Synthesis of α-D-GalpN₃-(1-3)-D-GalpN₃: α- and 3-O-selectivity using 3,4-diol acceptors

• Emil Glibstrup and
• Christian Marcus Pedersen

Beilstein J. Org. Chem. 2018, 14, 2805–2811, doi:10.3762/bjoc.14.258

• Shigella dysenteriae [23], as derivatives of the mucin O-glycan core structures for glycosidase studies [24], for the synthesis of T-antigen analogues [25], for the synthesis of E. coli O-antigens [26][27][28][29], for the development of Burkholderia vaccines [30][31][32], for the synthesis of PS A1

Pathoblockers or antivirulence drugs as a new option for the treatment of bacterial infections

• Matthew B. Calvert,
• Varsha R. Jumde and
• Alexander Titz

Beilstein J. Org. Chem. 2018, 14, 2607–2617, doi:10.3762/bjoc.14.239

• ongoing research [27][28]. Another adhesin of uropathogenic E. coli is FmlH, which is located at the tip of F9 pili and binds β-D-galactosides with moderate potency. It could be shown that this lectin plays an important role in kidney-associated chronic UTIs, as its glycan receptor is abundantly expressed

Synthetic and semi-synthetic approaches to unprotected N-glycan oxazolines

• Antony J. Fairbanks

Beilstein J. Org. Chem. 2018, 14, 416–429, doi:10.3762/bjoc.14.30

• Antony J. Fairbanks Department of Chemistry, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand Biomolecular Interaction Centre, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand 10.3762/bjoc.14.30 Abstract N-Glycan oxazolines have found

• subsequently relied on the Lewis acid catalysed conversion of peracetylated N-glycan oligosaccharides produced in this manner into their corresponding oxazolines, followed by global deprotection. However, a key breakthrough in the field has been the development by Shoda of 2-chloro-1,3-dimethylimidazolinium

• these materials, in concert with DMC-mediated oxazoline formation as a final step, allow access to a selection of N-glycan oxazoline structures both in larger quantities and in a more expedient fashion than is achievable by total synthesis. Keywords: DMC, ENGase; glycosyl oxazolines; N-glycans

What contributes to an effective mannose recognition domain?

• Christoph P. Sager,
• Deniz Eriş,
• Martin Smieško,
• Rachel Hevey and
• Beat Ernst

Beilstein J. Org. Chem. 2017, 13, 2584–2595, doi:10.3762/bjoc.13.255

• Brewer reviewed the role of density and number of glycan epitopes involved in multivalent carbohydrate interactions for legume lectins as well as for lectins of the innate immune system [74]. As an example, HIV-1 establishes multivalent contacts to DC-SIGN (E)-decorated dendritic cells in order to bypass

Preactivation-based chemoselective glycosylations: A powerful strategy for oligosaccharide assembly

• Weizhun Yang,
• Bo Yang,
• Sherif Ramadan and
• Xuefei Huang

Beilstein J. Org. Chem. 2017, 13, 2094–2114, doi:10.3762/bjoc.13.207

• transformations commonly encountered in building block preparation [41]. At the same time, mild promoters are available for thioglycoside activation. The anomeric reactivities of thioglycosides towards glycosylation can be significantly influenced by the protective groups on the glycan ring as well as the size

• synthetic glycan that has ever been produced, highlighting the power of the preactivation-based glycosylation strategy. In addition to Globo-H 105 and arabinogalactan 116, other complex oligosaccharides obtained by the preactivation-based thioglycoside method include branched oligosaccharides from

• oligosaccharides 123 from fungal cells [68][69], oligomannan containing multiple challenging β-mannosyl linkages 124 [54] (Figure 6), chitotetraose [70], mammalian glycans including complex type bisected N-glycan dodecasaccharide 125 [71], glycosaminoglycans including hyaluronic acid oligosaccharides 126 [72][73

Intramolecular glycosylation

• Xiao G. Jia and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2017, 13, 2028–2048, doi:10.3762/bjoc.13.201

• proteins in the human body are glycosylated [3], and cells display a multitude of glycostructures [4]. Since glycan and glycoconjugate biomarkers are present in all body fluids, they offer a fantastic opportunity for diagnostics. Changes in the level of glycans, as well as changes in glycosylation and

