Formaldehyde dialkylhydrazones smoothly add to sugaraldehydes without any need of promoter or catalyst. α-Hydroxy dialkylhydrazones, which are obtained in good yields and high stereoselectivities, have been successfully transformed in cyanohydrins by treatment with magnesium monoperoxyphtalate (MMPP) and in O-protected α-hydroxy aldehydes by ozonolysis or HCl mediated hydrolysis. No racemization was