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    Copper-Catalyzed Stereoselective Synthesis of 2-Deoxygalactosides
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    Abstract:
    An efficient glycosylation method to synthesize 2-deoxy-O-galactosides based on a Cu(II)-catalyzed reaction without additional ligand has been developed. The glycosylation was amenable to different protected glycal donors and a wide range of acceptors including alcohols, amino acids, sugars, and phenol, and proceeds with excellent yield and high α-selectivity under mild conditions. The reaction proceeds readily on a gram scale, and its versatility is exemplified in the synthesis of oligosaccharides.
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    Glycal
    2-Deoxy ketopyranoses were prepared in very good yields and excellent stereoselectivity by a onepot procedure involving the iodohydroxylation of exo-glycals and removal of the iodide group using sodium dithionite. Keywords: Sodium dithionite, Stereoselectivity, Ketopyranose, Iodohydroxylation, exo-Glycal
    Sodium dithionite
    Sodium iodide
    Glycal
    A remarkably stereoselective reduction of a γ-hydroxyketone with two equiv. of lithium triethylborohydride has been observed and this effect has been suggested to originate from 'chelation control'; the reaction has been utilised in a short stereoselective synthesis of ancistrofuran.
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    The glycosidations of silylated glycals and alcohols using a catalytic amount of BCl3 or BBr3 proceeded under mild conditions in a highly stereoselective fashion to afford the corresponding 2-deoxy-α-glycosides in high yields which were often found as the glycosidic components of several bioactive natural products.
    Glycosidic bond
    Citations (39)
    The effect of a 3-O-acetyl group on the stereoselectivity of α-glycosylation with 2-O-benzylated d-gluco glycosyl donors was studied. It was shown that 3-O-acetylated donors gave α-anomers predominantly or exclusively, whereas glycosylation with the corresponding per-O-benzylated donors afforded mixtures of comparable amounts of α- and β-anomers. The higher α-stereoselectivity in the first case was accounted for by the remote anchimeric assistance of the 3-O-acetyl group, which was confirmed by theoretical calculations.
    Glycosyl donor
    Chemoselectivity
    Citations (23)
    Quick access to various unnatural 3-amino-2,3,6-trideoxy sugars was achieved by sequential functionalization of a glycal intermediate. This strategy and the further glycosylation method allowed the efficient late-stage modification of bioactive natural products and drugs.
    Glycal
    Surface Modification
    Citations (14)
    A nonclassical, totally stereoselective synthesis of orthogonally protected 1,3-disaccharides is reported. Enantiomerically pure β-keto-δ-lactones, efficiently obtained from glucal and galactal, are transformed into electron-poor heterodienes and chemo-, regio-, and stereoselectively cycloadded to glycals as electron-rich dienophiles, to directly afford 2-thiodisaccharides. The reductive desulfurization of the latter smoothly gave the corresponding 2,2‘-dideoxydisaccharides.
    Glucal
    Glycal
    Disaccharide
    Citations (17)
    Abstract In the presence of a catalytic amount of several trityl salts, 2,3,5-tri-O-benzyl-d-ribofuranose smoothly reacted with alcohols to give various β-ribofuranosides in high yields with high stereoselectivity while reversed stereoselectivity was observed in the coexistence of lithium perchlolate.
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