- Cu-free Sonogashira Type Cross-Coupling of 6-Halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) Quinazolin-4(3H)-ones as Potential Antimicrobial Agents
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C(sp)–C(sp2) bond formation via Sonogashira cross-coupling reactions on 6-halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl)quinazolin-4(3H)-ones with appropriate alkynes was explored. Optimization of reaction conditions with various catalysts, ligands, bases, and solvents was conducted. The combination of PdCl2(MeCN)2 with X-Phos proved to be the best metal–ligand system for this conversion in the presence of triethylamine (Et3N) in tetrahydrofuran at room temperature for iodosubstrates, at 80°C for the bromosubstrates in 8?h, and also for the chlorosubstrates in 16?h. We also demonstrated synthesis of a successful diversity-oriented synthesis library of highly functionalized quinazolinones via Cu-free Sonogashira coupling of diverse aryl halides and azido-alkyne (“click”) ligation reactions with substituted azides. The library exhibited significant antimicrobial activity when screened against several microorganisms.
- Poudapally, Suresh,Gurram, Venkateshwarlu,Garlapati, Ramesh,Tulluri, Chiranjeevi,Addepally, Uma,Vidya,Sharma, Somesh,Sen, Subhabrata,Pottabathini, Narender
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Read Online
- Epoxy functionalized polymethacrylates based on various multifunctional D-glucopyranoside acetals
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The synthesis of acetal-derived d-glucopyranosides with a various number of hydroxyl groups (the first step, acetalization) and their modified forms with bromoester groups (the second step, esterification) are presented here. The latter, due to the type o
- Neugebauer, Dorota,Mielanczyk, Anna,Waskiewicz, Sylwia,Biela, Tadeusz
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Read Online
- SnCl2-Catalyzed Acetalation/Selective Benzoylation Sequence for the Synthesis of Orthogonally Protected Glycosyl Acceptors
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Based on SnCl2-catalyzed acetalation and selective benzoylation, a one-pot strategy to efficiently synthesize orthogonally protected glycosyl acceptors with 2-OH/3-OH was developed. Consequently, 2-OBz or 3-OBz 4,6-O-benzylidene galactosides and glucosides were efficiently prepared in moderate to high yields starting from free galactosides and glucosides, and were used as valuable glycosyl acceptors for the synthesis of blood group antigens O and B analogues in this study.
- Dong, Hai,Feng, Guang-Jing,Guo, Yang-Fan,Liu, Chun-Yang,Lv, Jian
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supporting information
(2022/04/03)
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- Sweet Drugs for Bad Bugs: A Glycomimetic Strategy against the DC-SIGN-Mediated Dissemination of SARS-CoV-2
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The C-type lectin receptor DC-SIGN is a pattern recognition receptor expressed on macrophages and dendritic cells. It has been identified as a promiscuous entry receptor for many pathogens, including epidemic and pandemic viruses such as SARS-CoV-2, Ebola virus, and HIV-1. In the context of the recent SARS-CoV-2 pandemic, DC-SIGN-mediated virus dissemination and stimulation of innate immune responses has been implicated as a potential factor in the development of severe COVID-19. Inhibition of virus binding to DC-SIGN, thus, represents an attractive host-directed strategy to attenuate overshooting innate immune responses and prevent the progression of the disease. In this study, we report on the discovery of a new class of potent glycomimetic DC-SIGN antagonists from a focused library of triazole-based mannose analogues. Structure-based optimization of an initial screening hit yielded a glycomimetic ligand with a more than 100-fold improved binding affinity compared to methyl α-d-mannopyranoside. Analysis of binding thermodynamics revealed an enthalpy-driven improvement of binding affinity that was enabled by hydrophobic interactions with a loop region adjacent to the binding site and displacement of a conserved water molecule. The identified ligand was employed for the synthesis of multivalent glycopolymers that were able to inhibit SARS-CoV-2 spike glycoprotein binding to DC-SIGN-expressing cells, as well as DC-SIGN-mediated trans-infection of ACE2+ cells by SARS-CoV-2 spike protein-expressing viruses, in nanomolar concentrations. The identified glycomimetic ligands reported here open promising perspectives for the development of highly potent and fully selective DC-SIGN-targeted therapeutics for a broad spectrum of viral infections.
- Cramer, Jonathan,Lakkaichi, Adem,Aliu, Butrint,Jakob, Roman P.,Klein, Sebastian,Cattaneo, Ivan,Jiang, Xiaohua,Rabbani, Said,Schwardt, Oliver,Zimmer, Gert,Ciancaglini, Matias,Abreu Mota, Tiago,Maier, Timm,Ernst, Beat
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supporting information
p. 17465 - 17478
(2021/11/04)
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- Site-Selective Acylation of Pyranosides with Oligopeptide Catalysts
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Herein, we report the oligopeptide-catalyzed site-selective acylation of partially protected monosaccharides. We identified catalysts that invert site-selectivity compared to N-methylimidazole, which was used to determine the intrinsic reactivity, for 4,6
- Seitz, Alexander,Wende, Raffael C.,Roesner, Emily,Niedek, Dominik,Topp, Christopher,Colgan, Avene C.,McGarrigle, Eoghan M.,Schreiner, Peter R.
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p. 3907 - 3922
(2021/03/09)
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- Carbohydrate-Derived Metal-Chelator-Triggered Lipids for Liposomal Drug Delivery
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Liposomes are versatile three-dimensional, biomaterial-based frameworks that can spatially enclose a variety of organic and inorganic biomaterials for advanced targeted-delivery applications. Implementation of external-stimuli-controlled release of their cargo will significantly augment their wide application for liposomal drug delivery. This paper presents the synthesis of a carbohydrate-derived lipid, capable of changing its conformation depending on the presence of Zn2+: an active state in the presence of Zn2+ ions and back to an inactive state in the absence of Zn2+ or when exposed to Na2EDTA, a metal chelator with high affinity for Zn2+ ions. This is the first report of a lipid triggered by the presence of a metal chelator. Total internal reflection fluorescence microscopy and a single-liposome study showed that it indeed was possible for the lipid to be incorporated into the bilayer of stable liposomes that remained leakage-free for the fluorescent cargo of the liposomes. On addition of EDTA to the liposomes, their fluorescent cargo could be released as a result of the membrane-incorporated lipids undergoing a conformational change.
