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A series of phosphinecopper(i) thiocarboxylates have been synthesized and characterized structurally. These complexes act as efficient catalysts for the 'click' azide–alkyne cycloaddition leading to glycoconjugates and a glycocluster.

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

d-Glucosamine, a natural, inexpensive, and conveniently accessible sugar, has been explored as an efficient ligand for the Cu(I)-catalyzed regio- and stereoselective synthesis of an array of (Z)-3-methyleneisoindoline-1-ones and (E)-N-aryl-4H-thiochromen-4-imines in good-to-excellent yield in a tandem fashion via the reaction of 2-halobenzamide and 2-halobenzothioamide with terminal alkynes, respectively. The water solubility and biocompatible nature of the ligand offer easy separation of the catalytic system toward the aqueous phase as well as change in the reaction path in terms of the product also demonstrated the variation of the reaction temperature. The domino reaction proceeds by the Sonogashira and Ullmann type cross-coupling reaction, followed by Cu(I)-promoted additive cyclization of heteroatom to the triple bond. In addition, d-glucosamine causes successful Glaser-Hay coupling of terminal alkynes under Cu catalysis to produce a high yield of respective 1,3-diynes.

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.

A diverse range of ureas, N-acylureas, carbamates, and thiocarbamates has been synthesized in good to excellent yields by reacting N-acylbenzotriazoles individually with amines or amides or phenols or thiols in the presence of diphenylphosphoryl azide (DPPA) as a suitable azide donor in anhydrous toluene at 110 °C for 3–4 hours. In this route, DPPA was found to be a good alternative to trimethylsilyl azide and sodium azide for the azide donor in Curtius degradation. The high reaction yields, one-pot and metal-free conditions, straightforward nature, easy handling, use of readily available reagents, and in many cases avoidance of column chromatography are the notable features of the devised protocol.

Calixarenes with their three-dimensional structural architecture and ease of functionalization at the upper and/or lower rim are well-known for their plethora of applications in chemical, physical, biological and other disciplines. Herein, CuAAC click inspired p-tert-butylcalix[4]arene tethered benzotriazolyl dendrimers, for example, N-1, N-2 type 2-fold compound 6 and 7 ‘G(0)’ and 6-fold compound 16 and 17 ‘G(1)’ generation benzotriazolyl dendrimer, were devised and also evaluated for their therapeutic potential both in vitro and in vivo. The developed calix[4]arene tethered benzotriazolyl dendrimers have been characterized by standard spectroscopic analysis including NMR (1H and 13C), MS, and SEC. Among all the benzotriazolyl dendrimers developed, compound 7 was identified as the effective one which provided potential anti-bacterial and anti-biofilm activities against drug-resistant and slime producing organisms without imparting cytotoxicity to the eukaryotic systems.

The primary motive behind this article is to bring to the forefront a unique kind of dendrimer which has remained a dark horse since its discovery, namely dentromer. We herein report the synthesis of glycodendrimers and glycodentromers crowned with galactose units by harnessing an expeditious synthesis of dendrimer core 18 and dentromer core 19, divergently with branching directionality (1 → 2) and (1 → 3), respectively. A competent, double stage convergent synthetic path was chosen to facilitate ease of refining and spectroscopic elucidations. By exploiting a Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction strategy, we successfully developed a new series of galactosylated dendrimers 20, 21, 22, and 24 containing 6, 12, 18, and 18 peripheral galactose units, respectively. We are first to report the practical synthesis of 9-peripheral galactose coated glycodentromer 23 (0th generation) and 27-peripheral galactose coated glycodentromer 25 (1st generation). These synthesized scaffolds were characterized by spectral studies such as 1H, 13C NMR, FT-IR, MALDI-TOF MS, HRMS and SEC analysis. Additionally, gel permeation chromatography depicted the regular progression in size from 6 to 27-peripheral galactose coated glycodendrimers along with glycodentromers, with their high monodispersity. Also, the glyco-dendrimers and dentromers synthesized from two different hypercore units i.e. dendrimers core (18) and dentromer core (19), have been supported by their UV-visible absorbance and emission spectroscopy.

