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Aniko Borbas - One of the best experts on this subject based on the ideXlab platform.
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systematic study on free radical hydrothiolation of unsaturated Monosaccharide Derivatives with exo and endocyclic double bonds
ChemInform, 2013Co-Authors: Laszlo Lazar, Magdolna Csavas, Adam Hadhazi, Mihaly Herczeg, Marietta Toth, Laszlo Somsak, Terezia Barna, Pal Herczegh, Aniko BorbasAbstract:The photoinduced radical-mediated hydrothiolation reactions show highly varying overall conversions depending not only on the substitution pattern and electron-density of the double bond but also on the nature and the substitution pattern of the thiol partner.
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systematic study on free radical hydrothiolation of unsaturated Monosaccharide Derivatives with exo and endocyclic double bonds
Organic and Biomolecular Chemistry, 2013Co-Authors: Laszlo Lazar, Magdolna Csavas, Adam Hadhazi, Mihaly Herczeg, Marietta Toth, Laszlo Somsak, Terezia Barna, Pal Herczegh, Aniko BorbasAbstract:Exo- and endocyclic double bonds of glycals and terminal double bonds of enoses were reacted with various thiols by irradiation with UV light in the presence of a cleavable photoinitiator. The photoinduced radical-mediated hydrothiolation reactions showed highly varying overall conversions depending not only on the substitution pattern and electron-density of the double bond but also on the nature and substitution pattern of the thiol partner. Out of the applied thiols thiophenol, producing the highly stabilized thiyl radical, exhibited the lowest reactivity toward each type of alkene. In most cases, the hydrothiolations took place with full regio- and stereoselectivities. Successful addition of 1,2 : 3,4-di-O-isopropylidene-6-thio-α-D-galactopyranose to a 2,3-unsaturated N-acetylneuraminic acid derivative, providing a (3 → 6)-S-linked pseudodisaccharide, demonstrated that the endocyclic double bond of Neu5Ac-2-ene, bearing an electron-withdrawing substituent, shows sufficient reactivity in the photoinduced thiol–ene coupling reaction.
Peter Norris - One of the best experts on this subject based on the ideXlab platform.
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Reactions of several Monosaccharide-derived alcohols with p-acetamidobenzenesulfonyl azide and DBU
Tetrahedron Letters, 2011Co-Authors: Iulia Sacui, Peter NorrisAbstract:Abstract Attempted diazo transfer to 1-O-(2-phenylacetyl)-2,3;5,6-di-O-isopropylidene-α- d -mannofuranose using p-acetamidobenzenesulfonyl azide (p-ABSA) and DBU as base affords 1-O-(2-diazo-2-phenylacetyl)-2,3;5,6-di-O-isopropylidene-α- d -mannofuranose in low yield along with 2,3;5,6-di-O-isopropylidene-α- d -mannofuranose, 1-azido-2,3;5,6-di-O-isopropylidene-β- d -mannofuranose, as well as the unreacted starting material. The azido sugar likely arises from α-mannofuranosyl sulfonate ester formation, through displacement of azide from p-ABSA by the sugar lactol, followed by stereospecific displacement by azide anion on the furanosyl sulfonate ester. This outcome has been studied further with the conditions being applied to several common Monosaccharide Derivatives. Accessible substrates afford the azido sugar in an overall one-pot alcohol-to-azide conversion, while hindered substrates yield the sulfonate esters.
Kristopher Williams - One of the best experts on this subject based on the ideXlab platform.
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regioselective esterification of vicinal diols on Monosaccharide Derivatives via mitsunobu reactions
Organic Letters, 2008Co-Authors: Guijun Wang, Jeanrene Ellamenye, Michael St Martin, Hao Yang, Kristopher WilliamsAbstract:We have carried out a series of esterification reactions of secondary alcohols derived from d-glucose, d-mannose, and d-galactose via the Mitsunobu reaction. The benzoylation reaction of vicinal diols derived from Monosaccharides under Mitsunobu conditions afforded monobenzoates with retention of stereochemistry only. The regioselectivity of these reactions depends on the stereochemistry of the sugar starting material. The Mitsunobu reactions on these diols may be used for the selective protection of other vicinal secondary hydroxyl groups.
Masahiko Inouye - One of the best experts on this subject based on the ideXlab platform.
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Nonplanar Macrocycle Consisting of Four Pyridine and Phenol Units Connected with Acetylene Bonds Displaying Preferential Binding to Maltoside over Monosaccharides
The Journal of organic chemistry, 2018Co-Authors: Yuki Ohishi, Naoto Yamamoto, Hajime Abe, Masahiko InouyeAbstract:A nonplanar macrocycle consisting of four pyridine–acetylene–phenol units was developed as a host for saccharide guest molecules. The macrocycle was found to strongly associate with a lipophilic maltose derivative, with an association constant of 107 M–1, over Monosaccharide Derivatives, for which much smaller association constants were determined, ranging from 103 M–1 to 104 M–1. The macrocycle was found to adopt a boat-like conformation, encapsulating β-d-maltoside in a twisted manner through approximately seven intermolecular hydrogen bonds.
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Nonplanar Macrocycle Consisting of Four Pyridine and Phenol Units Connected with Acetylene Bonds Displaying Preferential Binding to Maltoside over Monosaccharides
2018Co-Authors: Yuki Ohishi, Naoto Yamamoto, Hajime Abe, Masahiko InouyeAbstract:A nonplanar macrocycle consisting of four pyridine–acetylene–phenol units was developed as a host for saccharide guest molecules. The macrocycle was found to strongly associate with a lipophilic maltose derivative, with an association constant of 107 M–1, over Monosaccharide Derivatives, for which much smaller association constants were determined, ranging from 103 M–1 to 104 M–1. The macrocycle was found to adopt a boat-like conformation, encapsulating β-d-maltoside in a twisted manner through approximately seven intermolecular hydrogen bonds
Balaram Mukhopadhyay - One of the best experts on this subject based on the ideXlab platform.
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Linear synthesis of the hexasaccharide related to the repeating unit of the O-antigen from Shigella flexneri serotype 1d (I: 7,8)
Carbohydrate Research, 2016Co-Authors: Ankita Mitra, Balaram MukhopadhyayAbstract:Total synthesis of the hexasaccharide repeating unit of the O-antigen from Shigella flexneri serotype 1d (I: 7,8), α-D-Glcp-(1→3)-α-L-Rhap-(1→2)-α-L-Rhap-(1→3)-α-L-Rhap-(1→3)-[α-D-Glcp-(1→4)]-β-D-GlcpNAc, is reported by following a linear strategy. The target hexasaccharide was synthesized by sequential glycosylations of suitably protected Monosaccharide Derivatives prepared from commercially available Monosaccharides through rational protecting group manipulations. Stereoselective glycosylations were accomplished by the activation of thioglycoside using N-iodosuccinimide and H2SO4-silica. The use of H2SO4-silica in place of traditional promoters like TfOH or TMSOTf was proved to be a better option for the NIS-mediated thioglycoside activation.