- Holmstr?m, Thomas,Galsgaard Malle, Mette,Wu, Shunliang,Jensen, Knud J?rgen,Hatzakis, Nikos S.,Pedersen, Christian Marcus
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supporting information
p. 6917 - 6922
(2021/02/26)
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- Triethylamine-methanol mediated selective removal of oxophenylacetyl ester in saccharides
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A highly selective, mild, and efficient method for the cleavage of oxophenylacetyl ester protected saccharides was developed using triethylamine in methanol at room temperature. The reagent proved successful against different labile groups like acetal, ketal, and PMB and also generated good yields of the desired saccharides bearing lipid esters. Further, we also observed DBU in methanol as an alternative reagent for the deprotection of acetyl, benzoyl, and oxophenylacetyl ester groups. This journal is
- Rasool, Javeed Ur,Kumar, Atul,Ali, Asif,Ahmed, Qazi Naveed
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supporting information
p. 338 - 347
(2021/01/29)
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- Me3SI-promoted chemoselective deacetylation: a general and mild protocol
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A Me3SI-mediated simple and efficient protocol for the chemoselective deprotection of acetyl groups has been developedviaemploying KMnO4as an additive. This chemoselective deacetylation is amenable to a wide range of substrates, tolerating diverse and sensitive functional groups in carbohydrates, amino acids, natural products, heterocycles, and general scaffolds. The protocol is attractive because it uses an environmentally benign reagent system to perform quantitative and clean transformations under ambient conditions.
- Gurawa, Aakanksha,Kashyap, Sudhir,Kumar, Manoj
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p. 19310 - 19315
(2021/06/03)
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- Both d - And l -Glucose Polyphosphates Mimic d - myo-Inositol 1,4,5-Trisphosphate: New Synthetic Agonists and Partial Agonists at the Ins(1,4,5)P3Receptor
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Chiral sugar derivatives are potential cyclitol surrogates of the Ca2+-mobilizing intracellular messenger d-myo-inositol 1,4,5-trisphosphate [Ins(1,4,5)P3]. Six novel polyphosphorylated analogues derived from both d- and l-glucose were synthesized. Binding to Ins(1,4,5)P3 receptors [Ins(1,4,5)P3R] and the ability to release Ca2+ from intracellular stores via type 1 Ins(1,4,5)P3Rs were investigated. β-d-Glucopyranosyl 1,3,4-tris-phosphate, with similar phosphate regiochemistry and stereochemistry to Ins(1,4,5)P3, and α-d-glucopyranosyl 1,3,4-tris-phosphate are full agonists, being equipotent and 23-fold less potent than Ins(1,4,5)P3, respectively, in Ca2+-release assays and similar to Ins(1,4,5)P3 and 15-fold weaker in binding assays. They can be viewed as truncated analogues of adenophostin A and refine understanding of structure-activity relationships for this Ins(1,4,5)P3R agonist. l-Glucose-derived ligands, methyl α-l-glucopyranoside 2,3,6-trisphosphate and methyl α-l-glucopyranoside 2,4,6-trisphosphate, are also active, while their corresponding d-enantiomers, methyl α-d-glucopyranoside 2,3,6-trisphosphate and methyl α-d-glucopyranoside 2,4,6-trisphosphate, are inactive. Interestingly, both l-glucose-derived ligands are partial agonists: they are among the least efficacious agonists of Ins(1,4,5)P3R yet identified, providing new leads for antagonist development.
- Shipton, Megan L.,Riley, Andrew M.,Rossi, Ana M.,Brearley, Charles A.,Taylor, Colin W.,Potter, Barry V. L.
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p. 5442 - 5457
(2020/07/21)
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- Stereoselective Phenylselenoglycosylation of Glycals Bearing a Fused Carbonate Moiety toward the Synthesis of 2-Deoxy-β-galactosides and β-Mannosides
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A phenylselenoglycosylation reaction of glycal derivatives mediated by diphenyl diselenide and phenyliodine(III) bis(trifluoroacetate) under mild conditions is described. Stereoselective glycosylation has been achieved by installing fused carbonate on those glycals. 3,4-O-Carbonate galactals and 2,3-O-carbonate 2-hydroxyglucals are converted into corresponding glycosides in good yields with excellent β-selectivity, resulting in 2-phenylseleno-2-deoxy-β-galactosides and 2-phenylseleno-β-mannosides which are good precursors of 2-deoxy-β-galactosides and β-mannosides, respectively.
- Li, Zhongjun,Meng, Shuai,Yao, Wang,Zhong, Wenhe
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supporting information
(2020/04/09)
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- Acceleration and deceleration factors on the hydrolysis reaction of 4,6-O-benzylidene acetal group
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The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS? were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both Ea/ΔH? and A/ΔS? were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.
- Maki, Yuta,Kajihara, Yasuhiro,Nomura, Kota,Okamoto, Ryo,Izumi, Masayuki,Mizutani, Yasuhisa
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p. 15849 - 15856
(2021/01/18)
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- Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups
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The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate-attached benzene, such as the methoxy group a
- Fujiki, Katsumasa,Tanaka, Katsunori
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supporting information
p. 4616 - 4620
(2020/07/06)
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- A Direct Method for the Efficient Synthesis of Benzylidene Acetal at Room Temperature
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For the first time, a metal-free direct method has been developed for the efficient synthesis of benzylidene acetal at room temperature using Dowex 50WX8 as a solid acid catalyst and Cl3CCN as a novel water scavenger. At room temperature, a wide variety of aryl and α,β-unsaturated aldehydes react readily with functionalized 1,2- and 1,3-diols to furnish the corresponding acetals in very good yields. Labile functional groups, like N-Boc, N-Cbz, -OTBDMS, -OBn, -N3 and acetonide are found to be stable under the reaction conditions. The versatility of this method is further demonstrated with carbohydrate substrates and optically active diols.
- Reddy, Narra Rajashekar,Kumar, Rashmi,Baskaran, Sundarababu
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supporting information
p. 1548 - 1552
(2019/01/09)
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- Assessing the Optimal Deoxygenation Pattern of Dodecyl Glycosides for Antimicrobial Activity Against Bacillus anthracis
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The discovery of the bactericide dodecyl 2,6-dideoxypyranoside reorganizing membrane phospholipid matrix of Bacillus species into a hexagonal phase, encouraged further research on glycone deoxygenation/bioactivity relationship. We now describe expedient syntheses of new 2-, 3-, 4-deoxy, 2,3- and 3,4-dideoxy glycosides in moderate to good yields. Interestingly, Amberlyst 15 is a key protagonist, efficiently applied for the transacetalation of alkyl deoxy glycosides and for ring contraction to access regioselectively hexofuranosides. The 2-deoxy-d-arabino pyranoside affords the higher MIC values against two Bacillus spp. and Enterococcus faecalis, while a 4-fold decrease or higher was found by inversion of configuration or by deoxygenation at C-3. While 2,3- and 3,4-dideoxygenation do not improve bioactivity, the 4,6-dideoxy-α-d-xylo-hexopyranoside remains a promising glycoside, presenting low MIC values for all species tested, and low cytotoxicity in intestinal and liver cell models.
