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  • Title: Synthesis of an S-(alpha-sialosyl)-(2----9)-O-(alpha-sialosyl)-(2----3')-beta-lactos ylceramide.
    Author: Hasegawa A, Ogawa H, Ishida H, Kiso M.
    Journal: Carbohydr Res; 1992 Feb 07; 224():175-84. PubMed ID: 1591759.
    Abstract:
    A ganglioside GD3 analog has been synthesized having an N-acetylneuraminic acid (Neu5Ac) residue alpha-thioglycosidically linked to C-9 of the Neu5Ac residue in the ganglioside GM3 structure. Glycosylation of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,6-di-O-benzoyl-beta-D -glucopyranoside with methyl (methyl 5-acetamido-4,7,8-tri-O-acetyl-9-bromo-3,5,9-trideoxy-D-glycero-alpha-D- galacto-2-nonulopyranosid)onate, which was prepared from methyl (methyl 5-acetamido-3,5-dideoxy-D-glycero-alpha-D-galacto-2- nonulopyranosid)onate by 8,9-O-isopropylidenation, O-acetylation, hydrolysis of the isopropylidene group, selective bromination, and O-acetylation, using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter, gave the alpha-sialosyl-(2----3')-lactoside 8. Coupling of the O-acetyl derivative of 8 with the sodium salt of methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha-D- galacto-2-nonulopyranosonate gave an alpha-thioglycosidically linked tetrasaccharide. This was converted, via selective removal of the 2-(trimethylsilyl)ethyl group, trichloroacetimidation, and glycosidation with (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol into a ganglioside precursor. Finally the precursor on selective reduction of the azide group, coupling with octadecanoic acid, O-deacylation, and de-esterification gave the analog, S-(N-acetyl-alpha-neuraminosyl)-(2----9)-O-(N-acetyl-9-thio-alpha- neuraminosyl)-(2----3')-beta-lactosylceramide.
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