Abstract The reactions of d-mannose arylhydrazones with dimethyl acetylenedicarboxylate under acidic conditions afforded the respective pentahydroxypentylpyrazoles. With the phenyl-and p-tolyl-hydrazones, the respective enehydrazones were also obtained. The new pyrazole derivatives gave penta-acetates and oxidation with sodium periodate gave pyrazole-3-carbaldehydes. The 1 Hn. mr coupling constants of the penta-acetates ...