triazoles was achieved under a one-pot methodology. The developed triazolyl azido alcohols were further utilized for the synthesis of a diverse range of morpholine-fused triazoles of chemotherapeutic value. The structure of all developed compounds has been elucidated using IR, NMR, MS, and elemental analysis, where four of them have been characterized by single-crystal X-ray analysis.

Synthesis of 2-N/S/C-substituted benzothiazoles via intramolecular cyclative cleavage of benzotriazole ring.

The synthesis of numerous 2-N/S/C-substituted benzothiazoles was achieved from substituted thiocarbonylbenzotriazoles via free-radical intramolecular cyclative cleavage of the benzotriazole ring in the presence of (TMS)3SiH and AIBN under mild conditions. The developed methodology demonstrates significant compatibility under microwave conditions and is important as it avoids the use of toxic metals for radical cyclization.

Natural product based leads to fight against leishmaniasis.

The growing incidence of parasitic resistance against generic pentavalent antimonials, specifically for visceral disease in Indian subcontinent, is a serious issue in Leishmania control. Notwithstanding the two treatment alternatives, that is amphotericin B and miltefosine are being effectively used but their high cost and therapeutic complications limit their use in endemic areas. In the absence of a vaccine candidate, identification, and characterization of novel drugs and targets is a major requirement of leishmanial research. This review describes current drug regimens, putative drug targets, numerous natural products that have shown promising antileishmanial activity alongwith some key issues and strategies for future research to control leishmaniasis worldwide.

Recent Progress on Synthesis of Functionalized 1,5-Disubstituted Triazoles.

Immediately after the invention of 'Click Chemistry' in 2002, the regioselective 1,2,3- triazole scaffolds resulted from respective organic azides and terminal alkynes under Cu(I) catalysis have been well recognized as the functional heterocyclic core at the centre of modern organic chemistry, medicinal chemistry, and material sciences. This CuAAC reaction has several notable features including excellent regioselectivity, high-to-excellent yields, easy to execute, short reaction time, modular in nature, mild condition, readily available starting materials, etc. Moreover, the resulting regioselective triazoles can serve as amide bond isosteres, a privileged functional group in drug discovery and development. More than hundreds of reviews had been devoted to the 'Click Chemistry' in special reference to 1,4-disubstituted triazoles, while only little efforts were made for an opposite regioisomer i.e., 1,5-disubstituted triazole. Herein, we have presented various classical approaches for an expeditious synthesis of a wide range of biologically relevant 1,5- disubstituted 1,2,3-triazole analogues. The syntheses of such a class of diversly functionalized triazoles have emerged as a crucial investigation in the domain of chemistry and biology. This tutorial review covers the literature assessment on the development of various synthetic protocols for the functionalized 1,5-disubstituted triazoles reported during the last 12 years.

Corrigendum to: Recent Progress on Synthesis of Functionalized 1,5- disubstituted Triazoles.

Two errors appeared in the text of the manuscript titled "Recent Progress on Synthesis of Functionalized 1,5- disubstituted Triazoles", 2024; 21(4) : 513-558 [1]. We regret the errors and apologize to readers. The original article can be found online at: https://www.eurekaselect.com/article/131107.

Design, synthesis, and docking study of saccharin N-triazolyl glycoconjugates.

To achieve better-repurposed motifs, saccharin has been merged with biocompatible sugar molecules via a 1,2,3-triazole linker, and ten novel 1,2,3-triazole-appended saccharin glycoconjugates were developed in good yield by utilizing modular CuAAC click as regioselective triazole forming tool. The docking study indicated that the resulting hybrid molecules have an overall substantial interaction with the CAXII macromolecule. Moreover, the galactose triazolyl saccharin analogue 3h has a binding energy of -8.5 kcal/mol with 5 H-bonds, and xylosyl 1,2,3-triazolyl saccharin analogue 3d has a binding energy of -8.2 kcal/mol with 6 H-bond interactions and have exhibited the highest binding interaction with the macromolecule system.