AbstractTreatment of keto‐sugarp‐nitrophenylhydrazones with lead tetraacetate led to the correspondinggem‐azo‐acetates. The reaction is highly stereoselective, only one of the two possible epimers at the new asymmetric carbon being formed in measurable quantity. Catalytic de‐acylation of thesegem‐azo‐acetates yielded, quantitatively, representatives of a new class of nitrogen‐containing sugars: thegem‐azo‐alcohols. When treated with potassiumt‐butylate, thegem‐azoacetates underwent a rearrangement with ring expansion le