cas 4860-85-9, METHYL 2,3,4,6-TETRA-O-ACETYL-BETA-D-GLUCOPYRANOSIDE

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General Strategy for the Synthesis of Rare Sugars via Ru(II)-Catalyzed and Boron-Mediated Selective Epimerization of 1,2- trans-Diols to 1,2- cis-Diols
Human glycans are primarily composed of nine common sugar building blocks. On the other hand, several hundred monosaccharides have been discovered in bacteria and most of them are not readily available. The ability to access these rare sugars and the corresponding glycoconjugates can facilitate the studies of various fundamentally important biological processes in bacteria, including interactions between microbiota and the human host. Many rare sugars also exist in a variety of natural products and pharmaceutical reagents with significant biological activities. Although several methods have been developed for the synthesis of rare monosaccharides, most of them involve lengthy steps. Herein, we report an efficient and general strategy that can provide access to rare sugars from commercially available common monosaccharides via a one-step Ru(II)-catalyzed and boron-mediated selective epimerization of 1,2-trans-diols to 1,2-cis-diols. The formation of boronate esters drives the equilibrium toward 1,2-cis-diol products, which can be immediately used for further selective functionalization and glycosylation. The utility of this strategy was demonstrated by the efficient construction of glycoside skeletons in natural products or bioactive compounds.
Li, Xiaolei,Tang, Weiping,Wu, Jicheng
p. 3727 - 3736
(2022/03/02)

Structure of the unusual Sinorhizobium fredii HH103 lipopolysaccharide and its role in symbiosis
Rhizobia are soil bacteria that form important symbiotic associations with legumes, and rhizobial surface polysaccharides, such as K-antigen polysaccharide (KPS) and lipopolysaccharide (LPS), might be important for symbiosis. Previously, we obtained a mutant of Sinorhizobium fredii HH103, rkpA, that does not produce KPS, a homopolysaccharide of a pseudaminic acid derivative, but whose LPS electrophoretic profile was indistinguishable from that of the WT strain. We also previously demonstrated that the HH103 rkpLMNOPQ operon is responsible for 5-acetamido-3,5,7,9-tetradeoxy-7-(3-hydroxybutyramido)-L-glyc-ero-L-manno-nonulosonic acid [Pse5NAc7(3OHBu)] production and is involved in HH103 KPS and LPS biosynthesis and that an HH103 rkpM mutant cannot produce KPS and displays an altered LPS structure. Here, we analyzed the LPS structure of HH103 rkpA, focusing on the carbohydrate portion, and found that it contains a highly heterogeneous lipid A and a peculiar core oligosaccharide composed of an unusually high number of hexuronic acids containing b-configured Pse5NAc7(3OHBu). This pseudaminic acid derivative, in its a-configuration, was the only structural component of the S. fredii HH103 KPS and, to the best of our knowledge, has never been reported from any other rhizobial LPS. We also show that Pse5NAc7(3OHBu) is the complete or partial epitope for a mAb, NB6-228.22, that can recognize the HH103 LPS, but not those of most of the S. fredii strains tested here. We also show that the LPS from HH103 rkpM is identical to that of HH103 rkpA but devoid of any Pse5NAc7(3OHBu) residues. Notably, this rkpM mutant was severely impaired in symbiosis with its host, Macroptilium atropurpureum.
Di Lorenzo, Flaviana,Speciale, Immacolata,Silipo, Alba,Alías-Villegas, Cynthia,Acosta-Jurado, Sebastián,Rodríguez-Carvajal, Miguel-ángel,Dardanelli, Marta S.,Palmigiano, Angelo,Garozzo, Domenico,Ruiz-Sainz, José-Enrique,Molinaro, Antonio,Vinardell, José-María
p. 10969 - 10987
(2021/01/07)

Direct dehydrative glycosylation catalyzed by diphenylammonium triflate
Methods for direct dehydrative glycosylations of carbohydrate hemiacetals catalyzed by diphenylammonium triflate under microwave irradiation are described. Both armed and disarmed glycosyl-C1-hemiacetal donors were efficiently glycosylated in moderate to excellent yields without the need for any drying agents and stoichiometric additives. This method has been successfully applied to a solid-phase glycosylation.
Hsu, Mei-Yuan,Lam, Sarah,Lin, Mei-Huei,Lin, Su-Ching,Wang, Cheng-Chung,Wu, Chia-Hui
supporting information

(2020/03/13)

