Restriction of Conformation in Galabiosides Via an O6−O2‘-Methylene Bridge
摘要:
Treatment of 2-(trimethylsilyl)ethyl 2,3-di-O-acetyl-4-O-(3,4,6-tri-O-acetyl-alpha-D-galactopyranosyl)-beta-D-galactopyranoside (12) and 2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-beta-D-glucopyranoside (15) with the novel reagent combination formaldehyde diphenylmercaptal-N-iodosuccinimide-trifluoromethanesulfonic acid [(PhS)(2)CH2/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-alpha-D-galactopyranosyl-beta-D-galactopyranoside (1). The conformation of 1 was similar to that of the non-acetalated parent glycoside.
Treatment of 2-(trimethylsilyl)ethyl 2,3-di-O-acetyl-4-O-(3,4,6-tri-O-acetyl-alpha-D-galactopyranosyl)-beta-D-galactopyranoside (12) and 2-(trimethylsilyl)ethyl 2,3-di-O-benzyl-beta-D-glucopyranoside (15) with the novel reagent combination formaldehyde diphenylmercaptal-N-iodosuccinimide-trifluoromethanesulfonic acid [(PhS)(2)CH2/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-alpha-D-galactopyranosyl-beta-D-galactopyranoside (1). The conformation of 1 was similar to that of the non-acetalated parent glycoside.