- Dias, Catarina,Martins, Alice,Pelerito, Ana,Oliveira, Maria C.,Contino, Marialessandra,Colabufo, Nicola A.,Rauter, Amélia P.
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p. 2224 - 2233
(2019/02/19)
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- Phosphotungstic acid as a novel acidic catalyst for carbohydrate protection and glycosylation
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This work demonstrates the utilization of phosphotungstic acid (PTA) as a novel acidic catalyst for carbohydrate reactions, such as per-O-acetylation, regioselective O-4,6 benzylidene acetal formation, regioselective O-4 ring-opening, and glycosylation. These reactions are basic and salient during the synthesis of carbohydrate-based bioactive oligomers. Phosphotungstic acid's high acidity and eco-friendly character make it a tempting alternative to corrosive homogeneous acids. The various homogenous acid catalysts were replaced by the phosphotungstic acid solely for different carbohydrate reactions. It can be widely used as a catalyst for organic reactions as it is thermally stable and easy to handle. In our work, the reactions are operated smoothly under ambient conditions; the temperature varies from 0 °C to room temperature. Good to excellent yields were obtained in all four kinds of reactions.
- Chen, Jyun-Siao,Sankar, Arumugam,Lin, Yi-Jyun,Huang, Po-Hsun,Liao, Chih-Hsiang,Wu, Shen-Shen,Wu, Hsin-Ru,Luo, Shun-Yuan
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p. 33853 - 33862
(2019/11/11)
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- To acetyl cedilanid glucose modified compound liposomes and the use thereof (by machine translation)
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The invention discloses a de-acetyl cedilanid glucose modified compound liposome and its application. Mainly from the cedilanid glucose-based reconstruction, to glucose and 2 - amino glucose as raw material for some molecular modification with the end of the digoxin 3 - hydroxyl at the delivery into connected to acetyl cedilanid glucose-based modified product, in active under the guide of the choose to conform with the requirements of the molecule. By synthesis to acetylation cedilanid glucose modified compounds (2 - O - benzyl - β - D - glucopyranoside - acetyl cedilanid and the like), so as to enhance the anti-cancer effect of such compounds, improve the strength of the titer, prolong the half-life, at the same time the modified compound preparation into the liposome, improve the targeting [...], reduce cardiac toxicity. (by machine translation)
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Paragraph 0017; 0020
(2019/05/22)
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- Conformational analysis of the disaccharide methyl a-d-mannopyranosyl-(1→3)-2-O-acetyl-β-D-manno-pyranoside monohydrate
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The crystal structure of methyl β-d-mannopyranosyl-(1→3)-2-O-acetyl-β-d-mannopyranoside monohydrate, C15H26O12.H2O, (II), has been determined and the structural parameters for its constituent β-d-mannopyranosyl residue compared with those for methyl β-d-mannopyranoside. Mono-O-acetylation appears to promote the crystallization of (II), inferred from the difficulty in crystallizing methyl β-d-mannopyranosyl-(1→3)-β-d-mannopyranoside despite repeated attempts. The conformational properties of the O-acetyl side chain in (II) are similar to those observed in recent studies of peracetylated mannose-containing oligosaccharides, having a preferred geometry in which the C2—H2 bond eclipses the C O bond of the acetyl group. The C2—O2 bond in (II) elongates by ≈0.02 ? upon O-acetylation. The phi (φ) and psi () torsion angles that dictate the conformation of the internal O-glycosidic linkage in (II) are similar to those determined recently in aqueous solution by NMR spectroscopy for unacetylated (II) using the statistical program MA'AT, with a greater disparity found for (? = ≈16°) than for φ (? = ≈6°).
- Zhang, Wenhui,Wu, Qingquan,Oliver, Allen G.,Serianni, Anthony S.
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p. 610 - 615
(2019/06/14)
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- Synthesis and O-Glycosidic Linkage Conformational Analysis of 13C-Labeled Oligosaccharide Fragments of an Antifreeze Glycolipid
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NMR studies of two 13C-labeled disaccharides and a tetrasaccharide were undertaken that comprise the backbone of a novel thermal hysteresis glycolipid containing a linear glycan sequence of alternating [βXylp-(1→4)-βManp-(1→4)]n dimers. Experimental trans-glycoside NMR J-couplings, parameterized equations obtained from density functional theory (DFT) calculations, and an in-house circular statistics package (MA'AT) were used to derive conformational models of linkage torsion angles φ and ψ in solution, which were compared to those obtained from molecular dynamics simulations. Modeling using different probability distribution functions showed that MA'AT models of φ in βMan(1→4)βXyl and βXyl(1→4)βMan linkages are very similar in the disaccharide building blocks, whereas MA'AT models of ψ differ. This pattern is conserved in the tetrasaccharide, showing that linkage context does not influence linkage geometry in this linear system. Good agreement was observed between the MA'AT and MD models of ψ with respect to mean values and circular standard deviations. Significant differences were observed for φ, indicating that revision of the force-field employed by GLYCAM is probably needed. Incorporation of the experimental models of φ and ψ into the backbone of an octasaccharide fragment leads to a helical amphipathic topography that may affect the thermal hysteresis properties of the glycolipid.
- Zhang, Wenhui,Meredith, Reagan,Yoon, Mi-Kyung,Wang, Xiaocong,Woods, Robert J.,Carmichael, Ian,Serianni, Anthony S.
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p. 1706 - 1724
(2019/02/14)
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- Binding of the Bacterial Adhesin FimH to Its Natural, Multivalent High-Mannose Type Glycan Targets
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Multivalent carbohydrate-lectin interactions at host-pathogen interfaces play a crucial role in the establishment of infections. Although competitive antagonists that prevent pathogen adhesion are promising antimicrobial drugs, the molecular mechanisms underlying these complex adhesion processes are still poorly understood. Here, we characterize the interactions between the fimbrial adhesin FimH from uropathogenic Escherichia coli strains and its natural high-mannose type N-glycan binding epitopes on uroepithelial glycoproteins. Crystal structures and a detailed kinetic characterization of ligand-binding and dissociation revealed that the binding pocket of FimH evolved such that it recognizes the terminal α(1-2)-, α(1-3)-, and α(1-6)-linked mannosides of natural high-mannose type N-glycans with similar affinity. We demonstrate that the 2000-fold higher affinity of the domain-separated state of FimH compared to its domain-associated state is ligand-independent and consistent with a thermodynamic cycle in which ligand-binding shifts the association equilibrium between the FimH lectin and the FimH pilin domain. Moreover, we show that a single N-glycan can bind up to three molecules of FimH, albeit with negative cooperativity, so that a molar excess of accessible N-glycans over FimH on the cell surface favors monovalent FimH binding. Our data provide pivotal insights into the adhesion properties of uropathogenic Escherichia coli strains to their target receptors and a solid basis for the development of effective FimH antagonists.
