rearrangement of N-benzylhydrazine to sugar δ-enlactone with erythroconfiguration 1 and 2 affords mixtures of respective ribo and arabino isomers with the former one prevailing. In the case of the threo lactone 3 two regioisomers with xylo configuration are produced, whereas in the case of 4 only one isomer with the erythroconfiguration is formed. The stereochemical course of these rections was explained