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Clay S. Bennett - One of the best experts on this subject based on the ideXlab platform.
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reagent controlled direct dehydrative glycosylation with 2 Deoxy Sugars construction of the saquayamycin z pentasaccharide
Organic Letters, 2019Co-Authors: Colin J Mizia, Clay S. BennettAbstract:The first synthesis of the pentasaccharide fragment of the angucycline antibiotic saquayamycin Z is described. By using our sulfonyl chloride mediated reagent controlled dehydrative glycosylation, we are able to assemble the glycosidic linkages with high levels of anomeric selectivity. The total synthesis was completed in 25 total steps, and in 2.5% overall yield with a longest linear sequence of 15 steps.
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a reagent controlled sn2 glycosylation for the direct synthesis of β linked 2 Deoxy Sugars
ChemInform, 2014Co-Authors: John Paul Issa, Clay S. BennettAbstract:p-Toluenesulfonic anhydride activates both 2-Deoxy- and 2,6-Deoxy-Sugars in situ as electrophilic species, which react stereoselectively with nucleophilic acceptors to produce β-anomers exclusively.
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a reagent controlled sn2 glycosylation for the direct synthesis of β linked 2 Deoxy Sugars
Journal of the American Chemical Society, 2014Co-Authors: John Paul Issa, Clay S. BennettAbstract:The efficient and stereoselective construction of glycosidic linkages remains one of the most formidable challenges in organic chemistry. This is especially true in cases such as β-linked Deoxy-Sugars, where the outcome of the reaction cannot be controlled using the stereochemical information intrinsic to the glycosyl donor. Here we show that p-toluenesulfonic anhydride activates 2-Deoxy-sugar hemiacetals in situ as electrophilic species, which react stereoselectively with nucleophilic acceptors to produce β-anomers exclusively. NMR studies confirm that, under these conditions, the hemiacetal is quantitatively converted into an α-glycosyl tosylate, which is presumably the reactive species in the reaction. This approach demonstrates that use of promoters that activate hemiacetals as well-defined intermediates can be used to permit stereoselective glycosylation through an SN2-pathway.
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Reagent Controlled β-Specific Dehydrative Glycosylation Reactions with 2-Deoxy-Sugars.
ChemInform, 2013Co-Authors: John Paul Issa, Dina Lloyd, Emily Steliotes, Clay S. BennettAbstract:It is demonstrated that 2-Deoxysugar hemiacetals react with 1-tosyl-4-nitroimidazol to generate intermediates which react with S- or O-nucleophiles to give β-glycosides exclusively.
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reagent controlled β specific dehydrative glycosylation reactions with 2 Deoxy Sugars
Organic Letters, 2013Co-Authors: John Paul Issa, Dina Lloyd, Emily Steliotes, Clay S. BennettAbstract:N-Sulfonyl imidazoles activate 2-Deoxy-sugar hemiacetals for glycosylation presumably by converting them into glycosyl sulfonates in situ. By matching the leaving group ability of the sulfonate with the reactivity of the donor, it is possible to obtain β-specific glycosylation reactions. The reaction serves as proof of the principle that, by choosing promoters that can modulate the reactivity of active intermediates, it is possible to place glycosylation reactions entirely under reagent control.
John Paul Issa - One of the best experts on this subject based on the ideXlab platform.
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a reagent controlled sn2 glycosylation for the direct synthesis of β linked 2 Deoxy Sugars
ChemInform, 2014Co-Authors: John Paul Issa, Clay S. BennettAbstract:p-Toluenesulfonic anhydride activates both 2-Deoxy- and 2,6-Deoxy-Sugars in situ as electrophilic species, which react stereoselectively with nucleophilic acceptors to produce β-anomers exclusively.
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a reagent controlled sn2 glycosylation for the direct synthesis of β linked 2 Deoxy Sugars
Journal of the American Chemical Society, 2014Co-Authors: John Paul Issa, Clay S. BennettAbstract:The efficient and stereoselective construction of glycosidic linkages remains one of the most formidable challenges in organic chemistry. This is especially true in cases such as β-linked Deoxy-Sugars, where the outcome of the reaction cannot be controlled using the stereochemical information intrinsic to the glycosyl donor. Here we show that p-toluenesulfonic anhydride activates 2-Deoxy-sugar hemiacetals in situ as electrophilic species, which react stereoselectively with nucleophilic acceptors to produce β-anomers exclusively. NMR studies confirm that, under these conditions, the hemiacetal is quantitatively converted into an α-glycosyl tosylate, which is presumably the reactive species in the reaction. This approach demonstrates that use of promoters that activate hemiacetals as well-defined intermediates can be used to permit stereoselective glycosylation through an SN2-pathway.
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Reagent Controlled β-Specific Dehydrative Glycosylation Reactions with 2-Deoxy-Sugars.
