- A simple and highly diastereoselective preparation of glycal epoxides using the MCPBA-KF complex
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Glycals are converted ro the corresponding epoxides in high yields by a diastereoselective one-step epoxidation using the m-chloroperoxybenzoic acid-KF complex in anhydrous dichloromethane.
- Bellucci, Giuseppe,Catelani, Giorgio,Chiappe, Cinzia,D'Andrea, Felicia
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- Direct epoxidation of d-glucal and d-galactal derivatives with in situ generated DMDO
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A multi-gram epoxidation of 3,4,6-tri-O-benzyl-d-glucal and d-galactal with dimethyldioxirane (DMDO) generated in situ from Oxone/acetone in a biphasic system (CH2Cl2-aqueous NaHCO3) resulted in the formation of
- Cheshev, Pavel,Marra, Alberto,Dondoni, Alessandro
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- C-glycosides: A stereoselective synthesis of α- and β-C-galactosides with glycosyl dianions
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α- or β-C-galactosides can be obtained from the configurationally stable anomeric glycosyl dianions which are prepared by transmetallation of a tin compound or by reductive lithiation of a chloride. Different electrophiles react selectively at the anomeric center.
- Burkhart, Fred,Hoffmann, Matthias,Kessler, Horst
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- A Stereoselective and Preparative Entry to 1,2-Anhydrosugars through Oxidation of Glycals with Perfluoro-cis-2,3-dialkyloxaziridines
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Perfluoro-cis-2,3-dialkyloxaziridines 1 perform the direct epoxidation of glycals 2 to give cleanly corresponding 1,2-anhydrosugars 3 with medium to complete diastereoselection; elaboration of these glycals to glycosyl fluorides and lipid conjugates is al
- Cavicchioli, Marcello,Mele, Andrea,Montanari, Vittorio,Resnati, Giuseppe
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- A short route to nucleoside diphosphate activated D- and L-hexoses
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Leloir transferases utilise nucleoside diphosphate sugars, which are notoriously difficult to synthesise and handle. Starting off from D- or L-configurated glycals, a facile synthesis of nucleotide sugars by epoxidation and direct coupling with uridine di
- Ernst, Christiane,Klaffke, Werner
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- Synthesis and Conformational Analysis of 2-O-Silyl Protected Nucleosides from Unprotected Nucleobases and Sugar Epoxides
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Synthesis of orthogonally protected 2-silyl nucleosides were achieved by trans opening of sugar epoxides with nucleobases catalyzed by trimethylsilyltrifluoromethanesulfonate using hexamethyldisilazane both as solvent and silylating agent. Both α and β nu
- Ahmed, Ajaz,Katoch, Meenu,Mukherjee, Debaraj,Rasool, Faheem,Singh, Gurpreet
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- α-C-Glycosides via syn Opening of 1,2-Anhydro Sugars with Organozinc Compounds in Toluene/n-Dibutyl Ether
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The diastereoselective addition of organozinc species to 1,2-anhydro sugars in toluene/n-dibutyl ether solvent is reported. Compared to the existing methods, the reaction proceeds at 0 °C, and only a slight excess of nucleophile is required to achieve good yields. Scope was assessed with different O-protected glycals along with various nucleophiles (aryl, alkynyl). This methodology was applied to the synthesis of the α-anomer of canagliflozin.
- Wagschal, Simon,Guilbaud, Johan,Rabet, Pauline,Farina, Vittorio,Lemaire, Sébastien
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- IN VIVO ASSEMBLY OF ASGPR BINDING THERAPEUTICS
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Compounds are provided that assemble together in vivo to form an ASGPR-binding compound that has an asialoglycoprotein receptor (ASGPR) binding ligand bound to an extracellular protein binding ligand for the selective degradation of the target extracellular protein in vivo to treat disorders mediated by the extracellular protein.
