Synthetic studies on sialoglycoconjugates .88. Synthesis of ganglioside GM(3) and GM(4) analogs containing 2- or 3-branched fatty-alkyl residues in place of ceramide

Each of four ganglioside GM(4) and GM(3) analogues containing 2- or 3-branched fatty alkyl residues in place of ceramide have been synthesized. Coupling of O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonate)-(2-->3) -2,4,6-tri-O-benzoyl-alpha-D-galactopyranosyl trichloroacetimidate (13) or O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2- nonulopyranosylonate)-(2-->3)-O-(2,4-di-O-acetyl-6-O-benzoyl-beta-D-galactopyranosyl)-(1-->4)-3 -O-acetyl-2,4-di-O-benzoyl-alpha-D-glucopyranosyl trichloroacetimidate (14) with 2- or 3-branched fatty-alkyl-1-ols (9-12), prepared from the corresponding branched fatty acids by methyl esterification and reduction, using BF3 . OEt(2) gave the corresponding ganglioside analogues (15, 17, 19, 21, 23, 25, 27, 29) in good yields, which were coverted, via O-deacylation and de-esterification, into the tide compounds.