ACYLATED ACTIVE AGENTS AND METHODS OF THEIR USE FOR THE TREATMENT OF AUTOIMMUNE DISORDERS
Disclosed herein are acylated active agents (e.g., acylated catechin polyphenols, acylated carotenoids, acylated mesalamines, acylated sugars, acylated shikimic acids, acylated ellagic acid, acylated ellagic acid analogue, and acylated hydroxybenzoic acids), active agent combinations (e.g., with a second agent that is a fatty acid) and methods of their use, e.g., for modulating an autoimmunity marker or for treating an autoimmune disorder.
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(2019/12/28)

Structural properties of D-mannopyranosyl rings containing O-Acetyl side-chains
The crystal structures of 1,2,3,4,6-penta-O-Acetyl--d-mannopyranose, C16H22O11, and 2,3,4,6-Tetra-O-Acetyl--d-mannopyranosyl-(1.2)-3,4,6-Tri-O-Acetyl--d-mannopyranosyl-( 1.3)-1,2,4,6-Tetra-O-Acetyl--d-mannopyranose, C40H54O27, were determined and compared to those of methyl 2,3,4,6-Tetra-O-Acetyl--d-mannopyranoside, methyl -d-mannopyranoside andmethyl -d-mannopyranosyl-(1.2)--d-mannopyranoside to evaluate the effects of O-Acetylation on bond lengths, bond angles and torsion angles. In general, O-Acetylation exerts little effect on the exo-and endocyclic C-C and endocyclic C-O bond lengths, but the exocyclic C-O bonds involved in O-Acetylation are lengthened by -0.02 A ° . The conformation of the O-Acetyl side-chains is highly conserved, with the carbonyl O atom either eclipsing the H atom attached to a 2-Alcoholic C atom or bisecting the H-C-H bond angle of a 1-Alcoholic C atom. Of the two C-O bonds that determine O-Acetyl side-chain conformation, that involving the alcoholic C atom exhibits greater rotational variability than that involving the carbonyl C atom. These findings are in good agreement with recent solution NMR studies of O-Acetyl side-chain conformations in saccharides. Experimental evidence was also obtained to confirm density functional theory (DFT) predictions of C-O and O-H bond-length behavior in a C-O-H fragment involved in hydrogen bonding.
Turney, Toby,Zhang, Wenhui,Oliver, Allen G.,Serianni, Anthony S.
p. 1166 - 1174
(2019/08/13)

Antimycobacterial 1,4-napthoquinone natural products from Moneses uniflora
A new 1,4-naphthoquinone derivative, 5,8-dihydro-3-hydroxychimaphilin (4) and five known compounds (1, 2 and 5–7) were isolated from an extract of the Canadian medicinal plant Moneses uniflora that significantly inhibited the growth of Mycobacterium tuberculosis H37Ra. The structure of 4 was established through analysis of NMR and MS data and the absolute configuration of the glycone of 5 was determined by chemical transformation and comparison with standards prepared from D- and L-glucose. All compounds isolated were screened against Mycobacterium tuberculosis (H37Ra) and the mammalian HEK 293 cell line and, with the exception of compounds 5 and 7, exhibited marked selectivity in their bioactivity: Compound 1 exhibited potent antimycobacterial activity (IC50 of 5.4 μM) and moderate cytotoxicity (IC50 of 30 μM); compounds 2, 4 and 6 showed moderate antimycobacterial activity (IC50 values from 28 to 47 μM) without affecting the viability of mammalian cells; compound 5 displayed moderate activity in both assays (IC50 values of 44 and 55 μM respectively); and compound 7 was not active in either assay. These data suggest that the Moneses napthaquinone derivatives elicit biological responses in mycobacterial and mammalian cells through disparate modes of action that warrant further investigation.
Li, Haoxin,Bos, Allyson,Jean, Stéphanie,Webster, Duncan,Robichaud, Gilles A.,Johnson, John A.,Gray, Christopher A.
p. 229 - 233
(2018/08/21)

