Linear synthesis of the methyl glycosides of tri-, tetra-, and pentasaccharide fragments of the Shigella flexneri serotype 5a o-antigen1

Article abstract of DOI:10.1080/07328300008544096

The stepwise synthesis of methyl α-D-glucopyranosyl-(1-→3)-α-L-rhamnopyranosyl-(1-→3)-α-L-rhamnopyranoside (EBC-OMe, 1), methyl α-L-rhamnopyranosyl-(1 →2)-[α-D-glucopyranosyl-(1-→ 3)]-α-L-rhamnopyranosyl-(1-→ 3)-α-L-rhamnopyranoside (A(E)BC-OMe, 2), and methyl 2-acetamido-2-deoxy-β-D-glucopyranosyl-(1-→2)-α-L-rhamnopyranosy l-(1-→ 2)-[α-D-glucopyranosyl-(1- 3)]-α-L-rhamnopyranosyl-(1-→3)-α-L-rhamnopyranoside (DA(E)BC-OMe, 3) is described. Compounds 1, 2 and 3 constitute the methyl glycosides of fragments of the O-specific polysaccharide of Shigella flexneri serotype 5a. Methyl 2,4-di-O-benzoyl-α-L-rhamnopyranosyl-(1-→3)-2,4-di-O-benzoyl-α- L-rhamnopyranoside was an appropriate BC precursor for the synthesis of 1. For the synthesis of the branched targets 2 and 3, a benzyl group was best suited at position 2 of rhamnose C. Thus, methyl 4-O-benzyl-α-L-rhamnopyranosyl-(1-→3)-2,4-di-O-benzyl-α-L-rhamn opyranoside was the key intermediate to the BC portion. In all cases, 2,3,4,6-tetraO-benzyl-α-D-glucopyranosyl fluoride was a convenient E precursor, when used in combination with titanium tetrafluoride. All along, attention was paid to steric hindrance as a factor of major impact on the condensation steps outcome. Therefore, based on previous experience, 2-O-acetyl-3,4-di-O-allyl-α-L-rhamnopyranosyl trichloroacetimidate and 3,4,6-tri-O-acetyl-2-deoxy-2-trichloroacetamido-α-D-glucopyranosyl trichloroacetimidate were used as donors. Both suited all requirements when used as key precursors for residues A and D in the synthesis of 3, respectively.

Full text of DOI:10.1080/07328300008544096

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Linear Synthesis of The Methyl
Glycosides of Tri-, Tetra-, and
Pentasaccharide Fragments of The
Shigella Flexneri Serotype 5A O-
Antigen
Laurence A. Mulard & Joël Ughetto-Monfrin
a Unité de Chimie Organique, BGM, Institut Pasteur , 28 rue
du Dr. Roux, 75724 Paris Cedex 15, France E-mail:
Published online: 07 Mar 2008.
To cite this article: Laurence A. Mulard & Joël Ughetto-Monfrin (2000) Linear Synthesis
of The Methyl Glycosides of Tri-, Tetra-, and Pentasaccharide Fragments of The Shigella
Flexneri Serotype 5A O-Antigen, Journal of Carbohydrate Chemistry, 19:4-5, 503-526, DOI:
10.1080/07328300008544096
To link to this article: http://dx.doi.org/10.1080/07328300008544096
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