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.

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.

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.

First report of molecular confirmation and phylogenetic analysis of ocular seteriasis in buffalo in India using 12S rRNA

An adult Indian buffalo (Bubalus bubalis) presented with corneal opacity, irritation, and excessive lacrimation from the left eye in the Referral Veterinary Polyclinic-Teaching Veterinary Clinical Complex (RVC-TVCC), Indian Veterinary Research Institute, Izatnagar. Clinical examination revealed a whitish thread-like worm in the left eye's anterior chamber. The worm was surgically removed from the eye with supportive nerve blocks. Light microscopy was used for parasite morphological identification, which provided insight into the worm as female Setaria sp. Genomic DNA was isolated, and polymerase chain reaction amplification of 12S rRNA was conducted for molecular confirmation of the parasite. The amplicon was sequenced and analysed by bioinformatics software. Sequence data showed an amplicon size of 243 bp. Phylogenetic analysis with reference data from the NCBI Genbank database revealed the worm was S. digitata, with a similarity of 99.17%. The common predilection site of S. digitata is in the peritoneal cavity of natural hosts like cattle and buffalo and is mostly non-pathogenic. The aberrant migration of the parasite larva to the brain and eye commonly occurs in goats, sheep, and horses, causing clinical conditions like cerebrospinal nematodiasis (lumbar paralysis) and ocular setariasis, respectively. Nevertheless, until now, there have been no reports of ocular setariasis in buffalo. This report is the first unusual occurrence of ocular setariasis in buffalo and its molecular confirmation and phylogenetic analysis using 12S rRNA.

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.

Click inspired synthesis of piperazine-triazolyl sugar-conjugates as potent anti-Hela activity

To imbibe the aim of synthesizing water-soluble and biocompatible motif, a click-inspired piperazine glycoconjugate has been devised up. In this report, we present a focused approach to design and synthesis of versatile sugar-appended triazoles through 'Click Chemistry' along with their pharmacological studies on cyclin-dependent kinases (CDKs) and cell cytotoxicity on cancer cells using in silico and in vitro approaches, respectively. The study has inclusively recognized the galactose- and mannose-derived piperazine conjugates as the promising motifs. The findings suggested that the galactosyl bis-triazolyl piperazine analogue 10b is the most CDK interactive derivative and also possess significant anticancer activity.

Growing impact of sialic acid-containing glycans in future drug discovery

In nature, almost all cells are covered with a complex array of glycan chain namely sialic acids or nuraminic acids, a negatively charged nine carbon sugars which is considered for their great therapeutic importance since long back. Owing to its presence at the terminal end of lipid bilayer (commonly known as terminal sugars), the well-defined sialosides or sialoconjugates have served pivotal role on the cell surfaces and thus, the sialic acid-containing glycans can modulate and mediate a number of imperative cellular interactions. Understanding of the sialo-protein interaction and their roles in vertebrates in regard of normal physiology, pathological variance, and evolution has indeed a noteworthy journey in medicine. In this tutorial review, we present a concise overview about the structure, linkages in chemical diversity, biological significance followed by chemical and enzymatic modification/synthesis of sialic acid containing glycans. A more focus is attempted about the recent advances, opportunity, and more over growing impact of sialosides and sialoconjugates in future drug discovery and development.

Synthesis of Calix[4]arene Appended Lactosylated G1 and Galactosylated G2 Generation Glycodendrimers using ‘CuAAC’ click-approach

A modular click-approach is applied for the expeditious synthesis of lactose- and galactose-coated calixarene cored G1 and G2 generation glycodendrimers, respectively. The developed calixarene glycodendrimers has been characterized by using extensive spectral analysis including NMR (1H and 13C), MS, IR and SEC data.

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.

