Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

• Patrick Claude,
• Christian Lehmann and
• Thomas Ziegler

Beilstein J. Org. Chem. 2011, 7, 1609–1619, doi:10.3762/bjoc.7.189

• leaving group [5][6][7][8][9]. In the “aglycon-delivery concept”, the glycosyl acceptor is attached to a labile acetal [10][11][12][13][14] or silylene group [15][16][17], which is cleaved and the glycosyl acceptor is “delivered” to the anomeric center upon its activation. In the “prearranged-glycoside

• intramolecular, ring-closing condensation occurs affording a tethered saccharide (Figure 1). Despite the fact that the “prearranged-glycoside concept” for intramolecular glycosylation has been successfully applied to the construction of glycosidic bonds that are otherwise difficult to establish (i.e., β-D

• the prearranged glycoside 5a, only the β(1→3)-linked product 6a (50%) and the α(1→3)-linked product 7a (6%) were obtained upon intramolecular glycosylation, forming an 18-membered macrocyclic ring. No (1→2)-linked disaccharides 8 were detected. The structures of 6a and 7a were unambiguously assigned

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• glycoside in high yield. Keywords: diarrhea; glycosylation; O-antigen; oligosaccharide; Shigella boydii; Introduction Diarrhoeal disease is a common cause of death in the tropical countries and it is the second mostly causing infant deaths worldwide. Shigella is one of the well-studied human pathogens

• towards the preparation of glycoconjugates, we report herein a convergent chemical synthesis of the tetrasaccharide as its 4-methoxyphenyl glycoside 1 corresponding to the O-antigen of Shigella boydii type 9 using a [2 + 2] block glycosylation strategy (Figure 2). Results and Discussion The convergent

• synthesis of the target tetrasaccharide 1 as its 4-methoxyphenyl glycoside has been achieved applying a number of recently developed elegant reaction methodologies. A number of notable features are present in the synthetic strategy, which are (a) convergent [2 + 2] block glycosylation; (b) application of

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

• unsaturated glycoside 4 to be achieved; phosphomolybdic acid [32] gave the product (α:β, 8:1) in 63% yield. Deacetylation of 4 and regioselective silylation of the primary alcohol gave the threo allylic alcohol 2. The sulfonamide nucleophiles 6, 7 and 9 were prepared from the corresponding amines 5 [33] and 8

Synthesis, reactivity and biological activity of 5-alkoxymethyluracil analogues

• Lucie Brulikova and
• Jan Hlavac

Beilstein J. Org. Chem. 2011, 7, 678–698, doi:10.3762/bjoc.7.80

• is a C-glycoside isomer of uridine and plays an important role in proteosynthesis. In organisms, pseudouridine is biosynthesized from uridine via the action of pseudouridine synthases. Nevertheless, the specific role of pseudouridines is still the subject of much research. In order to study

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

• remaining hydroxyl groups afforded the glycoside 13, which was desilylated with HF·pyridine complex to yield 14. This chemoselective transformation uses conditions that are similar to those reported by Tam et al. [23], and result in desilylation in a significantly shorter period than that previously

• reported using HCl in MeOH/Et2O [22]. The diol 15 was prepared by treatment of 12 with 2,3-butanedione and trimethyl orthoformate in the presence of catalytic acid in refluxing MeOH (Scheme 2) [37]. Trace amounts of the corresponding methyl glycoside were also obtained, arising from limited methanolysis of

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• . This procedure has been successfully used to prepare C-aryl glycoside from C-alkynyl glycoside and ethylene according to an EYCM/Diels–Alder/oxidation sequence (Scheme 6) [52][53]. The selective cyclopropanation of the most electron deficient double bond of the unsymmetrical dienic system has been

Catalysis: transition-state molecular recognition?

