Validation of the Copper(I)-Catalyzed Azide−Alkyne Coupling in Ionic Liquids. Synthesis of a Triazole-Linked C-Disaccharide as a Case Study

1,5-disubstituted 1,2,3-triazolylated carbohydrates and nucleosides

In general, 1,5-disubstituted 1,2,3-triazolyl moiety is much less common in the synthesis and applications in comparison to its regioisomeric counterpart. Moreover, the synthesis of 1,5-disubstituted 1,2,3-triazoles are not so straightforward as is the case for copper catalyzed strategy of 1,4-disubstituted 1,2,3-triazoles. The preparation of 1,5-triazolylated carbohydrates and nucleosides are even more complex because of the difficulties in accessing the appropriate starting materials as well as the compatibility of reaction conditions with the various protecting groups. 1,5-Disubstitution regioisomeric triazoles of carbohydrates and nucleosides were traditionally obtained as minor products through straightforward heating of the mixture of azides and terminal alkynes. However, the separation of isomers was tedious or in some cases futile. On the other hand, regioselective synthesis using ruthenium catalysis triggered serious concern of residual metal content in therapeutically important ingredients. Therefore, serious efforts are being made by several groups to develop non-toxic metal based or completely metal-free synthesis of 1,5-disubstituted 1,2,3-triazoles. This article strives to summarize the pre-Click era as well as the post-2001 reports on the synthesis and potential applications of 1,5-disubstituted 1,2,3-triazoles in biological systems.

A kinetics study of copper-catalysed click reactions in ionic liquids

Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions are of extensive interest in chemical synthesis. While the use of ionic liquids (ILs) as solvents for synthesis has been widely explored in recent years, the understanding of their influence on the mechanism and reactivity of CuAAC reactions remains poorly understood. Here, we investigate the kinetics of a phenylacetylene-benzylazide and acetylene-benzylazide CuAAC reaction to probe the influence of IL structure, including the role of the base used to promote the reaction and the importance of water content. The use of 'wet' ILs led to remarkable changes in the kinetic profile of the reaction by eliminating the initial induction period. The reaction rate was found to be dependent on the copper(I) source. The effect of an added base was also studied, with the use of a tertiary amine-bearing IL leading to high conversions in under 5 min at ambient temperature. The results of this study highlight the nature and complexity of CuAAC reactions in ILs. As more ILs are getting involved in industrial processes, the data obtained from this study are valuable for better understanding processes that affect the CuAAC reaction in IL media and for creating customized systems for organic synthesis, thus improving the efficiency and sustainability of such processes.

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.

Copper(i)-catalyzed click chemistry in deep eutectic solvent for the syntheses of β-d-glucopyranosyltriazoles

In the last two decades, click chemistry has progressed as a powerful tool in joining two different molecular units to generate fascinating structures with a widespread application in various branch of sciences. copper(i)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, also known as click chemistry, has been extensively utilized as a versatile strategy for the rapid and selective formation of 1,4-disubstituted 1,2,3-triazoles. The successful use of CuAAC reaction for the preparation of biologically active triazole-attached carbohydrate-containing molecular architectures is an emerging area of glycoscience. In this regard, a well-defined copper(i)-iodide complex (1) with a tridentate NNO ligand (L1) was synthesized and effectively utilized as an active catalyst. Instead of using potentially hazardous reaction media such as DCM or toluene, the use of deep eutectic solvent (DES), an emerging class of green solvent, is advantageous for the syntheses of triazole-glycohybrids. The present work shows, for the first time, the successful use of DES as a reaction medium to click various glycosides and terminal alkynes in the presence of sodium azide. Various 1,4-disubstituted 1,2,3-glucopyranosyltriazoles were synthesized and the pure products were isolated by using a very simple work-up process (filtration). The reaction media was recovered and recycled in five consecutive runs. The presented catalytic protocol generated very minimum waste as reflected by a low E-factor (2.21-3.12). Finally, the optimized reaction conditions were evaluated with the CHEM21 green metrics toolkit.

