title: On the influence of the C2-O2 and C3-O3 bonds in 4,6-O-benzylidene-directed beta-mannopyranosylation and alpha-glucopyranosylation.
abstract: The synthesis of 4,6-O-benzylidene-protected 2-deoxyarabino-, 3-deoxyarabino-, and 3-deoxyribothioglycosides is described and their glycosylation reactions, with activation by either 1-benzenesulfinyl piperidine/trifluoromethansulfonic anhydride or diphenyl sulfoxide/trifluoromethanesulfonic anhydride, studied. In contrast to the corresponding 4,6-O-benzylidene-protected glucosyl and mannosyl donors, which are alpha- and beta-selective, respectively, poor diastereoselectivity is observed in all cases. The reasons for this poor selectivity are discussed in terms of the interaction between the C2-O2 and C3-O3 bonds in the glucosyl and mannosyl donors and of the influence of this interaction on the ease of formation of the intermediate glycosyl oxacarbenium ions.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA. dcrich@uic.edu
authors.forename: David
authors.initials: D
authors.lastname: Crich
authors.forename: Olga
authors.initials: O
authors.lastname: Vinogradova
mesh_terms: D001597:Benzylidene Compounds / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D006031:Glycosylation; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000737:chemistry*; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D001597:Benzylidene Compounds; D002244:Carbon; D005947:Glucose; D008358:Mannose; D010100:Oxygen