Asymmetric desymmetrization of meso-diols by C₂-symmetric chiral 4-pyrrolidinopyridines

• Hartmut Schedel,
• Keizo Kan,
• Yoshihiro Ueda,
• Kenji Mishiro,
• Keisuke Yoshida,
• Takumi Furuta and
• Takeo Kawabata

Beilstein J. Org. Chem. 2012, 8, 1778–1787, doi:10.3762/bjoc.8.203

• pyrrolidine ring such as 3 were prepared from trans-4-hydroxy-L-proline. These catalysts were found to be moderately effective for the asymmetric desymmetrization of meso-diols [11]. C2-Symmetric PPY-catalyst 4 was found to be effective for the chemo- and regioselective acylation of carbohydrates [12][14][16

Antifreeze glycopeptide diastereomers

• Lilly Nagel,
• Carsten Budke,
• Axel Dreyer,
• Thomas Koop and
• Norbert Sewald

Beilstein J. Org. Chem. 2012, 8, 1657–1667, doi:10.3762/bjoc.8.190

• arginine [11]. Tachibana et al. summarized the essential properties of AFGPs displaying significant antifreeze activity: The disaccharide must be α-glycosidically attached to every threonine; the acetylamino moiety has to be present at the C2 position; the carbohydrates must be galacto-configured; and the

• assembly of the glycopeptides the acetate protecting groups of the carbohydrates were cleaved with 5% hydrazine in DMF followed by the cleavage of the peptide from the resin with 2% aqueous TFA. Subsequently, the peptides were precipitated with cold diethyl ether and the solid residues were purified by

The Amadori rearrangement as glycoconjugation method: Synthesis of non-natural C-glycosyl type glycoconjugates

• Katharina Gallas,
• Gerit Pototschnig,
• Florian Adanitsch,
• Arnold E. Stütz and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2012, 8, 1619–1629, doi:10.3762/bjoc.8.185

• communication. In order to investigate and elucidate their many functions, reliable synthetic methods for the conjugation of carbohydrates to biomolecules are of crucial importance [2]. Several ligation strategies are described in the literature, such as chemical ligation [3], conjugation by means of click

• surfaces (glycosylated surfaces, e.g., “glyco-chips”, gold, polystyrene plates, glass, nanoparticles), or labelling and imaging of carbohydrates (fluorescence markers, biotin, photolabelling) [27][28]. Herein we describe the application of the Amadori rearrangement as a key step for the synthesis of non

Mannose-decorated cyclodextrin vesicles: The interplay of multivalency and surface density in lectin–carbohydrate recognition

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2012, 8, 1543–1551, doi:10.3762/bjoc.8.175

• multivalent interaction with ConA, and the most efficient interaction (i.e., fastest agglutination at lowest concentration) was observed for mannose–adamantane conjugates, in which both the cyclodextrin–adamantane and the lectin–mannose interaction is inherently multivalent. Keywords: carbohydrates

• ; cyclodextrins; lectins; molecular recognition; multivalency; vesicles; Introduction The surface modification of materials with carbohydrates has attracted much attention due to the fact that such materials can be compared to and compatible with the cell surface [1]. The “glycocalyx” is a dense layer on the

• role of oligosaccharides on cell surfaces is the fact that human blood types (A, B, AB and 0) are solely determined by minor changes in the composition of the erythrocyte glycocalyx. Additionally, many biological mechanisms are mediated by multivalent recognition of carbohydrates. For example, lectins

Recyclable fluorous cinchona alkaloid ester as a chiral promoter for asymmetric fluorination of β-ketoesters

• Wen-Bin Yi,
• Xin Huang,
• Zijuan Zhang,
• Dian-Rong Zhu,
• Chun Cai and
• Wei Zhang

Beilstein J. Org. Chem. 2012, 8, 1233–1240, doi:10.3762/bjoc.8.138

• . Introducing one or a few fluorine atoms to biologically interesting molecules can significantly change the physical, chemical and biological properties [1][2]. The significant amount of publications on fluorinated small molecules, amino acids, carbohydrates, steroids and nucleosides indicates that

Synthesis of 4” manipulated Lewis X trisaccharide analogues

• Christopher J. Moore and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2012, 8, 1134–1143, doi:10.3762/bjoc.8.126

• modifying this residue, particularly at O-4, may lead to the complete loss of this cross-reactivity [15]. Currently, it is not known what the reason for this observed loss of binding is, since the binding affinities between proteins and carbohydrates are the result of a combination of factors [25][26][27

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• hydrogen bonds. Keywords: aryl glycosides; carbohydrates; transition-metal complex; tricarbonyl(arene)chromium; Introduction In 1957, Fischer and Öfele published the preparation of tricarbonyl(η6-benzene)chromium, which was the first arene tricarbonylchromium complex [1]. Since then, a plethora of