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- Ionic liquids as phase transfer catalysts: Enhancing the biphasic extractive epoxidation reaction for the selective synthesis of β-O-glycosides
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Ionic liquids promoted the direct epoxidation of glycals acting as PTC. 1,2-anhydrosugars were prepared by the oxidation of glycals under biphasic conditions with dimethydioxirane generated in situ from oxone/acetone and amphiphilic IL's as catalysts. β-O
- Santiago, Cintia C.,Lafuente, Leticia,Bravo, Rodolfo,Díaz, Gisela,Ponzinibbio, Agustín
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p. 3739 - 3742
(2017/09/02)
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- Glycosyl Cross-Coupling of Anomeric Nucleophiles: Scope, Mechanism, and Applications in the Synthesis of Aryl C-Glycosides
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Stereoselective manipulations at the C1 anomeric position of saccharides are one of the central goals of preparative carbohydrate chemistry. Historically, the majority of reactions forming a bond with anomeric carbon has focused on reactions of nucleophiles with saccharide donors equipped with a leaving group. Here, we describe a novel approach to stereoselective synthesis of C-aryl glycosides capitalizing on the highly stereospecific reaction of anomeric nucleophiles. First, methods for the preparation of anomeric stannanes have been developed and optimized to afford both anomers of common saccharides in high anomeric selectivities. We established that oligosaccharide stannanes could be prepared from monosaccharide stannanes via O-glycosylation with Schmidt-type donors, glycal epoxides, or under dehydrative conditions with C1 alcohols. Second, we identified a general set of catalytic conditions with Pd2(dba)3 (2.5 mol%) and a bulky ligand (JackiePhos, 10 mol%) controlling the β-elimination pathway. We demonstrated that the glycosyl cross-coupling resulted in consistently high anomeric selectivities for both anomers with mono- and oligosaccharides, deoxysugars, saccharides with free hydroxyl groups, pyranose, and furanose substrates. The versatility of the glycosyl cross-coupling reaction was probed in the total synthesis of salmochelins (siderophores) and commercial anti-diabetic drugs (gliflozins). Combined experimental and computational studies revealed that the β-elimination pathway is suppressed for biphenyl-type ligands due to the shielding of Pd(II) by sterically demanding JackiePhos, whereas smaller ligands, which allow for the formation of a Pd-F complex, predominantly result in a glycal product. Similar steric effects account for the diminished rates of cross-couplings of 1,2-cis C1-stannanes with aryl halides. DFT calculations also revealed that the transmetalation occurs via a cyclic transition state with retention of configuration at the anomeric position. Taken together, facile access to both anomers of various glycoside nucleophiles, a broad reaction scope, and uniformly high transfer of anomeric configuration make the glycosyl cross-coupling reaction a practical tool for the synthesis of bioactive natural products, drug candidates, allowing for late-stage glycodiversification studies with small molecules and biologics.
- Zhu, Feng,Rodriguez, Jacob,Yang, Tianyi,Kevlishvili, Ilia,Miller, Eric,Yi, Duk,O'Neill, Sloane,Rourke, Michael J.,Liu, Peng,Walczak, Maciej A.
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supporting information
p. 17908 - 17922
(2017/12/26)
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- Glycosyl dithiocarbamates: β-selective couplings without auxiliary groups
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In this article, we evaluate glycosyl dithiocarbamates (DTCs) with unprotected C2 hydroxyls as donors in β-linked oligosaccharide synthesis. We report a mild, one-pot conversion of glycals into β-glycosyl DTCs via DMDO oxidation with subsequent ring opening by DTC salts, which can be generated in situ from secondary amines and CS2. Glycosyl DTCs are readily activated with Cu(I) or Cu(II) triflate at low temperatures and are amenable to reiterative synthesis strategies, as demonstrated by the efficient construction of a tri-β-1,6-linked tetrasaccharide. Glycosyl DTC couplings are highly β-selective despite the absence of a preexisting C2 auxiliary group. We provide evidence that the directing effect is mediated by the C2 hydroxyl itself via the putative formation of a cis-fused bicyclic intermediate.
- Padungros, Panuwat,Alberch, Laura,Wei, Alexander
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p. 2611 - 2624
(2014/04/17)
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- Glycal assembly by the in situ generation of glycosyl dithiocarbamates
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Glycal assembly offers an expedient entry into β-linked oligosaccharides, but epoxyglycal donors can be capricious in their reactivities. Treatment with Et2NH and CS2 enables their in situ conversion into glycosyl dithiocarbamates, which can be activated by copper triflate for coupling with complex or sterically congested acceptors. The coupling efficiency can be further enhanced by in situ benzoylation, as illustrated in an 11-step synthesis of a branched hexasaccharide from glucals in 28% isolated yield and just four chromatographic purifications.
