The usefulness of N,N -diacetylchitobiose (1) as a starting material for syntheses of biologically active compounds was shown by converting allyl chitobioside 5 intoO -(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→4)-2-acetamido-1,2,5-trideoxy -1,5-imino-D-glucitol (2), which would be a potential glycosidase inhibitor. The conversion includes a discriminative modification of two amino groups existing in the disaccharide intermediate 8, regioselective introduction of an azide group and construction of a piperidine ring utilizing an intramolecular aminocyclization.