One-pot expeditious synthesis of glycosylated esters through activation of carboxylic acids using trichloroacetonitrile

Acetimidates, a valuable intermediate has been well explored as versatile synthon in a number of organic transformations particularly as suitable donors in glycosylation reactions. Herein, we explored acetimidates to furnish high-to-excellent yield of diverse glycosylated esters under one-pot mild reaction condition. The commercially available trichloroacetonitrile is implemented for the activation of carboxylic acid via in situ generation of trichloroacetimidate, which was subsequently attacked by sugar alcohols to deliver high-to-excellent yields of desired glycosylated esters. The devised method has some notable features such as metal-free condition, one-pot mild reaction condition, easy-handling, high-to-excellent yields, and broad substrate scope.

Synthesis and structural features of a series of Cu(i) furan-2-thiocarboxylate complexes: efficient “click” catalysts for the synthesis of glycoconjugates and glycocluster

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 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.

Room-Temperature Ionic Liquids in Glycoscience: Opportunities and Challenges#

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Carbohydrates are fascinating molecular scaffolds known for their diverse applications in chemistry, biology, medicine, technology, and materials science. In addition, owing to the notable features of Room-Temperature Ionic Liquids (RTILs) such as high-yield, short reaction time, simple handling, excellent recyclability, and environmentally benign nature, they have been extensively utilized as green solvents, catalysts, or both in a wide range of organic transformation methodologies for easy access of a diverse range of biologically relevant molecules. This review highlights the importance of RTILs that offer promising solutions in glycoscience, particularly in relevance to the dissolution, functionalization, glycosylation, and modification of carbohydrates as well as their challenges, impact, and future perspectives.

Trichloroacetimidate-Triggered Expeditious and Novel Synthesis of N-Acylbenzotriazoles

A facile route for the synthesis of a diverse range of N-acylbenzotriazole derivatives from the corresponding carboxylic acids has been established through a carbonyl activation pathway. In this method, trichloroacetonitrile is performed as an effective reagent for an easy access of N-acylbenzotriazoles which was simply proceeded through the activation of carboxylic acids via in situ imidate formation in anhydrous 1,2-dichloroethane followed by addition of 1H-benzotriazole at 80 °C for 3–4 h. Easy handling, one-pot, and metal-free conditions demonstrate the notable merits of the devised protocol.

d-Glucosamine as the Green Ligand for Cu(I)-Catalyzed Regio- and Stereoselective Domino Synthesis of (Z)-3-Methyleneisoindoline-1-ones and (E)-N-Aryl-4H-thiochromen-4-imines

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.

CuAAC mediated synthesis of cyclen cored glycodendrimers of high sugar tethers at low generation

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.

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.

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.

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.

N-Acylbenzotriazoles as Proficient Substrates for an Easy Access to Ureas, Acylureas, Carbamates, and Thiocarbamates via Curtius Rearrangement Using Diphenylphosphoryl Azide (DPPA) as Azide Donor

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.

Recent Developments on Denitrogenative Functionalization of Benzotriazoles

Benzotriazoles are employed as useful synthons in organic synthesis, and due to their unique structural motif, they are able to undergo denitrogenation during the construction of new bonds. Various methods for the functionalization of benzotriazoles as precursors of ­ortho-amino arenediazoniums have recently been developed that involve transition-metal-catalyzed coupling reactions, mainly via cyclization, borylation, alkenylation, alkylation, carbonylation and the formation of carbon–heteroatom bonds. In this short review, we primarily focus on the recent applications of benzotriazoles in organic chemistry that proceed via a denitrogenative process, and the mechanisms are also discussed.

1 Introduction

2 Common Synthetic Routes Allowing Easy Access to Benzotriazole Derivatives

3 Formation of C–C Bonds

3.1 Cyclization Reactions

3.2 Arylation, Alkenylation, Alkylation and Carbonylation Reactions

4 Carbon–Heteroatom Bond Formation

5 Miscellaneous Denitrogenative Functionalization

6 Conclusions and Future Perspectives

An expeditious click approach towards the synthesis of galactose coated novel glyco-dendrimers and dentromers utilizing a double stage convergent method

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 (0^th generation) and 27-peripheral galactose coated glycodentromer 25 (1^st 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.

