Synthese von β-l-rhamnosidisch verknüpften oligosacchariden des lipopolysaccharides aus Shigella flexneri sero-typ 6
1983; Elsevier BV; Volume: 120; Linguagem: Inglês
10.1016/0008-6215(83)88004-5
ISSN1873-426X
AutoresHans Paulsen, Wolfram Kutschker,
Tópico(s)Microbial Metabolites in Food Biotechnology
ResumoThe synthesis of the trisaccharide O-beta-L-rhamnopyranosyl-(1 leads to 4)-O-beta-L-rhamnopyranosyl-(1 leads to 2)-L-rhamnopyranose (14) and the tetrasaccharide O-2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1 leads to 2)-O-[beta-L-rhamnopyranosyl-(1 leads to 4)]-O-beta-L-rhamnopyranosyl-(1 leads to 2)-L-rhamnopyranose (21) is described. The latter structure has been proposed as the repeating unit of the O-specific side-chain of the lipopolysaccharide obtained from Shigella flexneri Serotype 6. The key-intermediate was 4-O-acetyl-2-O-allyl-3-O-benzyl-alpha-D-rhamnopyranosyl bromide, which was first linked to benzyl 3,4-di-O-benzyl-alpha-L-rhamnopyranoside, to give a blocked beta-linked disaccharide. This was O-deacetylated and coupled with 2,3,4-tri-O-benzyl-alpha-L-rhamnopyranosyl bromide at O-4' to afford benzyl O-(2,3,4-tri-O-benzyl-beta-L-rhamnopyranosyl)-(1 leads to 4)-O-(2-O-allyl-3-O-benzyl-beta-L-rhamnopyranosyl)-(1 leads to 2)-3,4-di-O-benzyl-alpha-L-rhamnopyranoside (11), which was deprotected to give 14. Deallylation of 11 and coupling with 6-O-acetyl-2-azido-3,4-di-O-benzyl-2-deoxy-alpha-D-galactopyranosyl bromide led to a protected tetrasaccharide from which 21 was obtained. The method of catalysis by silver silicate was employed to obtain the beta-glycosidic linkage of all monosaccharide units.
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