Restriction of Conformation in Galabiosides Via an O6−O2‘-Methylene Bridge†
journal contributionposted on 30.05.1997, 00:00 by Michael Wilstermann, Joakim Balogh, Göran Magnusson
Treatment of 2-(trimethylsilyl)ethyl 2,3-di-O-acetyl-4-O-(3,4,6-tri-O-acetyl-α-d-galactopyranosyl)-β-d-galactopyranoside (12) and 2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-β-d-glucopyranoside (15) with the novel reagent combination formaldehyde diphenylmercaptal−N-iodosuccinimide−trifluoromethanesulfonic acid [(PhS)2CH2/NIS/TfOH], gave the corresponding 6,2‘-O- and 4,6-O-methylidene acetals 13 and 16 in 52% and 53% yield, respectively. Deacetylation of 13 gave 2-(trimethylsilyl)ethyl 4-O-α-d-galactopyranosyl-β-d-galactopyranoside (1). The conformation of 1 was similar to that of the non-acetalated parent glycoside.