One-pot oxidation-hydrocyanation sequence coupled to lipase-catalyzed diastereoresolution in the chemoenzymatic synthesis of sugar cyanohydrin esters
A three-step, one-pot synthesis and diastereoresolution sequence is described in anhydrous toluene starting from methyl α-D-2,3,4-tri-O- acetylgalacto- (1a), -manno- (1b) and -glucopyranosides (1c). The reaction sequence, including consecutive transformations through the aldehyde [PhI(OAc)2, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)] and cyanohydrin [basic resin or (R)-oxynitrilase] into the (6R)-cyanohydrin ester (lipase) is shown to proceed in a one-pot cascade, except that the basic resin (when used) should be removed before the addition of the enzymatic acylation reagents. We have shown that the effective transformation of 1a (75 % reaction yield) through labile intermediates gives the stable (6R)-cyanohydrin butanoate (85 % de). Further diastereomeric purification by chromatography is possible, although the product is already of high diastereopurity. (6R)-Cyanohydrin esters are obtained through acylation with Burkholderia cepacia lipase. The (6S)-ester (de 99 %) is produced by Candida rugosa lipase when the sequence is started from 1c whereas the other sugar derivatives are less suited to the reaction with lipase. Copyright
Hietanen, Ari,Kanerva, Liisa T.
experimental part
p. 2729 - 2737
(2012/07/13)

Glycosylation of α-amino acids by sugar acetate donors with InBr 3. Minimally competent Lewis acids
A simplified method for the preparation of Fmoc-serine and Fmoc-threonine glycosides for use in O-linked glycopeptide synthesis is described. Lewis acids promote glycoside formation, but also promote undesired reactions of the glycoside products. Use of 'minimally competent' Lewis acids such as InBr 3 promotes the desired activation catalytically, and with greatly reduced side products from sugar peracetates.
Lefever, Mark R.,Szab, Lajos Z.,Anglin, Bobbi,Ferracane, Michael,Hogan, Joanna,Cooney, Lauren,Polt, Robin
scheme or table
p. 121 - 125
(2012/05/20)

Methyl 1,2-orthoesters as useful glycosyl donors in glycosylation reactions: A comparison with n-pent-4-enyl 1,2-orthoesters
Mannopyranose-derived methyl 1,2-orthoacetates (R = Me) and -benzoates (R = Ph) can function as glycosyl donors - upon BF3·Et 2O activation in CH2Cl2 - in glycosylation reactions with monosaccharide acceptors to afford disaccharides in good yields. In the process, glycosylation is preferred to acid-catalyzed rearrangement leading to methyl mannopyranosides. Methyl 1,2-orthoesters can be also used in regioselective glycosylation protocols with monosaccharide diols, in which they display good regioselectivity. Copyright
Uriel, Clara,Ventura, Juan,Gomez, Ana M.,Lopez, J. Cristobal,Fraser-Reid, Bert
experimental part
p. 3122 - 3131
(2012/07/13)

Unexpected stereocontrolled access to 1α,1′β-disaccharides from methyl 1,2-ortho esters
Mannopyranose-derived methyl 1,2-orthoacetates (R = Me) and 1,2-orthobenzoates (R = Ph) undergo stereoselective formation of 1α,1′β-disaccharides, upon treatment with BF 3?Et2O in CH2Cl2, rather than the expected acid-catalyzed reaction leading to methyl glycosides by way of a rearrangement-glycosylation process of the liberated methanol.
Uriel, Clara,Ventura, Juan,Gomez, Ana M.,Lopez, J. Cristobal,Fraser-Reid, Bert
experimental part
p. 795 - 800
(2012/03/22)

Variations on the SnCl4 and CF3CO2Ag-promoted glycosidation of sugar acetates: a direct, versatile and apparently simple method with either α or β stereocontrol
Glycosidation of sugar peracetates (d-gluco, d-galacto) with SnCl4 and CF3CO2Ag led to either 1,2-cis-, or 1,2-trans-glycosides, depending primarily on the alcohols used. In particular, 1,2-trans-glycosides, expected from acyl-protected glycosyl donors, were formed in high yields with alcohols sharing specific features such as bulkiness, presence of electron-withdrawing groups or polyethoxy motifs. In contrast, simple alcohols afforded ～1:1 mixtures of 2,3,4,6-tetra-O-acetyl, and 3,4,6-tri-O-acetyl 1,2-cis-glycosides due to anomerization and/or acid-catalyzed fragmentation of 1,2-orthoester intermediates. After reacetylation or deacetylation, acetylated or fully deprotected 1,2-cis-glycosides (α-d-gluco, α-d-galacto) were obtained in ～90% yields by a simple and direct method.
Xue, Jia Lu,Cecioni, Samy,He, Li,Vidal, Sébastien,Praly, Jean-Pierre
scheme or table
p. 1646 - 1653
(2009/12/24)

