Stereoselective Access to the beta-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-(1->4)-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-(1->4)-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.