Synthesis of a common tetrasaccharide motif of Haemophilus influenzae LPS inner core structures

Abstract

A conserved tetrasaccharide structure, L-glycero-α-D-manno-heptopyranosyl-(1→2)-(6-O-aminoethylphosphono-L-glycero-α-D-manno-heptopyranosyl)-(1→3)-[β-D-glucopyranosyl-(1→4)]-L-glycero-α-D-manno-heptopyranose, from the LPS inner core of Haemophilus influenzae has been synthesised as its ethylamino glycosides to allow later conjugations. Starting from a previously synthesised suitably protected trisaccharide intermediate, the third heptose and subsequently the spacer were introduced using thioglycoside donor chemistry. The phosphoethanolamine was formed employing a Boc-protected phosphoamidite. Final deprotection and conjugation to biotin gave conjugates that will be used to study the specificity of MAbs raised against native LPS structures.