- Reagent controlled stereoselective synthesis of teichoic acid α-(1,2)-glucans
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The stereoselective construction of 1,2-cis-glycosidic linkages is key in the assembly of biologically relevant glycans, but remains a synthetic challenge. Reagent-controlled glycosylation methodologies, in which external nucleophiles are employed to modu
- Berni, Francesca,Enotarpi, Jacopo,Overkleeft, Hermen S.,Van Der Marel, Gijs,Wang, Liming,Codée, Jeroen D. C.
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p. 2038 - 2050
(2020/03/27)
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- Secondary amine salt catalyzed controlled activation of 2-deoxy sugar lactols towards alpha-selective dehydrative glycosylation
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A new organocatalytic glycosylation method exploiting the lactol functionality has been disclosed. The catalytic generation of glycosyl oxacarbenium ions from lactols under forcible conditions via weakly Br?nsted-acidic, readily available secondary amine salts affects the diastereoselective glycosylation of 2-deoxypyranoses and furanoses. This operationally simple iminium catalyzed activation of 2-deoxy hemi-acetals is a potential alternative to the existing cumbersome methods that need specialized handling. The mechanisms for this unique transformation and kinetic/thermodynamic effects have been discussed based on both experimental evidence and theoretical studies.
- Ghosh, Titli,Mukherji, Ananya,Srivastava, Hemant Kumar,Kancharla, Pavan K.
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p. 2870 - 2875
(2018/05/03)
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- Rapid Synthesis of l-Idosyl Glycosyl Donors from α-Thioglucosides for the Preparation of Heparin Disaccharides
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A new methodology for the synthesis of the most challenging heparin building block has been developed. Orthogonally protected l-idosyl glycosyl donors were prepared by C5 epimerization of the corresponding thioglucosides using the hydroboration/oxidation method followed by a 4,6-acetal formation. The α-anomeric configuration was crucial, and the bulky C4 substituent was advantageous for the high l-ido diastereoselectivity. The 4,6-arylmethylene group proved to be a directing element in glycosylation, whereby stereoselective α-idosylation could be achieved by using idosyl donors without a C-2 participating group.
- Herczeg, Mihály,Demeter, Fruzsina,Balogh, Tímea,Kelemen, Viktor,Borbás, Anikó
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supporting information
p. 3312 - 3316
(2018/07/13)
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- Oxidative activation of C-S bonds with an electropositive nitrogen promoter enables orthogonal glycosylation of alkyl over phenyl thioglycosides
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A method for the selective activation of thioglycosides that uses the N+-thiophilic reagent Omesitylenesulfonylhydroxylamine (MSH) as a promoter is presented. The reaction proceeds via anomeric mesitylensulfonate intermediates, which could be isolated and fully characterized by placing a fluorine atom at the C2 position. In the presence of a soft Lewis acid, glycosylation reaction proceeds at ambient temperature with good yields. It is further demonstrated that it is possible to orthogonally activate S-ethyl in the presence of S-phenyl donors, enabling the design of sequential glycosylation strategies.
- Kitowski, Annabel,Jiménez-Moreno, Ester,Salvadó, Míriam,Mestre, Jordi,Castillón, Sergio,Jiménez-Osés, Gonzalo,Boutureira, Omar,Bernardes, Gon?alo J.L.
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p. 5490 - 5493
(2017/11/07)
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- Hydrogenolytic cleavage of naphthylmethyl ethers in the presence of sulfides
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With the aid of a series of model thioether or thioglycoside containing polyols protected with combinations of benzyl ethers and 2-naphthylmethyl ethers it is demonstrated that the latter are readily cleaved selectively under hydrogenolytic conditions in the presence of the frequently catalyst-poisoning sulfides. These results suggest the possibility of employing 2-naphthylmethyl ethers in place of benzyl ethers in synthetic schemes when hydrogenolytic deprotection is anticipated in the presence of thioether type functionality.