Carboxymethyl tethered poly(disubstituted)triazoles built on nucleoside skeletons: A unique class of ribonuclease A inhibitors designed using chemical logic

Molecular docking of N-1,4-disubstituted-1,2,3-triazole tethered carboxymethylated thymidine and uridine with ribonuclease A, indicated their possible binding with the P₁, B₁ and P₂ subsites with varied efficiencies. This theoretical study in combination of our earlier experimental observations was used as the guiding principles for designing a range of 1,4-disubstituted 1, 2, 3- triazole tethered carboxymethylated pyrimidine nucleosides. Triazoles are biologically important molecules and at the same time easily accessible through less complicated synthetic routes as reported about two decades back in the context of "click" reactions. Regioselective propargylation of the nucleosides under controlled conditions followed by the use of CuAAC strategy afforded mono-, bis-, tris- and tetratriazolyl pyrimidine nucleosides. Although the characteristics of nucleosides were lost in these densely functionalized polyheterocycles, the catalytic efficiency of ribonuclease A was significantly reduced by these molecules which were investigated experimentally and by docking studies. Triazoles as linkers helped one or more acidic groups to reach the P₁ subsite of ribonuclease A. Enzyme kinetics showed that the efficiency of inhibition reached the highest point with an optimum number of functional groups and were not linearly dependent on the number of triazole tethered carboxymethyl groups. The location of the triazole ring in the molecule affected the efficiency and nature of inhibition which were the result of the overall structure of the modified nucleosides. Thus, the tris-triazolylated thymidine derivative (T-3', 5', N-tris-CH₂TzCH₂COOH) as opposed to tetra-triazolylated uridine (U-2', 3', 5', N-tetrakis-CH₂TzCH₂COOH) emerged as the best inhibitor with an inhibition constant value of 2.3 ± 0.05 µM.

Copper-doped functionalized β-cyclodextrin as an efficient green nanocatalyst for synthesis of 1,2,3-triazoles in water

The synthesis of 1,2,3-triazoles with immobilized Cu(I) in thiosemicarbazide-functionalized β-cyclodextrin (Cu@TSC-β-CD) as a supramolecular catalyst was discussed. The catalyst was characterized by Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) measurements. The catalyst showed high activity (up to 95% yields of triazole products under optimized reaction conditions), providing a one-pot, atom-economic, and highly regioselective green method for 1,2,3-triazoles synthesis in an azide-alkyne cycloaddition (AAC) protocol in water. High stability and no appreciable leaching of Cu(I) were observed, owing to its strong binding via the coordination with thiosemicarbazide functionality.

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.

Synthesis of Glycodendrimers with Antiviral and Antibacterial Activity

Glycodendrimers are an important class of synthetic macromolecules that can be used to mimic many structural and functional features of cell-surface glycoconjugates. Their carbohydrate moieties perform key important functions in bacterial and viral infections, often regulated by carbohydrate-protein interactions. Several studies have shown that the molecular structure, valency and spatial organisation of carbohydrate epitopes in glycoconjugates are key factors in the specificity and avidity of carbohydrate-protein interactions. Choosing the right glycodendrimers almost always helps to interfere with such interactions and blocks bacterial or viral adhesion and entry into host cells as an effective strategy to inhibit bacterial or viral infections. Herein, the state of the art in the design and synthesis of glycodendrimers employed for the development of anti-adhesion therapy against bacterial and viral infections is described.

A Simple Work-Up-free, Solvent-free Approach to Novel Amino Acid Linked 1,4-Disubstituted 1,2,3-Triazoles as Potent Antituberculosis Agents

An efficient, green strategy for synthesis of 1,4-disubstituted-1,2,3-triazole has been developed using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) acetate ionic liquid (200 μL) under a solvent- and external base-free condition. This protocol is further applied for the synthesis of novel amino acid containing 1,2,3-triazole molecules, which were then evaluated for potential antitubercular and antibacterial activities. Cytotoxicity assay of the compounds was also performed. In silico analysis of the promising compounds selected through experimental analysis was thereafter performed for visualizing molecular interactions and predicting binding affinities between our synthesized molecules, which exhibited good activity in experimental studies and the DprE1 target protein of Mycobacterium tuberculosis. Durg-likeness studies also show potential of the synthesized molecules as drug candidates.

