Chemical transformation of a 1-deoxynojirimycin derivative into 1-deoxymannojirimycin and 1-deoxygalactostatin

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 derivative 5 in good yield. This was efficiently converted into 1-deoxymannojirimycin (2) via regioselective p-toluenesulfonylation followed by an inversion reaction at the C-2 position. On the other hand, the monochloromethylsulfonate 10 obtained from 4 underwent configurational change at the C-4 position by the action of sodium benzoate. The resulting benzoate 11 was deprotected to afford 1-deoxygalactostatin (3).