- Adero, Philip O.,Jarois, Dean R.,Crich, David
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- HClO4-silica-catalysed regioselective opening of benzylidene acetals and its application towards regioselective HO-4 glycosylation of benzylidene acetals in one-pot
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Here we report a high-yielding method for the regioselective reductive ring opening of 4,6-O-benzylidene acetals of hexapyranosides using inexpensive and robust HClO4-SiO2 as the acidic catalyst and triethylsilane as the hydride dono
- Dara, Saidulu,Saikam, Varma,Yadav, Mahipal,Singh, Parvinder Pal,Vishwakarma, Ram A.
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supporting information
p. 93 - 96
(2014/05/20)
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- In(III) triflate-catalyzed detritylation and glycosylation by solvent-free ball milling
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A highly efficient In(III) triflate-assisted method for the detritylation of O-trityl derivatives of carbohydrates, phenols, and alcohols using solvent-free mechanochemical method is described. In the case of carbohydrates, further reaction in the presence of an acceptor sugar leads to highly efficient glycosylation in the same pot resulting in the formation of the desired glycoside-product in very high yields. The method was applied successfully to the synthesis of a combinatorial library of galactose-based (1,6)-linked cyclohexa-, hepta-, and octasaccharides on gram scale.
- Kumar, Vajinder,Yadav, Narender,Kartha, K.P. Ravindranathan
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- Selective deprotection method of N -phenylcarbamoyl group
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We report an improved method for the selective deprotection of the N-phenylcarbamoyl group, which yields the corresponding alcohol without affecting other protecting groups. Deprotection was performed using di-tert-butyl dicarbonate and tetra-n-butylammon
- Akai, Shoji,Tanaka, Rika,Hoshi, Hidekazu,Sato, Ken-Ichi
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p. 8802 - 8808
(2013/09/24)
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- α-Selective organocatalytic synthesis of 2-deoxygalactosides
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Alpha rules: A thiourea acts as an efficient organocatalyst for the glycosylation of protected galactals to form oligosaccharides containing a 2-deoxymonosaccharide moiety (see scheme). The reaction is highly stereoselective for α-linkages and proceeds by way of a syn-addition mechanism. Copyright
- Balmond, Edward I.,Coe, Diane M.,Galan, M. Carmen,McGarrigle, Eoghan M.
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p. 9152 - 9155
(2012/10/29)
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- Stereodirecting effect of the pyranosyl C-5 substituent in glycosylation reactions
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(Chemical Equation Presented) The stereodirecting effect of the glycosyl C-5 substituent has been investigated in a series of D-pyranosyl thioglycoside donors and related to their preferred positions in the intermediate 3H4 and
- Dinkelaar, Jasper,De Jong, Ana Rae,Van Meer, Robert,Somers, Mark,Lodder, Gerrit,Overkleeft, Herman S.,Codee, Jeroen D. C.,Van Der Marel, Gijsbert A.
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supporting information; experimental part
p. 4982 - 4991
(2009/10/09)
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- Sonochemistry: A powerful way of enhancing the efficiency of carbohydrate synthesis
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Using sonication as a means of facilitating organic reactions in carbohydrate chemistry was explored under the conditions used for traditional organic synthesis. An array of representative reactions, including hydroxy group manipulation (acylation, protection/deprotection, acyl group migration), thioglycoside synthesis, azidoglycoside synthesis, 1,3-dipolar cycloaddition and reductive cleavage of benzylidene, commonly used in the synthesis of carbohydrate derivatives was examined. A series of glycosylation reactions that employ thioglycosides, glycosyl trichloroacetimidate, glycosyl bromide and glycosyl acetate as the glycosyl donors was also examined. Our results demonstrate that sonication can significantly shorten the reaction time, enhance the reactivity of reactant and lead to superior yield and excellent stereoselectivity. More importantly, a general protocol of glycosylation may finally be developed. Sonication is compatible to the conditions used for traditional organic synthesis. We believe that sonication can also be applied to other areas of synthetic processes.
- Deng, Shenglou,Gangadharmath, Umesh,Chang, Cheng-Wei Tom
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p. 5179 - 5185
(2007/10/03)
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- Selective deprotection of terminal isopropylidene acetals and trityl ethers using HClO4 supported on silica gel
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Terminal isopropylidene acetals are selectively cleaved to the corresponding 1,2-diols in good to excellent yields in 6-24 h at room temperature by using the 'HClO4?SiO2' reagent system. Likewise, trityl ethers are readily cleaved to the corresponding alcohols in good to excellent yields within 2-3 h at room temperature. Work-up involves merely filtration of the reagent followed by purification of the crude product.