Synthesis of Dihydropyrimidinones (DHPMs) and Hexahydro Xanthene Catalyzed by 1,4-Diazabicyclo [2.2.2] Octane Triflate Under Solvent-Free Condition

OBJECTIVE

DABCO salts were evaluated as catalysts for the Biginelli reaction between 4- methoxybenzaldehyde, urea and ethyl acetoacetate under solvent-free conditions. 1,4-Diazabicyclo [2.2.2] octane triflate was found to be a simple, inexpensive, highly efficient catalyst for Biginelli reaction for a variety aromatic aldehyde with urea and ethyl acetoacetate at 80°C afforded corresponding 3,4-dihydropyrimidinones in 50-99% yields after 30-120 minutes. 1,3-Cyclohexadione was used in place of ethyl acetoacetate in the absence of urea this methodology is giving hexahydro xanthene derivatives in good to excellent yields after 3-4 hours.

METHODS

DABCO salt 4 (5 mol%), 4-methoxybenzaldehyde (0.73 mmol) and urea (0.73 mmol) were stirred for 10 minutes at 80°C, then ethyl acetoacetate (1.5 equiv.) was added and reaction mixture was stirred at 80°C for specified time. The resulting solution was stirred continuously and progress of the reaction was followed by TLC. The crude reaction mixture was purified by flash column chromatography on silica gel (hexane/ethyl acetate (1:2)) to give pure desired product.

RESULTS

Reaction conditions of the Biginelli reaction were optimized using 4-methoxybenzaldehyde (0.73 mmol), urea (0.73 mmol), and ethyl acetoacetate (5 equiv.) as model substrates catalyzed by 1,4-Diazabicyclo [2.2.2] octane triflate (5 mol%) in a different solvents, screening of different catalysts and different temperatures. Neat condition was found to be the best for the Biginelli condensation and corresponding 3,4- dihydropyrimidinones was obtained in good to excellent yields. When the reaction was carried out with benzaldehyde derivatives and cyclohexane-1,3-dione in place of ethyl acetoacetate in the absence of urea, solely corresponding hexahydro xanthene derivatives were obtained in 61-91% yields.

CONCLUSION

In conclusion, we have applied salts of 1,4-Diaza-bicyclo [2.2.2] octane as catalysts in the Biginelli condensation and corresponding 3,4-dihydropyrimidinones were obtained in 50- 99% yields under solvent free conditions. This methodology is having advantages like simple work-up; low loading of catalyst and reaction was performed at moderate temperature under solvent-free conditions.

Mesoporous PbO nanoparticle-catalyzed synthesis of arylbenzodioxy xanthenedione scaffolds under solvent-free conditions in a ball mill

A protocol for the efficient synthesis of arylbenzodioxy xanthenedione scaffolds was developed via a one-pot multi-component reaction of aromatic aldehydes, 2-hydroxy-1,4-naphthoquinone, and 3,4-methylenedioxy phenol using mesoporous PbO nanoparticles (NPs) as a catalyst under ball milling conditions. The synthesis protocol offers outstanding advantages, including short reaction time (60 min), excellent yields of the products (92-97%), solvent-free conditions, use of mild and reusable PbO NPs as a catalyst, simple purification of the products by recrystallization, and finally, the use of a green process of dry ball milling.

New N-phenylacetamide-incorporated 1,2,3-triazoles: [Et3NH][OAc]-mediated efficient synthesis and biological evaluation

A facile, highly efficient, and greener method for the synthesis of new 1,4-disubstituted-1,2,3-triazoles was conducted using [Et3NH][OAc] as a medium by the implementation of ultrasound irradiation via click chemistry, affording excellent yields. The present synthetic method exhibited numerous advantages such as mild reaction conditions, excellent product yields, minimal chemical waste, operational simplicity, shorter reaction time, and a wide range of substrate scope. The synthesized compounds were further evaluated for in vitro antifungal activity against five fungal strains, and some of the compounds displayed equivalent or greater potency than the standard drug. A molecular docking study against the modelled three-dimensional structure of cytochrome P450 lanosterol 14α-demethylase was also performed to understand the binding affinity and binding interactions of the enzyme. Furthermore, the synthesized compounds were evaluated for DPPH radical scavenging activity and antitubercular activity against Mycobacterium tuberculosis H37Rv strain.

