Application of the Dimethyl(phenyl)silyl Group as a Masked Form of the Hydroxy Group in the Synthesis of an L ‐ glycero ‐α‐ D ‐ manno ‐heptopyranoside‐Containing Trisaccharide from the Dephosphorylated Inner Core Region of Neisseria meningitidis

A favorable route to immunologically relevant oligosaccharides of type 1 makes use of the dimethyl(phenyl)silyl group (PhMe 2 Si). Addition of the Grignard reagent PhMe 2 SiCH 2 MgCl to a suitably protected D ‐mannodialdopyranose leads to chain lengthening at C‐6, i.e. formation of a heptopyranoside (Hepp) building block. The dimethyl(phenyl)silyl group functions thereby as equivalent of a protected hydroxy function. As precursor of 1 a completely protected triasaccharide was synthesized which additionally contained a spacer—for coupling with a polymeric support. Cleavage of the protecting groups affords the naturally occurring oligosaccharide 1 (with spacer).