Prearranged glycosides, 4: Synthesis via prearranged glycosides of a tetrasaccharide fragment related to the capsular polysaccharide of Streptococcus pneumoniae type 27

Article abstract of DOI:10.1002/jlac.199619961016

The blockwise synthesis of the pyruvated tetrasaccharide 4,6-(S)-pyruvic-acetal-β-D-GlcNAc_p-(1→3)-α-D-Gal _p-(1→4)-β-L-Rha_p-(1→4)-β-D-Glc _p-O(CH₂)₅NH₂ (32), related to the repeating unit of the capsular polysaccharide of Streptococcus pneumonias type 27, by coupling of the suitably protected disaccharide blocks 4,6-(S)-pyruvic-acetal-β-D-GlcNAc_p-(1→3)-α-D-Gal _p-trichloroacetimidate (13) and β-L-Rha_p-(1→4)-β-D-Glc_p-O(CH ₂)₅NHZ (29β) is described. The latter disaccharide acceptor was prepared via prearranged glycosides by intramolecular glycosylation of a protected 5-aminopentyl β-D-glucopyranoside linked by a succinyl bridge at C-3 to C-2 of ethyl 1-thio-α-L-rhamnopyranoside. The dependence of the anomeric selectivity of the coupling on the nature of the protecting group at C-4 of the rhamnosyl moiety is studied. VCH Verlagsgesellschaft mbH, 1996.