A proficient double stage convergent approach has been exploited for an easy access of galactose coated novel glycodendrimers and dentromers under CuAAC click condition.

Click inspired synthesis of p-tert-butyl calix[4]arene tethered benzotriazolyl dendrimers and their evaluation as anti-bacterial and anti-biofilm agents

CuAAC inspired calix-[4]arene tethered benzotriazolyl dendrimers were developed and investigated for their therapeutic potential, where 7 displayed potent anti-bacterial and anti-biofilm activities against drug-resistant & slime producing organisms.

Effect of dietary synbiotic supplementation on growth, immune and physiological status of Labeo rohita juveniles exposed to low pH stress

In this study, we investigated the effect of dietary Bacillus circulans PB7 (BCPB7) and fructoligosaccharide (FOS), used singly or in combination for evaluation of growth, immune and physiological status of Labeo rohita (rohu) juveniles reared under low pH and normal pH for 60 days. Experimental fishes were distributed in two sets such as one set continuously exposed to low pH (5.5) and other reared under normal pH (7.0), and fed with four iso-nitrogenous diets viz. basal (control), Bacillus circulans PB7 (BCPB7, 10⁶ cfug^-1), 1% fructooligosaccharide (FOS) and their combination. The effect of such pre, pro and synbiotics dietary treatments on growth performance (weight gain, specific growth rate, feed conversion ratio and protein efficiency ratio), immune response (hematological indices, serum biochemistry, lysozyme, NBT activity), antioxidative status in the form of antioxidant enzyme (catalase, superoxide dismutase, glutathione-S-transferase), acetylcholine esterase (AChE), Na⁺ K⁺ ATPase and stress bio-markers (cortisol, glucose and HSP-70) were examined. The group treated with low pH and fed with control diet (without supplementation) was found to be inhibited (p  <  0.05) in growth and immuno-physiological function. However, supplementation of BCPB7 and FOS was non-significant (p < 0.05) on growth performance and physiological process but their concurrent feeding remarkably improved (p < 0.05) growth and immune-physiological function when exposed to low pH. Overall results indicate that dietary combination of BCPB7 and FOS can be considered an effective synbiotic formula against low pH stress in culture practices of L. rohita juveniles.

An Improved Synthesis of Urea Derivatives from N-Acylbenzotriazole via Curtius Rearrangement

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.

Synthesis of Benz-Fused Azoles via C-Heteroatom Coupling Reactions Catalyzed by Cu(I) in the Presence of Glycosyltriazole Ligands

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.

Silicon Industry Waste Polymethylhydrosiloxane-Mediated Benzotriazole Ring Cleavage: A Practical and Green Synthesis of Diverse Benzothiazoles

A green modification has been introduced to the synthesis of benzothiazoles by using polymethylhydrosiloxane (PMHS) for successive steps of benzotriazole ring cleavage and cyclization, an approach which was previously developed in our lab by the use of n-Bu₃SnH. The use of the silicone industry byproduct PMHS makes this protocol a cost-effective and nontoxic one and thus may be considered for the industrial importance.

Ontogeny of the digestive tract in stinging catfish, Heteropneustes fossilis (Bloch) larvae