Indium trichloride promoted stereoselective synthesis of O-glycosides from trialkyl orthoformates
A novel, highly stereoselective method for O-glycosylation of glycals and glycosylbromides is developed using orthoformates as acceptors in the presence of InCl3 to afford the corresponding O-glycopyranosides in 66-94% yield. Both perbenzyl and peracetyl glycals afford the corresponding 2,3-unsaturated-O-glycosides with high α-selectivity. Stoichiometric amounts of orthoformates are sufficient to bring about this transformation instead of large excesses of alcohols.
Mukherjee, Debaraj,Yousuf, Syed Khalid,Taneja, Subhash C.
p. 4944 - 4948
(2008/09/21)

Tandem epoxidation-alcoholysis or epoxidation-hydrolysis of glycals catalyzed by titanium(IV) isopropoxide or Venturello's phosphotungstate complex
Venturello's phosphotungstate complex and titanium(IV) isopropoxide [Ti(O-i-Pr)4] were successfully used as catalysts for the epoxidation-alcoholysis of glycals using hydrogen peroxide [H2O 2]. Reaction substrates included a range of variously protected glycals and different alcohols were used as solvents. Ti(O-i-Pr)4 was only effective in methanol as solvent, but gave methyl glycosides in high yields and high selectivities. The Venturello complex proved to be a very versatile and efficient catalyst. Apart from epoxidation-alcoholysis in alcoholic solvents it also showed activity in biphasic conditions to allow for glycosylation of long-chain alcohols and was very effective in the stereoselective dihydroxylation of benzylated glucal.
Levecque, Pieter,Gammon, David W.,Kinfe, Henok Hadgu,Jacobs, Pierre,De Vos, Dirk,Sels, Bert
body text
p. 1557 - 1568
(2009/07/10)

Methyltrioxorhenium-catalyzed epoxidation-methanolysis of glycals under homogeneous and heterogeneous conditions
The efficient and high yielding domino epoxidation-methanolysis of glycals 8-15 has been achieved by oxidation with UHP in MeOH catalyzed by MTO. The products have been conveniently isolated as 2-acetoxy derivatives 16-23a, b by direct acetylation of the crude mixtures. Homogeneous MTO-amine complexes 5-7, heterogeneous poly(4-vinyl-pyridine)/MTO compounds I-III, and microencapsulated polystyrene/MTO systems IV-VII were also tested and demonstrated their effectiveness as catalysts for the oxidation step. The facial diastereoselectivity of the oxidation ranged from satisfactory to excellent depending on the substrate and could be optimized by ample screening of catalysts. Complete conversions of substrates and nearly quantitative yields of products were obtained under environmentally friendly experimental conditions and with the use of simple work-up procedures.
Goti, Andrea,Cardona, Francesca,Soldaini, Gianluca,Crestini, Claudia,Fiani, Cinzia,Saladino, Raffaele
p. 476 - 486
(2007/10/03)

InCl3 as a powerful catalyst for the acetylation of carbohydrate alcohols under microwave irradiation
Indium(III) chloride catalyzed microwave assisted acetylation of different carbohydrates is an efficient synthesis of per-O-acetyl derivatives and provides the products in good to excellent yields.
Das, Saibal Kumar,Reddy, K. Anantha,Krovvidi, V. L. Narasimha Rao,Mukkanti
p. 1387 - 1392
(2007/10/03)

Iodine promoted glycosylation with glycosyl iodides: α-glycoside synthesis
Glycosidation of fully acetylated glucopyranosyl iodide with methanol under the influence of iodine gave α-glucoside selectively. Use of less reactive acceptors led to the formation of α/β-mixtures. Glycosylations with fully benzoylated glucosyl iodide yielded β-glucosides only. In contrast, iodine-promoted glycosylation of serine and threonine with 2-azido-2-deoxy-glycosyl iodides, easily obtained in three steps, proceeded smoothly, resulting in only α-linked products in high yield in most cases. Copyright Taylor & Francis, Inc.
Van Well, Renate M.,Kartha, K. P. Ravindranathan,Field, Robert A.
p. 463 - 474
(2007/10/03)

Methyltrioxorhenium catalyzed domino epoxidation-nucleophilic ring opening of glycals
The use of catalytic methylrhenium trioxide (MTO) and urea hydrogen peroxide in room temperature ionic liquid for the hydroxyglycosylation with glycals in a domino fashion is reported. Excellent conversions and good selectivities for the epoxidation reaction were observed. Application to the synthesis of glycosylphosphates, good glycosyl donors, has been studied.
Soldaini, Gianluca,Cardona, Francesca,Goti, Andrea
p. 5589 - 5592
(2007/10/03)

