title: Stereoselective palladium-catalyzed O-glycosylation using glycals.
abstract: A highly stereoselective palladium-catalyzed O-glycosylation reaction is described. The reaction of a glycal 3-acetate or carbonate with the zinc(II) alkoxide of acceptors establishes the glycosidic linkage under palladium catalysis to give rise to disaccharides as the product in good yields and with high stereoselectivity. In contrast to the Lewis acid mediated Ferrier procedure, the anomeric stereochemistry of this reaction is controlled by the employed ligand. Whereas the use of a complex of palladium acetate and 2-di(tert-butyl)phosphinobiphenyl as the catalyst results in the exclusive beta-glycoside formation, the same reaction using trimethyl phosphite ligand furnishes an alpha-anomer as the major product. The utility of the 2,3-unsaturation present in the resulting glycoside is demonstrated by the further transformations such as dihydroxylation, hydration, and hydrogenation reactions. Thus, the combination of the glycosylation and subsequent functionalization provides a novel entry to saccharides which are otherwise difficult to prepare. The broad scope of the process, mildness of the reaction conditions, and experimental simplicity should make this method a useful tool in synthetic carbohydrate chemistry.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Hahn
authors.initials: H
authors.lastname: Kim
authors.forename: Hongbin
authors.initials: H
authors.lastname: Men
authors.forename: Chulbom
authors.initials: C
authors.lastname: Lee
mesh_terms: D002384:Catalysis; D004187:Disaccharides / Q000138:chemical synthesis; D006027:Glycosides / Q000138:chemical synthesis*; D006031:Glycosylation; D010165:Palladium / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D004187:Disaccharides; D006027:Glycosides; D010165:Palladium