- Sauer, Maximilian M.,Jakob, Roman P.,Luber, Thomas,Canonica, Fabia,Navarra, Giulio,Ernst, Beat,Unverzagt, Carlo,Maier, Timm,Glockshuber, Rudi
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supporting information
p. 936 - 944
(2019/01/11)
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- Total Synthesis and Biological Evaluation of the Glycosylated Macrocyclic Antibiotic Mangrolide A
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The macrocyclic antibiotic mangrolide A has been described to exhibit potent activity against a number of clinically important Gram-negative pathogens. Reported is the first enantioselective total synthesis of mangrolide A and derivatives. Salient features of this synthesis include a highly convergent macrocycle preparation, stereoselective synthesis of the disaccharide moiety, and two β-selective glycosylations. The synthesis of mangrolide A and its analogues enabled the re-examination of its activity against bacterial pathogens, and only minimal activity was observed.
- Hattori, Hiromu,Roesslein, Joel,Caspers, Patrick,Zerbe, Katja,Miyatake-Ondozabal, Hideki,Ritz, Daniel,Rueedi, Georg,Gademann, Karl
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supporting information
p. 11020 - 11024
(2018/07/31)
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- Synthesis of 1,2,3-triazolyl analog of Neisseria meningitidis A capsular polysaccharide
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Towards constructing a stable, non-hydrolyzable linkage for Neisseria meningitidis type A (MenA) polysaccharide, the phosphate bridge of its (1→6)-linked 2-acetamido-2-deoxy-α-D-mannopyranosyl phosphate repeating unit was replaced by a triazolyl analog using Cu(I) catalyzed click reaction. The synthesis involved anomeric azidation of N-acetyl-D-mannosamine derivative from its acetate precursor using stoichiometric amount of FeCl3 and one-pot synthesis of precursors for di- and tri- triazolyl saccharides with an azidoethyl spacer at the reducing end for bioconjugation.
- Vangala, Madhuri,Hotha, Srinivas
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p. 393 - 413
(2019/01/04)
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- KinITC—One Method Supports both Thermodynamic and Kinetic SARs as Exemplified on FimH Antagonists
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Affinity data, such as dissociation constants (KD) or inhibitory concentrations (IC50), are widely used in drug discovery. However, these parameters describe an equilibrium state, which is often not established in vivo due to pharmacokinetic effects and they are therefore not necessarily sufficient for evaluating drug efficacy. More accurate indicators for pharmacological activity are the kinetics of binding processes, as they shed light on the rate of formation of protein–ligand complexes and their half-life. Nonetheless, although highly desirable for medicinal chemistry programs, studies on structure–kinetic relationships (SKR) are still rare. With the recently introduced analytical tool kinITC this situation may change, since not only thermodynamic but also kinetic information of the binding process can be deduced from isothermal titration calorimetry (ITC) experiments. Using kinITC, ITC data of 29 mannosides binding to the bacterial adhesin FimH were re-analyzed to make their binding kinetics accessible. To validate these kinetic data, surface plasmon resonance (SPR) experiments were conducted. The kinetic analysis by kinITC revealed that the nanomolar affinities of the FimH antagonists arise from both (i) an optimized interaction between protein and ligand in the bound state (reduced off-rate constant koff) and (ii) a stabilization of the transition state or a destabilization of the unbound state (increased on-rate constant kon). Based on congeneric ligand modifications and structural input from co-crystal structures, a strong relationship between the formed hydrogen-bond network and koff could be concluded, whereas electrostatic interactions and conformational restrictions upon binding were found to have mainly an impact on kon.
- Zihlmann, Pascal,Silbermann, Marleen,Sharpe, Timothy,Jiang, Xiaohua,Mühlethaler, Tobias,Jakob, Roman P.,Rabbani, Said,Sager, Christoph P.,Frei, Priska,Pang, Lijuan,Maier, Timm,Ernst, Beat
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supporting information
p. 13049 - 13057
(2018/08/17)
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- DMSO as a Switchable Alkylating Agent in Heteroarene C?H Functionalization
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Herein, we report a novel strategy for the activation of DMSO to act as a versatile alkylating agent in heteroarene C?H functionalization. This direct, simple, and mild switch between methylation/trideuteromethylation and methylthiomethylation of heteroarenes was achieved under reagent-controlled photoredox catalysis conditions. The proposed mechanism is supported by both experimental and computational studies.
- Garza-Sanchez, R. Aleyda,Patra, Tuhin,Tlahuext-Aca, Adrian,Strieth-Kalthoff, Felix,Glorius, Frank
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supporting information
p. 10064 - 10068
(2018/07/29)
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- A Domino Epoxide Ring-Opening Xanthate Migration Reaction: An Alternative Entry to Thiosugars
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A sterereospecific and efficient synthesis of thiosugars derived from levoglucosenone and methyl α-d-glucopyranoside was developed by a domino epoxide ring opening- xanthate migration to afford 1,3-oxathiolane-2-thiones in high yields. The stereochemical outcome of the new C–S bond was defined by the configuration of the starting materials. The 1,3-oxathiolane-2-thiones were subsequently submitted to a second tandem reaction affording the corresponding 2,3-episulfide alcohols. The thiosugars obtained are useful building blocks for the synthesis of thiooligosaccharides with potential biological properties.
- Comba, María B.,Mangione, María I.,Suárez, Alejandra G.,Sarotti, Ariel M.,Spanevello, Rolando A.
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p. 6848 - 6856
(2018/12/11)
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- Structure-Based Design of a Monosaccharide Ligand Targeting Galectin-8
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Galectin-8 is a β-galactoside-recognising protein that has a role in the regulation of bone remodelling and is an emerging new target for tackling diseases with associated bone loss. We have designed and synthesised methyl 3-O-[1-carboxyethyl]-β-d-galacto
- Bohari, Mohammad H.,Yu, Xing,Kishor, Chandan,Patel, Brijesh,Go, Rob Marc,Eslampanah Seyedi, Hadieh A.,Vinik, Yaron,Grice, I. Darren,Zick, Yehiel,Blanchard, Helen
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p. 1664 - 1672
(2018/08/01)
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- Chemoenzymatic Synthesis of Advanced Intermediates for Formal Total Syntheses of Tetrodotoxin
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Advanced intermediates for the syntheses of tetrodotoxin reported by the groups of Fukuyama, Alonso, and Sato were prepared. Key steps include the toluene dioxygenase mediated dihydroxylation of either iodobenzene or benzyl acetate. The resulting diene diols were transformed into Fukuyama's intermediate in six steps, into Alonso's intermediate in nine steps, and into Sato's intermediate in ten steps.
