An improved preparation of 3-deoxy-d-erythro-hexos-2-ulose via the bis(benzoylhydrazone) and some related constitutional studies

Sugar osazones and glycosuloses rapidly and quantitatively react with hydroxylamine to produce oximes that give trimethylsilyl derivatives suitable for g.l.c. and mass spectral analysis. The reaction of d-glucose with benzoylhydrazine to give the bishydrazone of 3-deoxy-d-erythro-hexos-2-ulose (1) [H. El Khadem et al., Carbohydr. Res., 22 (1973) 381-89] was re-investigated, together with the conversion of this compound to the hexosulose. Although by-products are produced in the reaction, including the bis(benzoylhydrazone) (osazone) of d-glucose, the major product is the monohydrate of the bis(benzoylhydrazone) of 1 (colorless). The anhydrous (yellow) form can be prepared from the monohydrate by crystallization from absolute ethanol and has quite different physical properties. Improvements of the original preparation are described that allow the preparation of the bishydrazone and its subsequent conversion to 1via transhydrazonation in 44% overall yield, and with no detectable contamination by d-glucose or d-glucosone. Evidence is presented that the previously reported cyclic form of the bis(benzoylhydrazone) of d-glucose is the bis(benzoylhydrazone) (monohydrate) of 1.