Abstract
Abstract A simple, preparatively satisfactory 10-step sequence is described for converting lactose into a novel, suitably blocked lactosaminyl donor: N-Trichloroethoxycarbonyl-β-d-lactosaminyl fluoride (5). The key intermediate in this conversion is the particularly well-accessible oxime of lactosulosyl bromide (52% for the 6 steps from lactose), which on α-glycosidation with p-methoxybenzyl alcohol, oxime reduction, N-protection by Troc chloride, and the anomeric fluorination yields 5 (37% for the 4 steps). The utility of 5 as an effective donor was proved by the β-selective glycosylation of the primary 6-OH of 1,2 : 3,4-di-O-isopropylidene-α-d-galactopyranose (14) and the 3-OH of methyl 2,4,6-tri-O-benzyl-β-d-galactopyranoside (16), both affording the respective trisaccharides 15 and 18 in high yields. The latter, when subjected to N-deprotection, N-acetylation, and de-O-acylation gave, in 42% yield based on donor 5, β-d-Gal-(1→4)-β-d-GlcNAc-(1→3)-β-d-Gal-(1→Me, a core trisaccharide unit of immunologically important carbohydrate antigens.
Published Version
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