Allyl Glycosides Research Articles

ChemInform Abstract: Glycosyl Iodides Are Highly Efficient Donors under Neutral Conditions.

Abstract Glycosyl iodides have been prepared and subjected to glycosylation under neutral conditions. The reactions are highly efficient, giving α glycosides even with sterically demanding glycosyl acceptors. Glucosyl iodides react with allyl alcohol slowest and require refluxing conditions. Galactosyl iodides are intermediate in reactivity, providing the allyl glycoside in 3 h at room temperature, whereas glycosylation of fucosyl iodides occurs in less than 1 h under similar conditions. The scope and limitations of the reactions were demonstrated with a variety of acceptors, including an anomeric hydroxyl group, to give trehalose analogs. β-Selective glycosylation of glucosyl iodides, in the absence of C-2 participation, could be achieved by simply changing the solvent from benzene to acetonitrile.

N-Bromosuccinimide-Mediated Conversion of Allyl Glycosides to Glycosyl Hemiacetals

A novel reaction condition has been developed for the hydrolysis of differentially functionalized allyl glycosides to their corresponding glycosyl hemiacetal derivatives in the presence of N-bromosuccinimide (NBS). The reaction condition is exceptionally fast, mild, and compatible with most of the functional groups used in the oligosaccharide synthesis, and yields were excellent.

Facile glycosylation strategy with two-stage activation of allyl glycosyl donors. Application to concise synthesis of Shigella flexneri serotype Y O-antigen

A practical, useful glycosylation method employing only allyl glycoside building blocks has been developed. The donor's glycosylation reactivity is turned on via isomerization of its anomeric allyl protecting group into the corresponding prop-1-enyl moiety. Subsequent chemoselective activation with NIS/TfOH achieves high yields in glycosidic bond construction at room temperature. The efficacy and efficiency of this approach in carbohydrate synthesis is demonstrated in the concise synthesis of the fully protected Shigella flexneri serotype Y O-antigen.

Synthesis of a neoglycoconjugate containing a Chlamydophila psittaci-specific branched Kdo trisaccharide epitope

The branched Kdo trisaccharide sodium (3-deoxy-α- d- manno-oct-2-ulopyranosyl)onate-(2→8)-[sodium (3-deoxy-α- d- manno-oct-2-ulopyranosyl)onate-(2→4)]-sodium (allyl 3-deoxy-α- d- manno-oct-2-ulopyranosid)onate has been prepared utilizing the regioselective glycosylation of the C-7, C-8 diol entity of a Kdo monosaccharide acceptor with a Kdo bromide donor followed by the attachment of the third Kdo unit to O-4 of the disaccharide intermediate. Deacetylation and hydrolysis of the methyl ester groups furnished the trisaccharide allyl glycoside which was converted into the corresponding 3-(2-aminoethylthio)propyl glycoside. Subsequent covalent attachment to bovine serum albumin furnished a neoglycoconjugate serving as an antigen for the induction of Chlamydophila psittaci-specific monoclonal antibodies.

ChemInform Abstract: BiBr3‐Promoted Activation of Peracetylated Glycosyl Iodides: Straightforward Access to Synthetically Useful 2‐O‐Deprotected Allyl Glycosides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

BiBr3‐Promoted Activation of Peracetylated Glycosyl Iodides: Straightforward Access to Synthetically Useful 2‐O‐Deprotected Allyl Glycosides

AbstractSubstoichiometric amounts of BiBr3 are able to promote anomeric activation of acetylated glycosyl iodides. This reactivity can be exploited for straightforward access to allyl glycosides unprotected at the O‐2 position. The reported protocol appears to be convenient in comparison with the pre‐existing ones in that shorter experimental times are needed and the use of strong acids is avoided. Suitable structural features of substrates (6‐deoxy sugars or use of benzoyl or methoxycarbonyl 2‐O‐participating groups) switch the process to a preferential glycosidation without deprotection at the O‐2 position.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis of branched tri- to pentasaccharides representative of fragments of Shigella flexneri serotypes 3a and/or X O-antigens