ChemInform, 2013Co-Authors: John Paul Issa, Dina Lloyd, Emily Steliotes, Clay S. BennettAbstract:It is demonstrated that 2-Deoxysugar hemiacetals react with 1-tosyl-4-nitroimidazol to generate intermediates which react with S- or O-nucleophiles to give β-glycosides exclusively.
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reagent controlled β specific dehydrative glycosylation reactions with 2 Deoxy Sugars
Organic Letters, 2013Co-Authors: John Paul Issa, Dina Lloyd, Emily Steliotes, Clay S. BennettAbstract:N-Sulfonyl imidazoles activate 2-Deoxy-sugar hemiacetals for glycosylation presumably by converting them into glycosyl sulfonates in situ. By matching the leaving group ability of the sulfonate with the reactivity of the donor, it is possible to obtain β-specific glycosylation reactions. The reaction serves as proof of the principle that, by choosing promoters that can modulate the reactivity of active intermediates, it is possible to place glycosylation reactions entirely under reagent control.
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halide effects on cyclopropenium cation promoted glycosylation with Deoxy Sugars highly α selective glycosylations using a 3 3 dibromo 1 2 diphenylcyclopropene promoter
ChemInform, 2013Co-Authors: Jason M Nogueira, John Paul Issa, Anhsiang Adam Chu, Jordan A Sisel, Ryan S Schum, Clay S. BennettAbstract:α-Selective dehydrative glycosylations of 2-Deoxy sugar donors are achieved using a new cyclopropenium cation promoter system.
Pilar Garcia Mendoza - One of the best experts on this subject based on the ideXlab platform.
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Application of the Hofmann rearrangement in the synthesis of 3-amino sugar derivatives: preparation of some 3-tert-butoxycarbonylamino-3-cyano-3-Deoxy and 3-acetamido-methyl-3-tert-butoxycarbonylamino-3-Deoxy Sugars
Carbohydrate Research, 1991Co-Authors: Francisco Santoyo González, Antonio Vargas Berenguel, Fernando Hernández Mateo, Pilar Garcia MendozaAbstract:Abstract The cyclisation of dialdehydes, obtained from Sugars, with cyanoacetamide and subsequent Hofmann rearrangement is a convenient and short approach to the synthesis of 3-amino sugar derivatives branched at C-3. Thus, derivatives of 3-carbamoyl-3-cyano-3-Deoxy Sugars 1–4 were transformed into N-protected 3-amino-3-cyano-3-Deoxy Sugars 5–8 by Hofmann rearrangement (lead tetra-acetate-N,N-dimethylformamide-tert-butyl alcohol). Reduction of the cyano group in these compounds (NaBH4-CoCl2) gave, after acetylation, the corresponding 1,2-diamino derivatives 13–16.
Antonio Vargas-berenguel - One of the best experts on this subject based on the ideXlab platform.
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Reductive decyanation of 3-amino-3-cyano-3-Deoxy Sugars with sodium borohydride. A new approach to 3-amino-3-Deoxy Sugars.
Tetrahedron Letters, 1991Co-Authors: Francisco Santoyo-gonzalez, Fernando Hernandez-mateo, Antonio Vargas-berenguelAbstract:Abstract 3-Amino-3-cyano-3-Deoxy Sugars obtained cyclization of dialdehydes with cyanoacetamide and Hofmann rearrangement were reductively decyanated using sodium borohydride providing a new approach to 3-amino-3-Deoxy Sugars.
Daniel J Repeta - One of the best experts on this subject based on the ideXlab platform.
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periodate oxidation of marine high molecular weight dissolved organic matter evidence for a major contribution from 6 Deoxy and methyl Sugars
Marine Chemistry, 2007Co-Authors: T M Quan, Daniel J RepetaAbstract:Abstract Nuclear magnetic resonance spectroscopy has been used to infer that marine high molecular weight dissolved organic matter (HMWDOM) is a mixture of carbohydrates, proteins, and lipids. However, acid and base catalyzed hydrolysis of HMWDOM followed by molecular level analyses using gas and liquid chromatography provide only low to modest yields of simple Sugars, amino acids, and lipids. Here we use periodate over-oxidation to investigate the composition of HMWDOM. Our analyses show that the oxidation of HMWDOM carbohydrate consumes more periodate per carbon on a molar basis (1.3:1) than simple Sugars (0.8:1) or linear polysaccharides (1.0:1), and that HMWDOM is highly branched. We also recover acetic acid and methanol as major oxidation products. Methanol and acetic acid are derived from the oxidation of methyl and 6-Deoxy Sugars, and our analyses suggest these Sugars are major components of HMWDOM. Periodate over-oxidation shows that lipids are not major constituents of HMWDOM, and that most of the alkyl carbon observed in the 13CNMR spectra between 0–45 ppm that has been previously assigned to lipids is due to the methyl carbons of acetamide and 6-Deoxy Sugars.