title: C-glycosylmethylene carbenes: synthesis of anhydro-aldose tosylhydrazones as precursors; generation and a new synthetic route to exo-glycals.
abstract: Acylated anhydro-aldononitriles (glycosyl cyanides) were transformed into anhydro-aldose tosylhydrazones by Raney-nickel reduction in the presence of tosylhydrazine in a one-pot reaction. The configuration of the C=N double bond in these hydrazones was E as proven by 15N-1H coupling constants as well as X-ray crystallography. Thermolysis in refluxing 1,4-dioxane of the sodium salts of the tosylhydrazones obtained by sodium hydride (generally 10 eq.) resulted in the formation of anhydro-1-deoxy-ald-1-enitols (exo-glycals). "Dimeric" N-glycosylmethyl anhydro-aldose tosylhydrazones could also be isolated when the use of less base caused incomplete deprotonation of the starting compounds. This two-step procedure constitutes a novel, reasonably short synthetic pathway to acylated exo-glycals from the readily available glycosyl cyanides.
authors.affiliation: Department of Organic Chemistry, University of Debrecen, Debrecen, Hungary.
authors.forename: Marietta
authors.initials: M
authors.lastname: Tóth
authors.forename: Katalin E
authors.initials: KE
authors.lastname: Kövér
authors.forename: Attila
authors.initials: A
authors.lastname: Bényei
authors.forename: László
authors.initials: L
authors.lastname: Somsák
mesh_terms: D002244:Carbon / Q000737:chemistry; D003486:Cyanides / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry; D006027:Glycosides / Q000737:chemistry*; D006358:Hot Temperature; D006834:Hydrazines / Q000737:chemistry; D006838:Hydrocarbons; D006859:Hydrogen / Q000737:chemistry; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry; D012964:Sodium / Q000737:chemistry
chemical_list: D003486:Cyanides; D004146:Dioxanes; D006027:Glycosides; D006834:Hydrazines; D006838:Hydrocarbons; C030011:carbene; D002244:Carbon; D006859:Hydrogen; D012964:Sodium; C025223:1,4-dioxane; D009584:Nitrogen; D008697:Methane