Fragments of the {2)-[α- d-Glc p-(1→3)]-α- l-Rha p-(1→2)-α- l-Rha p-(1→3)-[Ac→2]-α- l-Rha p-(1→3)-β- d-Glc pNAc-(1→} n ( (E)AB AcCD ) n polymer were synthesized. D(E)A, CD(E)A, AcCD(E)A were obtained according to a linear strategy, whereas BCD(E)A and B AcCD(E)A were derived from the condensation of appropriate BC and D(E)A building blocks. Oligosaccharides were synthesized as their propyl glycoside, relying on (i) the efficient trichloroacetimidate chemistry, (ii) a common EA allyl glycoside, and (iii) a 2 -trichloroacetamido- d-glucopyranose precursor to residue D. Final Pd/C-mediated deprotection, run under a high pressure of hydrogen, ensured O-acetyl stability. All targets are parts of the O-antigen of Shigella flexneri 3a, a prevalent serotype. Non- O-acetylated oligosaccharides are shared by the S. flexneri serotype X O-antigen.

Simple Glycosylation Reaction of Allyl Glycosides.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Carboxymethylglycoside lactones (CMGLs): structural variations on the carbohydrate moiety

New glucose and galactose based bicyclic lactones, with variations in the anomeric configuration, the protecting groups (acetyl or benzyl) and the furanosyl or pyranosyl rings were synthesized from allyl glycosides and used for the preparation of a series of new glycosylated alkyne amides.

Simple Glycosylation Reaction of Allyl Glycosides

A simple glycosylation strategy employing only allyl glycosides is described. In a one-pot fashion, an allyl glycoside is first isomerized to the reactive 1-prop-en-yl glycoside intermediate, which subsequently undergoes glycosylation with a glycosyl acceptor, promoted by NIS at room temperature.

Synthetic access to spacer-linked 3,6-diamino-2,3,6-trideoxy-α-d-glucopyranosides—potential aminoglycoside mimics for the inhibition of the HIV-1 TAR-RNA/Tat-peptide complex

The synthesis of spacer-linked neoaminoglycoside 5 is described. Key steps of the synthesis are the introduction of nitrogen functionalities at C-3 and C-6 and the olefin cross metathesis of allyl glycoside 16. Although it is known that Grubbs catalysts tolerate nitrogen functionalities, difficulties were encountered in the cross metathesis reaction. Factors that govern this dimerization are the steric and electronic demands of the catalyst and the substrate. Preliminary biological evaluation of homodimer 5, by studying the inhibition of HIV-1 TAR-RNA/Tat-peptide complex using a method based on fluorescence titration, revealed an inhibitory effect of 5.

Subtle Stereochemical and Electronic Effects in Iridium-Catalyzed Isomerization of C-Allyl Glycosides

[reaction: see text] Stereoselective isomerization of C-allyl glycosides into (E)-C-vinyl glycosides or (Z)-exo-glycals was carried out in the presence of the cationic iridium(I) catalyst [(Ph(2)MeP)(2)Ir(cod)PF(6)]. The products of the isomerization were affected by the relative 1,2-stereochemical relationships and by the nature of the protecting groups. These effects are discussed along with a plausible reaction mechanism.

Separation of O- and C-allyl glycoside anomeric mixtures by capillary electrophoresis and high-performance liquid chromatography

Rapid and reliable methods for the analysis of O- and C-allyl galactopyranosides and glucopyranosides are presented, based on capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC). In MEKC, the formation of chromophoric and charged complexes between the saccharides and borate as well as the hydrophobic interactions with micelles jointly contributed to the selective separation and sensitive detection of all the investigated anomeric couples. Some non-purified synthesis mixtures of C-allyl glycosides were successfully characterised without pre-treatment. MEKC buffer conditions for which glycosides separation was successfully achieved were then exported and applied to reverse-phase liquid chromatography (RP-HPLC), for the quantitative isolation of each allyl glycoside anomer. Identification of the obtained anomeric products was performed by electrospray mass spectrometry and 13C NMR spectroscopy. Glycoside–solvent interactions driving the selective anomeric separation were shortly addressed and discussed on the basis of sugar derivatives structural differences.