The use of glycoinformatics in glycochemistry

• Thomas Lütteke

Beilstein J. Org. Chem. 2012, 8, 915–929, doi:10.3762/bjoc.8.104

• that can be of use to glycobiologists, but also to chemists who work on the synthesis or analysis of carbohydrates. This article gives an overview of existing glyco-specific databases and tools, with a focus on their application to glycochemistry: Databases can provide information on candidate glycan

• structures for synthesis, or on glyco-enzymes that can be used to synthesize carbohydrates. Statistical analyses of glycan databases help to plan glycan synthesis experiments. 3D-Structural data of protein–carbohydrate complexes are used in targeted drug design, and tools to support glycan structure analysis

• aid with quality control. Specific problems of glycoinformatics compared to bioinformatics for genomics or proteomics, especially concerning integration and long-term maintenance of the existing glycan databases, are also discussed. Keywords: carbohydrates; databases; glycomics; software

High-affinity multivalent wheat germ agglutinin ligands by one-pot click reaction

• Henning S. G. Beckmann,
• Heiko M. Möller and
• Valentin Wittmann

Beilstein J. Org. Chem. 2012, 8, 819–826, doi:10.3762/bjoc.8.91

• enhancements of the multivalent ligands with their ability to bind to the protein in a chelating mode. The best WGA ligand is a trivalent cluster with an IC50 value of 220 nM. Calculated per mol of contained chitobiose, this is the best WGA ligand known so far. Keywords: carbohydrates; click chemistry

Synthetic glycopeptides and glycoproteins with applications in biological research

• Ulrika Westerlind

Beilstein J. Org. Chem. 2012, 8, 804–818, doi:10.3762/bjoc.8.90

• - or oligosaccharides. The glycoprotein saccharides contribute physiochemical properties, influencing protein conformation or increasing stability against proteolytic activity. With their unique structural diversity and complexity, carbohydrates attached on proteins or lipids are involved in numerous

• mutant or a high-mannose oxazoline donor and an Endo-A mutant, two different homogenous glycoproteins 40 and 41 were formed (Scheme 7) [87]. Glycopeptide binding events Carbohydrates on proteins and lipids play critical roles in cell–cell and cell–external-agent binding events. Efforts in the preparation

• of diverse carbohydrate structures immobilized in a microarray format have made carbohydrates accessible for numerous functional studies of protein-binding recognition [90][91][92]. In addition to the glycan structure, multivalency and orientation are important for the presentation of glycan ligands

An easily accessible sulfated saccharide mimetic inhibits in vitro human tumor cell adhesion and angiogenesis of vascular endothelial cells

• Grazia Marano,
• Claas Gronewold,
• Martin Frank,
• Anette Merling,
• Christian Kliem,
• Sandra Sauer,
• Manfred Wiessler,
• Eva Frei and
• Reinhard Schwartz-Albiez

Beilstein J. Org. Chem. 2012, 8, 787–803, doi:10.3762/bjoc.8.89

• (hydroxymethyl)furan and benzoylated galactose imidate, is nontoxic and antagonizes cell physiological processes in vitro that are important for the dissemination and growth of tumor cells in vivo. Keywords: angiogenesis; biomimetic synthesis; carbohydrates; in silico blind docking; melanoma cells

• -adhesive properties showed that 3,4-bis{[(β-D-galactopyranosyl)oxy]methyl}furan (BGF) could inhibit the adhesion of murine B16F10 melanoma cells to several ECM-proteins [15]. Probably, more important than uncharged saccharides are carbohydrates that contain acidic residues, such as sialic acids or sulfated

Sonogashira–Hagihara reactions of halogenated glycals

• Dennis C. Koester and
• Daniel B. Werz

Beilstein J. Org. Chem. 2012, 8, 675–682, doi:10.3762/bjoc.8.75

• substituent in position 2. Keywords: C-glycosides; enyne; glycals; reductive/oxidative refunctionalization; Sonogashira–Hagihara reaction; Introduction Carbohydrates are key players in a plethora of biological processes, such as cell-development, metastasis, cell–cell aggregation and viral infection [1][2

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• samarium diiodide leading to enantiopure acyclic aminopolyols. We also report on our attempts to convert these compounds into enantiopure hydroxylated pyrrolidine derivatives. Keywords: aminopolyols; carbohydrates; chiral auxiliaries; lithiated alkoxyallenes; 1,2-oxazines; pyrroles; pyrrolidines; samarium

• diastereoselectivity [9]. We previously reported on the unusually diverse synthetic potential of carbohydrate-derived 1,2-oxazines allowing the smooth and flexible preparation of various highly functionalised compounds, including de novo syntheses of carbohydrates and their mimetics, as well as N-heterocycles [10][11