1,3-Dibromo-5,5-dimethylhydantoin as promoter for glycosylations using thioglycosides

• Fei-Fei Xu,
• Claney L. Pereira and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2017, 13, 1994–1998, doi:10.3762/bjoc.13.195

• trimethylsilyl trifluoromethanesulfonate (TMSOTf) were employed as co-promoters in solution or automated glycan assembly on solid phase. Keywords: automated glycan assembly; 1,3-dibromo-5,5-dimethylhydantoin; glycosylation; promoter; thioglycosides; Introduction Thioglycosides are versatile glycosylating

• donors [3][6][7][8][9][10][11][12][13][14][15][16][17][18]. However, most of those activators are expensive and toxic [5][17][19]. Poor solubility complicates the use of some promoters during automated glycan assembly [20][21][22][23], while the instability of some activators in solution requires them to

• acetonitrile [45] was used as co-solvent. With all these donors, the α-stereoselectivity increased at higher temperature [46]. Donor 13, containing a remote participating group, produced the disaccharide with better α-selectivity [22][42]. Automated glycan assembly is the most rapid means to access complex

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• example of this powerful methodology has been reported from the Fairbanks group [16] recently. They synthesized a phosphorylated glycoprotein containing a mannose-6-phosphate (M6P)-terminated N-glycan (Scheme 3). Their work combined the chemical synthesis of a phosphotetrasaccharide with the enzymatic

• determined by ESIMS) [80]. Soon after this seminal work appeared, in 2017, Fairbanks and collaborators constructed a 16-mer peptide with a complex bi-antennary N-glycan moiety ligated to the peptide using this thio–ene reaction under very similar conditions [83]. In 2016, the Fairbanks group devised a one

• determine the organic composition [101]. The easiness of this procedure is noteworthy. By simple pH adjustments in a two-step process a functionalized glycan-surface array can be obtained using a fully unprotected saccharide donor under aqueous conditions. 5 In situ activation of the anomeric center In this

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

• of the families of most glycan-interacting proteins (including glycosyl transferases and hydrolases, lectins, antibodies and GAG-binding proteins) are presented. Examples concerned with glycolipids and colloids are also covered as well as some dealing with the structures and multiscale architectures

• recognition with the elucidation of glycosyl hydrolases mechanism by X-ray crystallography, but the scope of applications in glycobiology is much broader: it encompasses the range of glycan containing (macro)-molecules and their conjugates. The present article reviews the application of synchrotron radiation

• glycosylated, whereas proteins expressed in E. coli do not contain any glycan chains. For proteins that require post-translational modification, eukaryotic expression systems are usually preferred [30]. The crystallization of glycoproteins faces several obstacles, including the micro-heterogenity of glycans at

Glyco-gold nanoparticles: synthesis and applications

• Federica Compostella,
• Olimpia Pitirollo,
• Alessandro Silvestri and
• Laura Polito

Beilstein J. Org. Chem. 2017, 13, 1008–1021, doi:10.3762/bjoc.13.100

• Penadès and co-workers [15] is a modified Brust–Shiffrin method [17], based on the in situ Au3+ reduction by means of NaBH4 in the presence of thiol-ending neoglycoconjugates. Following this approach, a rapid synthesis of AuNPs characterized by elevated glycan density on the NP surface and a 1–10 nm

• , the main drawbacks of this protocol are the longer reaction times (12–24 hours), the lower glycan loading and the difficulty for a fine control of the organic shell composition. The last category collects all the protocols based on chemical conjugations of sugar residues to ligands displayed on the

• for the preparation of “multicopy–multivalent” AuNPs, decorated with complex glycan structures. The high degree of ramification resulted in a strong selective recognition [57][58] with the possibility to modulate the glycosylic loading. Even if the carbohydrate loading is important, not always a high

Expression, purification and structural analysis of functional GABA transporter 1 using the baculovirus expression system

• Jing Hu,
• Chris Weise,
• Christoph Böttcher,
• Hua Fan and
• Jian Yin

Beilstein J. Org. Chem. 2017, 13, 874–882, doi:10.3762/bjoc.13.88

• peptides from primary sequence databases with Mascot (http://www.matrixscience.com/). The biological function of recombinant proteins of mammalian origin expressed in insect cells may be altered by different N-glycan status. We observed that the terminal sialic acid residues are essential for the GABA