New Poly(Sodium Carboxylate)s Based on Saccharides. II. Cobuilder Performance of Ionic Allyl Glycoside Polymers as Substitutes of Standard Polycarboxylates

New poly(sodium carboxylate)s consisting of neutral or ionic allyl glycoside (AGlu) monomers and maleic acid or itaconic acid as comonomers were examined as substitutes for water‐soluble homo‐ and copolymers of acrylic acid, which are used as cobuilders in detergent formulations. Standardized tests allowed us to measure the calcium sequestering capacity, kaolin dispersing capacity, biodegradability, and thermal stability. These parameters were correlated with the different degrees of functionalization and charge densities of the new polycarboxylates. Comparison with some commercial monomolecular and oligomeric polycarboxylates indicate that the new copolymer poly(allyl‐β‐D‐glucofuranosiduronic acid‐co‐maleic acid) (P(AGlu‐MA)) has an interesting cobuilder performance and is a potentially attractive substitute.

First synthesis of the immunodominant β-galactofuranose-containing tetrasaccharide present in the cell wall of Aspergillus fumigatus

β-Gal f-(1→5)-β-Gal f-(1→6)-α-Man p-(1→6)-α-Man p, the immunodominant epitope in the cell-wall galactomannan of Aspergillus fumigatus, was synthesized for the first time as its allyl glycoside. The key disaccharide glycosyl donor, 2,3,5,6-tetra- O-benzoyl-β- d-galactofuranosyl-(1→5)-2- O-acetyl-3,6-di- O-benzoyl-β- d-galactofuranosyl trichloroacetimidate ( 10), was constructed by 5- O-glycosylation of 1,2- O-isopropylidene-3,6-di- O-benzoyl-α- d-galactofuranose ( 4) with 2,3,5,6-tetra- O-benzoyl-β- d-galactofuranosyl trichloroacetimidate ( 5), followed by 1,2- O-deacetonation, acetylation, selective 1- O-deacetylation, and trichloroacetimidation. The target tetrasaccharide 16 was obtained by the condensation of allyl 2,3,4-tri- O-benzoyl-α- d-mannopyranosyl-(1→6)-2,3,4-tri- O-benzoyl-α- d-mannopyranoside ( 14) as glycosyl acceptor with the disaccharide glycosyl donor 10, followed by deprotection.

Bi(OTf)3as Novel and Efficient Catalyst for the Stereoselective Synthesis ofC-Pseudoglycals

D-Glycals undergo smoothly allylic rearrangement with allyltrimethylsilane and trimethylsilyl cyanide in the presence of catalytic amount of bismuth triflate to afford the corresponding 2,3-unsaturated allyl glycosides and glycosyl cyanides in excellent yields with high α-selectivity.