Synthesis and optical properties of novel 1,2,3-triazole derivatives possessing highly substituted imidazoles

Reactions of 1,4,5-triaryl-2-(4-bromomethyl)phenyl-imidazoles with sodium azide in acetone give the corresponding azidomethyl derivatives, which on 1,3-dipolar cycloaddition with various terminal alkynes in the presence of CuI afford novel 1,2,3-triazole products. On the other hand, treatment of 2,4,5-triaryl-1-(4-hydroxyphenyl)-imidazoles with propargyl chloride in the presence of a base gives the corresponding propargyl ether derivatives, which under CuI-catalyzed 1,3-dipolar cycloaddition with benzyl azide produce 1,2,3-triazole derivatives. All the products are characterized from their spectroscopic data and most are evaluated for fluorescence emission. The optical parameters of the studied products are also reported.

Dehydroascorbic Acid and pGPMA Dual Modified pH-Sensitive Polymeric Micelles for Target Treatment of Liver Cancer

In clinical therapy, the poor prognosis of hepatocellular carcinoma (HCC) is mainly attributed to the failure of chemotherapeutical agents to accumulate in tumor as well as lack of potency of tumor penetration. In this work, we developed actively tumor-targeting micelles with pH-sensitive linker as a novel nanocarrier for HCC therapy. These micelles comprised biodegradable poly(ethylene glycol)-poly(aspartate) polymers, in which paclitaxel can be covalently conjugated to pAsp via an acid-labile acetal bond to form pH-responsive structures. In vitro drug release studies showed that these structures were stable in physiological condition, whereas collapsed once internalized into cells due to the mildly acidic environment in endo/lysosomes, resulting in facilitated intracellular paclitaxel release. In addition, dehydroascorbic acid and guanidinopropyl methacrylamide polymers were decorated on the surface of micelles to achieve specific tumor accumulation and tumor penetration. Cellular uptake and in vivo imaging studies proved that these micelles had remarkable targeting property toward hepatocarcinoma cells and tumor. Enhanced anti-HCC efficacy of the micelles was also confirmed both in vitro and in vivo. Therefore, this micellar system may be a potential platform of chemotherapeutics delivery for HCC therapy.

C-Glycopyranosyl Arenes and Hetarenes: Synthetic Methods and Bioactivity Focused on Antidiabetic Potential

This Review summarizes close to 500 primary publications and surveys published since 2000 about the syntheses and diverse bioactivities of C-glycopyranosyl (het)arenes. A classification of the preparative routes to these synthetic targets according to methodologies and compound categories is provided. Several of these compounds, regardless of their natural or synthetic origin, display antidiabetic properties due to enzyme inhibition (glycogen phosphorylase, protein tyrosine phosphatase 1B) or by inhibiting renal sodium-dependent glucose cotransporter 2 (SGLT2). The latter class of synthetic inhibitors, very recently approved as antihyperglycemic drugs, opens new perspectives in the pharmacological treatment of type 2 diabetes. Various compounds with the C-glycopyranosyl (het)arene motif were subjected to biological studies displaying among others antioxidant, antiviral, antibiotic, antiadhesive, cytotoxic, and glycoenzyme inhibitory effects.

An ionic liquid promoted approach to bitriazolyl compounds as succinate–ubiquinone oxidoreductase inhibitors

Bitriazolyl compounds, a novel skeleton that is totally different from existing commercialized SQR-inhibiting fungicides, could provide a new lead for further development of SQR inhibitors.