• but not the terminal trimming of N-glycans is involved in the regulation of the correct membrane glycoprotein folding since the inhibition of N-glycosylation processing by 1-deoxymannojirimycin (dMM) results in a mannose-rich type of N-glycan that does not affect either the protein stability or

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

• Peter H. Seeberger,
• Claney L. Pereira and
• Subramanian Govindan

Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19

• glycosylation of the liberated hydroxy groups. Formation of the β-mannosazide glycoside containing a protected C5 amino linker that serves in the final product as an attachment point for glycan array surfaces or carrier proteins was central to the assembly of trisaccharide 3. To avoid a challenging and often

• (Scheme 1, route B). Building block synthesis. The accessibility of differentially protected monosaccharide building blocks is a prerequisite for the successful total synthesis of any complex glycan. The synthesis of the mannosazide building block was the first challenge to be addressed. Installation of a

• participation groups and solvent effects. It lends further credence to the linear assembly concept in which one monosaccharide unit at a time is incorporated, and which serves as the basis for automated glycan assembly [43]. With the synthetically sourced hexasaccharide repeating unit in hand detailed

Automated glycan assembly of a S. pneumoniae serotype 3 CPS antigen

• Markus W. Weishaupt,
• Stefan Matthies,
• Mattan Hurevich,
• Claney L. Pereira,
• Heung Sik Hahm and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2016, 12, 1440–1446, doi:10.3762/bjoc.12.139

• variability. Herein, we report the first iterative automated glycan assembly (AGA) of a conjugation-ready S. pneumoniae serotype 3 CPS trisaccharide. This oligosaccharide was assembled using a novel glucuronic acid building block to circumvent the need for a late-stage oxidation. The introduction of a washing

• ]. Automated glycan assembly builds on monomeric building blocks that are incorporated during iterative glycosylations [28][29]. Here, a set of building blocks was identified that can be employed interchangeably in the automated syntheses of a wide variety of biologically relevant glycans. To minimize the post

• using Pd(OH)2/C in methanol/water/acetic acid (50:25:1 v/v/v) afforded the fully deprotected S. pneumoniae serotype 3 CPS antigen 11 in 71% yield over three steps (Scheme 5). Conclusion The first automated glycan assembly of a conjugation-ready S. pneumoniae serotype 3 trisaccharide 11 using glucuronic

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• Background: Derivatives of D-glucosamine and D-galactosamine represent an important family of the cell surface glycan components and their fluorinated analogs found use as metabolic inhibitors of complex glycan biosynthesis, or as probes for the study of protein–carbohydrate interactions. This work is

• glycan and glycosaminoglycan biosynthesis [2][3], to inhibit amino sugars processing enzymes [4][5], to probe interactions of amino sugars with their target enzymes and lectins [6][7], or to increase the hydrolytic stability of the glycosidic bond in amino sugar glycosides [8][9]. For example, acetylated

• ]. The resulting disruption of protein–(glycosamino)glycan interactions had important biomedical consequences such as reduced selectin-mediated tumor cell adhesion [12][13], suppressed selectin-mediated leukocyte migration [11][14][15], reduced angiogenesis [3], or inhibition of tumor growth by decreased

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

• Madhuri Vangala and
• Ganesh P. Shinde

Beilstein J. Org. Chem. 2015, 11, 2289–2296, doi:10.3762/bjoc.11.249

• oxacarbenium-ion intermediate by a nitrile and subsequent intramolecular nucleophilic attack of the vicinal C2 ether or a free hydroxy group [32][33][34]. Such glycooxazolines are exploited for the generation of N-glycan structures [35]. In O-glycosylation reactions, an oxacarbenium-ion intermediate interacts

• applied them to the synthesis of α(1→5)-arabinan [38]. Thus, the exploration of carbohydrate-based oxazolines [39][40] has been limited to serve as glycosyl donors or as intermediates for N-glycan synthesis. Although, a few pyranose-based oxazoline frameworks are known [41], the corresponding furanoid

Synthesis and evaluation of the biostability and cell compatibility of novel conjugates of nucleobase, peptidic epitope, and saccharide

