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101.
Synthesis of Chlamydia Lipopolysaccharide Haptens through the use of α‐Specific 3‐Iodo‐Kdo Fluoride Glycosyl Donors 下载免费PDF全文
Barbara Pokorny Prof. Paul Kosma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):305-313
A scalable approach towards high‐yielding and (stereo)selective glycosyl donors of the 2‐ulosonic acid Kdo (3‐deoxy‐D ‐manno‐oct‐2‐ulosonic acid) is a fundamental requirement for the development of vaccines against Gram‐negative bacteria. Herein, we disclose a short synthetic route to 3‐iodo Kdo fluoride donors from Kdo glycal esters that enable efficient α‐specific glycosylations and significantly suppress the elimination side reaction. The potency of these donors is demonstrated in a straightforward, six‐step synthesis of a branched Chlamydia‐related Kdo‐trisaccharide ligand without the need for protecting groups at the Kdo glycosyl acceptor. The approach was further extended to include sequential iteration of the basic concept to produce the linear Chlamydia‐specific α‐Kdo‐(2→8)‐α‐Kdo‐(2→4)‐α‐Kdo trisaccharide in a good overall yield. 相似文献
102.
Synthesis of High‐Mannose Oligosaccharide Analogues through Click Chemistry: True Functional Mimics of Their Natural Counterparts Against Lectins? 下载免费PDF全文
Dr. Marc François‐Heude Dr. Alejandro Méndez‐Ardoy Dr. Virginie Cendret Dr. Pierre Lafite Prof. Richard Daniellou Prof. Carmen Ortiz Mellet Prof. José M. García Fernández Dr. Vincent Moreau Prof. Florence Djedaïni‐Pilard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(5):1978-1991
Terminal “high‐mannose oligosaccharides” are involved in a broad range of biological and pathological processes, from sperm‐egg fusion to influenza and human immunodeficiency virus infections. In spite of many efforts, their synthesis continues to be very challenging and actually represents a major bottleneck in the field. Whereas multivalent presentation of mannopyranosyl motifs onto a variety of scaffolds has proven to be a successful way to interfere in recognition processes involving high‐mannose oligosaccharides, such constructs fail at reproducing the subtle differences in affinity towards the variety of protein receptors (lectins) and antibodies susceptible to binding to the natural ligands. Here we report a family of functional high‐mannose oligosaccharide mimics that reproduce not only the terminal mannopyranosyl display, but also the core structure and the branching pattern, by replacing some inner mannopyranosyl units with triazole rings. Such molecular design can be implemented by exploiting “click” ligation strategies, resulting in a substantial reduction of synthetic cost. The binding affinities of the new “click” high‐mannose oligosaccharide mimics towards two mannose specific lectins, namely the plant lectin concanavalin A (ConA) and the human macrophage mannose receptor (rhMMR), have been studied by enzyme‐linked lectin assays and found to follow identical trends to those observed for the natural oligosaccharide counterparts. Calorimetric determinations against ConA, and X‐ray structural data support the conclusion that these compounds are not just another family of multivalent mannosides, but real “structural mimics” of the high‐mannose oligosaccharides. 相似文献
103.
104.
《Magnetic resonance in chemistry : MRC》2002,40(3):169-174
A 3D 1H–13C–1H refocused INEPT transfer experiment is proposed in which the initial coherence transfer of 1H longitudinal to 13C transverse magnetization is tuned to the long‐range 1H, 13C couplings while the reverse INEPT component transfers the magnetization to the directly bonded 1H. Integration of a constant time 1H evolution period into the long‐range coherence transfer interval provides absorption mode signals for each dimension. A 13C purge component at the beginning of the sequence selects for 12C‐bound 1H magnetization that is then transferred to a 13C‐bound hydrogen, thus strongly suppressing the diagonal signals. This experiment is expected to be of particular value for situations in which resonance overlap in the 13C dimension renders 2D long‐range heteronuclear correlation data ambiguous. In combination with a diagonal‐suppressed 3D 1H–13C–1H TOCSY‐HSQC experiment, complete assignment of the ring resonances of the Lewis‐b hexasaccharide was obtained on a 4.2 mM sample using a conventional 500 MHz probe (0.1% ethylbenzene signal‐to‐noise ratio of 600), suggesting its applicability to sub‐millimolar samples using cryoprobe technology. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
105.