Conformational study of the hydroxymethyl group in α-D-mannose derivatives
A study of the dependence of the hydroxymethyl group in α-D-mannose derivatives on the aglycon and its absolute configuration was performed by means of circular dichroism (CD) and NMR data. Depending mainly on the aglycon present, the gg or the gt rotamer was the most populated, the tg rotamer having a small population. In addition, the study showed a correlation between the rotational populations and the aglycon, the population of the gt rotamer increasing as the pKa of the bonded alcohol (aglycon) increased. Furthermore, the results revealed a strong dependence on the absolute configuration of the aglycon and point to the stereoelectronic exo-anomeric effect being responsible for these rotational dependencies besides nonbonding interactions.
Nobrega, Chaxiraxi,Vazquez, Jesus T.
p. 2793 - 2801
(2007/10/03)

A study of the epoxidation of 6-deoxyhex-5-enopyranosides. 1,5-Dicarbonyl derivatives and novel synthetic routes to D-xylo-hexos-5-ulose and D-lyxo-hexos-5-ulose
The work described deals with the isolation and characterization of epoxides from 6-deoxyhex-5-enopyranosides and preliminary exploration of their synthetic potential. Prolonged epoxidation reaction times led to their hydrolysis in situ and gave novel protected D-hexos-5-ulose derivatives (sugar 1,5-dicarbonyls). Some reactions of the hexos-5-uloses were studied, and in some cases septanoside (seven-membered-ring saccharide) derivatives were isolated. Novel routes to D-xylohexos-5-ulose and D-lyxo-hexos-5-ulose, of interest as intermediates in the synthesis and biosynthesis of inositols and aza sugars, are also described. The structures of the epoxides and novel hexos-5-uloses were established by NMR and X-ray crystallographic methods.
Enright, Philomena M.,Tosin, Manuela,Nieuwenhuyzen, Mark,Cronin, Linda,Murphy, Paul V.
p. 3733 - 3741
(2007/10/03)

Towards an unprotected self-activating glycosyl donor system: Bromobutyl glycosides
Bromobutyl mannopyranosides have been successfully used as both protected and unprotected glycosyl donors both with and without the use of an external activator.
Davis, Benjamin G.,Wood, Steven D.,Maughan, Michael A.T.
p. 555 - 558
(2007/10/03)

Caminoside A, an antimicrobial glycolipid isolated from the marine sponge Caminus sphaeroconia.
Extracts of the marine sponge Caminus sphaeroconia showed potent activity in a screen for bacterial type III secretion inhibitors. Bioassay guided fractionation of the extract led to the isolation of the novel antimicrobial glycolipid caminoside A (1). The structure of caminoside A was elucidated by analysis of spectroscopic data and chemical degradation.[structure: see text]
Linington, Roger G,Robertson, Marilyn,Gauthier, Annick,Finlay, B Brett,van Soest, Rob,Andersen, Raymond J
p. 4089 - 4092
(2007/10/03)

Synthesis of C7-C16-alkyl glycosides: Part I - Synthesis of alkyl D-glucopyranosides in the presence of tin (IV) chloride as a Lewis acid catalyst
The Lewis acid catalyzed glycosylation reaction of β-peracetylated sugar derivative (glucose) with fatty alkanols is used in a synthesis of C7-C16-alkyl glucopyranosides. The process occurs under the influence of tin (IV) chloride.
Konstantinovic,Predojevic,Mojsilovic,Dimitrijevic,Milosevic
p. 796 - 801
(2007/10/03)

Sulfuric acid-catalyzed acetolysis of anomeric methyl 2,3,4,6-tetra-O-acetyl-D-mannopyranosides: Kinetics and mechanism
The kinetics of the acetolysis and accompanying anomerization of methyl 2,3,4,6-tetra-O-acetyl-α- and -β-D-mannopyranosides at different concentrations of sulfuric acid in acetic anhydride-acetic acid mixtures were studied. The progress of the reactions was followed by gas chromatography, and the rate constants of the partial reactions were calculated on the basis of the time-dependent product distribution obtained. The mechanisms of the reactions involved are discussed. The involvement of unstable ionic intermediates is taken into account in the evaluation of the kinetic results, and simplified and extended models are used in the mathematical treatment of the results. A fourth-order Runge-Kutta algorithm is used to calculate rate constants. Acetolysis was found to be faster for mannosides than for glucosides relative to their anomerization. The β-mannopyranoside prefers endocyclic CO-bond rupture, while in the α anomer the endocyclic and exocyclic cleavages are comparatively rapid. Copyright (C) 2000 Elsevier Science Ltd.
Kaczmarek, Jozef,Kaczynski, Zbigniew,Trumpakaj, Zygmunt,Szafranek, Janusz,Bogalecka, Magda,Loennberg, Harri
p. 16 - 29
(2007/10/03)