• Dan Yuan,
• Xuewen Du,
• Junfeng Shi,
• Ning Zhou,
• Abdulgader Ahmed Baoum,
• Khalid Omar Al Footy,
• Khadija Omar Badahdah and
• Bing Xu

Beilstein J. Org. Chem. 2015, 11, 1352–1359, doi:10.3762/bjoc.11.145

• average width of 10 ± 2 nm in the solution. This result indicates that the introduction of the glycan at the C-terminus of 5 increases the solubility of the nanofibers. The mixture of 7 and 8 also fails to result in a hydrogel. Moreover, the TEM of the solution of 7 + 8 hardly exhibits any ordered

Orthogonal dual-modification of proteins for the engineering of multivalent protein scaffolds

• Michaela Mühlberg,
• Michael G. Hoesl,
• Christian Kuehne,
• Jens Dernedde,
• Nediljko Budisa and
• Christian P. R. Hackenberger

Beilstein J. Org. Chem. 2015, 11, 784–791, doi:10.3762/bjoc.11.88

• carbohydrate ligands to the protein barstar [18]. In the current study, we aimed to extend this approach to the dual modification of proteins using a combination of two chemoselective, orthogonal conjugation reactions for the introduction of glycan ligands and biotin to a protein. Our main objective in this

• successful glycan attachment was provided by tryptic digest and MS/MS-analysis of Gal-3, which showed functionalization of two specific Aha residues (see Table S5 in Supporting Information File 1). It should be noted that higher concentrations of Cu2+ also led to precipitation and loss of protein material

Probing multivalency in ligand–receptor-mediated adhesion of soft, biomimetic interfaces

• Stephan Schmidt,
• Hanqing Wang,
• Daniel Pussak,
• Simone Mosca and
• Laura Hartmann

Beilstein J. Org. Chem. 2015, 11, 720–729, doi:10.3762/bjoc.11.82

• carbohydrates of the glycocalyx, a glycan coating enveloping prokaryotic or eukaryotic cells. By specific binding to cell receptors, the carbohydrate units of the glycocalyx control important processes such as cell adhesion, communication and inflammatory response [1]. For this reason great effort is set forth

DNA display of glycoconjugates to emulate oligomeric interactions of glycans

• Alexandre Novoa and
• Nicolas Winssinger

Beilstein J. Org. Chem. 2015, 11, 707–719, doi:10.3762/bjoc.11.81

• programmability of the assemblies lends itself to a combinatorial display of multiple ligands. Recent efforts in the synthesis and applications of such conjugates are discussed. Keywords: glycan; glycoconjugate; DNA display; multivalency; nucleic acid conjugates; oligomeric interaction; Introduction Cell

• single high-affinity interaction with a target macromolecule, glycans’ interactions with glycan-binding proteins (GPB) or lectins are typically low affinity. However high avidity and specificity is achieved through the concerted interactions of multiple ligands with well-defined spatial geometry [5]. The

• different chemistries used in the glycoconjugations and the different strategies used to display the glycans with DNA templates. Review Glycan–DNA conjugates An initial solution used in the pioneering work of Kobayashi [17] for nucleic acid–glycan conjugation was the chemoselective reaction of p

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• galectin-mediated organization of cell surface glycoconjugates influences glycan dynamics and essential biological processes like signaling [8]. Therefore, in order to advance our understanding of carbohydrate-mediated biological response, we are seeking further molecular architectures that allow us

Automated solid-phase synthesis of oligosaccharides containing sialic acids

• Chian-Hui Lai,
• Heung Sik Hahm,
• Chien-Fu Liang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2015, 11, 617–621, doi:10.3762/bjoc.11.69

• carbohydrate antigens (TACAs) such as the sialyl-Tn antigen (sTn) [2]. Neu5Ac is often the terminal residue and is usually linked via an α-(2,3) or α-(2,6) linkage to galactose (Gal) (Figure 1) [3]. Automated glycan assembly enables rapid access to structurally defined oligosaccharides [4][5] including

• incorporation of sialic acid–galactose disaccharide building blocks [5][11]. Here, we describe a sialic acid building block that can be utilized for automated glycan assembly. Results and Discussion Sialylating oligosaccharides in high yield and α-selectivity was challenging since the presence of a C-1 carboxyl

