Stereoselective Access to the β‐D‐N‐Acetylhexosaminyl‐(1→4)‐1‐deoxy‐D‐nojirimycin Disaccharide Series Avoiding the Glycosylation Reaction

The synthesis of β-D-GlcNAc-, β-D-GalNAc-, β-D-ManNAc-, and β-D-TalNAc-(14)-DNJ iminosugar disaccharides has been achieved, avoiding the glycosylation reaction, using a mixed tetracetonide of lactose [2,3:5,6:3′,4′-tri-O-isopropylidene-(6′-O-2-methoxy-2-methylethyl)-lactose dimethyl acetal] as starting material. The synthetic process is based on the transformation of the reducing unit of suitably protected β-D-hexosaminyl-(14)-aldehydo-D-glucose dimethyl acetal disaccharides into a deoxynojirimycin derivative. Key steps of the synthesis are: (a) the selective oxidation of the 5-position of the D-glucose unit, (b) release of the aldehydo function, (c) double reductive aminocyclisation of the 1,5-dicarbonyl disaccharide intermediate, and (d) complete deprotection.