A NOVEL, READILY ACCESSIBLE LACTOSAMINYL DONOR - OETHOXYCARBONYL-HEXA-O-BENZOYL-BETA-D-LACTOSAMINYL FLUORIDE

A simple, preparatively satisfactory 10-step sequence is described for converting lactose into a novel, suitably blocked lactosaminyl donor: N-Trichloroethoxycarbonyl-beta-D-lactosaminyl fluoride (5). The key i ntermediate in this conversion is the particularly well-accessible oxi me of lactosulosyl bromide (52% for the 6 steps from lactose), which o n alpha-glycosidation with p-methoxybenzyl alcohol, oxime reduction, N -protection by Tree chloride, and the anomeric fluorination yields 5 ( 37% for the 4 steps). The utility of 5 as an effective donor was prove d by the beta-selective glycosylation of the primary 6-OH of ,2:3,4-di -O-isopropylidene-alpha-D-galactopyranose (14) and the 3-OH of methyl 2,4,6-tri-O-benzyl-beta-D-galactopyranoside (16), both affording the r espective trisaccharides 15 and 18 in high yields. The latter, when su bjected to N-deprotection, N-acetylation, and de-O-acylation gave, in 42% yield based on donor 5, -(1-->4)-beta-D-GlcNAc-(1-->3)-beta-D-Gal- (1-->Me, a core trisaccharide unit of immunologically important carboh ydrate antigens.