• these considerations sialyl phosphate building blocks 4 and 5 [14] were selected for automated glycan assembly using monosaccharides (Scheme 1). The synthesis of building block 4 commenced with the placement of a C-9 Fmoc protecting group on thioglycoside 1 [14] to produce 2. Installation of O

Synthesis and biological evaluation of a novel MUC1 glycopeptide conjugate vaccine candidate comprising a 4’-deoxy-4’-fluoro-Thomsen–Friedenreich epitope

• Manuel Johannes,
• Maximilian Reindl,
• Bastian Gerlitzki,
• Edgar Schmitt and
• Anja Hoffmann-Röder

Beilstein J. Org. Chem. 2015, 11, 155–161, doi:10.3762/bjoc.11.15

• tolerance to carbohydrate antigens remains a major obstacle in initiating an effective and long-lasting immune protection against malignancies. One strategy to enhance the immunogenicity of carbohydrate antigens relies upon modification of the glycan hapten [26][27], which renders it more foreign to the

• host [28]. Earlier studies proved that non-natural TACAs can be indeed highly immunogenic [29][30][31][32], although the elicited antibodies often failed to cross-react with the natural glycan. To overcome this drawback, the use of synthetic carbohydrate-based vaccines with TACA analogs [33][34] in

Galactan synthesis in a single step via oligomerization of monosaccharides

• Marius Dräger and
• Amit Basu

Beilstein J. Org. Chem. 2014, 10, 2658–2663, doi:10.3762/bjoc.10.279

• . Additionally, numerous other steps involving protecting group removal and installation are required to assure regio- and stereoselective glycan assembly. One-pot strategies for oligosaccharide synthesis can streamline the process by sequential iterative glycosylations, without the need for work-up and

• and reducing end functionality. Results and Discussion As part of a project on the synthesis of glycan fragments derived from arabinogalactan proteins (AGPs) [17][18], we sought to prepare a β1→6 linked galactan as a chemical probe. We elected to prepare the galactan with a pyrene-containing aglycone

Synthesis and immunological evaluation of protein conjugates of Neisseria meningitidis X capsular polysaccharide fragments

• Laura Morelli,
• Damiano Cancogni,
• Marta Tontini,
• Alberto Nilo,
• Sara Filippini,
• Paolo Costantino,
• Maria Rosaria Romano,
• Francesco Berti,
• Roberto Adamo and
• Luigi Lay

Beilstein J. Org. Chem. 2014, 10, 2367–2376, doi:10.3762/bjoc.10.247

• be enhanced by increasing the number of glycan antigens incorporated onto the carrier protein. The utilization of other conjugation chemistries enabling the achievement of higher carbohydrate loadings and the study of the effect of different glycan–protein ratios on glycoconjugates prepared from

• these short synthetic MenX fragments also deserve further exploration. Experimental General procedure for conjugation of fragments 1–3. This procedure is similar to that reported in reference [27]. The glycan (10 μmol) dissolved in DMSO (250 μL) containing triethylamine (25 equiv), was slowly dropped

Expanding the scope of cyclopropene reporters for the detection of metabolically engineered glycoproteins by Diels–Alder reactions

• Anne-Katrin Späte,
• Verena F. Schart,
• Julia Häfner,
• Andrea Niederwieser,
• Thomas U. Mayer and
• Valentin Wittmann

Beilstein J. Org. Chem. 2014, 10, 2235–2242, doi:10.3762/bjoc.10.232

• ; metabolic oligosaccharide engineering; Introduction The glycan chains of glycoproteins and lipids have been shown to be involved in numerous biological recognition and regulation events [1]. Glycan research, especially the visualization of glycoconjugates in vitro and in vivo, has significantly profited

• bioorthogonal labeling reactions that allow visualization [5][6]. Whereas in the first report on glycan labeling by this approach the ketone–hydrazide ligation was employed [7], later investigations mainly relied on the Staudinger ligation [8] and azide–alkyne [3 + 2] cycloaddition (copper-catalyzed [9][10] or

• -GlcNAcylated proteins). Subsequently, a ligation reaction is performed to visualize the glycan. Synthesis of the cyclopropene-modified hexosamine derivatives 1 and 2. Labeling strategy for metabolically incorporated monosaccharides. Supporting Information Additional MOE experiments and 1H and 13C NMR spectra