title: Pyranosides with 2,3-trans carbamate groups: exocyclic or endocyclic cleavage reaction?
abstract: Pyranosides with 2,3-trans carbamate groups exhibit high 1,2-cis selectivity in glycosylation reactions. Using glycosyl donors with N-benzyl 2,3-trans carbamate groups, an anti-Helicobacter pylori oligosaccharide was synthesized in an efficient manner. Moreover, pyranosides with 2,3-trans carbamate groups readily undergo anomerization from the β to the α configuration under mild acidic conditions via endocyclic cleavage. Acyclic cations generated during the endocyclic cleavage reaction were captured using reduction and intramolecular Friedel-Crafts reaction. By exploiting this anomerization, multiply aligned 1,2-trans glycosyl bonds can be transformed to 1,2-cis glycosyl bonds in a single operation.
authors.affiliation: RIKEN, Synthetic Cellular Chemistry Laboratory, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan. smanabe@riken.jp.
authors.forename: Shino
authors.initials: S
authors.lastname: Manabe
authors.forename: Yukishige
authors.initials: Y
authors.lastname: Ito
mesh_terms: D002219:Carbamates / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry; D006031:Glycosylation; D007536:Isomerism; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D002219:Carbamates; D006027:Glycosides; D009844:Oligosaccharides
keywords: anomerization; carbohydrates; endocyclic cleavage; glycosylation; oligosaccharides