Nafion-H catalyzed acetylation of alcohols
A wide variety of alcohols, some containing acid sensitive groups also, underwent smooth acetylation with acetic anhydride upon catalysis with Nation-H, a solid acid catalyst, which could be recovered and used again.
Kumareswaran,Pachamuthu,Vankar
p. 1652 - 1654
(2007/10/03)

Stereoselective α-glycosidation using FeCl3 as a Lewis acid catalyst
A simplified procedure for the stereoselective α-glycosidation of peracetylated sugars, carrying a participating group at C2, with aliphatic alcohols in the presence of FeCl3 as a Lewis acid is described.
Chatterjee, Swapan K.,Nuhn, Peter
p. 1729 - 1730
(2007/10/03)

Gas chromatographic investigation of the boron trifluoride etherate-induced formation and anomerization of glucopyranosides
Boron trifluoride etherate-induced glucosylation of methanol, 1-propanol, 2-propanol, 2-bromoethanol, and 3-bromo-2-(bromomethyl)propan-1-o1, using 1,2,3,4,6-penta-O-acetyl-β-D-glucopyranose as donor, gave the corresponding β-glucopyranosides. The α-glucosides and 1,2,3,4,6-penta-O-acetyl-α-D-glucopyranose were formed as byproducts in varying amounts, according to GLC analysis. The propensity of the different glucopyranosides to anomerize was determined in separate experiments.
Ellervik, Ulf,Jansson, Karl,Magnusson, Goeran
p. 777 - 784
(2007/10/03)

Cyclization of N-(Tetra-O-acetyl-D-gluco- and D-mannopyranosyl)-pyridinium salts in a methanolic solution of sodium methylate
N-(2,3,4,6-Tetra-O-acetyl-α-D-gluco-, β-D-gluco- and β-D-mannopyranosyl)-pyridinium salts were obtained and their structures were determined by 2D 1H NMR spectroscopy. The compounds obtained were treated with a methanolic solution of sodium methylate. The β-anomer of the D-gluco derivative cyclizes via Brigl's anhydride but the α anomer is competitively transformed according to the SN2 and SN1 mechanisms. The β-D-manno derivative does not cyclize under the conditions used. Comparison of the qualitative and quantitative results of the reaction studied enabled estimation of the influence of configuration at C-1 and C-2 on the course of cyclization. All product mixtures were separated by capillary gas chromatography (CGC) as exhaustively O-acetylated derivatives and their components were identified by coinjection with authentic materials.
Skorupowa,Dmochowska,Madaj,Kasprzykowski,Sokolowski,Wisniewski
p. 49 - 59
(2007/10/03)

Are glycosyl triflates intermediates in the sulfoxide glycosylation method? A chemical and 1H, 13C, and 19F NMR spectroscopic investigation
The title question is addressed by low-temperature 1H, 13C, and 19F NMR spectroscopies in CD2CL2 as well as by the preparation of authentic samples from glycopyranosyl bromides and AgOTf. At -78°C glycosyl triflates are cleanly generated with either nonparticipating or particpating protecting groups at O-2. The glycosyl triflates identified in this manner were allowed to react with methanol, resulting in the formation of methyl glycosides. Glycosyl triflates were generated at -78°C in CD2Cl2 and allowed to warm gradually until decomposition was detected by 1H and 19F NMR spectroscopy. The decomposition temperature and products are functions of the protecting groups employed.
Crich, David,Sun, Sanxing
p. 11217 - 11223
(2007/10/03)

Zinc-N-base mediated synthesis of pyranoid glycals mechanistic studies
Reactions of acetobromoglucose 1 or acetylated 1-bromo-D-galactopyranosyl cyanide 3 with zinc dust in the presence of a N-base (1-methylimidazole, 4-methylpyridine, or triethylamine, pyridine, respectively) in ethyl acetate or benzene were efficiently inhibited by 10-30 mol % of 1,4-dinitrobenzene, elemental sulfur, or carbon tetrachloride. Presence of glycosyl radicals in these reactions was also shown by trapping them with tert-dodecyl mercaptan or methyl acrylate. Based on these observations and the high yielding formation of glycal derivatives 2 and 4 of high purity a free radical chain mechanism is proposed for the transformations.
Somsak, Laszlo,Madaj, Janusz,Wisniewski, Andrzej
p. 1075 - 1087
(2007/10/03)

