title: Reactivity switching and selective activation of C-1 or C-3 in 2,3-unsaturated thioglycosides.
abstract: Reactivity switching and selective activation of C-1 or C-3 in 2,3-unsaturated thioglycosides, namely, 2,3-dideoxy-1-thio-D-hex-2-enopyranosides are reported. The reactivity switching allowed activation of either C-1 or C-3, with the use of either N-iodosuccinimide (NIS)/triflic acid (TfOH) or TfOH alone. C-1 glycosylation with alcohol acceptors occurred in the presence of NIS/TfOH, without the acceptors reacting at C-3. On the other hand, reaction of 2,3-unsaturated thioglycosides with alcohols mediated by triflic acid led to transposition of C-1 ethylthio-moiety to C-3 intramolecularly, to form 3-ethylthio-glycals. Resulting glycals underwent glycosylation with alcohols to afford 3-ethylthio-2-deoxy glycosides. However, when thiol was used as an acceptor, only a stereoselective addition at C-3 resulted, so as to form C-1, C-3 dithio-substituted 2-deoxypyranosides.
authors.affiliation: Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India.
authors.forename: Arunima
authors.initials: A
authors.lastname: Mukherjee
authors.forename: Narayanaswamy
authors.initials: N
authors.lastname: Jayaraman
mesh_terms: D000438:Alcohols / Q000737:chemistry; D001688:Biological Products / Q000138:chemical synthesis*; D002236:Carbohydrate Conformation; D003837:Deoxy Sugars / Q000737:chemistry; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008698:Mesylates / Q000737:chemistry; D013237:Stereoisomerism; D013388:Succinimides / Q000737:chemistry; D013865:Thioglycosides / Q000138:chemical synthesis*
chemical_list: D000438:Alcohols; D001688:Biological Products; D003837:Deoxy Sugars; D008698:Mesylates; D013388:Succinimides; D013865:Thioglycosides; C008155:N-iodosuccinimide; C012077:trifluoromethanesulfonic acid