- Padungros, Panuwat,Alberch, Laura,Wei, Alexander
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supporting information; experimental part
p. 3380 - 3383
(2012/09/22)
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- Stereoelectronic factors in the stereoselective epoxidation of glycals and 4-deoxypentenosides
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Glycals and 4-deoxypentenosides (4-DPs), unsaturated pyranosides with similar structures and reactivity profiles, can exhibit a high degree of stereoselectivity upon epoxidation with dimethyldioxirane (DMDO). In most cases, the glycals and their corresponding 4-DP isosteres share the same facioselectivity, implying that the pyran substituents are largely responsible for the stereodirecting effect. Fully substituted dihydropyrans are subject to a "majority rule", in which the epoxidation is directed toward the face opposite to two of the three groups. Removing one of the substituents has a variable effect on the epoxidation outcome, depending on its position and also on the relative stereochemistry of the remaining two groups. Overall, we observe that the greatest loss in facioselectivity for glycals and 4-DPs is caused by removal of the C3 oxygen, followed by the C5/anomeric substituent, and least of all by the C4/C2 oxygen. DFT calculations based on polarized-π frontier molecular orbital (PPFMO) theory support a stereoelectronic role for the oxygen substituents in 4-DP facioselectivity, but less clearly so in the case of glycals. We conclude that the anomeric oxygen in 4-DPs contributes toward a stereoelectronic bias in facioselectivity whereas the C5 alkoxymethyl in glycals imparts a steric bias, which at times can compete with the stereodirecting effects from the other oxygen substituents.
- Alberch, Laura,Cheng, Gang,Seo, Seung-Kee,Li, Xuehua,Boulineau, Fabien P.,Wei, Alexander
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experimental part
p. 2532 - 2547
(2011/06/19)
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- Epoxidation of glycals with oxone-acetone-tetrabutylammonium hydrogen sulfate: A convenient access to simple β-D-glycosides and to α-D-mannosamine and D-talosamine donors
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The addition of a phase transfer catalyst during the epoxidation of perbenzylated glycals with oxone- acetone under biphasic conditions allows their complete epoxidation. The epoxides were readily transformed into methyl 1,2-trans-β-D-glycosides or 1,2-trans-β-D-glycopyranosyl azides (D-gluco and-D-galacto configurations) bearing a free hydroxyl group at the 2-position. These glycosyl azides were converted to alkyl 1,2-trans-2-acetamido- 2-deoxy-α-D-pyranosides or alkyl 2-allyloxycarbonylamino-2- deoxy-α-D-pyranosides (D-manno and D-talo configurations) by a Staudinger reaction and a double inversion of configuration at C-1 and C-2.
- Lafont, Dominique,D'Attoma, Joseph,Gomez, Rejane,Goekjian, Peter G.
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experimental part
p. 1197 - 1204
(2011/10/19)
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- Stereoselective synthesis of β-Phenylselenoglycosides from glycals and rationalization of the selenoglycosylation processes
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β-Phenylselenoglycosides have been efficiently and stereoselectively synthesized by direct oxidative glycosylation of benzenselenolate (PhSe -) with glycals. A rationalization of the presently described β-selectivity and the opposite α-selectivity reported by Danishefsky in the ring-opening of epoxy glycals with benzeneselenol (PhSeH) is proposed.
- Di Bussolo, Valeria,Fiasella, Annalisa,Balzano, Federica,Uccello Barretta, Gloria,Crotti, Paolo
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supporting information; experimental part
p. 4284 - 4287
(2010/08/06)
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- Synthesis of fused pyran-carbahexopyranoses as glycosidase inhibitors
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Synthesis of polyhydroxylated oxabicyclo[4,4,0]decanes, which constitute a new family of annulated carbasugars, has been accomplished in a stereoselective manner by employing readily available 1,2-anhydro-3,4,6-tri-O-benzyl-α-d-glycopyranoses.
- Doddi, Venkata Ramana,Kancharla, Pavan K.,Reddy, Y. Suman,Kumar, Amit,Vankar, Yashwant D.
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body text
p. 606 - 612
(2009/05/11)
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- Gold(I)-catalyzed glycosidation of 1,2-anhydrosugars
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(Chemical Equation Presented) Being able to increase the yield by >20% compared to the conventional use of anhydrous zinc chloride (>1 equiv) as a promoter, Ph3PAuOTf is disclosed to be a superior catalyst for the well-established glycosylation reaction with 1,2-anhydrosugars as donors.
- Li, Yao,Tang, Pingping,Chen, Youxi,Yu, Biao
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p. 4323 - 4325
(2008/09/21)
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- The exo-deoxoanomeric effect in the conformational preferences of C-glycosides
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Rotational studies of a series of β-d-C-glycopyranosides were carried out by CD and NMR spectroscopy. The populations around the C-glycosidic bond were strongly dependent on the structure of the C-aglycon, the exo-syn rotamer population increasing with th
- Mayato, Carlos,Dorta, Rosa L.,Vazquez, Jesus T.