Tuberculosis, a disease of poverty is a communicable infection with a reasonably high mortality rate worldwide. 10 Million new cases of TB were reported with approx 1.4 million deaths in the year 2019. Due to the growing number of drug-sensitive and drug-resistant tuberculosis cases, there is a vital need to develop new and effective candidates useful to combat this deadly disease. Despite tremendous efforts to identify a mechanism-based novel antitubercular agent, only a few have entered into clinical trials in the last six decades. In recent years, triazoles have been well explored as the most valuable scaffolds in drug discovery and development. Triazole framework possesses favorable properties like hydrogen bonding, moderate dipole moment, enhanced water solubility, and also the ability to bind effectively with biomolecular targets of M. tuberculosis and therefore this scaffold displayed excellent potency against TB. This review is an endeavor to summarize an up-to-date innovation of triazole-appended hybrids during the last 10 years having potential in vitro and in vivo antitubercular activity with structure activity relationship analysis. This review may help medicinal chemists to explore the triazole scaffolds for the rational design of potent drug candidates having better efficacy, improved selectivity and minimal toxicity so that these hybrid NCEs can effectively be explored as potential lead to fight against M. tuberculosis.

Glycodendrimers are receiving considerable attention to mimic a number of imperative features of cell surface glycoconjugate and acquired excellent relevance to a wide domain of investigations including medicine, pharmaceutics, catalysis, nanotechnology, carbohydrate-protein interaction, and moreover in drug delivery systems. Toward this end, an expeditious, modular, and regioselective triazole-forming CuAAC click approach along with double stage convergent synthetic method was chosen to develop a variety of novel chlorine-containing cyclen cored glycodendrimers of high sugar tethers at low generation of promising therapeutic potential. We developed a novel chlorine-containing hypercore unit with 12 alkynyl functionality originated from cyclen scaffold which was confirmed by its single crystal X-ray data analysis. Further, the modular CuAAC technique was utilized to produce a variety of novel 12–sugar coated (G0) glycodendrimers 12-15 adorn with β-Glc-, β-Man-, β-Gal-, β-Lac, along with 36-galactose coated (G1) glycodendrimer 18 in good-to-high yield. The structures of the developed glycodendrimer architectures have been well elucidated by extensive spectral analysis including NMR (1H & 13CNMR), HRMS, MALDI-TOF MS, UV–Vis, IR, and SEC (Size Exclusion Chromatogram) data.

Recent advances in high-throughput, automated techniques combined with the identification of new therapeutic targets in genome sequencing and molecular biology have generated a need for a large collection of diverse heterocyclic scaffolds. This inspires toward the development of novel reaction sequences and linking strategies to generate libraries of diverse simple to complex heterocyclic systems. In this regard, combinatorial chemistry has emerged as an excellent technology platform for the rapid assembly of building blocks to synthesize complex molecular structures with great ease in a few synthetic steps. By means of the implementation of high-throughput screening for the biological evaluation of hits and leads, combinatorial libraries have become important assets in drug discovery and development. In the last two decades, the cyclorelease strategy that minimizes the chemical and tethering implications by releasing the intact desired target molecule in the final step of reaction has attracted much attention. Recently, a particular interest is developing in linking strategies, where loading and cleavage steps contribute to the complexity of the target structure rather than only extraneous manipulations. This review summarises the practical and high-yielding approaches of solid phase combinatorial synthesis for diverse high-purity heterocyclic skeletons of pharmacological importance involving the cycloelimination strategy.

The good leaving tendency of the benzotriazole moiety has been exploited for the synthesis of symmetric, unsymmetric, N-acyl, and cyclic ureas in good yields from N-acylbenzotriazoles by treating the latter with various amines in the presence of TMSN3/Et3N in a sealed tube. The salient features of the devised protocol includes the high-yield, mild, metal-free, one-pot reaction conditions, and short reaction time. Furthermore, in many cases, no column chromatography is required for the purification.

Benzotriazole has been established as an efficient ligand in Cu-catalyzed cross-coupling of terminal alkynes to form 1,3-dialkynes using CuI as the catalyst and K2CO3 as the base at room temperature in an open round-bottom flask. The established protocol has the following notable advantages: simple to handle, easy work-up, mild reaction condition, high substrate scope, requirement of less quantity of ligand and also Cu-catalyst, less expensive, and high reaction yield.

