Preparation of a Protected 3‑Deoxy‑d-manno-oct-2-ulosonate Glycal Donor for the Synthesis of β‑KDO-Containing Oligosaccharides

A practical method for the synthesis of KDO glycal donors was developed. The prepared KDO donors exhibited excellent disastereoselectivity of glycosylation in a CH₂Cl₂–CH₃CN solvent mixture, which was found to be associated with the isopropylidene protection at the C-4 and C-5 hydroxyls. The synthetic use of the KDO donor was demonstrated in the preparation of β-KDO-containing oligosaccharides.