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p. 931 - 948
(2008/02/03)
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- 1,2-Anhydrosaccharides and 1,2-cyclic sulfites as saccharide donors in convergent synthesis of glucopyranosyl-, mannopyranosyl- and ribofuranosylbenzocamalexin
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A convergent synthesis of 1-(β-o-glucopyranosyl)-, 1-(α-D-mannopyranosyl)- and 1-(β-D-ribofuranosyl) benzocamalexin was elaborated as an alternative route to the linear approach based on the indoline-indole method. 1,2-Anhydrosaccharides and 1,2-cyclic sulfites as saccharide donors were used in the key glycosylation step. Coupling with benzocamalexin resulted in moderate to excellent yields of nucleoside analogs, depending on the saccharide donor, catalyst and solvent used.
- Humenik, Martin,Kutschy, Peter,Kovacik, Vladimir,Bekesova, Slavka
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p. 487 - 506
(2007/10/03)
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- Conversion of D-Glucals into L-Glycals and Mirror-Image Carbohydrates
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(Equation presented) L-Glycals can be prepared in seven steps from readily available D-glucals, enabling the facile construction of mirror-image carbohydrates such as the L-lactosamine derivative shown above.
- Boulineau, Fabien P.,Wei, Alexander
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p. 119 - 121
(2007/10/03)
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- Total synthesis of mannosyl tryptophan and its derivatives
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Glycosylation is one of the most important post- or co-translational modifications of proteins, which affects the biological activities of the parent proteins by influencing the higher-order structure. Recently, a highly novel variant of glycoproteins tha
- Manabe, Shino,Marui, Yoshihiko,Ito, Yukishige
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p. 1435 - 1447
(2007/10/03)
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- Samarium diiodide-mediated reductive coupling of epoxides and carbonyl compounds: A stereocontrolled synthesis of C-glycosides from 1,2-anhydro sugars
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Sugar mimics: 1,2-anhydro sugars can be cross-coupled with aldehydes and ketones under very mild conditions and using a wide range of protecting groups to give C-glycosides in good yield in a radical reaction mediated by SmI2 (see scheme; A = n
- Chiara, Jose Luis,Sesmilo, Esther
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p. 3242 - 3246
(2007/10/03)
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- Linear synthesis of the tumor-associated carbohydrate antigens Globo-H, Ssea-3, and Gb3
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The tumor-associated carbohydrate antigens Globo-H, SSEA-3, and Gb3 were synthesized in a linear fashion using glycosyl phosphate monosaccharide building blocks. All of the building blocks were prepared from readily available common precursors. The difficult α-(1→-4-cis)-galactosidic linkage was installed using a galactosyl phosphate donor with high selectivity. Introduction of the β-galactosamine unit required the screening a variety of amine protecting groups to ensure good donor reactivity and protecting group compatibility. An N-trichloroacetyl-protected galactosamine donor performed best for the installation of the β-glycosidic linkage. Conversion of the trichloroacetyl group to the N-acetyl group was achieved under mild conditions, fully compatible with the presence of multiple glycosidic bonds. This synthetic strategy is expected to be amenable to the synthesis of the globo-series of tumor antigens on solid-support.
- Bosse, Folkert,Marcaurelle, Lisa A.,Seeberger, Peter H.
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p. 6659 - 6670
(2007/10/03)
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- Oligosaccharide synthesis with glycosyl phosphate and dithiophosphate triesters as glycosylating agents
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Described is an efficient one-pot synthesis of α- and β-glycosyl phosphate and dithiophosphate triesters from glycals via 1,2-anhydrosugars. Glycosyl phosphates function as versatile glycosylating agents for the synthesis of β-glucosidic, β-galactosidic,
- Plante,Palmacci,Andrade,Seeberger
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p. 9545 - 9554
(2007/10/03)
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- 2-Deoxy-disaccharide approach to natural and unnatural glycosphingolipids synthesis
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2-Deoxy-disaccharides were easily converted into glycosylphytosphingosines, as new and efficient precursors of natural and unnatural glycosphingolipids. Copyright (C) 2000 Elsevier Science Ltd.
- Graziani, Andrea,Passacantilli, Pietro,Piancatelli, Giovanni,Tani, Simona
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p. 3921 - 3937
(2007/10/03)
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- Synthesis of D-glycopyranosyl azides from 1,2-anhydrosugars using lithium azidohydridodiisobutylaluminate
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1,2-Anhydrosugars were transformed regio- and stereoselectively into the corresponding D-glycopyranosyl azides in high yield by treatment with lithium azidohydridodiisobutylaluminate in THF.