- Agarwal, Aditi,Vankar, Yashwant D.
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p. 1661 - 1667
(2007/10/03)
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- Single-step multisyntheses of glycosyl acceptors: Benzylation of n-1 hydroxyl groups of phenylthio glycosides of xylose, mannose, glucose, galactose, 2-azido-2-deoxy-glucose, and 2-azido-2-deoxy-galactose
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An array of synthons is required to access an oligosaccharide library; however, multistep and thus time-consuming synthesis is inevitable. To rapidly access such synthetic units, multiple benzylation reactions of monosaccharides under phase-transfer condi
- Suzuki, Kaori,Ohtsuka, Isao,Kanemitsu, Takuya,Ako, Takuro,Kanie, Osamu
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p. 219 - 236
(2007/10/03)
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- Chiral crown ethers based on galactopyranosides
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The 1,4- and 1,6-bridged 20- and 23-membered galactocrown ethers 7, 8 and 11 were synthesized by intramolecular trans-glycosidation of the phenyl 1-thio-D-galactopyranosides 5, 6, and 10, respectively. The relevant precursors 5, 6, and 10 were obtained from phenyl 2,3,6-tri-O-benzyl-1-thio-β-D-galactopyranoside (2) and phenyl 2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranoside (3), respectively, via two etherification steps. Compounds 2 and 3 are accessible from the same precursor, phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-galactopyranoside (1), by regioselective opening of benzylidene acetal. O-Alkylation of 2 and 3 with bis(2-chloroethyl)ether gave phenyl 2,3,6-tri-O-benzyl-4-[2-(2-chloro-ethoxy)ethyl]-1-thio-β-D- galactopyranoside (4) and phenyl 2,3,4-tri-O-benzyl-6-[2-(2-chloro-ethoxy)ethyl]-1-thio-β-D- galactopyranoside (9), respectively. The ensuing chain elongation of 4 was carried out with triethylene glycol and tetraethylene glycol, respectively, yielding 5 and 6. Compound 9 was alkoxylated with tetraethylene glycol under the same reaction conditions yielding phenyl 2,3,4-tri-O-benzyl-6-O-{2-[ω-hydroxy-penta-(oxyethylene) ethyl]}-1-thio-β-D-galactopyranoside (10). The yields of the chiral crowns 7, 8 and 11, obtained in the final cyclization step from the thioglycosides 5, 6, and 10, are 32-61%, i.e., they could be more than doubled compared to previous experiments with O-glycosidic precursors. High β-stereoselectivity was found for the cyclizations to the 1,4-bridged crowns 7 and 8. In contrast, the more flexible 6-O-polyethylene derivative 10 cyclized exclusively to the 1,6-bridged α-glycosidic crown ether 11.
- Faltin, Franziska,Fehring, Volker,Miethchen, Ralf
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p. 1851 - 1856
(2007/10/03)
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- Prearranged glycosides. Part 8. Intramolecular α-galactosylation via succinoyl tethered glycosides
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Benzyl protected phenyl 1-thio-galactopyranoside donors which were tethered by a succinoyl linker at their positions 2 and 6, respectively, to position 3 of a blocked benzyl glucopyranoside acceptor with a 4-OH group solely afforded the corresponding α-(1→4)-linked disaccharides upon intramolecular glycosylation. 4,6-Siloxane protected mannosides react with rearrangement of the siloxane group under similar conditions.
