SYNTHESIS OF TRISACCHARIDE AND TETRASACCHARIDE FRAGMENTS OF THE SHIGELLA-DYSENTERIAE TYPE-1 O-ANTIGEN DEOXYGENATED AND FLUORINATED AT POSITION-3 OF THE METHYL ALPHA-D-GALACTOPYRANOSIDE TERMINUS
La. Mulard et Cpj. Glaudemans, SYNTHESIS OF TRISACCHARIDE AND TETRASACCHARIDE FRAGMENTS OF THE SHIGELLA-DYSENTERIAE TYPE-1 O-ANTIGEN DEOXYGENATED AND FLUORINATED AT POSITION-3 OF THE METHYL ALPHA-D-GALACTOPYRANOSIDE TERMINUS, Carbohydrate research, 311(3), 1998, pp. 121-133
The blockwise synthesis of methyl alpha tri- and tetrasaccharide analo
gs of the biochemical repeating unit of the Shigella dysenteriae type
1 O-polysaccharide is described. Modifications include deoxygenation a
nd deoxyfluorination at position 3 of the galactopyranoside residue. M
ethyl -O-benzylidene-3-deoxy-alpha-D-xylo-hexopyranoside (8) and methy
l ylidene-3-deoxy-3-fluoro-alpha-D-galactopyranoside (9) were condense
d with )-(1-->3)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl chloride to
give, after deprotection, the target trisaccharide methyl anosyl-(1-->
2)-3-deoxy-alpha-D-xylo-hexopyranoside and the corresponding fluorinat
ed oligosaccharide. For the tetrasaccharide synthesis, the glycosyl ac
cepters 8 and 9 were condensed with the temporarily protected )-(1-->3
)-2,4-di-O-benzoyl-alpha-L-rhamnopyranosyl chloride. Removal of the ch
loroacetyl group was followed by condensation of the resulting selecti
vely deblocked trisaccharides with ri-O-acetyl-2-azido-2-deoxy-alpha-D
-glucopyranosyl chloride. Reduction and deprotection then gave the fre
e methyl 2-acetamido-2-deoxy-alpha-D-glucopyranosyl-(1-->3) anosyl-(1-
->2)-3-deoxy-alpha-D-xylo-hexopyranoside and the fluorinated analog. (
C) 1998 Elsevier Science Ltd. All rights reserved.