Novel heteroleptic dinuclear [Cu2(L)(PPh3)4] (L = 2,6-pyridinedimethyldixanthate L1 1, 1,4-benznedimethyldixanthate L2 2, 1,4-cyclohexanedixanthate L3 3) and mononuclear [Cu(L4)(PPh3)2] 4 (L4 = piperonylxanthate) and [Cu(L5)(dppf)] 5 (L5 = methylxanthate, dppf = 1,1′-bis(diphenylphosphino)ferrocene) complexes have been synthesised and characterised by elemental (C, H, and N) analysis, high resolution mass spectrometry, and IR, UV-vis, 1H, 13C{1H} and 31P{1H} NMR spectroscopy. Single crystal X-ray diffraction revealed S,S-bifunctional coordination of the dixanthate group in dinuclear complexes 1–3 while 4 and 5 are mononuclear. Complexes 1–5 adopt tetrahedral coordination geometry about the copper atom. These precatalysts having two and one copper(I) centres in a single molecule have been applied in copper catalysed azide–alkyne cycloaddition (CuAAC) reactions for the synthesis of a variety of glycoconjugate triazoles using the Click approach. Particularly the dinuclear catalyst 1, formed on the pyridyl linker based dixanthate ligand, displayed outstanding and reusable catalytic activity for this reaction. Full optimization of the reaction conditions demonstrated a noteworthy Click catalytic system with low catalyst loading under mild reaction conditions.

A Cu(I)-catalyzed azide–alkyne 1,3-dipolar cycloaddition reaction (CuAAC) has been utilized for the synthesis of novel glycodendrimers containing a rigid hexapropargyloxy benzene centered core with 6- and 18-peripheral β-D-galactopyranosidic units. Structures of the novel glycodendrimers and intermediates were well elucidated using nuclear magnetic resonance and infrared spectroscopies, matrix assisted laser desorption/ionization mass spectrometry, and size-exclusion chromatography. The therapeutic evaluations of the developed glycodendrimers were investigated and they were found to have good potential as anti-bacterial, anti-biofilm, and anti-tumour agents.

High-sugar-tethered glycodendrimers are a remarkable tool in glycobiology for the investigation of carbohydrate-protein interaction using its multivalency property. An enthralling double-stage convergent synthetic approach was selected to build a novel class of chlorine-containing glucose-coated dendrimers using an efficient click catalyst ‘dinuclear copper(I) thiodiacetate complex.’ In this context, cyclen core was developed through a divergent approach, while the glucodendron was developed via a convergent approach independently. Both azide-alkyne partners were coupled through a modular copper azide-alkyne cycloaddition (CuAAC) strategy to afford a high yield of the desired 36-glucose-coated glycodendrimer. The synthesized glycodendrimer has been elucidated by NMR, gel permeation chromatography (GPC), and IR spectral analysis.

More than two decades have passed with the glorified research works in the field of ionic liquids (ILs), and the explorartion is still counting by varying research groups across the world. ILs find versatile applications in organic synthesis as solvents, reaction media, and catalysts. The eye-catching advantages of ILs include easy handling, green approach, adjustable-desired physico-chemical properties, and versatile applications in preestablished reactions with much more cost-effective manner. Applications of ILs in developing suitable protocols for the syntheses of different heterocyclic skeletons have been explored with much positivity in the recent past. Among heterocycles, particularly five- and six-membered heterocycles are in the lime-light of medicinal chemistry for pharmacological activities and investigations. This chapter focuses on the properties and wide-spread applications of versatile ILs in the syntheses of heterocyclic scaffolds of promising pharmacological potential.

Among all the malaria parasites, P. falciparum is the most predominant species which has developed drug resistance against most of the commercial anti-malarial drugs. Thus, finding a new molecule for the inhibition of enzymes of P. falciparum is the pharmacological challenge in present era. Herein, ten novel molecules have been designed with an amalgamation of cinchonidine, carbohydrate moiety and triazole ring by utilizing copper-catalyzed click reaction of cinchonidine-derived azide and clickable glycosyl alkynes. The molecular docking of developed molecules showed promising results for plasmepsin inhibition in the form of effective binding with target proteins.