Reaction of D-fructose, D-glucose and inulin with alcohols in the presence of iodine; a novel glycosidation procedure
An efficient procedure for the glycosidation of D-fructose and D-glucose catalyzed by iodine is described. The reaction yields mainly alkyl glycofuranosides. Treatment of inulin under similar conditions leads to inter-glycosidic bond cleavage and to formation of alkyl D-fructofuranosides. The reaction conditions are particularly mild and relatively selective.
Verhart, Cor G.J.,Fransen, Carel T.M.,Zwanenburg, Binne,Chittenden, Gordon J.F.
p. 133 - 139
(2007/10/03)

Chemistry of 1-alkoxy-1-glycosyl radicals: Formation of β-mannopyranosides by radical decarboxylation and decarbonylation of manno-heptulosonic acid glycoside derivatives
A method for the preparation of highly enriched β-mannopyranosides is described. A glycosyl donor 28 is prepared from tetraallyl mannonolactone by standard means and coupled to a number of primary carbohydrate alcohols, resulting in the isolation in excellent yields of axial disaccharides. Following exchange of the allyl groups for acetyl esters, the furan is oxidatively cleaved with catalytic RuO2 and NaIO4 and the resulting acid subjected to the Barton decarboxylation. Coupling of 28 to a secondary alcohol, methyl 2,3-isopropylidene-α-L-rhamnopyranoside, resulted in an apparent inversion of anomeric stereochemistry and isolation of an equatorial disaccharide.
Crich, David,Hwang, Jae-Taeg,Yuan, Hongwei
p. 6189 - 6198
(2007/10/03)

THIOGLYCOSIDES AS POTENTIAL GLYCOSYL DONORS IN ELECTROCHEMICAL GLYCOSYLATION REACTIONS. PART 1: THEIR PREPARATION AND REACTIVITY TOWARD SIMPLE ALCOHOLS
Costant potential electrolysis of several glycosyl donors such as substituted phenyl 2,3,4,6-tetra-O-acetyl, benzoyl or benzyl-1-thio-β-D-gluco or galactopyranosides in dry acetonitrile in the presence of various primary, secondary or tertiary alcohols performed in an undivided cell, gave preferentially β-linked saccharides in moderate to good yields according to the nature of the protective groups on the sugar moiety. 2-Deoxy-2-phthalimido-1-thio-β-D-gluco derivatives gave the β-glucosides selectively in excellent yields.It was found, as expected, that substitution of the phenyl group with methoxy or methyl radicals facilitates the electrochemical glycosylation reaction by lowering the oxidation potentials of the corresponding thioglycosides.
Balovoine, Gilbert,Berteina, Sabine,Gref, Aurore,Fischer, Jean-Claude,Lubineau, Andre
p. 1217 - 1236
(2007/10/03)

Syntheses and Enzymatic Hydrolyses of Acylated Methyl a-D-Mannopyranosides
Selective pivaloylations of methyl α-D-mannopyranoside under various reaction conditions have been studied.The structures of the products were established by 1H-NMR spectroscopy and acetylation of partially pivaloyated compounds.The order of reactivity of hydroxyl groups was established and found to be 6-OH>3-OH>2-OH>4-OH.The newly synthesized acylated monosaccharides were subjected to the hydrolysis by rabbit serum and esterases isolated from rabbit serum.Various degrees of regioselectivity were observed in these reactions, depending on the sugar structure.
Ljevakovic, Durdica,Parat, Dijana,Tomasic, Jelka,Tomic, Srdanka
p. 477 - 484
(2007/10/02)

Radical oxygenation of 2-Dexyy-2-iodo hexopyranosides with molecular oxygen
2-Deoxy-2-iodo hexopyranosides react with molecular oxygen and tributylstannane to give the epimeric C-2 alcohols in high yield and moderate selectivity.
Moutel,Prandi
p. 8163 - 8166
(2007/10/02)

Design and Synthesis of Mannose Analogues as Inhibitors of α-Mannosidase
A series of N-, C- and S- mannopyranosyl derivatives (4, 9-16) have been synthesised and their inhibitory activity tested towards jackbean α-mannosidase (EC 3.2.1.24).These compounds are of mechanistic and synthetic interest in the design of new α-mannosidase inhibitors.
Maity, Sanat K.,Dutta, Samir K.,Banerjee, Asish K.,Achari, Basudeb,Singh, Manoranjan
p. 6965 - 6974
(2007/10/02)