• Ian H. Williams

Beilstein J. Org. Chem. 2010, 6, 1026–1034, doi:10.3762/bjoc.6.117

• cases of methyl transfer and of glycoside hydrolysis to illustrate and to update the same theme from a computational point of view. Discussion The transition state is of strategic importance within the field of chemical reactivity. Owing to its location in the region of the highest energy point on the

• − ΔGRint by virtue of the differential distortion energy ΔGTdist − ΔGRdist. TS recognition in enzymic glycoside hydrolysis The endo-1,4-β-xylanase (BCX) from Bacillus circulans catalyses the hydrolysis of xylan and β-xylobiosides with net retention of anomeric configuration by means of a double

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

• best result was obtained with commercially available triethylene glycol monochloride. Thus, peracetylated mannose 1 was reacted with triethyleneglycol monochloride, in the presence of boron trifluoride etherate to afford glycoside 2 [12] in 50–55% yield. After purification, the latter was converted to

Synthesis of lipophilic 1-deoxygalactonojirimycin derivatives as D-galactosidase inhibitors

• Georg Schitter,
• Elisabeth Scheucher,
• Andreas J. Steiner,
• Arnold E. Stütz,
• Martin Thonhofer,
• Chris A. Tarling,
• Stephen G. Withers,
• Jacqueline Wicki,
• Katrin Fantur,
• Eduard Paschke,
• Don J. Mahuran,
• Brigitte A. Rigat,
• Michael Tropak and
• Tanja M. Wrodnigg

Beilstein J. Org. Chem. 2010, 6, No. 21, doi:10.3762/bjoc.6.21

• study of glycoside-hydrolysing enzymes. These sugar mimetics have been found to have anti-viral, anti-cancer, anti-diabetes, anti-infective, as well as insect anti-feedant and plant growth regulatory effects. Because of their diverse properties, iminosugars have enjoyed continuous interest since their

• substituents of the new N-modified 1-galactonojirimycin derivatives on their biological interaction with respective glycoside hydrolases are described. Results and Discussion The key intermediate for the synthesis of N-modified lipophilic 1-deoxygalactonojirimycin derivatives 16–20 as well as 22 was the 3,4-O

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• -deazaguanine (c7G), forms a 1:1 complex with pentameric adenyl DNA. Deazaguanine nucleobase was chosen because of the unique glycoside bond stability and its ability to prevent G-quartet formation. To increase the already strong binding of DNG to DNA, DNG was combined with a ligand capable of binding

Convergent syntheses of Le^X analogues

• An Wang,
• Jenifer Hendel and
• France-Isabelle Auzanneau

Beilstein J. Org. Chem. 2010, 6, No. 17, doi:10.3762/bjoc.6.17

• respectively to the n-hexyl and 6-aminohexyl trisaccharide targets. Unexpectedly, the 6-acetylthiohexyl analogue underwent desulfurization and gave the n-hexyl glycoside product, whereas the 6-benzylthiohexyl analogue gave the desired disulfide trisaccharide dimer. This study constitutes a particularly

• , the reaction mixture was either stirred for 1 h at 50 °C in an oil bath (Supporting Information File 1, Method A) or submitted to microwave irradiation for 5 min at 50 °C (Supporting Information File 1, Method B). After acetylation of the excess chlorohexanol to ease its removal, pure glycoside 14 was

• isolated in excellent yield whether method A or B was followed. Thus, these syntheses of glycoside 14 constitute efficient alternatives to that reported by Nitz et al. in which the starting material was the corresponding anomeric bromide [45]. Nucleophilic displacement of the chlorine atom in glycoside 14

Synthesis in the glycosciences

• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2010, 6, No. 16, doi:10.3762/bjoc.6.16

• . Since the isolation of those complex glycans which are active in cellular communication is problematic, oligosaccharide synthesis is an important area of research. Moreover, what Professor Hans Paulsen, one of the greatest exponents of glycoside synthesis, observed in 1982 [2] still holds true today

• syntheses”. It is therefore not surprising that the majority of contributions collected in this Thematic Series deal with methods, both chemical and enzymatic, for oligosaccharide synthesis. One approach to deal with the problem of glycoside synthesis is the preparation of so-called glycomimetics. This is a

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• D-ribose 193. Treatment of D-ribose in acetone with allylic alcohol in presence of catalytic amount of sulfuric acid provided the corresponding protected acetonide allyl glycoside. The primary alcohol was transformed into a N-Boc amine by successive Mitsunobu reaction, reduction and acylation to