2-Allylphenyl glycosides as complementary building blocks for oligosaccharide and glycoconjugate synthesis

• Hemali D. Premathilake and
• Alexei V. Demchenko

Beilstein J. Org. Chem. 2012, 8, 597–605, doi:10.3762/bjoc.8.66

• efficient oligosaccharide assembly. Keywords: carbohydrates; glycosylation; leaving group; oligosaccharides; orthogonal strategy; selective activation; Introduction Current knowledge about the key roles of carbohydrates is still limited. However, thanks to the explosive growth of the field of glycobiology

• in recent years, we have already learned that carbohydrates are involved in a broad range of vital biological processes (e.g., fertilization, anti-inflammation, immunoresponse, joint lubrication, antigenic determination) [1]. Carbohydrates are also involved in many harmful processes (e.g., bacterial

Synthesis of fluorinated maltose derivatives for monitoring protein interaction by ¹⁹F NMR

• Michaela Braitsch,
• Hanspeter Kählig,
• Georg Kontaxis,
• Michael Fischer,
• Toshinari Kawada,
• Robert Konrat and
• Walther Schmid

Beilstein J. Org. Chem. 2012, 8, 448–455, doi:10.3762/bjoc.8.51

• carbohydrates to the maltose-binding protein, which were found to be in perfect agreement with published X-ray data. The results of the NMR competition experiments together with the established correlation between 19F chemical shift data and molecular interaction patterns, suggest valuable applications for

Synthesis of heteroglycoclusters by using orthogonal chemoselective ligations

• Baptiste Thomas,
• Michele Fiore,
• Isabelle Bossu,
• Pascal Dumy and
• Olivier Renaudet

Beilstein J. Org. Chem. 2012, 8, 421–427, doi:10.3762/bjoc.8.47

• combinations of carbohydrates. By using both oxime ligation and copper(I)-catalyzed alkyne–azide cycloaddition, two series of compounds bearing binary combinations of αMan, αFuc or βLac in an overall tetravalent presentation, and either 2:2 or 3:1 relative proportions, have been prepared. Keywords

• : chemoselective ligation; click chemistry; cyclopeptide; heteroglycocluster; oxime; Introduction Multivalent interactions between carbohydrates and proteins play key roles in diverse biological events, including fertilization, cell–cell communication, host–pathogen interactions, immune response and cancer

• reacted with aminooxy glycosyls 1–3a and propargyl glycosides 1–3b. Twelve novel oxime and triazole linked-heteroglycoclusters displaying well-defined distributions and combinations of carbohydrates were thus obtained in excellent yields and purity. Experimental Standard procedures for the

Synthesis in the glycosciences II

• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2012, 8, 411–412, doi:10.3762/bjoc.8.45

• . Expertise and rational planning have allowed the utilization of carbohydrates in stereoselective synthesis and the employment of enzymes in oligosaccharide synthesis. Analytical and pharmacological knowhow have disclosed polysaccharide and glycoconjugate structures, their biological effects and their

• biology in living systems. For this endeavour, chemical, biological and physical concepts and experiments have been equally important and equally challenging. In addition computer-aided methods, such as molecular dynamics studies of carbohydrates and glycoconjugates, have added valuable information about

Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays

• Ian Cumpstey,
• Jens Frigell,
• Elias Pershagen,
• Tashfeen Akhtar,
• Elena Moreno-Clavijo,
• Inmaculada Robina,
• Dominic S. Alonzi and
• Terry D. Butters

Beilstein J. Org. Chem. 2011, 7, 1115–1123, doi:10.3762/bjoc.7.128

• ]. Reports of Mitsunobu reactions of secondary alcohols in fully functionalized carbohydrates are much scarcer. Rather, reports exist of failed attempts at Mitsunobu reactions of secondary carbohydrate alcohols [23] or the selective functionalisation of primary carbohydrate alcohols in the presence of

• secondary alcohols [24]. Some examples of successful reactions do exist, though, for oxygen, nitrogen and sulfur nucleophiles [25][26][27][28]. Unsaturated carbohydrates, similar to those described here, have also been reported to undergo Mitsunobu reaction with simple, non-carbohydrate nucleophiles [29][30

Metathesis access to monocyclic iminocyclitol-based therapeutic agents

• Ileana Dragutan,
• Valerian Dragutan,
• Carmen Mitan,
• Hermanus C.M. Vosloo,
• Lionel Delaude and
• Albert Demonceau

Beilstein J. Org. Chem. 2011, 7, 699–716, doi:10.3762/bjoc.7.81

• the synthesis of naturally occurring iminocyclitols and in their structural modification. Consequently, efficient and stereoselective synthetic routes have been developed, often starting from an inexpensive chiral-pool of precursors, in particular carbohydrates that share structural features with