Synthesis of glucopyranos-6′-yl purine and pyrimidine isonucleosides as potential cholinesterase inhibitors. Access to pyrimidine-linked pseudodisaccharides through Mitsunobu reaction

The synthesis of new isonucleosides comprising purine and pyrimidine-derived systems linked to methyl glucopyranosidyl units at C-6 and evaluation of their cholinesterase inhibitory profiles is reported. Their access was based on the Mitsunobu coupling of partially acetylated and benzylated methyl glucopyranosides with purine and pyrimidine derivatives. While the reactions with purines and theobromine proceeded with complete regioselectivity, affording exclusively N9- or N1-linked 6′-isonucleosides, respectively, the use of pyrimidine nucleobases led to N1 and/or N3-glucopyranosid-6′-yl pyrimidines and/or to N1,N3/2-O,4-O-pyrimidine-linked pseudodisaccharides through bis-coupling, depending on the substitution pattern of the sugar precursor and on the nature of the nucleobase. From this series of compounds, four were shown to be effective and selective inhibitors of acetylcholinesterase with inhibition constants in the micromolar concentration range. A tri-O-acetylated N1-glucopyranosid-6′-yl theobromine and a benzylated N1,N3-bis-glucopyranosid-6-yl thymine were the most active molecules with Ki values of 4 μM. A tri-O-benzylated glucopyranosid-6′-yl uracil displayed good and selective inhibition of butyrylcholinesterase (Ki=8.4±1.0 μM), similar to that exhibited by the standard galantamine. Molecular docking simulations, performed with the two most effective acetylcholinesterase inhibitors, showed interactions with key amino acid residues located at the enzyme’s active site gorge, which explain the competitive component of their inhibitory activities.

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.

Vinyl sulfone modified-azidofuranoside building-blocks: 1,4-/1,5-disubstituted-1,2,3-triazole linked trisaccharides via an aqueous/ionic-liquid route and “Click” chemistry

1,5-Disubstituted 1,2,3-triazole (1,5-DT) linked disaccharides have been synthesized from stable building blocks having both vinyl sulfone and azido groups using aqueous ionic-liquid media.

Direct access to stabilized CuI using cuttlebone as a natural-reducing support for efficient CuAAC click reactions in water

Cuttlebone@CuCl₂ as a highly active, versatile, and green heterogeneous catalyst was investigated for the efficient preparation of 1,4-disubstituted 1,2,3-triazoles through the one-pot Huisgen 1,3-dipolar cycloaddition reaction in water.

Copper-catalysed azide-alkyne cycloadditions (CuAAC): an update

The reactions of organic azides and alkynes catalysed by copper species represent the prototypical examples of click chemistry. The so-called CuAAC reaction (copper-catalysed azide-alkyne cycloaddition), discovered in 2002, has been expanded since then to become an excellent tool in organic synthesis. In this contribution the recent results described in the literature since 2010 are reviewed, classified according to the nature of the catalyst precursor: copper(I) or copper(II) salts or complexes, metallic or nano-particulated copper and several solid-supported copper systems.

Cell microenvironment-controlled antitumor drug releasing-nanomicelles for GLUT1-targeting hepatocellular carcinoma therapy

In clinical therapy, the poor prognosis of hepatocellular carcinoma (HCC) is mainly attributed to the failure of chemotherapeutical agents to accumulate in tumor as well as their serious systemic toxicity. In this work, we developed actively tumor-targeting trilayer micelles with microenvironment-sensitive cross-links as a novel nanocarrier for HCC therapy. These micelles comprised biodegradable PEG-pLys-pPhe polymers, in which pLys could react with a disulfide-containing agent to form redox-responsive cross-links. In vitro drug release and pharmacokinetics studies showed that these cross-links were stable in physiological condition whereas cleaved once internalized into cells due to the high level of glutathione, resulting in facilitated intracellular doxorubicin release. In addition, dehydroascorbic acid (DHAA) was decorated on the surface of micelles for specific recognition of tumor cells via GLUT1, a member of glucose transporter family overexpressed on hepatocarcinoma cells. Moreover, DHAA exhibited a "one-way" continuous accumulation within tumor cells. Cellular uptake and in vivo imaging studies proved that these micelles had remarkable targeting property toward hepatocarcinoma cells and tumor. Enhanced anti-HCC efficacy of the micelles was also confirmed both in vitro and in vivo. Therefore, this micellar system may be a potential platform of chemotherapeutics delivery for HCC therapy.

