- 2-Isocyano glucose used in Ugi four-component reaction: An approach to enhance inhibitory effect against DNA oxidation
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The Ugi four-component-reaction (Ugi 4CR) allowed synthesizing bisamide from carboxylic acid, aldehyde, amine, and isocyanide in one-pot operation. However, introducing 2-isocyano glucose into the Ugi 4CR and investigating the inhibitory effects of Ugi adducts against radical-induced oxidation of DNA remained technical challenges. We herein applied 2-isocyano glucose (acetylation of hydroxy groups) to perform a catalyst-free Ugi 4CR at room temperature. The gallic, ferulic, caffeic, or p-hydroxybenzoic acids, aniline (or benzylamine and p-aminophenol), and formaldehyde acted as reagents. In the case of inhibiting DNA oxidations induced by 2,2’-azobis(2-amidinopropane hydrochloride) (AAPH), hydroxy radical, and Cu2+/glutathione, the Ugi adduct containing glucose moiety exhibited higher antioxidative activities than the structural analog without glucose moiety involved. It was also proved that high antioxidative property was owing to hydroxy groups in glucose moiety. Therefore, sugar-appended Ugi adducts might hold promising inhibitors for DNA oxidation.
- Zhao, Peng-Fei,Liu, Zai-Qun
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p. 458 - 466
(2017/05/05)
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- 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
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The 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.
- Mensah, Enoch A.,Yu, Fei,Nguyen, Hien M.
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supporting information; experimental part
p. 14288 - 14302
(2010/12/19)
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- Nickel-catalyzed stereoselective formation of α-2-deoxy-2-amino glycosides
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(Chemical Equation Presented) The development of a new method for the stereoselective synthesis of α-2-deoxy-2-amino glycosides is described. This methodology relies on the nature of the cationic nickel catalyst, generated in situ from LnNiCl2 and AgOTf, to direct the anomeric stereoselectivity. The new glycosylation reaction is highly α-selective and proceeds under mild conditions with 5-10 mol % of the nickel catalyst loading at ambient temperature. This new method has been applied to both D-glucosamine and galactosamine trichloroacetimidate donors as well as an array of primary, secondary, and tertiary alcohol nucleophiles to provide the desired glycoconjugates in good yields with excellent α-selectivity. Mechanistic studies of the present reaction are underway and will be reported in due course. Copyright
- Mensah, Enoch A.,Nguyen, Hien M.
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supporting information; experimental part
p. 8778 - 8780
(2009/12/04)
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- Synthesis of differentially protected glucosamine building blocks and their evaluation as glycosylating agents
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The modular assembly of heparin oligosaccharides requires glucosamine building blocks with amine protecting groups for α-selective glycosylations that can be readily removed. The synthesis of N-4-nitrobenzensulphonamide (nosyl)- and N-2,4-dinitrophenyl (DNP)-protected glucosamine building blocks and their evaluation as glycosylating agents is described. The N-nosyl-protected glucosamine building blocks were challenging to prepare and their glycosylations resulted in inseparable mixtures of products. The N-DNP-protected glucosamines, however, were readily synthesized and resulted in α-selective couplings to protected l-iduronic acid derivatives.
- Bindschaedler, Pascal,Dialer, Lukas O.,Seeberger, Peter H.
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experimental part
p. 395 - 420
(2011/06/19)
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- N-p-methoxybenzylidene derivatives of 2-amino-2-deoxy-D-glucose as glycosyl donors: a reinvestigation.
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6-O-Acetyl-3,4-di-O-benzyl-2-deoxy-2-p-methoxybenzylideneamino-D- glucopyranosyl chloride, 3,4,6-tri-O-acetyl-2-deoxy-2-p-methoxybenzylideneamino-alpha-D-glu copyranosyl bromide, 3,4,6-tri-O-acetyl-2-deoxy-2-p-methoxybenzylideneamino-alpha- and -beta-D- g
- Marra,Sinay
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p. 319 - 337
(2007/10/02)
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