title: Glycosidation-anomerisation reactions of 6,1-anhydroglucopyranuronic acid and anomerisation of beta-D-glucopyranosiduronic acids promoted by SnCl(4).
abstract: The reaction of silylated nucleophiles with 6,1-anhydroglucopyranuronic acid (glucuronic acid 6,1-lactones) catalysed by tin(IV) chloride provides 1,2-trans or 1,2-cis (deoxy)glycosides in a manner dependent on the donor structure. The alpha-glycoside was obtained for reactions of the donor with the 2-acyl group and 2-deoxydonors, whereas the 2-deoxy-2-iodo donor gave the beta-glycoside. Experimental evidence shows that when 1,2-cis-glycoside formation occurs, the anomerisation of initially formed 1,2-trans-glycosides catalysed by SnCl(4) is possible. The anomerisation of beta-D-glucopyranosiduronic acids was found to be faster, in some cases, than anomerisation of related beta-D-glucopyranosiduronic acid esters and beta-D-glucopyranoside derivatives and the rates are dependent on the structure of the aglycon. Moreover, the rates of anomerisation of beta-D-glucopyranuronic acid derivatives can be qualitatively correlated with rates of hydrolysis of beta-D-glucopyranosiduronic acids. Mechanistic possibilities for the reactions are considered.
authors.affiliation: Centre for Synthesis and Chemical Biology, UCD School of Chemistry and Chemical Biology, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin 4, Ireland.
authors.forename: Colin
authors.initials: C
authors.lastname: O'Brien
authors.forename: Monika
authors.initials: M
authors.lastname: Poláková
authors.forename: Nigel
authors.initials: N
authors.lastname: Pitt
authors.forename: Manuela
authors.initials: M
authors.lastname: Tosin
authors.forename: Paul V
authors.initials: PV
authors.lastname: Murphy
mesh_terms: D006031:Glycosylation; D015394:Molecular Structure; D009005:Monosaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013997:Time Factors; D017971:Tin Compounds / Q000737:chemistry*; D014574:Uronic Acids / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C518151:6,1-anhydroglucopyranuronic acid; D009005:Monosaccharides; D017971:Tin Compounds; D014574:Uronic Acids; C041694:stannic chloride