Prearranged Glycosides, 4!. Synthesisvia Prearranged Glycosides of a Tetrasaccharide Fragment Related to the Capsular Polysaccharide ofStreptococcus pneumoniae Type 27

✍ Scribed by Schüle, Gunter ;Ziegler, Thomas

• Book ID: 102905146
• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 981 KB
• Volume: 1996
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199619961016

✦ Synopsis

Abstract

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(CH~2~)~5~NH~2~ (32), related to the repeating unit of the capsular polysaccharide of Streptoccus pneumoniae 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~)~5~NHZ (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.