N-Glycoside neoglycotrimers from 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl azide

Click-chemistry-inspired synthesis of new series of 1,2,3-triazole fused chromene with glucose triazole conjugates: Antibacterial activity assessment with molecular docking evaluation

A series of new 1,2,3-triazole fused chromene based glucose triazole conjugates were synthesized from chromene fused 1,2,3-triazolyl extended alkyne and 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl azide in good to excellent yield by a copper catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The major advantages include mild reaction conditions, high yield, good substrate scope, and shorter reaction time. The antibacterial efficacy of the compounds were assessed in vitro against human pathogenic Gram-negative E. coli and Gram-positive S. aureus bacteria. Compound 24j was found to be the most potent molecule with zone of inhibition (ZI) of 17 mm and minimum inhibitory concentration (MIC) of 25 μg mL-1 in E. coli and ZI of 16 mm and MIC of 25 μg mL-1 in S. aureus. Also, it significantly inhibited E. coli DNA-gyrase in silico with a binding affinity of -9.4 kcal/mol. Among all the synthesized compounds, 24i, 24d, 24e and 24f showed significant antibacterial activity against both strains and inhibited DNA-gyrase in silico with good binding affinities. Hence, these 1,2,3-triazole fused chromene based glucose triazole conjugates may evolve to be powerful antibacterial agents in recent future, according to structure-activity relationships based on strong antibacterial properties and molecular docking studies.

Design and synthesis of 1,2-dihydroquinoline/chromene fused sugar triazole frameworks by copper-catalyzed one-pot click and intramolecular arylation reactions

Expedient copper-catalyzed one-pot click and intramolecular arylation reactions have been developed for the synthesis of 1,2-dihydroquinoline/chromene-fused triazoles with varying sugar functionalities. It has been observed that the additive TMEDA greatly facilitates this copper-catalyzed cyclization. This reaction involves two mechanistically distinct reactions i.e. an atom-economical click reaction and a direct arylation of a sugar triazole. This method provides rapid and simple access to fused sugar triazoles in moderate to good yields. All the key products were characterized using 1H and 13C NMR and HRMS data.

Design, Synthesis, α-Amylase/α-Glucosidase Inhibition Assay, Induced Fit Docking Study of New Hybrid Compounds Containing 4H-Pyrano[2,3-d]pyrimidine, 1H-1,2,3-Triazole and D-Glucose Components

In this study, the click chemistry between N-propargyl derivatives of substituted 4H-pyrano[2,3-d]pyrimidines and tetra-O-acetyl-α-d-glucopyranosyl azide carried out under catalytic conditions using catalyst CuI@Montmorillonite and additive N,N-diisopropylethylamine (DIPEA). The yields of obtained hybrid compounds having 4H-pyrano[2,3-d]pyrimidine connected to 1H-1,2,3-triazole rings were about 85-94 %. All these synthesized hybrid compounds were examined for in vitro α-amylase (with IC₅₀ values in the range of 103.63±1.13 μM to 295.45±1.11 μM) and α-glucosidase (with IC₅₀ values in the range of 45.63±1.14 μM to 184.52±1.15) inhibitory activity. Amongst this series, ethyl ester 8m showed the best inhibitory activity against α-amylase with IC₅₀ of 103.63±1.13 μM, while ethyl ester 8t exhibited the highest activity against α-glucosidase with IC₅₀ of 45.63±1.14 μM. The kinetics of the inhibition of compound 8t showed the competitive α-glucosidase inhibitor property of this compound. Furthermore, the most potent compounds had any cytotoxicity against human normal cells. Induced fit docking and molecular dynamics simulation calculations indicated that the inhibition potential compounds 8m and 8t had the active interactions with the residues in receptors of corresponding tested enzymes. The calculated binding free energy from MM-GBSA approach showed that the major energy components contributed to the active binding of these studied inhibitors, including Coulomb, lipophilic and van der Waals energy. Further, 300 ns MD simulation showed that studied ligand-protein complexes were stable and indicated the structural observations into mode of binding in these complexes.

Radiosynthesis and biological evaluation of fluorine-18 labeled N-acetylgalactosamine derivative [18F]FPGalNAc for PET imaging of asialoglycoprotein receptor-positive tumors

INTRODUCTION

The asialoglycoprotein receptor(ASGPR) is abundantly expressed on the surface of hepatocytes where it recognizes and endocytoses glycoproteins with galactosyl and N-acetylgalactosamine groups. ASGPR not only express on the surface of hepatocytes, but also express in several tumor cells (HepG2, A549 and HCT116). The purpose of this study was to develop a ASGPR-specific radiofluorinated ligand for positron emission tomography (PET) imaging in several tumor models.