The upsurge of multidrug resistant bacterial infections with declining pipeline of newer antibiotics has made it imperative to develop newer molecules or tailor the existing molecules for more effective antimicrobial therapies. Since antiquity, the use of curcumin, in the form of Curcuma longa paste, to treat infectious lesions is unperturbed despite its grave limitations like instability and aqueous insolubility. Here, we utilized “click” chemistry to address both the issues along with improvisation of its antibacterial and antibiofilm profile. We show that soluble curcumin disrupts several bacterial cellular processes leading to the Fenton’s chemistry mediated increased production of reactive oxygen species and increased membrane permeability of both Gram-positive and Gram-negative bacteria. We here report that its ability to induce oxidative stress can be harnessed to potentiate activities of ciprofloxacin, meropenem, and vancomycin. In addition, we demonstrated that the soluble curcumin reported herein even sensitizes resistant Gram-negative clinical isolates to the Gram-positive specific antibiotic vancomycin, thereby expanding the antibacterial spectrum of this drug. This work shows that the soluble curcumin can be used to enhance the action of existing antimicrobials against both Gram-positive and Gram-negative bacteria thus strengthening the antibiotic arsenal for fighting resistant bacterial infections for many years to come.

In nature, all cells are covered with a complex array of carbohydrates particularly sialic acids which is chemically a negatively charged nine-carbon α-keto aldonic acids. Because of their significant role on cell surfaces, the sialic acid-containing glycans certainly can mediate and modulate many important cellular interactions. Further, proteins having receptors to bind sialic acids are recognized to be involved in a wide variety of biological processes. Thus evaluation of carbohydrate-protein interaction and further their roles in vertebrates may results in enhanced understanding of normal physiology, pathological variance and human evolution. This chapter summarizes the structures and biological significance of sialic acid, their chemical diversity, biosynthesis followed by chemical modification and enzymatic synthesis of sialic acids, their impact in chemical biology, and also the neurobiology of sialic acid. Conclusively, this chapter highlights the recent advances and challenges at the interface of chemistry and biology of sialic acids in order to find out their scope in drug discovery and development.

A novel path has been developed for the conversion of carboxylic acids into the corresponding N-acylbenzotriazoles by using 2,2′-dipyridyl disulfide/PPh3 in anhydrous dichloromethane in the presence of 1H-benzotriazole. Mild reaction conditions, short reaction time, easy in handling, wide substrate scope, availability of reagents involved, and moreover avoiding the use of base makes this protocol quite useful for the laboratory practices for N-acylbenzotriazole synthesis.

An establishment of (1H-benzo[d][1,2,3]triazol-1-yl)(2-methoxyphenyl)methanone as ligand was attained in intramolecular C-O cross-coupling of N-(2-halophenyl)aryl/alkylamide derivatives to form 2-Aryl/alkyl benzoxazole derivatives using CuI/K2CO3 as catalytic system. A series of benzoxazoles was developed using this protocol and synthesized compounds were characterized using spectroscopic analysis (IR, MS, 1H & 13C NMR). Salient advantages associated with this pathway include easily available starting materials, cheap catalyst, highly stable ligand, wide substrate scope, smooth reaction, easy work-up and high product yield.

Glycosyl triazoles are conveniently accessible and contain multiple metal-binding units that may assist in metal-mediated catalysis. Azide derivatives of d-glucose have been converted to their respective aryltriazoles and screened as ligands for the synthesis of 2-substituted benz-fused azoles and benzimidazoquinazolinones by Cu-catalyzed intramolecular Ullmann type C-heteroatom coupling. Good to excellent yields for a variety of benz-fused heterocyles were obtained for this readily accessible catalytic system.

A controlled and facile synthesis of various glycosyl 1,3-oxazolidine-2-thiones and 1,3- thiozolidine-2-thiones has been accomplished from corresponding sugar azido alcohols utilizing Staudinger reaction (PPh3 and CS2) via isothiocynate route. A series of reactions were performed to investigate the effects of CS2 and PPh3 on the selectivity of product formed. The excessive addition of CS2 with PPh3(1.2 equiv) afforded oxazolidine-2-thione alone, while the solitary addition of PPh3 for 30 min followed by addition of CS2 to the reaction mixture resulted both the products in different ratios, which were successfully isolated using column chromatography (SiO2). Furthermore, synthesis of 1,3-oxathiolan-2-imine from glycosyl epoxide has also been attempted. Structures of all the developed compounds have been elucidated using extensive spectroscopic techniques including IR, NMR and MS analysis.