title: Application of silver N-heterocyclic carbene complexes in O-glycosidation reactions.
abstract: We report the efficient O-glycosidation of glycosyl bromides with therapeutically relevant acceptors facilitated by silver N-heterocyclic carbene (Ag-NHC) complexes. A set of four Ag-NHC complexes was synthesized and evaluated as promoters for glycosidation reactions. Two new bis-Ag-NHC complexes derived from ionic liquids 1-benzyl-3-methyl-1H-imidazolium chloride and 1-(2-methoxyethyl)-3-methylimidazolium chloride were found to efficiently promote glycosidation, whereas known mono-Ag complexes of 1,3-bis(2,4,6-trimethylphenyl)imidazolium chloride and 1,3-bis(2,6-di-isopropylphenyl)imidazolium chloride failed to facilitate the reaction. The structures of the promoters were established by X-ray crystallography and these complexes were employed in the glycosidation of different glycosyl bromide donors with biologically valuable acceptors, such as estrone, estradiol, and various flavones. The products were obtained in yields considered good to excellent, and all reactions were highly selective for the β isomer regardless of neighboring group effects.
authors.affiliation: Laboratory of Synthetic Chemistry, SAIC-Frederick Inc., National Cancer Institute at Frederick, 1050 Boyles Street, Frederick, MD-21702, United States.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Talisman
authors.forename: Vineet
authors.initials: V
authors.lastname: Kumar
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Deschamps
authors.forename: Mark
authors.initials: M
authors.lastname: Frisch
authors.forename: Sanjay V
authors.initials: SV
authors.lastname: Malhotra
mesh_terms: D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D003374:Coumarins / Q000138:chemical synthesis; D018360:Crystallography, X-Ray; D004963:Estrenes / Q000138:chemical synthesis; D005419:Flavonoids / Q000138:chemical synthesis; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D048289:Imidazolidines / Q000138:chemical synthesis* / Q000737:chemistry; D012834:Silver / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D003374:Coumarins; D004963:Estrenes; D005419:Flavonoids; D006027:Glycosides; D048289:Imidazolidines; D012834:Silver