The ultrasounds-ionic liquids synergy on the copper catalyzed azide-alkyne cycloaddition between phenylacetylene and 4-azidoquinoline

The effect of ultrasound irradiation on the copper catalyzed azide-alkyne cycloaddition between phenylacetylene and 4-azidoquinoline has been studied in solution of different ionic liquids. In particular, we used ionic liquids featuring both aliphatic and aromatic mono- and dications, as well as anions differing in size, symmetry and coordination ability. We also examined the influence of the ionic liquids structural features on the reaction outcomes, finding that under magnetic stirring reactivity is favorably affected by the solvent structural organization, while under sonochemical conditions an opposite trend was observed. In all cases examined, sonochemical activation leads to significant reduction in energy consumption as compared to the reaction conducted under magnetic stirring.

Synthesis of functionalized 1,2,3-triazoles using Bi2WO6 nanoparticles as efficient and reusable heterogeneous catalyst in aqueous medium

The regioselective synthesis of functionalized triazoles is achieved using a combination of Bi₂WO₆ nanoparticles (10 mol%) and click conditions from β-nitrostyrenes, phenylacetylene and chalcones with azides.

2-Pyrrolecarbaldiminato–Cu(ii) complex catalyzed three-component 1,3-dipolar cycloaddition for 1,4-disubstituted 1,2,3-triazoles synthesis in water at room temperature

2-Pyrrolecarbaldiminato–Cu(ii) complexes were first established as efficient catalyst for 1,4-disubstituted 1,2,3-triazoles synthesis under green and mild reaction conditions.

Efficient and selective azidation of per-O-acetylated sugars using ultrasound activation: application to the one-pot synthesis of 1,2,3-triazole glycosides

A new protocol was developed for the selective transformation of acetyl-sugars to triazolyl nucleosides using in situ generated SO₂(N₃)₂, iron/copper cocatalysis and ultrasound activation.

Regioselectivity of vinyl sulfone based 1,3-dipolar cycloaddition reactions with sugar azides by computational and experimental studies

DFT (M06-L) calculations on the transition state for the 1,3-dipolar cycloadditions between substituted vinyl sulfones with sugar azide have been reported in conjunction with new experimental results, and the origin of reversal of regioselectivity has been revealed using a distortion/interaction model. This study provides the scientific justification for combining organic azides with two different types of vinyl sulfones for the preparation of 1,5-disubstituted 1,2,3-triazoles and 1,4-disubstituted triazolyl esters under metal-free conditions.

Smart nanodevice combined tumor-specific vector with cellular microenvironment-triggered property for highly effective antiglioma therapy

Malignant glioma, a highly aggressive tumor, is one of the deadliest types of cancer associated with dismal outcome despite optimal chemotherapeutic regimens. One explanation for this is the failure of most chemotherapeutics to accumulate in the tumors, additionally causing serious side effects in periphery. To solve these problems, we sought to develop a smart therapeutic nanodevice with cooperative dual characteristics of high tumor-targeting ability and selectively controlling drug deposition in tumor cells. This nanodevice was fabricated with a cross-linker, containing disulfide linkage to form an inner cellular microenvironment-responsive "-S-S-" barrier, which could shield the entrapped drug leaking in blood circulation. In addition, dehydroascorbic acid (DHA), a novel small molecular tumor-specific vector, was decorated on the nanodevice for tumor-specific recognition via GLUT1, a glucose transporter highly expressed on tumor cells. The drug-loaded nanodevice was supposed to maintain high integrity in the bloodstream and increasingly to specifically bind with tumor cells through the association of DHA with GLUT1. Once within the tumor cells, the drug release was triggered by a high level of intracellular glutathione. When these two features were combined, the smart nanodevice could markedly improve the drug tumor-targeting delivery efficiency, meanwhile decreasing systemic toxicity. Herein, this smart nanodevice showed promising potential as a powerful platform for highly effective antiglioma treatment.