Synthesis of a hexasaccharide corresponding to part of the heptose-hexose region of the Salmonella Ra core, and a penta- and a tetra-saccharide that compose parts of this structure
✍ Scribed by Stefan Oscarson; Helena Ritzén
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 753 KB
- Volume
- 254
- Category
- Article
- ISSN
- 0008-6215
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✦ Synopsis
The synthesis of the hexasaccharide 2-(4-trifhioroacetamidophenyl)ethyl O-o-o-galactopyranosyl-(1 + 3)-[O_cu-D-galactopyranosyl-(I + 6)]-O-a-o-ghtcopyranosyl_(l --) 3)-[O-L-g&cero-o-D-r?zanno-heptopyranosyl-(1 + 7)]-0-L-g/yceroa-D-manno-heptopyranosyl-(1 + 3)-r_-glycero-a-o-manno-heptopyrauoside, corresponding to the heptose and part of the hexose region in the Salmonella Ra core, is described. Syntheses of the pentasaccharide 2_(4-trifluoroacetamidophenyl)ethyl O-a-o-galactopyranosyl-(1 + 3)-O-o-o-glucopyranosyl-(1 + 3)[0-L-glyceroa-~~mznno-heptopyranosyl-(I -+ 7)]-0-L-glyceroa-D-manno-heptopyranosyL(1 + 3)-L-glycero-a-o-manno-heptopyranoside and the tetrasaccharide 2-(4-trifluoroacetamidophenyljethyl 0-cu-o-glucopyranosyL(1 + 3)-[O-L-glycero-a-o-manno-heptopyranosyl-(I + 7)]-0-r_-glyceroa-o-manno-heptopyranosyl-(I + 3)r_-gbcero_cY-o-manno-heptopyranoside are also described. Coupling of methyl 2,3,4,6-tetra-O-benxykl-thio-p-o-glucopyranoside and methyl 2-O-benzyl-4,6-O-benzylidene-3-0-(2,3,4,6-tetra-O-be~l~-o-galactop~~osyl)-1-thio-~-o-glucopyranoside
to a triheptoside derivative with a free HO-3', using dimethyl(methylthio)sulfonium triflate and N-iodosuccinimide-silver triflate as promoters, gave the protected tetra-and penta-saccharide, respectively. Removal of the benxylidene group from the pentasaccharide followed by a regio-and stereo-selective coupling using halide-assisted conditions and L&3,4,6-tetra-0-benzykr-o-galactopyranosyl bromide as donor gave the protected hexasaccharide. Deprotection then gave the target structures.