- Baidilov, Daler,Rycek, Lukas,Trant, John F.,Froese, Jordan,Murphy, Brennan,Hudlicky, Tomas
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supporting information
p. 10994 - 10998
(2018/06/04)
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- A Natural Lipotrisaccharide and Its Derivatives Selectively Lyse Streptococcus pneumoniae via Interaction with Cell Membrane
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A natural lipotrisaccharide (NP000778, 1a), a new triglycosidic tri-O-substituted glycolipid isolated from the Morinda citrifolia plant, and its chemical derivatives were identified to be active against major Gram-positive pathogens, particularly Streptococcus pneumoniae. Additional evidence indicated that 1a and its synthetic derivatives exerted their bactericidal activities against S. pneumoniae by selectively targeting the bacterial membrane, leading to the rapid lysis of the pneumococci. Efficient synthesis of 1a and its derivatives was performed using an application of the intramolecular aglycon delivery (IAD) reaction to establish its structure-activity relationships (SARs). SAR analysis indicated that trisaccharide glycolipid compounds showed good selectivity and high potency against S. pneumoniae. These compounds contain a linear chain with a chain length from C3 to C9 at the 2-position (R1) and 4′-position (R3), as well as a 2-methyl butyryl group at the 3′-position (R2), without an aza substitution in the lipid chain. This is the first lipotrisaccharide identified with potent bactericidal activity via interaction with cell membrane. The results reported herein offer a valuable guideline for the design of glycolipid derivatives that selectively target pathogenic bacteria.
- Liu, Bo,Liu, Xue,Zhang, Jing-Ren,Liu, Gang
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p. 438 - 453
(2017/06/14)
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- Co2(CO)6-propargyl cation mediates glycosylation reaction by using thioglycoside
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We discovered that the cobalt-propargyl cation can mediate the glycosylation reaction by activating the thioglycoside donor. The glyco-oxacarbenium cation was formed by transferring the thio-aglycone to the cobalt-propargyl cation that was generated from the cobalt-propargylated acceptor in situ via the activating with Lewis acid. The reactivity of the donor (Armed or dis-armed) and the amount of the Lewis acid control the releasing rate of the cobalt-propargyl group.
- Xia, Meng-jie,Yao, Wang,Meng, Xiang-bao,Lou, Qing-hua,Li, Zhong-jun
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supporting information
p. 2389 - 2392
(2017/05/29)
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- A process for preparing 3 - deoxy phenyl C - aminoglycoside SGLT2 inhibitor preparation method and intermediate (by machine translation)
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The invention belongs to the field of medical technology, in particular to a 3 - deoxy phenyl C - aminoglycoside SGLT2 inhibitor can be industrialized preparation method, and the method relates to a key intermediate and its preparation method. The method relates to compounds 10 alkyl lithium reagent processing, with compound 9 reaction to obtain the addition product; in the acid-catalyzed reaction with methanol to obtain compound 11; compound 11 obtained compound 12, to obtain the target compound, the method has suitable for large-scale industrial characteristics. (by machine translation)
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Paragraph 0049-0053
(2017/09/21)
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- Synthesis and binding affinity analysis of α1-2- and α1-6-O/S-linked dimannosides for the elucidation of sulfur in glycosidic bonds using quartz crystal microbalance sensors
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The role of sulfur in glycosidic bonds has been evaluated using quartz crystal microbalance methodology. Synthetic routes towards α1-2- and α1-6-linked dimannosides with S- or O-glycosidic bonds have been developed, and the recognition properties assessed in competition binding assays with the cognate lectin concanavalin A. Mannose-presenting QCM sensors were produced using photoinitiated, nitrene-mediated immobilization methods, and the subsequent binding study was performed in an automated flow-through instrumentation, and correlated with data from isothermal titration calorimetry. The recorded Kd-values corresponded well with reported binding affinities for the O-linked dimannosides with affinities for the α1-2-linked dimannosides in the lower micromolar range. The S-linked analogs showed slightly disparate effects, where the α1-6-linked analog showed weaker affinity than the O-linked dimannoside, as well as positive apparent cooperativity, whereas the α1-2-analog displayed very similar binding compared to the O-linked structure.
- Norberg, Oscar,Wu, Bin,Thota, Niranjan,Ge, Jian-Tao,Fauquet, Germain,Saur, Ann-Kathrin,Aastrup, Teodor,Dong, Hai,Yan, Mingdi,Ramstr?m, Olof
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- Highly Regioselective Monoacylation of Unprotected Glucopyranoside Using Transient Directing-Protecting Groups
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The regioselective functionalization of monosaccharides is notoriously achieved using metal catalysis, lengthy synthetic strategies requiring protection/deprotection, various enzymes, or other methods that target cis-diols (and thus cannot be used with glucopyranose derivatives), In this paper, we report a new method using selected boronic acids as temporary protecting groups, and describe its application to the regioselective functionalization of methyl α-d-glucopyranoside, the most difficult monosaccharide to functionalize regioselectively. Generally, reactions of glucopyranosides may lead to a plethora of mono- and polyfunctionalized derivatives, yet our method gave the 3-O-acetylated, 2-O-benzoylated, and 2-O-pivaloylated derivatives of methyl α-d-glucopyranoside as major products. We focused on the use of recyclable and green temporary protecting groups (in a one-pot reaction) and on the modulation of the intramolecular hydrogen-bonding network using selected arylboronic acids. A complete scalable procedure leading to a single regioisomer from unprotected methyl α-d-glucopyranoside is presented.