- Ziegler, Thomas,Dettmann, Ralf,Ariffadhillah,Zettl, Uwe
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p. 1079 - 1095
(2007/10/03)
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- Synthesis of the two monomethyl esters of the disaccharide 4-O-α-D-galacturonosyl-D-galacturonic acid and of precursors for the preparation of higher oligomers methyl uronated in definite sequences
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Methyl (α-D-galactopyranosyluronic acid)-(1→4)-D-galactopyranuronate and methyl α-D-galactopyranosyluronate-(1→4)-D-galactopyranuronic acid have been synthesized by coupling methyl (benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate (3) or benzyl (benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate (4) with benzyl (phenyl 2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranosid)uronate and methyl (phenyl 2,3,4-tri-O-benzyl-1-thio-β-D-galactopyranosid)uronate, respectively, using N-iodosuccinimide and trifluoromethanesulphonic acid as promoters, followed by removal of the benzyl groups. The 4'-OH unprotected dimers benzyl (methyl 2,3-di-O-benzyl-α-D-galactopyranosyluronate)-(1→4)-(benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate and methyl (benzyl 2,3-di-O-benzyl-α-D-galactopyranosyluronate)-(1→4)-(benzyl 2,3-di-O-benzyl-β-D-galactopyranosid)uronate were prepared from methyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-trimethylsilyl-β-D-galactopyranosid)uronate and benzyl (phenyl 2,3-di-O-benzyl-1-thio-4-O-trimethylsilyl-β-D-galactopyranosid)uronate and acceptors 4 or 3, respectively. These compounds have been designed to serve as precursors for the preparation of higher-membered d-galacturonic acid oligomers methyl esterified in definite positions. Copyright (C) 1998 Elsevier Science Ltd.
- Magaud, Didier,Grandjean, Cyrille,Doutheau, Alain,Anker, Daniel,Shevchik, Vladimir,Cotte-Pattat, Nicole,Robert-Baudouy, Janine
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p. 189 - 199
(2007/10/03)
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- Borane/Bu2BOTf: A mild reagent for the regioselective reductive ring opening of benzylidene acetals in carbohydrates
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BH3/Bu2OTf is an effective reagent to reductively cleave 4,6-O-benzylidene acetals of various hexopyranosides to the corresponding 4-O-benzyl ethers. 4,6-O-Isopropylidene acetals can be similarly cleaved. Common protecting groups are
- Jiang, Lu,Chan, Tak-Hang
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p. 355 - 358
(2007/10/03)
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- Synthesis and absolute configuration of lepidimoide, a high potent allelopathic substance from mucilage of germinated cress seeds
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Lepidimoide (1), 1,2-cis-linked dissacharide, was synthesized from D-glucose and α-L-rhamnose for determination of the absolute configuration.
- Kosemura,Yamamura,Kakuta,Mizutani,Hasegawa
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p. 2653 - 2656
(2007/10/02)
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- 1,6-Anhydro-β-D-glucopyranose Derivatives as Glycosyl Donors for Thioglycosidation Reactions
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1,6-Anhydro derivatives of D-glucopyranose, maltose, and maltotriose reacted at room temperature with trimethylsilylated benzenethiol (2) and cyclohexanethiol (3) in the presence of zinc iodide (ZnI2) or trimethylsilyl triflate (TMSOTf), giving the corres
- Wang, Lai-Xi,Sakairi, Nobuo,Kuzuhara, Hiroyoshi
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p. 1677 - 1682
(2007/10/02)
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- Use of the methylsulfenyl cation as an activator for glycosylation reactions with alkyl (aryl) 1-thioglycopyranosides: synthesis of methyl O-(2-acetamido-2- deoxy-beta-D-glucopyranosyl)-(1----6)-O-alpha-D-glucopyranosyl-(1----2) -alpha-D -glucopyranoside, a derivative of the core trisaccharide of E. coli K12.
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Methylsulfenyl bromide (MSB) and methylsulfenyl trifluoromethanesulfonate (MST) have been used to prepare 1,2-cis-linked disaccharides. Ethyl (phenyl) 1-thio-beta-D-gluco- and galacto-pyranosides having non-participating (benzyloxy) protecting groups were used as the donors. The alpha beta-ratio of the products depended on the promoter and conditions of reaction. Intimate ion-pairs, formed initially, may be responsible for the steric outcome of the glycosylations. Thus, with ethyl 2,3,4,6-tetra-O-benzyl-alpha-D-mannopyranoside as a donor, moderate quantities of the beta-linked disaccharide could be produced using MSB as the activator. The synthesis of the title trisaccharide glycoside that contains 1,2-cis and 1,2-trans-linkages is described.
