title: Glycosylation with 2-Acetamido-2-deoxyglycosyl Donors at a Low Temperature: Scope of the Non-Oxazoline Method.
abstract: A direct construction of 1,2-trans-β-linked 2-acetamido-2-deoxyglycosides was investigated. The 3,4,6-tri-O-benzyl- and 3,4,6-tri-O-acetyl-protected glycosyl diethyl phosphites and 4,6-O-benzylidene-protected galactosyl diethyl phosphite each reacted with a variety of acceptor alcohols in the presence of a stoichiometric amount of Tf2NH in CH2Cl2 at -78 °C to afford the corresponding β-glycosides in good to high yields with complete stereoselectivity. Some experiments provided strong evidence that the corresponding oxazolinium ions are not responsible for the reaction. We demonstrated that glycosylations with the corresponding glycosyl imidate and thioglycoside also proceeded at a low temperature, indicating the possibility of these donors being attractive alternatives to the phosphite. A plausible reaction mechanism, which features glycosyl triflimide and contact ion pair as reactive intermediates, is proposed on the basis of the results obtained with 2-acetamido-2-deoxymannosyl donors.
authors: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors: Ryoichi
authors: R
authors: Arihara
authors: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors: Kosuke
authors: K
authors: Kakita
authors: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors: Noritoshi
authors: N
authors: Suzuki
authors: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors: Seiichi
authors: S
authors: Nakamura
authors: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
authors: Shunichi
authors: S
authors: Hashimoto
mesh_terms: D000117:Acetylglucosamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D002236:Carbohydrate Conformation; D006031:Glycosylation; D013696:Temperature
chemical_list: D000117:Acetylglucosamine