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Showing papers on "Glycal published in 2008"


Journal ArticleDOI
TL;DR: In this paper, a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glucosides via Ferrier rearrangement, was developed.

66 citations


Journal ArticleDOI
TL;DR: A highly efficient strategy for chemoselective oxidation of aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media is reported.
Abstract: A highly efficient strategy for chemoselective oxidation of aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media is reported. Their in situ intermolecular 1,3-dipolar cycloaddition (1,3-DC) with olefins in nanometer aqueous micelles occurs with improved stereoselectivity and acceleration of reaction rate toward synthesis of new chiral synthons, 3-(2′-C-3′,4′,6′-tri-O-benzylglycal)-Δ2-isoxazolines and others. Construction of optically pure 2,8-dioxabicyclo[4.4.0]decene skeleta is performed by this green approach, and the stereochemistry of the new chiral center is predicted by B3LYP density functional theory.

65 citations


Journal ArticleDOI
TL;DR: The synthesis of a fluorinated analogue of ADP-L-glycero-beta-D-manno-heptopyranose, the donor substrate of the heptosyl transferase WaaC, which catalyzes the incorporation of this carbohydrate into LPS.
Abstract: Heptosides are found in important bacterial glycolipids such as lipopolysaccharide (LPS), the biosynthesis of which is targeted for the development of novel antibacterial agents. This work describes the synthesis of a fluorinated analogue of ADP-L-glycero-beta-D-manno-heptopyranose, the donor substrate of the heptosyl transferase WaaC, which catalyzes the incorporation of this carbohydrate into LPS. Synthetically, the key step for the preparation of ADP-2F-heptose is the simultaneous and stereoselective installation of both the fluorine atom at C-2 and the phosphoryl group at C-1 through a selectfluor-mediated (selectfluor=1-chloromethyl-4-fluorodiazoniabicyclo[2.2.2]octane bis(triflate)) electrophilic addition/nucleophilic substitution involving a heptosylglycal. Therefore, we detail in this article 1) the stereoselective preparation of the key intermediates heptosylglycals, 2) the development of a new fluorophosphorylation procedure allowing an excellent beta-gluco stereoselectivity with "all-equatorial" glycals, 3) the synthesis of the target ADP-2F-heptose, and 4) some comments on the contacts observed between the fluorine atom of the final molecule and the protein in the crystallographic structure of heptosyltransferase WaaC.

61 citations


Journal ArticleDOI
TL;DR: The total synthesis of the potent cytotoxin theopederin D has been achieved through the use of an oxidative carbon–carbon bond cleavage reaction to form an acyliminium ion in the presence of acid labile acetal groups.
Abstract: The total synthesis of the potent cytotoxin theopederin D has been achieved through the use of an oxidative carbon–carbon bond cleavage reaction to form an acyliminium ion in the presence of acid labile acetal groups Other key transformations include an acid mediated functionalization of a tetrahydrofuranyl alcohol in the presence of a tetrahydropyranyl alcohol, a syn-selective glycal epoxide opening, and a catalytic asymmetric aldehyde-acid chloride condensation.

40 citations


Journal ArticleDOI
TL;DR: Sugar-iminosugar hybrid molecules made up of D-glucose and D-galactose with pyrrolidine-based iminosugars are synthesized from glycal epoxides and found to be moderate glycosidase inhibitors.

37 citations


Journal ArticleDOI
TL;DR: The utility of N-glycosyl trichloroacetamides as robust and versatile intermediates in the synthesis of unsymmetrical urea-linked disaccharides and trisaccharide is demonstrated and the method for the stereoselective synthesis of alpha- and beta- glycosyl ureas via Pd(II)-catalyzed rearrangement of glycal trich chloroacetimidates is developed.
Abstract: The research on the area of glycosyl urea derivatives, in which the O- and N-glycosidic bonds are replaced with the urea-glycosidic linkages, has recently emerged with applications in the field of aminoglycoside antibiotics. We have developed a novel method for the stereoselective synthesis of α- and β-glycosyl ureas via Pd(II)-catalyzed rearrangement of glycal trichloroacetimidates. In our approach, the α- and β-selectivity at the anomeric carbon of N-glycosyl trichloroacetamides depends on the nature of the palladium−ligand catalyst. While the cationic Pd(II)-L-4 (2-trifluoroacetylphenol) complex promotes α-selectivity, the neutral Pd(II)-TTMPP-L-5 (4-chloro-2-trifluoroacetylphenol) complex favors β-selectivity. The resulting α- and β-N-glycosyl trichloroacetamides were further coupled with a diverse array of primary and hindered secondary nitrogen nucleophiles to provide the corresponding glycosyl ureas in moderate to good yields and with no loss of stereochemical integrity at the anomeric carbon. We h...