Dimerization of propargyl and homopropargyl 6-azido- 6-deoxy- glycosides upon 1,3-dipolar cycloaddition

• Nikolas Pietrzik,
• Daniel Schmollinger and
• Thomas Ziegler

Beilstein J. Org. Chem. 2008, 4, No. 30, doi:10.3762/bjoc.4.30

• , affording the dimeric glycoside 7a beside products of oligomerization (Scheme 1). The reaction proceeded significantly slower than the coupling of 4a and 5. A faster reaction occurred upon irradiation with microwave, which also gave a higher yield (54%) of 7a. Benzoylated glycoside 4a' did not give any

• compounds on TLC (ethyl acetate/n-hexane 1:1) and appeared to be products of oligomerization of the starting material 4. In the case of benzoylated glycoside 4a' where no cyclic dimer could be isolated from the complex reaction mixture, FAB MS of the purified mixture indeed revealed the presence of linear

Cimicifoetisides A and B, two cytotoxic cycloartane triterpenoid glycosides from the rhizomes of Cimicifuga foetida, inhibit proliferation of cancer cells

• Li-Rong Sun,
• Chen Qing,
• Yan-Li Zhang,
• Shu-Yu Jia,
• Zhong-Rong Li,
• Shen-Ji Pei,
• Ming-Hua Qiu,
• Michael L. Gross and
• Samuel X. Qiu

Beilstein J. Org. Chem. 2007, 3, No. 3, doi:10.1186/1860-5397-3-3

• , the sugar moiety must be either a-L-arabinopyranosyl-[4C1 chair conformation) or β-D-arabinopyranosyl [1C4 chair conformation], with the former being more favorable, as it is a common component of the triterpene glycoside isolated from Cimicifuga plants, whereas the isolation of the latter has not

Investigation of acetyl migrations in furanosides

• O. P. Chevallier and
• M. E. Migaud

Beilstein J. Org. Chem. 2006, 2, No. 14, doi:10.1186/1860-5397-2-14

• acetyl moieties. Such direct transesterification is intermolecular and while it has been observed in nucleoside-phosphoramidite and glycoside chemistry,[20][21][22][23] this alkoxide-promoted intermolecular acetyl migration process has been overlooked in furanosides. The isolated quantities of 1c and 1d

Study of thioglycosylation in ionic liquids

• Jianguo Zhang and
• Arthur Ragauskas

Beilstein J. Org. Chem. 2006, 2, No. 12, doi:10.1186/1860-5397-2-12

• ionic liquids for the synthesis of alkyl glycoside and disaccharides via coupling of thioalkyl glycosyl donors with glycal acceptors. Alkyl glycosides and oligosaccharides are important intermediates and products in the synthesis of biologically active natural compounds and mimics. For example, tetra-O

• -acetyl-glycoside derivatives have been used in the synthesis of glycosyltransferase inhibitors and clearing agents to enhance anti-tumor activities.[10][11] In addition, alkyl glycosides possessing long alkyl chain have gained wide interest as non-ionic surfactants.[12] A variety of reagents have been

• reported to promote the formation of a glycoside bond which include, classical glycosyl halides, thioglycosides, pentenyl glycosides, anomeric trichloroacetimidates and others.[13] As reviewed by Oscarson,[14] thioalkyl or thioaryl glycosyl donors have been shown to exhibit excellent selectivity and

Synthesis and glycosidase inhibitory activity of new hexa- substituted C8-glycomimetics

• Olivia Andriuzzi,
• Christine Gravier-Pelletier,
• Gildas Bertho,
• Thierry Prangé and
• Yves Le Merrer

Beilstein J. Org. Chem. 2005, 1, No. 12, doi:10.1186/1860-5397-1-12

• protonated, and the corresponding ammonium ions mimick the charge of the presumed transition states or intermediates of the enzymatic glycoside hydrolyses [18]. More recently, attention has been increasingly accorded to seven- and eight-membered ring systems [19][20][21][22][23][24][25][26][27][28][29][30