Glycosylation of lactose: synthesis of branched oligosaccharides involved in the biosynthesis of glycolipids having blood-group I activity.

摘要: Abstract Methyl 4- O -(2- -benzoyl-4,6- -benzylidene-β- d -galactopyranos)-2,3,6-tri- -benzoyl-β- -glucopyranoside ( 2 ) was [re[ared in four steps from methyl β-lactoside. Crystalline a convenient substrate for the synthesis of branched oligosaccharides derived lactose. High-yield glycosylations were performed first at 3′-position and then, after removal benzylidene group, 6′-position, using trichloroacetimidates N -phthaloylamino sugars. 3,4,6-Tri- -acetyl-2-deoxy-2-phthalimido-β- -glucopyranosyl trichloroacetimidate thus used two consecutive glycosylations, also simultaneous disubstitution triol 9 , leading each sequence to tetrasaccharide, β- -Glc p -NAc-(1→3)-[β- NAc-(1→6)]-β- -Gal -(1→4-β- -GlcOME. Similar with 3,6-di- -acetyl-2-deoxy-2-phthalimido-4- -(2,3,4,6- tetra- -acetyl-β- -galactopyranosyl)-β- -g;ucopyranosyl afforded hexasaccharide -(1→4)-β- NAc-(1→3)-[β- NAc-(1→6)]- NAc-(1→6)-β- -GlcOMe, which corresponds human-milk oligasaccharide lacto- - neo hexaose has strong blood-group activity.