Synthetic Studies on Sialoglycoconjugates 89: Synthesis of Ganglioside GM3and KDN-GM3Containing Different Carbon-Chain Length Fatty Acyl Groups at the Ceramide Residue

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Abstract
Ganglioside GM3 and KDN-ganglioside GM3, containing hexanoyl, decanoyl, and hexadecanoyl groups at the ceramide moiety have been synthesized. Selective reduction of the azido group in O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-O-(2,4-di-O-acetyl-6-O-benzoyl-β-D-galactopyranosyl)-(1→4)-O-(3-O-acetyl-2,6-di-O-benzoyl-β-D-glucopyranosyl)-(1→1)-(2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (1) and O-(methyl 4,5,7,8,9-penta-O-acetyl-3-deoxy-D-glycero-α-D-galacto-2-nonulopyranosylonate)-(2→3)-O-(2,4-di-O-acetyl-6-O-benzoyl-β-D-galactopyranosyl)-(1→4)-O-(3-O-acetyl-2,6-di-O-benzoyl-β-D-glucopyranosyl)-(1→1)-(2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (2), coupling with hexanoic, decanoic, and hexadecanoic acids, O-deacylation, and de-esterification gave the title gangliosides GM3 (11→13) and KDN-GM3 (14→16) in good yields. On the other hand, O-deacylation of 1 and subsequent de-esterification gave 2-azido-sphingosine containing-GM3 analogue 17, which was converted into lyso-GM3, in which no fatty acyl group was substituted at the sphingosine residue, by selective reduction of the azido group.