In bacteria with truncated lipopolysaccharide structures, i.e., lacking the O-antigen polysaccharide part, core structures are exposed to the immune system upon infection and thus their use as carbohydrate surface antigens in glycoconjugate vaccines can be considered and investigated. One such suggested structure from Haemophilus influenzae LPS is the phosphorylated pentasaccharide 6-PEtN-alpha -D-GalpNAc-(1->6)-beta -D-Galp-(1->4)-beta -D-GlcpNAc-(1->3)-beta -D-Galp-(1->4)-beta -D-Glcp. Starting from a spacer-contg. lactose deriv. a suitably protected lacto-N-neotetraose tetrasaccharide structure was constructed through sub-sequential coupling with two thioglycoside donors, a glucosamine residue followed by a galactose deriv., using NIS/AgOTf as promoter. Removal of a silyl protecting group at the primary position of the non-reducing end residue afforded an acceptor to which the terminal alpha -galactosamine moiety was introduced using a 2-azido bromo sugar and halide assisted coupling conditions. Global deprotection afforded the non-phosphorylated target pentasaccharide, whereas removal of a silyl group from the primary position of the non-reducing end residue produced a free hydroxy group which was phosphorylated using H-phosphonate chem. to yield the phosphoethanolamine-contg. protected pentasaccharide. Partial deprotection afforded the phosphorylated target pentasaccharide with a free spacer amino group but with a protected phosphoethanolamino group. Conjugation of the spacer amino group to biotin or di-Me squarate followed by deprotection of the phosphoethanolamino group and in the case of the squarate deriv., further reaction with a protein then afforded the title conjugates. Through the spacer, biotin and protein conjugates of the title compd. have been constructed to allow further use in biol. expts. [on SciFinder (R)]In bacteria with truncated lipopolysaccharide structures, i.e., lacking the O-antigen polysaccharide part, core structures are exposed to the immune system upon infection and thus their use as carbohydrate surface antigens in glycoconjugate vaccines can be considered and investigated. One such suggested structure from Haemophilus influenzae LPS is the phosphorylated pentasaccharide 6-PEtN-alpha -D-GalpNAc-(1->6)-beta -D-Galp-(1->4)-beta -D-GlcpNAc-(1->3)-beta -D-Galp-(1->4)-beta -D-Glcp. Starting from a spacer-contg. lactose deriv. a suitably protected lacto-N-neotetraose tetrasaccharide structure was constructed through sub-sequential coupling with two thioglycoside donors, a glucosamine residue followed by a galactose deriv., using NIS/AgOTf as promoter. Removal of a silyl protecting group at the primary position of the non-reducing end residue afforded an acceptor to which the terminal alpha -galactosamine moiety was introduced using a 2-azido bromo sugar and halide assisted coupling conditions. Global deprotection afforded the non-phosphorylated target pentasaccharide, whereas removal of a silyl group from the primary position of the non-reducing end residue produced a free hydroxy group which was phosphorylated using H-phosphonate chem. to yield the phosphoethanolamine-contg. protected pentasaccharide. Partial deprotection afforded the phosphorylated target pentasaccharide with a free spacer amino group but with a protected phosphoethanolamino group. Conjugation of the spacer amino group to biotin or di-Me squarate followed by deprotection of the phosphoethanolamino group and in the case of the squarate deriv., further reaction with a protein then afforded the title conjugates. Through the spacer, biotin and protein conjugates of the title compd. have been constructed to allow further use in biol. expts. [on SciFinder (R)]