- Rocheleau, Sylvain,Pottel, Joshua,Huski?, Igor,Moitessier, Nicolas
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p. 646 - 656
(2017/02/05)
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- Synthesis of MeON-neoglycosides of digoxigenin with 6-deoxy- and 2,6-dideoxy-D-glucose derivatives and their anticancer activity
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Cardiac glycosides show anticancer activities and their deoxy-sugar chains are vital for their anticancer effects. In order to study the structure-activity relationship (SAR) of cardiac glycosides toward cancers and get more potent anticancer agents, a series of MeON-neoglycosides of digoxigenin was synthesized and evaluated. First, ten 6-deoxy- and 2,6-dideoxy-D-glucopyranosyl donors were synthesized starting from methyl α-D-glucopyranoside and 2-deoxy-D-glucose. Meanwhile, the digoxigenin was obtained by acidic hydrolysis of commercially available digoxin as glycosyl acceptor. Then, a 22-member MeON-neoglycoside library of digoxigenin was successfully synthesized by neoglycosylation method. Finally, the induction of Nur77 expression and its translocation from the nucleus to cytoplasm together with cytotoxicity of these MeON-neoglycosides were evaluated. The SAR analysis revealed that C3 glycosylation is required for their induction of Nur77 expression. Moreover, some MeON-neoglycosides (2b and 8b) could significant induce the expression of Nur77 and its translocation from the nucleus to cytoplasm. However, these compounds showed no inhibitory effects on the proliferation of cancer cells, suggesting that they may not induce apoptosis of NIH-H460 cancer cells and their underlying potential and application toward cancer cells deserves future study.
- Wang, Dong-dong,Li, Xiao-san,Bao, Yu-zhou,Liu, Jie,Zhang, Xiao-kun,Yao, Xin-sheng,Sun, Xue-Long,Tang, Jin-Shan
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supporting information
p. 3359 - 3364
(2017/07/07)
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- From organocatalysed desilylations to high-yielding benzylidenations of electron-deficient benzaldehydes
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A new type of organoprecatalyst (MeSCH2Cl/KI) for desilylation and benzylidenation reactions has been designed. Both reactions are user friendly and high yielding (71->99%) and have fast reaction rates. The desilylation of iodo silyl ethers was achieved with no sequential etherification side reactions like those seen for reactions when using TBAF. In the application of the catalytic system to a 6-TBDMS ether of a glucoside, glucoside benzylidenations using electron-deficient benzaldehydes were achieved in 87% yield compared with the previously reported yields of 69-77%. Altogether, 14 benzylidenation reactions were realised using silyloxy alcohols and electrondeficient benzaldehydes instead of their activated acetal forms. In terms of reaction rates and yields, the order of the benzylidenations is p-fluorobenzaldehyde > benzaldehyde > p-anisaldehyde, and a possible mechanism is discussed. These experiments have preliminarily differentiated this cost-effective catalytic system from the classic Lewis acids.
- Niu, Qun,Xing, Linlin,Li, Chunbao
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p. 358 - 364
(2017/06/19)
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- Practical preparation of mono- and di-O-isopropylidene derivatives of monosaccharides and methyl 4,6-O-benzylidene glycosides from free sugars in a deep eutectic solvent
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Free sugars were rapidly converted into the corresponding di-O-isopropylidene derivatives and methyl O-benzylidene glycosides in excellent yields and purity in a deep eutectic solvent made from choline chloride and malonic acid (ChCl:MA). Reaction conditions were mild; work-up was easy, and further purification was not necessary. Given the inexpensive, nontoxic, and recyclable nature of ChCl:MA, this protocol is environmental friendly.
- Rokade, Sunil M.,Bhate, Prakash M.
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- Aqueous Glycosylation of Unprotected Sucrose Employing Glycosyl Fluorides in the Presence of Calcium Ion and Trimethylamine
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We report a synthetic glycosylation reaction between sucrosyl acceptors and glycosyl fluoride donors to yield the derived trisaccharides. This reaction proceeds at room temperature in an aqueous solvent mixture. Calcium salts and a tertiary amine base promote the reaction with high site-selectivity for either the 3′-position or 1′-position of the fructofuranoside unit. Because nonenzymatic aqueous oligosaccharide syntheses are underdeveloped, mechanistic studies were carried out in order to identify the origin of the selectivity, which we hypothesized was related to the structure of the hydroxyl group array in sucrose. The solution conformation of various monodeoxysucrose analogs revealed the co-operative nature of the hydroxyl groups in mediating both this aqueous glycosyl bond-forming reaction and the site-selectivity at the same time.
- Pelletier, Guillaume,Zwicker, Aaron,Allen, C. Liana,Schepartz, Alanna,Miller, Scott J.
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supporting information
p. 3175 - 3182
(2016/03/19)
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- A Synthetic Toolbox for the In Situ Formation of Functionalized Homo- and Heteropolysaccharide-Based Hydrogel Libraries
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A synthetic toolbox for the introduction of aldehydo and hydrazido groups into the polysaccharides hyaluronic acid, alginate, dextran, pullulan, glycogen, and carboxymethyl cellulose and their use for hydrogel formation is reported. Upon mixing differently functionalized polysaccharides derived from the same natural precursor, hydrazone cross-linking takes place, which results in formation of a hydrogel composed of one type of polysaccharide backbone. Likewise, hydrogels based on two different polysaccharide strands can be formed after mixing the corresponding aldehydo- and hydrazido-modified polysaccharides. A second line of these studies paves the way to introduce a biomedically relevant ligand, namely, the adhesion factor cyclic RGD pentapeptide, by using an orthogonal click reaction. This set of modified polysaccharides served to create a library of hydrogels that differ in the combination of polysaccharide strands and the degree of cross-linking. The different hydrogels were evaluated with respect to their rheological properties, their ability to absorb water, and their cytotoxicity towards human fibroblast cell cultures. None of the hydrogels studied were cytotoxic, and, hence, they are in principal biocompatible for applications in tissue engineering.
- Dibbert, Nick,Krause, Andreas,Rios-Camacho, Julio-Cesar,Gruh, Ina,Kirschning, Andreas,Dr?ger, Gerald
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supporting information
p. 18777 - 18786
(2016/12/26)
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- Benzylidene Acetal Protecting Group as Carboxylic Acid Surrogate: Synthesis of Functionalized Uronic Acids and Sugar Amino Acids
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Direct oxidation of the 4,6-O-benzylidene acetal protecting group to C-6 carboxylic acid has been developed that provides an easy access to a wide range of biologically important and synthetically challenging uronic acid and sugar amino acid derivatives in good yields. The RuCl3-NaIO4-mediated oxidative cleavage method eliminates protection and deprotection steps and the reaction takes place under mild conditions. The dual role of the benzylidene acetal, as a protecting group and source of carboxylic acid, was exploited in the efficient synthesis of six-carbon sialic acid analogues and disaccharides bearing uronic acids, including glycosaminoglycan analogues.
