Synthesis of novel multidentate carbohydrate-triazole ligands

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 biological evaluation of 1,8-naphthyridine glucosamine conjugates as antimicrobial agents

In the quest for discovering potent antimicrobial agents with lower toxicity, we envisioned the design and synthesis of nalidixic acid-D-(+)-glucosamine conjugates. The novel compounds were synthesized and evaluated for their in vitro antimicrobial activity against Gram positive bacteria, Gram negative bacteria and fungi. Cytotoxicity using MTT assay over L6 skeletal myoblast cell line, ATCC CRL-1458 was carried out. In vitro antimicrobial assay revealed that 1-ethyl-7-methyl-4-oxo-N-(1,3,4,6-tetra-O-acetyl-2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide (5) and 1-ethyl-7-methyl-4-oxo-N-(2-deoxy-D-glucopyranose-2-yl)-[1,8]-naphthyridine-3-carboxamide(6) possess growth inhibitory activity against resistant Escherichia coli NCTC, 11954 (MIC 0.1589 mM) and Methicillin resistant Staphylococcus aureus ATCC, 33591 (MIC 0.1589 mM). Compound (5) was more active against Listeria monocytogenes ATCC 19115 (MIC 0.1113 mM) in comparison with the reference nalidixic acid (MIC 1.0765 mM). Interestingly, compound (6) had potential antifungal activity against Candida albicans ATCC 10231 (MIC <0.0099 mM). Remarkably, the tested compounds had low cytotoxic effect. This study indicated that glucosamine moiety inclusion into the chemical structure of the marketed nalidixic acid enhances antimicrobial activity and safety.

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.

Complexes of (η6-benzene)ruthenium(ii) with 1,4-bis(phenylthio/seleno-methyl)-1,2,3-triazoles: synthesis, structure and applications in catalytic activation of oxidation and transfer hydrogenation

1,4-Bis(phenylthio/seleno methyl)-1,2,3-triazoles (L1–L4) synthesized by a ‘Click’ reaction form complexes [(η⁶-C₆H₆)RuClL]PF₆ (L = L1–L4) suitable as catalyst for oxidation/transfer hydrogenation.

Copper(ii) complexes supported by click generated mixed NN, NO, and NS 1,2,3-triazole based ligands and their catalytic activity in azide–alkyne cycloaddition

Four copper complexes supported by mixed NO, NN and NS-1,2,3-triazoles are reported. Their catalytic activity in the CuAAC process is demonstrated.

Solid-Phase Synthesis of 2-Aminoethyl Glucosamine Sulfoforms

Mono- and disaccharides of sulfonated glucosamines (GlcN sulfoforms) conjugated to 2-aminoethyl linkers were generated by solid-phase synthesis. Orthogonally protected intermediates were tethered onto tritylated polystyrene resin beads, subjected to a modular sequence of deprotection and sulfonation steps, then cleaved from solid support without degradation of N- or O-sulfate esters using solvolytic conditions, and finally purified by reverse-phase HPLC to afford the title compounds.

Sulfoform generation from an orthogonally protected disaccharide

An orthogonally protected disaccharide (GlcN(α1→4)Glc) with a β-linked 2'-aminoethyl linker was used to generate a series of sulfated derivatives (sulfoforms), with a 6-O-sulfate on the glucose residue and one or more sulfate esters on the terminal glucosamine. Deprotection and sulfonation steps were performed in solution and in variable order, with isolated yields of 36-54% (85-90% per operation) after HPLC purification. The modular deprotection-sulfonation sequences can be performed with efficient recovery of the polysulfate products, and avoids complications associated with heterogeneous reactivity in solid-phase synthesis.

Metal chelating systems synthesized using the copper(I) catalyzed azide-alkyne cycloaddition

The copper(I) catalyzed azide-alkyne cycloaddition (CuAAC) is the premier example of a click reaction. The reaction is modular, reliable and easy to perform, providing easy access to molecular diversity. The majority of reported applications of the reaction employ the 1,2,3-triazole as a stable linkage to connect two chemical/biological components, while the potential for metal coordination of the heterocycle itself has received much less attention. In fact, 1,4-functionalized 1,2,3-triazoles are versatile ligands offering several donor sites for metal coordination, including N3, N2 and C5. In this article, we summarize the areas in which the CuAAC has been applied to the synthesis of novel triazole-containing ligands for transition metals.

A multicomponent CuAAC "click" approach to a library of hybrid polydentate 2-pyridyl-1,2,3-triazole ligands: new building blocks for the generation of metallosupramolecular architectures

A one pot, multicomponent CuAAC reaction has been exploited for the safe generation of alkyl, benzyl or aryl linked polydentate pyridyl-1,2,3-triazole ligands from their corresponding halides, sodium azide and alkynes in excellent yields. The ligands have been fully characterised by elemental analysis, HR-ESMS, IR, (1)H and (13)C NMR and in two cases the structures were confirmed by X-ray crystallography. Additionally, we have examined the Ag(I) coordination chemistry of these ligands and found, using HR-ESMS, (1)H NMR, and X-ray crystallography, that both discrete and polymeric metallosupramolecular architectures can be formed.

Dimerization of propargyl and homopropargyl 6-azido-6-deoxy-glycosides upon 1,3-dipolar cycloaddition

Copper-catalyzed, thermal or microwave promoted 1,3-dipolar cycloaddition (Click Reaction) of 2-propynyl and 3-butynyl 2,3,4-tri-O-acetyl-6-azido-6-deoxy-glycopyranosides in the D-gluco, D-galacto and D-manno series afford the corresponding dimeric cycloaddition products.