Heteropneustes fossilis (Bloch) is an important candidate species for diversification of freshwater aquaculture in India. However, high mortality rate during larval rearing is the most serious bottleneck in commercial production of this species. A proper understanding of the ontogenic development of digestive system provides the basis to understand the nutritional physiology of larvae and develop appropriate feeding strategies. In the present study, the ontogenical development of the digestive tract in H. fossilis larvae was studied from hatching until 30 day post-hatching (dph) at 29 °C. At hatching (2.8 ± 0.2 mm standard length, SL), the digestive tract was undifferentiated and attached dorsally to the yolk sac. At 1 dph (2.9 ± 0.2 mm SL), the mouth opened and oral valves were visible. At 2 dph (3.0 ± 0.3 mm SL), goblet cells were observed in the buccoparyngaeal cavity. At this age, exogenous feeding started and the intestine was differentiated into the anterior and posterior regions, and the rudimentary liver and pancreas were also seen. Small supranuclear vacuoles were observed in the enterocytes of the posterior intestine at 2 dph. Zymogen granules were observed in acinar cells of pancreas by 3 dph, and islets of Langerhans were visible at 4 dph (3.5 ± 0.1 mm SL). At the same age, most of the yolk sac reserves were consumed, whereas they were completely exhausted by 5 dph (3.9 ± 0.5 mm SL). Between 4 and 6 dph, the liver elongated in size and started to accumulate lipids in the hepatocytes. Gastric glands were detected at 4 dph, and the pyloric sphincter was completely differentiated at 9 dph (6.1 ± 0.4 mm SL) as an epithelial fold that separated stomach from the anterior intestine. By 13 dph (8.6 ± 0.2 mm SL), profuse gastric glands were visible inside longitudinal mucosal folds of the stomach. The formation of gastric glands and their development were noticed as the last events in the development of the digestive tract in H. fossilis. This indicated the end of the larval period and the commencement of the juvenile stage. Considering these observations, it is suggested that H. fossilis larvae have a morphologically complete digestive tract by 13 dph. The findings of the study on the development of the digestive system in H. fossilis may help in synchronising the larval stage of development and feeding strategies and would be helpful in improving larval rearing techniques for catfish species.

Benzotriazole as an Efficient Ligand in Cu-Catalyzed Glaser Reaction

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.

Catalytic activity of new heteroleptic [Cu(PPh3)2(β-oxodithioester)] complexes: click derived triazolyl glycoconjugates

Highly efficient and reusable precatalysts of Cu(i) β-oxodithioester PPh₃ complexes for the synthesis of triazolyl glycoconjugates under “click” conditions.

Click inspired synthesis of hexa and octadecavalent peripheral galactosylated glycodendrimers and their possible therapeutic applications

Click inspired glycodendrimers comprising a rigid hexapropargyloxy benzene core with peripheral β-d-galactopyranosidic units were developed and evaluated for their therapeutic potential.

Highly efficient structurally characterised novel precatalysts: di- and mononuclear heteroleptic Cu(i) dixanthate/xanthate–phosphine complexes for azide–alkyne cycloadditions

Prominent catalytic activities of novel di- and mononuclear Cu(i) xanthate/phosphine complexes have been investigated for the synthesis of triazolyl glycoconjugates using Click approach.

Isolation of a new flavonoid and waste to wealth recovery of 6-O-Ascorbyl Esters from Seeds of Aegle marmelos (family- Rutaceae)

Aegle marmelos is a plant species native to India. Commercially available food products such as jam, jelly, candy, squash etc. are prepared from ripe fruit pulp of A. marmelos. Ripe fruit processing accounts for 60% of whole fruit mass while 40% remains unutilized and generates waste (hard shell, pomace, fiber and seeds) on a massive scale which do not have high value applications. A new flavone 3,5,7-trihydroxy-2-(4'-hydroxy-3'-isopentyloxyphenyl-4H-chromen-4-one (5) in addition to the known compounds 1-4, has been isolated from seeds of A. marmelos. Also, compound 7-(3'-methylbut-2'-enyloxy)-2H-chromen-2-one (2) has been isolated for the first time from A. marmelos. The structure of compounds 1-5 was determined by spectral analysis (UV, IR, NMR, etc.). Additionally, the non-edible oil obtained from seeds was investigated for waste to wealth recovery of 6-O-ascorbyl esters in high regioselectivity via one step semi-synthetic approach in the presence of ascorbic acid and H₂SO₄ at ambient temperature.