METHODS

The radiosynthesis of [18F]FPGalNAc was initiated with fluorine-18 and 5-(p-toluenesulfonyl)-1-yne. The obtained 5-[18F]fluoro-1-pentyne intermediate was then reacted with 2-acetamido-2-deoxy-β-d-galactopyranosyl azide using "click chemistry" to produce the final product. The Kd of the product was determined in HepG2 cells at a range of concentrations of [18F]FPGalNAc. Cellular uptake and blocking experiments were also performed. In vivo biodistribution studies were performed in nude mice bearing HCT116 tumor and micro positron emission tomography/computed tomography (PET/CT) evaluations were then performed in tumor-bearing mice (HepG2, HCT116) models.

RESULTS

The radiosynthesis of [18F]FPGalNAc required 50 min with 5-6% RCY (radiochemical yield). The Kd of [18F]FPGalNAc to ASGPR in HepG2 cells was 0.25 ± 0.02 mM. Uptake values of 0.29% were observed within 30 min of incubation with HepG2 cells, which could be blocked by 200 mM d(+)-galactose (< 0.13%). The data of biodistribution revealed that the uptake of [18F]FPGalNAc was higher in kidneys and liver, and lower in muscle, bone and brain. In vivo micro PET studies, both HCT116 and HepG2 tumors showed high uptake for [18F]FPGalNAc, the radio of tumor/muscle (T/M) was 3.7 and 3.91, respectively.

CONCLUSIONS

In vitro assays and in vivo PET/CT imaging and biodistribution studies showed that [18F]FPGalNAc represents a promising tumor imaging agent that can provide insight into ASGPR related disease.

Linear triazole-linked pseudo oligogalactosides as scaffolds for galectin inhibitor development

Galectins play key roles in numerous biological processes. Their mode of action depends on their localization which can be extracellular, cytoplasmic, or nuclear and is partly mediated through interactions with β-galactose containing glycans. Galectins have emerged as novel therapeutic targets notably for the treatment of inflammatory disorders and cancers. This has stimulated the design of carbohydrate-based inhibitors targeting the carbohydrate recognition domains (CRDs) of the galectins. Pursuing this approach, we reasoned that linear oligogalactosides obtained by straightforward iterative click chemistry could mimic poly-lactosamine motifs expressed at eukaryote cell surfaces which the extracellular form of galectin-3, a prominent member of the galectin family, specifically recognizes. Affinities toward galectin-3 consistently increased with the length of the representative oligogalactosides but without reaching that of oligo-lactosamines. Elucidation of the X-ray crystal structures of the galectin-3 CRD in complex with a synthesized di- and tri-galactoside confirmed that the compounds bind within the carbohydrate-binding site. The atomic structures revealed that binding interactions mainly occur with the galactose moiety at the non-reducing end, primarily with subsites C and D of the CRD, differing from oligo-lactosamine which bind more consistently across the whole groove formed by the five subsites (A-E) of the galectin-3 CRD.

Synthesis and Reactivity of Propargylamines in Organic Chemistry

Propargylamines are a versatile class of compounds which find broad application in many fields of chemistry. This review aims to describe the different strategies developed so far for the synthesis of propargylamines and their derivatives as well as to highlight their reactivity and use as building blocks in the synthesis of chemically relevant organic compounds. In the first part of the review, the different synthetic approaches to synthesize propargylamines, such as A³ couplings and C-H functionalization of alkynes, have been described and organized on the basis of the catalysts employed in the syntheses. Both racemic and enantioselective approaches have been reported. In the second part, an overview of the transformations of propargylamines into heterocyclic compounds such as pyrroles, pyridines, thiazoles, and oxazoles, as well as other relevant organic derivatives, is presented.

Nonclassical Routes for Amide Bond Formation

The present review offers an overview of nonclassical (e.g., with no pre- or in situ activation of a carboxylic acid partner) approaches for the construction of amide bonds. The review aims to comprehensively discuss relevant work, which was mainly done in the field in the last 20 years. Organization of the data follows a subdivision according to substrate classes: catalytic direct formation of amides from carboxylic and amines ( section 2 ); the use of carboxylic acid surrogates ( section 3 ); and the use of amine surrogates ( section 4 ). The ligation strategies (NCL, Staudinger, KAHA, KATs, etc.) that could involve both carboxylic acid and amine surrogates are treated separately in section 5 .

Origin of problems related to Staudinger reduction in carbopeptoid syntheses

We report the solid phase synthesis of -GG-X-GG- type α/β-carbopeptoids incorporating RibAFU(ip) (1a, tX) or XylAFU(ip) (2a, cX) sugar amino acids. Though coupling efficacy is moderate, both the lengthier synthetic route using Fmoc derivative (e.g., Fmoc-RibAFU(ip)-OH) and the azido derivative (e.g., N₃-RibAFU(ip)-OH) via Staudinger reaction with nBu₃P can be successfully applied. Both X-ray diffraction, ¹H- and ³¹P-NMR, and theoretical (QM) data support and explain why the application of Ph₃P as Staudinger reagent is "ineffective" in the case of a cis stereoisomer, if cX is attached to the preceding residue with a peptide (-CONH-) bond. The failure of the polypeptide chain elongation with N₃-cX originates from the "coincidence" of a steric crowdedness and an electronic effect disabling the mandatory nucleophilic attack during the hydrolysis of a quasi penta-coordinated triphenylphosphinimine. Nevertheless, the synthesis of the above α/β-chimera peptides as completed now by a new pathway via 1,2-O-isopropylidene-3-azido-3-deoxy-ribo- and -xylo-furanuronic acid (H-RibAFU(ip)-OH 1a and H-XylAFU(ip)-OH 2a) coupled with N-protected α-amino acids on solid phase could serve as useful examples and starting points of further synthetic efforts.

