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Sequential tritylation, benzoylation, and detritylation of methyl 3-deoxy-3-fluoro-β-
-galactopyranoside gave crystalline methyl 2,4-di-O-benzoyl-3-deoxy-3-fluoro-β-
-galactopyranoside (9), which was used as the initial nucleophile in the synthesis of the target oligosaccharide (16). Treatment of 9 with 2,3,4-tri-O-benzoyl-6-O-bromoacetyl-α-
-galactopyranosyl bromide gave the corresponding disaccharide derivative 13, having a selectively removable blocking group at O-6′. Debromoacetylation of 13 afforded the disaccharide nucleophile 14 which, when treated with 2,4,6-tri-O-benzoyl-3-deoxy-3-fluoro-α-
-galactopyranosyl bromide, gave the fully protected trisaccharide 15. Debenzoylation of 15 gave the title glycoside 16. Condensation reactions were performed with silver trifluoromethane-sulfonate as a promoter in the presence of sym-collidine under base-deficient conditions, and gave excellent yields of the desired β-(trans)-products. Analyses of the 1H- and 13C-n.m.r. spectra, as well as determination of the JCF and JHF coupling constants, were made by using various one- and two-dimensional n.m.r. techniques. 相似文献
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D. Flssner 《International Review of Hydrobiology》1993,78(1):20-20
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