- Banerjee, Amit,Senthilkumar, Soundararasu,Baskaran, Sundarababu
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supporting information
p. 902 - 906
(2016/01/16)
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- A green and convenient method for regioselective mono and multiple benzoylation of diols and polyols
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An efficient method for regioselective benzoylation of diols and polyols was developed. The benzoylation is catalyzed by only 0.2 equiv of benzoate anion in acetonitrile with the addition of a stoichiometric amount of benzoic anhydride under very mild condition, leading to high yields. Compared with all other methods, this method shows particular advantage in regioselective multiple benzoylation of polyols, and in avoiding the use of any metal-based catalysts and any amine bases, which is more environment-friendly.
- Zhang, Xiaoling,Ren, Bo,Ge, Jiantao,Pei, Zhichao,Dong, Hai
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supporting information
p. 1005 - 1010
(2016/02/03)
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- Three Solvent-Free Catalytic Approaches to the Acetal Functionalization of Carbohydrates and Their Applicability to One-Pot Generation of Orthogonally Protected Building Blocks
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Three alternative protocols were developed to carry out the selective installation of acetal groups on carbohydrates and polyols under mildly acidic, solvent-free conditions. One protocol is based on a diol/aldehyde condensation at room temperature, with an acetolysis process serving for the activation of the carbonyl component. A second approach is based on an orthoester-mediated activation of the carbonyl component at high temperature. The third protocol is instead entailing a transacetalation mechanism. Combination of these methods allows a wide set of acetal-protected building blocks to be accessed in short times under very simple experimental conditions working under air. The scope of the latter two approaches was also extended to unusual one-pot synthetic sequences leading to concomitant Fischer glycosidation/acetal protection of reducing sugars.
- Traboni, Serena,Bedini, Emiliano,Giordano, Maddalena,Iadonisi, Alfonso
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p. 3562 - 3572
(2016/01/25)
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- Sugar thiacrown-ether appended calix[4]arene as a selective chemosensor for Fe2+ and Fe3+ ions
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A new fluorescent chemosensor derived from sugar-thiacrown-ether appended calix[4]arene, coupled with pyrene units was designed and synthesized. Upon the addition of Fe2+, or Fe3+, changes were observed in both the fluorescence and absorption spectra. The fluorescence intensities are significantly quenched indicating high selectivity for these two metal ions over other transition metals investigated.
- Ling, Irene,Hashim, Rauzah,Sabah, Karem J.
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p. 88038 - 88044
(2015/11/09)
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- Mild One-Step Synthesis of 4,6-Benzylideneglycopyranosides from Aromatic Aldehydes and Gelation Abilities of the Glucose Derivatives
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We report herein an efficient one-step synthesis of 4,6-benzylidene glycoside derivatives from aromatic aldehydes bearing electron-donating or -withdrawing groups as well as polymerisable monomer groups. Glucose, mannose and galactose derivatives could also be used successfully. Several of the glucose derivatives thus obtained acted as gelators for various solvents, including water. 4-(n-Butoxybenzylidene)glucose derivative 3a produced both a clear squalane gel and a hydrogel at 0.1 wt.-%. Furthermore, 3-(n-butoxybenzylidene)glucose derivative 3i produced a clear organogel and an opaque hydrogel. The critical gelation concentration (CGC) of 3i in squalane was determined to be 0.02 wt.-%, which is one of the lowest CGC values reported so far. The organogels, hydrogels and aqueous solution gels produced from 3a and 3d exhibited thixotropy. The strength and thixotropy of the organo- and hydrogel produced from 3a were estimated by a rheometer. The gel morphologies were observed by field-emission and wet-scanning electron microscopy, and the self-assembly modes were analysed by XRD. We have concluded that super-gelators can be created by this method. An efficient one-step synthesis of 4,6-benzylidene glycosides from aromatic aldehydes under mild conditions has been achieved. Some of the glucose derivatives synthesised by this method produced clear organo- and hydrogels with thixotropic properties. The critical gelation concentrations of the gels were below 0.1 wt.-%.
- Ono, Fumiyasu,Hirata, Osamu,Ichimaru, Keiko,Saruhashi, Koichiro,Watanabe, Hisayuki,Shinkai, Seiji
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supporting information
p. 6439 - 6447
(2015/10/19)
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- Hybridisation potential of 1′,3′-Di-O-methylaltropyranoside nucleic acids
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In further study of our series of six-membered ring-containing nucleic acids, different 1′,3′-di-O-methyl altropyranoside nucleoside analogs (DMANA) were synthesized comprising all four base moieties, adenine, cytosine, uracil and guanine. Following assembly into oligonucleotides (ONs), their affinity for natural oligonucleotides was evaluated by thermal denaturation of the respective duplexes. Data were compared with results obtained previously for both anhydrohexitol (HNAs) and 3′-O-methylated altrohexitol modified ONs (MANAs). We hereby demonstrate that ONs modified with DMANA monomers, unlike some of our previously described analogues with constrained 6-membered hexitol rings, did not improve thermodynamic stability of dsRNA complexes, most probably in view of an energetic penalty when forced in the required 1C4 pairing conformation. Overall, a single incorporation was more or less tolerated or even positive for the adenine congener, but incorporation of a second modification afforded a slight destabilization (except for A), while a fully modified sequence displayed a thermal stability of -0.3°C per modification. The selectivity of pairing remained very high, and the new modification upon incorporation into a DNA strand, strongly destabilized the corresponding DNA duplexes. Unfortunately, this new modification does not bring any advantage to be further evaluated for antisense or siRNA applications.
- Venkatesham, Akkaladevi,Kachare, Dhuldeo,Schepers, Guy,Rozenski, Jef,Froeyen, Mathy,Van Aerschot, Arthur
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p. 4020 - 4041
(2015/05/06)
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- Phase-selective gelators based on closed-chain glucose derivatives: their applications in the removal of dissolved aniline/nitrobenzene, and toxic dyes from contaminated water
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Several effective PSGs have been developed from a series of glucose-based compounds for the removal of aniline and nitrobenzene from their biphasic mixtures with water via a simple shaking strategy at room temperature within 1 min. The morphologies of the gels formed in aniline and nitrobenzene in the absence or presence of a large amount of water have been examined by field emission scanning electron microscopy (FE-SEM). The dominant factors that drive gelation in the case of the gelator and aniline or nitrobenzene have been studied using FT-IR, concentration-dependent 1H NMR, and XRD. Additionally, the efficient purification of toxic dye solutions has been realized by using one of these gelators as the adsorbent in a gel column. And the corresponding xerogel can also be used for efficient dye removal. HPLC and UV/vis spectroscopy provide the quantification means for the estimation of the purification efficacy. The easy-to-implement performance and high removal efficiency of the organic pollutants from water indicate the potential and promising applicability of these organogelators in water purification.