• ) (129) a natural iminosugar present in buckwheat (widely used in traditional recipes) is an efficient agent for preventing sharp blood glucose peaks after the intake of refined carbohydrates and for positively influencing intestinal microbiota by favouring adhesion of probiotics. It is supposed that

Synthesis of glycoconjugate fragments of mycobacterial phosphatidylinositol mannosides and lipomannan

• Benjamin Cao,
• Jonathan M. White and
• Spencer J. Williams

Beilstein J. Org. Chem. 2011, 7, 369–377, doi:10.3762/bjoc.7.47

• recently refined by the Kováč group [49] for the attachment of amine-derivatized carbohydrates to carrier proteins has particular advantages over other linker methodologies as diethyl squarate is commerically available and exhibits good selectivity in each coupling step, with the intermediate squaramate

Synthesis and self-assembly of 1-deoxyglucose derivatives as low molecular weight organogelators

• Guijun Wang,
• Hao Yang,
• Sherwin Cheuk and
• Sherman Coleman

Beilstein J. Org. Chem. 2011, 7, 234–242, doi:10.3762/bjoc.7.31

• into 3-dimensional networks. The resulting gels may find applications as soft materials for drug delivery, enzyme immobilization, scaffolds for tissue engineering, etc. [10][11][12][13][14]. The structures of LMWGs span a diverse range; carbohydrates have frequently been used in the synthesis of LMWGs

Carbasugar analogues of galactofuranosides: α-O-linked derivatives

• Jens Frigell and
• Ian Cumpstey

Beilstein J. Org. Chem. 2010, 6, 1127–1131, doi:10.3762/bjoc.6.129

• major factor in explaining the generally low reactivity of carbohydrates (at non-anomeric positions) in SN2 reactions. Carbapyranose 1,2-epoxides with α-gluco 3 and α-galacto configurations did not give such good results. With amine nucleophiles, attack was often unregioselective [15]: attack at C1

Preparation of aminoethyl glycosides for glycoconjugation

• Robert Šardzík,
• Gavin T. Noble,
• Martin J. Weissenborn,
• Andrew Martin,
• Simon J. Webb and
• Sabine L. Flitsch

Beilstein J. Org. Chem. 2010, 6, 699–703, doi:10.3762/bjoc.6.81

• aminoethyl glycosides of cell-surface carbohydrates, which are important intermediates for glycoarray synthesis, is described. A set of protocols was developed which provide these intermediates, in a short number of steps, from commercially available starting materials. Keywords: aminoethyl glycosides

• ; glycoarrays; glycoconjugation; glycosylation; Introduction The chemical conjugation of carbohydrates through the anomeric centre to biomolecules such as peptides, proteins, lipids, metabolites and to array surfaces is an important synthetic challenge [1][2][3][4][5]. A diverse range of linkers and spacers

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

• Fabian Pfrengle and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2010, 6, No. 75, doi:10.3762/bjoc.6.75

• ketones. This strategy allowed a simple access to unusual carbohydrates with C2-branched 4-amino sugar units and related carbohydrate mimetics [3][4][5][6][7]. Moreover, pursuing a similar strategy, we described the stereocontrolled preparation of 3,6-dihydro-2H-pyrans D as precursors for the synthesis of

• with high structural similarities to carbohydrates. Reduction of the carbonyl group of 8 by NaBH4 followed by hydrogenolysis of the N,O- and N-benzyl-bonds furnished aminopyran 24 (Scheme 12). Similarly, nitrone 21 was smoothly converted to the diastereomeric aminopyran 26 by analogous reductive

New amphiphilic glycopolymers by click functionalization of random copolymers – application to the colloidal stabilisation of polymer nanoparticles and their interaction with concanavalin A lectin

• Otman Otman,
• Paul Boullanger,
• Eric Drockenmuller and
• Thierry Hamaide

Beilstein J. Org. Chem. 2010, 6, No. 58, doi:10.3762/bjoc.6.58

• enough to allow scale-up. Thus, we elected to use the simplest carbohydrates, i.e., those which are easy to prepare and easy to handle, e.g., the peracetylated monosaccharide 1 [16]. Although other derivatives, such as the 2,3,4,6-tetra-O-acetyl-1-O-trichloroacetimidoyl mannose might give rise to better

• flocculation or precipitation, whereas the suspension should remain unchanged on the addition of “naked” nanoparticles (without any carbohydrate on their surface) or nanoparticles covered with non specific carbohydrates. This increase in size can be observed either by the naked eye, turbidity or fluorescence

• copolymer in order to obtain glycosylated polycaprolactone nanoparticles stable over a long period of storage. The carbohydrates covalently bound to the copolymers are accessible at the surface of the nanoparticles and are available for molecular recognition. The recognition of α-D-mannose at the surface of