31 citations


Journal ArticleDOI
TL;DR: A methodology allowing the synthesis alpha-CF(2)-mannosides, based on the addition of a difluoroenoxysilane to a glycal followed by a dihydroxylation reaction, is described, which converts into two pseudoglycopeptides which may act as E- and P-selectin inhibitors.
Abstract: A methodology allowing the synthesis alpha-CF(2)-mannosides, based on the addition of a difluoroenoxysilane to a glycal followed by a dihydroxylation reaction, is described. The resulting 2,2-difluoro-2-mannosylacetate is converted into two pseudoglycopeptides which may act as E- and P-selectin inhibitors.

26 citations


Journal ArticleDOI
TL;DR: A new general methodology for the synthesis of 1,1,1-trihaloalditols by starting from 1,5-anhydro-2-deoxy-hex-1-enitol derivatives (glycals) is described.
Abstract: Anew general methodology for the synthesis of 1,1,1-trihaloalditols by starting from 1,5-anhydro-2-deoxyhex- 1-enitol derivatives (glycals) is described. The halogens are introduced sequentially in each of the three different steps of the process. The fluorine is introduced in the first step by electrophilic fluorination of the starting glycal; next, hydroxyhalogenation of the resulting vinyl fluoride allows the addition of any halogen (F, Cl, Br or I) at will, and finally, an iodine atom is inserted through an alkoxyl radical fragmentation reaction. This methodology allows the preparation of diverse types of 1,1,1-trihalogenated compounds (R CF2I, RCFI2, RCFClI and R CFBrI) under mild conditions compatible with sensitive substituents. In some cases, the diastereomeric mixtures generated from RCFClI and RCFBrI can be chromatographically separated, and their configuration determined by X-ray crystallographic analysis. The synthetic usefulness of these compounds has been preliminarily assessed by examining the reactivity of the fluorinated radical generated by rupture of the CI bond.

26 citations


Journal ArticleDOI
TL;DR: InCl3 as discussed by the authors catalyzes a facile stereoselective 1,3-migration of allylic ethers of glycals to afford 2-C-methylene- and 2-3-unsaturated-α-O-glycosides in high yields.

19 citations


Journal ArticleDOI
TL;DR: Synthetized 4-deoxy-4-amino-alpha-D-erythro-hex-2-enopyranosyl di- and trisaccharides of types A and B were synthetized by means of a reiterative, completely stereoselective glycosylation process which makes use of the D-galactal-derived allyl epoxide 1beta and D-allal- derived allyl N-nosyl aziridine 2

18 citations



Journal ArticleDOI
TL;DR: The solid-state structures of C12 bola form isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key intermolecular interactions between bolaform headgroups are necessary to determine the structure in the solid state.
Abstract: Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain α,ω-diol, followed by deacetylation under Zemplen conditions. The reactions are stereoselective and preferentially afford the α-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key interm...

Journal ArticleDOI
TL;DR: In this article, a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glucosides via Ferrier rearrangement, was developed.
Abstract: We have developed a novel glycal-based O-glycosylation reaction, in which the substrates are not only peracetyl glycals but also perbenzyl glucals to afford the corresponding 2,3-unsaturated-O-glycosides via Ferrier rearrangement. The reaction of the perbenzyl glucal with various alcohols catalyzed by ferric sulfate hydrate (Fe2(SO4)3·xH2O) was successfully carried out to give 2,3-unsaturated d-O-glucosides with exclusive α-selectivity and no formation of addition products 2-deoxy hexopyranosides was observed. It is the first report on peralkyl glycal efficiently undergoing Ferrier rearrangement instead of addition of alcohols catalyzed by Lewis acids. Fe2(SO4)3·xH2O is an effective, convenient, and environmentally benign heterogeneous catalyst. It has low catalytic loading and recyclable without significant loss of activity.

Journal ArticleDOI
TL;DR: The high similarity in large-scale solid state structures between 1 and glucosamide bolaamphiphile 4 suggest a strong dependence on head group stereochemistry, and that only a few, key intermolecular interactions between head groups are necessary in controlling the ultimate structure observed.

