Synthesis of a single repeat unit of type VIII group B Streptococcus capsular polysaccharide

Article abstract of DOI:10.1080/07328309708007324

We have synthesized a single repeat unit of type VIII Group B Streptococcus capsular polysaccharide, the structure of which is {L-Rhap(ss1-→4)-D-Glcp(ss1→4)[Neu5Ac(α2→3)]-D- Galp(ss1→4)}_n. The synthesis presented three significant synthetic challenges namely: the L-Rhap(ss1→4)-D-Glcp bond, the Neu5Ac(α2→3)-D-Galp bond and 3,4-D-Galp branching. The L-Rhap bond was constructed in 60% yield (α:ss 1:1.2) using 4-O-acetyl-2,3-di-O-benzoyl-α-L-rhamnopyranosyl bromide 6 as donor, silver silicate as promotor and 6-O-benzyl-2,3-di-O-benzoyl-1-thio-ss-D-glucopyranoside as acceptor to yield disaccharide 18. The Neu5Ac(α2→3) linkage was synthesized in 66% yield using methyl [phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-D-galacto- nonulopyranosid]onate as donor and triol 2-(trimethylsilyl) ethyl 6-O-benzyl-ss-D-galactopyranoside as acceptor to give disaccharide 21. The 3,4-D-Galp branching was achieved by regioselective glycosylation of disaccharide diol 21 by disaccharide 18 in 28% yield to give protected tetrasaccharide 22. Tetrasaccharide 22 was deprotected to give as its 2-(trimethylsilyl)ethyl glycoside the title compound 1a. In addition the 2-(trimethylsilyl)ethyl group was cleaved and the tetrasaccharide coupled by glycosylation (via tetrasaccharide trichloroacetimidate) to a linker suitable for conjugation.

Full text of DOI:10.1080/07328309708007324

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Journal of Carbohydrate Chemistry
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Synthesis of a Single Repeat Unit of Type
VIII Group B Streptococcus Capsular
Polysaccharide
Eva Eichler a , Harold J. Jennings a & Dennis M. Whitfield a
a National Research Council , 100 Sussex Drive, Ottawa, Ontario,
CANADA , K1A OR6
Published online: 20 Aug 2006.
To cite this article: Eva Eichler , Harold J. Jennings & Dennis M. Whitfield (1997) Synthesis of a Single
Repeat Unit of Type VIII Group B Streptococcus Capsular Polysaccharide , Journal of Carbohydrate
Chemistry, 16:4-5, 385-411, DOI: 10.1080/07328309708007324
To link to this article: http://dx.doi.org/10.1080/07328309708007324
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