Reagent‐Controlled α‐Selective Dehydrative Glycosylation of 2,6‐Dideoxy‐ and 2,3,6‐Trideoxy Sugars 下载免费PDF全文
Dr. Jason M. Nogueira Marissa Bylsma Danielle K. Bright Prof. Clay S. Bennett 《Angewandte Chemie (International ed. in English)》2016,55(34):10088-10092
We have found that activating either 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropenone or 2,3‐bis(2,3,4‐trimethoxyphenyl)cyclopropene‐1‐thione with oxalyl bromide results in the formation of a species that promotes the glycosylation between 2,6‐dideoxy‐sugar hemiacetals and glycosyl acceptors in good yield and high α‐selectivity. Both reactions are mild and tolerate a number of sensitive functional groups including highly acid‐labile 2,3,6‐trideoxy‐sugar linkages. 相似文献
106.
Klajnert B Appelhans D Komber H Morgner N Schwarz S Richter S Brutschy B Ionov M Tonkikh AK Bryszewska M Voit B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(23):7030-7041
Maltose-modified poly(propylene imine) (PPI) dendrimers were synthesized by reductive amination of unmodified second- to fifth-generation PPI dendrimers in the presence of excess maltose. The dendrimers were characterized by using (1)H NMR, (13)C NMR, and IR spectroscopies; laser-induced liquid beam ionization/desorption mass spectrometry; dynamic light scattering analyses; and polyelectrolyte titration. Their scaffolds have enhanced molecular rigidity and their outer spheres, at which two maltose units are bonded to the former primary amino groups on the surface, have hydrogen-bond-forming properties. Furthermore, the structural features reveal the presence of a dense shell. Experiments involving encapsulation (1-anilinonaphthalene-8-sulfonic acid) and biological properties (hemolysis and interactions with human serum albumin (HSA) and prion peptide 185-208) were performed to compare the modified with the unmodified dendrimers. These experiments gave the following results: 1) The modified dendrimers entrapped a low-molecular-weight fluorescent dye by means of a dendritic box effect, in contrast to the interfacial uptake characteristic of the unmodified PPI dendrimers. 2) Both low- and high-generation dendrimers containing maltose units showed markedly reduced toxicity. 3) The desirable features of bio-interactions depended on the generation of the dendrimer; they were retained after maltose substitution, but were now mainly governed by nonspecific hydrogen-bonding interactions involving the maltose units. The modified dendrimers interacted with HSA as strongly as the parent compounds and appeared to have potential use as antiprion agents. These improvements will initiate the development of the next platform of glycodendrimers in which apparently contrary properties can be combined, and this will enable, for example, therapeutic products such as more efficient and less toxic antiamyloid agents to be synthesized. 相似文献
107.
Yi Zheng Jingyu Yan Cuiyan Cao Yanfang Liu Dongping Yu Xinmiao Liang 《Journal of separation science》2023,46(18):2300368
Polysaccharides are widely distributed in natural sources from monocytic microorganisms to higher animals, and are found in a variety of biological activities in recent decades. Natural polysaccharides have the characteristics of large molecular weight, diverse composition, and complex structure, so their purification and structural analysis are difficult issues in research. Chromatography as a powerful separation technique, plays an irreplaceable role in the separation and structural analysis of natural polysaccharides, especially in the purification of polysaccharides, the separation of hydrolysates, and the analysis of monosaccharide composition. The separation mechanisms and application of different chromatographic methods in the studies of polysaccharides were summarized in this review. Moreover, the advantages and drawbacks of various chromatography methods were discussed as well. 相似文献
108.
Dr. Somayeh Ahadi Dr. Shahid I. Awan Prof. Dr. Daniel B. Werz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6264-6270
A general and efficient strategy for synthesis of tri-, hexa- and heptasaccharidic substructures of the lipopolysaccharide of Providencia rustigianii O34 is described. For the heptasaccharide seven different building blocks were employed. Special features of the structures are an α-linked galactosamine and the two embedded α-fucose units, which are either branched at positions-3 and -4 or further linked at their 2-position. Convergent strategies focused on [4+3], [3+4], and [4+2+1] couplings. Whereas the [4+3] and [3+4] coupling strategies failed the [4+2+1] strategy was successful. As monosaccharidic building blocks trichloroacetimidates and phosphates were employed. Global deprotection of the fully protected structures was achieved by Birch reaction. 相似文献
109.
Wonmin Choi Dr. Hao Sun Dr. Claudia Battistella Dr. Or Berger Maria A. Vratsanos Max M. Wang Prof. Dr. Nathan C. Gianneschi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(45):19930-19940
In this Minireview, we describe synthetic polymers densely functionalized with sequence-defined biomolecular sidechains. We focus on synthetic brush polymers of oligonucleotides, oligosaccharides, and oligopeptides, prepared via graft-through polymerization from biomolecule functionalized monomers. The resulting structures are brush polymers wherein a biomolecular graft is positioned at each monomer backbone unit. We describe key synthetic milestones, identify synthetic opportunities, and highlight recent advances in the field, including biological applications. 相似文献
110.