Journal ArticleDOI
TL;DR: Silyl and isopropylidene-O-protected chromium glucal and galactal carbenes have been synthesized from their glycal precursors according to the Fischer route.
Abstract: Silyl- and isopropylidene-O-protected chromium glucal and galactal carbenes have been synthesized from their glycal precursors according to the Fischer route. NMR studies indicate a preferred 5 H 4 or 4 H 5 conformation, depending on the nature of the protective group and the configuration at C-4. The complexes with glycal carbenes have been applied to the diastereoselective cyclopropanation of methyl crotonate and γ-crotonolactone.

Journal ArticleDOI
TL;DR: In this paper, a novel palladium(II)-catalyzed stereoselective synthesis of α and β-N-glycosyl trichloroacetamides has been developed.
Abstract: A novel palladium(II)-catalyzed stereoselective synthesis of α- and β-N-glycosyl trichloroacetamides has been developed The α- and β-selectivity at the anomeric carbon depends on the nature of the palladium−ligand catalyst While the cationic palladium(II) promotes the α-selectivity, the neutral palladium(II) favors the β-selectivity


Journal ArticleDOI
TL;DR: Although vinyl sulfone-modified- (VSM) pent-2'-enofuranosyl nucleosides 2 and hex-2-enopyranosyl glycoside 4 are easily synthesized from the corresponding mesylated sulfones 1c and 3c, via an oxidation-mesylation-elimination route, the 3'-C-sulfonyl-hex-3'-enopyrsylthymine 11 is not obtained from 10 and a glycal

Journal ArticleDOI
TL;DR: In this article, the synthesis of the potent cytotoxin theopederin D has been achieved through the use of an oxidative carbon-carbon bond cleavage reaction to form an acyliminium ion in the presence of acid labile acetal groups.
Abstract: The total synthesis of the potent cytotoxin theopederin D has been achieved through the use of an oxidative carbon–carbon bond cleavage reaction to form an acyliminium ion in the presence of acid labile acetal groups Other key transformations include an acid mediated functionalization of a tetrahydrofuranyl alcohol in the presence of a tetrahydropyranyl alcohol, a syn-selective glycal epoxide opening, and a catalytic asymmetric aldehyde-acid chloride condensation.

Patent
03 Dec 2008
TL;DR: In this article, a method for the production of glycosamine analogues (I) from natural carbohydrates, i.e. 5- or 6-ring glycals, involves reacting the glycal with a nitroalkane to give a carbohydrate 2-C-N-analogue in which the nitrogen is in the form of a Nitro group and reducing this to (I).
Abstract: A method for the production of glycosamine analogues (I) from natural carbohydrates , i.e. 5- or 6-ring glycals, involves (a) reacting the glycal with a nitroalkane to give a carbohydrate 2-C-N-analogue in which the nitrogen is in the form of a nitro group and (b) reducing this to (I).

Journal ArticleDOI
TL;DR: 2-Deoxy-2-iodo-N-glycosylamides have been prepared in high yields and with good selectivities by a one step process starting from glycals by tin hydride mediated reductive deiodination.
Abstract: 2-Deoxy-2-iodo-N-glycosylamides have been prepared in high yields and with good selectivities by a one step process starting from glycals. The resulting trans-configured 2-deoxy-2-iodo-N-glycosylamides are readily converted to the 2-deoxy-N-glycosylamides by tin hydride mediated reductive deiodination. Aliphatic and aromatic primary amides, substituted ureas and amino acids were added to glycals in this fashion. The stereoselectivity and yields in these reactions were governed by a variety of factors including the nature of the solvent used in the addition reaction, the types of protecting groups on the glycal, and the nature of the R group on the amide.

Journal ArticleDOI
TL;DR: Glycals undergo smooth coupling with β-enaminoketones and βenaminoesters generated in situ from 1,3-dicarbonyl compounds and arylamines in the presence of 10 mol % of InCl3 in refluxing dichloroethane to produce oxa-aza bicyclononene scaffolds as discussed by the authors.
Abstract: Glycals undergo smooth coupling with β-enaminoketones and β-enaminoesters generated in situ from 1,3-dicarbonyl compounds and arylamines in the presence of 10 mol % of InCl3 in refluxing dichloroethane to produce oxa-aza bicyclononene scaffolds in excellent yields with high selectivity. The use of InCl3 makes this protocol simple, convenient and easy to scale-up.