- Lee, Goo Soo,Min, Hye Kyung,Chung, Bong Young
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p. 543 - 544
(2007/10/03)
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- Synthesis of laminin hexasaccharide analogue
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The synthesis of laminin hexasaccharide analogue di-O-[Gal-β-(1→4)-Glc-β]-(1→2)-(1→6)-man-α- (1→6)-man-α-Me derivative (1) was achieved with 1,2-anhydromannopyranose benzyl ether (3) as the key intermediate. Coupling of 3 with methyl 2,3,4-tri-O-benzyl-α-D-mannopyranoside (4) promoted by ZnCl2 gave methyl 2,3,4-tri-O-benzyl-6-O-(3,4,6-tri-O-benzyl-α-D-mannopyranosyl)-α-D- mannopyranoside (2a). Selective 6-O-debenzylation of 2b with ZnCl2-Ac2O-HOAc followed by coupling with acetobromolactopyranose afforded 1.
- Ding, Xianglan,Kong, Fanzuo
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p. 915 - 922
(2007/10/03)
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- Diastereoselective Bromination of Allyl Glycosides Using Tetrabutylammonium Tribromide
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Both (R) and (S)-2,3-dibromo-1-propanol with e.e. up to 60percent have been obtained by diastereoselective addition of Br2 to allyl glucosides and galactosides having only one unprotected hydroxyl group at C-2 or C-6 using tetrabutylammonium tribromide, followed by hydrolysis.The absolute configuration is shown to depend on the position of the free hydroxyl and on the configuration at the anomeric centre.
- Bellucci, Giuseppe,Chiappe, Cinzia,D'Andrea, Felicia
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p. 221 - 230
(2007/10/02)
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- STEREOSELECTIVE GLYCOSIDIC COUPLING REACTIONS OF FULLY BENZYLATED 1,2-ANHYDRO SUGARS WITH N-TOSYL- OR N-BENZYLOXYCARBONYL-L-SERINE METHYL ESTER
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The glycosidic coupling reaction of 1,2-anhydro-3,4,6-tri-O-benzyl-β-D-mannopyranose (7), 1,2-anhydro-3,4,6-tri-O-benzyl-α-D-galactopyranose (21), and 1,2-anhydro-3,4-di-O-benzyl-α-D-xylopyranose (18) with N-tosyl- (10) or N-benzyloxycarbonyl- (11) L-serine methyl ester provides a new stereocontrolled synthesis of 1,2-trans linked glycopeptides.The 1,2-anhydro sugars are shown to react smoothly with 10 or 11 in the presence of Lewis acid (ZnCl2 or AgOTf) as well as powdered 4 Angstroem molecular sieves in CH2Cl2 at room temperature to afford glycosyl serine derivatives with high stereoselectivity and high yield in less than 30 min.An improved method using 2-O-acetyl-3,4,6-tri-O-benzyl-α-D-mannopyranosyl chloride (6) as the key intermediate for ring closure was applied for the synthesis of 1,2-anhydro-3,4,6-tri-O-benzyl-β-D-mannopyranose.
- Du, Yuguo,Kong, Fanzuo
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p. 341 - 352
(2007/10/02)
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- On the Direct Epoxidation of Glycals: Application of a Reiterative Strategy for the Synthesis of β-Linked Oligosaccharides
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The use of dimethyldioxirane for the first direct epoxidation of glycals is described.The products of such reactions, 1,2-anhydro sugars, are employed in the stereospecific construction of β-linked oligosaccharides.A key element is the use of glycals with
- Halcomb, Randall L.,Danishefsky, Samuel J.
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p. 6661 - 6666
(2007/10/02)
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- SYNTHESIS OF SUBSTITUTED 2,7-DIOXABICYCLOHEPTANES: 1,2-ANHYDRO-3,4,6-TRI-O-BENZYL-AND 1,2-ANHYDRO-3,4,6-TRI-O-(p-BROMOBENZYL)-α-D-GALACTOPYRANOSE
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The title compounds were synthesized from D-galactose via 9 steps.For obtaining stable, 1,2-blocked D-galactopyranose ethers, the 1,2-hydroxyl groups were protected with an ethylidene group instead of a 1-ethoxyethylidene group.The key intermediates for t
- Kong, Fanzuo,Du, Jingying,Shang, Heng
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p. 217 - 226
(2007/10/02)
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