- Dasgupta,Garegg
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p. 225 - 238
(2007/10/02)
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- FACILE SYNTHESIS OF SILYLATED THIOGLYCOSIDES
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The one pot conversion of 1,2,4,6-tetra-O-acetyl-β-D-glucopyranose, 1, into phenyl 2,4,6-tri O-acetyl-3-O-trialkylsilyl-1-thio-β-D-glucopyranosides, 3, is described.The method is applicable to use with galactopyranosyl-, 2-deoxyglucopyranosyl-, and ribofuranosyl-starting materials.
- Nambiar, Sudhir,Daeuble, John F.,Doyle, Ronald J.,Taylor, K. Grant
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p. 2179 - 2182
(2007/10/02)
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- SYSTEMATIC CHEMICAL SYNTHESIS AND N.M.R. SPECTRA OF METHYL α-GLYCOSIDES OF ISOMALTO-OLIGOSACCHARIDES AND RELATED COMPOUNDS
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Acid-catalyzed thiophenolysis of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D-glucopyranose and acetylation of the resulting phenyl 2,3,4-tri-O-benzyl-1-thio-α-D-glucopyranoside (4) gave phenyl 6-O-acetyl-2,3,4-tri-O-benzyl-1-thio-α-D-glucopyranoside (5).Reaction of 5 with chlorine gave, stereospecifically, the corresponding β-glycosyl chloride, which was treated with 4 in the presence of silver perchlorate and 2,4,6-trimethylpyridine to afford phenyl O-(6-O-acetyl-2,3,4-tri-O-benzyl-α-D-glucopyranosyl)-(1->6)-2,3,4-tri-O-benzyl-1-thio-α-D-glucopyranoside (17).Crystalline O-(6-O-acetyl-2,3,4-tri-O-benzyl-α-D- glucopyranosyl)-(1->6)-2,3,4-tri-O-benzyl-β-D-glucopyranosyl chloride, readily obtainable in a stereospecific manner from 17 by treatment with chlorine, was used as the key glycosyl (isomaltosyl) donor in the bockwise synthesis of methyl glycosides of isomalto-oligosaccharides, up to and including the octasaccharide.The methyl α-glycoside of isomaltotetraose fluorinated at C-6 of the terminal D glucopyranosyl group was prepared by using SnCl2-activated 2,3,4-tri-O-benzyl-6-deoxy-6-fluoro-α,β-D-glucopyranosyl fluoride as the glycosyl donor, a suitably protected methyl α-isomaltotrioside as the nucleophile, and silver perchlorate as the promoter.The n.m.r. spectra (1H- and 13C-) of numereous synthetic intermediates were analyzed and completely assigned by a variety of two-dimensional homo- and hetero-nuclear n.m.r.-spectroscopic techniques, and the final deprotected title oligosaccharides were characterized by 13C-n.m.r. data.Silver perchlorate-mediated glycosylation reactions involving β-glycosyl chlorides were high-yielding and showed high stereoselectivity for the formation of an α-(cis)-glycosidic linkage.The practical limitation of obtaining high isomalto-oligosaccharides in this way appears to lie solely in the separation technique applied for the resolution of the crude products formed.
- Kovac, Pavol,Lerner, Laura
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- HYDROGENOLYSIS OF THE BENZYLIDENE ACETALS OF THIOGLYCOSIDES WITH THE LiAlH4-AlCl3 REAGENT. SYNTHESIS OF PARTIALLY BENZYLATED THIOGLYCOSIDE DERIVATIVES
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Reductive hydrogenolysis of phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1-thio-β-D-gluco- (4) and -galactopyranoside (8) and phenyl 2,3,6,2',3'-penta-O-benzyl-4',6'-O-benzylidene-1-thio-β-cellobioside (15) with the LiAlH4-AlCl3 reagent resulted in the corres
- Liptak, A.,Jodal, I.,Harangi, J.,Nanasi, P.
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p. 415 - 422
(2007/10/02)
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