ANODIC GLYCOSYLATION FROM ARYL THIOGLYCOSIDES
Unprotected aryl thioglucosides undergo electrochemical oxidation in undivided cell at constant moderated potential in the presence of alcohols to give the corresponding glucosides in good yield without any self condensation.
Balavoine, Gilbert,Gref, Aurore,Fischer, Jean-Claude,Lubineau, Andre
p. 5761 - 5764
(2007/10/02)

CIS-CLERODANE-TYPE DITERPENE LACTONES FROM EPHEMERANTHA COMATA
Two new cis-clerodane-type diterpene lactones named ephemeric acid and ephemeroside have been isolated from Ephemerantha comata Hunt & Summerh (Orchidaceae) and their structures have been characterized on the basis of spectroscopic evidence.Key Word Index - Ephemerantha comata; Orchidaceae; cis-clerodane; diterpene; glucoside; butenolide.
Niwa, Masatake,Kihira, Noriko,Hirata, Yoshimasa,Tori, Motoo,Wu, Tiang-Schung,Kuoh, Chang-Sheng
p. 3293 - 3296
(2007/10/02)

Methods for the preparation of alkyl 1,2-orthoacetates of D-glucopyranose and D-galactopyranose in high yield
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Tsui, David S. K.,Gorin, Philip A. J.
p. 137 - 147
(2007/10/02)

Dioxolanylium Ions Derived from Carbohydrates. IX. Rearrangement between Dioxolanylium and Dioxanylium Ions
The formation of 4,6-acetoxonium and benzoxonium ion derivatives of methyl gluco-, manno-, galacto- and idopyranosides from the 6-azido-6-deoxy compounds on treatment with nitrosonium ion is described and the formation and rearrangement of the 3,5-benzoxonium ion derived from methyl α-d-xylofuranoside discussed.
Jacobsen, Steffen
p. 157 - 164
(2007/10/02)

Reaction des glycosyl isonitriles avec les amines et les alcools
After complexation with metals, glycosylisonitriles 1 react with alcohols to give mainly orthoesters, if C-2 bears a participating group, and/or alkyl glycosides without particular stereoselectivity.In the case of amines, formamidines are obtained by α-addition to 1 in good yields.An example of further heterocyclisation is given with the stereospecific synthesis of the glucosylquinazolinone 15.
Marmet, Danielle,Boullanger, Paul,Descotes, Gerard
p. 373 - 378
(2007/10/02)

Sugar Tosylates via p-Toluenesulfinic Acid Esters. - p-Toluenesulfinimidazolide - A Reagent for Formation of Sulfinic Acid Esters without Using Halides
The reaction of the protected sugar derivatives 1, 4, 7, 10, 13, 16, 19 and 20 with p-toluenesulfinimidazolide prepared from p-toluenesulfinic acid and N,N'-carbonyldiimidazole yields the corresponding p-toluenesulfinic esters 2, 5, 8, 11, 14, 17, 20 and 22.With the exception of 20 and 22, these products can be oxidized with m-chloroperbenzoic acid in high yields and short overall reaction times to the tosylates 3, 6, 9, 12, 15 and 18.
Redlich, Hartmut,Meyer, Wolf-Ulrich
p. 1354 - 1360
(2007/10/02)

OXYAMINATION OF UNSATURATED SUGAR DERIVATIVES. PART III. CIS-ADDITION OF β-TOLUENESULFONAMIDO AND HYDROXYL GROUPS TO THE DOUBLE BOND OF METHYL 3,4-DIDEOXY-α-DL-THREO- AND ERYTHRO-HEX-3-ENOPYRANOSIDES
Vicinal oxyamination of fifteen derivatives of methyl 3,4-dideoxy-α-DL-threo- and erythro-hex-3-enopyranosides with chloramine-T--osmium tetroxide (Sharpless reagent) was investigated.Under the conditions employed several methyl 3- and 4-deoxy-3- and 4-p-toluenesulfonamido-α-DL-hexopyranosides of altro, allo and galacto configuration, as well as their 6-amino-6-deoxy, and 6-deoxy analogs have been prepared.The oxyamination reaction was completely supressed if an allylic acyloxy group was present in the substrate; instead, dihydroxylated products, i.e. methyl hexopyranosides have been formed.
Banaszek, Anna
p. 583 - 598
(2007/10/02)