Limitations of Current Therapeutic Options, Possible Drug Targets and Scope of Natural Products in Control of Leishmaniasis

Soon after the identification of Leishmania parasite as a causative agent, the pentavalent antimony compounds have been the mainstay to treat all forms of leishmaniasis. Due to growing incidences of antimony resistant parasites and unavailability of true antileishmanial compounds, few drugs like pentamidine (antimicrobial), amphotericin B (antifungal) or miltefosine (antitumor) are currently being used but these are associated with serious side effects. Unfortunately, the emergence of amphotericin B and miltefosine resistant parasites in clinical settings has further questioned their sustained use in leishmanial control. Moreover, the parameters of protective immunity are not well understood in leishmanial pathogenesis therefore, a vaccine candidate, either prophylactic or preventive, is still an unrealized goal. In addition, the emergence of insecticide resistance sand flies in disease endemic regions also stance a big threat for the current elimination strategies. Therefore, in lieu of the limited drug regimen and unavailability of a vaccine, the necessity of a true antileishmanial agent is always there. Although, leishmanial infections have been neglected for many decades but recent studies have identified potential drug targets that could be targeted to control the growth of parasites. In recent past many compounds derived from natural sources have also been shown to possess excellent antiparasitic potential; however, most of these studies are limited to primary evaluation and only a few have reached to clinical levels. In this review, we discuss the limitations of current drug regimen, explore possible drug targets of Leishmania species and summarize wide range of compounds isolated from various natural sources that are worth screening as antileishmanial drug candidates.

A thiocyanopalladation/carbocyclization transformation identified through enzymatic screening: stereocontrolled tandem C-SCN and C-C bond formation

Herein we describe a formal thiocyanopalladation/carbocyclization transformation and its parametrization and optimization using a new elevated temperature plate-based version of our visual colorimetric enzymatic screening method for reaction discovery. The carbocyclization step leads to C-SCN bond formation in tandem with C-C bond construction and is highly stereoselective, showing nearly absolute 1,2-anti-stereoinduction (5 examples) for substrates bearing allylic substitution, and nearly absolute 1,3-syn-stereoinduction (16 examples) for substrates bearing propargylic substitution. Based upon these high levels of stereoinduction, the dependence of the 1,2-stereoinduction upon cyclization substrate geometry, and the generally high preference for the transoid vinyl thiocyanate alkene geometry, a mechanistic model is proposed, involving (i) Pd(ii)-enyne coordination, (ii) thiocyanopalladation, (iii) migratory insertion and (iv) β-elimination. Examples of transition metal-mediated C-SCN bond formation that proceed smoothly on unactivated substrates and allow for preservation of the SCN moiety are lacking. Yet, the thiocyanate functionality is of great value for biophysical chemistry (vibrational Stark effect) and medicinal chemistry (S,N-heterocycle construction). The title transformation accommodates C-, O-, N- and S-bridged substrates (6 examples), thereby providing the corresponding carbocyclic or heterocyclic scaffolds. The reaction is also shown to be compatible with a significant range of substituents, varying in steric and electronic demand, including a wide range of substituted aromatics, fused bicyclic and heterocyclic systems, and even biaryl systems. Combination of this new transformation with asymmetric allylation and Grubbs ring-closing metathesis provides for a streamlined enantio- and diastereoselective entry into the oxabicyclo[3.2.1]octyl core of the natural products massarilactone and annuionone A, as also evidenced by low temperature X-ray crystal structure determination. Utilizing this bicyclic scaffold, we demonstrate the versatility of the thiocyanate moiety for structural diversification post-cyclization. Thus, the bridging vinyl thiocyanate moiety is smoothly elaborated into a range of derivative functionalities utilizing transformations that cleave the S-CN bond, add the elements of RS-CN across a π-system and exploit the SCN moiety as a cycloaddition partner (7 diverse examples). Among the new functionalities thereby generated are thiotetrazole and sulfonyl tetrazole heterocycles that serve as carboxylate and phosphate surrogates, respectively, highlighting the potential of this approach for future applications in medicinal chemistry or chemical biology.