PubMed:20860359 JSONTXT

{"project":"Glycan-GlyCosmos","denotations":[{"id":"T1","span":{"begin":280,"end":286},"obj":"Glycan"},{"id":"T2","span":{"begin":1702,"end":1708},"obj":"Glycan"}],"attributes":[{"id":"A1","pred":"glycosmos_id","subj":"T1","obj":"https://glycosmos.org/glycans/show/G39738WL"},{"id":"A3","pred":"image","subj":"T1","obj":"https://api.glycosmos.org/wurcs2image/latest/png/binary/G39738WL"},{"id":"A2","pred":"glycosmos_id","subj":"T2","obj":"https://glycosmos.org/glycans/show/G39738WL"},{"id":"A4","pred":"image","subj":"T2","obj":"https://api.glycosmos.org/wurcs2image/latest/png/binary/G39738WL"}],"text":"Nickel-catalyzed stereoselective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates for the formation of 1,2-cis-2-amino glycosides. Applications to the synthesis of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GalNAc.\nThe 1,2-cis-2-amino glycosides are key components found within a variety of biologically important oligosaccharides and glycopeptides. Although there are remarkable advances in the synthesis of 1,2-cis-2-amino glycosides, disadvantages of the current state-of-the-art methods include limited substrate scope, low yields, long reaction times, and anomeric mixtures. We have developed a novel method for the synthesis of 1,2-cis-2-amino glycosides via nickel-catalyzed α-selective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates. These glycosyl donors are capable of coupling to a wide variety of alcohols to provide glycoconjugates in high yields with excellent levels of α-selectivity. Additionally, only a substoichiometric amount of nickel (5-10 mol %) is required for the reaction to occur at 25 °C. The current nickel method relies on the nature of the nickel-ligand complex to control the α-selectivity. The reactive sites of the nucleophiles or the nature of the protecting groups have little effect on the α-selectivity. This methodology has also been successfully applied to both disaccharide donors and acceptors to provide the corresponding oligosaccharides in high yields and α-selectivity. The efficacy of the nickel procedure has been further applied toward the preparation of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GluNAc/GalNAc. Mechanistic studies suggest that the presence of the substituted benzylidene functionality at the C(2)-amino position of glycosyl donors is crucial for the high α-selectivity observed in the coupling products. Additionally, the α-orientation of the C(1)-trichloroacetimidate group on glycosyl donors is necessary for the coupling process to occur."}

{"project":"GlyCosmos15-Sentences","blocks":[{"id":"T1","span":{"begin":0,"end":185},"obj":"Sentence"},{"id":"T2","span":{"begin":186,"end":287},"obj":"Sentence"},{"id":"T3","span":{"begin":288,"end":422},"obj":"Sentence"},{"id":"T4","span":{"begin":423,"end":652},"obj":"Sentence"},{"id":"T5","span":{"begin":653,"end":871},"obj":"Sentence"},{"id":"T6","span":{"begin":872,"end":1029},"obj":"Sentence"},{"id":"T7","span":{"begin":1030,"end":1252},"obj":"Sentence"},{"id":"T8","span":{"begin":1253,"end":1371},"obj":"Sentence"},{"id":"T9","span":{"begin":1372,"end":1545},"obj":"Sentence"},{"id":"T10","span":{"begin":1546,"end":1709},"obj":"Sentence"},{"id":"T11","span":{"begin":1710,"end":1919},"obj":"Sentence"},{"id":"T12","span":{"begin":1920,"end":2057},"obj":"Sentence"}],"text":"Nickel-catalyzed stereoselective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates for the formation of 1,2-cis-2-amino glycosides. Applications to the synthesis of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GalNAc.\nThe 1,2-cis-2-amino glycosides are key components found within a variety of biologically important oligosaccharides and glycopeptides. Although there are remarkable advances in the synthesis of 1,2-cis-2-amino glycosides, disadvantages of the current state-of-the-art methods include limited substrate scope, low yields, long reaction times, and anomeric mixtures. We have developed a novel method for the synthesis of 1,2-cis-2-amino glycosides via nickel-catalyzed α-selective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates. These glycosyl donors are capable of coupling to a wide variety of alcohols to provide glycoconjugates in high yields with excellent levels of α-selectivity. Additionally, only a substoichiometric amount of nickel (5-10 mol %) is required for the reaction to occur at 25 °C. The current nickel method relies on the nature of the nickel-ligand complex to control the α-selectivity. The reactive sites of the nucleophiles or the nature of the protecting groups have little effect on the α-selectivity. This methodology has also been successfully applied to both disaccharide donors and acceptors to provide the corresponding oligosaccharides in high yields and α-selectivity. The efficacy of the nickel procedure has been further applied toward the preparation of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GluNAc/GalNAc. Mechanistic studies suggest that the presence of the substituted benzylidene functionality at the C(2)-amino position of glycosyl donors is crucial for the high α-selectivity observed in the coupling products. Additionally, the α-orientation of the C(1)-trichloroacetimidate group on glycosyl donors is necessary for the coupling process to occur."}

{"project":"GlyCosmos15-Glycan","denotations":[{"id":"T1","span":{"begin":280,"end":286},"obj":"Glycan"},{"id":"T2","span":{"begin":1702,"end":1708},"obj":"Glycan"}],"attributes":[{"id":"A1","pred":"glycosmos_id","subj":"T1","obj":"https://glycosmos.org/glycans/show/G39738WL"},{"id":"A3","pred":"image","subj":"T1","obj":"https://api.glycosmos.org/wurcs2image/latest/png/binary/G39738WL"},{"id":"A2","pred":"glycosmos_id","subj":"T2","obj":"https://glycosmos.org/glycans/show/G39738WL"},{"id":"A4","pred":"image","subj":"T2","obj":"https://api.glycosmos.org/wurcs2image/latest/png/binary/G39738WL"}],"text":"Nickel-catalyzed stereoselective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates for the formation of 1,2-cis-2-amino glycosides. Applications to the synthesis of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GalNAc.\nThe 1,2-cis-2-amino glycosides are key components found within a variety of biologically important oligosaccharides and glycopeptides. Although there are remarkable advances in the synthesis of 1,2-cis-2-amino glycosides, disadvantages of the current state-of-the-art methods include limited substrate scope, low yields, long reaction times, and anomeric mixtures. We have developed a novel method for the synthesis of 1,2-cis-2-amino glycosides via nickel-catalyzed α-selective glycosylation with C(2)-N-substituted benzylidene D-glucosamine and galactosamine trichloroacetimidates. These glycosyl donors are capable of coupling to a wide variety of alcohols to provide glycoconjugates in high yields with excellent levels of α-selectivity. Additionally, only a substoichiometric amount of nickel (5-10 mol %) is required for the reaction to occur at 25 °C. The current nickel method relies on the nature of the nickel-ligand complex to control the α-selectivity. The reactive sites of the nucleophiles or the nature of the protecting groups have little effect on the α-selectivity. This methodology has also been successfully applied to both disaccharide donors and acceptors to provide the corresponding oligosaccharides in high yields and α-selectivity. The efficacy of the nickel procedure has been further applied toward the preparation of heparin disaccharides, GPI anchor pseudodisaccharides, and α-GluNAc/GalNAc. Mechanistic studies suggest that the presence of the substituted benzylidene functionality at the C(2)-amino position of glycosyl donors is crucial for the high α-selectivity observed in the coupling products. Additionally, the α-orientation of the C(1)-trichloroacetimidate group on glycosyl donors is necessary for the coupling process to occur."}