- Zhang, Xin,Song, Jiefang,Ji, Wei,Xu, Ning,Gao, Ning,Zhang, Xuhong,Yu, Haitao
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p. 18953 - 18962
(2015/09/28)
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- Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins' Bicyclic Sugar Moiety
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2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.
- Cachatra, Vasco,Almeida, Andreia,Sardinha, Jo?o,Lucas, Susana D.,Gomes, Ana,Vaz, Pedro D.,Florêncio, M. Helena,Nunes, Rafael,Vila-Vi?osa, Diogo,Calhorda, Maria José,Rauter, Amélia P.
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supporting information
p. 5622 - 5625
(2015/12/01)
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- Glycoporphyrin Catalysts for Efficient C-H Bond Aminations by Organic Azides
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We report herein the synthesis of new glycoporphyrin ligands which bear a glucopyranoside derivative on each meso-aryl moiety of the porphyrin skeleton. The saccharide unit is directly conjugated to the porphyrin or a triazole spacer is placed between the carbohydrate and porphyrin ring. The obtained glycoporphyrin ligands were employed to synthesize cobalt(II), ruthenium(II), and iron(III) complexes which were tested as catalysts of C-H bond aminations by organic azides. Two of the synthesized complexes were very efficient in promoting catalytic reactions, and the results achieved indicated that ruthenium and iron complexes show an interesting complementary catalytic activity in several amination reactions. The eco-friendly iron catalyst displayed very good chemical stability in catalyzing the amination reaction for three consecutive runs without losing catalytic activity. (Chemical Equation Presented).
- Tseberlidis, Giorgio,Zardi, Paolo,Caselli, Alessandro,Cancogni, Damiano,Fusari, Matteo,Lay, Luigi,Gallo, Emma
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supporting information
p. 3774 - 3781
(2015/08/19)
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- Stable analogues of nojirimycin-synthesis and biological evaluation of nojiristegine and manno-nojiristegine
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Two novel iminosugars called nojiristegines, being structural hybrids between nor-tropane alkaloid calystegine and nojirimycins, have been synthesised and found to be stable molecules despite the presence of a hemiaminal functionality. The synthesised iminosugars were evaluated against a panel of glycosidases and the best inhibition (IC50), found against α-glucosidases, was in the micromolar region. The compounds were also evaluated as potential antibiotics but no useful level of activity was observed.
- Viuff, Agnete H.,Besenbacher, Louise M.,Kamori, Akiko,Jensen, Mikkel T.,Kilian, Mogens,Kato, Atsushi,Jensen, Henrik H.
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p. 9637 - 9658
(2015/09/28)
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- A robust synthesis of N-glycolyl muramyl dipeptide via azidonitration/reduction
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A novel synthetic route leading to N-glycolyl muramyl dipeptide (MDP), a bacterial glycopeptide of particular interest in studies of nucleotide-binding oligomerization domain-containing protein 2 (NOD2), is described. The synthetic strategy hinges on the alkylation of benzylidene-protected glucal with 2-bromopropionic acid and thus circumvents a challenging and non-reproducible SN2 step at the C-3 position of glucosamine derivatives. The subsequent sequence includes an azidonitration and an unusual azide reduction/acylation step via an aza ylide/oxaphospholidine intermediate. This approach generates a protected N-glycolyl MDP that can be either subjected to a one-step global deprotection or differentially deprotected to obtain further derivatives.
- Xing, Shuo,Gleason, James L.
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p. 1515 - 1520
(2015/01/30)
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- Exploring glycosylation reactions under continuous-flow conditions
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The industrial development of carbohydrate-based drugs is greatly thwarted by the typical challenges inherent in oligosaccharide synthesis. The practical advantages of continuous-flow synthesis in microreactors (high reproducibility, easy scalability, and fast reaction optimization) may offer an effective support to make carbohydrates more attractive targets for drug-discovery processes. Here we report a systematic exploration of the glycosylation reaction carried out under microfluidic conditions. Trichloroacetimidates and thioglycosides have been investigated as glycosyl donors, using both primary and secondary acceptors. Each microfluidic glycosylation has been compared with the corresponding batch reaction, in order to highlight advantages and drawbacks of microreactors technology. As a significant example of multistep continuous-flow synthesis, we also describe the preparation of a trisaccharide by means of two consecutive glycosylations performed in interconnected microreactors.
- Cancogni, Damiano,Lay, Luigi
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supporting information
p. 2873 - 2878
(2015/01/16)
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- Linearization of carbohydrate derived polycyclic frameworks
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We report easy access to carbohydrate derived diverse tricyclic skeletons which could be beneficial for exploring polyfunctionalized chiral alicycles. The key reaction to assemble a sugar fused tricyclic core is intermolecular tandem esterification and 1,3-dipolar cycloaddition. The framework was elaborated using amide forming reactions, opening of isoxazolidine rings followed by N and O-acylations. The sequences provide distinct, spatially separated and encoded chemical entities that may pave the way to investigate cell functions.
- Singh, Priyanka,Panda, Gautam
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p. 31892 - 31903
(2014/08/18)
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- From d-glucuronic acid to l-iduronic acid derivatives via a radical tandem decarboxylation-cyclization
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A synthesis to l-iduronic derivatives, major components of heparin derived pentasaccharides was accomplished by formal inversion of configuration at C-5 of a d-glucuronic acid derivative through radical formation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic tether at O-4 giving exclusively a bicyclic sugar of l-ido configuration. Oxidation and ring opening of this bicyclic sugar led to a l-iduronate. This method opens the way to short syntheses of pentasaccharidic moiety of Idraparinux and congeners.
- Salamone, Stéphane,Boisbrun, Michel,Didierjean, Claude,Chapleur, Yves
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- A 3,4-trans-fused cyclic protecting group facilitates α-selective catalytic synthesis of 2-deoxyglycosides
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A practical approach has been developed to convert glucals and rhamnals into disaccharides or glycoconjugates with high α-selectivity and yields (77-97 %) using a trans-fused cyclic 3,4-O-disiloxane protecting group and TsOH·H2O (1 mol %) as a catalyst. Control of the anomeric selectivity arises from conformational locking of the intermediate oxacarbenium cation. Glucals outperform rhamnals because the C6 side-chain conformation augments the selectivity.
- Balmond, Edward I.,Benito-Alifonso, David,Coe, Diane M.,Alder, Roger W.,McGarrigle, Eoghan M.,Galan, M. Carmen
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supporting information
p. 8190 - 8194
(2014/08/18)
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