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.

Design and synthesis of sugar-triazole based uracil appended sugar-imine derivatives – an application in DNA binding studies

The interaction of the sugar-triazoles with CT-DNA was explored, which revealed that all the compounds could interact with CT-DNA through groove binding, which was further supported by the docking analysis.

A convenient synthesis of N-linked diglycose derivatives based on one-pot tandem Staudinger/aza-Wittig/reduction and biological evaluation

A series of novel N-linked diglycose derivatives 9 and 10 were conveniently and directly synthesized based on the key step of one-pot tandem Staudinger/aza-Wittig/reduction reaction from the azido sugar and sugar-derived aldehyde followed by deprotection. The biological activities against glycosidases (α-amylase, α-glucosidase, and β-glucosidase) and HIV-RT and antitumor activity of these compounds were preliminarily evaluated.

4-Butyl-1-(2,3,4-tri-O-acetyl-β-l-fuco-pyranos-yl)-1H-1,2,3-triazole

The title compound, C(18)H(27)N(3)O(7), was synthesized by Cu(I)-catalysed coupling of an azide with an alkyne as part of a study into the synthesis of N-glycosyl-1,2,3-triazoles. The crystal structure confirms the selective formation of the β-conformer of the pyran-ose N-glycoside, thus confirming the retention of stereochemistry during heterocycle formation with the N-glycosyl triazole group occupying the equatorial position at the anomeric C atom. The structure exhibits two crystallographically independent mol-ecules (A and B) with essentially identical conformations with a weighted r.m.s. deviation of only 0.09 Å. The mol-ecules are arranged in layers with hydro-phobic and more polar sections built from the butyl triazole units on the one hand and the more polar moieties dominated by the carbohydrate units on the other. Within the polar layers, inter-molecular inter-actions are dominated by a three-dimensional network of weak C-H⋯O hydrogen bonds with the acetyl keto O atoms as the hydrogen-bond acceptors. The triazole units inter-act with each other via C-H⋯N hydrogen bonds which connect the mol-ecules into two infinite chains of mol-ecules made up of either A mol-ecules or B mol-ecules that stretch parallel to each other along [100]. Between the butyl groups no directional inter-actions are observed.

1,2,3-Triazoles

Rapid progress in the synthetic application of benzotriazole derivatives in the last 20 years has resulted in over 1000 scientific papers on the subject. This fact is reflected in Section 5.01.7, which involves almost a half of the volume of this chapter. The section is arranged according to hybridization of the C-α atom and atomic numbers of the atoms in positions β and γ to allow an easy access to the material of interest. Recent discovery of copper catalysis in [3+2] cycloadditions of azides to acetylenes, the so-called ‘click chemistry’, which boosted application of the 1,2,3-triazole derivatives, especially in medicinal chemistry, is presented in Section 5.01.9. From the point of view of practical applications, Section 5.01.11 is organized according to the number, position, and combination of the substituents at the aromatic rings. Another novel feature that has no precedence in the previous editions of Comprehensive Heterocyclic Chemistry is an addition of triazole and benzotriazole complexes with various transitions metals to Section 5.01.4.

Synthesis of a fluorescence-labeled K30 antigen repeating unit using click chemistry

An N-dansyl-labeled K30 antigen repeating unit, [4-[5-(N,N'-dimethylamino)naphthalene-1-sulfonamine]-1H-1,2,3-triazol-1-yl]hexyl beta-D-glucopyranosyluronate-(1-->3)-alpha-D-galactopyranosyl-alpha-D-mannopyranosyl-(1-->3)-beta-D-galactopyranoside, was synthesized using click chemistry, the copper(I)-catalyzed 1,3-dipolar cycloaddition reaction of an azide and an alkyne. The target compound could further facilitate the studies of interactions among K30 oligosaccharides and proteins.

Recent applications of the CuI-catalysed Huisgen azide–alkyne 1,3-dipolar cycloaddition reaction in carbohydrate chemistry

This article surveys recent applications of Cu(I)-catalysed 1,3-dipolar cycloaddition of azides and alkynes in carbohydrate chemistry, highlighting developments in the preparation of simple glycoside and oligosaccharide mimetics, glyco-macrocycles, glycopeptides, glyco-clusters and carbohydrate arrays.