Preparation of 2,6-anhydro-aldose acylhydrazones, -semicarbazones and -oximes from 2,6-anhydro-aldononitriles (glycosyl cyanides)

Reductive transformation of per-O-acylated 2,6-anhydro-aldononitriles (glycopyranosyl cyanides of the d-galacto, d-gluco, d-xylo, and d-arabino configuration) with Raney-nickel–NaH2PO2 in pyridine–AcOH–water solvent mixture in the presence of benzoylhydrazine, ethyl carbazate, and semicarbazide gave the corresponding anhydro-aldose benzoylhydrazones, -ethoxycarbonylhydrazones, and -semicarbazones, respectively. Acid catalyzed transimination of the semicarbazones with thiosemicarbazide, hydroxylamine, and O-benzylhydroxylamine, resulted in the formation of anhydro-aldose thiosemicarbazones, and E/Z mixtures of anhydro-aldose oximes, and O-benzyl-(anhydro-aldose)-oximes, respectively.