Synthesis of β- d-glucose oligosaccharides from Phytophthora parasitica

The glucohexaose, β- d-Glc p-(1→3)-[β- d-Glc p-(1→3)-β- d-Glc p-(1→3)-β- d-Glc p-(1→6)]-β- d-Glc p-(1→3)- d-Glc p, was synthesized as its allyl glycoside via 3+3 strategy. The trisaccharide donor, 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-α- d-glucopyranosyl trichloroacetimidate ( 11), was obtained by 3-selective coupling of isopropyl 4,6- O-benzylidene-1-thio-β- d-glucopyranoside ( 2) with 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2- O-acetyl-4,6- O-benzylidene-α- d-glucopyranosyl trichloroacetimidate ( 6), followed by hydrolysis, acetylation, dethiolation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor, allyl 2,3,4,6-tetra- O-benzoyl-β- d-glucopyranosyl-(1→3)-2- O-acetyl-β- d-glucopyranosyl-(1→3)-4,6-di- O-acetyl-2- O-benzoyl-α- d-glucopyranoside ( 14), was prepared by coupling of allyl 4,6-di- O-acetyl-2- O-benzoyl-α- d-glucopyranoside ( 12) with 6, followed by debenzylidenation. Condensation of 14 with 11, followed by deacylation, gave the target hexaoside. A β-(1→3)-linked tetrasaccharide 29 was also synthesized with methyl 2- O-benzoyl-4,6- O-benzylidene-β- d-glucopyranosyl-(1→3)-2,4,6-tri- O-acetyl-β- d-glucopyranoside ( 25) as the acceptor and acylated β-(1→3)-linked disaccharide 21 as the donor.

“Sugaring” Carbosilane Dendrimers via Hydrosilylation.

Abstract Two new pathways to introduce carbohydrate derivatives into dendritic carbosilane structures were explored. Pathway one utilised alcoholysis of a chlorosilane with a protected hydroxyethyl glycoside resulting in Si–O linkages. Pathway two proceeds via a hydrosilylation reaction of a protected allyl glycoside with a carbosilane containing Si–H end groups in the presence of a platinum catalyst, thus leading to Si–C linked structures.

Synthesis of a hexasaccharide, the repeating unit of O-deacetylated GXM of C. neoformans serotype A

β- d-Glc pA-(1→2)-α- d-Man p-(1→3)-[β- d-Xyl p-(1→2)]-α- d-Man p-(1→3)[-β- d-Xyl p-(1→2)]-α- d-Man p, the repeating unit of the exopolysaccharide from Cryptococcus neoformans serovar A, was synthesized as its allyl glycoside. Thus, 3-O-selective acetylation of allyl 4,6- O-benzylidene-α- d-mannopyranoside afforded 2, and subsequent glycosylation of 2 with 2,3,4-tri- O-benzoyl- d-xylopyranosyl trichloroacetimidate furnished the β-(1→2)-linked disaccharide 4. Debenzylidenation followed by benzoylation gave allyl 2,3,4-tri- O-benzoyl-β- d-xylopyranosyl-(1→2)-3- O-acetyl-4,6-di- O-benzoyl-α- d-mannopyranoside ( 5), and selective 3-O-deacetylation gave the disaccharide acceptor 6. Coupling of 6 with 2- O-acetyl-3,4,6-tri- O-benzoyl-α- d-mannopyranosyl trichloroacetimidate yielded the trisaccharide 8, and subsequent deallylation and trichloroacetimidation gave 2,3,4-tri- O-benzoyl-β- d-xylopyranosyl-(1→2)-[2- O-acetyl-3,4,6-tri- O-benzoyl-α- d-mannopyranosyl-(1→3)]-4,6-di- O-benzoyl-α- d-mannopyranosyl trichloroacetimidate ( 9). Condensation of the trisaccharide donor 9 with the disaccharide acceptor 6 gave the pentasaccharide 10 whose 2-O-deacetylation gave the acceptor 11. Glycosylation of 11 with methyl 2,3,4-tri- O-acetyl-α- d-glucopyranosyluronate trichloroacetimidate and subsequent deprotection gave the target hexasaccharide.

Synthesis of a mannose nonasaccharide existing in the exopolysaccharide of Cryphonectria parasitica

α- d-Man p-(1→2)-α- d-Man p-(1→2)-α- d-Man p-(1→6)[α- d-Man p-(1→3)-α- d-Man p-(1→2)-α- d-Man p-(1→2)]-α- d-Man p-(1→6)-[α- d-Man p-(1→2)]-α- d-Man p, existing in the exopolysaccharide of Cryphonectria parasitica was synthesized as its allyl glycoside in a regio- and stereoselective manner.