Treatment of 2,3-di-O-benzyl-N-benzyloxycarbonyl-6-O-t-butyldiphenylsilyl-1,5-dideoxy-1,5-imino-D-glucitol (4) with sodium hydride resulted in an intramolecular cyclization concomitant with silyl migration, giving the carbamate derivative5in good yield. This was efficiently converted into 1-deoxymannojirimycin (2)viaregioselectivep-toluenesulfonylation followed by an inversion reaction at the C-2 position. On the other hand, the monochloromethylsulfonate10obtained from4underwent configurational change at the C-4 position by the action of sodium benzoate. The resulting benzoate11was deprotected to afford 1-deoxygalactostatin (3).